TY  - JOUR
A1  - Schulze, Patricia S. C.
A1  - Bett, Alexander J.
A1  - Bivour, Martin
A1  - Caprioglio, Pietro
A1  - Gerspacher, Fabian M.
A1  - Kabaklı, Özde Ş.
A1  - Richter, Armin
A1  - Stolterfoht, Martin
A1  - Zhang, Qinxin
A1  - Neher, Dieter
A1  - Hermle, Martin
A1  - Hillebrecht, Harald
A1  - Glunz, Stefan W.
A1  - Goldschmidt, Jan Christoph
T1  - 25.1% high-efficiency monolithic perovskite silicon tandem solar cell with a high bandgap perovskite absorber
JF  - Solar RRL
N2  - Monolithic perovskite silicon tandem solar cells can overcome the theoretical efficiency limit of silicon solar cells. This requires an optimum bandgap, high quantum efficiency, and high stability of the perovskite. Herein, a silicon heterojunction bottom cell is combined with a perovskite top cell, with an optimum bandgap of 1.68 eV in planar p-i-n tandem configuration. A methylammonium-free FA(0.75)Cs(0.25)Pb(I0.8Br0.2)(3) perovskite with high Cs content is investigated for improved stability. A 10% molarity increase to 1.1 m of the perovskite precursor solution results in approximate to 75 nm thicker absorber layers and 0.7 mA cm(-2) higher short-circuit current density. With the optimized absorber, tandem devices reach a high fill factor of 80% and up to 25.1% certified efficiency. The unencapsulated tandem device shows an efficiency improvement of 2.3% (absolute) over 5 months, showing the robustness of the absorber against degradation. Moreover, a photoluminescence quantum yield analysis reveals that with adapted charge transport materials and surface passivation, along with improved antireflection measures, the high bandgap perovskite absorber has the potential for 30% tandem efficiency in the near future.
KW  - heterojunction silicon solar cells
KW  - interfaces
KW  - perovskite solar cells
KW  - tandem solar cells
KW  - thin films
Y1  - 2020
VL  - 4
IS  - 7
PB  - John Wiley & Sons, Inc.
CY  - New Jersey
ER  - 
TY  - JOUR
A1  - Leto, Paolo
A1  - Trigilio, C.
A1  - Oskinova, Lida
A1  - Ignace, R.
A1  - Buemi, C. S.
A1  - Umana, G.
A1  - Ingallinera, A.
A1  - Leone, Francesco
A1  - Phillips, N. M.
A1  - Agliozzo, Claudia
A1  - Todt, Helge Tobias
A1  - Cerrigone, L.
T1  - A combined multiwavelength VLA/ALMA/Chandra study unveils the complex magnetosphere of the B-type star HR5907
JF  - Monthly notices of the Royal Astronomical Society
N2  - We present new radio/millimeter measurements of the hot magnetic star HR5907 obtained with the VLA and ALMA interferometers. We find that HR5907 is the most radio luminous early type star in the cm-mm band among those presently known. Its multi-wavelength radio light curves are strongly variable with an amplitude that increases with radio frequency. The radio emission can be explained by the populations of the non-thermal electrons accelerated in the current sheets on the outer border of the magnetosphere of this fast-rotating magnetic star. We classify HR5907 as another member of the growing class of strongly magnetic fast-rotating hot stars where the gyro-synchrotron emission mechanism efficiently operates in their magnetospheres. The new radio observations of HR5907 are combined with archival X-ray data to study the physical condition of its magnetosphere. The X-ray spectra of HR5907 show tentative evidence for the presence of non-thermal spectral component. We suggest that non-thermal X-rays originate a stellar X-ray aurora due to streams of non-thermal electrons impacting on the stellar surface. Taking advantage of the relation between the spectral indices of the X-ray power-law spectrum and the non-thermal electron energy distributions, we perform 3-D modelling of the radio emission for HR5907. The wavelength-dependent radio light curves probe magnetospheric layers at different heights above the stellar surface. A detailed comparison between simulated and observed radio light curves leads us to conclude that the stellar magnetic field of HR 5907 is likely non-dipolar, providing further indirect evidence of the complex magnetic field topology of HR5907.
KW  - stars: chemically peculiar
KW  - stars: early-type
KW  - stars: individual: HR 5907
KW  - stars: magnetic field
KW  - radio continuum: stars
KW  - X-rays: stars
Y1  - 2018
U6  - https://doi.org/10.1093/mnras/sty244
SN  - 0035-8711
SN  - 1365-2966
VL  - 476
IS  - 1
SP  - 562
EP  - 579
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Agarwal, Ankit
A1  - Guntu, Ravikumar
A1  - Banerjee, Abhirup
A1  - Gadhawe, Mayuri Ashokrao
A1  - Marwan, Norbert
T1  - A complex network approach to study the extreme precipitation patterns in a river basin
JF  - Chaos : an interdisciplinary journal of nonlinear science
N2  - The quantification of spatial propagation of extreme precipitation events is vital in water resources planning and disaster mitigation. However, quantifying these extreme events has always been challenging as many traditional methods are insufficient to capture the nonlinear interrelationships between extreme event time series. Therefore, it is crucial to develop suitable methods for analyzing the dynamics of extreme events over a river basin with a diverse climate and complicated topography. Over the last decade, complex network analysis emerged as a powerful tool to study the intricate spatiotemporal relationship between many variables in a compact way. In this study, we employ two nonlinear concepts of event synchronization and edit distance to investigate the extreme precipitation pattern in the Ganga river basin. We use the network degree to understand the spatial synchronization pattern of extreme rainfall and identify essential sites in the river basin with respect to potential prediction skills. The study also attempts to quantify the influence of precipitation seasonality and topography on extreme events. The findings of the study reveal that (1) the network degree is decreased in the southwest to northwest direction, (2) the timing of 50th percentile precipitation within a year influences the spatial distribution of degree, (3) the timing is inversely related to elevation, and (4) the lower elevation greatly influences connectivity of the sites. The study highlights that edit distance could be a promising alternative to analyze event-like data by incorporating event time and amplitude and constructing complex networks of climate extremes.
Y1  - 2022
U6  - https://doi.org/10.1063/5.0072520
SN  - 1054-1500
SN  - 1089-7682
VL  - 32
IS  - 1
PB  - American Institute of Physics
CY  - Woodbury, NY
ER  - 
TY  - JOUR
A1  - Fischer, Eric W.
A1  - Werther, Michael
A1  - Bouakline, Foudhil
A1  - Saalfrank, Peter
T1  - A hierarchical effective mode approach to phonon-driven multilevel vibrational relaxation dynamics at surfaces
JF  - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistry
N2  - We discuss an efficient Hierarchical Effective Mode (HEM) representation of a high-dimensional harmonic oscillator bath, which describes phonon-driven vibrational relaxation of an adsorbate-surface system, namely, deuterium adsorbed on Si(100). Starting from the original Hamiltonian of the adsorbate-surface system, the HEM representation is constructed via iterative orthogonal transformations, which are efficiently implemented with Householder matrices. The detailed description of the HEM representation and its construction are given in the second quantization representation. The hierarchical nature of this representation allows access to the exact quantum dynamics of the adsorbate-surface system over finite time intervals, controllable via the truncation order of the hierarchy. To study the convergence properties of the effective mode representation, we solve the time-dependent Schrodinger equation of the truncated system-bath HEM Hamiltonian, with the help of the multilayer extension of the Multiconfigurational Time-Dependent Hartree (ML-MCTDH) method. The results of the HEM representation are compared with those obtained with a quantum-mechanical tier-model. The convergence of the HEM representation with respect to the truncation order of the hierarchy is discussed for different initial conditions of the adsorbate-surface system. The combination of the HEM representation with the ML-MCTDH method provides information on the time evolution of the system (adsorbate) and multiple effective modes of the bath (surface). This permits insight into mechanisms of vibration-phonon coupling of the adsorbate-surface system, as well as inter-mode couplings of the effective bath.
Y1  - 2020
U6  - https://doi.org/10.1063/5.0017716
SN  - 0021-9606
SN  - 1089-7690
VL  - 153
IS  - 6
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - JOUR
A1  - Abeysekara, A. U.
A1  - Archambault, S.
A1  - Archer, A.
A1  - Benbow, Wystan
A1  - Bird, Ralph
A1  - Buchovecky, M.
A1  - Buckley, J. H.
A1  - Bugaev, V.
A1  - Byrum, K.
A1  - Cerruti, M.
A1  - Chen, X.
A1  - Ciupik, L.
A1  - Cui, W.
A1  - Dickinson, H. J.
A1  - Eisch, J. D.
A1  - Errando, M.
A1  - Falcone, A.
A1  - Feng, Q.
A1  - Finley, J. P.
A1  - Fleischhack, H.
A1  - Fortson, L.
A1  - Furniss, A.
A1  - Gillanders, G. H.
A1  - Griffin, S.
A1  - Grube, J.
A1  - Hutten, M.
A1  - Hakansson, N.
A1  - Hanna, D.
A1  - Holder, J.
A1  - Humensky, T. B.
A1  - Johnson, C. A.
A1  - Kaaret, P.
A1  - Kar, P.
A1  - Kertzman, M.
A1  - Kieda, D.
A1  - Krause, M.
A1  - Krennrich, F.
A1  - Kumar, S.
A1  - Lang, M. J.
A1  - Maier, G.
A1  - McArthur, S.
A1  - McCann, A.
A1  - Meagher, K.
A1  - Moriarty, P.
A1  - Mukherjee, R.
A1  - Nguyen, T.
A1  - Nieto, D.
A1  - Ong, R. A.
A1  - Otte, A. N.
A1  - Park, N.
A1  - Pelassa, V.
A1  - Pohl, Martin
A1  - Popkow, A.
A1  - Pueschel, Elisa
A1  - Quinn, J.
A1  - Ragan, K.
A1  - Reynolds, P. T.
A1  - Richards, G. T.
A1  - Roache, E.
A1  - Rulten, C.
A1  - Santander, M.
A1  - Sembroski, G. H.
A1  - Shahinyan, K.
A1  - Staszak, D.
A1  - Telezhinsky, Igor O.
A1  - Tucci, J. V.
A1  - Tyler, J.
A1  - Wakely, S. P.
A1  - Weiner, O. M.
A1  - Weinstein, A.
A1  - Wilhelm, Alina
A1  - Williams, D. A.
A1  - Fegan, S.
A1  - Giebels, B.
A1  - Horan, D.
A1  - Berdyugin, A.
A1  - Kuan, J.
A1  - Lindfors, E.
A1  - Nilsson, K.
A1  - Oksanen, A.
A1  - Prokoph, H.
A1  - Reinthal, R.
A1  - Takalo, L.
A1  - Zefi, F.
T1  - A Luminous and Isolated Gamma-Ray Flare from the Blazar B2 1215+30
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - B2 1215+30 is a BL-Lac-type blazar that was first detected at TeV energies by the MAGIC atmospheric Cherenkov telescopes and subsequently confirmed by the Very Energetic Radiation Imaging Telescope Array System (VERITAS) observatory with data collected between 2009 and 2012. In 2014 February 08, VERITAS detected a large-amplitude flare from B2. 1215+30 during routine monitoring observations of the blazar 1ES. 1218+304, located in the same field of view. The TeV flux reached 2.4 times the Crab Nebula flux with a variability timescale of <3.6 hr. Multiwavelength observations with Fermi-LAT, Swift, and the Tuorla Observatory revealed a correlated high GeV flux state and no significant optical counterpart to the flare, with a spectral energy distribution where the gamma-ray luminosity exceeds the synchrotron luminosity. When interpreted in the framework of a onezone leptonic model, the observed emission implies a high degree of beaming, with Doppler factor delta > 10, and an electron population with spectral index p < 2.3.
KW  - BL Lacertae objects: individual (B2 1215+30, VER J1217+301)
KW  - galaxies: active
KW  - galaxies: jets
KW  - galaxies: nuclei
KW  - gamma rays: galaxies
Y1  - 2017
U6  - https://doi.org/10.3847/1538-4357/836/2/205
SN  - 0004-637X
SN  - 1538-4357
VL  - 836
IS  - 2
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Hassanin, Alshaimaa
A1  - Kliem, Bernhard
A1  - Seehafer, Norbert
A1  - Török, Tibor
T1  - A model of homologous confined and ejective eruptions involving kink instability and flux cancellation
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - In this study, we model a sequence of a confined and a full eruption, employing the relaxed end state of the confined eruption of a kink-unstable flux rope as the initial condition for the ejective one. The full eruption, a model of a coronal mass ejection, develops as a result of converging motions imposed at the photospheric boundary, which drive flux cancellation. In this process, parts of the positive and negative external flux converge toward the polarity inversion line, reconnect, and cancel each other. Flux of the same amount as the canceled flux transfers to a flux rope, increasing the free magnetic energy of the coronal field. With sustained flux cancellation and the associated progressive weakening of the magnetic tension of the overlying flux, we find that a flux reduction of approximate to 11% initiates the torus instability of the flux rope, which leads to a full eruption. These results demonstrate that a homologous full eruption, following a confined one, can be driven by flux cancellation.
Y1  - 2022
U6  - https://doi.org/10.3847/2041-8213/ac64a9
SN  - 2041-8205
SN  - 2041-8213
VL  - 929
IS  - 2
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Grebenkov, Denis S.
A1  - Metzler, Ralf
A1  - Oshanin, Gleb
T1  - A molecular relay race: sequential first-passage events to the terminal reaction centre in a cascade of diffusion controlled processes
JF  - New Journal of Physics (NJP)
N2  - We consider a sequential cascade of molecular first-reaction events towards a terminal reaction centre in which each reaction step is controlled by diffusive motion of the particles. The model studied here represents a typical reaction setting encountered in diverse molecular biology systems, in which, e.g. a signal transduction proceeds via a series of consecutive 'messengers': the first messenger has to find its respective immobile target site triggering a launch of the second messenger, the second messenger seeks its own target site and provokes a launch of the third messenger and so on, resembling a relay race in human competitions. For such a molecular relay race taking place in infinite one-, two- and three-dimensional systems, we find exact expressions for the probability density function of the time instant of the terminal reaction event, conditioned on preceding successful reaction events on an ordered array of target sites. The obtained expressions pertain to the most general conditions: number of intermediate stages and the corresponding diffusion coefficients, the sizes of the target sites, the distances between them, as well as their reactivities are arbitrary.
KW  - diffusion
KW  - reaction cascade
KW  - first passage time
Y1  - 2021
U6  - https://doi.org/10.1088/1367-2630/ac1e42
SN  - 1367-2630
VL  - 23
PB  - IOP - Institute of Physics Publishing
CY  - Bristol
ER  - 
TY  - JOUR
A1  - González-Galán, Ana
A1  - Oskinova, Lida
A1  - Popov, Sergei B.
A1  - Haberl, F.
A1  - Kühnel, M.
A1  - Gallagher, John S.
A1  - Schurch, Matthew
A1  - Guerrero, Martín A.
T1  - A multiwavelength study of SXP 1062, the long-period X-ray pulsar associated with a supernova remnant
JF  - Monthly notices of the Royal Astronomical Society
N2  - SXP 1062 is a Be X-ray binary (BeXB) located in the Small Magellanic Cloud. It hosts a long-period X-ray pulsar and is likely associated with the supernova remnant MCSNR J0127−7332. In this work we present a multiwavelength view on SXP 1062 in different luminosity regimes. We consider monitoring campaigns in optical (OGLE survey) and X-ray (Swift telescope). During these campaigns a tight coincidence of X-ray and optical outbursts is observed. We interpret this as typical Type I outbursts as often detected in BeXBs at periastron passage of the neutron star (NS). To study different X-ray luminosity regimes in depth, during the source quiescence we observed it with XMM–Newton while Chandra observations followed an X-ray outburst. Nearly simultaneously with Chandra observations in X-rays, in optical the RSS/SALT telescope obtained spectra of SXP 1062. On the basis of our multiwavelength campaign we propose a simple scenario where the disc of the Be star is observed face-on, while the orbit of the NS is inclined with respect to the disc. According to the model of quasi-spherical settling accretion our estimation of the magnetic field of the pulsar in SXP 1062 does not require an extremely strong magnetic field at the present time.
KW  - stars: neutron
KW  - pulsars: individual: SXP 1062
KW  - galaxies: individual: Small Magellanic Cloud
KW  - X-rays: binaries
Y1  - 2017
U6  - https://doi.org/10.1093/mnras/stx3127
SN  - 0035-8711
SN  - 1365-2966
VL  - 475
IS  - 2
SP  - 2809
EP  - 2821
PB  - Oxford University Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Liebig, Ferenc
A1  - Henning, Ricky
A1  - Sarhan, Radwan Mohamed
A1  - Prietzel, Claudia Christina
A1  - Bargheer, Matias
A1  - Koetz, Joachim
T1  - A new route to gold nanoflowers
JF  - Nanotechnology
N2  - Catanionic vesicles spontaneously formed by mixing the anionic surfactant bis(2-ethylhexyl)sulfosuccinate sodium salt with the cationic surfactant cetyltrimethylammonium bromide were used as a reducing medium to produce gold clusters, which are embedded and well-ordered into the template phase. The gold clusters can be used as seeds in the growth process that follows by adding ascorbic acid as a mild reducing component. When the ascorbic acid was added very slowly in an ice bath round-edged gold nanoflowers were produced. When the same experiments were performed at room temperature in the presence of Ag+ ions, sharp-edged nanoflowers could be synthesized. The mechanism of nanoparticle formation can be understood to be a non-diffusion-limited Ostwald ripening process of preordered gold nanoparticles embedded in catanionic vesicle fragments. Surface-enhanced Raman scattering experiments show an excellent enhancement factor of 1.7 . 10(5) for the nanoflowers deposited on a silicon wafer.
KW  - catanionic vesicles
KW  - gold cluster
KW  - gold nanoflowers
KW  - crystal growth
KW  - HRTEM
KW  - SEM
Y1  - 2018
U6  - https://doi.org/10.1088/1361-6528/aaaffd
SN  - 0957-4484
SN  - 1361-6528
VL  - 29
IS  - 18
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Assagra, Yuri A.O.
A1  - Altafim, Ruy Alberto Pisani
A1  - do Carmo, Joao P.
A1  - Altafim, Ruy A.C.
A1  - Rychkov, Dmitry
A1  - Wirges, Werner
A1  - Gerhard, Reimund
T1  - A new route to piezo-polymer transducers: 3D printing of polypropylene ferroelectrets
JF  - IEEE transactions on dielectrics and electrical insulation
N2  - Here, a promising approach for producing piezo-polymer transducers in a one-step process is presented. Using 3D-printing technology and polypropylene (PP) filaments, we are able to print a two-layered film structure with regular cavities of precisely controlled size and shape. It is found that the 3D-printed samples exhibit piezoelectric coefficients up to 200 pC/N, similar to those of other PP ferroelectrets, and their temporal and thermal behavior is in good agreement with those known of PP ferroelectrets. The piezoelectric response strongly decreases for applied pressures above 20 kPa, as the pressure in the air-filled cavities strongly influences the overall elastic modulus of ferroelectrets.
KW  - 3D printing
KW  - polymer ferroelectrets
KW  - sensors and actuators
KW  - piezoelectrets
KW  - electret polymers
KW  - soft electro-active materials
KW  - functional materials
KW  - soft matter
Y1  - 2020
U6  - https://doi.org/10.1109/TDEI.2020.008461
SN  - 1070-9878
SN  - 1558-4135
VL  - 27
IS  - 5
SP  - 1668
EP  - 1674
PB  - Inst. of Electr. and Electronics Engineers
CY  - Piscataway
ER  - 
TY  - JOUR
A1  - Gómez-Nava, Luis
A1  - Grossmann, Robert
A1  - Hintsche, Marius
A1  - Beta, Carsten
A1  - Peruani, Fernando
T1  - A novel approach to chemotaxis
BT  - active particles guided by internal clocks
JF  - epl : a letters journal exploring the frontiers of physics
N2  - Motivated by the observation of non-exponential run-time distributions of bacterial swimmers, we propose a minimal phenomenological model for taxis of active particles whose motion is controlled by an internal clock. The ticking of the clock depends on an external concentration field, e.g., a chemical substance. We demonstrate that these particles can detect concentration gradients and respond to them by moving up- or down-gradient depending on the clock design, albeit measurements of these fields are purely local in space and instantaneous in time. Altogether, our results open a new route in the study of directional navigation: we show that the use of a clock to control motility actions represents a generic and versatile toolbox to engineer behavioral responses to external cues, such as light, chemical, or temperature gradients.
Y1  - 2020
U6  - https://doi.org/10.1209/0295-5075/130/68002
SN  - 0295-5075
SN  - 1286-4854
VL  - 130
IS  - 6
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Gostkowska-Lekner, Natalia Katarzyna
A1  - Wallacher, Dirk
A1  - Grimm, Nico
A1  - Habicht, Klaus
A1  - Hofmann, Tommy
T1  - A novel electrochemical anodization cell for the synthesis of mesoporous silicon
JF  - Review of scientific instruments : a monthly journal devoted to scientific instruments, apparatus, and techniques
N2  - A novel design of an electrochemical anodization cell dedicated to the synthesis of mesoporous, single-crystalline silicon is presented. First and foremost, the design principle follows user safety since electrochemical etching of silicon requires highly hazardous electrolytes based on hydrofluoric (HF) acid. The novel cell design allows for safe electrolyte handling prior, during, and post-etching. A peristaltic pump with HF-resistant fluoroelastomer tubing transfers electrolytes between dedicated reservoirs and the anodization cell. Due to the flexibility of the cell operation, different processing conditions can be realized providing a large parameter range for the attainable sample thickness, its porosity, and the mean pore size. Rapid etching on the order of several minutes to synthesize micrometer-thick porous silicon epilayers on bulk silicon is possible as well as long-time etching with continuous, controlled electrolyte flow for several days to prepare up to 1000 mu m thick self-supporting porous silicon membranes. A highly adaptable, LabVIEW((TM))-based control software allows for user-defined etching profiles.
Y1  - 2020
U6  - https://doi.org/10.1063/5.0008536
SN  - 0034-6748
SN  - 1089-7623
VL  - 91
IS  - 10
PB  - American Institute of Physics
CY  - Melville, NY
ER  - 
TY  - JOUR
A1  - Großmann, Robert
A1  - Aranson, Igor S.
A1  - Peruani, Fernando
T1  - A particle-field approach bridges phase separation and collective motion in active matter
JF  - Nature Communications
N2  - Whereas self-propelled hard discs undergo motility-induced phase separation, self-propelled rods exhibit a variety of nonequilibrium phenomena, including clustering, collective motion, and spatio-temporal chaos. In this work, we present a theoretical framework representing active particles by continuum fields. This concept combines the simplicity of alignment-based models, enabling analytical studies, and realistic models that incorporate the shape of self-propelled objects explicitly. By varying particle shape from circular to ellipsoidal, we show how nonequilibrium stresses acting among self-propelled rods destabilize motility-induced phase separation and facilitate orientational ordering, thereby connecting the realms of scalar and vectorial active matter. Though the interaction potential is strictly apolar, both, polar and nematic order may emerge and even coexist. Accordingly, the symmetry of ordered states is a dynamical property in active matter. The presented framework may represent various systems including bacterial colonies, cytoskeletal extracts, or shaken granular media. Interacting self-propelled particles exhibit phase separation or collective motion depending on particle shape. A unified theory connecting these paradigms represents a major challenge in active matter, which the authors address here by modeling active particles as continuum fields.
Y1  - 2020
U6  - https://doi.org/10.1038/s41467-020-18978-5
SN  - 2041-1723
VL  - 11
IS  - 1
PB  - Nature Publishing Group
CY  - London
ER  - 
TY  - JOUR
A1  - Malass, Ihsane
A1  - Tarkhanov, Nikolaj Nikolaevič
T1  - A perturbation of the de Rham complex
T1  - Возмущение комплекса де Рама
JF  - Journal of Siberian Federal University : Mathematics & Physics
JF  - Žurnal Sibirskogo Federalʹnogo Universiteta : Matematika i fizika
N2  - We consider a perturbation of the de Rham complex on a compact manifold with boundary. This perturbation goes beyond the framework of complexes, and so cohomology does not apply to it. On the other hand, its curvature is "small", hence there is a natural way to introduce an Euler characteristic and develop a Lefschetz theory for the perturbation. This work is intended as an attempt to develop a cohomology theory for arbitrary sequences of linear mappings.
N2  - Рассмотрим возмущение комплекса де Рама на компактном многообразии с краем. Это возмущение выходит за рамки комплексов, и поэтому когомологии к нему не относятся. С другой стороны, его кривизна "мала", поэтому существует естественный способ ввести характеристику Эйлера и разработать теорию Лефшеца для возмущения. Данная работа предназначена для попытки разработать теорию когомологий для произвольных последовательностей линейных отображений.
KW  - de Rham complex
KW  - cohomology
KW  - Hodge theory
KW  - Neumann problem
KW  - комплекс де Рама
KW  - когомологии
KW  - теория Ходжа
KW  - проблема Неймана
Y1  - 2020
U6  - https://doi.org/10.17516/1997-1397-2020-13-5-519-532
SN  - 1997-1397
SN  - 2313-6022
VL  - 13
IS  - 5
SP  - 519
EP  - 532
PB  - Siberian Federal University
CY  - Krasnojarsk
ER  - 
TY  - JOUR
A1  - Sachse, Manuel
T1  - A planetary dust ring generated by impact-ejection from the Galilean satellites
JF  - Icarus : international journal of solar system studies
N2  - All outer planets in the Solar System are surrounded by a ring system. Many of these rings are dust rings or they contain at least a high proportion of dust. They are often formed by impacts of micro-meteoroids onto embedded bodies. The ejected material typically consists of micron-sized charged particles, which are susceptible to gravitational and non-gravitational forces. Generally, detailed information on the dynamics and distribution of the dust requires expensive numerical simulations of a large number of particles. Here we develop a relatively simple and fast, semi-analytical model for an impact-generated planetary dust ring governed by the planet’s gravity and the relevant perturbation forces for the dynamics of small charged particles. The most important parameter of the model is the dust production rate, which is a linear factor in the calculation of the dust densities. We apply our model to dust ejected from the Galilean satellites using production rates obtained from flybys of the dust sources. The dust densities predicted by our model are in good agreement with numerical simulations and with in situ measurements by the Galileo spacecraft. The lifetimes of large particles are about two orders of magnitude greater than those of small ones, which implies a flattening of the size distribution in circumplanetary space. Information about the distribution of circumplanetary dust is also important for the risk assessment of spacecraft orbits in the respective regions.
Y1  - 0207
U6  - https://doi.org/10.1016/j.icarus.2017.10.011
SN  - 0019-1035
SN  - 1090-2643
VL  - 303
SP  - 166
EP  - 180
PB  - Elsevier
CY  - San Diego
ER  - 
TY  - JOUR
A1  - Hintsche, Marius
A1  - Waljor, Veronika
A1  - Grossmann, Robert
A1  - Kühn, Marco J.
A1  - Thormann, Kai M.
A1  - Peruani, Fernando
A1  - Beta, Carsten
T1  - A polar bundle of flagella can drive bacterial swimming by pushing, pulling, or coiling around the cell body
JF  - Scientific reports
N2  - Bacteria swim in sequences of straight runs that are interrupted by turning events. They drive their swimming locomotion with the help of rotating helical flagella. Depending on the number of flagella and their arrangement across the cell body, different run-and-turn patterns can be observed. Here, we present fluorescence microscopy recordings showing that cells of the soil bacterium Pseudomonas putida that are decorated with a polar tuft of helical flagella, can alternate between two distinct swimming patterns. On the one hand, they can undergo a classical push-pull-push cycle that is well known from monopolarly flagellated bacteria but has not been reported for species with a polar bundle of multiple flagella. Alternatively, upon leaving the pulling mode, they can enter a third slow swimming phase, where they propel themselves with their helical bundle wrapped around the cell body. A theoretical estimate based on a random-walk model shows that the spreading of a population of swimmers is strongly enhanced when cycling through a sequence of pushing, pulling, and wrapped flagellar configurations as compared to the simple push-pull-push pattern.
Y1  - 2017
U6  - https://doi.org/10.1038/s41598-017-16428-9
SN  - 2045-2322
VL  - 7
PB  - Macmillan Publishers Limited, part of Springer Nature
CY  - London
ER  - 
TY  - JOUR
A1  - Bouma, Sietske Jeltje Deirdre
A1  - Richter, Philipp
A1  - Fechner, Cora
T1  - A population of high-velocity absorption-line systems residing in the Local Group
JF  - Astronomy and astrophysics : an international weekly journal
N2  - Aims. We investigated the ionisation conditions and distances of Galactic high-velocity clouds (HVCs) in the Galactic halo and beyond in the direction of the Local Group (LG) barycentre and anti-barycentre, by studying spectral data of 29 extragalactic background sources obtained with the Cosmic Origins Spectropgraph (COS) installed on the Hubble Space Telescope (HST). Methods. We model column-densities of low, intermediate, and high ions such as Si ii, C ii, Si iii, Si vi, and C iv, and use these data to construct a set of Cloudy ionisation models. Results. In total, we found 69 high-velocity absorption components along the 29 lines of sight. The components in the direction of the LG barycentre span the entire range of studied velocities, 100 less than or similar to vertical bar nu(LSR)vertical bar less than or similar to 400 km s(-1), while those in the anti-barycentre sample have velocities up to about 300 km s(-1). For 49 components, we infer the gas densities. In the direction of the LG barycentre, the gas densities exhibit a wide range from log nH = -3.96 to -2.55, while in the anti-barycentre direction the densities are systematically higher, log nH > -3.25. The barycentre absorbers can be split into two groups based on their density: a high-density group with log nH > -3.54, which can be affected by the Milky Way radiation field, and a low-density group (log nH <= -3.54). The latter has very low thermal pressures of P/k < 7.3 Kcm(-3). Conclusions. Our study shows that part of the absorbers in the LG barycentre direction trace gas at very low gas densities and thermal pressures. These properties indicate that the absorbers are located beyond the virial radius of the Milky Way. Our study also confirms results from earlier, single-sightline studies, suggesting the presence of a metal-enriched intragroup medium filling the LG near its barycentre.
KW  - Galaxy: halo
KW  - Galaxy: structure
KW  - Galaxy: evolution
KW  - ISM: kinematics and dynamics
KW  - techniques: spectroscopic
KW  - ultraviolet: ISM
Y1  - 2019
U6  - https://doi.org/10.1051/0004-6361/201935078
SN  - 1432-0746
VL  - 627
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Postnov, K.
A1  - Oskinova, Lida
A1  - Torrejon, J. M.
T1  - A propelling neutron star in the enigmatic Be-star gamma Cassiopeia
JF  - Monthly notices of the Royal Astronomical Society
N2  - gamma Cassiopeia (gamma Cas), is known to be a binary system consisting of a Be-type star and a low-mass (M similar to 1M(circle dot)) companion of unknown nature orbiting in the Be-disc plane. Here, we apply the quasi-spherical accretion theory on to a compact magnetized star and show that if the low-mass companion of gamma Cas is a fast spinning neutron star, the key observational signatures of. Cas are remarkably well reproduced. Direct accretion on to this fast rotating neutron star is impeded by the propeller mechanism. In this case, around the neutron star magnetosphere a hot shell is formed which emits thermal X-rays in qualitative and quantitative agreement with observed properties of the X-ray emission from gamma Cas. We suggest that gamma Cas and its analogues constitute a new subclass of Be-type X-ray binaries hosting rapidly rotating neutron stars formed in supernova explosions with small kicks. The subsequent evolutionary stage of gamma Cas and its analogues should be the X Per-type binaries comprising low-luminosity slowly rotating X-ray pulsars. The model explains the enigmatic X-ray emission from gamma Cas, and also establishes evolutionary connections between various types of rotating magnetized neutron stars in Be-binaries.
KW  - stars: emission-line, Be
KW  - stars: neutron
Y1  - 2017
U6  - https://doi.org/10.1093/mnrasl/slw223
SN  - 0035-8711
SN  - 1365-2966
VL  - 465
IS  - 1
SP  - L119
EP  - L123
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Schaffenroth, Veronika
A1  - Casewell, Sarah L.
A1  - Schneider, D.
A1  - Kilkenny, David
A1  - Geier, Stephan
A1  - Heber, Ulrich
A1  - Irrgang, Andreas
A1  - Przybilla, Norbert
A1  - Marsh, Thomas R.
A1  - Littlefair, Stuart P.
A1  - Dhillon, Vik S.
T1  - A quantitative in-depth analysis of the prototype sdB plus BD system SDSS J08205+0008 revisited in the Gaia era
JF  - Monthly notices of the Royal Astronomical Society
N2  - Subdwarf B stars are core-helium-burning stars located on the extreme horizontal branch (EHB). Extensive mass loss on the red giant branch is necessary to form them. It has been proposed that substellar companions could lead to the required mass loss when they are engulfed in the envelope of the red giant star. J08205+0008 was the first example of a hot subdwarf star with a close, substellar companion candidate to be found. Here, we perform an in-depth re-analysis of this important system with much higher quality data allowing additional analysis methods. From the higher resolution spectra obtained with ESO-VLT/XSHOOTER, we derive the chemical abundances of the hot subdwarf as well as its rotational velocity. Using the Gaia parallax and a fit to the spectral energy distribution in the secondary eclipse, tight constraints to the radius of the hot subdwarf are derived. From a long-term photometric campaign, we detected a significant period decrease of -3.2(8) x 10(-12) dd(-1). This can be explained by the non-synchronized hot subdwarf star being spun up by tidal interactions forcing it to become synchronized. From the rate of period decrease we could derive the synchronization time-scale to be 4 Myr, much smaller than the lifetime on EHB. By combining all different methods, we could constrain the hot subdwarf to a mass of 0.39-0.50 M-circle dot and a radius of R-sdB = 0.194 +/- 0.008 R-circle dot, and the companion to 0.061-0.071 M-circle dot with a radius of R-comp = 0.092 +/- 0.005 R-circle dot, below the hydrogen-burning limit. We therefore confirm that the companion is most likely a massive brown dwarf.
KW  - stars: abundances
KW  - stars: atmospheres
KW  - stars: fundamental parameters
KW  - stars: horizontal branch
KW  - stars: low-mass
KW  - subdwarfs
Y1  - 2020
U6  - https://doi.org/10.1093/mnras/staa3661
SN  - 0035-8711
SN  - 1365-2966
VL  - 501
IS  - 3
SP  - 3847
EP  - 3870
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Hantschmann, Markus
A1  - Föhlisch, Alexander
T1  - A rate model approach for FEL pulse induced transmissions changes, saturable absorption, X-ray transparency and stimulated emission
JF  - Journal of electron spectroscopy and related phenomena : the international journal on theoretical and experimental aspects of electron spectroscopy
N2  - As the use of free electron laser (FEL) sources increases, so do the findings mentioning non-linear phenomena occurring at these experiments, such as saturable absorption, induced transparency and scattering breakdowns. These are well known among the laser community, but are still rarely understood and expected among the X-ray community and to date lack tools and theories to accurately predict the respective experimental parameters and results. We present a simple theoretical framework to access short X-ray pulse induced light- matter interactions which occur at intense short X-ray pulses as available at FEL sources. Our approach allows to investigate effects such as saturable absorption, induced transparency and scattering suppression, stimulated emission, and transmission spectra, while including the density of state influence relevant to soft X-ray spectroscopy in, for example, transition metal complexes or functional materials. This computationally efficient rate model based approach is intuitively adaptable to most solid state sample systems in the soft X-ray spectrum with the potential to be extended for liquid and gas sample systems as well. The feasibility of the model to estimate the named effects and the influence of the density of state is demonstrated using the example of CoPd transition metal systems at the Co edge. We believe this work is an important contribution for the preparation, performance, and understanding of FEL based high intensity and short pulse experiments, especially on functional materials in the soft X-ray spectrum.
KW  - Free-electron-laser science
KW  - RIXS at FELs
KW  - Stimulated scattering
KW  - Pulse induced transparency
KW  - Scattering breakdown
Y1  - 2022
U6  - https://doi.org/10.1016/j.elspec.2021.147139
SN  - 0368-2048
VL  - 256
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Hanisch, Florian
A1  - Ludewig, Matthias
T1  - A rigorous construction of the supersymmetric path integral associated to a compact spin manifold
JF  - Communications in mathematical physics
N2  - We give a rigorous construction of the path integral in N = 1/2 supersymmetry as an integral map for differential forms on the loop space of a compact spin manifold. It is defined on the space of differential forms which can be represented by extended iterated integrals in the sense of Chen and Getzler-Jones-Petrack. Via the iterated integral map, we compare our path integral to the non-commutative loop space Chern character of Guneysu and the second author. Our theory provides a rigorous background to various formal proofs of the Atiyah-Singer index theorem for twisted Dirac operators using supersymmetric path integrals, as investigated by Alvarez-Gaume, Atiyah, Bismut and Witten.
Y1  - 2022
U6  - https://doi.org/10.1007/s00220-022-04336-7
SN  - 0010-3616
SN  - 1432-0916
VL  - 391
IS  - 3
SP  - 1209
EP  - 1239
PB  - Springer
CY  - Berlin ; Heidelberg
ER  - 
TY  - JOUR
A1  - Abdalla, Hassan E.
A1  - Abramowski, A.
A1  - Aharonian, Felix A.
A1  - Benkhali, F. Ait
A1  - Akhperjanian, A. G.
A1  - Andersson, T.
A1  - Anguener, E. O.
A1  - Arakawa, M.
A1  - Arrieta, M.
A1  - Aubert, P.
A1  - Backes, M.
A1  - Balzer, A.
A1  - Barnard, M.
A1  - Becherini, Y.
A1  - Tjus, J. Becker
A1  - Berge, D.
A1  - Bernhard, S.
A1  - Bernloehr, K.
A1  - Blackwell, R.
A1  - Boettcher, M.
A1  - Boisson, C.
A1  - Bolmont, J.
A1  - Bonnefoy, S.
A1  - Bordas, Pol
A1  - Bregeon, J.
A1  - Brun, F.
A1  - Brun, P.
A1  - Bryan, M.
A1  - Buechele, M.
A1  - Bulik, T.
A1  - Capasso, M.
A1  - Carr, J.
A1  - Casanova, Sabrina
A1  - Cerruti, M.
A1  - Chakraborty, N.
A1  - Chaves, R. C. G.
A1  - Chen, A.
A1  - Chevalier, J.
A1  - Coffaro, M.
A1  - Colafrancesco, S.
A1  - Cologna, G.
A1  - Condon, B.
A1  - Conrad, J.
A1  - Cui, Y.
A1  - Davids, I. D.
A1  - Decock, J.
A1  - Degrange, B.
A1  - Deil, C.
A1  - Devin, J.
A1  - deWilt, P.
A1  - Dirson, L.
A1  - Djannati-Atai, A.
A1  - Domainko, W.
A1  - Donath, A.
A1  - Dutson, K.
A1  - Dyks, J.
A1  - Edwards, T.
A1  - Egberts, Kathrin
A1  - Eger, P.
A1  - Ernenwein, J. -P.
A1  - Eschbach, S.
A1  - Farnier, C.
A1  - Fegan, S.
A1  - Fernandes, M. V.
A1  - Fiasson, A.
A1  - Fontaine, G.
A1  - Foerster, A.
A1  - Funk, S.
A1  - Fuessling, M.
A1  - Gabici, S.
A1  - Gajdus, M.
A1  - Gallant, Y. A.
A1  - Garrigoux, T.
A1  - Giavitto, G.
A1  - Giebels, B.
A1  - Glicenstein, J. F.
A1  - Gottschall, D.
A1  - Goyal, A.
A1  - Grondin, M. -H.
A1  - Hahn, J.
A1  - Haupt, M.
A1  - Hawkes, J.
A1  - Heinzelmann, G.
A1  - Henri, G.
A1  - Hermann, G.
A1  - Hervet, O.
A1  - Hinton, J. A.
A1  - Hofmann, W.
A1  - Hoischen, Clemens
A1  - Holch, T. L.
A1  - Holler, M.
A1  - Horns, D.
A1  - Ivascenko, A.
A1  - Iwasaki, H.
A1  - Jacholkowska, A.
A1  - Jamrozy, M.
A1  - Janiak, M.
A1  - Jankowsky, D.
A1  - Jankowsky, F.
A1  - Jingo, M.
A1  - Jogler, T.
A1  - Jouvin, L.
A1  - Jung-Richardt, I.
A1  - Kastendieck, M. A.
A1  - Katarzynski, K.
A1  - Katsuragawa, M.
A1  - Katz, U.
A1  - Kerszberg, D.
A1  - Khangulyan, D.
A1  - Khelifi, B.
A1  - King, J.
A1  - Klepser, S.
A1  - Klochkov, D.
A1  - Kluzniak, W.
A1  - Kolitzus, D.
A1  - Komin, Nu.
A1  - Kosack, K.
A1  - Krakau, S.
A1  - Kraus, M.
A1  - Krueger, P. P.
A1  - Laffon, H.
A1  - Lamanna, G.
A1  - Lau, J.
A1  - Lees, J. -P.
A1  - Lefaucheur, J.
A1  - Lefranc, V.
A1  - Lemiere, A.
A1  - Lemoine-Goumard, M.
A1  - Lenain, J. -P.
A1  - Leser, Eva
A1  - Lohse, T.
A1  - Lorentz, M.
A1  - Liu, R.
A1  - Lopez-Coto, R.
A1  - Lypova, I.
A1  - Marandon, V.
A1  - Marcowith, Alexandre
A1  - Mariaud, C.
A1  - Marx, R.
A1  - Maurin, G.
A1  - Maxted, N.
A1  - Mayer, M.
A1  - Meintjes, P. J.
A1  - Meyer, M.
A1  - Mitche, A. M. W.
A1  - Moderski, R.
A1  - Mohamed, M.
A1  - Mohrmann, L.
A1  - Mora, K.
A1  - Moulin, Emmanuel
A1  - Murach, T.
A1  - Nakashima, S.
A1  - de Naurois, M.
A1  - Niederwanger, F.
A1  - Niemiec, J.
A1  - Oakes, L.
A1  - Odaka, H.
A1  - Oettl, S.
A1  - Ohm, S.
A1  - Ostrowski, M.
A1  - Oya, I.
A1  - Padovani, M.
A1  - Panter, M.
A1  - Parsons, R. D.
A1  - Pekeur, N. W.
A1  - Pelletier, G.
A1  - Perennes, C.
A1  - Petrucci, P. -O.
A1  - Peyaud, B.
A1  - Piel, Q.
A1  - Pita, S.
A1  - Poon, H.
A1  - Prokhorov, D.
A1  - Prokoph, H.
A1  - Puehlhofer, G.
A1  - Punch, M.
A1  - Quirrenbach, A.
A1  - Raab, S.
A1  - Reimer, A.
A1  - Reimer, O.
A1  - Renaud, M.
A1  - de los Reyes, R.
A1  - Richter, S.
A1  - Rieger, F.
A1  - Romoli, C.
A1  - Rowell, G.
A1  - Rudak, B.
A1  - Rulten, C. B.
A1  - Sahakian, V.
A1  - Saito, S.
A1  - Salek, D.
A1  - Sanchez, D. A.
A1  - Santangelo, Andrea
A1  - Sasaki, M.
A1  - Schlickeiser, R.
A1  - Schuessler, F.
A1  - Schulz, A.
A1  - Schwanke, U.
A1  - Schwemmer, S.
A1  - Seglar-Arroyo, M.
A1  - Settimo, M.
A1  - Seyffert, A. S.
A1  - Shafi, N.
A1  - Shilon, I.
A1  - Simoni, R.
A1  - Sol, H.
A1  - Spanier, F.
A1  - Spengler, G.
A1  - Spies, F.
A1  - Stawarz, L.
A1  - Steenkamp, R.
A1  - Stegmann, Christian
A1  - Stycz, K.
A1  - Sushch, I.
A1  - Takahashi, T.
A1  - Tavernet, J. -P.
A1  - Tavernier, T.
A1  - Taylor, A. M.
A1  - Terrier, R.
A1  - Tibaldo, L.
A1  - Tiziani, D.
A1  - Tluczykont, M.
A1  - Trichard, C.
A1  - Tsuji, N.
A1  - Tuffs, R.
A1  - Uchiyama, Y.
A1  - van der Wale, D. J.
A1  - van Eldik, C.
A1  - van Rensburg, C.
A1  - van Soelen, B.
A1  - Vasileiadis, G.
A1  - Veh, J.
A1  - Venter, C.
A1  - Viana, A.
A1  - Vincent, P.
A1  - Vink, J.
A1  - Voisin, F.
A1  - Voelk, H. J.
A1  - Vuillaume, T.
A1  - Wadiasingh, Z.
A1  - Wagner, S. J.
A1  - Wagner, P.
A1  - Wagner, R. M.
A1  - White, R.
A1  - Wierzcholska, A.
A1  - Willmann, P.
A1  - Woernlein, A.
A1  - Wouters, D.
A1  - Yang, R.
A1  - Zabalza, V.
A1  - Zaborov, D.
A1  - Zacharias, M.
A1  - Zanin, R.
A1  - Zdziarski, A. A.
A1  - Zech, Alraune
A1  - Zefi, F.
A1  - Ziegler, A.
A1  - Zywucka, N.
A1  - Bamba, A.
A1  - Fukui, Y.
A1  - Sano, H.
A1  - Yoshiike, S.
T1  - A search for new supernova remnant shells in the Galactic plane with HESS
JF  - Astronomy and astrophysics : an international weekly journal
N2  - A search for new supernova remnants (SNRs) has been conducted using TeV gamma-ray data from the H.E.S.S. Galactic plane survey. As an identification criterion, shell morphologies that are characteristic for known resolved TeV SNRs have been used. Three new SNR candidates were identified in the H.E.S.S. data set with this method. Extensive multiwavelength searches for counterparts were conducted. A radio SNR candidate has been identified to be a counterpart to HESS J1534-571. The TeV source is therefore classified as a SNR. For the other two sources, HESS J1614-518 and HESS J1912 + 101, no identifying counterparts have been found, thus they remain SNR candidates for the time being. TeV-emitting SNRs are key objects in the context of identifying the accelerators of Galactic cosmic rays. The TeV emission of the relativistic particles in the new sources is examined in view of possible leptonic and hadronic emission scenarios, taking the current multiwavelength knowledge into account.
KW  - astroparticle physics
KW  - ISM: supernova remnants
KW  - cosmic rays
Y1  - 2018
U6  - https://doi.org/10.1051/0004-6361/201730737
SN  - 1432-0746
VL  - 612
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Archer, A.
A1  - Benbow, Wystan
A1  - Bird, Ralph
A1  - Brose, Robert
A1  - Buchovecky, M.
A1  - Buckley, J. H.
A1  - Chromey, A. J.
A1  - Cui, Wei
A1  - Falcone, A.
A1  - Feng, Qi
A1  - Finley, J. P.
A1  - Fortson, Lucy
A1  - Furniss, Amy
A1  - Gent, A.
A1  - Gueta, O.
A1  - Hanna, David
A1  - Hassan, T.
A1  - Hervet, Olivier
A1  - Holder, J.
A1  - Hughes, G.
A1  - Humensky, T. B.
A1  - Johnson, Caitlin A.
A1  - Kaaret, Philip
A1  - Kar, P.
A1  - Kelley-Hoskins, N.
A1  - Kertzman, M.
A1  - Kieda, David
A1  - Krennrich, F.
A1  - Kumar, S.
A1  - Lang, M. J.
A1  - Lin, T. T. Y.
A1  - McCann, A.
A1  - Moriarty, P.
A1  - Mukherjee, Reshmi
A1  - Ong, R. A.
A1  - Otte, Adam Nepomuk
A1  - Pandel, D.
A1  - Park, N.
A1  - Petrashyk, A.
A1  - Pohl, Martin
A1  - Pueschel, Elisa
A1  - Quinn, J.
A1  - Ragan, K.
A1  - Richards, Gregory T.
A1  - Roache, E.
A1  - Sadeh, I
A1  - Santander, Marcos
A1  - Scott, S. S.
A1  - Sembroski, G. H.
A1  - Shahinyan, Karlen
A1  - Sushch, Iurii
A1  - Tyler, J.
A1  - Wakely, S. P.
A1  - Weinstein, A.
A1  - Wells, R. M.
A1  - Wilcox, P.
A1  - Wilhelm, Alina
A1  - Williams, D. A.
A1  - Williamson, T. J.
A1  - Zitzer, B.
T1  - A Search for Pulsed Very High-energy Gamma-Rays from 13 Young Pulsars in Archival VERITAS Data
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - We conduct a search for periodic emission in the very high-energy (VHE) gamma-ray band (E > 100 GeV) from a total of 13 pulsars in an archival VERITAS data set with a total exposure of over 450 hr. The set of pulsars includes many of the brightest young gamma-ray pulsars visible in the Northern Hemisphere. The data analysis resulted in nondetections of pulsed VHE gamma-rays from each pulsar. Upper limits on a potential VHE gamma-ray flux are derived at the 95% confidence level above three energy thresholds using two methods. These are the first such searches for pulsed VHE emission from each of the pulsars, and the obtained limits constrain a possible flux component manifesting at VHEs as is seen for the Crab pulsar.
KW  - gamma rays: general
KW  - pulsars: general
KW  - stars: neutron
Y1  - 2019
U6  - https://doi.org/10.3847/1538-4357/ab14f4
SN  - 0004-637X
SN  - 1538-4357
VL  - 876
IS  - 2
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Abdalla, Hassan E.
A1  - Abramowski, A.
A1  - Aharonian, Felix A.
A1  - Benkhali, F. Ait
A1  - Akhperjanian, A. G.
A1  - Anguenee, E. O.
A1  - Arrieta, M.
A1  - Aubert, P.
A1  - Backes, M.
A1  - Balzer, A.
A1  - Barnard, M.
A1  - Becherini, Y.
A1  - Tjus, J. Becker
A1  - Berge, D.
A1  - Bernhard, S.
A1  - Bernloehr, K.
A1  - Birsin, E.
A1  - Blackwell, R.
A1  - Boettcher, M.
A1  - Boisson, C.
A1  - Bolmont, J.
A1  - Bordas, Pol
A1  - Bregeon, J.
A1  - Brun, F.
A1  - Brun, P.
A1  - Bryan, M.
A1  - Bulik, T.
A1  - Capasso, M.
A1  - Carr, J.
A1  - Casanova, Sabrina
A1  - Chadwick, P. M.
A1  - Chakraborty, N.
A1  - Chalme-Calvet, R.
A1  - Chaves, R. C. G.
A1  - Chen, A.
A1  - Chevalier, J.
A1  - Chretien, M.
A1  - Colafrancesco, S.
A1  - Cologna, G.
A1  - Condon, B.
A1  - Conrad, J.
A1  - Couturier, C.
A1  - Cui, Y.
A1  - Davids, I. D.
A1  - Degrange, B.
A1  - Deil, C.
A1  - deWilt, P.
A1  - Dickinson, H. J.
A1  - Djannati-Atai, A.
A1  - Domainko, W.
A1  - Donath, A.
A1  - Dubus, G.
A1  - Dutson, K.
A1  - Dyks, J.
A1  - Dyrda, M.
A1  - Edwards, T.
A1  - Egberts, Kathrin
A1  - Eger, P.
A1  - Ernenwein, J. -P.
A1  - Eschbach, S.
A1  - Farnier, C.
A1  - Fegan, S.
A1  - Fernandes, M. V.
A1  - Fiasson, A.
A1  - Fontaine, G.
A1  - Foerster, A.
A1  - Funk, S.
A1  - Fuessling, M.
A1  - Gabici, S.
A1  - Gajdus, M.
A1  - Gallant, Y. A.
A1  - Garrigoux, T.
A1  - Giavitto, G.
A1  - Giebels, B.
A1  - Glicenstein, J. F.
A1  - Gottschall, D.
A1  - Goya, A.
A1  - Grondin, M. -H.
A1  - Grudzinska, M.
A1  - Hadasch, D.
A1  - Hahn, J.
A1  - Hawkes, J.
A1  - Heinzelmann, G.
A1  - Henri, G.
A1  - Hermann, G.
A1  - Hervet, O.
A1  - Hillert, A.
A1  - Hinton, J. A.
A1  - Hofmann, W.
A1  - Hoischen, Clemens
A1  - Holler, M.
A1  - Horns, D.
A1  - Ivascenko, A.
A1  - Jacholkowska, A.
A1  - Jamrozy, M.
A1  - Janiak, M.
A1  - Jankowsky, D.
A1  - Jankowsky, F.
A1  - Jingo, M.
A1  - Jogler, T.
A1  - Jouvin, L.
A1  - Jung-Richardt, I.
A1  - Kastendieck, M. A.
A1  - Katarzynski, K.
A1  - Katz, U.
A1  - Kerszberg, D.
A1  - Khelifi, B.
A1  - Kieffer, M.
A1  - King, J.
A1  - Klepser, S.
A1  - Klochkov, D.
A1  - Kluzniak, W.
A1  - Kolitzus, D.
A1  - Komin, Nu.
A1  - Kosack, K.
A1  - Krakau, S.
A1  - Kraus, M.
A1  - Krayzel, F.
A1  - Krueger, P. P.
A1  - Laffon, H.
A1  - Lamanna, G.
A1  - Lau, J.
A1  - Lees, J. -P.
A1  - Lefaucheur, J.
A1  - Lefranc, V.
A1  - Lemiere, A.
A1  - Lemoine-Goumard, M.
A1  - Lenain, J. -P.
A1  - Leser, Eva
A1  - Lohse, T.
A1  - Lorentz, M.
A1  - Liu, R.
A1  - Lypova, I.
A1  - Marandon, V.
A1  - Marcowith, Alexandre
A1  - Mariaud, C.
A1  - Marx, R.
A1  - Maurin, G.
A1  - Maxted, N.
A1  - Mayer, M.
A1  - Meintjes, P. J.
A1  - Menzler, U.
A1  - Meyer, M.
A1  - Mitchell, A. M. W.
A1  - Moderski, R.
A1  - Mohamed, M.
A1  - Mora, K.
A1  - Moulin, Emmanuel
A1  - Murach, T.
A1  - de Naurois, M.
A1  - Niederwanger, F.
A1  - Niemiec, J.
A1  - Oakes, L.
A1  - Odaka, H.
A1  - Oettl, S.
A1  - Ohm, S.
A1  - Ostrowski, M.
A1  - Oya, I.
A1  - Padovani, M.
A1  - Panter, M.
A1  - Parsons, R. D.
A1  - Arribas, M. Paz
A1  - Pekeur, N. W.
A1  - Pelletier, G.
A1  - Petrucci, P. -O.
A1  - Peyaud, B.
A1  - Pita, S.
A1  - Poona, H.
A1  - Prokhorov, D.
A1  - Prokoph, H.
A1  - Puehlhofer, G.
A1  - Punch, M.
A1  - Quirrenbach, A.
A1  - Raab, S.
A1  - Reimer, A.
A1  - Reimer, O.
A1  - Renaud, M.
A1  - de los Reyes, R.
A1  - Rieger, F.
A1  - Romoli, C.
A1  - Rosier-Lees, S.
A1  - Rowell, G.
A1  - Rudak, B.
A1  - Rulten, C. B.
A1  - Sahakian, V.
A1  - Salek, D.
A1  - Sanchez, D. A.
A1  - Santangelo, Andrea
A1  - Sasaki, M.
A1  - Schlickeiser, R.
A1  - Schuessler, F.
A1  - Schulz, A.
A1  - Schwanke, U.
A1  - Schwemmer, S.
A1  - Seyffert, A. S.
A1  - Shafi, N.
A1  - Shilon, I.
A1  - Simoni, R.
A1  - Sol, H.
A1  - Spanier, F.
A1  - Spengler, G.
A1  - Spies, F.
A1  - Stawarz, L.
A1  - Steenkamp, R.
A1  - Stegmann, Christian
A1  - Stinzing, F.
A1  - Stycz, K.
A1  - Sushch, I.
A1  - Tavernet, J. -P.
A1  - Tavernier, T.
A1  - Taylor, A. M.
A1  - Terrier, R.
A1  - Tluczykont, M.
A1  - Trichard, C.
A1  - Tuffs, R.
A1  - van der Walt, J.
A1  - van Eldik, C.
A1  - van Soelen, B.
A1  - Vasileiadis, G.
A1  - Veh, J.
A1  - Venters, C.
A1  - Viana, A.
A1  - Vincent, P.
A1  - Vink, J.
A1  - Voisin, F.
A1  - Voelk, H. J.
A1  - Vuillaume, T.
A1  - Wadiasingh, Z.
A1  - Wagner, S. J.
A1  - Wagner, P.
A1  - Wagner, R. M.
A1  - White, R.
A1  - Wierzcholska, A.
A1  - Willmann, P.
A1  - Woernlein, A.
A1  - Wouters, D.
A1  - Yang, R.
A1  - Zabalza, V.
A1  - Zaborov, D.
A1  - Zacharias, M.
A1  - Zdziarski, A. A.
A1  - Zech, Alraune
A1  - Zefi, F.
A1  - Ziegler, A.
A1  - Zywucka, N.
T1  - A search for very high-energy flares from the microquasars GRS 1915+105, Circinus X-1, and V4641 Sgr using contemporaneous HESS and RXTE observations
JF  - Astronomy and astrophysics : an international weekly journal
N2  - Context. Microquasars are potential gamma-ray emitters. Indications of transient episodes of gamma-ray emission were recently reported in at least two systems: Cyg X-1 and Cyg X-3. The identification of additional gamma-ray-emitting microquasars is required to better understand how gamma-ray emission can be produced in these systems. Aims. Theoretical models have predicted very high-energy (VHE) gamma-ray emission from microquasars during periods of transient outburst. Observations reported herein were undertaken with the objective of observing a broadband flaring event in the gamma-ray and X-ray bands. Methods. Contemporaneous observations of three microquasars, GRS 1915+105, Circinus X-1, and V4641 Sgr, were obtained using the High Energy Spectroscopic System (H.E.S.S.) telescope array and the Rossi X-ray Timing Explorer (RXTE) satellite. X-ray analyses for each microquasar were performed and VHE gamma-ray upper limits from contemporaneous H.E.S.S. observations were derived. Results. No significant gamma-ray signal has been detected in any of the three systems. The integral gamma-ray photon flux at the observational epochs is constrained to be I(>560 GeV) < 7.3 x 10(-13) cm(-2) S-1, I(>560 GeV) < 1.2 x 10-(12) cm s(-1), and I(>240 GeV) < 4.5 x 10(-12) cm(-2) s(-1) for GRS 1915+105, Circinus X-1, and V4641 Sgr, respectively. Conclusions. The gamma-ray upper limits obtained using H.E.S.S. are examined in the context of previous Cherenkov telescope observations of microquasars. The effect of intrinsic absorption is modelled for each target and found to have negligible impact on the flux of escaping gamma-rays. When combined with the X-ray behaviour observed using RXTE, the derived results indicate that if detectable VHE gamma-ray emission from microquasars is commonplace, then it is likely to be highly transient.
KW  - gamma rays: general
KW  - X-rays: binaries
KW  - X-rays: individuals: GRS 1915+105
KW  - X-rays: individuals: Circinus X-1
KW  - X-rays: individuals: V4641 Sgr
Y1  - 2018
U6  - https://doi.org/10.1051/0004-6361/201527773
SN  - 1432-0746
VL  - 612
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Herrmann, Carl J. J.
A1  - Metzler, Ralf
T1  - A self-avoiding walk with neural delays as a model of fixational eye movements
JF  - Scientific reports
N2  - Fixational eye movements show scaling behaviour of the positional mean-squared displacement with a characteristic transition from persistence to antipersistence for increasing time-lag. These statistical patterns were found to be mainly shaped by microsaccades (fast, small-amplitude movements). However, our re-analysis of fixational eye-movement data provides evidence that the slow component (physiological drift) of the eyes exhibits scaling behaviour of the mean-squared displacement that varies across human participants. These results suggest that drift is a correlated movement that interacts with microsaccades. Moreover, on the long time scale, the mean-squared displacement of the drift shows oscillations, which is also present in the displacement auto-correlation function. This finding lends support to the presence of time-delayed feedback in the control of drift movements. Based on an earlier non-linear delayed feedback model of fixational eye movements, we propose and discuss different versions of a new model that combines a self-avoiding walk with time delay. As a result, we identify a model that reproduces oscillatory correlation functions, the transition from persistence to antipersistence, and microsaccades.
Y1  - 2017
U6  - https://doi.org/10.1038/s41598-017-13489-8
SN  - 2045-2322
VL  - 7
SP  - 1
EP  - 17
PB  - Springer Nature
CY  - London
ER  - 
TY  - JOUR
A1  - Armin, Ardalan
A1  - Chen, Zhiming
A1  - Jin, Yaocheng
A1  - Zhang, Kai
A1  - Huang, Fei
A1  - Shoaee, Safa
T1  - A Shockley-Type polymer
BT  - Fullerene solar cell
JF  - Advanced energy materials
N2  - Charge extraction rate in solar cells made of blends of electron donating/accepting organic semiconductors is typically slow due to their low charge carrier mobility. This sets a limit on the active layer thickness and has hindered the industrialization of organic solar cells (OSCs). Herein, charge transport and recombination properties of an efficient polymer (NT812):fullerene blend are investigated. This system delivers power conversion efficiency of >9% even when the junction thickness is as large as 800 nm. Experimental results indicate that this material system exhibits exceptionally low bimolecular recombination constant, 800 times smaller than the diffusion-controlled electron and hole encounter rate. Comparing theoretical results based on a recently introduced modified Shockley model for fill factor, and experiments, clarifies that charge collection is nearly ideal in these solar cells even when the thickness is several hundreds of nanometer. This is the first realization of high-efficiency Shockley-type organic solar cells with junction thicknesses suitable for scaling up.
KW  - charge transport
KW  - non-Langevin recombination
KW  - organic solar cells
KW  - thick junctions
Y1  - 2018
U6  - https://doi.org/10.1002/aenm.201701450
SN  - 1614-6832
SN  - 1614-6840
VL  - 8
IS  - 7
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Pick, Leonie
A1  - Effenberger, Frederic
A1  - Zhelavskaya, Irina
A1  - Korte, Monika
T1  - A Statistical Classifier for Historical Geomagnetic Storm Drivers Derived Solely From Ground-Based Magnetic Field Measurements
JF  - Earth and Space Science
N2  - Solar wind observations show that geomagnetic storms are mainly driven by interplanetary coronal mass ejections (ICMEs) and corotating or stream interaction regions (C/SIRs). We present a binary classifier that assigns one of these drivers to 7,546 storms between 1930 and 2015 using ground‐based geomagnetic field observations only. The input data consists of the long‐term stable Hourly Magnetospheric Currents index alongside the corresponding midlatitude geomagnetic observatory time series. This data set provides comprehensive information on the global storm time magnetic disturbance field, particularly its spatial variability, over eight solar cycles. For the first time, we use this information statistically with regard to an automated storm driver identification. Our supervised classification model significantly outperforms unskilled baseline models (78% accuracy with 26[19]% misidentified interplanetary coronal mass ejections [corotating or stream interaction regions]) and delivers plausible driver occurrences with regard to storm intensity and solar cycle phase. Our results can readily be used to advance related studies fundamental to space weather research, for example, studies connecting galactic cosmic ray modulation and geomagnetic disturbances. They are fully reproducible by means of the underlying open‐source software (Pick, 2019, http://doi.org/10.5880/GFZ.2.3.2019.003)
KW  - geomagnetic observatory data
KW  - geomagnetic storm drivers
KW  - historical geomagnetic storms
KW  - supervised machine learning
Y1  - 2019
U6  - https://doi.org/10.1029/2019EA000726
SN  - 2333-5084
VL  - 6
SP  - 2000
EP  - 2015
PB  - American Geophysical Union
CY  - Malden, Mass.
ER  - 
TY  - JOUR
A1  - Kamann, Sebastian
A1  - Husser, T. -O.
A1  - Dreizler, S.
A1  - Emsellem, E.
A1  - Weilbacher, Peter Michael
A1  - Martens, S.
A1  - Bacon, R.
A1  - den Brok, M.
A1  - Giesers, B.
A1  - Krajnovic, Davor
A1  - Roth, Martin M.
A1  - Wendt, Martin
A1  - Wisotzki, Lutz
T1  - A stellar census in globular clusters with MUSE
BT  - the contribution of rotation to cluster dynamics studied with 200 000 stars
JF  - Monthly notices of the Royal Astronomical Society
N2  - This is the first of a series of papers presenting the results from our survey of 25 Galactic globular clusters with the MUSE integral-field spectrograph. In combination with our dedicated algorithm for source deblending, MUSE provides unique multiplex capabilities in crowded stellar fields and allows us to acquire samples of up to 20 000 stars within the half-light radius of each cluster. The present paper focuses on the analysis of the internal dynamics of 22 out of the 25 clusters, using about 500 000 spectra of 200 000 individual stars. Thanks to the large stellar samples per cluster, we are able to perform a detailed analysis of the central rotation and dispersion fields using both radial profiles and two-dimensional maps. The velocity dispersion profiles we derive show a good general agreement with existing radial velocity studies but typically reach closer to the cluster centres. By comparison with proper motion data, we derive or update the dynamical distance estimates to 14 clusters. Compared to previous dynamical distance estimates for 47 Tuc, our value is in much better agreement with other methods. We further find significant (>3 sigma) rotation in the majority (13/22) of our clusters. Our analysis seems to confirm earlier findings of a link between rotation and the ellipticities of globular clusters. In addition, we find a correlation between the strengths of internal rotation and the relaxation times of the clusters, suggesting that the central rotation fields are relics of the cluster formation that are gradually dissipated via two-body relaxation.
KW  - techniques: imaging spectroscopy
KW  - stars: kinematics and dynamics
KW  - globular clusters: general
Y1  - 2017
U6  - https://doi.org/10.1093/mnras/stx2719
SN  - 0035-8711
SN  - 1365-2966
VL  - 473
IS  - 4
SP  - 5591
EP  - 5616
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Göttgens, Fabian
A1  - Husser, Tim-Oliver
A1  - Kamann, Sebastian
A1  - Dreizler, Stefan
A1  - Giesers, Benjamin
A1  - Kollatschny, Wolfram
A1  - Weilbacher, Peter Michael
A1  - Roth, Martin M.
A1  - Wendt, Martin
T1  - A stellar census in globular clusters with MUSE: A spectral catalogue of emission-line sources
JF  - Astronomy and astrophysics : an international weekly journal
N2  - Aims. Globular clusters produce many exotic stars due to a much higher frequency of dynamical interactions in their dense stellar environments. Some of these objects were observed together with several hundred thousand other stars in our MUSE survey of 26 Galactic globular clusters. Assuming that at least a few exotic stars have exotic spectra (i.e. spectra that contain emission lines), we can use this large spectroscopic data set of over a million stellar spectra as a blind survey to detect stellar exotica in globular clusters. Methods. To detect emission lines in each spectrum, we modelled the expected shape of an emission line as a Gaussian curve. This template was used for matched filtering on the di fferences between each observed 1D spectrum and its fitted spectral model. The spectra with the most significant detections of H alpha emission are checked visually and cross-matched with published catalogues. Results. We find 156 stars with H alpha emission, including several known cataclysmic variables (CV) and two new CVs, pulsating variable stars, eclipsing binary stars, the optical counterpart of a known black hole, several probable sub-subgiants and red stragglers, and 21 background emission-line galaxies. We find possible optical counterparts to 39 X-ray sources, as we detected H alpha emission in several spectra of stars that are close to known positions of Chandra X-ray sources. This spectral catalogue can be used to supplement existing or future X-ray or radio observations with spectra of potential optical counterparts to classify the sources.
KW  - globular clusters: general
KW  - stars: emission-line, Be
KW  - novae
KW  - cataclysmic variables
KW  - catalogs
KW  - techniques: imaging spectroscopy
Y1  - 2019
U6  - https://doi.org/10.1051/0004-6361/201936485
SN  - 0004-6361
SN  - 1432-0746
VL  - 631
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Giesers, Benjamin David
A1  - Kamann, Sebastian
A1  - Dreizler, Stefan
A1  - Husser, Tim-Oliver
A1  - Askar, Abbas
A1  - Göttgens, Fabian
A1  - Brinchmann, Jarle
A1  - Latour, Marilyn
A1  - Weilbacher, Peter Michael
A1  - Wendt, Martin
A1  - Roth, Martin M.
T1  - A stellar census in globular clusters with MUSE: Binaries in NGC 3201
JF  - Astronomy and astrophysics : an international weekly journal
N2  - We utilise multi-epoch MUSE spectroscopy to study binary stars in the core of the Galactic globular cluster NGC 3201. Our sample consists of 3553 stars with 54 883 spectra in total comprising 3200 main-sequence stars up to 4 magnitudes below the turn-off. Each star in our sample has between 3 and 63 (with a median of 14) reliable radial velocity measurements within five years of observations. We introduce a statistical method to determine the probability of a star showing radial velocity variations based on the whole inhomogeneous radial velocity sample. Using HST photometry and an advanced dynamical MOCCA simulation of this specific cluster we overcome observational biases that previous spectroscopic studies had to deal with. This allows us to infer a binary frequency in the MUSE field of view and enables us to deduce the underlying true binary frequency of (6.75 +/- 0.72)% in NGC 3201. The comparison of the MUSE observations with the MOCCA simulation suggests a large portion of primordial binaries. We can also confirm a radial increase in the binary fraction towards the cluster centre due to mass segregation. We discovered that in the core of NGC 3201 at least (57.5 +/- 7.9)% of blue straggler stars are in a binary system. For the first time in a study of globular clusters, we were able to fit Keplerian orbits to a significant sample of 95 binaries. We present the binary system properties of eleven blue straggler stars and the connection to SX Phoenicis-type stars. We show evidence that two blue straggler formation scenarios, the mass transfer in binary (or triple) star systems and the coalescence due to binary-binary interactions, are present in our data. We also describe the binary and spectroscopic properties of four sub-subgiant (or red straggler) stars. Furthermore, we discovered two new black hole candidates with minimum masses (M sin i) of (7.68 +/- 0.50)M-circle dot, (4.4 +/- 2.8)M-circle dot, and refine the minimum mass estimate on the already published black hole to (4.53 +/- 0.21)M-circle dot, These black holes are consistent with an extensive black hole subsystem hosted by NGC 3201.
KW  - binaries: general
KW  - blue stragglers
KW  - stars: black holes
KW  - techniques: radial velocities
KW  - techniques: imaging spectroscopy
KW  - globular clusters: individual: NGC 3201
Y1  - 2019
U6  - https://doi.org/10.1051/0004-6361/201936203
SN  - 0004-6361
SN  - 1432-0746
VL  - 632
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Latour, Marlyn
A1  - Husser, Tim Oliver
A1  - Giesers, Benjamin David
A1  - Kamann, S.
A1  - Göttgens, Fabian
A1  - Dreizler, Stefan
A1  - Brinchmann, Jan
A1  - Bastian, Nate
A1  - Wendt, Martin
A1  - Weilbacher, Peter Michael
A1  - Molinski, N. S.
T1  - A stellar census in globular clusters with MUSE: multiple populations chemistry in NGC 2808 star star star
JF  - Astronomy and astrophysics : an international weekly journal
N2  - Context. Galactic globular clusters (GCs) are now known to host multiple populations displaying particular abundance variations. The different populations within a GC can be well distinguished following their position in the pseudo two-colors diagrams, also referred to as "chromosome maps". These maps are constructed using optical and near-UV photometry available from the Hubble Space Telescope (HST) UV survey of GCs. However, the chemical tagging of the various populations in the chromosome maps is hampered by the fact that HST photometry and elemental abundances are both only available for a limited number of stars. Aims. The spectra collected as part of the MUSE survey of globular clusters provide a spectroscopic counterpart to the HST photometric catalogs covering the central regions of GCs. In this paper, we use the MUSE spectra of 1115 red giant branch (RGB) stars in NGC 2808 to characterize the abundance variations seen in the multiple populations of this cluster. Methods. We used the chromosome map of NGC 2808 to divide the RGB stars into their respective populations. We then combined the spectra of all stars belonging to a given population, resulting in one high signal-to-noise ratio spectrum representative of each population. Results. Variations in the spectral lines of O, Na, Mg, and Al are clearly detected among four of the populations. In order to quantify these variations, we measured equivalent width differences and created synthetic populations spectra that were used to determine abundance variations with respect to the primordial population of the cluster. Our results are in good agreement with the values expected from previous studies based on high-resolution spectroscopy. We do not see any significant variations in the spectral lines of Ca, K, and Ba. We also do not detect abundance variations among the stars belonging to the primordial population of NGC 2808. Conclusions. We demonstrate that in spite of their low resolution, the MUSE spectra can be used to investigate abundance variations in the context of multiple populations.
KW  - techniques: imaging spectroscopy
KW  - stars: abundances
KW  - globular clusters: individual: NGC 2808
Y1  - 2019
U6  - https://doi.org/10.1051/0004-6361/201936242
SN  - 1432-0746
VL  - 631
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Abeysekara, A. U.
A1  - Archer, A.
A1  - Benbow, Wystan
A1  - Bird, Ralph
A1  - Brose, Robert
A1  - Buchovecky, M.
A1  - Bugaev, V.
A1  - Connolly, M. P.
A1  - Cui, Wei
A1  - Errando, Manel
A1  - Falcone, A.
A1  - Feng, Qi
A1  - Finley, John P.
A1  - Flinders, A.
A1  - Fortson, L.
A1  - Furniss, Amy
A1  - Gillanders, Gerard H.
A1  - Huetten, M.
A1  - Hanna, David
A1  - Hervet, O.
A1  - Holder, J.
A1  - Hughes, G.
A1  - Humensky, T. B.
A1  - Johnson, Caitlin A.
A1  - Kaaret, Philip
A1  - Kar, P.
A1  - Kelley-Hoskins, N.
A1  - Kertzman, M.
A1  - Kieda, David
A1  - Krause, Maria
A1  - Krennrich, F.
A1  - Lang, M. J.
A1  - Lin, T. T. Y.
A1  - Maier, Gernot
A1  - McArthur, S.
A1  - Moriarty, P.
A1  - Mukherjee, Reshmi
A1  - Ong, R. A.
A1  - Park, N.
A1  - Perkins, Jeremy S.
A1  - Petrashyk, A.
A1  - Pohl, Martin
A1  - Popkow, Alexis
A1  - Pueschel, Elisa
A1  - Quinn, J.
A1  - Ragan, K.
A1  - Reynolds, P. T.
A1  - Richards, Gregory T.
A1  - Roache, E.
A1  - Rulten, C.
A1  - Sadeh, I.
A1  - Santander, M.
A1  - Sembroski, G. H.
A1  - Shahinyan, Karlen
A1  - Tyler, J.
A1  - Wakely, S. P.
A1  - Weiner, O. M.
A1  - Weinstein, A.
A1  - Wells, R. M.
A1  - Wilcox, P.
A1  - Wilhelm, Alina
A1  - Williams, David A.
A1  - Zitzer, B.
A1  - Vurm, Indrek
A1  - Beloborodov, Andrei
T1  - A Strong Limit on the Very-high-energy Emission from GRB 150323A
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - On 2015 March 23, the Very Energetic Radiation Imaging Telescope Array System (VERITAS) responded to a Swift-Burst Alert Telescope (BAT) detection of a gamma-ray burst, with observations beginning 270 s after the onset of BAT emission, and only 135 s after the main BAT emission peak. No statistically significant signal is detected above 140 GeV. The VERITAS upper limit on the fluence in a 40-minute integration corresponds to about 1% of the prompt fluence. Our limit is particularly significant because the very-high-energy (VHE) observation started only similar to 2 minutes after the prompt emission peaked, and Fermi-Large Area Telescope observations of numerous other bursts have revealed that the high-energy emission is typically delayed relative to the prompt radiation and lasts significantly longer. Also, the proximity of GRB 150323A (z = 0.593) limits the attenuation by the extragalactic background light to similar to 50% at 100-200 GeV. We conclude that GRB 150323A had an intrinsically very weak high-energy afterglow, or that the GeV spectrum had a turnover below similar to 100 GeV. If the GRB exploded into the stellar wind of a massive progenitor, the VHE non-detection constrains the wind density parameter to be A greater than or similar to 3 x 10(11) g . cm(-1), consistent with a standard Wolf-Rayet progenitor. Alternatively, the VHE emission from the blast wave would be weak in a very tenuous medium such as the interstellar medium, which therefore cannot be ruled out as the environment of GRB 150323A.
KW  - gamma rays: general
KW  - gamma-ray burst: general
KW  - gamma-ray burst: individual (GRB 150323A)
Y1  - 2018
U6  - https://doi.org/10.3847/1538-4357/aab371
SN  - 0004-637X
SN  - 1538-4357
VL  - 857
IS  - 1
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Rodríguez Zuluaga, Juan
A1  - Stolle, Claudia
A1  - Yamazaki, Yosuke
A1  - Xiong, Chao
A1  - England, Scott L.
T1  - A synoptic-scale wavelike structure in the nighttime equatorial ionization anomaly
JF  - Earth and Space Science : ESS
N2  - Both ground- and satellite-based airglow imaging have significantly contributed to understanding the low-latitude ionosphere, especially the morphology and dynamics of the equatorial ionization anomaly (EIA). The NASA Global-scale Observations of the Limb and Disk (GOLD) mission focuses on far-ultraviolet airglow images from a geostationary orbit at 47.5 degrees W. This region is of particular interest at low magnetic latitudes because of the high magnetic declination (i.e., about -20 degrees) and proximity of the South Atlantic magnetic anomaly. In this study, we characterize an exciting feature of the nighttime EIA using GOLD observations from October 5, 2018 to June 30, 2020. It consists of a wavelike structure of a few thousand kilometers seen as poleward and equatorward displacements of the EIA-crests. Initial analyses show that the synoptic-scale structure is symmetric about the dip equator and appears nearly stationary with time over the night. In quasi-dipole coordinates, maxima poleward displacements of the EIA-crests are seen at about +/- 12 degrees latitude and around 20 and 60 degrees longitude (i.e., in geographic longitude at the dip equator, about 53 degrees W and 14 degrees W). The wavelike structure presents typical zonal wavelengths of about 6.7 x 10(3) km and 3.3 x 10(3) km. The structure's occurrence and wavelength are highly variable on a day-to-day basis with no apparent dependence on geomagnetic activity. In addition, a cluster or quasi-periodic wave train of equatorial plasma depletions (EPDs) is often detected within the synoptic-scale structure. We further outline the difference in observing these EPDs from FUV images and in situ measurements during a GOLD and Swarm mission conjunction.
KW  - equatorial ionization anomaly
KW  - equatorial ionosphere
KW  - equatorial plasma bubbles
KW  - wave structure
KW  - forcing from below
Y1  - 2021
U6  - https://doi.org/10.1029/2020EA001529
SN  - 2333-5084
VL  - 8
IS  - 2
PB  - American Geophysical Union
CY  - Malden, Mass.
ER  - 
TY  - JOUR
A1  - Myhre, Rolf H.
A1  - Wolf, Thomas J. A.
A1  - Cheng, Lan
A1  - Nandi, Saikat
A1  - Coriani, Sonia
A1  - Gühr, Markus
A1  - Koch, Henrik
T1  - A theoretical and experimental benchmark study of core-excited states in nitrogen
JF  - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr
N2  - The high resolution near edge X-ray absorption fine structure spectrum of nitrogen displays the vibrational structure of the core-excited states. This makes nitrogen well suited for assessing the accuracy of different electronic structure methods for core excitations. We report high resolution experimental measurements performed at the SOLEIL synchrotron facility. These are compared with theoretical spectra calculated using coupled cluster theory and algebraic diagrammatic construction theory. The coupled cluster singles and doubles with perturbative triples model known as CC3 is shown to accurately reproduce the experimental excitation energies as well as the spacing of the vibrational transitions. The computational results are also shown to be systematically improved within the coupled cluster hierarchy, with the coupled cluster singles, doubles, triples, and quadruples method faithfully reproducing the experimental vibrational structure. Published by AIP Publishing.
Y1  - 2018
U6  - https://doi.org/10.1063/1.5011148
SN  - 0021-9606
SN  - 1089-7690
VL  - 148
IS  - 6
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - JOUR
A1  - Fischer, Eric W.
A1  - Saalfrank, Peter
T1  - A thermofield-based multilayer multiconfigurational time-dependent Hartree approach to non-adiabatic quantum dynamics at finite temperature
JF  - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistry
N2  - We introduce a thermofield-based formulation of the multilayer multiconfigurational time-dependent Hartree (MCTDH) method to study finite temperature effects on non-adiabatic quantum dynamics from a non-stochastic, wave function perspective. Our approach is based on the formal equivalence of bosonic many-body theory at zero temperature with a doubled number of degrees of freedom and the thermal quasi-particle representation of bosonic thermofield dynamics (TFD). This equivalence allows for a transfer of bosonic many-body MCTDH as introduced by Wang and Thoss to the finite temperature framework of thermal quasi-particle TFD. As an application, we study temperature effects on the ultrafast internal conversion dynamics in pyrazine. We show that finite temperature effects can be efficiently accounted for in the construction of multilayer expansions of thermofield states in the framework presented herein. Furthermore, we find our results to agree well with existing studies on the pyrazine model based on the pMCTDH method.
Y1  - 2021
U6  - https://doi.org/10.1063/5.0064013
SN  - 0021-9606
SN  - 1089-7690
VL  - 155
IS  - 13
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - JOUR
A1  - Battistoni, A.
A1  - Dürr, H. A.
A1  - Gühr, Markus
A1  - Wolf, Thomas J. A.
T1  - A tilted pulse-front setup for femtosecond transient grating spectroscopy in highly non-collinear geometries
JF  - Journal of optics
N2  - We demonstrate a tilted pulse-front transient grating (TG) technique that allows to optimally utilize time resolution as well as TG line density while probing under grazing incidence as typically done in extreme ultraviolet (EUV) or soft x-ray (SXR) experiments. Our optical setup adapts the pulse front tilt of the two pulses that create the TG to the grazing incident pulse. We demonstrate the technique using all 800 nm femtosecond laser pulses for TG generation on a vanadium dioxide film. We probe that grating via diffraction of a third 800 nm pulse. The time resolution of 90 fs is an improvement by a factor of 30 compared to our previous experiments on the same system. The scheme paves the way for EUV and SXR probing of optically induced TGs on any material.
KW  - transient grating spectroscopy
KW  - ultrafast spectroscopy
KW  - pulse front matching
Y1  - 2018
U6  - https://doi.org/10.1088/2040-8986/aad60a
SN  - 2040-8978
SN  - 2040-8986
VL  - 20
IS  - 9
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Abeysekara, A. U.
A1  - Archer, A.
A1  - Aune, Taylor
A1  - Benbow, Wystan
A1  - Bird, Ralph
A1  - Brose, Robert
A1  - Buchovecky, M.
A1  - Bugaev, V.
A1  - Cui, Wei
A1  - Daniel, M. K.
A1  - Falcone, A.
A1  - Feng, Qi
A1  - Finley, John P.
A1  - Fleischhack, H.
A1  - Flinders, A.
A1  - Fortson, L.
A1  - Furniss, Amy
A1  - Gotthelf, Eric V.
A1  - Grube, J.
A1  - Hanna, David
A1  - Hervet, O.
A1  - Holder, J.
A1  - Huang, K.
A1  - Hughes, G.
A1  - Humensky, T. B.
A1  - Huetten, M.
A1  - Johnson, Caitlin A.
A1  - Kaaret, Philip
A1  - Kar, P.
A1  - Kelley-Hoskins, N.
A1  - Kertzman, M.
A1  - Kieda, David
A1  - Krause, Maria
A1  - Kumar, S.
A1  - Lang, M. J.
A1  - Lin, T. T. Y.
A1  - Maier, Gernot
A1  - McArthur, S.
A1  - Moriarty, P.
A1  - Mukherjee, Reshmi
A1  - Ong, R. A.
A1  - Otte, Adam Nepomuk
A1  - Pandel, Dirk
A1  - Park, Nahee
A1  - Petrashyk, A.
A1  - Pohl, Martin
A1  - Popkow, Alexis
A1  - Pueschel, Elisa
A1  - Quinn, J.
A1  - Ragan, K.
A1  - Reynolds, P. T.
A1  - Richards, Gregory T.
A1  - Roache, E.
A1  - Rousselle, J.
A1  - Rulten, C.
A1  - Sadeh, I.
A1  - Santander, M.
A1  - Sembroski, G. H.
A1  - Shahinyan, Karlen
A1  - Tyler, J.
A1  - Vassiliev, V. V.
A1  - Wakely, S. P.
A1  - Ward, J. E.
A1  - Weinstein, A.
A1  - Wells, R. M.
A1  - Wilcox, P.
A1  - Wilhelm, Alina
A1  - Williams, David A.
A1  - Zitzer, B.
T1  - A Very High Energy gamma-Ray Survey toward the Cygnus Region of the Galaxy
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - We present results from deep observations toward the Cygnus region using 300 hr of very high energy (VHE)gamma-ray data taken with the VERITAS Cerenkov telescope array and over 7 yr of high-energy.-ray data taken with the Fermi satellite at an energy above 1 GeV. As the brightest region of diffuse gamma-ray emission in the northern sky, the Cygnus region provides a promising area to probe the origins of cosmic rays. We report the identification of a potential Fermi-LAT counterpart to VER J2031+415 (TeV J2032+4130) and resolve the extended VHE source VER J2019+368 into two source candidates (VER J2018+367* and VER J2020+368*) and characterize their energy spectra. The Fermi-LAT morphology of 3FGL J2021.0+4031e (the Gamma Cygni supernova remnant) was examined, and a region of enhanced emission coincident with VER J2019+407 was identified and jointly fit with the VERITAS data. By modeling 3FGL J2015.6+3709 as two sources, one located at the location of the pulsar wind nebula CTB 87 and one at the quasar QSO J2015+371, a continuous spectrum from 1 GeV to 10 TeV was extracted for VER J2016+371 (CTB 87). An additional 71 locations coincident with Fermi-LAT sources and other potential objects of interest were tested for VHE gamma-ray emission, with no emission detected and upper limits on the differential flux placed at an average of 2.3% of the Crab Nebula flux. We interpret these observations in a multiwavelength context and present the most detailed gamma-ray view of the region to date.
KW  - acceleration of particles
KW  - cosmic rays
KW  - gamma rays: general
KW  - ISM: supernova remnants
Y1  - 2018
U6  - https://doi.org/10.3847/1538-4357/aac4a2
SN  - 0004-637X
SN  - 1538-4357
VL  - 861
IS  - 2
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Abdalla, Hassan E.
A1  - Adam, R.
A1  - Aharonian, Felix A.
A1  - Benkhali, F. Ait
A1  - Angüner, Ekrem Oǧuzhan
A1  - Arakawa, M.
A1  - Arcaro, C.
A1  - Armand, C.
A1  - Ashkar, H.
A1  - Backes, M.
A1  - Martins, V. Barbosa
A1  - Barnard, M.
A1  - Becherini, Y.
A1  - Berge, D.
A1  - Bernloehr, K.
A1  - Bissaldi, E.
A1  - Blackwell, R.
A1  - Boettcher, M.
A1  - Boisson, C.
A1  - Bolmont, J.
A1  - Bonnefoy, S.
A1  - Bregeon, J.
A1  - Breuhaus, M.
A1  - Brun, F.
A1  - Brun, P.
A1  - Bryan, M.
A1  - Buechele, M.
A1  - Bulik, T.
A1  - Bylund, T.
A1  - Capasso, M.
A1  - Caroff, S.
A1  - Carosi, A.
A1  - Casanova, Sabrina
A1  - Cerruti, M.
A1  - Chand, T.
A1  - Chandra, S.
A1  - Chen, A.
A1  - Colafrancesco, S.
A1  - Curylo, M.
A1  - Davids, I. D.
A1  - Deil, C.
A1  - Devin, J.
A1  - deWilt, P.
A1  - Dirson, L.
A1  - Djannati-Atai, A.
A1  - Dmytriiev, A.
A1  - Donath, A.
A1  - Doroshenko, V
A1  - Dyks, J.
A1  - Egberts, Kathrin
A1  - Emery, G.
A1  - Ernenwein, J-P
A1  - Eschbach, S.
A1  - Feijen, K.
A1  - Fegan, S.
A1  - Fiasson, A.
A1  - Fontaine, G.
A1  - Funk, S.
A1  - Fussling, Matthias
A1  - Gabici, S.
A1  - Gallant, Y. A.
A1  - Gate, F.
A1  - Giavitto, G.
A1  - Giunti, L.
A1  - Glawion, D.
A1  - Glicenstein, J. F.
A1  - Gottschall, D.
A1  - Grondin, M-H
A1  - Hahn, J.
A1  - Haupt, M.
A1  - Heinzelmann, G.
A1  - Henri, G.
A1  - Hermann, G.
A1  - Hinton, J. A.
A1  - Hofmann, W.
A1  - Hoischen, Clemens
A1  - Holch, T. L.
A1  - Holler, M.
A1  - Horns, D.
A1  - Huber, D.
A1  - Iwasaki, H.
A1  - Jamrozy, M.
A1  - Jankowsky, D.
A1  - Jankowsky, F.
A1  - Jardin-Blicq, A.
A1  - Jung-Richardt, I
A1  - Kastendieck, M. A.
A1  - Katarzynski, K.
A1  - Katsuragawa, M.
A1  - Katz, U.
A1  - Khangulyan, D.
A1  - Khelifi, B.
A1  - King, J.
A1  - Klepser, S.
A1  - Kluzniak, W.
A1  - Komin, Nu
A1  - Kosack, K.
A1  - Kostunin, D.
A1  - Kreter, M.
A1  - Lamanna, G.
A1  - Lemiere, A.
A1  - Lemoine-Goumard, M.
A1  - Lenain, J-P
A1  - Leser, Eva
A1  - Levy, C.
A1  - Lohse, T.
A1  - Lypova, I
A1  - Mackey, J.
A1  - Majumdar, J.
A1  - Malyshev, D.
A1  - Marandon, V
A1  - Marcowith, Alexandre
A1  - Mares, A.
A1  - Mariaud, C.
A1  - Marti-Devesa, G.
A1  - Marx, R.
A1  - Maurin, G.
A1  - Meintjes, P. J.
A1  - Mitchell, A. M. W.
A1  - Moderski, R.
A1  - Mohamed, M.
A1  - Mohrmann, L.
A1  - Moore, C.
A1  - Moulin, Emmanuel
A1  - Muller, J.
A1  - Murach, T.
A1  - Nakashima, S.
A1  - de Naurois, M.
A1  - Ndiyavala, H.
A1  - Niederwanger, F.
A1  - Niemiec, J.
A1  - Oakes, L.
A1  - Odaka, H.
A1  - Ohm, S.
A1  - Wilhelmi, E. de Ona
A1  - Ostrowski, M.
A1  - Oya, I
A1  - Panter, M.
A1  - Parsons, R. D.
A1  - Perennes, C.
A1  - Petrucci, P-O
A1  - Peyaud, B.
A1  - Piel, Q.
A1  - Pita, S.
A1  - Poireau, V
A1  - Noel, A. Priyana
A1  - Prokhorov, D. A.
A1  - Prokoph, H.
A1  - Puehlhofer, G.
A1  - Punch, M.
A1  - Quirrenbach, A.
A1  - Raab, S.
A1  - Rauth, R.
A1  - Reimer, A.
A1  - Reimer, O.
A1  - Remy, Q.
A1  - Renaud, M.
A1  - Rieger, F.
A1  - Rinchiuso, L.
A1  - Romoli, C.
A1  - Rowell, G.
A1  - Rudak, B.
A1  - Ruiz-Velasco, E.
A1  - Sahakian, V
A1  - Sailer, S.
A1  - Saito, S.
A1  - Sanchez, D. A.
A1  - Santangelo, Andrea
A1  - Sasaki, M.
A1  - Schlickeiser, R.
A1  - Schussler, F.
A1  - Schulz, A.
A1  - Schutte, H. M.
A1  - Schwanke, U.
A1  - Schwemmer, S.
A1  - Seglar-Arroyo, M.
A1  - Senniappan, M.
A1  - Seyffert, A. S.
A1  - Shafi, N.
A1  - Shiningayamwe, K.
A1  - Simoni, R.
A1  - Sinha, A.
A1  - Sol, H.
A1  - Specovius, A.
A1  - Spir-Jacob, M.
A1  - Stawarz, L.
A1  - Steenkamp, R.
A1  - Stegmann, Christian
A1  - Steppa, Constantin Beverly
A1  - Takahashi, T.
A1  - Tavernier, T.
A1  - Taylor, A. M.
A1  - Terrier, R.
A1  - Tiziani, D.
A1  - Tluczykont, M.
A1  - Trichard, C.
A1  - Tsirou, M.
A1  - Tsuji, N.
A1  - Tuffs, R.
A1  - Uchiyama, Y.
A1  - van der Walt, D. J.
A1  - van Eldik, C.
A1  - van Rensburg, C.
A1  - van Soelen, B.
A1  - Vasileiadis, G.
A1  - Veh, J.
A1  - Venter, C.
A1  - Vincent, P.
A1  - Vink, J.
A1  - Voelk, H. J.
A1  - Vuillaume, T.
A1  - Wadiasingh, Z.
A1  - Wagner, S. J.
A1  - White, R.
A1  - Wierzcholska, A.
A1  - Yang, R.
A1  - Yoneda, H.
A1  - Zacharias, M.
A1  - Zanin, R.
A1  - Zdziarski, A. A.
A1  - Zech, Alraune
A1  - Ziegler, A.
A1  - Zorn, J.
A1  - Zywucka, N.
A1  - de Palma, F.
A1  - Axelsson, M.
A1  - Roberts, O. J.
T1  - A very-high-energy component deep in the gamma-ray burst afterglow
JF  - Nature : the international weekly journal of science
N2  - Gamma-ray bursts (GRBs) are brief flashes of gamma-rays and are considered to be the most energetic explosive phenomena in the Universe(1). The emission from GRBs comprises a short (typically tens of seconds) and bright prompt emission, followed by a much longer afterglow phase. During the afterglow phase, the shocked outflow-produced by the interaction between the ejected matter and the circumburst medium-slows down, and a gradual decrease in brightness is observed(2). GRBs typically emit most of their energy via.-rays with energies in the kiloelectronvolt-to-megaelectronvolt range, but a few photons with energies of tens of gigaelectronvolts have been detected by space-based instruments(3). However, the origins of such high-energy (above one gigaelectronvolt) photons and the presence of very-high-energy (more than 100 gigaelectronvolts) emission have remained elusive(4). Here we report observations of very-high-energy emission in the bright GRB 180720B deep in the GRB afterglow-ten hours after the end of the prompt emission phase, when the X-ray flux had already decayed by four orders of magnitude. Two possible explanations exist for the observed radiation: inverse Compton emission and synchrotron emission of ultrarelativistic electrons. Our observations show that the energy fluxes in the X-ray and gamma-ray range and their photon indices remain comparable to each other throughout the afterglow. This discovery places distinct constraints on the GRB environment for both emission mechanisms, with the inverse Compton explanation alleviating the particle energy requirements for the emission observed at late times. The late timing of this detection has consequences for the future observations of GRBs at the highest energies.
Y1  - 2019
U6  - https://doi.org/10.1038/s41586-019-1743-9
SN  - 0028-0836
SN  - 1476-4687
VL  - 575
IS  - 7783
SP  - 464
EP  - +
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Norell, Jesper
A1  - Eckert, Sebastian
A1  - Van Kuiken, Benjamin E.
A1  - Föhlisch, Alexander
A1  - Odelius, Michael
T1  - Ab initio simulations of complementary K-edges and solvatization effects for detection of proton transfer in aqueous 2-thiopyridone
JF  - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr
N2  - The nitrogen and sulfur K-edge X-ray absorption spectra of aqueous 2-thiopyridone, a model system for excited-state proton transfer in several recent time-resolved measurements, have been simulated from ab initio molecular dynamics. Spectral signatures of the local intra- and inter-molecular structure are identified and rationalized, which facilitates experimental interpretation and optimization. In particular, comparison of aqueous and gas phase spectrum simulations assesses the previously unquantified solvatization effects, where hydrogen bonding is found to yield solvatochromatic shifts up to nearly 1 eV of the main peak positions. Thereby, while each K-edge can still decisively determine the local protonation of its core-excited site, only their combined, complementary fingerprints allow separating all of the three relevant molecular forms, giving a complete picture of the proton transfer.
Y1  - 2019
U6  - https://doi.org/10.1063/1.5109840
SN  - 0021-9606
SN  - 1089-7690
VL  - 151
IS  - 11
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - JOUR
A1  - Sajedi, Maryam
A1  - Krivenkov, Maxim
A1  - Marchenko, Dmitry
A1  - Varykhalov, Andrei
A1  - Sanchez-Barriga, Jaime
A1  - Rienks, Emile D. L.
A1  - Rader, Oliver
T1  - Absence of a giant Rashba effect in the valence band of lead halide perovskites
JF  - Physical review : B, Condensed matter and materials physics
N2  - For hybrid organic-inorganic as well as all-inorganic lead halide perovskites a Rashba effect has been invoked to explain the high efficiency in energy conversion by prohibiting direct recombination. Both a bulk and surface Rashba effect have been predicted. In the valence band of methylammonium (MA) lead bromide a Rashba effect has been reported by angle-resolved photoemission and circular dichroism with giant values of 7-11 eV angstrom. We present band dispersion measurements of MAPbBr(3) and spin-resolved photoemission of CsPbBr3 to show that a large Rashba effect detectable by photoemission or circular dichroism does not exist and cannot be the origin of the high effciency.
Y1  - 2020
U6  - https://doi.org/10.1103/PhysRevB.102.081116
SN  - 2469-9950
SN  - 2469-9969
VL  - 102
IS  - 8
PB  - American Institute of Physics; American Physical Society (APS)
CY  - Woodbury, NY
ER  - 
TY  - JOUR
A1  - Guggenberger, Tobias
A1  - Chechkin, Aleksei
A1  - Metzler, Ralf
T1  - Absence of stationary states and non-Boltzmann distributions of fractional Brownian motion in shallow external potentials
JF  - New journal of physics : the open-access journal for physics
N2  - We study the diffusive motion of a particle in a subharmonic potential of the form U(x) = |x|( c ) (0 < c < 2) driven by long-range correlated, stationary fractional Gaussian noise xi ( alpha )(t) with 0 < alpha <= 2. In the absence of the potential the particle exhibits free fractional Brownian motion with anomalous diffusion exponent alpha. While for an harmonic external potential the dynamics converges to a Gaussian stationary state, from extensive numerical analysis we here demonstrate that stationary states for shallower than harmonic potentials exist only as long as the relation c > 2(1 - 1/alpha) holds. We analyse the motion in terms of the mean squared displacement and (when it exists) the stationary probability density function. Moreover we discuss analogies of non-stationarity of Levy flights in shallow external potentials.
KW  - diffusion
KW  - Boltzmann distribution
KW  - fractional Brownian motion
Y1  - 2022
U6  - https://doi.org/10.1088/1367-2630/ac7b3c
SN  - 1367-2630
VL  - 24
IS  - 7
PB  - Dt. Physikalische Ges.
CY  - [Bad Honnef]
ER  - 
TY  - JOUR
A1  - Vandewal, Koen
A1  - Benduhn, Johannes
A1  - Schellhammer, Karl Sebastian
A1  - Vangerven, Tim
A1  - Rückert, Janna E.
A1  - Piersimoni, Fortunato
A1  - Scholz, Reinhard
A1  - Zeika, Olaf
A1  - Fan, Yeli
A1  - Barlow, Stephen
A1  - Neher, Dieter
A1  - Marder, Seth R.
A1  - Manca, Jean
A1  - Spoltore, Donato
A1  - Cuniberti, Gianaurelio
A1  - Ortmann, Frank
T1  - Absorption Tails of Donor
BT  - C-60 Blends Provide Insight into Thermally Activated Charge-Transfer Processes and Polaron Relaxation
JF  - Journal of the American Chemical Society
N2  - In disordered organic semiconductors, the transfer of a rather localized charge carrier from one site to another triggers a deformation of the molecular structure quantified by the intramolecular relaxation energy. A similar structural relaxation occurs upon population of intermolecular charge-transfer (CT) states formed at organic electron donor (D)-acceptor (A) interfaces. Weak CT absorption bands for D A complexes occur at photon energies below the optical gaps of both the donors and the C-60 acceptor as a result of optical transitions from the neutral ground state to the ionic CT state. In this work, we show that temperature-activated intramolecular vibrations of the ground state play a major role in determining the line shape of such CT absorption bands. This allows us to extract values for the relaxation energy related to the geometry change from neutral to ionic CT complexes. Experimental values for the relaxation energies of 20 D:C-60 CT complexes correlate with values calculated within density functional theory. These results provide an experimental method for determining the polaron relaxation energy in solid-state organic D-A blends and show the importance of a reduced relaxation energy, which we introduce to characterize thermally activated CT processes.
Y1  - 2017
U6  - https://doi.org/10.1021/jacs.6b12857
SN  - 0002-7863
VL  - 139
IS  - 4
SP  - 1699
EP  - 1704
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Willner, Sven N.
A1  - Levermann, Anders
A1  - Zhao, Fang
A1  - Frieler, Katja
T1  - Adaptation required to preserve future high-end river flood risk at present levels
JF  - Science Advances
N2  - Earth’s surface temperature will continue to rise for another 20 to 30 years even with the strongest carbon emission reduction currently considered. The associated changes in rainfall patterns can result in an increased flood risk worldwide. We compute the required increase in flood protection to keep high-end fluvial flood risk at present levels. The analysis is carried out worldwide for subnational administrative units. Most of the United States, Central Europe, and Northeast and West Africa, as well as large parts of India and Indonesia, require the strongest adaptation effort. More than half of the United States needs to at least double their protection within the next two decades. Thus, the need for adaptation to increased river flood is a global problem affecting industrialized regions as much as developing countries.
Y1  - 2018
U6  - https://doi.org/10.1126/sciadv.aao1914
SN  - 2375-2548
VL  - 4
IS  - 1
PB  - American Assoc. for the Advancement of Science
CY  - Washington
ER  - 
TY  - JOUR
A1  - Anielski, Alexander
A1  - Barbosa Pfannes, Eva Katharina
A1  - Beta, Carsten
T1  - Adaptive microfluidic gradient generator for quantitative chemotaxis experiments
JF  - Review of scientific instruments : a monthly journal devoted to scientific instruments, apparatus, and techniques
N2  - Chemotactic motion in a chemical gradient is an essential cellular function that controls many processes in the living world. For a better understanding and more detailed modelling of the underlying mechanisms of chemotaxis, quantitative investigations in controlled environments are needed. We developed a setup that allows us to separately address the dependencies of the chemotactic motion on the average background concentration and on the gradient steepness of the chemoattractant. In particular, both the background concentration and the gradient steepness can be kept constant at the position of the cell while it moves along in the gradient direction. This is achieved by generating a well-defined chemoattractant gradient using flow photolysis. In this approach, the chemoattractant is released by a light-induced reaction from a caged precursor in a microfluidic flow chamber upstream of the cell. The flow photolysis approach is combined with an automated real-time cell tracker that determines changes in the cell position and triggers movement of the microscope stage such that the cell motion is compensated and the cell remains at the same position in the gradient profile. The gradient profile can be either determined experimentally using a caged fluorescent dye or may be alternatively determined by numerical solutions of the corresponding physical model. To demonstrate the function of this adaptive microfluidic gradient generator, we compare the chemotactic motion of Dictyostelium discoideum cells in a static gradient and in a gradient that adapts to the position of the moving cell. Published by AIP Publishing.
Y1  - 2017
U6  - https://doi.org/10.1063/1.4978535
SN  - 0034-6748
SN  - 1089-7623
VL  - 88
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - JOUR
A1  - Umlandt, Maren
A1  - Feldmann, David
A1  - Schneck, Emanuel
A1  - Santer, Svetlana
A1  - Bekir, Marek
T1  - Adsorption of photoresponsive surfactants at solid-liquid interfaces
JF  - Langmuir
N2  - We report on the adsorption kinetics of azoben-zene-containing surfactants on solid surfaces of different hydrophobicity. The understanding of this processes is of great importance for many interfacial phenomena that can be actuated and triggered by light, since the surfactant molecules contain a photoresponsive azobenzene group in their hydrophobic tail. Three surfactant types are studied, differing in the spacer connecting the headgroup and the azobenzene unit by between 6 and 10 CH2 groups. Under irradiation with light of a suitable wavelength, the azobenzene undergoes reversible photoisomerization between two states, a nonpolar trans-state and a highly polar cis-state. Consequently, the surfactant molecule changes its hydrophobicity and thus affinity to a surface depending on the photoisomerization state of the azobenzene. The adsorption behavior on hydrophilic (glass) and hydrophobic (TeflonAF) surfaces is analyzed using quartz crystal microbalance with dissipation (QCM-D) and zeta-potential measurements. At equilibrium, the adsorbed surfactant amount is almost twice as large on glass compared to TeflonAF for both isomers. The adsorption rate for the trans-isomers on both surfaces is similar, but the desorption rate of the trans-isomers is faster at the glass-water interface than at the Teflon-water interface. This result demonstrates that the trans-isomers have higher affinity for the glass surface, so the trans-to-cis ratios on glass and TeflonAF are 80/1 and 2/1, respectively, with similar trends for all three surfactant types.
Y1  - 2020
U6  - https://doi.org/10.1021/acs.langmuir.0c02545
SN  - 0743-7463
SN  - 1520-5827
VL  - 36
IS  - 46
SP  - 14009
EP  - 14018
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Evsevleev, Sergei
A1  - Paciornik, Sidnei
A1  - Bruno, Giovanni
T1  - Advanced deep learning-based 3D microstructural characterization of multiphase metal matrix composites
JF  - Advanced engineering materials
N2  - The quantitative analysis of microstructural features is a key to understanding the micromechanical behavior of metal matrix composites (MMCs), which is a premise for their use in practice. Herein, a 3D microstructural characterization of a five-phase MMC is performed by synchrotron X-ray computed tomography (SXCT). A workflow for advanced deep learning-based segmentation of all individual phases in SXCT data is shown using a fully convolutional neural network with U-net architecture. High segmentation accuracy is achieved with a small amount of training data. This enables extracting unprecedently precise microstructural parameters (e.g., volume fractions and particle shapes) to be input, e.g., in micromechanical models.
KW  - computed tomography
KW  - convolutional neural networks
KW  - deep learning
KW  - metal
KW  - matrix composites
KW  - segmentations
Y1  - 2020
U6  - https://doi.org/10.1002/adem.201901197
SN  - 1438-1656
SN  - 1527-2648
VL  - 22
IS  - 4
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Safdari, Hadiseh
A1  - Cherstvy, Andrey G.
A1  - Chechkin, Aleksei V.
A1  - Bodrova, Anna
A1  - Metzler, Ralf
T1  - Aging underdamped scaled Brownian motion
BT  - Ensemble- and time-averaged particle displacements, nonergodicity, and the failure of the overdamping approximation
JF  - Physical review : E, Statistical, nonlinear and soft matter physics
N2  - We investigate both analytically and by computer simulations the ensemble- and time-averaged, nonergodic, and aging properties of massive particles diffusing in a medium with a time dependent diffusivity. We call this stochastic diffusion process the (aging) underdamped scaled Brownian motion (UDSBM). We demonstrate how the mean squared displacement (MSD) and the time-averaged MSD of UDSBM are affected by the inertial term in the Langevin equation, both at short, intermediate, and even long diffusion times. In particular, we quantify the ballistic regime for the MSD and the time-averaged MSD as well as the spread of individual time-averaged MSD trajectories. One of the main effects we observe is that, both for the MSD and the time-averaged MSD, for superdiffusive UDSBM the ballistic regime is much shorter than for ordinary Brownian motion. In contrast, for subdiffusive UDSBM, the ballistic region extends to much longer diffusion times. Therefore, particular care needs to be taken under what conditions the overdamped limit indeed provides a correct description, even in the long time limit. We also analyze to what extent ergodicity in the Boltzmann-Khinchin sense in this nonstationary system is broken, both for subdiffusive and superdiffusive UDSBM. Finally, the limiting case of ultraslow UDSBM is considered, with a mixed logarithmic and power-law dependence of the ensemble-and time-averaged MSDs of the particles. In the limit of strong aging, remarkably, the ordinary UDSBM and the ultraslow UDSBM behave similarly in the short time ballistic limit. The approaches developed here open ways for considering other stochastic processes under physically important conditions when a finite particle mass and aging in the system cannot be neglected.
Y1  - 2017
U6  - https://doi.org/10.1103/PhysRevE.95.012120
SN  - 2470-0045
SN  - 2470-0053
VL  - 95
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Shivhare, Rishi
A1  - Erdmann, Tim
A1  - Hoermann, Ulrich
A1  - Collado-Fregoso, Elisa
A1  - Zeiske, Stefan
A1  - Benduhn, Johannes
A1  - Ullbrich, Sascha
A1  - Huebner, Rene
A1  - Hambsch, Mike
A1  - Kiriy, Anton
A1  - Voit, Brigitte
A1  - Neher, Dieter
A1  - Vandewal, Koen
A1  - Mannsfeld, Stefan C. B.
T1  - Alkyl Branching Position in Diketopyrrolopyrrole Polymers
BT  - Interplay between Fibrillar Morphology and Crystallinity and Their Effect on Photogeneration and Recombination in Bulk-Heterojunction Solar Cells
JF  - Chemistry of materials : a publication of the American Chemical Society
N2  - Diketopyrrolopyrrole (DPP)-based donor acceptor copolymers have gained a significant amount of research interest in the organic electronics community because of their high charge carrier mobilities in organic field-effect transistors (OFETs) and their ability to harvest near-infrared (NIR) photons in solar cells. In this study, we have synthesized four DPP based donor-acceptor copolymers with variations in the donor unit and the branching point of the solubilizing alkyl chains (at the second or sixth carbon position). Grazing incidence wide-angle X-ray scattering (GIWAXS) results suggest that moving the branching point further away from the polymer backbone increases the tendency for aggregation and yields polymer phases with a higher degree of crystallinity (DoC). The polymers were blended with PC70BM and used as active layers in solar cells. A careful analysis of the energetics of the neat polymer and blend films reveals that the charge-transfer state energy (E-CT) of the blend films lies exceptionally close to the singlet energy of the donor (E-D*), indicating near zero electron transfer losses. The difference between the optical gap and open-circuit voltage (V-OC) is therefore determined to be due to rather high nonradiative 418 +/- 13 mV) and unavoidable radiative voltage losses (approximate to 255 +/- 8 mV). Even though the four materials have similar optical gaps, the short-circuit current density (J(SC)) covers a vast span from 7 to 18 mA cm(-2) for the best performing system. Using photoluminescence (PL) quenching and transient charge extraction techniques, we quantify geminate and nongeminate losses and find that fewer excitons reach the donor-acceptor interface in polymers with further away branching points due to larger aggregate sizes. In these material systems, the photogeneration is therefore mainly limited by exciton harvesting efficiency.
Y1  - 2018
U6  - https://doi.org/10.1021/acs.chemmater.8b02739
SN  - 0897-4756
SN  - 1520-5002
VL  - 30
IS  - 19
SP  - 6801
EP  - 6809
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Stolterfoht, Martin
A1  - Lang, Felix
T1  - All-perovskite tandems get flexible
JF  - Nature energy
N2  - Flexible all-perovskite tandem photovoltaics open up new opportunities for application compared to rigid devices, yet their performance lags behind. Now, researchers show that molecule-bridged interfaces mitigate charge recombination and crack formation, improving the efficiency and mechanical reliability of flexible devices.
Y1  - 2022
U6  - https://doi.org/10.1038/s41560-022-01087-6
SN  - 2058-7546
VL  - 7
IS  - 8
SP  - 688
EP  - 689
PB  - Nature Publishing Group
CY  - London
ER  - 
TY  - JOUR
A1  - Pelisoli, Ingrid
A1  - Vos, Joris
A1  - Geier, Stephan
A1  - Schaffenroth, Veronika
A1  - Baran, Andrzej S.
T1  - Alone but not lonely
BT  - observational evidence that binary interaction is always required to form hot subdwarf stars
JF  - Astronomy and astrophysics : an international weekly journal
N2  - Context. Hot subdwarfs are core-helium burning stars that show lower masses and higher temperatures than canonical horizontal branch stars. They are believed to be formed when a red giant suffers an extreme mass-loss episode. Binary interaction is suggested to be the main formation channel, but the high fraction of apparently single hot subdwarfs (up to 30%) has prompted single star formation scenarios to be proposed.Aims. We investigate the possibility that hot subdwarfs could form without interaction by studying wide binary systems. If single formation scenarios were possible, there should be hot subdwarfs in wide binaries that have undergone no interaction.Methods. Angular momentum accretion during interaction is predicted to cause the hot subdwarf companion to spin up to the critical velocity. The effect of this should still be observable given the timescales of the hot subdwarf phase. To study the rotation rates of companions, we have analysed light curves from the Transiting Exoplanet Survey Satellite for all known hot subdwarfs showing composite spectral energy distributions indicating the presence of a main sequence wide binary companion. If formation without interaction were possible, that would also imply the existence of hot subdwarfs in very wide binaries that are not predicted to interact. To identify such systems, we have searched for common proper motion companions with projected orbital distances of up to 0.1 pc to all known spectroscopically confirmed hot subdwarfs using Gaia DR2 astrometry.Results. We find that the companions in composite hot subdwarfs show short rotation periods when compared to field main sequence stars. They display a triangular-shaped distribution with a peak around 2.5 days, similar to what is observed for young open clusters. We also report a shortage of hot subdwarfs with candidate common proper motion companions. We identify only 16 candidates after probing 2938 hot subdwarfs with good astrometry. Out of those, at least six seem to be hierarchical triple systems, in which the hot subdwarf is part of an inner binary.Conclusions. The observed distribution of rotation rates for the companions in known wide hot subdwarf binaries provides evidence of previous interaction causing spin-up. Additionally, there is a shortage of hot subdwarfs in common proper motion pairs, considering the frequency of such systems among progenitors. These results suggest that binary interaction is always required for the formation of hot subdwarfs.
KW  - subdwarfs
KW  - binaries: general
KW  - stars: variables: general
Y1  - 2020
U6  - https://doi.org/10.1051/0004-6361/202038473
SN  - 0004-6361
SN  - 1432-0746
VL  - 642
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Davidzon, Iary
A1  - Ilbert, Olivier
A1  - Faisst, Andreas L.
A1  - Sparre, Martin
A1  - Capak, Peter L.
T1  - An Alternate Approach to Measure Specific Star Formation Rates at 2 < z < 7
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - We trace the specific star formation rate (sSFR) of massive star-forming galaxies (greater than or similar to 10(10)M(circle dot)) from z similar to 2 to 7. Our method is substantially different from previous analyses, as it does not rely on direct estimates of star formation rate, but on the differential evolution of the galaxy stellar mass function (SMF). We show the reliability of this approach by means of semianalytical and hydrodynamical cosmological simulations. We then apply it to real data, using the SMFs derived in the COSMOS and CANDELS fields. We find that the sSFR is proportional to (1 + z)(1.1) (+/-) (0.2) at z > 2, in agreement with other observations but in tension with the steeper evolution predicted by simulations from z similar to 4 to 2. We investigate the impact of several sources of observational bias, which, however, cannot account for this discrepancy. Although the SMF of high-redshift galaxies is still affected by significant errors, we show that future large-area surveys will substantially reduce them, making our method an effective tool to probe the massive end of the main sequence of star-forming galaxies.
KW  - galaxies: evolution
KW  - galaxies: high-redshift
KW  - galaxies: star formation
Y1  - 2018
U6  - https://doi.org/10.3847/1538-4357/aaa19e
SN  - 0004-637X
SN  - 1538-4357
VL  - 852
IS  - 2
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Ciemer, Catrin
A1  - Rehm, Lars
A1  - Kurths, Jürgen
A1  - Donner, Reik Volker
A1  - Winkelmann, Ricarda
A1  - Boers, Niklas
T1  - An early-warning indicator for Amazon droughts exclusively based on tropical Atlantic sea surface temperatures
JF  - Environmental Research Letters
N2  - Droughts in tropical South America have an imminent and severe impact on the Amazon rainforest and affect the livelihoods of millions of people. Extremely dry conditions in Amazonia have been previously linked to sea surface temperature (SST) anomalies in the adjacent tropical oceans. Although the sources and impacts of such droughts have been widely studied, establishing reliable multi-year lead statistical forecasts of their occurrence is still an ongoing challenge. Here, we further investigate the relationship between SST and rainfall anomalies using a complex network approach. We identify four ocean regions which exhibit the strongest overall SST correlations with central Amazon rainfall, including two particularly prominent regions in the northern and southern tropical Atlantic. Based on the time-dependent correlation between SST anomalies in these two regions alone, we establish a new early-warning method for droughts in the central Amazon basin and demonstrate its robustness in hindcasting past major drought events with lead-times up to 18 months.
KW  - complex networks
KW  - droughts
KW  - prediction
KW  - Amazon rainforest
Y1  - 2019
VL  - 15
IS  - 9
PB  - IOP - Institute of Physics Publishing
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Smirnov, Artem
A1  - Shprits, Yuri Y.
A1  - Allison, Hayley
A1  - Aseev, Nikita
A1  - Drozdov, Alexander
A1  - Kollmann, Peter
A1  - Wang, Dedong
A1  - Saikin, Anthony
T1  - An empirical model of the equatorial electron pitch angle distributions in earth's outer radiation belt
JF  - Space Weather: the International Journal of Research and Applications
N2  - In this study, we present an empirical model of the equatorial electron pitch angle distributions (PADs) in the outer radiation belt based on the full data set collected by the Magnetic Electron Ion Spectrometer (MagEIS) instrument onboard the Van Allen Probes in 2012-2019. The PADs are fitted with a combination of the first, third and fifth sine harmonics. The resulting equation resolves all PAD types found in the outer radiation belt (pancake, flat-top, butterfly and cap PADs) and can be analytically integrated to derive omnidirectional flux. We introduce a two-step modeling procedure that for the first time ensures a continuous dependence on L, magnetic local time and activity, parametrized by the solar wind dynamic pressure. We propose two methods to reconstruct equatorial electron flux using the model. The first approach requires two uni-directional flux observations and is applicable to low-PA data. The second method can be used to reconstruct the full equatorial PADs from a single uni- or omnidirectional measurement at off-equatorial latitudes. The model can be used for converting the long-term data sets of electron fluxes to phase space density in terms of adiabatic invariants, for physics-based modeling in the form of boundary conditions, and for data assimilation purposes.
KW  - pitch angle
KW  - radiation belt
KW  - model
KW  - magnetosphere
KW  - van allen probes;
KW  - electrons
Y1  - 2022
U6  - https://doi.org/10.1029/2022SW003053
SN  - 1542-7390
VL  - 20
IS  - 9
PB  - American Geophysical Union
CY  - Washington, DC
ER  - 
TY  - JOUR
A1  - Grebenkov, Denis S.
T1  - An encounter-based approach for restricted diffusion with a gradient drift
JF  - Journal of physics : A, Mathematical and theoretical
N2  - We develop an encounter-based approach for describing restricted diffusion with a gradient drift toward a partially reactive boundary. For this purpose, we introduce an extension of the Dirichlet-to-Neumann operator and use its eigenbasis to derive a spectral decomposition for the full propagator, i.e. the joint probability density function for the particle position and its boundary local time. This is the central quantity that determines various characteristics of diffusion-influenced reactions such as conventional propagators, survival probability, first-passage time distribution, boundary local time distribution, and reaction rate. As an illustration, we investigate the impact of a constant drift onto the boundary local time for restricted diffusion on an interval. More generally, this approach accesses how external forces may influence the statistics of encounters of a diffusing particle with the reactive boundary.
KW  - boundary local time
KW  - reflected Brownian motion
KW  - diffusion-influenced
KW  - reactions
KW  - surface reactivity
KW  - Robin boundary condition
KW  - Heterogeneous
KW  - catalysis
Y1  - 2022
U6  - https://doi.org/10.1088/1751-8121/ac411a
SN  - 1751-8113
SN  - 1751-8121
VL  - 55
IS  - 4
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Nakoudi, Konstantina
A1  - Stachlewska, Iwona S.
A1  - Ritter, Christoph
T1  - An extended lidar-based cirrus cloud retrieval scheme
BT  - first application over an Arctic site
JF  - Optics express : the international electronic journal of optics / Optica
N2  - Accurate and precise characterization of cirrus cloud geometrical and optical properties is essential for better constraining their radiative footprint. A lidar-based retrieval scheme is proposed here, with its performance assessed on fine spatio-temporal observations over the Arctic site of Ny-Alesund, Svalbard. Two contributions related to cirrus geometrical (dynamic Wavelet Covariance Transform (WCT)) and optical properties (constrained Klett) are reported. The dynamic WCT rendered cirrus detection more robust, especially for thin cirrus layers that frequently remained undetected by the classical WCT method. Regarding optical characterization, we developed an iterative scheme for determining the cirrus lidar ratio (LRci) that is a crucial parameter for aerosol - cloud discrimination. Building upon the Klett-Fernald method, the LRci was constrained by an additional reference value. In established methods, such as the double-ended Klett, an aerosol-free reference value is applied. In the proposed constrained Klett, however, the reference value was approximated from cloud-free or low cloud optical depth (COD up to 0.2) profiles and proved to agree with independent Raman estimates. For optically thin cirrus, the constrained Klett inherent uncertainties reached 50% (60-74%) in terms of COD (LRci). However, for opaque cirrus COD (LRci) uncertainties were lower than 10% (15%). The detection method discrepancies (dynamic versus static WCT) had a higher impact on the optical properties of low COD layers (up to 90%) compared to optically thicker ones (less than 10%). The constrained Klett presented high agreement with two established retrievals. For an exemplary cirrus cloud, the constrained Klett estimated the COD355 (LRci355) at 0.28 +/- 0.17 (29 +/- 4 sr), the double-ended Klett at 0.27 +/- 0.15 (32 +/- 4 sr) and the Raman retrievals at 0.22 +/- 0.12 (26 +/- 11 sr). Our approach to determine the necessary reference value can also be applied in established methods and increase their accuracy. In contrast, the classical aerosol-free assumption led to 44 sr LRci overestimation in optically thin layers and 2-8 sr in thicker ones. The multiple scattering effect was corrected using Eloranta (1998) and accounted for 50-60% extinction underestimation near the cloud base and 20-30% within the cirrus layers.
Y1  - 2021
U6  - https://doi.org/10.1364/OE.414770
SN  - 1094-4087
VL  - 29
IS  - 6
SP  - 8553
EP  - 8580
PB  - Optical Society of America
CY  - Washington
ER  - 
TY  - JOUR
A1  - Abdalla, H.
A1  - Adam, R.
A1  - Aharonian, Felix A.
A1  - Benkhali, F. Ait
A1  - Angüner, Ekrem Oǧuzhan
A1  - Arcaro, C.
A1  - Armand, C.
A1  - Armstrong, T.
A1  - Ashkar, H.
A1  - Backes, M.
A1  - Baghmanyan, V.
A1  - Martins, V. Barbosa
A1  - Barnacka, A.
A1  - Barnard, M.
A1  - Becherini, Y.
A1  - Berge, D.
A1  - Bernlohr, K.
A1  - Bi, B.
A1  - Bottcher, M.
A1  - Boisson, C.
A1  - Bolmont, J.
A1  - de Lavergne, M. de Bony
A1  - Bordas, Pol
A1  - Breuhaus, M.
A1  - Brun, F.
A1  - Brun, P.
A1  - Bryan, M.
A1  - Buchele, M.
A1  - Bulik, T.
A1  - Bylund, T.
A1  - Caroff, S.
A1  - Carosi, A.
A1  - Casanova, Sabrina
A1  - Chand, T.
A1  - Chandra, S.
A1  - Chen, A.
A1  - Cotter, G.
A1  - Curylo, M.
A1  - Mbarubucyeye, J. Damascene
A1  - Davids, I. D.
A1  - Davies, J.
A1  - Deil, C.
A1  - Devin, J.
A1  - deWilt, P.
A1  - Dirson, L.
A1  - Djannati-Atai, A.
A1  - Dmytriiev, A.
A1  - Donath, A.
A1  - Doroshenko, V.
A1  - Duffy, C.
A1  - Dyks, J.
A1  - Egberts, Kathrin
A1  - Eichhorn, F.
A1  - Einecke, S.
A1  - Emery, G.
A1  - Ernenwein, J. -P.
A1  - Feijen, K.
A1  - Fegan, S.
A1  - Fiasson, A.
A1  - de Clairfontaine, G. Fichet
A1  - Fontaine, G.
A1  - Funk, S.
A1  - Fussling, Matthias
A1  - Gabici, S.
A1  - Gallant, Y. A.
A1  - Giavitto, G.
A1  - Giunti, L.
A1  - Glawion, D.
A1  - Glicenstein, J. F.
A1  - Gottschall, D.
A1  - Grondin, M. -H.
A1  - Hahn, J.
A1  - Haupt, M.
A1  - Hermann, G.
A1  - Hinton, J. A.
A1  - Hofmann, W.
A1  - Hoischen, Clemens
A1  - Holch, T. L.
A1  - Holler, M.
A1  - Horbe, M.
A1  - Horns, D.
A1  - Huber, D.
A1  - Jamrozy, M.
A1  - Jankowsky, D.
A1  - Jankowsky, F.
A1  - Jardin-Blicq, A.
A1  - Joshi, V.
A1  - Jung-Richardt, I.
A1  - Kasai, E.
A1  - Kastendieck, M. A.
A1  - Katarzynski, K.
A1  - Katz, U.
A1  - Khangulyan, D.
A1  - Khelifi, B.
A1  - Klepser, S.
A1  - Kluzniak, W.
A1  - Komin, Nu.
A1  - Konno, R.
A1  - Kosack, K.
A1  - Kostunin, D.
A1  - Kreter, M.
A1  - Lamanna, G.
A1  - Lemiere, A.
A1  - Lemoine-Goumard, M.
A1  - Lenain, J. -P.
A1  - Levy, C.
A1  - Lohse, T.
A1  - Lypova, I.
A1  - Mackey, J.
A1  - Majumdar, J.
A1  - Malyshev, D.
A1  - Malyshev, D.
A1  - Marandon, V.
A1  - Marchegiani, P.
A1  - Marcowith, Alexandre
A1  - Mares, A.
A1  - Marti-Devesa, G.
A1  - Marx, R.
A1  - Maurin, G.
A1  - Meintjes, P. J.
A1  - Meyer, M.
A1  - Mitchell, A.
A1  - Moderski, R.
A1  - Mohamed, M.
A1  - Mohrmann, L.
A1  - Montanari, A.
A1  - Moore, C.
A1  - Morris, P.
A1  - Moulin, Emmanuel
A1  - Muller, J.
A1  - Murach, T.
A1  - Nakashima, K.
A1  - Nayerhoda, A.
A1  - de Naurois, M.
A1  - Ndiyavala, H.
A1  - Niederwanger, F.
A1  - Niemiec, J.
A1  - Oakes, L.
A1  - O'Brien, Patrick
A1  - Odaka, H.
A1  - Ohm, S.
A1  - Olivera-Nieto, L.
A1  - Wilhelmi, E. de Ona
A1  - Ostrowski, M.
A1  - Oya, I.
A1  - Panter, M.
A1  - Panny, S.
A1  - Parsons, R. D.
A1  - Peron, G.
A1  - Peyaud, B.
A1  - Piel, Q.
A1  - Pita, S.
A1  - Poireau, V.
A1  - Noel, A. Priyana
A1  - Prokhorov, D. A.
A1  - Prokoph, H.
A1  - Puhlhofer, G.
A1  - Punch, M.
A1  - Quirrenbach, A.
A1  - Raab, S.
A1  - Rauth, R.
A1  - Reichherzer, P.
A1  - Reimer, A.
A1  - Reimer, O.
A1  - Remy, Q.
A1  - Renaud, M.
A1  - Rieger, F.
A1  - Rinchiuso, L.
A1  - Romoli, C.
A1  - Rowell, G.
A1  - Rudak, B.
A1  - Ruiz-Velasco, E.
A1  - Sahakian, V.
A1  - Sailer, S.
A1  - Sanchez, D. A.
A1  - Santangelo, Andrea
A1  - Sasaki, M.
A1  - Scalici, M.
A1  - Schussler, F.
A1  - Schutte, H. M.
A1  - Schwanke, U.
A1  - Schwemmer, S.
A1  - Seglar-Arroyo, M.
A1  - Senniappan, M.
A1  - Seyffert, A. S.
A1  - Shafi, N.
A1  - Shiningayamwe, K.
A1  - Simoni, R.
A1  - Sinha, A.
A1  - Sol, H.
A1  - Specovius, A.
A1  - Spencer, S.
A1  - Spir-Jacob, M.
A1  - Stawarz, L.
A1  - Sun, L.
A1  - Steenkamp, R.
A1  - Stegmann, C.
A1  - Steinmassl, S.
A1  - Steppa, C.
A1  - Takahashi, T.
A1  - Tavernier, T.
A1  - Taylor, A. M.
A1  - Terrier, R.
A1  - Tiziani, D.
A1  - Tluczykont, M.
A1  - Tomankova, L.
A1  - Trichard, C.
A1  - Tsirou, M.
A1  - Tuffs, R.
A1  - Uchiyama, Y.
A1  - van der Walt, D. J.
A1  - van Eldik, C.
A1  - van Rensburg, C.
A1  - van Soelen, B.
A1  - Vasileiadis, G.
A1  - Veh, J.
A1  - Venter, C.
A1  - Vincent, P.
A1  - Vink, J.
A1  - Volk, H. J.
A1  - Vuillaume, T.
A1  - Wadiasingh, Z.
A1  - Wagner, S. J.
A1  - Watson, J.
A1  - Werner, F.
A1  - White, R.
A1  - Wierzcholska, A.
A1  - Wong, Yu Wun
A1  - Yusafzai, A.
A1  - Zacharias, M.
A1  - Zanin, R.
A1  - Zargaryan, D.
A1  - Zdziarski, A. A.
A1  - Zech, Alraune
A1  - Zhu, S. J.
A1  - Ziegler, A.
A1  - Zorn, J.
A1  - Zouari, S.
A1  - Zywucka, N.
T1  - An extreme particle accelerator in the Galactic plane
BT  - HESS J1826-130
JF  - Astronomy and astrophysics : an international weekly journal
N2  - The unidentified very-high-energy (VHE; E > 0.1 TeV) gamma -ray source, HESS J1826-130, was discovered with the High Energy Stereoscopic System (HESS) in the Galactic plane. The analysis of 215 h of HESS data has revealed a steady gamma -ray flux from HESS J1826-130, which appears extended with a half-width of 0.21 degrees +/- 0.02 <br /> (stat)degrees <br /> stat degrees +/- 0.05 <br /> (sys)degrees sys degrees . The source spectrum is best fit with either a power-law function with a spectral index Gamma = 1.78 +/- 0.10(stat) +/- 0.20(sys) and an exponential cut-off at 15.2 <br /> (+5.5)(-3.2) -3.2+5.5 TeV, or a broken power-law with Gamma (1) = 1.96 +/- 0.06(stat) +/- 0.20(sys), Gamma (2) = 3.59 +/- 0.69(stat) +/- 0.20(sys) for energies below and above E-br = 11.2 +/- 2.7 TeV, respectively. The VHE flux from HESS J1826-130 is contaminated by the extended emission of the bright, nearby pulsar wind nebula, HESS J1825-137, particularly at the low end of the energy spectrum. Leptonic scenarios for the origin of HESS J1826-130 VHE emission related to PSR J1826-1256 are confronted by our spectral and morphological analysis. In a hadronic framework, taking into account the properties of dense gas regions surrounding HESS J1826-130, the source spectrum would imply an astrophysical object capable of accelerating the parent particle population up to greater than or similar to 200 TeV. Our results are also discussed in a multiwavelength context, accounting for both the presence of nearby supernova remnants, molecular clouds, and counterparts detected in radio, X-rays, and TeV energies.
KW  - ISM: supernova remnants
KW  - ISM: clouds
KW  - gamma rays: general
KW  - gamma rays:
KW  - ISM
Y1  - 2020
U6  - https://doi.org/10.1051/0004-6361/202038851
SN  - 0004-6361
SN  - 1432-0746
VL  - 644
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - He, Yushuang
A1  - Wang, Feipeng
A1  - He, Li
A1  - Wang, Qiang
A1  - Li, Jian
A1  - Qian, Yihua
A1  - Gerhard, Reimund
A1  - Plath, Ronald
T1  - An insight Into the role of Nano-Alumina on DC Flashover-Resistance and surface charge variation of Epoxy Nanocomposites
JF  - IEEE transactions on dielectrics and electrical insulation
N2  - The addition of nano-Al2O3 has been shown to enhance the breakdown voltage of epoxy resin, but its flashover results appeared with disputation. This work concentrates on the surface charge variation and dc flashover performance of epoxy resin with nano-Al2O3 doping. The dispersion of nano-Al2O3 in epoxy is characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The dc flashover voltages of samples under either positive or negative polarity are measured with a finger-electrode system, and the surface charge variations before and after flashovers were identified from the surface potential mapping. The results evidence that nano-Al2O3 would lead to a 16.9% voltage drop for the negative flashovers and a 6.8% drop for positive cases. It is found that one-time flashover clears most of the accumulated surface charges, regardless of positive or negative. As a result, the ground electrode is neighbored by an equipotential zone enclosed with low-density heterocharges. The equipotential zone tends to be broadened after 20 flashovers. The nano-Al2O3 is noticed as beneficial to downsize the equipotential zone due to its capability on charge migration, which is reasonable to maintain flashover voltage at a high level after multiple flashovers. Hence, nano-Al2O3 plays a significant role in improving epoxy with high resistance to multiple flashovers.
KW  - surface morphology
KW  - Epoxy resins
KW  - Electric potential
KW  - Surface treatment
KW  - Doping
KW  - Epoxy resin
KW  - multiple
KW  - flashover
KW  - nanocomposite
KW  - surface charge
Y1  - 2022
U6  - https://doi.org/10.1109/TDEI.2022.3173510
SN  - 1070-9878
SN  - 1558-4135
VL  - 29
IS  - 3
SP  - 1022
EP  - 1029
PB  - Inst. of Electr. and Electronics Engineers
CY  - Piscataway
ER  - 
TY  - JOUR
A1  - Wiljes, Jana de
A1  - Tong, Xin T.
T1  - Analysis of a localised nonlinear ensemble Kalman Bucy filter with complete and accurate observations
JF  - Nonlinearity
N2  - Concurrent observation technologies have made high-precision real-time data available in large quantities. Data assimilation (DA) is concerned with how to combine this data with physical models to produce accurate predictions. For spatial-temporal models, the ensemble Kalman filter with proper localisation techniques is considered to be a state-of-the-art DA methodology. This article proposes and investigates a localised ensemble Kalman Bucy filter for nonlinear models with short-range interactions. We derive dimension-independent and component-wise error bounds and show the long time path-wise error only has logarithmic dependence on the time range. The theoretical results are verified through some simple numerical tests.
KW  - data assimilation
KW  - stability and accuracy
KW  - dimension independent bound
KW  - localisation
KW  - high dimensional
KW  - filter
KW  - nonlinear
Y1  - 2020
U6  - https://doi.org/10.1088/1361-6544/ab8d14
SN  - 0951-7715
SN  - 1361-6544
VL  - 33
IS  - 9
SP  - 4752
EP  - 4782
PB  - IOP Publ.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Knoche, Lisa
A1  - Lisec, Jan
A1  - Koch, Matthias
T1  - Analysis of electrochemical and liver microsomal transformation products of lasalocid by LC/HRMS
JF  - Rapid communications in mass spectrometry : RCM
N2  - Rationale:
Lasalocid (LAS), an ionophore, is used in cattle and poultry farming as feed additive for its antibiotic and growth-promoting properties. Literature on transformation products (TP) resulting from LAS degradation is limited. So far, only hydroxylation is found to occur as the metabolic reaction during the LAS degradation. To investigate potential TPs of LAS, we used electrochemistry (EC) and liver microsome (LM) assays to synthesize TPs, which were identified using liquid chromatography high-resolution mass spectrometry (LC/HRMS). 

Methods:
Electrochemically produced TPs were analyzed online by direct coupling of the electrochemical cell to the electrospray ionization (ESI) source of a Sciex Triple-TOF high resolution mass spectrometer. Then, EC-treated LAS solution was collected and analyzed offline using LC/HRMS to confirm stable TPs and improve their annotation with a chemical structure due to informative MS/MS spectra. In a complementary approach, TPs formed by rat and human microsomal incubation were investigated using LC/HRMS. The resulting data were used to investigate LAS modification reactions and elucidate the chemical structure of obtained TPs.

Results:
The online measurements identified a broad variety of TPs, resulting from modification reactions like (de-)hydrogenation, hydration, methylation, oxidation as well as adduct formation with methanol. We consistently observed different ion complexations of LAS and LAS-TPs (Na+; 2Na(+) K+; NaNH4+; KNH4+). Two stable methylated EC-TPs were found, structurally annotated, and assigned to a likely modification reaction. Using LM incubation, seven TPs were formed, mostly by oxidation/hydroxylation. After the identification of LM-TPs as Na+-complexes, we identified LM-TPs as K+-complexes.

Conclusion:
We identified and characterized TPs of LAS using EC- and LM-based methods. Moreover, we found different ion complexes of LAS-based TPs. This knowledge, especially the different ion complexes, may help elucidate the metabolic and environmental degradation pathways of LAS.
Y1  - 2022
U6  - https://doi.org/10.1002/rcm.9349
SN  - 0951-4198
SN  - 1097-0231
VL  - 36
IS  - 18
PB  - Wiley
CY  - New York, NY
ER  - 
TY  - JOUR
A1  - Rinaldi, G.
A1  - Formisano, M.
A1  - Kappel, David
A1  - Capaccioni, F.
A1  - Bockelee-Morvan, D.
A1  - Cheng, Y-C
A1  - Vincent, J-B
A1  - Deshapriya, P.
A1  - Arnold, G.
A1  - Capria, M. T.
A1  - Ciarniello, M.
A1  - De Sanctis, M. C.
A1  - Doose, L.
A1  - Erard, S.
A1  - Federico, C.
A1  - Filacchione, G.
A1  - Fink, U.
A1  - Leyrat, C.
A1  - Longobardo, A.
A1  - Magni, G.
A1  - Mighorini, A.
A1  - Mottola, S.
A1  - Naletto, G.
A1  - Raponi, A.
A1  - Taylor, F.
A1  - Tosi, F.
A1  - Tozzi, G. P.
A1  - Salatti, M.
T1  - Analysis of night-side dust activity on comet 67P observed by VIRTIS-M
BT  - a new method to constrain the thermal inertia on the surface
JF  - Astronomy and astrophysics : an international weekly journal
N2  - On 2015 July 18, near perihelion at a heliocentric distance of 1.28 au, the Visible InfraRed Thermal Imaging Spectrometer (VIRTIS-M) on board the Rosetta spacecraft had the opportunity of observing dust activity in the inner coma with a view of the night side (shadowed side) of comet 67P/Churyumov-Gerasimenko. At the time of the measurements we present here, we observe a dust plume that originates on the far side of the nucleus. We are able to identify the approximate location of its source at the boundary between the Hapi and Anuket regions, and we find that it has been in darkness for some hours before the observation. Assuming that this time span is equal to the conductive time scale, we obtain a thermal inertia in the range 25-36 W K-1 m(-2) s(-1/2). These thermal inertia values can be used to verify with a 3D finite-element method (REM) numerical code whether the surface and subsurface temperatures agree with the values found in the literature. We explored three different configurations: (1) a layer of water ice mixed with dust beneath a dust mantle of 5 mm with thermal inertia of 36 J m(-2) K-1 S-0.5 ; (2) the same structure, but with thermal inertia of 100 J m(-2) K-1 S-0.5; (3) an ice-dust mixture that is directly exposed. Of these three configurations, the first seems to be the most reasonable, both for the low thermal inertia and for the agreement with the surface and subsurface temperatures that have been found for the comet 67P/Churyumov-Gerasimenko. The spectral properties of the plume show that the visible dust color ranged from 16 +/- 4.8%/100 nm to 13 +/- 2.6%/100 nm, indicating that this plume has no detectable color gradient. The morphology of the plume can be classified as a narrow jet that has an estimated total ejected mass of between 6 and 19 tons when we assume size distribution indices between -2.5 and -3.
KW  - comets: general
KW  - comets: individual: 67P/Churyumov-Gerasimenko
KW  - infrared: planetary systems
Y1  - 2019
U6  - https://doi.org/10.1051/0004-6361/201834907
SN  - 1432-0746
VL  - 630
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Mattern, Maximilian
A1  - Pudell, Jan-Etienne
A1  - Laskin, Gennadii
A1  - Reppert, Alexander von
A1  - Bargheer, Matias
T1  - Analysis of the temperature- and fluence-dependent magnetic stress in laser-excited SrRuO3
JF  - Structural dynamics
N2  - We use ultrafast x-ray diffraction to investigate the effect of expansive phononic and contractive magnetic stress driving the picosecond strain response of a metallic perovskite SrRuO3 thin film upon femtosecond laser excitation. We exemplify how the anisotropic bulk equilibrium thermal expansion can be used to predict the response of the thin film to ultrafast deposition of energy. It is key to consider that the laterally homogeneous laser excitation changes the strain response compared to the near-equilibrium thermal expansion because the balanced in-plane stresses suppress the Poisson stress on the picosecond timescale. We find a very large negative Grüneisen constant describing the large contractive stress imposed by a small amount of energy in the spin system. The temperature and fluence dependence of the strain response for a double-pulse excitation scheme demonstrates the saturation of the magnetic stress in the high-fluence regime.
KW  - Thin films
KW  - Thermodynamic properties
KW  - Bragg peak
KW  - Ultrafast X-ray diffraction
KW  - Thermal effects
KW  - Phonons
KW  - Magnetism
KW  - Lattice dynamics
KW  - Lasers
KW  - Perovskites
Y1  - 2020
U6  - https://doi.org/10.1063/4.0000072
SN  - 2329-7778
VL  - 8
IS  - 2
PB  - AIP Publishing LLC
CY  - Melville, NY
ER  - 
TY  - JOUR
A1  - Cecchini, Gloria
A1  - Schelter, Björn
T1  - Analytical approach to network inference
BT  - Investigating degree distribution
JF  - Physical review : E, Statistical, nonlinear and soft matter physics
N2  - When the network is reconstructed, two types of errors can occur: false positive and false negative errors about the presence or absence of links. In this paper, the influence of these two errors on the vertex degree distribution is analytically analyzed. Moreover, an analytic formula of the density of the biased vertex degree distribution is found. In the inverse problem, we find a reliable procedure to reconstruct analytically the density of the vertex degree distribution of any network based on the inferred network and estimates for the false positive and false negative errors based on, e.g., simulation studies.
Y1  - 2018
U6  - https://doi.org/10.1103/PhysRevE.98.022311
SN  - 2470-0045
SN  - 2470-0053
VL  - 98
IS  - 2
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Munyaev, Vyacheslav O.
A1  - Smirnov, Lev A.
A1  - Kostin, Vasily A.
A1  - Osipov, Grigory V.
A1  - Pikovskij, Arkadij
T1  - Analytical approach to synchronous states of globally coupled noisy rotators
JF  - New journal of physics : the open-access journal for physics
N2  - We study populations of globally coupled noisy rotators (oscillators with inertia) allowing a nonequilibrium transition from a desynchronized state to a synchronous one (with the nonvanishing order parameter). The newly developed analytical approaches resulted in solutions describing the synchronous state with constant order parameter for weakly inertial rotators, including the case of zero inertia, when the model is reduced to the Kuramoto model of coupled noise oscillators. These approaches provide also analytical criteria distinguishing supercritical and subcritical transitions to the desynchronized state and indicate the universality of such transitions in rotator ensembles. All the obtained analytical results are confirmed by the numerical ones, both by direct simulations of the large ensembles and by solution of the associated Fokker-Planck equation. We also propose generalizations of the developed approaches for setups where different rotators parameters (natural frequencies, masses, noise intensities, strengths and phase shifts in coupling) are dispersed.
KW  - coupled rotators
KW  - synchronization transition
KW  - hysteresis
KW  - Kuramoto
KW  - model
KW  - noisy systems
Y1  - 2020
U6  - https://doi.org/10.1088/1367-2630/ab6f93
SN  - 1367-2630
VL  - 22
IS  - 2
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Munyaev, Vyacheslav
A1  - Smirnov, Lev A.
A1  - Kostin, Vasily
A1  - Osipov, Grigory V.
A1  - Pikovskij, Arkadij
T1  - Analytical approach to synchronous states of globally coupled noisy rotators
JF  - New Journal of Physics
N2  - We study populations of globally coupled noisy rotators (oscillators with inertia) allowing a nonequilibrium transition from a desynchronized state to a synchronous one (with the nonvanishing order parameter). The newly developed analytical approaches resulted in solutions describing the synchronous state with constant order parameter for weakly inertial rotators, including the case of zero inertia, when the model is reduced to the Kuramoto model of coupled noise oscillators. These approaches provide also analytical criteria distinguishing supercritical and subcritical transitions to the desynchronized state and indicate the universality of such transitions in rotator ensembles. All the obtained analytical results are confirmed by the numerical ones, both by direct simulations of the large ensembles and by solution of the associated Fokker-Planck equation. We also propose generalizations of the developed approaches for setups where different rotators parameters (natural frequencies, masses, noise intensities, strengths and phase shifts in coupling) are dispersed.
KW  - coupled rotators
KW  - synchronization transition
KW  - hysteresis
KW  - Kuramoto model
KW  - noisy systems
Y1  - 2019
VL  - 22
IS  - 2
PB  - Springer Science
CY  - New York
ER  - 
TY  - JOUR
A1  - Wang, Dedong
A1  - Shprits, Yuri Y.
A1  - Zhelayskaya, Irina S.
A1  - Agapitov, Oleksiy
A1  - Drozdov, Alexander
A1  - Aseev, Nikita
T1  - Analytical chorus wave model derived from van Allen Probe Observations
JF  - Journal of geophysical research : Space physics
N2  - Chorus waves play an important role in the dynamic evolution of energetic electrons in the Earth's radiation belts and ring current. Using more than 5 years of Van Allen Probe data, we developed a new analytical model for upper‐band chorus (UBC; 0.5fce < f < fce) and lower‐band chorus (LBC; 0.05fce < f < 0.5fce) waves, where fce is the equatorial electron gyrofrequency. By applying polynomial fits to chorus wave root mean square amplitudes, we developed regression models for LBC and UBC as a function of geomagnetic activity (Kp), L, magnetic latitude (λ), and magnetic local time (MLT). Dependence on Kp is separated from the dependence on λ, L, and MLT as Kp‐scaling law to simplify the calculation of diffusion coefficients and inclusion into particle tracing codes. Frequency models for UBC and LBC are also developed, which depends on MLT and magnetic latitude. This empirical model is valid in all MLTs, magnetic latitude up to 20°, Kp ≤ 6, L‐shell range from 3.5 to 6 for LBC and from 4 to 6 for UBC. The dependence of root mean square amplitudes on L are different for different bands, which implies different energy sources for different wave bands. This analytical chorus wave model is convenient for inclusion in quasi‐linear diffusion calculations of electron scattering rates and particle simulations in the inner magnetosphere, especially for the newly developed four‐dimensional codes, which require significantly improved wave parameterizations.
KW  - chorus waves
KW  - radiation belt electrons
KW  - ring current electrons
KW  - analytical model
KW  - wave-particle interactions
KW  - diffusion coefficients
Y1  - 2019
U6  - https://doi.org/10.1029/2018JA026183
SN  - 2169-9380
SN  - 2169-9402
VL  - 124
IS  - 2
SP  - 1063
EP  - 1084
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Stange, Maike
A1  - Hintsche, Marius
A1  - Sachse, Kirsten
A1  - Gerhardt, Matthias
A1  - Valleriani, Angelo
A1  - Beta, Carsten
T1  - Analyzing the spatial positioning of nuclei in polynuclear giant cells
JF  - Journal of Physics D: Applied Physics
N2  - How cells establish and maintain a well-defined size is a fundamental question of cell biology. Here we investigated to what extent the microtubule cytoskeleton can set a predefined cell size, independent of an enclosing cell membrane. We used electropulse-induced cell fusion to form giant multinuclear cells of the social amoeba Dictyostelium discoideum. Based on dual-color confocal imaging of cells that expressed fluorescent markers for the cell nucleus and the microtubules, we determined the subcellular distributions of nuclei and centrosomes in the giant cells. Our two- and three-dimensional imaging results showed that the positions of nuclei in giant cells do not fall onto a regular lattice. However, a comparison with model predictions for random positioning showed that the subcellular arrangement of nuclei maintains a low but still detectable degree of ordering. This can be explained by the steric requirements of the microtubule cytoskeleton, as confirmed by the effect of a microtubule degrading drug.
KW  - Dictyostelium
KW  - cell nucleus
KW  - positioning
KW  - imaging
KW  - spatial poisson distribution
Y1  - 2017
U6  - https://doi.org/10.1088/1361-6463/aa8da0
SN  - 0022-3727
SN  - 1361-6463
VL  - 50
IS  - 46
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Dieterich, Peter
A1  - Lindemann, Otto
A1  - Moskopp, Mats Leif
A1  - Tauzin, Sebastien
A1  - Huttenlocher, Anna
A1  - Klages, Rainer
A1  - Chechkin, Aleksei V.
A1  - Schwab, Albrecht
T1  - Anomalous diffusion and asymmetric tempering memory in neutrophil chemotaxis
JF  - PLoS Computational Biology : a new community journal
N2  - Neutrophil granulocytes are essential for the first host defense. After leaving the blood circulation they migrate efficiently towards sites of inflammation. They are guided by chemoattractants released from cells within the inflammatory foci. On a cellular level, directional migration is a consequence of cellular front-rear asymmetry which is induced by the concentration gradient of the chemoattractants. The generation and maintenance of this asymmetry, however, is not yet fully understood. Here we analyzed the paths of chemotacting neutrophils with different stochastic models to gain further insight into the underlying mechanisms. Wildtype chemotacting neutrophils show an anomalous superdiffusive behavior. CXCR2 blockade and TRPC6-knockout cause the tempering of temporal correlations and a reduction of chemotaxis. Importantly, such tempering is found both in vitro and in vivo. These findings indicate that the maintenance of anomalous dynamics is crucial for chemotactic behavior and the search efficiency of neutrophils. 
The motility of neutrophils and their ability to sense and to react to chemoattractants in their environment are of central importance for the innate immunity. Neutrophils are guided towards sites of inflammation following the activation of G-protein coupled chemoattractant receptors such as CXCR2 whose signaling strongly depends on the activity of Ca2+ permeable TRPC6 channels. It is the aim of this study to analyze data sets obtained in vitro (murine neutrophils) and in vivo (zebrafish neutrophils) with a stochastic mathematical model to gain deeper insight into the underlying mechanisms. The model is based on the analysis of trajectories of individual neutrophils. Bayesian data analysis, including the covariances of positions for fractional Brownian motion as well as for exponentially and power-law tempered model variants, allows the estimation of parameters and model selection. Our model-based analysis reveals that wildtype neutrophils show pure superdiffusive fractional Brownian motion. This so-called anomalous dynamics is characterized by temporal long-range correlations for the movement into the direction of the chemotactic CXCL1 gradient. Pure superdiffusion is absent vertically to this gradient. This points to an asymmetric 'memory' of the migratory machinery, which is found both in vitro and in vivo. CXCR2 blockade and TRPC6-knockout cause tempering of temporal correlations in the chemotactic gradient. This can be interpreted as a progressive loss of memory, which leads to a marked reduction of chemotaxis and search efficiency of neutrophils. In summary, our findings indicate that spatially differential regulation of anomalous dynamics appears to play a central role in guiding efficient chemotactic behavior.
KW  - neutrophils
KW  - chemotaxis
KW  - autocorrelation
KW  - zebrafish
KW  - cell migration
KW  - covariance
KW  - brownian motion
KW  - stochastic processes
Y1  - 2022
U6  - https://doi.org/10.1371/journal.pcbi.1010089
SN  - 1553-734X
SN  - 1553-7358
VL  - 18
IS  - 5
PB  - PLoS
CY  - San Fransisco
ER  - 
TY  - JOUR
A1  - Wang, Wei
A1  - Metzler, Ralf
A1  - Cherstvy, Andrey G.
T1  - Anomalous diffusion, aging, and nonergodicity of scaled Brownian motion with fractional Gaussian noise: overview of related experimental observations and models
JF  - Physical chemistry, chemical physics : PCCP ; a journal of European chemical societies
N2  - How does a systematic time-dependence of the diffusion coefficient D(t) affect the ergodic and statistical characteristics of fractional Brownian motion (FBM)? Here, we answer this question via studying the characteristics of a set of standard statistical quantifiers relevant to single-particle-tracking (SPT) experiments. We examine, for instance, how the behavior of the ensemble- and time-averaged mean-squared displacements-denoted as the standard MSD < x(2)(Delta)> and TAMSD <<(delta(2)(Delta))over bar>> quantifiers-of FBM featuring < x(2) (Delta >> = <<(delta(2)(Delta >)over bar>> proportional to Delta(2H) (where H is the Hurst exponent and Delta is the [lag] time) changes in the presence of a power-law deterministically varying diffusivity D-proportional to(t) proportional to t(alpha-1) -germane to the process of scaled Brownian motion (SBM)-determining the strength of fractional Gaussian noise. The resulting compound "scaled-fractional" Brownian motion or FBM-SBM is found to be nonergodic, with < x(2)(Delta >> proportional to Delta(alpha+)(2H)(-1) and <(delta 2(Delta >) over bar > proportional to Delta(2H). We also detect a stalling behavior of the MSDs for very subdiffusive SBM and FBM, when alpha + 2H - 1 < 0. The distribution of particle displacements for FBM-SBM remains Gaussian, as that for the parent processes of FBM and SBM, in the entire region of scaling exponents (0 < alpha < 2 and 0 < H < 1). The FBM-SBM process is aging in a manner similar to SBM. The velocity autocorrelation function (ACF) of particle increments of FBM-SBM exhibits a dip when the parent FBM process is subdiffusive. Both for sub- and superdiffusive FBM contributions to the FBM-SBM process, the SBM exponent affects the long-time decay exponent of the ACF. Applications of the FBM-SBM-amalgamated process to the analysis of SPT data are discussed. A comparative tabulated overview of recent experimental (mainly SPT) and computational datasets amenable for interpretation in terms of FBM-, SBM-, and FBM-SBM-like models of diffusion culminates the presentation. The statistical aspects of the dynamics of a wide range of biological systems is compared in the table, from nanosized beads in living cells, to chromosomal loci, to water diffusion in the brain, and, finally, to patterns of animal movements.
Y1  - 2022
U6  - https://doi.org/10.1039/d2cp01741e
SN  - 1463-9076
SN  - 1463-9084
VL  - 24
IS  - 31
SP  - 18482
EP  - 18504
PB  - RSC Publ.
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Cherstvy, Andrey G.
A1  - Safdari, Hadiseh
A1  - Metzler, Ralf
T1  - Anomalous diffusion, nonergodicity, and ageing for exponentially and logarithmically time-dependent diffusivity
BT  - striking differences for massive versus massless particles
JF  - Journal of physics. D, Applied physics
N2  - We investigate a diffusion process with a time-dependent diffusion coefficient, both exponentially increasing and decreasing in time, D(t)=D-0(e +/- 2 alpha t). For this (hypothetical) nonstationary diffusion process we compute-both analytically and from extensive stochastic simulations-the behavior of the ensemble- and time-averaged mean-squared displacements (MSDs) of the particles, both in the over- and underdamped limits. Simple asymptotic relations derived for the short- and long-time behaviors are shown to be in excellent agreement with the results of simulations. The diffusive characteristics in the presence of ageing are also considered, with dramatic differences of the over- versus underdamped regime. Our results for D(t)=D-0(e +/- 2 alpha t) extend and generalize the class of diffusive systems obeying scaled Brownian motion featuring a power-law-like variation of the diffusivity with time, D(t) similar to t(alpha-1). We also examine the logarithmically increasing diffusivity, D(t)=D(0)log[t/tau(0)], as another fundamental functional dependence (in addition to the power-law and exponential) and as an example of diffusivity slowly varying in time. One of the main conclusions is that the behavior of the massive particles is predominantly ergodic, while weak ergodicity breaking is repeatedly found for the time-dependent diffusion of the massless particles at short times. The latter manifests itself in the nonequivalence of the (both nonaged and aged) MSD and the mean time-averaged MSD. The current findings are potentially applicable to a class of physical systems out of thermal equilibrium where a rapid increase or decrease of the particles' diffusivity is inherently realized. One biological system potentially featuring all three types of time-dependent diffusion (power-law-like, exponential, and logarithmic) is water diffusion in the brain tissues, as we thoroughly discuss in the end.
KW  - anomalous diffusion
KW  - scaled Brownian motion
KW  - stochastic processes
KW  - nonstationary diffusivity
KW  - water diffusion in the brain
KW  - nonergodicity
Y1  - 2021
U6  - https://doi.org/10.1088/1361-6463/abdff0
SN  - 0022-3727
SN  - 1361-6463
VL  - 54
IS  - 19
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Reese, Ronja
A1  - Albrecht, Torsten
A1  - Mengel, Matthias
A1  - Asay-Davis, Xylar
A1  - Winkelmann, Ricarda
T1  - Antarctic sub-shelf melt rates via PICO
JF  - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union
N2  - Ocean-induced melting below ice shelves is one of the dominant drivers for mass loss from the Antarctic Ice Sheet at present. An appropriate representation of sub-shelf melt rates is therefore essential for model simulations of marine-based ice sheet evolution. Continental-scale ice sheet models often rely on simple melt-parameterizations, in particular for long-term simulations, when fully coupled ice-ocean interaction becomes computationally too expensive. Such parameterizations can account for the influence of the local depth of the ice-shelf draft or its slope on melting. However, they do not capture the effect of ocean circulation underneath the ice shelf. Here we present the Potsdam Ice-shelf Cavity mOdel (PICO), which simulates the vertical overturning circulation in ice-shelf cavities and thus enables the computation of sub-shelf melt rates consistent with this circulation. PICO is based on an ocean box model that coarsely resolves ice shelf cavities and uses a boundary layer melt formulation. We implement it as a module of the Parallel Ice Sheet Model (PISM) and evaluate its performance under present-day conditions of the Southern Ocean. We identify a set of parameters that yield two-dimensional melt rate fields that qualitatively reproduce the typical pattern of comparably high melting near the grounding line and lower melting or refreezing towards the calving front. PICO captures the wide range of melt rates observed for Antarctic ice shelves, with an average of about 0.1 ma(-1) for cold sub-shelf cavities, for example, underneath Ross or Ronne ice shelves, to 16 ma(-1) for warm cavities such as in the Amundsen Sea region. This makes PICO a computationally feasible and more physical alternative to melt parameterizations purely based on ice draft geometry.
Y1  - 2018
U6  - https://doi.org/10.5194/tc-12-1969-2018
SN  - 1994-0416
SN  - 1994-0424
VL  - 12
IS  - 6
SP  - 1969
EP  - 1985
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Pranav, Manasi
A1  - Hultzsch, Thomas
A1  - Musiienko, Artem
A1  - Sun, Bowen
A1  - Shukla, Atul
A1  - Jaiser, Frank
A1  - Shoaee, Safa
A1  - Neher, Dieter
T1  - Anticorrelated photoluminescence and free charge generation proves field-assisted exciton dissociation in low-offset PM6:Y5 organic solar cells
JF  - APL materials : high impact open access journal in functional materials science
N2  - Understanding the origin of inefficient photocurrent generation in organic solar cells with low energy offset remains key to realizing high-performance donor-acceptor systems. Here, we probe the origin of field-dependent free-charge generation and photoluminescence in wnon-fullereneacceptor (NFA)-based organic solar cells using the polymer PM6 and the NFA Y5-a non-halogenated sibling to Y6, with a smaller energetic offset to PM6. By performing time-delayed collection field (TDCF) measurements on a variety of samples with different electron transport layers and active layer thickness, we show that the fill factor and photocurrent are limited by field-dependent free charge generation in the bulk of the blend. We also introduce a new method of TDCF called m-TDCF to prove the absence of artifacts from non-geminate recombination of photogenerated and dark charge carriers near the electrodes. We then correlate free charge generation with steady-state photoluminescence intensity and find perfect anticorrelation between these two properties. Through this, we conclude that photocurrent generation in this low-offset system is entirely controlled by the field-dependent dissociation of local excitons into charge-transfer states. (c) 2023 Author(s).
Y1  - 2023
U6  - https://doi.org/10.1063/5.0151580
SN  - 2166-532X
VL  - 11
IS  - 6
PB  - AIP Publishing
CY  - Melville
ER  - 
TY  - JOUR
A1  - Rüdiger, Günther
A1  - Küker, Manfred
A1  - Kapyla, P. J.
A1  - Strassmeier, Klaus G.
T1  - Antisolar differential rotation of slowly rotating cool stars
JF  - Astronomy and astrophysics : an international weekly journal
N2  - Rotating stellar convection transports angular momentum towards the equator, generating the characteristic equatorial acceleration of the solar rotation while the radial flux of angular momentum is always inwards. New numerical box simulations for the meridional cross-correlation < u(theta)u(phi)>, however, reveal the angular momentum transport towards the poles for slow rotation and towards the equator for fast rotation. The explanation is that for slow rotation a negative radial gradient of the angular velocity always appears, which in combination with a so-far neglected rotation-induced off-diagonal eddy viscosity term nu(perpendicular to) provides "antisolar rotation" laws with a decelerated equator Similarly, the simulations provided positive values for the rotation-induced correlation < u(r)u(theta)>, which is relevant for the resulting latitudinal temperature profiles (cool or warm poles) for slow rotation and negative values for fast rotation. Observations of the differential rotation of slowly rotating stars will therefore lead to a better understanding of the actual stress-strain relation, the heat transport, and the underlying model of the rotating convection.
KW  - stars: solar-type
KW  - convection
KW  - stars: rotation
KW  - turbulence
Y1  - 2019
U6  - https://doi.org/10.1051/0004-6361/201935280
SN  - 1432-0746
VL  - 630
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Doerries, Timo J.
A1  - Chechkin, Aleksei V.
A1  - Metzler, Ralf
T1  - Apparent anomalous diffusion and non-Gaussian distributions in a simple mobile-immobile transport model with Poissonian switching
JF  - Interface : journal of the Royal Society
N2  - We analyse mobile-immobile transport of particles that switch between the mobile and immobile phases with finite rates. Despite this seemingly simple assumption of Poissonian switching, we unveil a rich transport dynamics including significant transient anomalous diffusion and non-Gaussian displacement distributions. Our discussion is based on experimental parameters for tau proteins in neuronal cells, but the results obtained here are expected to be of relevance for a broad class of processes in complex systems. Specifically, we obtain that, when the mean binding time is significantly longer than the mean mobile time, transient anomalous diffusion is observed at short and intermediate time scales, with a strong dependence on the fraction of initially mobile and immobile particles. We unveil a Laplace distribution of particle displacements at relevant intermediate time scales. For any initial fraction of mobile particles, the respective mean squared displacement (MSD) displays a plateau. Moreover, we demonstrate a short-time cubic time dependence of the MSD for immobile tracers when initially all particles are immobile.
KW  - diffusion
KW  - mobile-immobile model
KW  - tau proteins
Y1  - 2022
U6  - https://doi.org/10.1098/rsif.2022.0233
SN  - 1742-5689
SN  - 1742-5662
VL  - 19
IS  - 192
PB  - Royal Society
CY  - London
ER  - 
TY  - JOUR
A1  - Karamzadeh Toularoud, Nasim
A1  - Heimann, Sebastian
A1  - Dahm, Torsten
A1  - Krüger, Frank
T1  - Application based seismological array design by seismicity scenario modelling
JF  - Geophysical journal international
N2  - The design of an array configuration is an important task in array seismology during experiment planning. Often the array response function (ARF), which depends on the relative position of array stations and frequency content of the incoming signals, is used as the array design criterion. In practice, additional constraints and parameters have to be taken into account, for example, land ownership, site-specific noise levels or characteristics of the seismic sources under investigation. In this study, a flexible array design framework is introduced that implements a customizable scenario modelling and optimization scheme by making use of synthetic seismograms. Using synthetic seismograms to evaluate array performance makes it possible to consider additional constraints. We suggest to use synthetic array beamforming as an array design criterion instead of the ARF. The objective function of the optimization scheme is defined according to the monitoring goals, and may consist of a number of subfunctions. The array design framework is exemplified by designing a seven-station small-scale array to monitor earthquake swarm activity in Northwest Bohemia/Vogtland in central Europe. Two subfunctions are introduced to verify the accuracy of horizontal slowness estimation; one to suppress aliasing effects due to possible secondary lobes of synthetic array beamforming calculated in horizontal slowness space and the other to reduce the event’s mislocation caused by miscalculation of the horizontal slowness vector. Subsequently, a weighting technique is applied to combine the subfunctions into one single scalar objective function to use in the optimization process.
KW  - Array Seismology
KW  - Array design
KW  - Seismicity modelling
Y1  - 2018
SN  - 0956-540X
SN  - 1365-246X
VL  - 216
IS  - 3
SP  - 1711
EP  - 1727
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Stolterfoht, Martin
A1  - Wolff, Christian Michael
A1  - Amir, Yohai
A1  - Paulke, Andreas
A1  - Perdigón-Toro, Lorena
A1  - Caprioglio, Pietro
A1  - Neher, Dieter
T1  - Approaching the fill factor Shockley-Queisser limit in stable, dopant-free triple cation perovskite solar cells
JF  - Energy & Environmental Science
N2  - Perovskite solar cells now compete with their inorganic counterparts in terms of power conversion efficiency, not least because of their small open-circuit voltage (V-OC) losses. A key to surpass traditional thin-film solar cells is the fill factor (FF). Therefore, more insights into the physical mechanisms that define the bias dependence of the photocurrent are urgently required. In this work, we studied charge extraction and recombination in efficient triple cation perovskite solar cells with undoped organic electron/hole transport layers (ETL/HTL). Using integral time of flight we identify the transit time through the HTL as the key figure of merit for maximizing the fill factor (FF) and efficiency. Complementarily, intensity dependent photocurrent and V-OC measurements elucidate the role of the HTL on the bias dependence of non-radiative and transport-related loss channels. We show that charge transport losses can be completely avoided under certain conditions, yielding devices with FFs of up to 84%. Optimized cells exhibit power conversion efficiencies of above 20% for 6 mm(2) sized pixels and 18.9% for a device area of 1 cm(2). These are record efficiencies for hybrid perovskite devices with dopant-free transport layers, highlighting the potential of this device technology to avoid charge-transport limitations and to approach the Shockley-Queisser limit.
Y1  - 2017
U6  - https://doi.org/10.1039/c7ee00899f
SN  - 1754-5692
SN  - 1754-5706
VL  - 10
SP  - 1530
EP  - 1539
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Padash, Amin
A1  - Sandev, Trifce
A1  - Kantz, Holger
A1  - Metzler, Ralf
A1  - Chechkin, Aleksei
T1  - Asymmetric Levy flights are more efficient in random search
JF  - Fractal and fractional
N2  - We study the first-arrival (first-hitting) dynamics and efficiency of a one-dimensional random search model performing asymmetric Levy flights by leveraging the Fokker-Planck equation with a delta-sink and an asymmetric space-fractional derivative operator with stable index alpha and asymmetry (skewness) parameter beta. 

We find exact analytical results for the probability density of first-arrival times and the search efficiency, and we analyse their behaviour within the limits of short and long times. 
We find that when the starting point of the searcher is to the right of the target, random search by Brownian motion is more efficient than Levy flights with beta <= 0 (with a rightward bias) for short initial distances, while for beta>0 (with a leftward bias) Levy flights with alpha -> 1 are more efficient. 

When increasing the initial distance of the searcher to the target, Levy flight search (except for alpha=1 with beta=0) is more efficient than the Brownian search. Moreover, the asymmetry in jumps leads to essentially higher efficiency of the Levy search compared to symmetric Levy flights at both short and long distances, and the effect is more pronounced for stable indices alpha close to unity.
KW  - asymmetric Levy flights
KW  - first-arrival density
KW  - search efficiency
Y1  - 2022
U6  - https://doi.org/10.3390/fractalfract6050260
SN  - 2504-3110
VL  - 6
IS  - 5
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Omel'chenko, Oleh
A1  - Ocampo-Espindola, Jorge Luis
A1  - Kiss, István Z.
T1  - Asymmetry-induced isolated fully synchronized state in coupled oscillator populations
JF  - Physical review : E, Statistical, nonlinear and soft matter physics
N2  - A symmetry-breaking mechanism is investigated that creates bistability between fully and partially synchronized states in oscillator networks. Two populations of oscillators with unimodal frequency distribution and different amplitudes, in the presence of weak global coupling, are shown to simplify to a modular network with asymmetrical coupling. With increasing the coupling strength, a synchronization transition is observed with an isolated fully synchronized state. The results are interpreted theoretically in the thermodynamic limit and confirmed in experiments with chemical oscillators.
Y1  - 2021
U6  - https://doi.org/10.1103/PhysRevE.104.L022202
SN  - 2470-0045
SN  - 2470-0053
VL  - 104
IS  - 2
PB  - American Physical Society
CY  - Melville, NY
ER  - 
TY  - JOUR
A1  - Janowski, Marcin Andrzej
A1  - Zoschke, Reimo
A1  - Scharff, Lars B.
A1  - Jaime, Silvia Martinez
A1  - Ferrari, Camilla
A1  - Proost, Sebastian
A1  - Xiong, Jonathan Ng Wei
A1  - Omranian, Nooshin
A1  - Musialak-Lange, Magdalena
A1  - Nikoloski, Zoran
A1  - Graf, Alexander
A1  - Schoettler, Mark Aurel
A1  - Sampathkumar, Arun
A1  - Vaid, Neha
A1  - Mutwil, Marek
T1  - AtRsgA from Arabidopsis thaliana is important for maturation of the small subunit of the chloroplast ribosome
JF  - The plant journal
N2  - Plastid ribosomes are very similar in structure and function to the ribosomes of their bacterial ancestors. Since ribosome biogenesis is not thermodynamically favorable under biological conditions it requires the activity of many assembly factors. Here we have characterized a homolog of bacterial RsgA in Arabidopsis thaliana and show that it can complement the bacterial homolog. Functional characterization of a strong mutant in Arabidopsis revealed that the protein is essential for plant viability, while a weak mutant produced dwarf, chlorotic plants that incorporated immature pre-16S ribosomal RNA into translating ribosomes. Physiological analysis of the mutant plants revealed smaller, but more numerous, chloroplasts in the mesophyll cells, reduction of chlorophyll a and b, depletion of proplastids from the rib meristem and decreased photosynthetic electron transport rate and efficiency. Comparative RNA sequencing and proteomic analysis of the weak mutant and wild-type plants revealed that various biotic stress-related, transcriptional regulation and post-transcriptional modification pathways were repressed in the mutant. Intriguingly, while nuclear- and chloroplast-encoded photosynthesis-related proteins were less abundant in the mutant, the corresponding transcripts were increased, suggesting an elaborate compensatory mechanism, potentially via differentially active retrograde signaling pathways. To conclude, this study reveals a chloroplast ribosome assembly factor and outlines the transcriptomic and proteomic responses of the compensatory mechanism activated during decreased chloroplast function. Significance Statement AtRsgA is an assembly factor necessary for maturation of the small subunit of the chloroplast ribosome. Depletion of AtRsgA leads to dwarfed, chlorotic plants, a decrease of mature 16S rRNA and smaller, but more numerous, chloroplasts. Large-scale transcriptomic and proteomic analysis revealed that chloroplast-encoded and -targeted proteins were less abundant, while the corresponding transcripts were increased in the mutant. We analyze the transcriptional responses of several retrograde signaling pathways to suggest the mechanism underlying this compensatory response.
KW  - ribosome assembly
KW  - chloroplast ribosome
KW  - assembly factor
KW  - 30S subunit
KW  - RsgA
KW  - Arabidopsis thaliana
Y1  - 2018
U6  - https://doi.org/10.1111/tpj.14040
SN  - 0960-7412
SN  - 1365-313X
VL  - 96
IS  - 2
SP  - 404
EP  - 420
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Merchel, Silke
A1  - Gärtner, Andreas
A1  - Beutner, Sabrina
A1  - Bookhagen, Bodo
A1  - Chabilan, Amelie
T1  - Attempts to understand potential deficiencies in chemical procedures for AMS: Cleaning and dissolving quartz for Be-10 and Al-26 analysis
JF  - Nuclear instruments & methods in physics research : a journal on accelerators, instrumentation and techniques applied to research in nuclear and atomic physics, materials science and related fields in physics, Section B, Beam interactions with materials and atoms
N2  - The purity of the analysed samples (e.g. quartz) with respect to chemical composition and radionuclide contamination is essential for geomorphologic applications using so-called terrestrial cosmogenic nuclides (TCNs). To guarantee this, numerous cleaning and dissolution procedures have been developed. At the DREsden Accelerator Mass Spectrometry (DREAMS) facility, we also work on enhancing the chemical quartz-enrichment methodology from bulk rock and dissolution of quartz. Repeated exposure of the bulk material to acid mixtures (HCl/H2SiF6) at room temperature for cleaning and its monitoring by optical microscopy works for most quartz-rich samples. The quartz dissolution in HF under rather mild conditions (at room temperature on a shaker-table) has the advantage to leave difficult-to-dissolve minerals (e.g., tourmaline, zircon, rutile, sillimanite, kyanite, chromite, corundum), not separated by other physical methods before, as residue. Our comparison with a high-temperature dissolution method (in a microwave) indicates an additional amount of interfering elements, such as in average about 3 mg of Ti, more than 7 mg of Al, and about 22 mu g of Be (for 50 g SiO2), is added to the sample, hence showing the superiority of our mild method. This way, we reduce problems for chemistry and AMS, but also ensure better comparability to production rates of cleaner stoichiometric quartz from calibration sites.
KW  - Accelerator mass spectrometry
KW  - In-situ
KW  - Terrestrial cosmogenic nuclide
KW  - Residue
KW  - Quartz
Y1  - 2019
U6  - https://doi.org/10.1016/j.nimb.2019.02.007
SN  - 0168-583X
SN  - 1872-9584
VL  - 455
SP  - 293
EP  - 299
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Zacharias, Michael
A1  - Chen, Xuhui
A1  - Wagner, Stefan
T1  - Attenuation of TeV gamma-rays by the starlight photon field of the host galaxy
JF  - Monthly notices of the Royal Astronomical Society
N2  - The absorption of TeV gamma-ray photons produced in relativistic jets by surrounding soft photon fields is a long-standing problem of jet physics. In some cases, the most likely emission site close to the central black hole is ruled out because of the high opacity caused by strong optical and infrared photon sources, such as the broad-line region. Mostly neglected for jet modelling is the absorption of gamma-rays in the starlight photon field of the host galaxy. Analysing the absorption for arbitrary locations and observation angles of the gamma-ray emission site within the host galaxy, we find that the distance to the galaxy centre, the observation angle, and the distribution of starlight in the galaxy are crucial for the amount of absorption. We derive the absorption value for a sample of 20 TeV-detected blazars with a redshift z(r) < 0.2. The absorption value of the gamma-ray emission located in the galaxy centre may be as high as 20 per cent, with an average value of 6 per cent. This is important in order to determine the intrinsic blazar parameters. We see no significant trends in our sample between the degree of absorption and host properties, such as starlight emissivity, galactic size, half-light radius, and redshift. While the uncertainty of the spectral properties of the extragalactic background light exceeds the effect of absorption by stellar light from the host galaxy in distant objects, the latter is a dominant effect in nearby sources. It may also be revealed in a differential comparison of sources with similar redshifts.
KW  - opacity
KW  - radiation mechanisms: non-thermal
KW  - galaxies: active
KW  - gamma-rays: galaxies
Y1  - 2016
U6  - https://doi.org/10.1093/mnras/stw3032
SN  - 0035-8711
SN  - 1365-2966
VL  - 465
IS  - 3
SP  - 3767
EP  - 3774
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Gerlach, Marius
A1  - Preitschopf, Tobias
A1  - Karaev, Emil
A1  - Quitian-Lara, Heidy Mayerly
A1  - Mayer, Dennis
A1  - Bozek, John
A1  - Fischer, Ingo
A1  - Fink, Reinhold F.
T1  - Auger electron spectroscopy of fulminic acid, HCNO
BT  - an experimental and theoretical study
JF  - Physical chemistry, chemical physics : a journal of European Chemical Societies
N2  - HCNO is a molecule of considerable astrochemical interest as a precursor to prebiotic molecules. It is synthesized by preparative pyrolysis and is unstable at room temperature. Here, we investigate its spectroscopy in the soft X-ray regime at the C 1s, N 1s and O 1s edges. All 1s ionization energies are reported and X-ray absorption spectra reveal the transitions from the 1s to the pi* state. Resonant and normal Auger electron spectra for the decay of the core hole states are recorded in a hemispherical analyzer. An assignment of the experimental spectra is provided with the aid of theoretical counterparts. The latter are using a valence configuration interaction representation of the intermediate and final state energies and wavefunctions, the one-center approximation for transition rates and band shapes according to the moment theory. The computed spectra are in very good agreement with the experimental data and most of the relevant bands are assigned. Additionally, we present a simple approach to estimate relative Auger transition rates on the basis of a minimal basis representation of the molecular orbitals. We demonstrate that this provides a qualitatively good and reliable estimate for several signals in the normal and resonant Auger electron spectra which have significantly different intensities in the decay of the three core holes.
Y1  - 2022
U6  - https://doi.org/10.1039/d2cp02104h
SN  - 1463-9076
SN  - 1463-9084
VL  - 24
IS  - 25
SP  - 15217
EP  - 15229
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Stojkoski, Viktor
A1  - Sandev, Trifce
A1  - Kocarev, Ljupco
A1  - Pal, Arnab
T1  - Autocorrelation functions and ergodicity in diffusion with stochastic resetting
JF  - Journal of physics : A, Mathematical and theoretical
N2  - Diffusion with stochastic resetting is a paradigm of resetting processes. Standard renewal or master equation approach are typically used to study steady state and other transport properties such as average, mean squared displacement etc. 
What remains less explored is the two time point correlation functions whose evaluation is often daunting since it requires the implementation of the exact time dependent probability density functions of the resetting processes which are unknown for most of the problems. 

We adopt a different approach that allows us to write a stochastic solution for a single trajectory undergoing resetting. 
Moments and the autocorrelation functions between any two times along the trajectory can then be computed directly using the laws of total expectation. Estimation of autocorrelation functions turns out to be pivotal for investigating the ergodic properties of various observables for this canonical model. 
In particular, we investigate two observables (i) sample mean which is widely used in economics and (ii) time-averaged-mean-squared-displacement (TAMSD) which is of acute interest in physics. 

We find that both diffusion and drift-diffusion processes with resetting are ergodic at the mean level unlike their reset-free counterparts. In contrast, resetting renders ergodicity breaking in the TAMSD while both the stochastic processes are ergodic when resetting is absent. We quantify these behaviors with detailed analytical study and corroborate with extensive numerical simulations. 

Our results can be verified in experimental set-ups that can track single particle trajectories and thus have strong implications in understanding the physics of resetting.
KW  - autocorrelations
KW  - ergodicity
KW  - diffusion
KW  - stochastic resetting
Y1  - 2022
U6  - https://doi.org/10.1088/1751-8121/ac4ce9
SN  - 1751-8113
SN  - 1751-8121
VL  - 55
IS  - 10
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Perdigón-Toro, Lorena
A1  - Zhang, Huotian
A1  - Markina, Anastaa si
A1  - Yuan, Jun
A1  - Hosseini, Seyed Mehrdad
A1  - Wolff, Christian Michael
A1  - Zuo, Guangzheng
A1  - Stolterfoht, Martin
A1  - Zou, Yingping
A1  - Gao, Feng
A1  - Andrienko, Denis
A1  - Shoaee, Safa
A1  - Neher, Dieter
T1  - Barrierless free charge generation in the high-performance PM6:Y6 bulk heterojunction non-fullerene solar cell
JF  - Advanced materials
N2  - Organic solar cells are currently experiencing a second golden age thanks to the development of novel non-fullerene acceptors (NFAs). Surprisingly, some of these blends exhibit high efficiencies despite a low energy offset at the heterojunction. Herein, free charge generation in the high-performance blend of the donor polymer PM6 with the NFA Y6 is thoroughly investigated as a function of internal field, temperature and excitation energy. Results show that photocurrent generation is essentially barrierless with near-unity efficiency, regardless of excitation energy. Efficient charge separation is maintained over a wide temperature range, down to 100 K, despite the small driving force for charge generation. Studies on a blend with a low concentration of the NFA, measurements of the energetic disorder, and theoretical modeling suggest that CT state dissociation is assisted by the electrostatic interfacial field which for Y6 is large enough to compensate the Coulomb dissociation barrier.
KW  - driving force
KW  - non-fullerene acceptors
KW  - organic solar cells
KW  - photocurrent generation
Y1  - 2020
U6  - https://doi.org/10.1002/adma.201906763
SN  - 0935-9648
SN  - 1521-4095
VL  - 32
IS  - 9
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Thapa, Samudrajit
A1  - Lomholt, Michael Andersen
A1  - Krog, Jens
A1  - Cherstvy, Andrey G.
A1  - Metzler, Ralf
T1  - Bayesian analysis of single-particle tracking data using the nested-sampling algorithm: maximum-likelihood model selection applied to stochastic-diffusivity data
JF  - Physical chemistry, chemical physics : PCCP ; a journal of European Chemical Societies
N2  - We employ Bayesian statistics using the nested-sampling algorithm to compare and rank multiple models of ergodic diffusion (including anomalous diffusion) as well as to assess their optimal parameters for in silico-generated and real time-series. We focus on the recently-introduced model of Brownian motion with "diffusing diffusivity'-giving rise to widely-observed non-Gaussian displacement statistics-and its comparison to Brownian and fractional Brownian motion, also for the time-series with some measurement noise. We conduct this model-assessment analysis using Bayesian statistics and the nested-sampling algorithm on the level of individual particle trajectories. We evaluate relative model probabilities and compute best-parameter sets for each diffusion model, comparing the estimated parameters to the true ones. We test the performance of the nested-sampling algorithm and its predictive power both for computer-generated (idealised) trajectories as well as for real single-particle-tracking trajectories. Our approach delivers new important insight into the objective selection of the most suitable stochastic model for a given time-series. We also present first model-ranking results in application to experimental data of tracer diffusion in polymer-based hydrogels.
Y1  - 2018
U6  - https://doi.org/10.1039/c8cp04043e
SN  - 1463-9076
SN  - 1463-9084
VL  - 20
IS  - 46
SP  - 29018
EP  - 29037
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Seckler, Henrik
A1  - Metzler, Ralf
T1  - Bayesian deep learning for error estimation in the analysis of anomalous diffusion
JF  - Nature Communnications
N2  - Modern single-particle-tracking techniques produce extensive time-series of diffusive motion in a wide variety of systems, from single-molecule motion in living-cells to movement ecology. The quest is to decipher the physical mechanisms encoded in the data and thus to better understand the probed systems. We here augment recently proposed machine-learning techniques for decoding anomalous-diffusion data to include an uncertainty estimate in addition to the predicted output. To avoid the Black-Box-Problem a Bayesian-Deep-Learning technique named Stochastic-Weight-Averaging-Gaussian is used to train models for both the classification of the diffusionmodel and the regression of the anomalous diffusion exponent of single-particle-trajectories. Evaluating their performance, we find that these models can achieve a wellcalibrated error estimate while maintaining high prediction accuracies. In the analysis of the output uncertainty predictions we relate these to properties of the underlying diffusion models, thus providing insights into the learning process of the machine and the relevance of the output.
KW  - random-walk
KW  - models
Y1  - 2022
U6  - https://doi.org/10.1038/s41467-022-34305-6
SN  - 2041-1723
VL  - 13
PB  - Nature Publishing Group UK
CY  - London
ER  - 
TY  - JOUR
A1  - Seckler, Henrik
A1  - Metzler, Ralf
T1  - Bayesian deep learning for error estimation in the analysis of anomalous diffusion
JF  - Nature Communications
N2  - Modern single-particle-tracking techniques produce extensive time-series of diffusive motion in a wide variety of systems, from single-molecule motion in living-cells to movement ecology. The quest is to decipher the physical mechanisms encoded in the data and thus to better understand the probed systems. We here augment recently proposed machine-learning techniques for decoding anomalous-diffusion data to include an uncertainty estimate in addition to the predicted output. To avoid the Black-Box-Problem a Bayesian-Deep-Learning technique named Stochastic-Weight-Averaging-Gaussian is used to train models for both the classification of the diffusion model and the regression of the anomalous diffusion exponent of single-particle-trajectories. Evaluating their performance, we find that these models can achieve a well-calibrated error estimate while maintaining high prediction accuracies. In the analysis of the output uncertainty predictions we relate these to properties of the underlying diffusion models, thus providing insights into the learning process of the machine and the relevance of the output. <br /> Diffusive motions in complex environments such as living biological cells or soft matter systems can be analyzed with single-particle-tracking approaches, where accuracy of output may vary. The authors involve a machine-learning technique for decoding anomalous-diffusion data and provide an uncertainty estimate together with predicted output.
Y1  - 2022
U6  - https://doi.org/10.1038/s41467-022-34305-6
SN  - 2041-1723
VL  - 13
IS  - 1
PB  - Nature portfolio
CY  - Berlin
ER  - 
TY  - JOUR
A1  - Hou, Ru
A1  - Cherstvy, Andrey G.
A1  - Metzler, Ralf
A1  - Akimoto, Takuma
T1  - Biased continuous-time random walks for ordinary and equilibrium cases
BT  - facilitation of diffusion, ergodicity breaking and ageing
JF  - Physical chemistry, chemical physics : a journal of European Chemical Societies
N2  - We examine renewal processes with power-law waiting time distributions (WTDs) and non-zero drift via computing analytically and by computer simulations their ensemble and time averaged spreading characteristics. All possible values of the scaling exponent alpha are considered for the WTD psi(t) similar to 1/t(1+alpha). We treat continuous-time random walks (CTRWs) with 0 < alpha < 1 for which the mean waiting time diverges, and investigate the behaviour of the process for both ordinary and equilibrium CTRWs for 1 < alpha < 2 and alpha > 2. We demonstrate that in the presence of a drift CTRWs with alpha < 1 are ageing and non-ergodic in the sense of the non-equivalence of their ensemble and time averaged displacement characteristics in the limit of lag times much shorter than the trajectory length. In the sense of the equivalence of ensemble and time averages, CTRW processes with 1 < alpha < 2 are ergodic for the equilibrium and non-ergodic for the ordinary situation. Lastly, CTRW renewal processes with alpha > 2-both for the equilibrium and ordinary situation-are always ergodic. For the situations 1 < alpha < 2 and alpha > 2 the variance of the diffusion process, however, depends on the initial ensemble. For biased CTRWs with alpha > 1 we also investigate the behaviour of the ergodicity breaking parameter. In addition, we demonstrate that for biased CTRWs the Einstein relation is valid on the level of the ensemble and time averaged displacements, in the entire range of the WTD exponent alpha.
Y1  - 2018
U6  - https://doi.org/10.1039/c8cp01863d
SN  - 1463-9076
SN  - 1463-9084
VL  - 20
IS  - 32
SP  - 20827
EP  - 20848
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Feudel, Fred
A1  - Feudel, Ulrike
T1  - Bifurcations in rotating spherical shell convection under the influence of differential rotation
JF  - Chaos : an interdisciplinary journal of nonlinear science
N2  - The bifurcations of thermal convection in a rotating spherical shell heated from the inner sphere and driven by the buoyancy of a central gravity field are studied numerically. This model of spherical Rayleigh-Benard convection describes large-scale convection in planets and in the outer zones of celestial bodies. In this work, the influence of an additionally imposed differential rotation of the inner sphere with respect to the outer one on the heat transfer and, more generally, on the whole bifurcation structure is investigated. In addition to numerical simulations, path-following techniques are applied in order to compute both stable and unstable solution branches. The dynamics and the heat transfer are essentially determined by a global bifurcation, which we have identified as a homoclinic bifurcation that consists of a collision of a stable modulated rotating with an unstable rotating wave.
Y1  - 2021
U6  - https://doi.org/10.1063/5.0063113
SN  - 1054-1500
SN  - 1089-7682
VL  - 31
IS  - 11
PB  - AIP
CY  - Melville
ER  - 
TY  - JOUR
A1  - Bastian, Philipp U.
A1  - Yu, Leixiao
A1  - de Guereñu Kurganova, Anna Lopez
A1  - Haag, Rainer
A1  - Kumke, Michael Uwe
T1  - Bioinspired confinement of upconversion nanoparticles for improved performance in aqueous solution
JF  - The journal of physical chemistry : C, Nanomaterials and interfaces
N2  - The resonance energy transfer (RET) from NaYF4:Yb,Er upconverting nanoparticles (UNCPs) to a dye (5-carboxytetramethylrhodamine (TAMRA)) was investigated by photoluminescence experiments and microscale thermophoresis (MST). The dye was excited via RET from the UCNPs which was excited in the near-infrared (NIR). The change of the dye diffusion speed (free vs coupled) was investigated by MST. RET shows significant changes in the decay times of the dye as well as of the UCNPs. MST reveals significant changes in the diffusion speed. A unique amphiphilic coating polymer (customized mussel protein (CMP) polymer) for UCNP surface coating was used, which mimics blood protein adsorption and mussel food protein adhesion to transfer the UCNP into the aqueous phase and to allow surface functionalization. The CMP provides very good water dispersibility to the UCNPs and minimizes ligand exchange and subsequent UCNP aging reactions because of the interlinkage of the CMP on the UCNP surface. Moreover, CMP provides N-3-functional groups for dick chemistry-based functionalization demonstrated with the dye 5-carboxytetramethylrhodamine (TAMRA). This establishes the principle coupling scheme for suitable biomarkers such as antibodies. The CMP provides very stable aqueous UCNP dispersions that are storable up to 3 years in a fridge at 5 degrees C without dissolution or coagulation. The outstanding properties of CMP in shielding the UCNP from unwanted solvent effects is reflected in the distinct increase of the photoluminescence decay times after UCNP functionalization. The UCNP-to-TAMRA energy transfer is also spectroscopically investigated at low temperatures (4-200 K), revealing that one of the two green Er(III) emission bands contributes the major part to the energy transfer. The TAMRA fluorescence decay time increases by a factor of 9500 from 2.28 ns up to 22 mu s due to radiationless energy transfer from the UCNP after NIR excitation of the latter. This underlines the unique properties of CMP as a versatile capping ligand for distinctly improving the UCNPs' performance in aqueous solutions, for coupling of biomolecules, and for applications for in vitro and in vivo experiments using UCNPs as optical probes in life science applications.
Y1  - 2020
U6  - https://doi.org/10.1021/acs.jpcc.0c09798
SN  - 1932-7447
SN  - 1932-7455
VL  - 124
IS  - 52
SP  - 28623
EP  - 28635
PB  - American Chemical Society
CY  - Washington, DC
ER  - 
TY  - JOUR
A1  - Chaurasia, Swami Vivekanandji
A1  - Dietrich, Tim
A1  - Rosswog, Stephan
T1  - Black hole-neutron star simulations with the BAM code
BT  - first tests and simulations
JF  - Physical review : D, Particles, fields, gravitation, and cosmology
N2  - The first detections of black hole-neutron star mergers (GW200105 and GW200115) by the LIGO-Virgo-Kagra Collaboration mark a significant scientific breakthrough. The physical interpretation of pre- and postmerger signals requires careful cross-examination between observational and theoretical modelling results. Here we present the first set of black hole-neutron star simulations that were obtained with the numerical-relativity code BAM. Our initial data are constructed using the public LORENE spectral library, which employs an excision of the black hole interior. BAM, in contrast, uses the moving-puncture gauge for the evolution. Therefore, we need to "stuff" the black hole interior with smooth initial data to evolve the binary system in time. This procedure introduces constraint violations such that the constraint damping properties of the evolution system are essential to increase the accuracy of the simulation and in particular to reduce spurious center-of-mass drifts. Within BAM we evolve the Z4c equations and we compare our gravitational-wave results with those of the SXS collaboration and results obtained with the SACRA code. While we find generally good agreement with the reference solutions and phase differences less than or similar to 0.5 rad at the moment of merger, the absence of a clean convergence order in our simulations does not allow for a proper error quantification. We finally present a set of different initial conditions to explore how the merger of black hole neutron star systems depends on the involved masses, spins, and equations of state.
Y1  - 2021
U6  - https://doi.org/10.1103/PhysRevD.104.084010
SN  - 2470-0010
SN  - 2470-0029
VL  - 104
IS  - 8
PB  - American Physical Society
CY  - Ridge, NY
ER  - 
TY  - JOUR
A1  - Goldschmidt, Richard Janis
A1  - Pikovskij, Arkadij
A1  - Politi, Antonio
T1  - Blinking chimeras in globally coupled rotators
JF  - Chaos : an interdisciplinary journal of nonlinear science
N2  - In globally coupled ensembles of identical oscillators so-called chimera states can be observed. The chimera state is a symmetry-broken regime, where a subset of oscillators forms a cluster, a synchronized population, while the rest of the system remains a collection of nonsynchronized, scattered units. We describe here a blinking chimera regime in an ensemble of seven globally coupled rotators (Kuramoto oscillators with inertia). It is characterized by a death-birth process, where a long-term stable cluster of four oscillators suddenly dissolves and is very quickly reborn with a new reshuffled configuration. We identify three different kinds of rare blinking events and give a quantitative characterization by applying stability analysis to the long-lived chaotic state and to the short-lived regular regimes that arise when the cluster dissolves.
Y1  - 2019
U6  - https://doi.org/10.1063/1.5105367
SN  - 1054-1500
SN  - 1089-7682
VL  - 29
IS  - 7
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - JOUR
A1  - Krämer, Hauke Kai
A1  - Marwan, Norbert
T1  - Border effect corrections for diagonal line based recurrence quantification analysis measures
JF  - Modern physics letters : A, Particles and fields, gravitation, cosmology, nuclear physics
N2  - Recurrence Quantification Analysis (RQA) defines a number of quantifiers, which base upon diagonal line structures in the recurrence plot (RP). Due to the finite size of an RP, these lines can be cut by the borders of the RP and, thus, bias the length distribution of diagonal lines and, consequently, the line based RQA measures. In this letter we investigate the impact of the mentioned border effects and of the thickening of diagonal lines in an RP (caused by tangential motion) on the estimation of the diagonal line length distribution, quantified by its entropy. Although a relation to the Lyapunov spectrum is theoretically expected, the mentioned entropy yields contradictory results in many studies. Here we summarize correction schemes for both, the border effects and the tangential motion and systematically compare them to methods from the literature. We show that these corrections lead to the expected behavior of the diagonal line length entropy, in particular meaning zero values in case of a regular motion and positive values for chaotic motion. Moreover, we test these methods under noisy conditions, in order to supply practical tools for applied statistical research.
KW  - Recurrence plots
KW  - Recurrence quantification analysis
KW  - Shannon entropy
KW  - Dynamical invariants
Y1  - 2019
U6  - https://doi.org/10.1016/j.physleta.2019.125977
SN  - 0375-9601
SN  - 1873-2429
VL  - 383
IS  - 34
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Clavier, Pierre J.
T1  - Borel-Écalle resummation of a two-point function
JF  - Annales Henri Poincaré : a journal of theoretical and mathematical physics / ed. jointly by the Institut Henri Poincaré and by the Swiss Physical Society
N2  - We provide an overview of the tools and techniques of resurgence theory used in the Borel-ecalle resummation method, which we then apply to the massless Wess-Zumino model. Starting from already known results on the anomalous dimension of the Wess-Zumino model, we solve its renormalisation group equation for the two-point function in a space of formal series. We show that this solution is 1-Gevrey and that its Borel transform is resurgent. The Schwinger-Dyson equation of the model is then used to prove an asymptotic exponential bound for the Borel transformed two-point function on a star-shaped domain of a suitable ramified complex plane. This proves that the two-point function of the Wess-Zumino model is Borel-ecalle summable.
Y1  - 2021
U6  - https://doi.org/10.1007/s00023-021-01057-w
SN  - 1424-0637
SN  - 1424-0661
VL  - 22
IS  - 6
SP  - 2103
EP  - 2136
PB  - Springer
CY  - Cham
ER  - 
TY  - JOUR
A1  - Li, Tian-yi
A1  - Benduhn, Johannes
A1  - Li, Yue
A1  - Jaiser, Frank
A1  - Spoltore, Donato
A1  - Zeika, Olaf
A1  - Ma, Zaifei
A1  - Neher, Dieter
A1  - Vandewal, Koen
A1  - Leo, Karl
T1  - Boron dipyrromethene (BODIPY) with meso-perfluorinated alkyl substituents as near infrared donors in organic solar cells
JF  - Journal of materials chemistry : A, Materials for energy and sustainability
N2  - Three furan-fused BODIPYs were synthesized with perfluorinated methyl, ethyl and n-propyl groups on the meso-carbon. They were obtained with high yields by reacting the furan-fused 2-carboxylpyrrole in corresponding perfluorinated acid and anhydride. With the increase in perfluorinated alkyl chain length, the molecular packing in the single crystal is influenced, showing increasing stacking distance and decreasing slope angle. All the BODIPYs were characterized as intense absorbers in near infrared region in solid state, peaking at similar to 800 nm with absorption coefficient of over 280 000 cm(-1). Facilitated by high thermal stability, the furan-fused BODIPYs were employed in vacuum-deposited organic solar cells as electron donors. All devices exhibit PCE over 6.0% with the EQE maximum reaching 70% at similar to 790 nm. The chemical modification of the BODIPY donors have certain influence on the active layer morphology, and the highest PCE of 6.4% was obtained with a notably high jsc of 13.6 mA cm(-2). Sensitive EQE and electroluminance studies indicated that the energy losses generated by the formation of a charge transfer state and the radiative recombination at the donor-acceptor interface were comparable in the range of 0.14-0.19 V, while non-radiative recombination energy loss of 0.38 V was the main energy loss route resulting in the moderate V-oc of 0.76 V.
Y1  - 2018
U6  - https://doi.org/10.1039/c8ta06261g
SN  - 2050-7488
SN  - 2050-7496
VL  - 6
IS  - 38
SP  - 18583
EP  - 18591
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Reindl, Nicole
A1  - Rauch, Thomas
A1  - Miller Bertolami, Marcelo Miguel
A1  - Todt, Helge Tobias
A1  - Werner, K.
T1  - Breaking news from the HST
BT  - the central star of the Stingray Nebula is now returning towards the AGB
JF  - Monthly notices of the Royal Astronomical Society
N2  - SAO 244567 is a rare example of a star that allows us to witness stellar evolution in real time. Between 1971 and 1990, it changed from a B-type star into the hot central star of the Stingray Nebula. This observed rapid heating has been a mystery for decades, since it is in strong contradiction with the low mass of the star and canonical post-asymptotic giant branch (AGB) evolution. We speculated that SAO 244567 might have suffered from a late thermal pulse (LTP) and obtained new observations with Hubble Space Telescope (HST)/COS to follow the evolution of the surface properties of SAO 244567 and to verify the LTP hypothesis. Our non-LTE spectral analysis reveals that the star cooled significantly since 2002 and that its envelope is now expanding. Therefore, we conclude that SAO 244567 is currently on its way back towards the AGB, which strongly supports the LTP hypothesis. A comparison with state-of-the-art LTP evolutionary calculations shows that these models cannot fully reproduce the evolution of all surface parameters simultaneously, pointing out possible shortcomings of stellar evolution models. Thereby, SAO 244567 keeps on challenging stellar evolution theory and we highly encourage further investigations.
KW  - stars: AGB and post-AGB
KW  - stars: atmospheres
KW  - stars: evolution
Y1  - 2016
U6  - https://doi.org/10.1093/mnrasl/slw175
SN  - 0035-8711
SN  - 1365-2966
VL  - 464
SP  - L51
EP  - L55
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Eckert, Sebastian
A1  - Vaz da Cruz, Vinícius
A1  - Ochmann, Miguel
A1  - Ahnen, Inga von
A1  - Föhlisch, Alexander
A1  - Huse, Nils
T1  - Breaking the symmetry of pyrimidine
BT  - solvent effects and core-excited state dynamics
JF  - The journal of physical chemistry letters
N2  - Symmetry and its breaking crucially define the chemical properties of molecules and their functionality. Resonant inelastic X-ray scattering is a local electronic structure probe reporting on molecular symmetry and its dynamical breaking within the femtosecond scattering duration. Here, we study pyrimidine, a system from the C-2v point group, in an aqueous solution environment, using scattering though its 2a(2) resonance. Despite the absence of clean parity selection rules for decay transitions from in-plane orbitals, scattering channels including decay from the 7b(2) and 11a(1) orbitals with nitrogen lone pair character are a direct probe for molecular symmetry. Computed spectra of explicitly solvated molecules sampled from a molecular dynamics simulation are combined with the results of a quantum dynamical description of the X-ray scattering process. We observe dominant signatures of core-excited Jahn-Teller induced symmetry breaking for resonant excitation. Solvent contributions are separable by shortening of the effective scattering duration through excitation energy detuning.
Y1  - 2021
U6  - https://doi.org/10.1021/acs.jpclett.1c01865
SN  - 1948-7185
VL  - 12
IS  - 35
SP  - 8637
EP  - 8643
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Bolotov, Maxim I.
A1  - Smirnov, Lev A.
A1  - Osipov, Grigory V.
A1  - Pikovskij, Arkadij
T1  - Breathing chimera in a system of phase oscillators
JF  - JETP Letters
N2  - Chimera states consisting of synchronous and asynchronous domains in a medium of nonlinearly coupled phase oscillators have been considered. Stationary inhomogeneous solutions of the Ott-Antonsen equation for a complex order parameter that correspond to fundamental chimeras have been constructed. The direct numerical simulation has shown that these structures under certain conditions are transformed to oscillatory (breathing) chimera regimes because of the development of instability.
Y1  - 2017
U6  - https://doi.org/10.1134/S0021364017180059
SN  - 0021-3640
SN  - 1090-6487
VL  - 106
SP  - 393
EP  - 399
PB  - Pleiades Publ.
CY  - New York
ER  - 
TY  - JOUR
A1  - Metzler, Ralf
T1  - Brownian motion and beyond: first-passage, power spectrum, non-Gaussianity, and anomalous diffusion
JF  - Journal of statistical mechanics: theory and experiment
N2  - Brownian motion is a ubiquitous physical phenomenon across the sciences. After its discovery by Brown and intensive study since the first half of the 20th century, many different aspects of Brownian motion and stochastic processes in general have been addressed in Statistical Physics. In particular, there now exists a very large range of applications of stochastic processes in various disciplines. Here we provide a summary of some of the recent developments in the field of stochastic processes, highlighting both the experimental findings and theoretical frameworks.
KW  - 15
KW  - 4
Y1  - 2019
U6  - https://doi.org/10.1088/1742-5468/ab4988
SN  - 1742-5468
VL  - 2019
IS  - 11
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Emanuel, Marc D.
A1  - Cherstvy, Andrey G.
A1  - Metzler, Ralf
A1  - Gompper, Gerhard
T1  - Buckling transitions and soft-phase invasion of two-component icosahedral shells
JF  - Physical review / publ. by The American Physical Society. E, Statistical, nonlinear, and soft matter physics
N2  - What is the optimal distribution of two types of crystalline phases on the surface of icosahedral shells, such as of many viral capsids? We here investigate the distribution of a thin layer of soft material on a crystalline convex icosahedral shell. We demonstrate how the shapes of spherical viruses can be understood from the perspective of elasticity theory of thin two-component shells. We develop a theory of shape transformations of an icosahedral shell upon addition of a softer, but still crystalline, material onto its surface. We show how the soft component "invades" the regions with the highest elastic energy and stress imposed by the 12 topological defects on the surface. We explore the phase diagram as a function of the surface fraction of the soft material, the shell size, and the incommensurability of the elastic moduli of the rigid and soft phases. We find that, as expected, progressive filling of the rigid shell by the soft phase starts from the most deformed regions of the icosahedron. With a progressively increasing soft-phase coverage, the spherical segments of domes are filled first (12 vertices of the shell), then the cylindrical segments connecting the domes (30 edges) are invaded, and, ultimately, the 20 flat faces of the icosahedral shell tend to be occupied by the soft material. We present a detailed theoretical investigation of the first two stages of this invasion process and develop a model of morphological changes of the cone structure that permits noncircular cross sections. In conclusion, we discuss the biological relevance of some structures predicted from our calculations, in particular for the shape of viral capsids.
Y1  - 2020
U6  - https://doi.org/10.1103/PhysRevE.102.062104
SN  - 2470-0045
SN  - 2470-0053
SN  - 2470-0061
SN  - 1538-4519
VL  - 102
IS  - 6
PB  - Woodbury
CY  - New York
ER  - 
TY  - JOUR
A1  - Franović, Igor
A1  - Omel'chenko, Oleh
A1  - Wolfrum, Matthias
T1  - Bumps, chimera states, and Turing patterns in systems of coupled active rotators
JF  - Physical review : E, Statistical, nonlinear and soft matter physics
N2  - Self-organized coherence-incoherence patterns, called chimera states, have first been reported in systems of Kuramoto oscillators. For coupled excitable units, similar patterns where coherent units are at rest are called bump states. Here, we study bumps in an array of active rotators coupled by nonlocal attraction and global repulsion. We demonstrate how they can emerge in a supercritical scenario from completely coherent Turing patterns: a single incoherent unit appears in a homoclinic bifurcation, undergoing subsequent transitions to quasiperiodic and chaotic behavior, which eventually transforms into extensive chaos with many incoherent units. We present different types of transitions and explain the formation of coherence-incoherence patterns according to the classical paradigm of short-range activation and long-range inhibition.
Y1  - 2021
U6  - https://doi.org/10.1103/PhysRevE.104.L052201
SN  - 2470-0045
SN  - 2470-0053
VL  - 104
IS  - 5
PB  - American Physical Society
CY  - College Park
ER  -