TY  - JOUR
A1  - Kim, Kyung-Chan
A1  - Shprits, Yuri Y.
T1  - Survey of the Favorable Conditions for Magnetosonic Wave Excitation
JF  - Journal of geophysical research : Space physics
N2  - The ratio of the proton ring velocity (VR) to the local Alfven speed (VA), in addition to proton ring distributions, plays a key factor in the excitation of magnetosonic waves at frequencies between the proton cyclotron frequency fcp and the lower hybrid resonance frequency fLHR in the Earth's magnetosphere. Here we investigate whether there is a statistically significant relationship between occurrences of proton rings and magnetosonic waves both outside and inside the plasmapause using particle and wave data from Van Allen Probe-A during the time period of October 2012 to December 2015. We also perform a statistical survey of the ratio of the ring energy (ER, corresponding to VR) to the Alfven energy (EA, corresponding to VA) to determine the favorable conditions under which magnetosonic waves in each of two frequency bands (fcp < f ≤ 0.5 fLHR and 0.5 fLHR < f < fLHR) can be excited. The results show that the magnetosonic waves in both frequency bands occur around the postnoon (12–18 magnetic local time, MLT) sector outside the plasmapause when ER is comparable to or lower than EA, and those in lower-frequency bands (fcp < f ≤ 0.5 fLHR) occur around the postnoon sector inside the plasmapause when ER/EA > ~9. However, there is one discrepancy between occurrences of proton rings and magnetosonic waves in low-frequency bands around the prenoon sector (6–12 MLT) outside the plasmapause, which suggests either that the waves may have propagated during active time from the postnoon sector after being excited during quiet time, or they may have locally excited in the prenoon sector during active time.
Y1  - 2018
U6  - https://doi.org/10.1002/2017JA024865
SN  - 2169-9380
SN  - 2169-9402
VL  - 123
IS  - 1
SP  - 400
EP  - 413
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Utecht, Manuel Martin
A1  - Klamroth, Tillmann
T1  - Local resonances in STM manipulation of chlorobenzene on Si(111)-7x7
BT  - performance of different cluster models and density functionals
JF  - Molecular physics
N2  - Hot localised charge carriers on the Si(111)-7x7 surface are modelled by small charged clusters. Such resonances induce non-local desorption, i.e. more than 10 nm away from the injection site, of chlorobenzene in scanning tunnelling microscope experiments. We used such a cluster model to characterise resonance localisation and vibrational activation for positive and negative resonances recently. In this work, we investigate to which extent the model depends on details of the used cluster or quantum chemistry methods and try to identify the smallest possible cluster suitable for a description of the neutral surface and the ion resonances. Furthermore, a detailed analysis for different chemisorption orientations is performed. While some properties, as estimates of the resonance energy or absolute values for atomic changes, show such a dependency, the main findings are very robust with respect to changes in the model and/or the chemisorption geometry. [GRAPHICS] .
KW  - DFT
KW  - cluster model
KW  - charge localisation
KW  - STM
Y1  - 2018
U6  - https://doi.org/10.1080/00268976.2018.1442939
SN  - 0026-8976
SN  - 1362-3028
VL  - 116
IS  - 13
SP  - 1687
EP  - 1696
PB  - Routledge, Taylor & Francis Group
CY  - Abingdon
ER  - 
TY  - JOUR
A1  - Martinez-Chicharro, M.
A1  - Torrejon, J. M.
A1  - Oskinova, Lida
A1  - Furst, F.
A1  - Postnov, K.
A1  - Rodes-Roca, J. J.
A1  - Hainich, Rainer
A1  - Bodaghee, A.
T1  - Evidence of Compton cooling during an X-ray flare supports a neutron star nature of the compact object in 4U1700-37
JF  - Monthly notices of the Royal Astronomical Society
N2  - Based on new Chandra X-ray telescope data, we present empirical evidence of plasma Compton cooling during a flare in the non-pulsating massive X-ray binary 4U1700-37. This behaviour might be explained by quasi-spherical accretion on to a slowly rotating magnetized neutron star (NS). In quiescence, the NS in 4U1700-37 is surrounded by a hot radiatively cooling shell. Its presence is supported by the detection of mHz quasi-periodic oscillations likely produced by its convection cells. The high plasma temperature and the relatively low X-ray luminosity observed during the quiescence, point to a small emitting area similar to 1 km, compatible with a hotspot on an NS surface. The sudden transition from a radiative to a significantly more efficient Compton cooling regime triggers an episode of enhanced accretion resulting in a flare. During the flare, the plasma temperature drops quickly. The predicted luminosity for such transitions, similar to 3 x 10(35) erg s(-1), is very close to the luminosity of 4U1700-37 during quiescence. The transition may be caused by the accretion of a clump in the stellar wind of the donor star. Thus, a magnetized NS nature of the compact object is strongly favoured.
KW  - stars: individual: 4U1700-37
KW  - V*V884 Sco
KW  - X-rays: binaries
Y1  - 2017
U6  - https://doi.org/10.1093/mnrasl/slx165
SN  - 0035-8711
SN  - 1365-2966
VL  - 473
IS  - 1
SP  - L74
EP  - L78
PB  - Oxford Univ. Press
CY  - Oxford
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  - Thiede, Tobias
A1  - Cabeza, Sandra
A1  - Mishurova, Tatiana
A1  - Nadammal, Naresh
A1  - Kromm, Arne
A1  - Bode, Johannes
A1  - Haberland, Christoph
A1  - Bruno, Giovanni
T1  - Residual Stress in Selective Laser Melted Inconel 718
BT  - Influence of the Removal from Base Plate and Deposition Hatch Length
JF  - Materials performance and characterization
N2  - The residual stress distribution in IN718 elongated prisms produced by selective laser melting was studied by means of neutron (bulk) and laboratory X-ray (surface) diffraction. Two deposition hatch lengths were considered. A horizontal plane near the top surface (perpendicular to the building direction) and a vertical plane near the lateral surface (parallel to the building direction) were investigated. Samples both in as-built (AB) condition and removed from the base plate (RE) were characterized. While surface stress fields seem constant for the AB condition, X-ray diffraction shows stress gradients along the hatch direction in the RE condition. The stress profiles correlate with the distortion maps obtained by tactile probe measurements. Neutron diffraction shows bulk stress gradients for all principal components along the main sample directions. We correlate the observed stress patterns with the hatch length, i.e., with its effect on temperature gradients and heat flow. The bulk stress gradients partially disappear after removal from the base plate.
KW  - residual stress
KW  - IN718
KW  - neutron diffraction
KW  - laboratory x-ray diffraction
KW  - additive manufacturing
KW  - selective laser melting
KW  - coordinate measurement machine
Y1  - 2018
U6  - https://doi.org/10.1520/MPC20170119
SN  - 2379-1365
SN  - 2165-3992
VL  - 7
IS  - 4
SP  - 717
EP  - 735
PB  - American Society for Testing and Materials
CY  - West Conshohocken
ER  - 
TY  - JOUR
A1  - Kretschmer, Marlene
A1  - Coumou, Dim
A1  - Agel, Laurie
A1  - Barlow, Mathew
A1  - Tziperman, Eli
A1  - Cohen, Judah
T1  - More-Persistent weak stratospheric polar vortex states linked to cold extremes
JF  - Bulletin of the American Meteorological Society
N2  - The extratropical stratosphere in boreal winter is characterized by a strong circumpolar westerly jet, confining the coldest temperatures at high latitudes. The jet, referred to as the stratospheric polar vortex, is predominantly zonal and centered around the pole; however, it does exhibit large variability in wind speed and location. Previous studies showed that a weak stratospheric polar vortex can lead to cold-air outbreaks in the midlatitudes, but the exact relationships and mechanisms are unclear. Particularly, it is unclear whether stratospheric variability has contributed to the observed anomalous cooling trends in midlatitude Eurasia. Using hierarchical clustering, we show that over the last 37 years, the frequency of weak vortex states in mid- to late winter (January and February) has increased, which was accompanied by subsequent cold extremes in midlatitude Eurasia. For this region, 60% of the observed cooling in the era of Arctic amplification, that is, since 1990, can be explained by the increased frequency of weak stratospheric polar vortex states, a number that increases to almost 80% when El Nino-Southern Oscillation (ENSO) variability is included as well.
Y1  - 2018
U6  - https://doi.org/10.1175/BAMS-D-16-0259.1
SN  - 0003-0007
SN  - 1520-0477
VL  - 99
IS  - 1
SP  - 49
EP  - 60
PB  - American Meteorological Soc.
CY  - Boston
ER  - 
TY  - JOUR
A1  - Ryll, Britta
A1  - Schmitz, Andreas
A1  - de Boor, Johannes
A1  - Franz, Alexandra
A1  - Whitfield, Pamela S.
A1  - Reehuis, Manfred
A1  - Hoser, Andreas
A1  - Müller, Eckhard
A1  - Habicht, Klaus
A1  - Fritscht, Katharina
T1  - Structure, phase composition, and thermoelectric properties of YbxCo4Sb12 and their dependence on synthesis method
JF  - ACS applied energy materials
N2  - We present a combined microscopic and macroscopic study of YbxCo4Sb12 skutterudites for a range of nominal filling fractions, 0.15 < x < 0.75. The samples were synthesized using two different methods — a melt–quench–annealing route in evacuated quartz ampoules and a non-equilibrium ball-mill route — for which we directly compare the crystal structure and phase composition as well as the thermoelectric properties. Rietveld refinements of high-quality neutron powder diffraction data reveal about a 30–40% smaller Yb occupancy on the crystallographic 2a site than nominally expected for both synthesis routes. We observe a maximum filling fraction of at least 0.439(7) for a sample synthesized by the ball-mill routine, exceeding theoretical predictions of the filling fraction limit of 0.2–0.3. A single secondary phase of CoSb2 is observed in ball-mill-synthesized samples, while two secondary phases, CoSb2 and YbSb2, are detected for samples prepared by the ampoule route. A detrimental influence of the secondary phases on the thermoelectric properties is observed for secondary-phase fractions larger than 8 wt % regardless of the kind of secondary phase. The largest figure of merit of all samples with a ZT ∼ 1.0 at 723 K is observed for the sample with a refined Yb content of x2a = 0.159(3), synthesized by the ampoule route.
KW  - thermoelectric materials
KW  - skutterudite
KW  - melt-quench-anneal
KW  - ball mill
KW  - neutron powder diffraction
KW  - thermoelectric properties
KW  - figure of merit
Y1  - 2017
U6  - https://doi.org/10.1021/acsaem.7b00015
SN  - 2574-0962
VL  - 1
IS  - 1
SP  - 113
EP  - 122
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Kretschmer, Marlene
A1  - Cohen, Judah
A1  - Matthias, Vivien
A1  - Runge, Jakob
A1  - Coumou, Dim
T1  - The different stratospheric influence on cold-extremes in Eurasia and North America
JF  - npj Climate and Atmospheric Science
N2  - The stratospheric polar vortex can influence the tropospheric circulation and thereby winter weather in the mid-latitudes. Weak vortex states, often associated with sudden stratospheric warmings (SSW), have been shown to increase the risk of cold-spells especially over Eurasia, but its role for North American winters is less clear. Using cluster analysis, we show that there are two dominant patterns of increased polar cap heights in the lower stratosphere. Both patterns represent a weak polar vortex but they are associated with different wave mechanisms and different regional tropospheric impacts. The first pattern is zonally symmetric and associated with absorbed upward-propagating wave activity, leading to a negative phase of the North Atlantic Oscillation (NAO) and cold-air outbreaks over northern Eurasia. This coupling mechanism is well-documented in the literature and is consistent with the downward migration of the northern annular mode (NAM). The second pattern is zonally asymmetric and linked to downward reflected planetary waves over Canada followed by a negative phase of the Western Pacific Oscillation (WPO) and cold-spells in Central Canada and the Great Lakes region. Causal effect network (CEN) analyses confirm the atmospheric pathways associated with this asymmetric pattern. Moreover, our findings suggest the reflective mechanism to be sensitive to the exact region of upward wave-activity fluxes and to be state-dependent on the strength of the vortex. Identifying the causal pathways that operate on weekly to monthly timescales can pave the way for improved sub-seasonal to seasonal forecasting of cold spells in the mid-latitudes.
Y1  - 2018
U6  - https://doi.org/10.1038/s41612-018-0054-4
SN  - 2397-3722
VL  - 1
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Aydiner, Ekrem
A1  - Cherstvy, Andrey G.
A1  - Metzler, Ralf
T1  - Wealth distribution, Pareto law, and stretched exponential decay of money
BT  - Computer simulations analysis of agent-based models
JF  - Physica : europhysics journal ; A, Statistical mechanics and its applications
N2  - We study by Monte Carlo simulations a kinetic exchange trading model for both fixed and distributed saving propensities of the agents and rationalize the person and wealth distributions. We show that the newly introduced wealth distribution – that may be more amenable in certain situations – features a different power-law exponent, particularly for distributed saving propensities of the agents. For open agent-based systems, we analyze the person and wealth distributions and find that the presence of trap agents alters their amplitude, leaving however the scaling exponents nearly unaffected. For an open system, we show that the total wealth – for different trap agent densities and saving propensities of the agents – decreases in time according to the classical Kohlrausch–Williams–Watts stretched exponential law. Interestingly, this decay does not depend on the trap agent density, but rather on saving propensities. The system relaxation for fixed and distributed saving schemes are found to be different.
KW  - Econophysics
KW  - Wealth and income distribution
KW  - Pareto law
KW  - Scaling exponents
Y1  - 2017
U6  - https://doi.org/10.1016/j.physa.2017.08.017
SN  - 0378-4371
SN  - 1873-2119
VL  - 490
SP  - 278
EP  - 288
PB  - Elsevier
CY  - Amsterdam
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  - Ni, Binbin
A1  - Cao, Xing
A1  - Shprits, Yuri Y.
A1  - Summers, Danny
A1  - Gu, Xudong
A1  - Fu, Song
A1  - Lou, Yuequn
T1  - Hot Plasma Effects on the Cyclotron-Resonant Pitch-Angle Scattering Rates of Radiation Belt Electrons Due to EMIC Waves
JF  - Geophysical research letters
N2  - To investigate the hot plasma effects on the cyclotron-resonant interactions between electromagnetic ion cyclotron (EMIC) waves and radiation belt electrons in a realistic magnetospheric environment, calculations of the wave-induced bounce-averaged pitch angle diffusion coefficients are performed using both the cold and hot plasma dispersion relations. The results demonstrate that the hot plasma effects have a pronounced influence on the electron pitch angle scattering rates due to all three EMIC emission bands (H+, He+, and O+) when the hot plasma dispersion relation deviates significantly from the cold plasma approximation. For a given wave spectrum, the modification of the dispersion relation by hot anisotropic protons can strongly increase the minimum resonant energy for electrons interacting with O+ band EMIC waves, while the minimum resonant energies for H+ and He+ bands are not greatly affected. For H+ band EMIC waves, inclusion of hot protons tends to weaken the pitch angle scattering efficiency of >5MeV electrons. The most crucial differences introduced by the hot plasma effects occur for >3MeV electron scattering rates by He+ band EMIC waves. Mainly due to the changes of resonant frequency and wave group velocity when the hot protons are included, the difference in scattering rates can be up to an order of magnitude, showing a strong dependence on both electron energy and equatorial pitch angle. Our study confirms the importance of including hot plasma effects in modeling the scattering of ultra-relativistic radiation belt electrons by EMIC waves.
Y1  - 2018
U6  - https://doi.org/10.1002/2017GL076028
SN  - 0094-8276
SN  - 1944-8007
VL  - 45
IS  - 1
SP  - 21
EP  - 30
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Guber, Christoph Rudolf
A1  - Richter, Philipp
A1  - Wendt, Martin
T1  - Multiple origins for the DLA at zabs = 0.313 toward PKS 1127–145 indicated by a complex dust depletion pattern of Ca, Ti, and Mn
JF  - Astronomy and astrophysics : an international weekly journal
N2  - Aims:
We aim to investigate the dust depletion properties of optically thick gas in and around galaxies and its origin we study in detail the dust depletion patterns of Ti, Mn, and Ca in the multi-component damped Lyman alpha (DLA) absorber at z(abs) = 0.313 toward the quasar PKS 1127-145. Methods:
We performed a detailed spectral analysis of the absorption profiles of Ca II, Mn II, TIII, and Na I associated with the DLA toward PKS 1127-145, based on optical high-resolution data obtained with the UVES instrument at the Very Large Telescope. We obtained column densities and Doppler-parameters for the ions listed above and determine their gas-phase abundances, from which we conclude on their dust depletion properties. We compared the Ca and Ti depletion properties of this DLA with that of other DLAs. 
Results:
One of the six analyzed absorption components (component 3) shows a striking underabundance of Ti and Mn in the gas-phase, indicating the effect of dust depletion for these elements and a locally enhanced dust-to-gas ratio. In this DLA and in other similar absorbers, the Mn II abundance follows that of Ti II very closely, implying that both ions are equally sensitive to the dust depletion effects. 
Conclusions:
Our analysis indicates that the DLA toward PKS 1127 145 has multiple origins. With its narrow line width and its strong dust depletion, component 3 points toward the presence of a neutral gas disk from a faint LSB galaxy in front of PKS 1127 145, while the other, more diffuse and dust-poor, absorption components possibly are related to tidal gas features from the interaction between the various, optically confirmed galaxy-group members. In general, the Mn/Ca II ratio in sub-DLAs and DLAs possibly serves as an important indicator to discriminate between dust-rich and dust-poor in neutral gas in and around galaxies.
KW  - quasars: absorption lines
KW  - galaxies: abundances
KW  - intergalactic medium
KW  - quasars: individual: PKS1127-145
KW  - dust, extinction
KW  - ISM: kinematics and dynamics
Y1  - 2018
U6  - https://doi.org/10.1051/0004-6361/201730984
SN  - 1432-0746
VL  - 609
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Hainich, Rainer
A1  - Oskinova, Lida
A1  - Shenar, Tomer
A1  - Marchant Campos, Pablo
A1  - Eldridge, J. J.
A1  - Sander, Andreas Alexander Christoph
A1  - Hamann, Wolf-Rainer
A1  - Langer, Norbert
A1  - Todt, Helge Tobias
T1  - Observational properties of massive black hole binary progenitors
JF  - Astronomy and astrophysics : an international weekly journal
N2  - Context:
The first directly detected gravitational waves (GW 150914) were emitted by two coalescing black holes (BHs) with masses of ≈ 36 M⊙ and ≈ 29 M⊙. Several scenarios have been proposed to put this detection into an astrophysical context. The evolution of an isolated massive binary system is among commonly considered models.
Aims:
Various groups have performed detailed binary-evolution calculations that lead to BH merger events. However, the question remains open as to whether binary systems with the predicted properties really exist. The aim of this paper is to help observers to close this gap by providing spectral characteristics of massive binary BH progenitors during a phase where at least one of the companions is still non-degenerate.
Methods:
Stellar evolution models predict fundamental stellar parameters. Using these as input for our stellar atmosphere code (Potsdam Wolf-Rayet), we compute a set of models for selected evolutionary stages of massive merging BH progenitors at different metallicities.
Results:
The synthetic spectra obtained from our atmosphere calculations reveal that progenitors of massive BH merger events start their lives as O2-3V stars that evolve to early-type blue supergiants before they undergo core-collapse during the Wolf-Rayet phase. When the primary has collapsed, the remaining system will appear as a wind-fed high-mass X-ray binary. Based on our atmosphere models, we provide feedback parameters, broad band magnitudes, and spectral templates that should help to identify such binaries in the future.
Conclusions:
While the predicted parameter space for massive BH binary progenitors is partly realized in nature, none of the known massive binaries match our synthetic spectra of massive BH binary progenitors exactly. Comparisons of empirically determined mass-loss rates with those assumed by evolution calculations reveal significant differences. The consideration of the empirical mass-loss rates in evolution calculations will possibly entail a shift of the maximum in the predicted binary-BH merger rate to higher metallicities, that is, more candidates should be expected in our cosmic neighborhood than previously assumed.
KW  - gravitational waves
KW  - binaries: close
KW  - stars: early-type
KW  - stars: atmospheres
KW  - stars: winds
KW  - outflows
KW  - stars: mass-loss
Y1  - 2018
U6  - https://doi.org/10.1051/0004-6361/201731449
SN  - 1432-0746
VL  - 609
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Zellmeier, M.
A1  - Brenner, Thomas J. K.
A1  - Janietz, Silvia
A1  - Nickel, N. H.
A1  - Rappich, J.
T1  - Polythiophenes as emitter layers for crystalline silicon solar cells
BT  - parasitic absorption, interface passivation, and open circuit voltage
JF  - Journal of applied physics
N2  - We investigated the influence of the emitter (amorphous-Si, a-Si, or polythiophene derivatives: poly(3-hexylthiophene), P3HT, and poly(3-[3,6-dioxaheptyl]-thiophene), P3DOT) and the interface passivation (intrinsic a-Si or SiOX and methyl groups or SiOX) on the c-Si based 1 × 1 cm2 planar hybrid heterojunction solar cell parameters. We observed higher short circuit currents for the P3HT or P3DOT/c-Si solar cells than those obtained for a-Si/c-Si devices, independent of the interface passivation. The obtained VOC of 659 mV for the P3DOT/SiOX/c-Si heterojunction solar cell with hydrophilic 3,6-dioxaheptyl side chains is among the highest reported for c-Si/polythiophene devices. The maximum power conversion efficiency, PCE, was 11% for the P3DOT/SiOX/c-Si heterojunction solar cell. Additionally, our wafer lifetime measurements reveal a field effect passivation in the wafer induced by the polythiophenes when deposited on c-Si.
Y1  - 2018
U6  - https://doi.org/10.1063/1.5006625
SN  - 0021-8979
SN  - 1089-7550
VL  - 123
IS  - 3
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - JOUR
A1  - Pikovskij, Arkadij
T1  - Reconstruction of a random phase dynamics network from observations
JF  - Physics letters : A
N2  - We consider networks of coupled phase oscillators of different complexity: Kuramoto–Daido-type networks, generalized Winfree networks, and hypernetworks with triple interactions. For these setups an inverse problem of reconstruction of the network connections and of the coupling function from the observations of the phase dynamics is addressed. We show how a reconstruction based on the minimization of the squared error can be implemented in all these cases. Examples include random networks with full disorder both in the connections and in the coupling functions, as well as networks where the coupling functions are taken from experimental data of electrochemical oscillators. The method can be directly applied to asynchronous dynamics of units, while in the case of synchrony, additional phase resettings are necessary for reconstruction.
KW  - Phase dynamics
KW  - Network reconstruction
Y1  - 2017
U6  - https://doi.org/10.1016/j.physleta.2017.11.012
SN  - 0375-9601
SN  - 1873-2429
VL  - 382
IS  - 4
SP  - 147
EP  - 152
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Ramiaramanantsoa, Tahina
A1  - Moffat, Anthony F. J.
A1  - Harmon, Robert
A1  - Ignace, R.
A1  - St-Louis, Nicole
A1  - Vanbeveren, Dany
A1  - Shenar, Tomer
A1  - Pablo, Herbert
A1  - Richardson, Noel D.
A1  - Howarth, Ian D.
A1  - Stevens, Ian R.
A1  - Piaulet, Caroline
A1  - St-Jean, Lucas
A1  - Eversberg, Thomas
A1  - Pigulski, Andrzej
A1  - Popowicz, Adam
A1  - Kuschnig, Rainer
A1  - Zoclonska, Elzbieta
A1  - Buysschaert, Bram
A1  - Handler, Gerald
A1  - Weiss, Werner W.
A1  - Wade, Gregg A.
A1  - Rucinski, Slavek M.
A1  - Zwintz, Konstanze
A1  - Luckas, Paul
A1  - Heathcote, Bernard
A1  - Cacella, Paulo
A1  - Powles, Jonathan
A1  - Locke, Malcolm
A1  - Bohlsen, Terry
A1  - Chené, André-Nicolas
A1  - Miszalski, Brent
A1  - Waldron, Wayne L.
A1  - Kotze, Marissa M.
A1  - Kotze, Enrico J.
A1  - Böhm, Torsten
T1  - BRITE-Constellation high-precision time-dependent photometry of the early O-type supergiant zeta Puppis unveils the photospheric drivers of its small- and large-scale wind structures
JF  - Monthly notices of the Royal Astronomical Society
N2  - From 5.5 months of dual-band optical photometric monitoring at the 1 mmag level, BRITE-Constellation has revealed two simultaneous types of variability in the O4I(n)fp star ζ Puppis: one single periodic non-sinusoidal component superimposed on a stochastic component. The monoperiodic component is the 1.78-d signal previously detected by Coriolis/Solar Mass Ejection Imager, but this time along with a prominent first harmonic. The shape of this signal changes over time, a behaviour that is incompatible with stellar oscillations but consistent with rotational modulation arising from evolving bright surface inhomogeneities. By means of a constrained non-linear light-curve inversion algorithm, we mapped the locations of the bright surface spots and traced their evolution. Our simultaneous ground-based multisite spectroscopic monitoring of the star unveiled cyclical modulation of its He ii λ4686 wind emission line with the 1.78-d rotation period, showing signatures of corotating interaction regions that turn out to be driven by the bright photospheric spots observed by BRITE. Traces of wind clumps are also observed in the He ii λ4686 line and are correlated with the amplitudes of the stochastic component of the light variations probed by BRITE at the photosphere, suggesting that the BRITE observations additionally unveiled the photospheric drivers of wind clumps in ζ Pup and that the clumping phenomenon starts at the very base of the wind. The origins of both the bright surface inhomogeneities and the stochastic light variations remain unknown, but a subsurface convective zone might play an important role in the generation of these two types of photospheric variability.
KW  - techniques: photometric
KW  - techniques: spectroscopic
KW  - stars: massive
KW  - stars: rotation
KW  - starspots
KW  - supergiants
KW  - stars: winds, outflows
Y1  - 2017
U6  - https://doi.org/10.1093/mnras/stx2671
SN  - 0035-8711
SN  - 1365-2966
VL  - 473
IS  - 4
SP  - 5532
EP  - 5569
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Ohm, Stefan
A1  - Hoischen, Clemens
T1  - On the expected gamma-ray emission from nearby flaring stars
JF  - Monthly notices of the Royal Astronomical Society
N2  - Stellar flares have been extensively studied in soft X-rays (SXRs) by basically every X-ray mission. Hard X-ray (HXR) emission from stellar superflares, however, have only been detected from a handful of objects over the past years. One very extreme event was the superflare from the young M-dwarf DGCVn binary star system, which triggered Swift/BAT as if it was a gamma-ray burst. In this work, we estimate the expected gamma-ray emission from DGCVn and the most extreme stellar flares by extrapolating from solar flares based on measured solar energetic particles (SEPs), as well as thermal and non-thermal emission properties. We find that ions are plausibly accelerated in stellar superflares to 100 GeV energies, and possibly up to TeV energies in the associated coronal mass ejections. The corresponding pi(0)-decay gamma-ray emission could be detectable from stellar superflares with ground-based gamma-ray telescopes. On the other hand, the detection of gamma-ray emission implies particle densities high enough that ions suffer significant losses due to inelastic proton-proton scattering. The next-generation Cherenkov Telescope Array (CTA) should be able to probe superflares from M dwarfs in the solar neighbourhood and constrain the energy in interacting cosmic rays and/or their maximum energy. The detection of gamma-ray emission from stellar flares would open a new window for the study of stellar physics, the underlying physical processes in flares and their impact on habitability of planetary systems.
KW  - radiation mechanisms: non-thermal
KW  - stars: flare
KW  - stars: individual: DGCVn-gamma rays: stars
Y1  - 2018
U6  - https://doi.org/10.1093/mnras/stx2806
SN  - 0035-8711
SN  - 1365-2966
VL  - 474
IS  - 1
SP  - 1335
EP  - 1341
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Gorenflot, Julien
A1  - Paulke, Andreas
A1  - Piersimoni, Fortunato
A1  - Wolf, Jannic
A1  - Kan, Zhipeng
A1  - Cruciani, Federico
A1  - El Labban, Abdulrahman
A1  - Neher, Dieter
A1  - Beaujuge, Pierre M.
A1  - Laquai, Frederic
T1  - From recombination dynamics to device performance
BT  - quantifying the efficiency of exciton dissociation, charge separation, and extraction in bulk heterojunction solar cells with Fluorine-Substituted polymer donors
JF  - dvanced energy materials
N2  - An original set of experimental and modeling tools is used to quantify the yield of each of the physical processes leading to photocurrent generation in organic bulk heterojunction solar cells, enabling evaluation of materials and processing condition beyond the trivial comparison of device performances. Transient absorption spectroscopy, “the” technique to monitor all intermediate states over the entire relevant timescale, is combined with time-delayed collection field experiments, transfer matrix simulations, spectral deconvolution, and parametrization of the charge carrier recombination by a two-pool model, allowing quantification of densities of excitons and charges and extrapolation of their kinetics to device-relevant conditions. Photon absorption, charge transfer, charge separation, and charge extraction are all quantified for two recently developed wide-bandgap donor polymers: poly(4,8-bis((2-ethylhexyl)oxy)benzo[1,2-b:4,5-b′]dithiophene-3,4-difluorothiophene) (PBDT[2F]T) and its nonfluorinated counterpart poly(4,8-bis((2-ethylhexyl)oxy)benzo[1,2-b:4,5-b′]dithiophene-3,4-thiophene) (PBDT[2H]T) combined with PC71BM in bulk heterojunctions. The product of these yields is shown to agree well with the devices' external quantum efficiency. This methodology elucidates in the specific case studied here the origin of improved photocurrents obtained when using PBDT[2F]T instead of PBDT[2H]T as well as upon using solvent additives. Furthermore, a higher charge transfer (CT)-state energy is shown to lead to significantly lower energy losses (resulting in higher VOC) during charge generation compared to P3HT:PCBM.
KW  - bulk heterojunction
KW  - charge generation yield
KW  - charge recombination yield
KW  - polymer solar cells
KW  - transient absorption spectroscopy
Y1  - 2018
U6  - https://doi.org/10.1002/aenm.201701678
SN  - 1614-6832
SN  - 1614-6840
VL  - 8
IS  - 4
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Sandev, Trifce
A1  - Metzler, Ralf
A1  - Chechkin, Aleksei V.
T1  - From continuous time random walks to the generalized diffusion equation
JF  - Fractional calculus and applied analysis : an international journal for theory and applications
N2  - We obtain a generalized diffusion equation in modified or Riemann-Liouville form from continuous time random walk theory. The waiting time probability density function and mean squared displacement for different forms of the equation are explicitly calculated. We show examples of generalized diffusion equations in normal or Caputo form that encode the same probability distribution functions as those obtained from the generalized diffusion equation in modified form. The obtained equations are general and many known fractional diffusion equations are included as special cases.
KW  - continuous time random walk (CTRW)
KW  - generalized diffusion equation
KW  - Mittag-Leffler functions
KW  - anomalous diffusion
Y1  - 2018
U6  - https://doi.org/10.1515/fca-2018-0002
SN  - 1311-0454
SN  - 1314-2224
VL  - 21
IS  - 1
SP  - 10
EP  - 28
PB  - De Gruyter
CY  - Berlin
ER  - 
TY  - JOUR
A1  - Sawicki, Jakub
A1  - Abel, Markus
A1  - Schöll, Eckehard
T1  - Synchronization of organ pipes
JF  - The European physical journal : B, Condensed matter and complex systems
N2  - We investigate synchronization of coupled organ pipes. Synchronization and reflection in the organ lead to undesired weakening of the sound in special cases. Recent experiments have shown that sound interaction is highly complex and nonlinear, however, we show that two delay-coupled Van-der-Pol oscillators appear to be a good model for the occurring dynamical phenomena. Here the coupling is realized as distance-dependent, or time-delayed, equivalently. Analytically, we investigate the synchronization frequency and bifurcation scenarios which occur at the boundaries of the Arnold tongues. We successfully compare our results to experimental data.
Y1  - 2018
U6  - https://doi.org/10.1140/epjb/e2017-80485-8
SN  - 1434-6028
SN  - 1434-6036
VL  - 91
IS  - 2
PB  - Springer
CY  - New York
ER  -