TY - JOUR A1 - Brügger, Sandra Olivia A1 - Gobet, Erika A1 - Sigl, Michael A1 - Osmont, Dimitri A1 - Papina, Tatyana A1 - Rudaya, Natalia A1 - Schwikowski-Gigar, Margit A1 - Tinner, Willy T1 - Ice records provide new insights into climatic vulnerability of Central Asian forest and steppe communities JF - Global and planetary change N2 - Forest and steppe communities in the Altai region of Central Asia are threatened by changing climate and anthropogenic pressure. Specifically, increasing drought and grazing pressure may cause collapses of moisture-demanding plant communities, particularly forests. Knowledge about past vegetation and fire responses to climate and land use changes may help anticipating future ecosystem risks, given that it has the potential to disclose mechanisms and processes that govern ecosystem vulnerability. We present a unique paleoecological record from the high-alpine Tsambagarav glacier in the Mongolian Altai that provides novel large-scale information on vegetation, fire and pollution with an exceptional temporal resolution and precision. Our palynological record identifies several late-Holocene boreal forest expansions, contractions and subsequent recoveries. Maximum forest expansions occurred at 3000-2800 BC, 2400-2100 BC, and 1900-1800 BC. After 1800 BC mixed boreal forest communities irrecoverably declined. Fires reached a maximum at 1600 BC, 200 years after the final forest collapse. Our multiproxy data suggest that burning peaked in response to dead biomass accumulation resulting from forest diebacks. Vegetation and fire regimes partly decoupled from climate after 1700 AD, when atmospheric industrial pollution began, and land use intensified. We conclude that moisture availability was more important than temperature for past vegetation dynamics, in particular for forest loss and steppe expansion. The past Mongolian Altai evidence implies that in the future forests of the Russian Altai may collapse in response to reduced moisture availability. KW - Boreal forest diebacks KW - Climatic tipping points KW - Diversity KW - Ice core KW - Moisture change KW - Pollen KW - Microscopic charcoal KW - SCP Y1 - 2018 U6 - https://doi.org/10.1016/j.gloplacha.2018.07.010 SN - 0921-8181 SN - 1872-6364 VL - 169 SP - 188 EP - 201 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Ramiaramanantsoa, Tahina A1 - Ratnasingam, Rathish A1 - Shenar, Tomer A1 - Moffat, Anthony F. J. A1 - Rogers, Tamara M. A1 - Popowicz, Adam A1 - Kuschnig, Rainer A1 - Pigulski, Andrzej A1 - Handler, Gerald A1 - Wade, Gregg A. A1 - Zwintz, Konstanze A1 - Weiss, Werner W. T1 - A BRITE view on the massive O-type supergiant V973 Scorpii BT - hints towards internal gravity waves or sub-surface convection zones JF - Monthly notices of the Royal Astronomical Society N2 - Stochastically triggered photospheric light variations reaching similar to 40 mmag peak-to-valley amplitudes have been detected in the O8 Iaf supergiant V973 Scorpii as the outcome of 2 months of high-precision time-resolved photometric observations with the BRIght Target Explorer (BRITE) nanosatellites. The amplitude spectrum of the time series photometry exhibits a pronounced broad bump in the low-frequency regime (less than or similar to 0.9 d(-1)) where several prominent frequencies are detected. A time-frequency analysis of the observations reveals typical mode lifetimes of the order of 5-10 d. The overall features of the observed brightness amplitude spectrum of V973 Sco match well with those extrapolated from two-dimensional hydrodynamical simulations of convectively driven internal gravity waves randomly excited from deep in the convective cores of massive stars. An alternative or additional possible source of excitation from a sub-surface convection zone needs to be explored in future theoretical investigations. KW - convection KW - waves KW - techniques: photometric KW - stars: massive KW - supergiants Y1 - 2018 U6 - https://doi.org/10.1093/mnras/sty1897 SN - 0035-8711 SN - 1365-2966 VL - 480 IS - 1 SP - 972 EP - 986 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Thapa, Samudrajit A1 - Wyłomańska, Agnieszka A1 - Sikora, Grzegorz A1 - Wagner, Caroline E. A1 - Krapf, Diego A1 - Kantz, Holger A1 - Chechkin, Aleksei V. A1 - Metzler, Ralf T1 - Leveraging large-deviation statistics to decipher the stochastic properties of measured trajectories JF - New Journal of Physics N2 - Extensive time-series encoding the position of particles such as viruses, vesicles, or individualproteins are routinely garnered insingle-particle tracking experiments or supercomputing studies.They contain vital clues on how viruses spread or drugs may be delivered in biological cells.Similar time-series are being recorded of stock values in financial markets and of climate data.Such time-series are most typically evaluated in terms of time-averaged mean-squareddisplacements (TAMSDs), which remain random variables for finite measurement times. Theirstatistical properties are different for differentphysical stochastic processes, thus allowing us toextract valuable information on the stochastic process itself. To exploit the full potential of thestatistical information encoded in measured time-series we here propose an easy-to-implementand computationally inexpensive new methodology, based on deviations of the TAMSD from itsensemble average counterpart. Specifically, we use the upper bound of these deviations forBrownian motion (BM) to check the applicability of this approach to simulated and real data sets.By comparing the probability of deviations fordifferent data sets, we demonstrate how thetheoretical bound for BM reveals additional information about observed stochastic processes. Weapply the large-deviation method to data sets of tracer beads tracked in aqueous solution, tracerbeads measured in mucin hydrogels, and of geographic surface temperature anomalies. Ouranalysis shows how the large-deviation properties can be efficiently used as a simple yet effectiveroutine test to reject the BM hypothesis and unveil relevant information on statistical propertiessuch as ergodicity breaking and short-time correlations. KW - diffusion KW - anomalous diffusion KW - large-deviation statistic KW - time-averaged mean squared displacement KW - Chebyshev inequality Y1 - 2020 U6 - https://doi.org/10.1088/1367-2630/abd50e SN - 1367-2630 VL - 23 PB - Dt. Physikalische Ges. ; IOP CY - Bad Honnef ; London ER - TY - JOUR A1 - Wolf, Thomas A1 - Gühr, Markus T1 - Photochemical pathways in nucleobases measured with an X-ray FEL JF - Philosophical Transactions of the Royal Society of London, Series A : Mathematical, Physical and Engineering Sciences N2 - The conversion of light energy into other molecular energetic degrees of freedom is often dominated by ultrafast, non-adiabatic processes. Femtosecond spectroscopy with optical pulses has helped in shaping our understanding of crucial processes in molecular energy-conversion. The advent of new, ultrashort and bright X-ray free electron laser sources opens the possibility to use X-ray-typical element and site sensitivity for ultrafast molecular research. We present two types of spectroscopy, ultrafast Auger and ultrafast X-ray absorption spectroscopy, and discuss their sensitivity to molecular processes. While Auger spectroscopy is able to monitor bond distance changes in the vicinity of an X-ray created core hole, near-edge absorption spectroscopy can deliver high-fidelity information on non-adiabatic transitions involving lone-pair orbitals. We demonstrate these features on the example of the UV-excited nucleobase thymine, investigated at the oxygen K-edge. We find a C-O bond elongation in the Auger data in addition to pi pi*/n pi* non-adiabatic transition in X-ray near-edge absorption. We compare the results from both methods and draw a conclusive scenario of non-adiabatic molecular relaxation after UV excitation. KW - nucleobase KW - time-resolved X-ray probing KW - Auger decay KW - femtosecond laser spectroscopy Y1 - 2019 U6 - https://doi.org/10.1098/rsta.2017.0473 SN - 1364-503X SN - 1471-2962 VL - 377 IS - 2145 PB - Royal Society CY - London 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 - Robrade, Jan A1 - Oskinova, Lida A1 - Schmitt, J. H. M. M. A1 - Leto, Paolo A1 - Trigilio, C. T1 - Outstanding X-ray emission from the stellar radio pulsar CU Virginis JF - Astronomy and astrophysics : an international weekly journal N2 - Context. Among the intermediate-mass magnetic chemically peculiar (MCP) stars, CU Vir is one of the most intriguing objects. Its 100% circularly polarized beams of radio emission sweep the Earth as the star rotates, thereby making this strongly magnetic star the prototype of a class of nondegenerate stellar radio pulsars. While CU Vir is well studied in radio, its high-energy properties are not known. Yet, X-ray emission is expected from stellar magnetospheres and confined stellar winds. Aims. Using X-ray data we aim to test CU Vir for intrinsic X-ray emission and investigate mechanisms responsible for its generation. Methods. We present X-ray observations performed with XMM-Newton and Chandra and study obtained X-ray images, light curves, and spectra. Basic X-ray properties are derived from spectral modelling and are compared with model predictions. In this context we investigate potential thermal and nonthermal X-ray emission scenarios. Results. We detect an X-ray source at the position of CU Vir. With LX approximate to 3 x 10(28) erg s(-1) it is moderately X-ray bright, but the spectrum is extremely hard compared to other Ap stars. Spectral modelling requires multi-component models with predominant hot plasma at temperatures of about T-X = 25MK or, alternatively, a nonthermal spectral component. Both types of model provide a virtually equivalent description of the X-ray spectra. The Chandra observation was performed six years later than those by XMM-Newton, yet the source has similar X-ray flux and spectrum, suggesting a steady and persistent X-ray emission. This is further confirmed by the X-ray light curves that show only mild X-ray variability. Conclusions. CU Vir is also an exceptional star at X-ray energies. To explain its full X-ray properties, a generating mechanism beyond standard explanations, like the presence of a low-mass companion or magnetically confined wind-shocks, is required. Magnetospheric activity might be present or, as proposed for fast-rotating strongly magnetic Bp stars, the X-ray emission of CU Vir is predominantly auroral in nature. KW - individual: CU Vir KW - stars: activity KW - stars: chemically peculiar KW - stars: magnetic field KW - X-rays: stars Y1 - 2018 U6 - https://doi.org/10.1051/0004-6361/201833492 SN - 1432-0746 VL - 619 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Shen, Z. A1 - Diercke, Andrea A1 - Denker, Carsten T1 - Calibration of full-disk He i 10 830 angstrom filtergrams of the Chromospheric Telescope JF - Astronomische Nachrichten = Astronomical notes N2 - The Chromospheric Telescope (ChroTel) is a small 10-cm robotic telescope at Observatorio del Teide on Tenerife (Spain), which observes the entire sun in Hα, Ca ii K, and He i 10 830 Å. We present a new calibration method that includes limb-darkening correction, removal of nonuniform filter transmission, and determination of He i Doppler velocities. Chromospheric full-disk filtergrams are often obtained with Lyot filters, which may display nonuniform transmission causing large-scale intensity variations across the solar disk. Removal of a 2D symmetric limb-darkening function from full-disk images results in a flat background. However, transmission artifacts remain and are even more distinct in these contrast-enhanced images. Zernike polynomials are uniquely appropriate to fit these large-scale intensity variations of the background. The Zernike coefficients show a distinct temporal evolution for ChroTel data, which is likely related to the telescope's alt-azimuth mount that introduces image rotation. In addition, applying this calibration to sets of seven filtergrams that cover the He i triplet facilitates the determination of chromospheric Doppler velocities. To validate the method, we use three datasets with varying levels of solar activity. The Doppler velocities are benchmarked with respect to cotemporal high-resolution spectroscopic data of the GREGOR Infrared Spectrograph (GRIS). Furthermore, this technique can be applied to ChroTel Hα and Ca ii K data. The calibration method for ChroTel filtergrams can be easily adapted to other full-disk data exhibiting unwanted large-scale variations. The spectral region of the He i triplet is a primary choice for high-resolution near-infrared spectropolarimetry. Here, the improved calibration of ChroTel data will provide valuable context data. KW - methods: Data analysis KW - methods: Observational KW - Sun: Chromosphere KW - techniques: Image processing Y1 - 2019 U6 - https://doi.org/10.1002/asna.201813536 SN - 0004-6337 SN - 1521-3994 VL - 339 IS - 9-10 SP - 661 EP - 671 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Rychkov, Dmitry A1 - Altafim, Ruy Alberto Pisani T1 - Template-based fluoroethylenepropylene ferroelectrets with enhanced thermal stability of piezoelectricity JF - Journal of applied physics N2 - In ferroelectrets, the piezoelectricity stems from the charges of both polarities trapped on the inner surfaces of the cavities in the material, so that its thermal stability is defined by the stability of the respective charges. In the present work, a template-based lamination technique has been employed to fabricate tubular-channel ferroelectrets from fluoroethylenepropylene (FEP) films. It has been shown that the piezoelectricity in FEP ferroelectrets decays at relatively low temperatures due to the inherently lower thermal stability of the positive charge. In order to improve charge trapping, we have treated both FEP films and inner surfaces of the ferroelectret cavities with titanium-tetrachloride vapor, using the atomic-layer-deposition technique. Using surface-potential-decay measurements on FEP films, we have found that the charge-decay curves shift by more than 100 degrees C to the higher temperatures as a result of the surface treatment. Direct measurements of piezoelectric d(33) coefficients as a function of temperature have shown that the piezoelectric stability is likewise improved with the d(33)-decay curves shifted by 60 degrees C to the right. The improvement of electret/ferroelectret properties can be attributed to the formation of the deeper traps on the chemically modified FEP surface. SEM micrographs and EDS analysis reveal island-like structures with titanium- and oxygen-containing species that can be responsible for the deeper trapping of the electret charges. Published by AIP Publishing. Y1 - 2018 U6 - https://doi.org/10.1063/1.5041374 SN - 0021-8979 SN - 1089-7550 VL - 124 IS - 17 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Sposini, Vittoria A1 - Chechkin, Aleksei V. A1 - Metzler, Ralf T1 - First passage statistics for diffusing diffusivity JF - Journal of physics : A, Mathematical and theoretical N2 - A rapidly increasing number of systems is identified in which the stochastic motion of tracer particles follows the Brownian law < r(2)(t)> similar or equal to Dt yet the distribution of particle displacements is strongly non-Gaussian. A central approach to describe this effect is the diffusing diffusivity (DD) model in which the diffusion coefficient itself is a stochastic quantity, mimicking heterogeneities of the environment encountered by the tracer particle on its path. We here quantify in terms of analytical and numerical approaches the first passage behaviour of the DD model. We observe significant modifications compared to Brownian-Gaussian diffusion, in particular that the DD model may have a faster first passage dynamics. Moreover we find a universal crossover point of the survival probability independent of the initial condition. KW - diffusion KW - superstatistics KW - first passage Y1 - 2018 U6 - https://doi.org/10.1088/1751-8121/aaf6ff SN - 1751-8113 SN - 1751-8121 VL - 52 IS - 4 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Jonscher, Ernst A1 - Flemming, Sven A1 - Schmitt, Marius A1 - Sabitzki, Ricarda A1 - Reichard, Nick A1 - Birnbaum, Jakob A1 - Bergmann, Bärbel A1 - Höhn, Katharina A1 - Spielmann, Tobias T1 - PfVPS45 Is Required for Host Cell Cytosol Uptake by Malaria Blood Stage Parasites JF - Cell host & microbe N2 - During development in human erythrocytes, the malaria parasite Plasmodium falciparum internalizes a large part of the cellular content of the host cell. The internalized cytosol, consisting largely of hemoglobin, is transported to the parasite’s food vacuole where it is degraded, providing nutrients and space for growth. This host cell cytosol uptake (HCCU) is crucial for parasite survival but the parasite proteins mediating this process remain obscure. Here, we identify P. falciparum VPS45 as an essential factor in HCCU. Conditional inactivation of PfVPS45 led to an accumulation of host cell cytosol-filled vesicles within the parasite and inhibited the delivery of hemoglobin to the parasite's digestive vacuole, resulting in arrested parasite growth. A proportion of these HCCU vesicle intermediates was positive for phosphatidylinositol 3-phosphate, suggesting endosomal characteristics. Thus PfVPS45 provides insight into the elusive machinery of the ingestion pathway in a parasite that contains an endolysosomal system heavily repurposed for protein secretion. Y1 - 2018 U6 - https://doi.org/10.1016/j.chom.2018.11.010 SN - 1931-3128 SN - 1934-6069 VL - 25 IS - 1 SP - 166 EP - 173 PB - Cell Press CY - Cambridge ER - TY - JOUR A1 - Dybiec, Bartlomiej A1 - Capala, Karol A1 - Chechkin, Aleksei V. A1 - Metzler, Ralf T1 - Conservative random walks in confining potentials JF - Journal of physics : A, Mathematical and theoretical N2 - Levy walks are continuous time random walks with spatio-temporal coupling of jump lengths and waiting times, often used to model superdiffusive spreading processes such as animals searching for food, tracer motion in weakly chaotic systems, or even the dynamics in quantum systems such as cold atoms. In the simplest version Levy walks move with a finite speed. Here, we present an extension of the Levy walk scenario for the case when external force fields influence the motion. The resulting motion is a combination of the response to the deterministic force acting on the particle, changing its velocity according to the principle of total energy conservation, and random velocity reversals governed by the distribution of waiting times. For the fact that the motion stays conservative, that is, on a constant energy surface, our scenario is fundamentally different from thermal motion in the same external potentials. In particular, we present results for the velocity and position distributions for single well potentials of different steepness. The observed dynamics with its continuous velocity changes enriches the theory of Levy walk processes and will be of use in a variety of systems, for which the particles are externally confined. KW - Levy walk KW - conservative random walks KW - Levy flight Y1 - 2018 U6 - https://doi.org/10.1088/1751-8121/aaefc2 SN - 1751-8113 SN - 1751-8121 VL - 52 IS - 1 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Xue, Rui A1 - Liu, Ruo-Yu A1 - Wang, Xiang-Yu A1 - Yan, Huirong A1 - Böttcher, Markus T1 - On the minimum jet power of TeV BL Lac objects in the p-gamma model JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - We study the requirement of the jet power in the conventional p-gamma models (photopion production and Bethe-Heitler pair production) for TeV BL Lac objects. We select a sample of TeV BL Lac objects whose spectral energy distributions are difficult to explain by the one-zone leptonic model. Based on the relation between the p-gamma interaction efficiency and the opacity of gamma gamma absorption, we find that the detection of TeV emission poses upper limits on the p-gamma interaction efficiencies in these sources and hence minimum jet powers can be derived accordingly. We find that the obtained minimum jet powers exceed the Eddington luminosity of the supermassive black holes (SMBHs). Implications for the accretion mode of the SMBHs in these BL Lac objects and the origin of their TeV emissions are discussed. KW - galaxies: active KW - galaxies: jets KW - radiation mechanisms: non-thermal Y1 - 2019 U6 - https://doi.org/10.3847/1538-4357/aaf720 SN - 0004-637X SN - 1538-4357 VL - 871 IS - 1 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Liu, Ruo-Yu A1 - Yan, Huirong A1 - Wang, Xiang-Yu A1 - Shao, Shi A1 - Li, Hui T1 - Gamma-Ray production in the extended halo of the galaxy and possible implications for the origin of galactic cosmic rays JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - Various studies have implied the existence of a gaseous halo around the Galaxy extending out to similar to 100 kpc. Galactic cosmic rays (CRs) that propagate to the halo, either by diffusion or by convection with the possibly existing large-scale Galactic wind, can interact with the gas therein and produce gamma-rays via proton-proton collision. We calculate the CR distribution in the halo and the gamma-ray flux, and explore the dependence of the result on model parameters such as diffusion coefficient, CR luminosity, and CR spectral index. We find that the current measurement of isotropic gamma-ray background (IGRB) at less than or similar to TeV with the Fermi Large Area Telescope already approaches a level that can provide interesting constraints on the properties of Galactic CR (e.g., with CR luminosity L-CR <= 1041 erg s(-1)). We also discuss the possibilities of the Fermi bubble and IceCube neutrinos originating from the proton-proton collision between CRs and gas in the halo, as well as the implication of our results for the baryon budget of the hot circumgalactic medium of our Galaxy. Given that the isotropic gamma-ray background is likely to be dominated by unresolved extragalactic sources, future telescopes may extract more individual sources from the IGRB, and hence put even more stringent restrictions on the relevant quantities (such as Galactic CR luminosity and baryon budget in the halo) in the presence of a turbulent halo that we consider. KW - cosmic rays KW - Galaxy: halo KW - gamma rays: diffuse background KW - neutrinos Y1 - 2019 U6 - https://doi.org/10.3847/1538-4357/aaf567 SN - 0004-637X SN - 1538-4357 VL - 871 IS - 1 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Goychuk, Igor T1 - Viscoelastic subdiffusion in a random Gaussian environment JF - Physical chemistry, chemical physics : a journal of European Chemical Societies N2 - Viscoelastic subdiffusion governed by a fractional Langevin equation is studied numerically in a random Gaussian environment modeled by stationary Gaussian potentials with decaying spatial correlations. This anomalous diffusion is archetypal for living cells, where cytoplasm is known to be viscoelastic and a spatial disorder also naturally emerges. We obtain some first important insights into it within a model one-dimensional study. Two basic types of potential correlations are studied: short-range exponentially decaying and algebraically slow decaying with an infinite correlation length, both for a moderate (several kBT, in the units of thermal energy), and strong (5–10kBT) disorder. For a moderate disorder, it is shown that on the ensemble level viscoelastic subdiffusion can easily overcome the medium's disorder. Asymptotically, it is not distinguishable from the disorder-free subdiffusion. However, a strong scatter in single-trajectory averages is nevertheless seen even for a moderate disorder. It features a weak ergodicity breaking, which occurs on a very long yet transient time scale. Furthermore, for a strong disorder, a very long transient regime of logarithmic, Sinai-type diffusion emerges. It can last longer and be faster in the absolute terms for weakly decaying correlations as compared with the short-range correlations. Residence time distributions in a finite spatial domain are of a generalized log-normal type and are reminiscent also of a stretched exponential distribution. They can be easily confused for power-law distributions in view of the observed weak ergodicity breaking. This suggests a revision of some experimental data and their interpretation. Y1 - 2018 U6 - https://doi.org/10.1039/c8cp05238g SN - 1463-9076 SN - 1463-9084 VL - 20 IS - 37 SP - 24140 EP - 24155 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Baran, Andrzej S. A1 - Ostensen, R. H. A1 - Telting, J. H. A1 - Vos, Joris A1 - Kilkenny, D. A1 - Vuckovic, Maja A1 - Reed, M. D. A1 - Silvotti, R. A1 - Jeffery, C. Simon A1 - Parsons, Steven G. A1 - Dhillon, V. S. A1 - Marsh, T. R. T1 - Pulsations and eclipse-time analysis of HW Vir JF - Monthly notices of the Royal Astronomical Society N2 - We analysed recent K2 data of the short-period eclipsing binary system HW Vir, which consists of a hot subdwarf-B type primary with an M-dwarf companion. We determined the mid-times of eclipses, calculated O-C diagrams, and an average shift of the secondary minimum. Our results show that the orbital period is stable within the errors over the course of the 70 days of observations. Interestingly, the offset from mid-orbital phase between the primary and the secondary eclipses is found to be 1.62 s. If the shift is explained solely by light-travel time, the mass of the sdB primary must be 0.26 M-circle dot, which is too low for the star to be core-helium burning. However, we argue that this result is unlikely to be correct and that a number of effects caused by the relative sizes of the stars conspire to reduce the effective light-travel time measurement. After removing the flux variation caused by the orbit, we calculated the amplitude spectrum to search for pulsations. The spectrum clearly shows periodic signal from close to the orbital frequency up to 4600 mu Hz, with the majority of peaks found below 2600 mu Hz. The amplitudes are below 0.1 part-per-thousand, too low to be detected with ground-based photometry. Thus, the high-precision data from the Kepler spacecraft has revealed that the primary of the HW Vir system is a pulsating sdBV star. We argue that the pulsation spectrum of the primary in HW Vir differs from that in other sdB stars due to its relatively fast rotation that is (nearly) phase-locked with the orbit. KW - binaries: eclipsing KW - stars: oscillations KW - subdwarfs Y1 - 2019 U6 - https://doi.org/10.1093/mnras/sty2473 SN - 0035-8711 SN - 1365-2966 VL - 481 IS - 2 SP - 2721 EP - 2735 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Gajda, J. A1 - Wylomanska, Agnieszka A1 - Kantz, Holger A1 - Chechkin, Aleksei V. A1 - Sikora, Grzegorz T1 - Large deviations of time-averaged statistics for Gaussian processes JF - Statistics & Probability Letters N2 - In this paper we study the large deviations of time averaged mean square displacement (TAMSD) for Gaussian processes. The theory of large deviations is related to the exponential decay of probabilities of large fluctuations in random systems. From the mathematical point of view a given statistics satisfies the large deviation principle, if the probability that it belongs to a certain range decreases exponentially. The TAMSD is one of the main statistics used in the problem of anomalous diffusion detection. Applying the theory of generalized chi-squared distribution and sub-gamma random variables we prove the upper bound for large deviations of TAMSD for Gaussian processes. As a special case we consider fractional Brownian motion, one of the most popular models of anomalous diffusion. Moreover, we derive the upper bound for large deviations of the estimator for the anomalous diffusion exponent. (C) 2018 Elsevier B.V. All rights reserved. KW - Large deviation statistics KW - Fractional Brownian motion KW - Anomalous diffusion exponent KW - Sub-gamma random variable Y1 - 2018 U6 - https://doi.org/10.1016/j.spl.2018.07.013 SN - 0167-7152 SN - 1879-2103 VL - 143 SP - 47 EP - 55 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Mardoukhi, Yousof A1 - Chechkin, Aleksei V. A1 - Metzler, Ralf T1 - Spurious ergodicity breaking in normal and fractional Ornstein–Uhlenbeck process JF - New Journal of Physics N2 - The Ornstein–Uhlenbeck process is a stationary and ergodic Gaussian process, that is fully determined by its covariance function and mean. We show here that the generic definitions of the ensemble- and time-averaged mean squared displacements fail to capture these properties consistently, leading to a spurious ergodicity breaking. We propose to remedy this failure by redefining the mean squared displacements such that they reflect unambiguously the statistical properties of any stochastic process. In particular we study the effect of the initial condition in the Ornstein–Uhlenbeck process and its fractional extension. For the fractional Ornstein–Uhlenbeck process representing typical experimental situations in crowded environments such as living biological cells, we show that the stationarity of the process delicately depends on the initial condition. KW - Ornstein–Uhlenbeck process KW - stationary stochastic process KW - ensemble and time averaged mean squared displacement Y1 - 2020 U6 - https://doi.org/10.1088/1367-2630/ab950b SN - 1367-2630 VL - 22 PB - IOP CY - London ER - TY - JOUR A1 - Makuch, Martin A1 - Brilliantov, Nikolai V. A1 - Sremcevic, Miodrag A1 - Spahn, Frank A1 - Krivov, Alexander V. T1 - Stochastic circumplanetary dynamics of rotating non-spherical dust particles JF - Planetary and space science N2 - We develop a model of stochastic radiation pressure for rotating non-spherical particles and apply the model to circumplanetary dynamics of dust grains. The stochastic properties of the radiation pressure are related to the ensemble-averaged characteristics of the rotating particles, which are given in terms of the rotational time-correlation function of a grain. We investigate the model analytically and show that an ensemble of particle trajectories demonstrates a diffusion-like behaviour. The analytical results are compared with numerical simulations, performed for the motion of the dusty ejecta from Deimos in orbit around Mars. We find that the theoretical predictions are in a good agreement with the simulation results. The agreement however deteriorates at later time, when the impact of non-linear terms, neglected in the analytic approach, becomes significant. Our results indicate that the stochastic modulation of the radiation pressure can play an important role in the circumplanetary dynamics of dust and may in case of some dusty systems noticeably alter an optical depth. (c) 2006 Elsevier Ltd. All rights reserved. KW - Mars KW - Deimos KW - ejecta KW - stochastics KW - radiation pressure Y1 - 2006 U6 - https://doi.org/10.1016/j.pss.2006.05.006 SN - 0032-0633 VL - 54 IS - 9-10 SP - 855 EP - 870 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Becker, George D. A1 - Pettini, Max A1 - Rafelski, Marc A1 - Boera, Elisa A1 - Christensen, Lise A1 - Cupani, Guido A1 - Ellison, Sara L. A1 - Farina, Emanuele Paolo A1 - Fumagalli, Michele A1 - Lopez, Sebastian A1 - Neeleman, Marcel A1 - Ryan-Weber, Emma A1 - Worseck, Gabor T1 - The Evolution of OI over 3.2 < z < 6.5: Reionization of the Circumgalactic Medium JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - We present a survey for metal absorption systems traced by neutral oxygen over 3.2 < z < 6.5. Our survey uses Keck/ESI and VLT/X-Shooter spectra of 199 QSOs with redshifts up to 6.6. In total, we detect 74 OI absorbers, of which 57 are separated from the background QSO by more than 5000 km s(-1). We use a maximum likelihood approach to fit the distribution of OI lambda 1302 equivalent widths in bins of redshift and from this determine the evolution in number density of absorbers with W-1302 > 0.05 angstrom, of which there are 49 nonproximate systems in our sample. We find that the number density does not monotonically increase with decreasing redshift, as would naively be expected from the buildup of metal-enriched circumgalactic gas with time. The number density over 4.9 < z < 5.7 is a factor of 1.7-4.1 lower (68% confidence) than that over 5.7 < z < 6.5, with a lower value at z < 5.7 favored with 99% confidence. This decrease suggests that the fraction of metals in a low-ionization phase is larger at z similar to 6 than at lower redshifts. Absorption from highly ionized metals traced by CIV is also weaker in higher-redshift OI systems, supporting this picture. The evolution of OI absorbers implies that metal-enriched circumgalactic gas at z similar to 6 is undergoing an ionization transition driven by a strengthening ultraviolet background. This in turn suggests that the reionization of the diffuse intergalactic medium may still be ongoing at or only recently ended by this epoch. Y1 - 2019 U6 - https://doi.org/10.3847/1538-4357/ab3eb5 SN - 0004-637X SN - 1538-4357 VL - 883 IS - 2 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Wilkin, Kyle J. A1 - Parrish, Robert M. A1 - Yang, Jie A1 - Wolf, Thomas J. A. A1 - Nunes, J. Pedro F. A1 - Gühr, Markus A1 - Li, Renkai A1 - Shen, Xiaozhe A1 - Zheng, Qiang A1 - Wang, Xijie A1 - Martinez, Todd J. A1 - Centurion, Martin T1 - Diffractive imaging of dissociation and ground-state dynamics in a complex molecule JF - Physical review : A, Atomic, molecular, and optical physics N2 - We have investigated the structural dynamics in photoexcited 1,2-diiodotetrafluoroethane molecules (C2F4I2) in the gas phase experimentally using ultrafast electron diffraction and theoretically using FOMO-CASCI excited-state dynamics simulations. The molecules are excited by an ultraviolet femtosecond laser pulse to a state characterized by a transition from the iodine 5p perpendicular to orbital to a mixed 5p parallel to sigma hole and CF2 center dot antibonding orbital, which results in the cleavage of one of the carbon-iodine bonds. We have observed, with sub-Angstrom resolution, the motion of the nuclear wave packet of the dissociating iodine atom followed by coherent vibrations in the electronic ground state of the C2F4I radical. The radical reaches a stable classical (nonbridged) structure in less than 200 fs. Y1 - 2019 U6 - https://doi.org/10.1103/PhysRevA.100.023402 SN - 2469-9926 SN - 2469-9934 VL - 100 IS - 2 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Wolf, Thomas J. A. A1 - Parrish, Robert M. A1 - Myhre, Rolf H. A1 - Martinez, Todd J. A1 - Koch, Henrik A1 - Gühr, Markus T1 - Observation of Ultrafast Intersystem Crossing in Thymine by Extreme Ultraviolet Time-Resolved Photoelectron Spectroscopy JF - The journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment & general theory N2 - We studied the photoinduced ultrafast relaxation dynamics of the nucleobase thymine using gas-phase time-resolved photoelectron spectroscopy. By employing extreme ultraviolet pulses from high harmonic generation for photoionization, we substantially extend our spectral observation window with respect to previous studies. This enables us to follow relaxation of the excited state population all the way to low-lying electronic states including the ground state. In thymine, we observe relaxation from the optically bright (1)pi pi* state of thymine to a dark (1)n pi* state within 80 +/- 30 fs. The (1)n pi* state relaxes further within 3.5 +/- 0.3 ps to a low-lying electronic state. By comparison with quantum chemical simulations, we can unambiguously assign its spectroscopic signature to the (3)pi pi* state. Hence, our study draws a comprehensive picture of the relaxation mechanism of thymine including ultrafast intersystem crossing to the triplet manifold. Y1 - 2019 U6 - https://doi.org/10.1021/acs.jpca.9b05573 SN - 1089-5639 SN - 1520-5215 VL - 123 IS - 32 SP - 6897 EP - 6903 PB - American Chemical Society CY - Washington 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 - Tubiana, C. A1 - Rinaldi, G. A1 - Guettler, C. A1 - Snodgrass, C. A1 - Shi, X. A1 - Hu, X. A1 - Marschall, R. A1 - Fulle, M. A1 - Bockeele-Morvan, D. A1 - Naletto, G. A1 - Capaccioni, F. A1 - Sierks, H. A1 - Arnold, G. A1 - Barucci, M. A. A1 - Bertaux, J-L A1 - Bertini, I A1 - Bodewits, D. A1 - Capria, M. T. A1 - Ciarniello, M. A1 - Cremonese, G. A1 - Crovisier, J. A1 - Da Deppo, V A1 - Debei, S. A1 - De Cecco, M. A1 - Deller, J. A1 - De Sanctis, M. C. A1 - Davidsson, B. A1 - Doose, L. A1 - Erard, S. A1 - Filacchione, G. A1 - Fink, U. A1 - Formisano, M. A1 - Fornasier, S. A1 - Gutierrez, P. J. A1 - Ip, W-H A1 - Ivanovski, S. A1 - Kappel, David A1 - Keller, H. U. A1 - Kolokolova, L. A1 - Koschny, D. A1 - Krueger, H. A1 - La Forgia, F. A1 - Lamy, P. L. A1 - Lara, L. M. A1 - Lazzarin, M. A1 - Levasseur-Regourd, A. C. A1 - Lin, Z-Y A1 - Longobardo, A. A1 - Lopez-Moreno, J. J. A1 - Marzari, F. A1 - Migliorini, A. A1 - Mottola, S. A1 - Rodrigo, R. A1 - Taylor, F. A1 - Toth, I A1 - Zakharov, V T1 - Diurnal variation of dust and gas production in comet 67P/Churyumov-Gerasimenko at the inbound equinox as seen by OSIRIS and VIRTIS-M on board Rosetta JF - Astronomy and astrophysics : an international weekly journal N2 - Context. On 27 April 2015, when comet 67P/Churyumov-Gerasimenko was at 1.76 au from the Sun and moving toward perihelion, the OSIRIS and VIRTIS-M instruments on board the Rosetta spacecraft simultaneously observed the evolving dust and gas coma during a complete rotation of the comet. Aims. We aim to characterize the spatial distribution of dust, H2O, and CO2 gas in the inner coma. To do this, we performed a quantitative analysis of the release of dust and gas and compared the observed H2O production rate with the rate we calculated using a thermophysical model. Methods. For this study we selected OSIRIS WAC images at 612 nm (dust) and VIRTIS-M image cubes at 612 nm, 2700 nm (H2O emission band), and 4200 nm (CO2 emission band). We measured the average signal in a circular annulus to study the spatial variation around the comet, and in a sector of the annulus to study temporal variation in the sunward direction with comet rotation, both at a fixed distance of 3.1 km from the comet center. Results. The spatial correlation between dust and water, both coming from the sunlit side of the comet, shows that water is the main driver of dust activity in this time period. The spatial distribution of CO2 is not correlated with water and dust. There is no strong temporal correlation between the dust brightness and water production rate as the comet rotates. The dust brightness shows a peak at 0 degrees subsolar longitude, which is not pronounced in the water production. At the same epoch, there is also a maximum in CO2 production. An excess of measured water production with respect to the value calculated using a simple thermophysical model is observed when the head lobe and regions of the southern hemisphere with strong seasonal variations are illuminated (subsolar longitude 270 degrees-50 degrees). A drastic decrease in dust production when the water production (both measured and from the model) displays a maximum occurs when typical northern consolidated regions are illuminated and the southern hemisphere regions with strong seasonal variations are instead in shadow (subsolar longitude 50 degrees-90 degrees). Possible explanations of these observations are presented and discussed. KW - comets: general KW - comets: individual: 67P/Churyumov-Gerasimenko KW - methods: data analysis Y1 - 2019 U6 - https://doi.org/10.1051/0004-6361/201834869 SN - 1432-0746 VL - 630 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Baran, Andrzej S. A1 - Telting, J. H. A1 - Jeffery, C. Simon A1 - Ostensen, R. H. A1 - Vos, Joris A1 - Reed, M. D. A1 - Vŭcković, Maja T1 - K2 observations of the sdBV plus dM/bd binaries PHL457 and EQPsc JF - Monthly notices of the Royal Astronomical Society N2 - We present an analysis of two pulsating subdwarf B stars PHL 457 and EQ Psc observed during the K2 mission. The K2 light curves of both stars show variation consistent with irradiation of a cooler companion by the hot subdwarf. They also show higher frequency oscillations consistent with pulsation. Using new spectroscopic data, we measured the radial velocity, effective temperature, surface gravity, and helium abundance of both hot subdwarfs as a function of orbital phase. We confirm the previously published spectroscopic orbit of PHL 457, and present the first spectroscopic orbit of EQ Psc. The orbital periods are 0.313 and 0.801 d, respectively. For EQPsc, we find a strong correlation between T-eff and orbital phase, due to contribution of light from the irradiated companion. We calculated amplitude spectra, identified significant pulsation frequencies, and searched for multiplets and asymptotic period spacings. By means of multiplets and period spacing, we identified the degrees of several pulsation modes in each star. The g-mode multiplets indicate subsynchronous core rotation with periods of 4.6 d (PHL 457) and 9.4 d (EQ Psc). We made spectral energy disctribution (SED) fits of PHL 457 and EQ Psc using available broad-band photometry and Gaia data. While the SED of PHL 457 shows no evidence of a cool companion, the SED for EQPsc clearly shows an infrared (IR) access consistent with a secondary with a temperature of about 6800K and a radius of 0.23 R-circle dot. This is the first detection of an IR access in any sdB + dM binary. KW - binaries: general KW - stars: individual (PHL 457, EQ Psc) KW - stars: oscillations (including pulsations) Y1 - 2019 U6 - https://doi.org/10.1093/mnras/stz2209 SN - 0035-8711 SN - 1365-2966 VL - 489 IS - 2 SP - 1556 EP - 1571 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Eliazar, Iddo A1 - Metzler, Ralf A1 - Reuveni, Shlomi T1 - Poisson-process limit laws yield Gumbel max-min and min-max JF - Physical review : E, Statistical, nonlinear and soft matter physics N2 - “A chain is only as strong as its weakest link” says the proverb. But what about a collection of statistically identical chains: How long till all chains fail? The answer to this question is given by the max-min of a matrix whose (i,j)entry is the failure time of link j of chain i: take the minimum of each row, and then the maximum of the rows' minima. The corresponding min-max is obtained by taking the maximum of each column, and then the minimum of the columns' maxima. The min-max applies to the storage of critical data. Indeed, consider multiple backup copies of a set of critical data items, and consider the (i,j) matrix entry to be the time at which item j on copy i is lost; then, the min-max is the time at which the first critical data item is lost. In this paper we address random matrices whose entries are independent and identically distributed random variables. We establish Poisson-process limit laws for the row's minima and for the columns' maxima. Then, we further establish Gumbel limit laws for the max-min and for the min-max. The limit laws hold whenever the entries' distribution has a density, and yield highly applicable approximation tools and design tools for the max-min and min-max of large random matrices. A brief of the results presented herein is given in: Gumbel central limit theorem for max-min and min-max Y1 - 2019 U6 - https://doi.org/10.1103/PhysRevE.100.022129 SN - 2470-0045 SN - 2470-0053 VL - 100 IS - 2 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Eliazar, Iddo A1 - Metzler, Ralf A1 - Reuveni, Shlomi T1 - Gumbel central limit theorem for max-min and min-max JF - Physical review : E, Statistical, nonlinear and soft matter physics N2 - The max-min and min-max of matrices arise prevalently in science and engineering. However, in many real-world situations the computation of the max-min and min-max is challenging as matrices are large and full information about their entries is lacking. Here we take a statistical-physics approach and establish limit laws—akin to the central limit theorem—for the max-min and min-max of large random matrices. The limit laws intertwine random-matrix theory and extreme-value theory, couple the matrix dimensions geometrically, and assert that Gumbel statistics emerge irrespective of the matrix entries' distribution. Due to their generality and universality, as well as their practicality, these results are expected to have a host of applications in the physical sciences and beyond. Y1 - 2019 U6 - https://doi.org/10.1103/PhysRevE.100.020104 SN - 2470-0045 SN - 2470-0053 VL - 100 IS - 2 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Soupiona, Ourania A1 - Samaras, Stefanos A1 - Ortiz-Amezcua, Pablo A1 - Böckmann, Christine A1 - Papayannis, Alexandros D. A1 - Moreira, Gregori De Arruda A1 - Benavent-Oltra, Jose Antonio A1 - Guerrero-Rascado, Juan Luis A1 - Bedoya-Velásquez, Andres Esteban A1 - Olmo-Reyes, Francisco José A1 - Román, Roberto A1 - Kokkalis, Panagiotis A1 - Mylonaki, Maria A1 - Alados-Arboledas, Lucas A1 - Papanikolaou, Christina Anna A1 - Foskinis, Romanos T1 - Retrieval of optical and microphysical properties of transported Saharan dust over Athens and Granada based on multi-wavelength Raman lidar measurements: Study of the mixing processes JF - Atmospheric environment : air pollution ; emissions, transport and dispersion, transformation, deposition effects, micrometeorology, urban atmosphere, global atmosphere N2 - In this paper we extract the aerosol microphysical properties for a collection of mineral dust cases measured by multi-wavelength depolarization Raman lidar systems located at the National Technical University of Athens (NTUA, Athens, Greece) and the Andalusian Institute for Earth System Research (IISTA-CEAMA, Granada, Spain). The lidar-based retrievals were carried out with the Spheroidal Inversion eXperiments software tool (SphInX) developed at the University of Potsdam (Germany). The software uses regularized inversion of a two-dimensional enhancement of the Mie model based on the spheroid-particle approximation with the aspect ratio determining the particle shape. The selection of the cases was based on the transport time from the source regions to the measuring sites. The aerosol optical depth as measured by AERONET ranged from 0.27 to 0.54 (at 500 nm) depending on the intensity of each event. Our analysis showed the hourly mean particle linear depolarization ratio and particle lidar ratio values at 532 nm ranging from 11 to 34% and from 42 to 79 sr respectively, depending on the mixing status, the corresponding air mass pathways and their transport time. Cases with shorter transport time showed good agreement in terms of the optical and SphInX-retrieved microphysical properties between Athens and Granada providing a complex refractive index value equal to 1.4 + 0.004i. On the other hand, the results for cases with higher transport time deviated from the aforementioned ones as well as from each other, providing, in particular, an imaginary part of the refractive index ranging from 0.002 to 0.005. Reconstructions of two-dimensional shape-size distributions for each selected layer showed that the dominant effective particle shape was prolate with diverse spherical contributions. The retrieved volume concentrations reflect overall the intensity of the episodes. Y1 - 2019 U6 - https://doi.org/10.1016/j.atmosenv.2019.116824 SN - 1352-2310 SN - 1873-2844 VL - 214 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Pittarello, Lidia A1 - Goderis, Steven A1 - Soens, Bastien A1 - McKibbin, Seann J. A1 - Giuli, Gabriele A1 - Bariselli, Federico A1 - Dias, Bruno A1 - Helber, Bernd A1 - Lepore, Giovanni Orazio A1 - Vanhaecke, Frank A1 - Köberl, Christian A1 - Magin, Thierry E. A1 - Claeys, Philippe T1 - Meteoroid atmospheric entry investigated with plasma flow experiments: Petrography and geochemistry of the recovered material JF - Icarus : international journal of solar system studies N2 - Melting experiments attempting to reproduce some of the processes affecting asteroidal and cometary material during atmospheric entry have been performed in a high enthalpy facility. For the first time with the specific experimental setup, the resulting material has been recovered, studied, and compared with natural analogues, focusing on the thermal and redox reactions triggered by interaction between the melt and the atmospheric gases under high temperature and low pressure conditions. Experimental conditions were tested across a range of parameters, such as heat flux, experiment duration, and pressure, using two types of sample holders materials, namely cork and graphite. A basalt served as asteroidal analog and to calibrate the experiments, before melting a H5 ordinary chondrite meteorite. The quenched melt recovered after the experiments has been analyzed by mu-XRF, EDS-SEM, EMPA, LA-ICP-MS, and XANES spectroscopy. The glass formed from the basalt is fairly homogeneous, depleted in highly volatile elements (e.g., Na, K), relatively enriched in moderately siderophile elements (e.g., Co, Ni), and has reached an equilibrium redox state with a lower Fe3+/Fe-tot ratio than that in the starting material. Spherical objects, enriched in SiO2, Na2O and K2O, were observed, inferring condensation from the vaporized material. Despite instantaneous quenching, the melt formed from the ordinary chondrite shows extensive crystallization of mostly olivine and magnetite, the latter indicative of oxygen fugacity compatible with presence of both Fe2+ and Fe3+. Similar features have been observed in natural meteorite fusion crusts and in micrometeorites, implying that, at least in terms of maximum temperature reached and chemical reactions, the experiments have successfully reproduced the conditions likely encountered by extraterrestrial material following atmospheric entry. KW - Melting experiments KW - Atmospheric entry KW - Meteorites KW - Fusion crust KW - Redox Y1 - 2019 U6 - https://doi.org/10.1016/j.icarus.2019.04.033 SN - 0019-1035 SN - 1090-2643 VL - 331 SP - 170 EP - 178 PB - Elsevier CY - San Diego ER - TY - JOUR A1 - Poeschel, Thorsten A1 - Brilliantov, Nikolai V. A1 - Formella, Arno T1 - Impact of high-energy tails on granular gas properties JF - Physical review : E, Statistical, nonlinear and soft matter physics N2 - The velocity distribution function of granular gases in the homogeneous cooling state as well as some heated granular gases decays for large velocities as f proportional to exp(-const x nu). That is, its high-energy tail is overpopulated as compared with the Maxwell distribution. At the present time, there is no theory to describe the influence of the tail on the kinetic characteristics of granular gases. We develop an approach to quantify the overpopulated tail and analyze its impact on granular gas properties, in particular on the cooling coefficient. We observe and explain anomalously slow relaxation of the velocity distribution function to its steady state. Y1 - 2006 U6 - https://doi.org/10.1103/PhysRevE.74.041302 SN - 1539-3755 SN - 1550-2376 VL - 74 IS - 4 PB - The American Physical Society CY - College Park ER - TY - JOUR A1 - Goychuk, Igor T1 - Fractional Bhatnagar-Gross-Krook kinetic equation JF - The European physical journal : B, Condensed matter and complex systems N2 - The linear Boltzmann equation approach is generalized to describe fractional superdiffusive transport of the Levy walk type in external force fields. The time distribution between scattering events is assumed to have a finite mean value and infinite variance. It is completely characterized by the two scattering rates, one fractional and a normal one, which defines also the mean scattering rate. We formulate a general fractional linear Boltzmann equation approach and exemplify it with a particularly simple case of the Bohm and Gross scattering integral leading to a fractional generalization of the Bhatnagar, Gross and Krook kinetic equation. Here, at each scattering event the particle velocity is completely randomized and takes a value from equilibrium Maxwell distribution at a given fixed temperature. We show that the retardation effects are indispensable even in the limit of infinite mean scattering rate and argue that this novel fractional kinetic equation provides a viable alternative to the fractional Kramers-Fokker-Planck (KFP) equation by Barkai and Silbey and its generalization by Friedrich et al. based on the picture of divergent mean time between scattering events. The case of divergent mean time is also discussed at length and compared with the earlier results obtained within the fractional KFP. Also a phenomenological fractional BGK equation without retardation effects is proposed in the limit of infinite scattering rates. It cannot be, however, rigorously derived from a scattering model, being rather clever postulated. It this respect, this retardationless equation is similar to the fractional KFP by Barkai and Silbey. However, it corresponds to the opposite, much more physical limit and, therefore, also presents a viable alternative. Y1 - 2017 U6 - https://doi.org/10.1140/epjb/e2017-80297-x SN - 1434-6028 SN - 1434-6036 VL - 90 PB - Springer CY - New York ER - TY - JOUR A1 - Delle Side, Domenico A1 - Nassisi, Vincenzo A1 - Pennetta, Cecilia A1 - Alifano, Pietro A1 - Di Salvo, Marco A1 - Tala, Adelfia A1 - Chechkin, Aleksei V. A1 - Seno, Flavio A1 - Trovato, Antonio T1 - Bacterial bioluminescence onset and quenching: a dynamical model for a quorum sensing-mediated property JF - Royal Society Open Science N2 - We present an effective dynamical model for the onset of bacterial bioluminescence, one of the most studied quorum sensing-mediated traits. Our model is built upon simple equations that describe the growth of the bacterial colony, the production and accumulation of autoinducer signal molecules, their sensing within bacterial cells, and the ensuing quorum activation mechanism that triggers bioluminescent emission. The model is directly tested to quantitatively reproduce the experimental distributions of photon emission times, previously measured for bacterial colonies of Vibrio jasicida, a luminescent bacterium belonging to the Harveyi clade, growing in a highly drying environment. A distinctive and novel feature of the proposed model is bioluminescence ‘quenching’ after a given time elapsed from activation. Using an advanced fitting procedure based on the simulated annealing algorithm, we are able to infer from the experimental observations the biochemical parameters used in the model. Such parameters are in good agreement with the literature data. As a further result, we find that, at least in our experimental conditions, light emission in bioluminescent bacteria appears to originate from a subtle balance between colony growth and quorum activation due to autoinducers diffusion, with the two phenomena occurring on the same time scale. This finding is consistent with a negative feedback mechanism previously reported for Vibrio harveyi. KW - quorum sensing KW - bioluminescence KW - biophysical model KW - Vibrio Harveyi clade KW - oxygen quenching KW - Gompertz growth function Y1 - 2017 U6 - https://doi.org/10.1098/rsos.171586 SN - 2054-5703 VL - 4 PB - Royal Society CY - London ER - TY - JOUR A1 - Javanainen, Matti A1 - Martinez-Seara, Hector A1 - Metzler, Ralf A1 - Vattulainen, Ilpo T1 - Diffusion of Integral Membrane Proteins in Protein-Rich Membranes JF - The journal of physical chemistry letters N2 - The lateral diffusion of embedded proteins along lipid membranes in protein-poor conditions has been successfully described in terms of the Saffman-Delbruck (SD) model, which predicts that the protein diffusion coefficient D is weakly dependent on its radius R as D proportional to ln(1/R). However, instead of being protein-poor, native cell membranes are extremely crowded with proteins. On the basis of extensive molecular simulations, we here demonstrate that protein crowding of the membrane at physiological levels leads to deviations from the SD relation and to the emergence of a stronger Stokes-like dependence D proportional to 1/R. We propose that this 1/R law mainly arises due to geometrical factors: smaller proteins are able to avoid confinement effects much better than their larger counterparts. The results highlight that the lateral dynamics in the crowded setting found in native membranes is radically different from protein-poor conditions and plays a significant role in formation of functional multiprotein complexes. Y1 - 2017 U6 - https://doi.org/10.1021/acs.jpclett.7b01758 SN - 1948-7185 VL - 8 SP - 4308 EP - 4313 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Palyulin, Vladimir V. A1 - Mantsevich, Vladimir N. A1 - Klages, Rainer A1 - Metzler, Ralf A1 - Chechkin, Aleksei V. T1 - Comparison of pure and combined search strategies for single and multiple targets JF - The European physical journal : B, Condensed matter and complex systems N2 - We address the generic problem of random search for a point-like target on a line. Using the measures of search reliability and efficiency to quantify the random search quality, we compare Brownian search with Levy search based on long-tailed jump length distributions. We then compare these results with a search process combined of two different long-tailed jump length distributions. Moreover, we study the case of multiple targets located by a Levy searcher. Y1 - 2017 U6 - https://doi.org/10.1140/epjb/e2017-80372-4 SN - 1434-6028 SN - 1434-6036 VL - 90 SP - 20 EP - 37 PB - Springer CY - New York ER - TY - JOUR A1 - Caetano, Daniel L. Z. A1 - de Carvalho, Sidney J. A1 - Metzler, Ralf A1 - Cherstvy, Andrey G. T1 - Critical adsorption of periodic and random polyampholytes onto charged surfaces JF - Physical chemistry, chemical physics : a journal of European Chemical Societies N2 - How different are the properties of critical adsorption of polyampholytes and polyelectrolytes onto charged surfaces? How important are the details of polyampholyte charge distribution on the onset of critical adsorption transition? What are the scaling relations governing the dependence of critical surface charge density on salt concentration in the surrounding solution? Here, we employ Metropolis Monte Carlo simulations and uncover the scaling relations for critical adsorption for quenched periodic and random charge distributions along the polyampholyte chains. We also evaluate and discuss the dependence of the adsorbed layer width on solution salinity and details of the charge distribution. We contrast our findings to the known results for polyelectrolyte adsorption onto oppositely charged surfaces, in particular, their dependence on electrolyte concentration. Y1 - 2017 U6 - https://doi.org/10.1039/c7cp04040g SN - 1463-9076 SN - 1463-9084 VL - 19 SP - 23397 EP - 23413 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Muench, Thomas A1 - Kipfstuhl, Sepp A1 - Freitag, Johannes A1 - Meyer, Hanno A1 - Laepple, Thomas T1 - Constraints on post-depositional isotope modifications in East Antarctic firn from analysing temporal changes of isotope profiles JF - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union N2 - The isotopic composition of water in ice sheets is extensively used to infer past climate changes. In low-accumulation regions their interpretation is, however, challenged by poorly constrained effects that may influence the initial isotope signal during and after deposition of the snow. This is reflected in snow-pit isotope data from Kohnen Station, Antarctica, which exhibit a seasonal cycle but also strong interannual variations that contradict local temperature observations. These inconsistencies persist even after averaging many profiles and are thus not explained by local stratigraphic noise. Previous studies have suggested that post-depositional processes may significantly influence the isotopic composition of East Antarctic firn. Here, we investigate the importance of post-depositional processes within the open-porous firn (greater than or similar to 10 cm depth) at Kohnen Station by separating spatial from temporal variability. To this end, we analyse 22 isotope profiles obtained from two snow trenches and examine the temporal isotope modifications by comparing the new data with published trench data extracted 2 years earlier. The initial isotope profiles undergo changes over time due to downward advection, firn diffusion and densification in magnitudes consistent with independent estimates. Beyond that, we find further modifications of the original isotope record to be unlikely or small in magnitude (<< 1 parts per thousand RMSD). These results show that the discrepancy between local temperatures and isotopes most likely originates from spatially coherent processes prior to or during deposition, such as precipitation intermittency or systematic isotope modifications acting on drifting or loose surface snow. Y1 - 2017 U6 - https://doi.org/10.5194/tc-11-2175-2017 SN - 1994-0416 SN - 1994-0424 VL - 11 SP - 2175 EP - 2188 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Starkenburg, Else A1 - Martin, Nicolas A1 - Youakim, Kris A1 - Aguado, David S. A1 - Allende Prieto, Carlos A1 - Arentsen, Anke A1 - Bernard, Edouard J. A1 - Bonifacio, Piercarlo A1 - Caffau, Elisabetta A1 - Carlberg, Raymond G. A1 - Cote, Patrick A1 - Fouesneau, Morgan A1 - Francois, Patrick A1 - Franke, Oliver A1 - Gonzalez Hernandez, Jonay I. A1 - Gwyn, Stephen D. J. A1 - Hill, Vanessa A1 - Ibata, Rodrigo A. A1 - Jablonka, Pascale A1 - Longeard, Nicolas A1 - McConnachie, Alan W. A1 - Navarro, Julio F. A1 - Sanchez-Janssen, Ruben A1 - Tolstoy, Eline A1 - Venn, Kim A. T1 - The Pristine survey - I. Mining the Galaxy for the most metal-poor stars JF - Monthly notices of the Royal Astronomical Society N2 - We present the Pristine survey, a new narrow-band photometric survey focused on the metallicity-sensitive Ca H&K lines and conducted in the Northern hemisphere with the wide-field imager MegaCam on the Canada-France-Hawaii Telescope. This paper reviews our overall survey strategy and discusses the data processing and metallicity calibration. Additionally we review the application of these data to the main aims of the survey, which are to gather a large sample of the most metal-poor stars in the Galaxy, to further characterize the faintest Milky Way satellites, and to map the (metal-poor) substructure in the Galactic halo. The current Pristine footprint comprises over 1000 deg(2) in the Galactic halo ranging from b similar to 30 degrees to similar to 78 degrees and covers many known stellar substructures. We demonstrate that, for Sloan Digital Sky Survey (SDSS) stellar objects, we can calibrate the photometry at the 0.02-mag level. The comparison with existing spectroscopic metallicities from SDSS/Sloan Extension for Galactic Understanding and Exploration (SEGUE) and Large Sky Area Multi-Object Fiber Spectroscopic Telescope shows that, when combined with SDSS broad-band g and i photometry, we can use the CaHK photometry to infer photometric metallicities with an accuracy of similar to 0.2 dex from [Fe/H] = -0.5 down to the extremely metal-poor regime ([Fe/H] < -3.0). After the removal of various contaminants, we can efficiently select metal-poor stars and build a very complete sample with high purity. The success rate of uncovering [Fe/H](SEGUE) < -3.0 stars among [Fe/H](Pristine) < -3.0 selected stars is 24 per cent, and 85 per cent of the remaining candidates are still very metal poor ([Fe/H]<-2.0). We further demonstrate that Pristine is well suited to identify the very rare and pristine Galactic stars with [Fe/H] < -4.0, which can teach us valuable lessons about the early Universe. KW - stars: abundances KW - Galaxy: abundances KW - Galaxy: evolution KW - Galaxy: formation KW - Galaxy: halo KW - galaxies: dwarf Y1 - 2017 U6 - https://doi.org/10.1093/mnras/stx1068 SN - 0035-8711 SN - 1365-2966 VL - 471 SP - 2587 EP - 2604 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Arora, Ashima A1 - Mawass, Mohamad-Assaad A1 - Sandig, Oliver A1 - Luo, Chen A1 - Uenal, Ahmet A. A1 - Radu, Florin A1 - Valencia, Sergio A1 - Kronast, Florian T1 - Spatially resolved investigation of all optical magnetization switching in TbFe alloys JF - Scientific reports N2 - Optical control of magnetization using femtosecond laser without applying any external magnetic field offers the advantage of switching magnetic states at ultrashort time scales. Recently, all-optical helicity-dependent switching (AO-HDS) has drawn a significant attention for potential information and data storage device applications. In this work, we employ element and magnetization sensitive photoemission electron microscopy (PEEM) to investigate the role of heating in AO-HDS for thin films of the rare-earth transition-metal alloy TbFe. Spatially resolved measurements in a 3–5 μm sized stationary laser spot demonstrate that AO-HDS is a local phenomenon in the vicinity of thermal demagnetization in a ‘ring’ shaped region. The efficiency of AO-HDS further depends on a local temperature profile around the demagnetized region and thermally activated domain wall motion. We also demonstrate that the thickness of the film determines the preferential switching direction for a particular helicity. Y1 - 2017 U6 - https://doi.org/10.1038/s41598-017-09615-1 SN - 2045-2322 VL - 7 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Mor, Selene A1 - Herzog, Marc A1 - Golez, Denis A1 - Werner, Philipp A1 - Eckstein, Martin A1 - Katayama, Naoyuki A1 - Nohara, Minoru A1 - Takagi, Hide A1 - Mizokawa, Takashi A1 - Monney, Claude A1 - Staehler, Julia T1 - Ultrafast Electronic Band Gap Control in an Excitonic Insulator JF - Physical review letters N2 - We report on the nonequilibrium dynamics of the electronic structure of the layered semiconductor Ta2NiSe5 investigated by time-and angle-resolved photoelectron spectroscopy. We show that below the critical excitation density of F-C = 0.2 mJ cm(-2), the band gap narrows transiently, while it is enhanced above FC. Hartree-Fock calculations reveal that this effect can be explained by the presence of the low-temperature excitonic insulator phase of Ta2NiSe5, whose order parameter is connected to the gap size. This work demonstrates the ability to manipulate the band gap of Ta2NiSe5 with light on the femtosecond time scale. Y1 - 2017 U6 - https://doi.org/10.1103/PhysRevLett.119.086401 SN - 0031-9007 SN - 1079-7114 VL - 119 SP - 11559 EP - 11567 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Yoon, P. H. A1 - Lopez, R. A. A1 - Vafin, Sergei A1 - Kim, S. A1 - Schlickeiser, R. T1 - Spontaneous emission of Alfvenic fluctuations JF - Plasma physics and controlled fusion N2 - Low-frequency fluctuations are pervasively observed in the solar wind. The present paper theoretically calculates the steady state spectra of low-frequency electromagnetic (EM) fluctuations of the Alfvenic type for thermal equilibrium plasma. The analysis is based upon a recently formulated theory of spontaneously emitted EM fluctuations in magnetized thermal plasmas. It is found that the fluctuations in the magnetosonic mode branch is constant, while the kinetic Alfvenic mode spectrum is dependent on a form factor that is a function of perpendicular wave number. Potential applicability of the present work in the wider context of heliospheric research is also discussed. KW - spontaneous emission KW - kinetic Alfven KW - magnetosonic Y1 - 2017 U6 - https://doi.org/10.1088/1361-6587/aa77c3 SN - 0741-3335 SN - 1361-6587 VL - 59 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Cherstvy, Andrey G. T1 - Shape Morphologies of Icosahedral Two-Component Vesicles JF - The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces & biophysical chemistry N2 - What are the features of partitioning of crystalline materials on the surface of a two-component icosahedral vesicle? We model the response of the rigid hardly stretchable crystalline icosahedra upon addition of a softer component on its surface. We demonstrate how the soft phase "invades" the shell regions with the highest elastic energy density around 12 5-fold topological defects. We explore the phase diagram of these inhomogeneous shells as a function of the soft material fraction, shell radius, and elastic moduli of the two phases. The findings are compared with the recent computer simulation findings, and their biological relevance, for example, for the structure of icosahedral viruses, is also discussed. Y1 - 2017 U6 - https://doi.org/10.1021/acs.jpcb.7b02440 SN - 1520-6106 VL - 121 SP - 7484 EP - 7491 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Baptista, Murilo da Silva A1 - Grebogi, Celso A1 - Koberle, Roland T1 - Dynamically multilayered visual system of the multifractal fly JF - Physical review letters Y1 - 2006 U6 - https://doi.org/10.1103/PhysRevLett.97.178102 SN - 0031-9007 VL - 97 IS - 17 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Hamann, Wolf-Rainer A1 - Graefener, G. A1 - Liermann, A. T1 - The galactic WN stars - Spectral analyses with line-blanketed model atmospheres versus stellar evolution models with and without rotation JF - Astronomy and astrophysics : an international weekly journal N2 - Context. Very massive stars pass through the Wolf-Rayet (WR) stage before they finally explode. Details of their evolution have not yet been safely established, and their physics are not well understood. Their spectral analysis requires adequate model atmospheres, which have been developed step by step during the past decades and account in their recent version for line blanketing by the millions of lines from iron and iron-group elements. However, only very few WN stars have been re-analyzed by means of line-blanketed models yet. Aims. The quantitative spectral analysis of a large sample of Galactic WN stars with the most advanced generation of model atmospheres should provide an empirical basis for various studies about the origin, evolution, and physics of the Wolf-Rayet stars and their powerful winds. Methods. We analyze a large sample of Galactic WN stars by means of the Potsdam Wolf-Rayet (PoWR) model atmospheres, which account for iron line blanketing and clumping. The results are compared with a synthetic population, generated from the Geneva tracks for massive star evolution. Results. We obtain a homogeneous set of stellar and atmospheric parameters for the GalacticWN stars, partly revising earlier results. Conclusions. Comparing the results of our spectral analyses of the Galactic WN stars with the predictions of the Geneva evolutionary calculations, we conclude that there is rough qualitative agreement. However, the quantitative discrepancies are still severe, and there is no preference for the tracks that account for the effects of rotation. It seems that the evolution of massive stars is still not satisfactorily understood. KW - stars : mass-loss KW - stars : winds, outflows KW - stars : Wolf-Rayet KW - stars : atmospheres KW - stars : early-type KW - stars : evolution Y1 - 2006 U6 - https://doi.org/10.1051/0004-6361:20065052 SN - 0004-6361 VL - 457 IS - 3 SP - 1015 EP - 1031 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Zaikin, Alexey A1 - Kurths, Jürgen T1 - Optimal length transportation hypothesis to model proteasome product size distribution JF - Journal of biological physics : emphasizing physical principles in biological research ; an international journal for the formulation and application of mathematical models in the biological sciences N2 - This paper discusses translocation features of the 20S proteasome in order to explain typical proteasome length distributions. We assume that the protein transport depends significantly on the fragment length with some optimal length which is transported most efficiently. By means of a simple one-channel model, we show that this hypothesis can explain both the one- and the three-peak length distributions found in experiments. A possible mechanism of such translocation is provided by so-called fluctuation-driven transport. KW - proteasome KW - protein translocation KW - stochastic process KW - ratchets Y1 - 2006 U6 - https://doi.org/10.1007/s10867-006-9014-z SN - 0092-0606 VL - 32 IS - 3-4 SP - 231 EP - 243 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Pico, Tamara A1 - Mitrovica, Jerry X. A1 - Perron, J. Taylor A1 - Ferrier, Ken L. A1 - Braun, Jean T1 - Influence of glacial isostatic adjustment on river evolution along the US mid-Atlantic coast JF - Earth & planetary science letters N2 - Long-term river evolution depends partly on crustal deformation, which shapes the topography crossed by rivers. On glacial timescales, ice-sheet growth and decay can produce crustal vertical motion of ∼10 mm/yr resulting from the solid Earth's adjustment to variations in ice and water loads, comparable to tectonically-driven rates in the most rapidly uplifting mountains on Earth. This process of glacial isostatic adjustment (GIA) can influence river courses and drainage basins substantially, particularly near former ice margins. We explore the extent to which GIA influenced the evolution of rivers along the United States east coast during the last glacial cycle. We compute gravitationally self-consistent GIA responses that incorporate recent constraints on the Laurentide Ice Sheet history through the last glacial build-up phase, and we connect the predicted variations in topography to abrupt changes in river dynamics recorded in the Hudson, Delaware, Susquehanna, and Potomac Rivers from 40 ka to present. To the extent that increases in sediment transport capacity imply increases in river incision rate, the GIA-driven changes in slope and drainage area are consistent with episodes of erosion and sedimentation observed in the Hudson, Delaware, and Potomac Rivers, but inconsistent with the observed accelerated river incision in the Susquehanna River at 30-14 ka. These analyses add to a growing body of evidence showing that GIA strongly influences river evolution over millennial timescales. KW - glacial-isostatic adjustment KW - US east coast river geomorphology KW - river dynamics on glacial timescales Y1 - 2019 U6 - https://doi.org/10.1016/j.epsl.2019.06.026 SN - 0012-821X SN - 1385-013X VL - 522 SP - 176 EP - 185 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Diercke, Andrea A1 - Kuckein, Christoph A1 - Denker, Carsten T1 - Dynamics and connectivity of an extended arch filament system JF - Astronomy and astrophysics : an international weekly journal N2 - Aims. In this study, we analyzed a filament system, which expanded between moving magnetic features (MMFs) of a decaying sunspot and opposite flux outside of the active region from the nearby quiet-Sun network. This configuration deviated from a classical arch filament system (AFS), which typically connects two pores in an emerging flux region. Thus, we called this system an extended AFS. We contrasted classical and extended AFSs with an emphasis on the complex magnetic structure of the latter. Furthermore, we examined the physical properties of the extended AFS and described its dynamics and connectivity. Methods. The extended AFS was observed with two instruments at the Dunn Solar Telescope (DST). The Rapid Oscillations in the Solar Atmosphere (ROSA) imager provided images in three different wavelength regions, which covered the dynamics of the extended AFS at different atmospheric heights. The Interferometric Bidimensional Spectropolarimeter (IBIS) provided spectroscopic Ha data and spectropolarimetric data that was obtained in the near-infrared (NIR) Call lambda 8542 angstrom line. We derived the corresponding line-of-sight (LOS) velocities and used He II lambda 304 angstrom extreme ultraviolet (EUV) images of the Atmospheric Imaging Assembly (AIA) and LOS magnetograms of the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) as context data. Results. The NIR Call Stokes-V maps are not suitable to definitively define a clear polarity inversion line and to classify this chromospheric structure. Nevertheless, this unusual AFS connects the MMFs of a decaying sunspot with the network field. At the southern footpoint, we measured that the flux decreases over time. We find strong downflow velocities at the footpoints of the extended AFS, which increase in a time period of 30 min. The velocities are asymmetric at both footpoints with higher velocities at the southern footpoint. An EUV brigthening appears in one of the arch filaments, which migrates from the northern footpoint toward the southern one. This activation likely influences the increasing redshift at the southern footpoint. Conclusions. The extended AFS exhibits a similar morphology as classical AFSs, for example, threaded filaments of comparable length and width. Major differences concern the connection from MMFs around the sunspot with the flux of the neighboring quietSun network, converging footpoint motions, and longer lifetimes of individual arch filaments of about one hour, while the extended AFS is still very dynamic. KW - methods: observational KW - Sun: filaments, prominences KW - Sun: activity KW - techniques: image processing KW - Sun: chromosphere Y1 - 2019 U6 - https://doi.org/10.1051/0004-6361/201935583 SN - 1432-0746 VL - 629 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Latour, Marilyn A1 - Dorsch, Matti A1 - Heber, Ulrich T1 - Heavy metal enrichment in the intermediate He-sdOB pulsator Feige 46 JF - Astronomy and astrophysics : an international weekly journal N2 - The intermediate He-enriched hot subdwarf star Feige 46 was recently reported as the second member of the V366 Aqr (or He-sdOBV) pulsating class. Feige 46 is very similar to the prototype of the class, LS IV-14 degrees 116, not only in terms of pulsational properties, but also in terms of atmospheric parameters and kinematic properties. LS IV-14 degrees 116 is additionally characterized by a very peculiar chemical composition, with extreme overabundances of the trans-iron elements Ge, Sr, Y, and Zr. We investigate the possibility that the similarity between the two pulsators extends to their chemical composition. We retrieved archived optical and UV spectroscopic observations of Feige 46 and performed an abundance analysis using model atmospheres and synthetic spectra computed with TLUSTY and SYNSPEC. In total, we derived abundances for 16 elements and provide upper limits for four additional elements. Using absorption lines in the optical spectrum of the star we measure an enrichment of more than 10 000x solar for yttrium and zirconium. The UV spectrum revealed that strontium is equally enriched. Our results confirm that Feige 46 is not only a member of the now growing group of heavy metal subdwarfs, but also has an abundance pattern that is remarkably similar to that of LS IV-14 degrees 116. KW - stars: abundances KW - subdwarfs KW - stars: individual: Feige 46 Y1 - 2019 U6 - https://doi.org/10.1051/0004-6361/201936247 SN - 1432-0746 VL - 629 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Saha, Sourav A1 - Owen, Lewis A. A1 - Orr, Elizabeth N. A1 - Caffee, Marc W. T1 - High-frequency Holocene glacier fluctuations in the Himalayan-Tibetan orogen JF - Quaternary science reviews : the international multidisciplinary research and review journal N2 - Holocene glacial chronostratigraphies in glaciated valleys spread throughout the Himalayan-Tibetan orogen, including the Himalaya, Tibet, Pamir, and Tian Shan, are developed using a landsystems approach, detailed geomorphic mapping, and new and published Be-10 surface exposure dating. New studies in the Kulti valley of Lahul and the Parkachik valley of the Nun Kun massif of the Himalaya of northern India define three glacier advances at similar to 14.7, 12.2, 0.5 ka, in addition to one historically dated late 19th Century advance in the Kulti valley, and one Late Holocene advance at similar to 0.2 ka in the Parkachik valley. Three major climatic groups (subdivided into five climatic zones) are defined across the orogen using Cluster Analysis (CA) and Principal Component Analysis (PCA) to identify glaciated regions with comparable climatic characteristics to evaluate the timing, and extent of Holocene glacier advances across these regions. Our regional analyses across the Himalayan-Tibetan orogen suggest at least one Lateglacial (similar to 15.3-11.8 ka) and five Himalayan-Tibetan Holocene glacial stages (HTHS) at similar to 11.5-9.5, similar to 8.8-7.7, similar to 7.0-3.2, similar to 2.3-1.0, and <1 ka. The extent (amplitude) of glacier advances in 77 glaciated valleys is reconstructed and defined using equilibrium-line altitudes (ELAs). Modern glacier hypsometries are also assessed to help explain the intra-regional variations in glacier amplitudes during each regional glacier advance. A linear inverse glacier flow model is used to decipher the net changes in temperature (Delta T) between periods of reconstructed regional glacier advances in 66 glaciated valleys across different climatic regions throughout the orogen. The Be-10, ELAs, and Delta T data suggest enhanced monsoonal and increased precipitation during the Early Holocene, followed by relative cooling and increased aridity during the Mid- and Late Holocene that influenced glaciation. The sublimation-dominated cold-based glaciers in the northern regions of Himalayan-Tibetan orogen are more affected during these shifts in climate than the temperate glaciers in the south. (C) 2019 Elsevier Ltd. All rights reserved. KW - Holocene KW - Glaciation Central Asia KW - Cosmogenic isotopes KW - Paleoclimate modeling KW - Equilibrium-line altitudes Y1 - 2019 U6 - https://doi.org/10.1016/j.quascirev.2019.07.021 SN - 0277-3791 VL - 220 SP - 372 EP - 400 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Liu, Ruo-Yu A1 - Yan, Huirong A1 - Zhang, Heshou T1 - Role of Anisotropic Diffusion of Particles JF - Physical review letters N2 - In this Letter, we propose that the x-ray and the TeV observations in the vicinity of Geminga can be understood in the framework of anisotropic diffusion of injected electrons or positrons. This interpretation only requires the turbulence in the vicinity of Geminga to be sub-Alfvenic with the local mean magnetic field direction approximately aligned with our line of sight towards Geminga, without invoking extreme conditions for the environment, such as an extremely small diffusion coefficient and a weak magnetic field of submicrogauss as suggested in previous literature. Y1 - 2019 U6 - https://doi.org/10.1103/PhysRevLett.123.221103 SN - 0031-9007 SN - 1079-7114 VL - 123 IS - 22 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Lever, Fabiano A1 - Ramelow, Sven A1 - Gühr, Markus T1 - Effects of time-energy correlation strength in molecular entangled photon spectroscopy JF - Physical review : A, Atomic, molecular, and optical physics N2 - In this paper, we explore the time-energy domain quantum-classical transition comparing a classical pump-probe experiment on a diatomic molecule to its quantum enhanced counterpart, where the pump and probe pulses are substituted by the signal and idler beams of a spontaneous parametric down conversion (SPDC) source. Absorption of biphotons generated with SPDC exploits quantum time-energy entanglement to enhance the overall yield and selectivity of the process, when compared with a classical pump-probe setup, while maintaining femtosecond time resolution. We systematically study the effects of correlation strength on process efficiency and selectivity, comparing the results to classical pump-probe spectra. An excitation scheme to improve the yield based on spectral narrowing of biphotons is shown. The results indicate that the quantum improvements in yield are caused by a more efficient use of the total power available for the process. Y1 - 2019 U6 - https://doi.org/10.1103/PhysRevA.100.053844 SN - 2469-9926 SN - 2469-9934 VL - 100 IS - 5 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Berrah, N. A1 - Sánchez-González, Álvaro A1 - Jurek, Zoltan A1 - Obaid, Razib A1 - Xiong, H. A1 - Squibb, R. J. A1 - Osipov, T. A1 - Lutman, A. A1 - Fang, L. A1 - Barillot, T. A1 - Bozek, J. D. A1 - Cryan, J. A1 - Wolf, T. J. A. A1 - Rolles, Daniel A1 - Coffee, R. A1 - Schnorr, Kirsten A1 - Augustin, S. A1 - Fukuzawa, Hironobu A1 - Motomura, K. A1 - Niebuhr, Nina Isabelle A1 - Frasinski, L. J. A1 - Feifel, Raimund A1 - Schulz, Claus-Peter A1 - Toyota, Kenji A1 - Son, Sang-Kil A1 - Ueda, K. A1 - Pfeifer, T. A1 - Marangos, J. P. A1 - Santra, Robin T1 - Femtosecond-resolved observation of the fragmentation of buckminsterfullerene following X-ray multiphoton ionization JF - Nature physics N2 - X-ray free-electron lasers have, over the past decade, opened up the possibility of understanding the ultrafast response of matter to intense X-ray pulses. In earlier research on atoms and small molecules, new aspects of this response were uncovered, such as rapid sequences of inner-shell photoionization and Auger ionization. Here, we studied a larger molecule, buckminsterfullerene (C-60), exposed to 640 eV X-rays, and examined the role of chemical effects, such as chemical bonds and charge transfer, on the fragmentation following multiple ionization of the molecule. To provide time resolution, we performed femtosecond-resolved X-ray pump/X-ray probe measurements, which were accompanied by advanced simulations. The simulations and experiment reveal that despite substantial ionization induced by the ultrashort (20 fs) X-ray pump pulse, the fragmentation of C-60 is considerably delayed. This work uncovers the persistence of the molecular structure of C-60, which hinders fragmentation over a timescale of hundreds of femtoseconds. Furthermore, we demonstrate that a substantial fraction of the ejected fragments are neutral carbon atoms. These findings provide insights into X-ray free-electron laser-induced radiation damage in large molecules, including biomolecules. Y1 - 2019 U6 - https://doi.org/10.1038/s41567-019-0665-7 SN - 1745-2473 SN - 1745-2481 VL - 15 IS - 12 SP - 1279 EP - 1301 PB - Nature Publ. Group CY - London ER -