TY - JOUR A1 - Seiß, Martin A1 - Albers, Nicole A1 - Sremčević, Miodrag A1 - Schmidt, Jürgen A1 - Salo, Heikki A1 - Seiler, Michael A1 - Hoffmann, Holger A1 - Spahn, Frank T1 - Hydrodynamic Simulations of Moonlet-induced Propellers in Saturn's Rings BT - Application to Bleriot JF - The astronomical journal N2 - One of the biggest successes of the Cassini mission is the detection of small moons (moonlets) embedded in Saturns rings that cause S-shaped density structures in their close vicinity, called propellers. Here, we present isothermal hydrodynamic simulations of moonlet-induced propellers in Saturn's A ring that denote a further development of the original model. We find excellent agreement between these new hydrodynamic and corresponding N-body simulations. Furthermore, the hydrodynamic simulations confirm the predicted scaling laws and the analytical solution for the density in the propeller gaps. Finally, this mean field approach allows us to simulate the pattern of the giant propeller Blériot, which is too large to be modeled by direct N-body simulations. Our results are compared to two stellar occultation observations by the Cassini Ultraviolet Imaging Spectrometer (UVIS), which intersect the propeller Blériot. Best fits to the UVIS optical depth profiles are achieved for a Hill radius of 590 m, which implies a moonlet diameter of about 860 m. Furthermore, the model favors a kinematic shear viscosity of the surrounding ring material of ν0 = 340 cm2 s−1, a dispersion velocity in the range of 0.3 cm s−1 < c0 < 1.5 cm s−1, and a fairly high bulk viscosity 7 < ξ0/ν0 < 17. These large transport values might be overestimated by our isothermal ring model and should be reviewed by an extended model including thermal fluctuations. KW - diffusion KW - hydrodynamics KW - planets and satellites: rings Y1 - 2018 U6 - https://doi.org/10.3847/1538-3881/aaed44 SN - 0004-6256 SN - 1538-3881 VL - 157 IS - 1 PB - IOP Publishing Ltd. CY - Bristol ER - TY - JOUR A1 - Schmälzlin, Elmar Gerd A1 - Moralejo, Benito A1 - Gersonde, Ingo A1 - Schleusener, Johannes A1 - Darvin, Maxim E. A1 - Thiede, Gisela A1 - Roth, Martin M. T1 - Nonscanning large-area Raman imaging for ex vivo/in vivo skin cancer discrimination JF - Journal of biomedical optics N2 - Imaging Raman spectroscopy can be used to identify cancerous tissue. Traditionally, a step-by-step scanning of the sample is applied to generate a Raman image, which, however, is too slow for routine examination of patients. By transferring the technique of integral field spectroscopy (IFS) from astronomy to Raman imaging, it becomes possible to record entire Raman images quickly within a single exposure, without the need for a tedious scanning procedure. An IFS-based Raman imaging setup is presented, which is capable of measuring skin ex vivo or in vivo. It is demonstrated how Raman images of healthy and cancerous skin biopsies were recorded and analyzed. (C) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. KW - Raman spectroscopy KW - cancer diagnosis KW - Raman imaging KW - multichannel KW - astronomy KW - epidermis KW - dermis Y1 - 2018 U6 - https://doi.org/10.1117/1.JBO.23.10.105001 SN - 1083-3668 SN - 1560-2281 VL - 23 IS - 10 PB - SPIE CY - Bellingham ER - TY - JOUR A1 - Mann, Michael E. A1 - Rahmstorf, Stefan A1 - Kornhuber, Kai A1 - Steinman, Byron A. A1 - Miller, Sonya K. A1 - Petri, Stefan A1 - Coumou, Dim T1 - Projected changes in persistent extreme summer weather events BT - The role of quasi-resonant amplification JF - Science Advances N2 - Persistent episodes of extreme weather in the Northern Hemisphere summer have been associated with high-amplitude quasi-stationary atmospheric Rossby waves, with zonal wave numbers 6 to 8 resulting from the phenomenon of quasi-resonant amplification (QRA). A fingerprint for the occurrence of QRA can be defined in terms of the zonally averaged surface temperature field. Examining state-of-the-art [Coupled Model Intercomparison Project Phase 5 (CMIP5)] climate model projections, we find that QRA events are likely to increase by similar to 50% this century under business-as-usual carbon emissions, but there is considerable variation among climate models. Some predict a near tripling of QRA events by the end of the century, while others predict a potential decrease. Models with amplified Arctic warming yield the most pronounced increase in QRA events. The projections are strongly dependent on assumptions regarding the nature of changes in radiative forcing associated with anthropogenic aerosols over the next century. One implication of our findings is that a reduction in midlatitude aerosol loading could actually lead to Arctic de-amplification this century, ameliorating potential increases in persistent extreme weather events. Y1 - 2018 U6 - https://doi.org/10.1126/sciadv.aat3272 SN - 2375-2548 VL - 4 IS - 10 PB - American Assoc. for the Advancement of Science CY - Washington ER - TY - JOUR A1 - Richter, Philipp A1 - Fox, Andrew J. A1 - Wakker, Bart P. A1 - Howk, J. Christopher A1 - Lehner, Nicolas A1 - Barger, Kathleen A. A1 - Lockman, Felix J. T1 - New constraints on the nature and origin of the leading arm of the magellanic stream JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - We present a new precision measurement of gas-phase abundances of S, O, N, Si, Fe, P, Al, Ca as well as molecular hydrogen (H-2) in the Leading Arm (region II, LA II) of the Magellanic Stream (MS) toward the Seyfert galaxy NGC 3783. The results are based on high-quality archival ultraviolet/optical/radio data from various different instruments (HST/STIS, FUSE, AAT, GBT, GB140 ft, ATCA). Our study updates previous results from lower-resolution data and provides for the first time a self-consistent component model of the complex multiphase absorber, delivering important constraints on the nature and origin of LA II. We derive a uniform, moderate a abundance in the two main absorber groups at +245 and +190 km s(-1) of alpha/H = 0.30 +/- 0.05 solar, a low nitrogen abundance of N/H = 0.05 +/- 0.01 solar, and a high dust content with substantial dust depletion values for Si, Fe, Al, and Ca. These a, N, and dust abundances in LA II are similar to those observed in the Small Magellanic Cloud (SMC). From the analysis of the H2 absorption, we determine a high thermal pressure of P/k approximate to 1680 K cm(-3) in LA II, in line with the idea that LA II is located in the inner Milky Way halo at a z-height of < 20 kpc, where it hydrodynamically interacts with the ambient hot coronal gas. Our study supports a scenario in which LA II stems from the breakup of a metal- and dust-enriched progenitor cloud that was recently (200-500 Myr ago) stripped from the SMC. KW - Galaxy: evolution KW - Galaxy: halo KW - ISM: abundances KW - Magellanic Clouds KW - quasars: absorption lines Y1 - 2018 U6 - https://doi.org/10.3847/1538-4357/aadd0f SN - 0004-637X SN - 1538-4357 VL - 865 IS - 2 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Gonzalez Manrique, Sergio Javier A1 - Kuckein, Christoph A1 - Collados, M. A1 - Denker, Carsten A1 - Solanki, S. K. A1 - Gomory, P. A1 - Verma, Meetu A1 - Balthasar, H. A1 - Lagg, A. A1 - Diercke, Andrea T1 - Temporal evolution of arch filaments as seen in He I 10 830 angstrom JF - Astronomy and astrophysics : an international weekly journal N2 - Aims. We study the evolution of an arch filament system (AFS) and of its individual arch filaments to learn about the processes occurring in them. Methods. We observed the AFS at the GREGOR solar telescope on Tenerife at high cadence with the very fast spectroscopic mode of the GREGOR Infrared Spectrograph (GRIS) in the He I 10 830 angstrom spectral range. The He I triplet profiles were fitted with analytic functions to infer line-of-sight (LOS) velocities to follow plasma motions within the AFS. Results. We tracked the temporal evolution of an individual arch filament over its entire lifetime, as seen in the He I 10 830 angstrom triplet. The arch filament expanded in height and extended in length from 13 ' to 21 '. The lifetime of this arch filament is about 30 min. About 11 min after the arch filament is seen in He I, the loop top starts to rise with an average Doppler velocity of 6 km s(-1). Only two minutes later, plasma drains down with supersonic velocities towards the footpoints reaching a peak velocity of up to 40 km s(-1) in the chromosphere. The temporal evolution of He I 10 830 angstrom profiles near the leading pore showed almost ubiquitous dual red components of the He I triplet, indicating strong downflows, along with material nearly at rest within the same resolution element during the whole observing time. KW - Sun: chromosphere KW - Sun: activity KW - methods: observational KW - methods: data analysis KW - techniques: high angular resolution Y1 - 2018 U6 - https://doi.org/10.1051/0004-6361/201832684 SN - 1432-0746 VL - 617 PB - EDP Sciences CY - Les Ulis ER - 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 - Lewandowsky, Stephan A1 - Cowtan, Kevin A1 - Risbey, James S. A1 - Mann, Michael E. A1 - Steinman, Byron A. A1 - Oreskes, Naomi A1 - Rahmstorf, Stefan T1 - The 'pause' in global warming in historical context BT - (II). comparing models to observations JF - Environmental research letters N2 - We review the evidence for a putative early 21st-century divergence between global mean surface temperature (GMST) and Coupled Model Intercomparison Project Phase 5 (CMIP5) projections. We provide a systematic comparison between temperatures and projections using historical versions of GMST products and historical versions of model projections that existed at the times when claims about a divergence were made. The comparisons are conducted with a variety of statistical techniques that correct for problems in previous work, including using continuous trends and a Monte Carlo approach to simulate internal variability. The results show that there is no robust statistical evidence for a divergence between models and observations. The impression of a divergence early in the 21st century was caused by various biases in model interpretation and in the observations, and was unsupported by robust statistics. Y1 - 2018 U6 - https://doi.org/10.1088/1748-9326/aaf372 SN - 1748-9326 VL - 13 IS - 12 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 -