The Experts below are selected from a list of 156723 Experts worldwide ranked by ideXlab platform
A P Jones - One of the best experts on this subject based on the ideXlab platform.
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destruction of interstellar dust in evolving supernova remnant shock waves
The Astrophysical Journal, 2015Co-Authors: Jonathan D Slavin, Eli Dwek, A P JonesAbstract:Supernova generated shock waves are responsible for most of the destruction of dust grains in the interstellar medium (ISM). Calculations of the dust destruction timescale have so far been carried out using plane parallel steady shocks, however that approximation breaks down when the destruction timescale becomes longer than that for the evolution of the supernova remnant (SNR) shock. In this paper we present new calculations of grain destruction in evolving, radiative SNRs. To facilitate comparison with the previous study by Jones et al. (1996), we adopt the same dust properties as in that paper. We find that the efficiencies of grain destruction are most divergent from those for a steady shock when the thermal history of a shocked gas parcel in the SNR differs significantly from that behind a steady shock. This occurs in shocks with velocities 200 km s(exp -1) for which the remnant is just beginning to go radiative. Assuming SNRs evolve in a warm phase dominated ISM, we find dust destruction Timescales are increased by a factor of approximately 2 compared to those of Jones et al. (1996), who assumed a hot gas dominated ISM. Recent estimates of supernova rates and ISM mass lead to another factor of approximately 3 increase in the destruction Timescales, resulting in a silicate grain destruction timescale of approximately 2-3 Gyr. These increases, while not able resolve the problem of the discrepant Timescales for silicate grain destruction and creation, are an important step towards understanding the origin, and evolution of dust in the ISM.
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destruction of interstellar dust in evolving supernova remnant shock waves
arXiv: Astrophysics of Galaxies, 2015Co-Authors: Jonathan D Slavin, Eli Dwek, A P JonesAbstract:Supernova generated shock waves are responsible for most of the destruction of dust grains in the interstellar medium (ISM). Calculations of the dust destruction timescale have so far been carried out using plane parallel steady shocks, however that approximation breaks down when the destruction timescale becomes longer than that for the evolution of the supernova remnant (SNR) shock. In this paper we present new calculations of grain destruction in evolving, radiative SNRs. To facilitate comparison with the previous study by Jones et al. (1996), we adopt the same dust properties as in that paper. We find that the efficiencies of grain destruction are most divergent from those for a steady shock when the thermal history of a shocked gas parcel in the SNR differs significantly from that behind a steady shock. This occurs in shocks with velocities >~ 200 km/s for which the remnant is just beginning to go radiative. Assuming SNRs evolve in a warm phase dominated ISM, we find dust destruction Timescales are increased by a factor of ~2 compared to those of Jones et al. (1996), who assumed a hot gas dominated ISM. Recent estimates of supernova rates and ISM mass lead to another factor of ~3 increase in the destruction Timescales, resulting in a silicate grain destruction timescale of ~2-3 Gyr. These increases, while not able resolve the problem of the discrepant Timescales for silicate grain destruction and creation, are an important step towards understanding the origin, and evolution of dust in the ISM.
David E Shaw - One of the best experts on this subject based on the ideXlab platform.
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long timescale molecular dynamics simulations of protein structure and function
Current Opinion in Structural Biology, 2009Co-Authors: John L Klepeis, Kresten Lindorfflarsen, Ron O Dror, David E ShawAbstract:Molecular dynamics simulations allow for atomic-level characterization of biomolecular processes such as the conformational transitions associated with protein function. The computational demands of such simulations, however, have historically prevented them from reaching the microsecond and greater Timescales on which these events often occur. Recent advances in algorithms, software, and computer hardware have made microsecond-timescale simulations with tens of thousands of atoms practical, with millisecond-timescale simulations on the horizon. This review outlines these advances in high-performance molecular dynamics simulation and discusses recent applications to studies of protein dynamics and function as well as experimental validation of the underlying computational models.
Jonathan D Slavin - One of the best experts on this subject based on the ideXlab platform.
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destruction of interstellar dust in evolving supernova remnant shock waves
The Astrophysical Journal, 2015Co-Authors: Jonathan D Slavin, Eli Dwek, A P JonesAbstract:Supernova generated shock waves are responsible for most of the destruction of dust grains in the interstellar medium (ISM). Calculations of the dust destruction timescale have so far been carried out using plane parallel steady shocks, however that approximation breaks down when the destruction timescale becomes longer than that for the evolution of the supernova remnant (SNR) shock. In this paper we present new calculations of grain destruction in evolving, radiative SNRs. To facilitate comparison with the previous study by Jones et al. (1996), we adopt the same dust properties as in that paper. We find that the efficiencies of grain destruction are most divergent from those for a steady shock when the thermal history of a shocked gas parcel in the SNR differs significantly from that behind a steady shock. This occurs in shocks with velocities 200 km s(exp -1) for which the remnant is just beginning to go radiative. Assuming SNRs evolve in a warm phase dominated ISM, we find dust destruction Timescales are increased by a factor of approximately 2 compared to those of Jones et al. (1996), who assumed a hot gas dominated ISM. Recent estimates of supernova rates and ISM mass lead to another factor of approximately 3 increase in the destruction Timescales, resulting in a silicate grain destruction timescale of approximately 2-3 Gyr. These increases, while not able resolve the problem of the discrepant Timescales for silicate grain destruction and creation, are an important step towards understanding the origin, and evolution of dust in the ISM.
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destruction of interstellar dust in evolving supernova remnant shock waves
arXiv: Astrophysics of Galaxies, 2015Co-Authors: Jonathan D Slavin, Eli Dwek, A P JonesAbstract:Supernova generated shock waves are responsible for most of the destruction of dust grains in the interstellar medium (ISM). Calculations of the dust destruction timescale have so far been carried out using plane parallel steady shocks, however that approximation breaks down when the destruction timescale becomes longer than that for the evolution of the supernova remnant (SNR) shock. In this paper we present new calculations of grain destruction in evolving, radiative SNRs. To facilitate comparison with the previous study by Jones et al. (1996), we adopt the same dust properties as in that paper. We find that the efficiencies of grain destruction are most divergent from those for a steady shock when the thermal history of a shocked gas parcel in the SNR differs significantly from that behind a steady shock. This occurs in shocks with velocities >~ 200 km/s for which the remnant is just beginning to go radiative. Assuming SNRs evolve in a warm phase dominated ISM, we find dust destruction Timescales are increased by a factor of ~2 compared to those of Jones et al. (1996), who assumed a hot gas dominated ISM. Recent estimates of supernova rates and ISM mass lead to another factor of ~3 increase in the destruction Timescales, resulting in a silicate grain destruction timescale of ~2-3 Gyr. These increases, while not able resolve the problem of the discrepant Timescales for silicate grain destruction and creation, are an important step towards understanding the origin, and evolution of dust in the ISM.
Chunyan Jiang - One of the best experts on this subject based on the ideXlab platform.
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a fitting formula for the merger timescale of galaxies in hierarchical clustering
The Astrophysical Journal, 2008Co-Authors: Chunyan Jiang, Yipeng Jing, A Faltenbacher, Weipeng LinAbstract:We study galaxy mergers using a high-resolution cosmological hydro/N-body simulation with star formation and compare the measured merger Timescales with theoretical predictions based on the Chandrasekhar formula. In contrast to Navarro et al., our numerical results indicate that the commonly used equation for the merger timescale given by Lacey and Cole systematically underestimates the merger Timescales for minor mergers and overestimates those for major mergers. This behavior is partly explained by the poor performance of their expression for the Coulomb logarithm, ln (mpri/msat) . The two alternative forms ln (1 + mpri/msat) and ½ln[1 + (mpri/msat)2] for the Coulomb logarithm can account for the mass dependence of merger timescale successfully, but both of them underestimate the merger timescale by a factor 2. Since ln (1 + mpri/msat) represents the mass dependence slightly better, we adopt this expression for the Coulomb logarithm. Furthermore, we find that the dependence of the merger timescale on the circularity parameter is much weaker than the widely adopted power law 0.78, whereas 0.940.60 + 0.60 provides a good match to the data. Based on these findings, we present an accurate and convenient fitting formula for the merger timescale of galaxies in cold dark matter models.
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a fitting formula for the merger timescale of galaxies in hierarchical clustering
arXiv: Astrophysics, 2007Co-Authors: Chunyan Jiang, Yipeng Jing, A Faltenbacher, Weipeng LinAbstract:We study galaxy mergers using a high-resolution cosmological hydro/N-body simulation with star formation, and compare the measured merger Timescales with theoretical predictions based on the Chandrasekhar formula. In contrast to Navarro et al., our numerical results indicate, that the commonly used equation for the merger timescale given by Lacey and Cole, systematically underestimates the merger Timescales for minor mergers and overestimates those for major mergers. This behavior is partly explained by the poor performance of their expression for the Coulomb logarithm, \ln (m_pri/m_sat). The two alternative forms \ln (1+m_pri/m_sat) and 1/2\ln [1+(m_pri/m_sat)^2] for the Coulomb logarithm can account for the mass dependence of merger timescale successfully, but both of them underestimate the merger time scale by a factor 2. Since \ln (1+m_pri/m_sat) represents the mass dependence slightly better we adopt this expression for the Coulomb logarithm. Furthermore, we find that the dependence of the merger timescale on the circularity parameter \epsilon is much weaker than the widely adopted power-law \epsilon^{0.78}, whereas 0.94*{\epsilon}^{0.60}+0.60 provides a good match to the data. Based on these findings, we present an accurate and convenient fitting formula for the merger timescale of galaxies in cold dark matter models.
Matthias R Hohmann - One of the best experts on this subject based on the ideXlab platform.
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are intrinsic neural Timescales related to sensory processing evidence from abnormal behavioral states
NeuroImage, 2021Co-Authors: Federico Zilio, Javier Gomezpilar, Shumei Cao, Jun Zhang, Di Zang, Jiaxing Tan, Tanigawa Hiromi, Stuart Fogel, Zirui Huang, Matthias R HohmannAbstract:Abstract The brain exhibits a complex temporal structure which translates into a hierarchy of distinct neural Timescales. An open question is how these intrinsic Timescales are related to sensory or motor information processing and whether these dynamics have common patterns in different behavioural states. We address these questions by investigating the brain's intrinsic Timescales in healthy controls, motor (amyotrophic lateral sclerosis, locked-in syndrome), sensory (anaesthesia, unresponsive wakefulness syndrome), and progressive reduction of sensory processing (from awake states over N1, N2, N3). We employed a combination of measures from EEG resting-state data: auto-correlation window (ACW), power spectral density (PSD), and power-law exponent (PLE). Prolonged neural Timescales accompanied by a shift towards slower frequencies were observed in the conditions with sensory deficits, but not in conditions with motor deficits. Our results establish that the spontaneous activity's intrinsic neural timescale is related to the neural capacity that specifically supports sensory rather than motor information processing in the healthy brain.
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intrinsic neural Timescales related to sensory processing evidence from abnormal behavioural states
bioRxiv, 2020Co-Authors: Federico Zilio, Javier Gomezpilar, Shumei Cao, Jun Zhang, Di Zang, Jiaxing Tan, Tanigawa Hiromi, Stuart Fogel, Zirui Huang, Matthias R HohmannAbstract:The brain exhibits a complex temporal structure which translates into a hierarchy of distinct neural Timescales. An open question is how these intrinsic Timescales are related to sensory or motor information processing and whether these dynamics have common patterns in different behavioural states. We address these questions by investigating the brains intrinsic Timescales in healthy controls, motor (amyotrophic lateral sclerosis, locked-in syndrome), sensory (anaesthesia, unresponsive wakefulness syndrome), and progressive reduction of sensory processing (from awake states over N1, N2, N3). We employed a combination of measures from EEG resting-state data: auto-correlation window (ACW), power spectral density (PSD), and power-law exponent (PLE). Prolonged neural Timescales accompanied by a shift towards slower frequencies were observed in the conditions with sensory deficits, but not in conditions with motor deficits. Our results establish that the spontaneous activitys intrinsic neural timescale is related to specifically sensory rather than motor information processing in the healthy brain. HighlightsO_LIEEG resting-state shows a hierarchy of intrinsic neural Timescales. C_LIO_LISensory deficits as in disorders of consciousness lead to prolonged intrinsic neuralTimescales. C_LIO_LIClinical conditions with motor deficits do not show changes in intrinsic neural Timescales.20 C_LI Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=156 SRC="FIGDIR/small/229161v1_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@9a393corg.highwire.dtl.DTLVardef@123a1d6org.highwire.dtl.DTLVardef@55f892org.highwire.dtl.DTLVardef@32689a_HPS_FORMAT_FIGEXP M_FIG C_FIG
