778 research outputs found
Spectral Properties of Compressible Magnetohydrodynamic Turbulence from Numerical Simulations
We analyze the spectral properties of driven, supersonic compressible
magnetohydrodynamic (MHD) turbulence obtained via high-resolution numerical
experiments, for application to understanding the dynamics of giant molecular
clouds. Via angle-averaged power spectra, we characterize the transfer of
energy from the intermediate, driving scales down to smaller dissipative
scales, and also present evidence for inverse cascades that achieve
modal-equipartition levels on larger spatial scales. Investigating compressive
versus shear modes separately, we evaluate their relative total power, and find
that as the magnetic field strength decreases, (1) the shear fraction of the
total kinetic power decreases, and (2) slopes of power-law fits over the
inertial range steepen. To relate to previous work on incompressible MHD
turbulence, we present qualitative and quantitative measures of the
scale-dependent spectral anisotropy arising from the shear-Alfv\'{e}n cascade,
and show how these vary with changing mean magnetic field strength. Finally, we
propose a method for using anisotropy in velocity centroid maps as a diagnostic
of the mean magnetic field strength in observed cloud cores.Comment: 22 pages, 11 figures; Ap.J., accepte
Interpreting the multi-biomarker disease activity score in the context of tocilizumab treatment for patients with rheumatoid arthritis
CHD4 slides nucleosomes by decoupling entry- and exit-side DNA translocation
© 2020, The Author(s). Chromatin remodellers hydrolyse ATP to move nucleosomal DNA against histone octamers. The mechanism, however, is only partially resolved, and it is unclear if it is conserved among the four remodeller families. Here we use single-molecule assays to examine the mechanism of action of CHD4, which is part of the least well understood family. We demonstrate that the binding energy for CHD4-nucleosome complex formation—even in the absence of nucleotide—triggers significant conformational changes in DNA at the entry side, effectively priming the system for remodelling. During remodelling, flanking DNA enters the nucleosome in a continuous, gradual manner but exits in concerted 4–6 base-pair steps. This decoupling of entry- and exit-side translocation suggests that ATP-driven movement of entry-side DNA builds up strain inside the nucleosome that is subsequently released at the exit side by DNA expulsion. Based on our work and previous studies, we propose a mechanism for nucleosome sliding
An investigation into the prevalence of sleep disturbances in primary Sjögren’s syndrome: a systematic review of the literature
Objectives. To identify whether sleep disturbances are more prevalent in primary SS (pSS) patients compared with the general population and to recognize which specific sleep symptoms are particularly problematic in this population. Methods. Electronic searches of the literature were conducted in PubMed, Medline (Ovid), Embase (Ovid), PsychINFO (Ovid) and Web of Science and the search strategy registered a priori. Titles and abstracts were reviewed by two authors independently against a set of prespecified inclusion/exclusion criteria, reference lists were examined and a narrative synthesis of the included articles was conducted. Results. Eight whole-text papers containing nine separate studies met the inclusion criteria and were included in the narrative analysis. Few of these studies met all of the quality assessment criteria. The studies used a range of self-reported measures and objective measures, including polysomnography. Mixed evidence was obtained for some of the individual sleep outcomes, but overall compared with controls, pSS patients reported greater subjective sleep disturbances and daytime somnolence and demonstrated more night awakenings and pre-existing obstructive sleep apnoea. Conclusions. A range of sleep disturbances are commonly reported in pSS patients. Further polysomnography studies are recommended to confirm the increased prevalence of night awakenings and obstructive sleep apnoea in this patient group. pSS patients with excessive daytime somnolence should be screened for co-morbid sleep disorders and treated appropriately. Interventions targeted at sleep difficulties in pSS, such as cognitive behavioural therapy for insomnia and nocturnal humidification devices, have the potential to improve quality of life in this patient group and warrant further investigation
TCT-251 ECG Findings in ST-Elevation Myocardial Infarction from Culprit Left Main Coronary Artery Disease: A Multicenter Registry Study
Ubiquitous outflows in DEEP2 spectra of star-forming galaxies at z=1.4
Galactic winds are a prime suspect for the metal enrichment of the
intergalactic medium and may have a strong influence on the chemical evolution
of galaxies and the nature of QSO absorption line systems. We use a sample of
1406 galaxy spectra at z~1.4 from the DEEP2 redshift survey to show that
blueshifted Mg II 2796, 2803 A absorption is ubiquitous in starforming galaxies
at this epoch. This is the first detection of frequent outflowing galactic
winds at z~1. The presence and depth of absorption are independent of AGN
spectral signatures or galaxy morphology; major mergers are not a prerequisite
for driving a galactic wind from massive galaxies. Outflows are found in
coadded spectra of galaxies spanning a range of 30x in stellar mass and 10x in
star formation rate (SFR), calibrated from K-band and from MIPS IR fluxes. The
outflows have column densities of order N_H ~ 10^20 cm^-2 and characteristic
velocities of ~ 300-500 km/sec, with absorption seen out to 1000 km/sec in the
most massive, highest SFR galaxies. The velocities suggest that the outflowing
gas can escape into the IGM and that massive galaxies can produce
cosmologically and chemically significant outflows. Both the Mg II equivalent
width and the outflow velocity are larger for galaxies of higher stellar mass
and SFR, with V_wind ~ SFR^0.3, similar to the scaling in low redshift
IR-luminous galaxies. The high frequency of outflows in the star-forming galaxy
population at z~1 indicates that galactic winds occur in the progenitors of
massive spirals as well as those of ellipticals. The increase of outflow
velocity with mass and SFR constrains theoretical models of galaxy evolution
that include feedback from galactic winds, and may favor momentum-driven models
for the wind physics.Comment: Accepted by ApJ. 25 pages, 17 figures. Revised to add discussions of
intervening absorbers and AGN-driven outflows; conclusions unchange
Development of a modified head and neck quality assurance phantom for use in stereotactic radiosurgery trials
Optimising intraperitoneal gentamicin dosing in peritoneal dialysis patients with peritonitis (GIPD) study
Background: Antibiotics are preferentially delivered via the peritoneal route to treat peritonitis, a major complication of peritoneal dialysis (PD), so that maximal concentrations are delivered at the site of infection. However, drugs administered intraperitoneally can be absorbed into the systemic circulation. Drugs excreted by the kidneys accumulate in PD patients, increasing the risk of toxicity. The aim of this study is to examine a model of gentamicin pharmacokinetics and to develop an intraperitoneal drug dosing regime that maximises bacterial killing and minimises toxicity
Early identification of DPAM in at-risk low-grade appendiceal mucinous neoplasm patients: a new approach to surveillance for peritoneal metastasis
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