58 research outputs found
New Insights into White-Light Flare Emission from Radiative-Hydrodynamic Modeling of a Chromospheric Condensation
(abridged) The heating mechanism at high densities during M dwarf flares is
poorly understood. Spectra of M dwarf flares in the optical and
near-ultraviolet wavelength regimes have revealed three continuum components
during the impulsive phase: 1) an energetically dominant blackbody component
with a color temperature of T 10,000 K in the blue-optical, 2) a smaller
amount of Balmer continuum emission in the near-ultraviolet at lambda 3646
Angstroms and 3) an apparent pseudo-continuum of blended high-order Balmer
lines. These properties are not reproduced by models that employ a typical
"solar-type" flare heating level in nonthermal electrons, and therefore our
understanding of these spectra is limited to a phenomenological interpretation.
We present a new 1D radiative-hydrodynamic model of an M dwarf flare from
precipitating nonthermal electrons with a large energy flux of erg
cm s. The simulation produces bright continuum emission from a
dense, hot chromospheric condensation. For the first time, the observed color
temperature and Balmer jump ratio are produced self-consistently in a
radiative-hydrodynamic flare model. We find that a T 10,000 K
blackbody-like continuum component and a small Balmer jump ratio result from
optically thick Balmer and Paschen recombination radiation, and thus the
properties of the flux spectrum are caused by blue light escaping over a larger
physical depth range compared to red and near-ultraviolet light. To model the
near-ultraviolet pseudo-continuum previously attributed to overlapping Balmer
lines, we include the extra Balmer continuum opacity from Landau-Zener
transitions that result from merged, high order energy levels of hydrogen in a
dense, partially ionized atmosphere. This reveals a new diagnostic of ambient
charge density in the densest regions of the atmosphere that are heated during
dMe and solar flares.Comment: 50 pages, 2 tables, 13 figures. Accepted for publication in the Solar
Physics Topical Issue, "Solar and Stellar Flares". Version 2 (June 22, 2015):
updated to include comments by Guest Editor. The final publication is
available at Springer via http://dx.doi.org/10.1007/s11207-015-0708-
Association between NICE guidance on biologic therapies with rates of hip and knee replacement among rheumatoid arthritis patients in England and Wales:An interrupted time-series analysis.
Objective: To estimate the impact of NICE approval of tumour necrosis factor inhibitor (TNFi) therapies on the incidence of total hip replacement (THR) and total knee replacement (TKR) among rheumatoid arthritis (RA) patients in England and Wales.Methods: Primary care data (Clinical Practice Research Datalink (CPRD)) for the study period (1995-2014) were used to identify incident adult RA patients. The age and sex-standardised 5-year incidence of THR and TKR was calculated separately for RA patients diagnosed in each six-months between 1995-2009. We took a natural experimental approach, using segmented linear regression to estimate changes in level and trend following the publication of NICE TA 36 in March 2002, incorporating a 1-year lag. Regression coefficients were used to calculate average change in rates, adjusted for prior level and trend.Results: We identified 17,505 incident RA patients of whom 465 and 650 underwent THR and TKR surgery, respectively. The modeled average incidence of THR and TKR over the biologic-era was 6.57/1,000 person years (PYs) and 8.51/1,000 PYs, respectively, with projected (had pre-NICE TA 36 level and trend continued uninterrupted) figures of 5.63/1,000 PYs and 12.92 PYs, respectively. NICE guidance was associated with a significant average decrease in TKR incidence of -4.41/1,000 PYs (95% C.I. -6.88 to -1.94), equating to a relative 34% reduction. Overall, no effect was seen on THR rates.Conclusions: Among incident RA patients in England and Wales, NICE guidance on TNFi therapies for RA management was temporally associated with reduced rates of TKR but not THR</p
Current Status of Simulations
As the title suggests, the purpose of this chapter is to review the current
status of numerical simulations of black hole accretion disks. This chapter
focuses exclusively on global simulations of the accretion process within a few
tens of gravitational radii of the black hole. Most of the simulations
discussed are performed using general relativistic magnetohydrodynamic (MHD)
schemes, although some mention is made of Newtonian radiation MHD simulations
and smoothed particle hydrodynamics. The goal is to convey some of the exciting
work that has been going on in the past few years and provide some speculation
on future directions.Comment: 15 pages, 14 figures, to appear in the proceedings of the ISSI-Bern
workshop on "The Physics of Accretion onto Black Holes" (8-12 October 2012
Evaluating outcomes of therapies offered by occupational therapists in adult mental health
Background:
Attitudes towards the use of outcome measures by professionals working in mental health have been shown to be variable. Occupational therapists appear to have difficulty specifying goals and measuring the outcomes of interventions.
Aims:
To measure the outcomes of therapies offered by occupational therapists and to assess concurrent validity of the Van du Toit Model of Creative Ability (VdT MoCA) assessment.
Method:
The Global Assessment of Functioning (GAF), VdT MoCA assessment and Canadian Occupational Performance Measure (COPM) were used. Changes in mean scores on the measures were assessed using appropriate tests. Correlations between measures were assessed using Spearman's non-parametric test.
Results:
Mean post-therapy scores were significantly higher than pre-therapy scores on all three measures. VdT MoCA assessment scores pre- and post-therapy were highly correlated with GAF scores. The COPM outcome scores were uncorrelated with VdT MoCA assessment and GAF scores.
Conclusions:
The results offer a promising indication that occupational therapy interventions may increase functioning and thus aid clients' recovery. The VdT MoCA assessment is promising as a measure of improvement in functioning. Further research is needed to confirm these results and to further explore issues around occupational therapists' use of outcome measures
Study Protocol for Better Evidence for Selecting Transplant Fluids (BEST-Fluids): a pragmatic, registry-based, multi-center, double-blind, randomized controlled trial evaluating the effect of intravenous fluid therapy with Plasma-Lyte 148 versus 0.9% saline on delayed graft function in deceased donor kidney transplantation
BACKGROUND: Delayed graft function, the requirement for dialysis due to poor kidney function post-transplant, is a frequent complication of deceased donor kidney transplantation and is associated with inferior outcomes and higher costs. Intravenous fluids given during and after transplantation may affect the risk of poor kidney function after transplant. The most commonly used fluid, isotonic sodium chloride (0.9% saline), contains a high chloride concentration, which may be associated with acute kidney injury, and could increase the risk of delayed graft function. Whether using a balanced, low-chloride fluid instead of 0.9% saline is safe and improves kidney function after deceased donor kidney transplantation is unknown. METHODS: BEST-Fluids is an investigator-initiated, pragmatic, registry-based, multi-center, double-blind, randomized controlled trial. The primary objective is to compare the effect of intravenous Plasma-Lyte 148 (Plasmalyte), a balanced, low-chloride solution, with the effect of 0.9% saline on the incidence of delayed graft function in deceased donor kidney transplant recipients. From January 2018 onwards, 800 participants admitted for deceased donor kidney transplantation will be recruited over 3 years in Australia and New Zealand. Participants are randomized 1:1 to either intravenous Plasmalyte or 0.9% saline peri-operatively and until 48 h post-transplant, or until fluid is no longer required; whichever comes first. Follow up is for 1 year. The primary outcome is the incidence of delayed graft function, defined as dialysis in the first 7 days post-transplant. Secondary outcomes include early kidney transplant function (composite of dialysis duration and rate of improvement in graft function when dialysis is not required), hyperkalemia, mortality, graft survival, graft function, quality of life, healthcare resource use, and cost-effectiveness. Participants are enrolled, randomized, and followed up using the Australia and New Zealand Dialysis and Transplant (ANZDATA) Registry. DISCUSSION: If using Plasmalyte instead of 0.9% saline is effective at reducing delayed graft function and improves other clinical outcomes in deceased donor kidney transplantation, this simple, inexpensive change to using a balanced low-chloride intravenous fluid at the time of transplantation could be easily implemented in the vast majority of transplant settings worldwide. TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry: ACTRN12617000358347. Registered on 8 March 2017. ClinicalTrials.gov: NCT03829488. Registered on 4 February 2019.Michael G. Collins, Magid A. Fahim, Elaine M. Pascoe, Kathryn B. Dansie, Carmel M. Hawley, Philip A. Clayton, Kirsten Howard, David W. Johnson, Colin J. McArthur, Rachael C. McConnochie, Peter F. Mount, Donna Reidlinger, Laura Robison, Julie Varghese, Liza A. Vergara, Laurence Weinberg, Steven J. Chadban, and for the BEST-Fluids Investigators and the Australasian Kidney Trials Networ
Mendelian randomization supports bidirectional causality between telomere length and clonal hematopoiesis of indeterminate potential
Human genetic studies support an inverse causal relationship between leukocyte telomere length (LTL) and coronary artery disease (CAD), but directionally mixed effects for LTL and diverse malignancies. Clonal hematopoiesis of indeterminate potential (CHIP), characterized by expansion of hematopoietic cells bearing leukemogenic mutations, predisposes both hematologic malignancy and CAD. TERT (which encodes telomerase reverse transcriptase) is the most significantly associated germline locus for CHIP in genome-wide association studies. Here, we investigated the relationship between CHIP, LTL, and CAD in the Trans-Omics for Precision Medicine (TOPMed) program (n = 63,302) and UK Biobank (n = 47,080). Bidirectional Mendelian randomization studies were consistent with longer genetically imputed LTL increasing propensity to develop CHIP, but CHIP then, in turn, hastens to shorten measured LTL (mLTL). We also demonstrated evidence of modest mediation between CHIP and CAD by mLTL. Our data promote an understanding of potential causal relationships across CHIP and LTL toward prevention of CAD
Preliminary O and H isotope data for groundwater from the Hueco Bolson (El Paso, Texas; Ciudad Juárez, Chihuahua): constraints on water sources
Groundwater from municipal and monitoring wells gives δO and δH values plotting in several fields that distinguish water sources as follows. Values are presented below as (δO\permil,δH \permil). Present-day Rio Grande water (-6 to-7, -62 to -66) is strongly affected by evaporation in New Mexico reservoirs. Groundwater from post-bomb infiltration in the river bed is similar. Groundwater from Texas includes non-evaporated water (-9, -63) associated with the flanks of the 1500 m Franklin Mts., and (-10 to -11, -70 to -78) probably derived from the 2500-3500 m San Andres and Sacramento Mts. in New Mexico. Groundwater with strong evaporation signatures (-5.5 to -9, -41 to -64) occurs east of El Paso, and may represent mixtures of river- and mountain-derived water, or evaporated surface water from lower basin elevations. Groundwater from Ciudad Juárez, (-11 to -12, -80 to -90), did not originate as present-day Rio Grande surface water or groundwater from the Hueco Bolson in Texas. Two hypothetical sources are consistent with isotope data: 1. Pre-dam snow-melt from Colorado, supplied as Rio Grande water; 2 Late Quaternary lake water from pluvial Lake Palomas, supplied by underflow from the adjacent Bolson de los Muertos area of Chihuahua. Historical water level data indicate that significant recharge from the Rio Grande was unlikely before aquifer development
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