1,353 research outputs found
Preliminary EoS for core-collapse supernova simulations with the QMC model
In this work we present the preliminary results of a complete equation of
state (EoS) for core-collapse supernova simulations. We treat uniform matter
made of nucleons using the the quark-meson coupling (QMC) model. We show a
table with a variety of thermodynamic quantities, which covers the proton
fraction range with the linear grid spacing
( points) and the density range g.cm with
the logarithmic grid spacing g.cm
( points). This preliminary study is performed at zero temperature and our
results are compared with the widely used EoS already available in the
literature
Improved simulation of aerosol, cloud, and density measurements by shuttle lidar
Data retrievals are simulated for a Nd:YAG lidar suitable for early flight on the space shuttle. Maximum assumed vertical and horizontal resolutions are 0.1 and 100 km, respectively, in the boundary layer, increasing to 2 and 2000 km in the mesosphere. Aerosol and cloud retrievals are simulated using 1.06 and 0.53 microns wavelengths independently. Error sources include signal measurement, conventional density information, atmospheric transmission, and lidar calibration. By day, tenuous clouds and Saharan and boundary layer aerosols are retrieved at both wavelengths. By night, these constituents are retrieved, plus upper tropospheric, stratospheric, and mesospheric aerosols and noctilucent clouds. Density, temperature, and improved aerosol and cloud retrievals are simulated by combining signals at 0.35, 1.06, and 0.53 microns. Particlate contamination limits the technique to the cloud free upper troposphere and above. Error bars automatically show effect of this contamination, as well as errors in absolute density nonmalization, reference temperature or pressure, and the sources listed above. For nonvolcanic conditions, relative density profiles have rms errors of 0.54 to 2% in the upper troposphere and stratosphere. Temperature profiles have rms errors of 1.2 to 2.5 K and can define the tropopause to 0.5 km and higher wave structures to 1 or 2 km
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Lifetime Risk of Lower-Extremity Peripheral Artery Disease Defined by Ankle-Brachial Index in the United States.
Background There are no available lifetime risk estimates of lower-extremity peripheral artery disease (PAD). Methods and Results Using data from 6 US community-based cohorts and the vital statistics, we estimated the prevalence and incidence of PAD, defined as an ankle-brachial index < 0.90, at each year of age from birth to 80 years for white, black, and Hispanic men and women. Then, we used Markov Monte Carlo simulations in a simulated cohort of 100 000 individuals to estimate lifetime risk of PAD. On the basis of odds ratios of PAD for traditional atherosclerotic risk factors (eg, diabetes mellitus and smoking), we developed a calculator providing residual lifetime risk of PAD. In an 80-year horizon, lifetime risks of PAD were 30.0% in black men and 27.6% in black women, but ≈19% in white men and women and ≈22% in Hispanic men and women. From another perspective, 9% of blacks were estimated to develop PAD by 60 years of age, while the same proportion was seen at ≈70 years for whites and Hispanics. The residual lifetime risk within the same race/ethnicity varied by 3.5- to 5-fold according to risk factors (eg, residual lifetime risk in 45-year-old black men was 19.9% when current smoking, diabetes mellitus, and history of cardiovascular disease were absent versus 70.4% when all were present). Conclusions In the United States, ≈30% of blacks are estimated to develop PAD during their lifetime, whereas the corresponding estimate is ≈20% for whites and Hispanics. The residual lifetime risk within the same race/ethnicity substantially varies according to traditional risk factors
Observations of mesoscale and boundary-layer circulations affecting dust uplift and transport in the Saharan boundary layer
International audienceObservations of the Saharan boundary layer, made during the GERBILS field campaign, show that mesoscale land surface temperature variations (which were related to albedo variations) induced mesoscale circulations, and that mesoscale and boundary-layer circulations affected dust uplift and transport. These processes are unrepresented in many climate models, but may have significant impacts on the vertical transport and uplift of desert dust. Mesoscale effects in particular tend to be difficult to parameterise. With weak winds along the aircraft track, land surface temperature anomalies with scales of greater than 10 km are shown to significantly affect boundary-layer temperatures and winds. Such anomalies are expected to affect the vertical mixing of the dusty and weakly stratified Saharan Air Layer (SAL). Mesoscale variations in winds are also shown to affect dust loadings in the boundary-layer. In a region of local uplift, with strong along-track winds, boundary-layer rolls are shown to lead to warm moist dusty updraughts in the boundary layer. Large eddy model (LEM) simulations suggest that these rolls increased uplift by approximately 30%. The modelled effects of boundary-layer convection on uplift is shown to be larger when the boundary-layer wind is decreased, and most significant when the mean wind is below the threshold for dust uplift and the boundary-layer convection leads to uplift which would not otherwise occur
Simultaneous Red - Blue Lidar and Airborne Impactor Measurements
Simultaneous two-color (0.6943 micrometers and 0.3472 micrometers) LIDAR measurements were made in the troposphere and lower stratosphere over Boulder, Colorado during March 1973. In addition, on the evening of March 26, airborne single-stage impactor measurements were made at four altitudes-- 10,500, 25,000, 33,000 and 43,000 feet MSL. These data were integrated at constant altitude for 15,45, 45, and 60 minutes respectively. The LIDAR data were taken with Langley's 48" LIDAR using a dichroic beamsplitter to separate the return at 0.6943 micrometers and 0.3472 micrometers. The analog waveforms for both colors were digitized simultaneously; one on an NCAR data acquisition system and the other on the 48" Langley data acquisition system. A discussion of the preliminary results from these measurements will be presented
Role of water in metal catalyst performance for ketone hydrogenation: a joint experimental and theoretical study on levulinic acid conversion into gamma-valerolactone
While Ru is a poor hydrogenation catalyst compared to Pt or Pd in the gas phase, it is efficient under aqueous phase conditions in the hydrogenation of ketones such as the conversion of levulinic acid into gamma-valerolactone. Combining DFT calculations and experiments, we demonstrate that water is responsible for the enhanced reactivity of Ru under those conditions
Observations of mesoscale and boundary-layer scale circulations affecting dust transport and uplift over the Sahara
Observations of the Saharan boundary layer, made during the GERBILS field campaign, show that mesoscale land surface temperature variations (which were related to albedo variations) induced mesoscale circulations. With weak winds along the aircraft track, land surface temperature anomalies with scales of greater than 10 km are shown to significantly affect boundary-layer temperatures and winds. Such anomalies are expected to affect the vertical mixing of the dusty and weakly stratified Saharan Residual Layer (SRL). Mesoscale variations in winds are also shown to affect dust loadings in the boundary layer. <br><br> Using the aircraft observations and data from the COSMO model, a region of local dust uplift, with strong along-track winds, was identified in one low-level flight. Large eddy model (LEM) simulations based on this location showed linearly organised boundary-layer convection. Calculating dust uplift rates from the LEM wind field showed that the boundary-layer convection increased uplift by approximately 30%, compared with the uplift rate calculated neglecting the convection. The modelled effects of boundary-layer convection on uplift are shown to be larger when the boundary-layer wind is decreased, and most significant when the mean wind is below the threshold for dust uplift and the boundary-layer convection leads to uplift which would not otherwise occur. <br><br> Both the coupling of albedo features to the atmosphere on the mesoscale, and the enhancement of dust uplift by boundary-layer convection are unrepresented in many climate models, but may have significant impacts on the vertical transport and uplift of desert dust. Mesoscale effects in particular tend to be difficult to parametrise
Comments: Walking the Line of Admissibility: Why Maryland Courts Should Reexamine the Admissibility of Field Sobriety Tests
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