Low Mach Number Modeling of Type Ia Supernovae

We introduce a low Mach number equation set for the large-scale numerical simulation of carbon-oxygen white dwarfs experiencing a thermonuclear deflagration. Since most of the interesting physics in a Type Ia supernova transpires at Mach numbers from 0.01 to 0.1, such an approach enables both a considerable increase in accuracy and savings in computer time compared with frequently used compressible codes. Our equation set is derived from the fully compressible equations using low Mach number asymptotics, but without any restriction on the size of perturbations in density or temperature. Comparisons with simulations that use the fully compressible equations validate the low Mach number model in regimes where both are applicable. Comparisons to simulations based on the more traditional anelastic approximation also demonstrate the agreement of these models in the regime for which the anelastic approximation is valid. For low Mach number flows with potentially finite amplitude variations in density and temperature, the low Mach number model overcomes the limitations of each of the more traditional models and can serve as the basis for an accurate and efficient simulation tool.Comment: Accepted for publication in the Astrophysical Journal 31 pages, 5 figures (some figures degraded in quality to conserve space

Linear approaches to intramolecular Förster Resonance Energy Transfer probe measurements for quantitative modeling

Numerous unimolecular, genetically-encoded Forster Resonance Energy Transfer (FRET) probes for monitoring biochemical activities in live cells have been developed over the past decade. As these probes allow for collection of high frequency, spatially resolved data on signaling events in live cells and tissues, they are an attractive technology for obtaining data to develop quantitative, mathematical models of spatiotemporal signaling dynamics. However, to be useful for such purposes the observed FRET from such probes should be related to a biological quantity of interest through a defined mathematical relationship, which is straightforward when this relationship is linear, and can be difficult otherwise. First, we show that only in rare circumstances is the observed FRET linearly proportional to a biochemical activity. Therefore in most cases FRET measurements should only be compared either to explicitly modeled probes or to concentrations of products of the biochemical activity, but not to activities themselves. Importantly, we find that FRET measured by standard intensity-based, ratiometric methods is inherently non-linear with respect to the fraction of probes undergoing FRET. Alternatively, we find that quantifying FRET either via (1) fluorescence lifetime imaging (FLIM) or (2) ratiometric methods where the donor emission intensity is divided by the directly-excited acceptor emission intensity (denoted R<sub>alt</sub>) is linear with respect to the fraction of probes undergoing FRET. This linearity property allows one to calculate the fraction of active probes based on the FRET measurement. Thus, our results suggest that either FLIM or ratiometric methods based on R<sub>alt</sub> are the preferred techniques for obtaining quantitative data from FRET probe experiments for mathematical modeling purpose

Socioeconomic status, alcohol use disorders, and depression: A population-based study.

Depressive disorders (DD) and alcohol use disorders (AUD) frequently co-occur. They are key to understanding the current increases in "deaths of despair" among individuals with lower socioeconomic status (SES). The aim of this study was to assess the prospective bidirectional associations between AUD and DD, as well as the effect of SES on these two conditions. The National Epidemiologic Survey on Alcohol and Related Conditions is a cohort study representative of the US adult population, which began in 2001-2002, with follow-up interviews conducted 3 years later. SES was primarily operationalized as educational attainment. AUD, DD, and their levels of severity were defined according to the DSM-5 criteria. The risk of developing an incident DD increased gradually with the recency and the severity of AUD at baseline, but the converse was not observed. Lower SES was an independent risk for incident AUD or DD. SES did not modify the prospective association between AUD and DD. The absence of interaction between SES and moderate or severe AUD for the incident DD must be considered with caution due to the limited number of DD cases reported in these AUD categories. This result is consistent with a causal relationship between AUD and DD, and suggests that therapeutic interventions for AUD may also have beneficial effects to lower DD rates. The independent effects of a lower SES and AUD on DD may result in a vulnerable population cumulating disorders with heavy consequences on health and social well-being

Non-fatal injuries in three Central and Eastern European urban population samples: the HAPIEE study

Background: Despite high mortality from injuries and accidents, data on rates and distribution of non-fatal injuries in Central and Eastern European populations are scarce. Methods: Cross-sectional study of random population samples of 45–69-year-old men and women (n = 28 600) from Novosibirsk (Russia), Krakow (Poland) and six Czech towns, participating in the Health, Alcohol and Psychosocial factors In Eastern Europe (HAPIEE) study. Participants provided information on non-fatal injuries in the past 12 months, socio-economic characteristics, alcohol consumption and other covariates. Results: The period prevalence of non-fatal injuries in the last year among Czech, Russian and Polish men was 12.5, 9.4 and 5.3%, respectively; among women, the respective proportions were 9.9, 9.8 and 6.4%. Injury prevalence declined with age in men and increased with age in women. Higher injury prevalence was associated with being unmarried, material deprivation, higher drinking frequency and problem drinking. In the pooled data, the adjusted odds ratio (OR) for the highest versus lowest material deprivation category was 1.57 [95% confidence interval (CI) 1.38–1.79]; for problem drinking, the OR was 1.44 (95% CI 1.23–1.69). Alcohol did not mediate the link between socio-economic status and injury. Conclusion: Non-fatal injuries were associated with material deprivation, other socio-economic characteristics and with alcohol. These results not only underscore the universality of the inequality phenomenon, but also suggest that the mediating role of alcohol in social differentials in non-fatal injury remains an unresolved issue

Determination of Omega_b From Big Bang Nucleosynthesis in the Presence of Regions of Antimatter

Production of regions of antimatter in the early universe is predicted in many baryogenesis models. Small scale antimatter regions would annihilate during or soon after nucleosynthesis, affecting the abundances of the light elements. In this paper we study how the acceptable range in Omega_b changes in the presence of antimatter regions, as compared to the standard big bang nucleosynthesis. It turns out that it is possible to produce at the same time both a low 4He value (Y_p < 0.240) and a low D/H value (D/H < 4e-5), but overproduction of 7Li is unavoidable at large Omega_b.Comment: 9 pages, PRD version, ref. 6 correcte

sidestep Encodes a Target-Derived Attractant Essential for Motor Axon Guidance in Drosophila

AbstractAt specific choice points in the periphery, subsets of motor axons defasciculate from other axons in the motor nerves and steer into their muscle target regions. Using a large-scale genetic screen in Drosophila, we identified the sidestep (side) gene as essential for motor axons to leave the motor nerves and enter their muscle targets. side encodes a target-derived transmembrane protein (Side) that is a novel member of the immunoglobulin superfamily (IgSF). Side is expressed on embryonic muscles during the period when motor axons leave their nerves and extend onto these muscles. In side mutant embryos, motor axons fail to extend onto muscles and instead continue to extend along their motor nerves. Ectopic expression of Side results in extensive and prolonged motor axon contact with inappropriate tissues expressing Side

Beam heat load analysis with COLDDIAG: a cold vacuum chamber for diagnostics

The knowledge of the heat intake from the electron beam is essential to design the cryogenic layout of superconducting insertion devices. With the aim of measuring the beam heat load to a cold bore and understanding the responsible mechanisms, a cold vacuum chamber for diagnostics (COLDDIAG) has been built. The instrumentation comprises temperature sensors, pressure gauges, mass spectrometers and retarding field analyzers, which allow to study the beam heat load and the influence of the cryosorbed gas layer. COLDDIAG was installed in the storage ring of the Diamond Light Source from September 2012 to August 2013. During this time measurements were performed for a wide range of machine conditions, employing the various measuring capabilities of the device. Here we report on the analysis of the measured beam heat load, pressure and gas content, as well as the low energy charged particle flux and spectrum as a function of the electron beam parameters

Stellar 36,38^{36,38}Ar(n,γ)37,39(n,\gamma)^{37,39}Ar reactions and their effect on light neutron-rich nuclide synthesis

The $^{36}$Ar$(n,\gamma)^{37}$Ar ($t_{1/2}$ = 35 d) and $^{38}$Ar$(n,\gamma)^{39}$Ar (269 y) reactions were studied for the first time with a quasi-Maxwellian ($kT \sim 47$ keV) neutron flux for Maxwellian Average Cross Section (MACS) measurements at stellar energies. Gas samples were irradiated at the high-intensity Soreq applied research accelerator facility-liquid-lithium target neutron source and the $^{37}$Ar/$^{36}$Ar and $^{39}$Ar/$^{38}$Ar ratios in the activated samples were determined by accelerator mass spectrometry at the ATLAS facility (Argonne National Laboratory). The $^{37}$Ar activity was also measured by low-level counting at the University of Bern. Experimental MACS of $^{36}$Ar and $^{38}$Ar, corrected to the standard 30 keV thermal energy, are 1.9(3) mb and 1.3(2) mb, respectively, differing from the theoretical and evaluated values published to date by up to an order of magnitude. The neutron capture cross sections of $^{36,38}$Ar are relevant to the stellar nucleosynthesis of light neutron-rich nuclides; the two experimental values are shown to affect the calculated mass fraction of nuclides in the region A=36-48 during the weak $s$-process. The new production cross sections have implications also for the use of $^{37}$Ar and $^{39}$Ar as environmental tracers in the atmosphere and hydrosphere.Comment: 18 pages + Supp. Mat. (13 pages) Accepted for publication in Phys. Rev. Let