1,221 research outputs found
Properties of Carbon-Oxygen White Dwarfs From Monte Carlo Stellar Models
We investigate properties of carbon-oxygen white dwarfs with respect to the
composite uncertainties in the reaction rates using the stellar evolution
toolkit, Modules for Experiments in Stellar Astrophysics (MESA) and the
probability density functions in the reaction rate library STARLIB. These are
the first Monte Carlo stellar evolution studies that use complete stellar
models. Focusing on 3 M models evolved from the pre main-sequence to
the first thermal pulse, we survey the remnant core mass, composition, and
structure properties as a function of 26 STARLIB reaction rates covering
hydrogen and helium burning using a Principal Component Analysis and Spearman
Rank-Order Correlation. Relative to the arithmetic mean value, we find the
width of the 95\% confidence interval to be
0.019 M for the core mass at the first thermal pulse,
12.50 Myr for the age, 0.013 for the central temperature, 0.060 for the central density,
2.610 for the central electron
fraction, 5.810,
0.392, and 0.392. Uncertainties in the experimental
C(, triple-, and
N( reaction rates dominate these variations. We
also consider a grid of 1 to 6 M models evolved from the pre
main-sequence to the final white dwarf to probe the sensitivity of the
initial-final mass relation to experimental uncertainties in the hydrogen and
helium reaction rates.Comment: Accepted for publication in The Astrophysical Journal; 19 Pages, 23
Figures, 5 Table
R-process nucleosynthesis calculations with complete nuclear physics input
The r-process constitutes one of the major challenges in nuclear
astrophysics. Its astrophysical site has not yet been identified but there is
observational evidence suggesting that at least two possible sites should
contribute to the solar system abundance of r-process elements and that the
r-process responsible for the production of elements heavier than Z=56 operates
quite robustly producing always the same relative abundances. From the
nuclear-physics point of view the r-process requires the knowledge of a large
number of reaction rates involving exotic nuclei. These include neutron capture
rates, beta-decays and fission rates, the latter for the heavier nuclei
produced in the r-process. We have developed for the first time a complete
database of reaction rates that in addition to neutron-capture rates and
beta-decay half-lives includes all possible reactions that can induce fission
(neutron-capture, beta-decay and spontaneous fission) and the corresponding
fission yields. In addition, we have implemented these reaction rates in a
fully implicit reaction network. We have performed r-process calculations for
the neutrino-driven wind scenario to explore whether or not fission can
contribute to provide a robust r-process pattern
Small bowel obstruction caused by a fast-growing desmoid tumor.
Desmoid tumors are rare tumors which can cause intestinal obstructions. Surgical wide excision is currently the treatment of choice, with the goal of achieving free resection margins
Sum Rules for Magnetic Moments and Polarizabilities in QED and Chiral Effective-Field Theory
We elaborate on a recently proposed extension of the Gerasimov-Drell-Hearn
(GDH) sum rule which is achieved by taking derivatives with respect to the
anomalous magnetic moment. The new sum rule features a {\it linear} relation
between the anomalous magnetic moment and the dispersion integral over a
cross-section quantity. We find some analogy of the linearized form of the GDH
sum rule with the `sideways dispersion relations'. As an example, we apply the
linear sum rule to reproduce the famous Schwinger's correction to the magnetic
moment in QED from a tree-level cross-section calculation and outline the
procedure for computing the two-loop correction from a one-loop cross-section
calculation. The polarizabilities of the electron in QED are considered as well
by using the other forward-Compton-scattering sum rules. We also employ the sum
rules to study the magnetic moment and polarizabilities of the nucleon in a
relativistic chiral EFT framework. In particular we investigate the chiral
extrapolation of these quantities.Comment: 24 pages, 7 figures; several additions, published versio
Room temperature sol-gel fabrication and functionalization for sensor applications
The structure and physical properties of a thin titania sol-gel layer prepared on silicon and silica surfaces were examined. Spectroscopic (FTIR, UV-VIS spectroscopy), refractive index (ellipsometry) and microscopic (light microscopy and SEM/EDS) tools were used to examine both chemical uniformity and physical uniformity of the sol-gel glass layers. The conditions for the fabrication of uniform layers were established, and room temperature dopant incorporation was examined. The absorption bands of porphyrin-containing titania sol-gel layers were characterized. By addition of a metal salt to the titania layer, it was possible to metallate the free-base porphyrin within and change the UV-VIS absorbance of the porphyrin, the basis of metal detection using porphyrins. The metalloporphyrins were detected by localized laser ablation inductive coupled mass spectroscopy (LA-ICP-MS), indicating fairly uniform distribution of metals across the titania surface. © 2012 The Author(s)
Perspectives of Long-Haul WDM Transmission Systems Based on Phase-Insensitive Fiber-Optic Parametric Amplifiers
International audienceThe deployment of phase-insensitive fiber-optic parametric amplifiers (PI-FOPAs) as inline amplifiers in long-haul WDM transmission systems is discussed, and it is outlined how to design PI-FOPAs to be a valuable upgrade option for this application
Looking before we leap: Expanding ethical review processes for AI and data science research
This is the final version. Available from The Ada Lovelace Institute via the DOI in this record.âŻAs part of this work, the Ada Lovelace Institute, the University of Exeterâs Institute for Data Science and Artificial Intelligence, and the Alan Turing Institute developed six mock AI and data science research proposals that represent hypothetical submissions to a Research Ethics Committee. An expert workshop found that case studies are useful training resources for understanding common AI and data science ethical challenges. Their purpose is to prompt reflection on common research ethics issues and the societal implications of different AI and data science research projects. These case studies are for use by students, researchers, members of research ethics committees, funders and other actors in the research ecosystem to further develop their ability to spot and evaluate common ethical issues in AI and data science research.Alan Turing InstituteArts and Humanities Research Counci
The effect of socioeconomic deprivation on the association between an extended measurement of unhealthy lifestyle factors and health outcomes: a prospective analysis of the UK Biobank cohort
Background:
Combinations of lifestyle factors interact to increase mortality. Combinations of traditional factors such as smoking and alcohol are well described, but the additional effects of emerging factors such as television viewing time are not. The effect of socioeconomic deprivation on these extended lifestyle risks also remains unclear. We aimed to examine whether deprivation modifies the association between an extended score of lifestyle-related risk factors and health outcomes.
Methods:
Data for this prospective analysis were sourced from the UK Biobank, a prospective population-based cohort study. We assigned all participants an extended lifestyle score, with 1 point for each unhealthy lifestyle factor (incorporating sleep duration and high television viewing time, in addition to smoking, excessive alcohol, poor diet [low intake of oily fish or fruits and vegetables, and high intake of red meat or processed meats], and low physical activity), categorised as most healthy (score 0â2), moderately healthy (score 3â5), or least healthy (score 6â9). Cox proportional hazards models were used to examine the association between lifestyle score and health outcomes (all-cause mortality and cardiovascular disease mortality and incidence), and whether this association was modified by deprivation. All analyses were landmark analyses, in which participants were excluded if they had an event (death or cardiovascular disease event) within 2 years of recruitment. Participants with non-communicable diseases (except hypertension) and missing covariate data were excluded from analyses. Participants were also excluded if they reported implausible values for physical activity, sleep duration, and total screen time. All analyses were adjusted for age, sex, ethnicity, month of assessment, history of hypertension, systolic blood pressure, medication for hypercholesterolaemia or hypertension, and body-mass index categories.
Findings:
328â594 participants aged 40â69 years were included in the study, with a mean follow-up period of 4·9 years (SD 0·83) after the landmark period for all-cause and cardiovascular disease mortality, and 4·1 years (0·81) for cardiovascular disease incidence. In the least deprived quintile, the adjusted hazard ratio (HR) in the least healthy lifestyle category, compared with the most healthy category, was 1·65 (95% CI 1·25â2·19) for all-cause mortality, 1·93 (1·16â3·20) for cardiovascular disease mortality, and 1·29 (1·10â1·52) for cardiovascular disease incidence. Equivalent HRs in the most deprived quintile were 2·47 (95% CI 2·04â3·00), 3·36 (2·36â4·76), and 1·41 (1·25â1·60), respectively. The HR for trend for one increment change towards least healthy in the least deprived quintile compared with that in the most deprived quintile was 1·25 (95% CI 1·12â1·39) versus 1·55 (1·40â1·70) for all-cause mortality, 1·30 (1·05â1·61) versus 1·83 (1·54â2·18) for cardiovascular disease mortality, and 1·10 (1·04â1·17) versus 1·16 (1·09â1·23) for cardiovascular disease incidence. A significant interaction was found between lifestyle and deprivation for all-cause and cardiovascular disease mortality (both pinteraction<0·0001), but not for cardiovascular disease incidence (pinteraction=0·11).
Interpretation:
Wide combinations of lifestyle factors are associated with disproportionate harm in deprived populations. Social and fiscal policies that reduce poverty are needed alongside public health and individual-level interventions that address a wider range of lifestyle factors in areas of deprivation
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