292 research outputs found

    Measuring the neutron star equation of state using X-ray timing

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    One of the primary science goals of the next generation of hard X-ray timing instruments is to determine the equation of state of the matter at supranuclear densities inside neutron stars, by measuring the radius of neutron stars with different masses to accuracies of a few percent. Three main techniques can be used to achieve this goal. The first involves waveform modelling. The flux we observe from a hotspot on the neutron star surface offset from the rotational pole will be modulated by the star's rotation, giving rise to a pulsation. Information about mass and radius is encoded into the pulse profile via relativistic effects, and tight constraints on mass and radius can be obtained. The second technique involves characterising the spin distribution of accreting neutron stars. The most rapidly rotating stars provide a very clean constraint, since the mass-shedding limit is a function of mass and radius. However the overall spin distribution also provides a guide to the torque mechanisms in operation and the moment of inertia, both of which can depend sensitively on dense matter physics. The third technique is to search for quasi-periodic oscillations in X-ray flux associated with global seismic vibrations of magnetars (the most highly magnetized neutron stars), triggered by magnetic explosions. The vibrational frequencies depend on stellar parameters including the dense matter equation of state. We illustrate how these complementary X-ray timing techniques can be used to constrain the dense matter equation of state, and discuss the results that might be expected from a 10m2^2 instrument. We also discuss how the results from such a facility would compare to other astronomical investigations of neutron star properties. [Modified for arXiv]Comment: To appear in Reviews of Modern Physics as a Colloquium, 23 pages, 9 figure

    Co-enrollment for Child Health: How Receipt and Loss of Food and Housing Subsidies Relate to Housing Security and Statutes for Streamlined, Multi-Subsidy Application

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    In light of recent policy debates around funding food and housing subsidies, the combined influence of these programs on housing security (HS), defined as housing without crowding or frequent moves, remains unstudied. In a multi-city study of young children, federal nutrition and housing subsidies together increased the odds of HS, whereas loss of nutrition subsidies lowered the odds of HS even after controlling for housing subsidy receipt. Ensuring eligible families’ access to both nutrition and housing subsidies may sustain HS. The results of this study inform and support current efforts by states to streamline online applications for social services and remove statutory legal barriers to accessing these subsidies simultaneously

    Trends in Household and Child Food Insecurity Among Families with Young Children from 2007 to 2013

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    Background: 2007-2013 spanned an economic downturn with rising food costs. While Supplemental Nutrition Assistance Program (SNAP) benefits increased during those years by 13.6% from the 2009 American Recovery Reinvestment Act (ARRA), the impact of these competing conditions on household food insecurity (HFI, household food insecure but child food secure) and child food insecurity (CFI, household and child food insecure) in households with infants and toddlers has not been investigated. Objective: To describe HFI and CFI in households participating in SNAP vs. households likely eligible but not participating (No SNAP). Design: Repeat cross-sectional Participants/Setting: 19,999 caregivers of childrenChildren’s HealthWatch survey in emergency and primary care departments in 5 US cities. Main Outcome Measures: The 18-item U.S. Household Food Security Survey (HFSS) measured HFI (≥3 affirmative responses on non-child-specific questions) and CFI (≥2 affirmative responses to eight child-specific questions). Statistical analyses performed: The sample was stratified by SNAP/ No SNAP. Multinomial logistic regression analyses examined the association between SNAP receipt and HFI and CFI. Results: Across the study period, controlling for confounders including year, households with SNAP were 17% less likely to experience HFI (AOR 0.83; 95% CI,0 .75, 0.91; p Conclusions: Receipt of SNAP vs. No SNAP was associated with decreased prevalence of HFI and CFI during much of the economic downturn; this impact waned as the buying power of the boost in benefit amounts during the ARRA period eroded

    The Metaphor of Circle: Stanislavski, Phenomenology of Roundness and High Yoga

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    Stanislavski’s Eastern influence and his persistent fascination with Yoga is an established area of research. Stanislavski has two major yogic influences in the System: Hatha Yoga and Raja Yoga. The first is about training the body through postures, movements, stances and breathing exercises to make it active, relaxed and energetic. The second includes a range of exclusive practices on concentration and visualization that are an integral part of the actor’s creativity. However, in the current research, there is a clear lack of a comprehensive practical method that informs Stanislavski’s use of yogic practice in the System: what specific yogic exercises were used and what synergies were developed in the training? Scholars have, so far, only explored Stanislavski’s literary legacy of his encounter with yoga, identifying the Sanskrit terms appeared in his writings such as prana for breathing and the Indian anecdotes he used when answering the questions of his students. Focusing on the metaphor of the circle, the phenomenology of roundness and the Deleuzian notions of ‘the invisible forces of sensations’ and ‘the body becomes an event itself’, the present study, for the first time, offers useful insights into the fundamental principles of yoga and their methods of practice as a way of developing a new training to understand the significance of Stanislavski in the 21st century

    A polymorphism at codon 31 of gene p21 is not associated with primary open angle glaucoma in Caucasians

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    BACKGROUND: Primary open angle glaucoma (POAG) is considered to be a neurodegenerative optic neuropathy, in which cell death occurs by apoptosis. p21, is an important protective component of the apoptotic pathway, regulating cellular arrest in the presence of DNA damage. An unstable or altered p21 protein could modify the cellular response to genomic injury and abolish the effect of p21. A previous study on a Chinese cohort suggested that the p21 codon 31 polymorphism may alter the state of apoptosis in glaucomatous optic neuropathy, failing to protect the ganglion cells. The aim of this study was to test the hypothesis that a p21 codon 31 polymorphism is associated with POAG on a Caucasian cohort. METHODS: 140 POAG patients and a control group of 73 healthy individuals were included in the study. All the subjects were of Caucasian origin. Genomic DNA was amplified by polymerase chain reaction, followed by enzymatic restriction fragment length polymorphism technique (PCR-RFLP). Patients and controls were genotyped for a single nucleotide polymorphism (C/A transversion) in the third base of codon 31 of p21, which leads to a serine (Ser)/arginine (Arg) substitution. RESULTS: The distribution of the genotypes in the POAG patients showed 128 (91.4%) Ser homozygotes, 10 (7.1%) Ser/Arg heterozygotes and 2 (1.5%) Arg homozygotes. In the control cohort, there were 61 (83.6%) Ser homozygotes and 12 (16.4%) Ser/Arg heterozygotes. No Arg homozygotes were present amongst the control group. Both the allelic and genotypic frequencies of the Ser or Arg residues at codon 31 were not significantly different between POAG patients and controls (Fisher's exact test, P = 0.20 for alleles and P = 0.0561 for genotypes). CONCLUSION: This study suggests that the p21 codon 31 polymorphism does not contribute to the risk of POAG in the Caucasian population

    Colloquium: Measuring the neutron star equation of state using x-ray timing

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    One of the primary science goals of the next generation of hard x-ray timing instruments is to determine the equation of state of matter at supranuclear densities inside neutron stars by measuring the radius of neutron stars with different masses to accuracies of a few percent. Three main techniques can be used to achieve this goal. The first involves waveform modeling. The flux observed from a hotspot on the neutron star surface offset from the rotational pole will be modulated by the star's rotation, and this periodic modulation at the spin frequency is called a pulsation. As the photons propagate through the curved spacetime of the star, information about mass and radius is encoded into the shape of the waveform (pulse profile) via special and general-relativistic effects. Using pulsations from known sources (which have hotspots that develop either during thermonuclear bursts or due to channeled accretion) it is possible to obtain tight constraints on mass and radius. The second technique involves characterizing the spin distribution of accreting neutron stars. A large collecting area enables highly sensitive searches for weak or intermittent pulsations (which yield spin) from the many accreting neutron stars whose spin rates are not yet known. The most rapidly rotating stars provide a clean constraint, since the limiting spin rate where the equatorial surface velocity is comparable to the local orbital velocity, at which mass shedding occurs, is a function of mass and radius. However, the overall spin distribution also provides a guide to the torque mechanisms in operation and the moment of inertia, both of which can depend sensitively on dense matter physics. The third technique is to search for quasiperiodic oscillations in x-ray flux associated with global seismic vibrations of magnetars (the most highly magnetized neutron stars), triggered by magnetic explosions. The vibrational frequencies depend on stellar parameters including the dense matter equation of state, and large-area x-ray timing instruments would provide much improved detection capability. An illustration is given of how these complementary x-ray timing techniques can be used to constrain the dense matter equation of state and the results that might be expected from a 10 m2 instrument are discussed. Also discussed are how the results from such a facility would compare to other astronomical investigations of neutron star properties
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