270 research outputs found

    On the energy of gamma-ray bursts

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    We show that gamma-ray burst (GRB) afterglow observations strongly suggest, within the fireball model framework, that radiating electrons are shock accelerated to a power-law energy distribution, with universal index p \approx 2.2, and that the fraction of shock energy carried by electrons, \xi_e, is universal and close to equipartition, \xi_e ~ 1/3. For universal p and \xi_e, a single measurement of the X-ray afterglow flux on the time scale of a day provides a robust estimate of the fireball energy per unit solid angle, \epsilon, averaged over a conical section of the fireball of opening angle \theta ~ 0.1. Applying our analysis to BeppoSAX afterglow data we find that: (i) Fireball energies are in the range of 4\pi\epsilon=10^{51.5} to 10^{53.5} erg; (ii) The ratio of observed γ\gamma-ray to total fireball energy per unit solid angle, \epsilon_\gamma / \epsilon, is of order unity, satisfying abs[log10(\epsilon_\gamma/\epsilon)]<0.5; (iii) If fireballs are jet like, their opening angle should satisfy \theta>=0.1. Our results imply that if typical opening angles are \theta ~ 0.1, a value consistent with our analysis, the total energy associated with a GRB event is in the range of 10^{50} erg to 10^{51.5} erg.Comment: 16 pages; Submitted to Ap

    Do family relationships buffer the impact of disability on older adults' daily mood? An exploration of gender and marital status differences

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    OBJECTIVE: We evaluate whether non-spousal family support and strain moderate the effect of disability on two daily emotions (happiness and frustration) among older adults, and whether these patterns differ by gender among married persons, and by marital status among women. BACKGROUND: Stress buffering perspectives predict that harmful effects of stress on well-being are buffered by family support, whereas stress proliferation models suggest these effects are intensified by family strain. The extent to which family relationships moderate associations between stress and well-being may vary on the basis of gender and marital status, as non-spousal family ties are considered especially salient for women and those without a romantic partner. METHOD: Daily diary data are from the 2013 Disability and Use of Time supplement to the Panel Study of Income Dynamics (n=1,474), a national sample of adults ages 60+. Multivariate regression models are estimated for married/partnered men and women, and formerly married women. RESULTS: Neither family support nor strain moderated the effect of severe impairment on married men's daily emotions. Family support buffered the effect of severe impairment on frustration among divorced and widowed women, but not their married counterparts. Counterintuitively, family arguments mitigated against frustration and increased happiness among married women with severe impairment. CONCLUSION: Consistent with stress buffering perspectives, family support was most protective for the vulnerable population of formerly married older women with severe impairment. IMPLICATIONS: This study underscores the importance of family support for the large and growing population of formerly married women managing health-related challenges in later life.P01 AG029409 - NIA NIH HHS; R01 AG040213 - NIA NIH HHS; R01 HD069609 - NICHD NIH HHSAccepted manuscrip

    Common variants in the ATM, BRCA1, BRCA2, CHEK2 and TP53 cancer susceptibility genes are unlikely to increase breast cancer risk

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    RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are.Abstract Introduction Certain rare, familial mutations in the ATM, BRCA1, BRCA2, CHEK2 or TP53 genes increase susceptibility to breast cancer but it has not, until now, been clear whether common polymorphic variants in the same genes also increase risk. Methods We have attempted a comprehensive, single nucleotide polymorphism (SNP)- and haplotype-tagging association study on each of these five genes in up to 4,474 breast cancer cases from the British, East Anglian SEARCH study and 4,560 controls from the EPIC-Norfolk study, using a two-stage study design. Nine tag SNPs were genotyped in ATM, together with five in BRCA1, sixteen in BRCA2, ten in CHEK2 and five in TP53, with the aim of tagging all other known, common variants. SNPs generating the common amino acid substitutions were specifically forced into the tagging set for each gene. Results No significant breast cancer associations were detected with any individual or combination of tag SNPs. Conclusion It is unlikely that there are any other common variants in these genes conferring measurably increased risks of breast cancer in our study population

    Strengthening the reporting of genetic risk prediction studies (GRIPS): explanation and elaboration

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    The rapid and continuing progress in gene discovery for complex diseases is fuelling interest in the potential application of genetic risk models for clinical and public health practice. The number of studies assessing the predictive ability is steadily increasing, but they vary widely in completeness of reporting and apparent quality. Transparent reporting of the strengths and weaknesses of these studies is important to facilitate the accumulation of evidence on genetic risk prediction. A multidisciplinary workshop sponsored by the Human Genome Epidemiology Network developed a checklist of 25 items recommended for strengthening the reporting of Genetic RIsk Prediction Studies (GRIPS), building on the principles established by prior reporting guidelines. These recommendations aim to enhance the transparency, quality and completeness of study reporting, and thereby to improve the synthesis and application of information from multiple studies that might differ in design, conduct or analysis

    Determinants of subject visit participation in a prospective cohort study of HTLV infection

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    <p>Abstract</p> <p>Background</p> <p>Understanding participation in a prospective study is crucial to maintaining and improving retention rates. In 1990–92, following attempted blood donation at five blood centers, we enrolled 155 HTLV-I, 387 HTLV-II and 799 HTLV seronegative persons in a long-term prospective cohort.</p> <p>Methods</p> <p>Health questionnaires and physical exams were administered at enrollment and 2-year intervals through 2004. To examine factors influencing attendance at study visits of the cohort participants we calculated odds ratios (ORs) with generalized estimated equations (GEE) to analyze fixed and time-varying predictors of study visit participation.</p> <p>Results</p> <p>There were significant independent associations between better visit attendance and female gender (OR = 1.31), graduate education (OR = 1.86) and income > 75,000(OR=2.68).Participantsattwocenters(OR=0.47,0.67)andofBlackrace/ethnicity(OR=0.61)werelesslikelytocontinue.Highersubjectreimbursementforinterviewwasassociatedwithbettervisitattendance(OR=1.84for75,000 (OR = 2.68). Participants at two centers (OR = 0.47, 0.67) and of Black race/ethnicity (OR = 0.61) were less likely to continue. Higher subject reimbursement for interview was associated with better visit attendance (OR = 1.84 for 25 vs. $10). None of the health related variables (HTLV status, perceived health status and referral to specialty diagnostic exam for potential adverse health outcomes) significantly affected participation after controlling for demographic variables.</p> <p>Conclusion</p> <p>Increasing and maintaining participation by minority and lower socioeconomic status participants is an ongoing challenge in the study of chronic disease outcomes. Future studies should include methods to evaluate attrition and retention, in addition to primary study outcomes, including qualitative analysis of reasons for participation or withdrawal.</p
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