X-Ray Spectroscopy of Stars

(abridged) Non-degenerate stars of essentially all spectral classes are soft X-ray sources. Low-mass stars on the cooler part of the main sequence and their pre-main sequence predecessors define the dominant stellar population in the galaxy by number. Their X-ray spectra are reminiscent, in the broadest sense, of X-ray spectra from the solar corona. X-ray emission from cool stars is indeed ascribed to magnetically trapped hot gas analogous to the solar coronal plasma. Coronal structure, its thermal stratification and geometric extent can be interpreted based on various spectral diagnostics. New features have been identified in pre-main sequence stars; some of these may be related to accretion shocks on the stellar surface, fluorescence on circumstellar disks due to X-ray irradiation, or shock heating in stellar outflows. Massive, hot stars clearly dominate the interaction with the galactic interstellar medium: they are the main sources of ionizing radiation, mechanical energy and chemical enrichment in galaxies. High-energy emission permits to probe some of the most important processes at work in these stars, and put constraints on their most peculiar feature: the stellar wind. Here, we review recent advances in our understanding of cool and hot stars through the study of X-ray spectra, in particular high-resolution spectra now available from XMM-Newton and Chandra. We address issues related to coronal structure, flares, the composition of coronal plasma, X-ray production in accretion streams and outflows, X-rays from single OB-type stars, massive binaries, magnetic hot objects and evolved WR stars.Comment: accepted for Astron. Astrophys. Rev., 98 journal pages, 30 figures (partly multiple); some corrections made after proof stag

Daily Physical Activities and Sports in Adult Survivors of Childhood Cancer and Healthy Controls: A Population-Based Questionnaire Survey

BACKGROUND: Healthy lifestyle including sufficient physical activity may mitigate or prevent adverse long-term effects of childhood cancer. We described daily physical activities and sports in childhood cancer survivors and controls, and assessed determinants of both activity patterns. METHODOLOGY/PRINCIPAL FINDINGS: The Swiss Childhood Cancer Survivor Study is a questionnaire survey including all children diagnosed with cancer 1976-2003 at age 0-15 years, registered in the Swiss Childhood Cancer Registry, who survived ≥5 years and reached adulthood (≥20 years). Controls came from the population-based Swiss Health Survey. We compared the two populations and determined risk factors for both outcomes in separate multivariable logistic regression models. The sample included 1058 survivors and 5593 controls (response rates 78% and 66%). Sufficient daily physical activities were reported by 52% (n = 521) of survivors and 37% (n = 2069) of controls (p<0.001). In contrast, 62% (n = 640) of survivors and 65% (n = 3635) of controls reported engaging in sports (p = 0.067). Risk factors for insufficient daily activities in both populations were: older age (OR for ≥35 years: 1.5, 95CI 1.2-2.0), female gender (OR 1.6, 95CI 1.3-1.9), French/Italian Speaking (OR 1.4, 95CI 1.1-1.7), and higher education (OR for university education: 2.0, 95CI 1.5-2.6). Risk factors for no sports were: being a survivor (OR 1.3, 95CI 1.1-1.6), older age (OR for ≥35 years: 1.4, 95CI 1.1-1.8), migration background (OR 1.5, 95CI 1.3-1.8), French/Italian speaking (OR 1.4, 95CI 1.2-1.7), lower education (OR for compulsory schooling only: 1.6, 95CI 1.2-2.2), being married (OR 1.7, 95CI 1.5-2.0), having children (OR 1.3, 95CI 1.4-1.9), obesity (OR 2.4, 95CI 1.7-3.3), and smoking (OR 1.7, 95CI 1.5-2.1). Type of diagnosis was only associated with sports. CONCLUSIONS/SIGNIFICANCE: Physical activity levels in survivors were lower than recommended, but comparable to controls and mainly determined by socio-demographic and cultural factors. Strategies to improve physical activity levels could be similar as for the general population

Physical activity, obesity and cardiometabolic risk factors in 9- to 10-year-old UK children of white European, South Asian and black African-Caribbean origin: the Child Heart And health Study in England (CHASE)

Physical inactivity is implicated in unfavourable patterns of obesity and cardiometabolic risk in childhood. However, few studies have quantified these associations using objective physical activity measurements in children from different ethnic groups. We examined these associations in UK children of South Asian, black African-Caribbean and white European origin. This was a cross-sectional study of 2,049 primary school children in three UK cities, who had standardised anthropometric measurements, provided fasting blood samples and wore activity monitors for up to 7 days. Data were analysed using multilevel linear regression and allowing for measurement error. Overall physical activity levels showed strong inverse graded associations with adiposity markers (particularly sum of skinfold thicknesses), fasting insulin, HOMA insulin resistance, triacylglycerol and C-reactive protein; for an increase of 100 counts of physical activity per min of registered time, levels of these factors were 12.2% (95% CI 10.2-14.1%), 10.2% (95% CI 7.5-12.8%), 10.2% (95% CI 7.5-12.8%), 5.8% (95% CI 4.0-7.5%) and 19.2% (95% CI 13.9-24.2%) lower, respectively. Similar increments in physical activity levels were associated with lower diastolic blood pressure (1.0 mmHg, 95% CI 0.6-1.5 mmHg) and LDL-cholesterol (0.04 mmol/l, 95% CI 0.01-0.07 mmol/l), and higher HDL-cholesterol (0.02 mmol/l, 95% CI 0.01-0.04 mmol/l). Moreover, associations were broadly similar in strength in all ethnic groups. All associations between physical activity and cardiometabolic risk factors were reduced (albeit variably) after adjustment for adiposity. Objectively measured physical activity correlates at least as well with obesity and cardiometabolic risk factors in South Asian and African-Caribbean children as in white European children, suggesting that efforts to increase activity levels in such groups would have equally beneficial effect

Psychiatry out-of-hours: a focus group study of GPs' experiences in Norwegian casualty clinics

Background: For Norwegian general practitioners (GPs), acute treatment of mental illness and substance abuse are among the most commonly experienced emergency situations in out-of-hours primary healthcare. The largest share of acute referrals to emergency psychiatric wards occurs out-of-hours, and out-of-hours services are responsible for a disproportionately high share of compulsory referrals. Concerns exist regarding the quality of mental healthcare provided in the out-of-hours setting. The aim of this study was to explore which challenges GPs experience when providing emergency care out-of-hours to patients presenting problems related to mental illness or substance abuse. Methods: We conducted a qualitative study based on two individual interviews and six focus groups with purposively sampled GPs (totally 45 participants). The interviews were analysed successively in an editing style, using a thematic approach based on methodological descriptions by Charmaz and Malterud. Results: Safety and uncertainty were the dominating themes in the discussions. The threat to personal safety due to unpredictable patient behaviour was a central concern, and present security precautions in the out-of-hours services were questioned. The GPs expressed high levels of uncertainty in their work with patients presenting problems related to mental illness or substance abuse. The complexity of the problems presented, shortage of time, limited access to reliable information and limited range of interventions available during out-of-hours contributed to this uncertainty. Perceived access to second opinion seemed to have a major impact on subjectively experienced work stress. Conclusions: The GPs experienced out-of-hours psychiatry as a field with high levels of uncertainty and limited support to help them meet the experienced challenges. This might influence the quality of care provided. If the current organisation of emergency mental healthcare is to be kept, we need to provide GPs with a better support framework out-of-hours

One size fits all? High frequency trading, tick size changes and the implications for exchanges: market quality and market structure considerations

This paper offers a systematic review of the empirical literature on the implications of tick size changes for exchanges. Our focus is twofold: first, we are concerned with the market quality implications of a change in the minimum tick size. Second, we are interested in the implications of changes in the minimum tick size on market structure. We show that there is a large body of empirical literature that documents a decrease in transaction costs following a decrease in the minimum tick size. However, even though market liquidity increases, the incentive to provide market making activities decreases. We document a strong link between the minimum tick size regulations and the recent increase in high frequency trading activity. A smaller tick enhances the price discovery process. However, the question of how multiple tick size regimes affect market liquidity in a fragmented market remains to be answered. Finally, we identify topics for future research; we discuss the empirical literature on the minimum trade unit and the recent calls for a minimum resting time for quotes

Parent and child physical activity and sedentary time: Do active parents foster active children?

<p>Abstract</p> <p>Background</p> <p>Physical activity has many positive effects on children's health while TV viewing has been associated with adverse health outcomes. Many children do not meet physical activity recommendations and exceed TV viewing guidelines. Parents are likely to be an important influence on their children's behaviour. There is an absence of information about the associations between parents' and children's physical activity and TV viewing.</p> <p>Methods</p> <p>Year 6 children and their parent were recruited from 40 primary schools. Results are presented for the 340 parent-child dyads with accelerometer data that met a ≥ 3 day inclusion criteria and the 431 parent-child dyads with complete self-reported TV viewing. Over 80% of the dyads with valid TV viewing data included mothers and their child. Mean minutes of moderate to vigorous physical activity (MVPA), minutes of sedentary time per day and counts per minute were assessed by accelerometer. Self-reported hours of TV viewing were coded into 3 groups (< 2 hours per day, 2-4 hours per day and >4 hours per day. Linear and multi-nominal regression models were run by child gender to examine parent-child associations.</p> <p>Results</p> <p>In linear regression models there was an association for the overall sedentary time of girls and their parents (t = 2.04. p = .020) but there was no association between girls' and parents' physical activity. There were no associations between parents' and boys' sedentary or physical activity time. For girls, the risk of watching more than 4 hours of TV per day, (reference = 2 hours of TV per day), was 3.67 times higher if the girl's parent watched 2-4 hours of TV per day (p = 0.037). For boys, the risk of watching more than 4 hours of TV per day, was 10.47 times higher if the boy's parent watched more than 4 hours of TV per day (p = 0.038).</p> <p>Conclusions</p> <p>There are associations in the sedentary time of parents and daughters. Higher parental TV viewing was associated with an increased risk of high levels of TV viewing for both boys and girls. There were no associations between the time that parents and children spend engaged in physical activity.</p

OSS (Outer Solar System): A fundamental and planetary physics mission to Neptune, Triton and the Kuiper Belt

The present OSS mission continues a long and bright tradition by associating the communities of fundamental physics and planetary sciences in a single mission with ambitious goals in both domains. OSS is an M-class mission to explore the Neptune system almost half a century after flyby of the Voyager 2 spacecraft. Several discoveries were made by Voyager 2, including the Great Dark Spot (which has now disappeared) and Triton's geysers. Voyager 2 revealed the dynamics of Neptune's atmosphere and found four rings and evidence of ring arcs above Neptune. Benefiting from a greatly improved instrumentation, it will result in a striking advance in the study of the farthest planet of the Solar System. Furthermore, OSS will provide a unique opportunity to visit a selected Kuiper Belt object subsequent to the passage of the Neptunian system. It will consolidate the hypothesis of the origin of Triton as a KBO captured by Neptune, and improve our knowledge on the formation of the Solar system. The probe will embark instruments allowing precise tracking of the probe during cruise. It allows to perform the best controlled experiment for testing, in deep space, the General Relativity, on which is based all the models of Solar system formation. OSS is proposed as an international cooperation between ESA and NASA, giving the capability for ESA to launch an M-class mission towards the farthest planet of the Solar system, and to a Kuiper Belt object. The proposed mission profile would allow to deliver a 500 kg class spacecraft. The design of the probe is mainly constrained by the deep space gravity test in order to minimise the perturbation of the accelerometer measurement.Comment: 43 pages, 10 figures, Accepted to Experimental Astronomy, Special Issue Cosmic Vision. Revision according to reviewers comment

No evidence that genetic variation in the myeloid-derived suppressor cell pathway influences ovarian cancer survival

BACKGROUND: The precise mechanism by which the immune system is adversely affected in cancer patients remains poorly understood, but the accumulation of immune suppressive/pro-tumorigenic myeloid-derived suppressor cells (MDSCs) is thought to be one prominent mechanism contributing to immunologic tolerance of malignant cells in epithelial ovarian cancer (EOC). To this end, we hypothesized genetic variation in MDSC pathway genes would be associated with survival after EOC diagnoses. METHODS: We measured the hazard of death due to EOC within 10 years of diagnosis, overall and by invasive subtype, attributable to SNPs in 24 genes relevant in the MDSC pathway in 10,751 women diagnosed with invasive EOC. Versatile Gene-based Association study (VEGAS) and the Admixture Likelihood method (AML), were used to test gene and pathway associations with survival. RESULTS: We did not identify individual SNPs that were significantly associated with survival after correction for multiple testing (p<3.5 x 10-5), nor did we identify significant associations between the MDSC pathway overall, or the 24 individual genes and EOC survival. CONCLUSIONS: In this well-powered analysis, we observed no evidence that inherited variations in MDSC-associated SNPs, individual genes, or the collective genetic pathway contributed to EOC survival outcomes. IMPACT: Common inherited variation in genes relevant to MDSCs were not associated with survival in women diagnosed with invasive EOC

Increased Systemic Th17 Cytokines Are Associated with Diastolic Dysfunction in Children and Adolescents with Diabetic Ketoacidosis

Diastolic dysfunction suggestive of diabetic cardiomyopathy is established in children with T1DM, but its pathogenesis is not well understood. We studied the relationships of systemic inflammatory cytokines/chemokines and cardiac function in 17 children with T1DM during and after correction of diabetic ketoacidosis (DKA). Twenty seven of the 39 measured cytokines/chemokines were elevated at 6–12 hours into treatment of DKA compared to values after DKA resolution. Eight patients displayed at least one parameter of diastolic abnormality (DA) during acute DKA. Significant associations were present between nine of the cytokine/chemokine levels and the DA over time. Interestingly, four of these nine interactive cytokines (GM-CSF, G-CSF, IL-12p40, IL-17) are associated with a Th17 mediated cell response. Both the DA and CCL7 and IL-12p40, had independent associations with African American patients. Thus, we report occurrence of a systemic inflammatory response and the presence of cardiac diastolic dysfunction in a subset of young T1DM patients during acute DKA