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

Gender Based Within-Household Inequality in Childhood Immunization in India: Changes over Time and across Regions

Background and Objectives: Despite India’s substantial economic growth in the past two decades, girls in India are discriminated against in access to preventive healthcare including immunizations. Surprisingly, no study has assessed the contribution of gender based within-household discrimination to the overall inequality in immunization status of Indian children. This study therefore has two objectives: to estimate the gender based within-household inequality (GWHI) in immunization status of Indian children and to examine the inter-regional and inter-temporal variations in the GWHI. Data and Methods: The present study used households with a pair of male-female siblings (aged 1–5 years) from two rounds of National Family Health Survey (NFHS, 1992–93 and 2005–06). The overall inequality in the immunization status (after controlling for age and birth order) of children was decomposed into within-households and between-households components using Mean log deviation to obtain the GWHI component. The analysis was conducted at the all-India level as well as for six specified geographical regions and at two time points (1992–93 and 2005–06). Household fixed-effects models for immunization status of children were also estimated. Results and Conclusions: Findings from household fixed effects analysis indicated that the immunization scores of girls were significantly lower than that of boys. The inequality decompositions revealed that, at the all-India level, the absolute level of GWHI in immunization status decreased from 0.035 in 1992–93 to 0.023 in 2005–06. However, as a percentage o

Using an equity-based framework for evaluating publicly funded health insurance programmes as an instrument of UHC in Chhattisgarh State, India

Universal health coverage (UHC) has provided the impetus for the introduction of publicly funded health insurance (PFHI) schemes in the mixed health systems of India and many other low- and middle-income countries. There is a need for a holistic understanding of the pathways of impact of PFHI schemes, including their role in promoting equity of access. Methods: This paper applies an equity-oriented evaluation framework to assess the impacts of PFHI schemes in Chhattisgarh State by synthesising literature from various sources and highlighting knowledge gaps. Data were collected from an extensive review of publications on PFHI schemes in Chhattisgarh since 2009, including empirical studies from the first author's PhD and grey literature such as programme evaluation reports, media articles and civil society campaign documents. The framework was constructed using concepts and frameworks from the health policy and systems research literature on UHC, access and health system building blocks, and is underpinned by the values of equity, human rights and the right to health

Diffusion theory model of the neutron number probability distribution in a subcritical multiplying assembly

The probability distribution of neutron numbers in a symmetric subcritical reflected fissile sphere is numerically obtained using a one-speed diffusion approximation to the underlying backward Master equation. Employing an accurate space–time discretisation scheme, the coupled but closed system of equations for the number probabilities is sequentially solved as a function of position and time of an injected neutron. This solution is then used to construct the corresponding distributions for a random intrinsic source of arbitrary multiplicity. Numerical results clearly demonstrate the importance of including spatial dependence in the neutron number probability distributions, which show complex spatial behaviours that cannot be encapsulated in a point model system. This is especially evident in the case of the multi-region model where the presence of a reflector is seen to alter the approach to steady state of the number probabilities, while the material interface has a significant effect on the magnitude of the probabilities, both locally and globally

National healthcare economic evaluation guidelines: a cross-country comparison

Background and Objectives Globally, a number of countries have developed guidelines that describe the design and conduct of economic evaluations as part of health technology assessment (HTA) or pharmacoeconomic analysis for decision making. The current scoping review was undertaken with an objective to summarize the recommendations made on methods of economic evaluation by the national healthcare economic evaluation (HEE) guidelines. Methodology A comprehensive search was undertaken in the website repositories of the International Society for Pharmacoeconomic and Outcomes Research (ISPOR) and Guide to Economic Analysis and Research (GEAR), and websites of national HTA agencies and ministries of health of individual countries. All guidelines in the English language were included in this review. Data were extracted with respect to general and methodological characteristics, and a descriptive analysis of recommendations made across the countries was undertaken. Results Overall, our review included 31 national HEE guidelines, published between 1997 and August 2020. Nearly half (45%) of the guidelines targeted the evaluation of pharmaceuticals. The nature of the guidelines was either mandatory (31%), recommendatory (42%), or voluntary (16%). There was a substantial consensus among the guidelines on several key principles, including type of economic evaluation (cost-utility analysis), time horizon of the analysis (long enough), health outcome measure (quality-adjusted life-years) and use of sensitivity analyses. The recommendations on study perspective, comparator, discount rate and type of costs to be included (particularly the inclusion of indirect costs) varied widely. Conclusion Despite similarity in the overall processes, variation in several recommendations given by various national HEE guidelines was observed. This is perhaps unsurprising given the differences in the health systems and financing mechanisms, capacity of local researchers, and data availability. This review offers important lessons and a starting point for countries that are planning to develop their own HEE guidelines