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

Is the racial composition of your surroundings associated with your levels of social dominance orientation?

We investigate the extent to which minority group members are surrounded by outgroup members in their immediate environment as a predictor of social dominance orientation. Using a large representative sample of New Zealanders, we found that minority group members in outgroup dense environments reported lower levels of social dominance orientation (Study 1). In studies 2 and 3, Asian Australian and Black American participants who were surrounded by outgroup members reported lower social dominance orientation. For majority group (White) participants there was no association between social dominance orientation and outgroup density. Study 4 explained the overall pattern: Black Americans surrounded by outgroup members perceived their group to be of lower status in their immediate environment, and through this, reported lower social dominance orientation. This article adds to growing literature on contextual factors that predict social dominance orientation, especially among minority group members

Regulatory nodD1 and nodD2 genes of Rhizobium tropici strain CIAT 899 and their roles in the early stages of molecular signaling and host-legume nodulation

BACKGROUND: Nodulation and symbiotic nitrogen fixation are mediated by several genes, both of the host legume and of the bacterium. The rhizobial regulatory nodD gene plays a critical role, orchestrating the transcription of the other nodulation genes. Rhizobium tropici strain CIAT 899 is an effective symbiont of several legumes—with an emphasis on common bean (Phaseolus vulgaris)—and is unusual in carrying multiple copies of nodD, the roles of which remain to be elucidated. RESULTS: Phenotypes, Nod factors and gene expression of nodD1 and nodD2 mutants of CIAT 899 were compared with those of the wild type strain, both in the presence and in the absence of the nod-gene-inducing molecules apigenin and salt (NaCl). Differences between the wild type and mutants were observed in swimming motility and IAA (indole acetic acid) synthesis. In the presence of both apigenin and salt, large numbers of Nod factors were detected in CIAT 899, with fewer detected in the mutants. nodC expression was lower in both mutants; differences in nodD1 and nodD2 expression were observed between the wild type and the mutants, with variation according to the inducing molecule, and with a major role of apigenin with nodD1 and of salt with nodD2. In the nodD1 mutant, nodulation was markedly reduced in common bean and abolished in leucaena (Leucaena leucocephala) and siratro (Macroptilium atropurpureum), whereas a mutation in nodD2 reduced nodulation in common bean, but not in the other two legumes. CONCLUSION: Our proposed model considers that full nodulation of common bean by R. tropici requires both nodD1 and nodD2, whereas, in other legume species that might represent the original host, nodD1 plays the major role. In general, nodD2 is an activator of nod-gene transcription, but, in specific conditions, it can slightly repress nodD1. nodD1 and nodD2 play other roles beyond nodulation, such as swimming motility and IAA synthesis. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12864-015-1458-8) contains supplementary material, which is available to authorized users

Introduction: Managing for public service performance: How people and values make a difference

This chapter introduces the overall question that is central to this volume: How does management make a meaningful contribution to public service performance? A summary review of our knowledge of the concepts and relationships that feature in this overall question is provided. Describing the gaps in our knowledge, the chapter explains the approach taken by this volume in order to generate fresh insights. Thus, noting that what constitutes performance is dependent on the institutional context, the public values, and different stakeholders that emphasize some rather than other aspects of public service performance, the chapter introduces the institutional perspective. Signaling parallel lines of research with some centering management systems and others managers’ leadership, the chapter explains the multidisciplinary approach which combines the insights from public management, leadership, human resource management, and work and organization psychology to gain a better understanding of what managers do to impact performance. In addition, this multidisciplinary approach provides insight into how public employees’ attitudes and behaviors contribute to job and organization performance. The chapter concludes by presenting the conceptual model underlying the volume and explains the focus of the individual chapters and their contribution to answering the volume’s overall question

CTG repeat instability and size variation timing in DNA repair-deficient mice

Type 1 myotonic dystrophy is caused by the expansion of an unstable CTG repeat in the DMPK gene. We have investigated the molecular mechanisms underlying the CTG repeat instability by crossing transgenic mice carrying >300 unstable CTG repeats in their human chromatin environment with mice knockout for genes involved in various DNA repair pathways: Msh2 (mismatch repair), Rad52 and Rad54 (homologous recombination) and DNA-PKcs (non-homologous end-joining). Genes of the non-homologous end-joining and homologous recombination pathways did not seem to affect repeat instability. Only lack of Rad52 led to a slight decrease in expansion range. Unexpectedly, the absence of Msh2 did not result in stabilization of the CTG repeats in our model. Instead, it shifted the instability towards contractions rather than expansions, both in tissues and through generations. Furthermore, we carefully analyzed repeat transmissions with different Msh2 genotypes to determine the timing of intergenerational instability. We found that instability over generations depends not only on parental germinal instability, but also on a second event taking place after fertilization

Career Crafting Training Intervention for Physicians: Protocol for a Randomized Controlled Trial

Background: Physicians work in a highly demanding work setting where ongoing changes affect their work and challenge their employability (ie, their ability and willingness to continue working). In this high-pressure environment, physicians could benefit from proactively managing or crafting their careers; however, they tend not to show this behavior. The new concept of career crafting concerns proactively making choices and adapting behavior regarding both short-term job design (ie, job crafting) as well as longer-term career development (ie, career self-management). However, so far, no intervention studies have aimed at enhancing career crafting behavior among physicians. Given that proactive work and career behavior have been shown to be related to favorable outcomes, we designed an intervention to support career crafting behavior and employability of physicians. Objective: The objectives of this study were to describe (1) the development and (2) the design of the evaluation of a randomized controlled career crafting intervention to increase job crafting, career self-management, and employability. Methods: A randomized controlled intervention study was designed for 141 physicians in two Dutch hospitals. The study was designed and will be evaluated based on parts of the intervention mapping protocol. First, needs of physicians were assessed through 40 interviews held with physicians and managers. This pointed to a need to support physicians in becoming more proactive regarding their careers as well as in building awareness of proactive behaviors in order to craft their current work situation. Based on this, a training program was developed in line with their needs. A number of theoretical methods and practical applications were selected as the building blocks of the training. Next, participants were randomly assigned to either the waitlist-control group (ie, received no training) or the intervention group. The intervention group participated in a 4-hour training session and worked on four self-set goals. Then, a coaching conversation took place over the phone. Digital questionnaires distributed before and 8 weeks after the intervention assessed changes in job crafting, career self-management, employability, and changes in the following additional variables: job satisfaction, career satisfaction, work-home interference, work ability, and performance. In addition, a process evaluation was conducted to examine factors that may have promoted or hindered the effectiveness of the intervention. Results: Data collection was completed in March 2020. Evaluation of outcomes and the research process started in April 2020. Study results were submitted for publication in September 2020. Conclusions: This study protocol gives insight into the systematic development and design of a career crafting training intervention that is aimed to enhance job crafting, career self-management, and employability. This study will provide valuable information to physicians, managers, policy makers, and other researchers that aim to enhance career crafting