Magnetic Field Generation in Stars

Enormous progress has been made on observing stellar magnetism in stars from the main sequence through to compact objects. Recent data have thrown into sharper relief the vexed question of the origin of stellar magnetic fields, which remains one of the main unanswered questions in astrophysics. In this chapter we review recent work in this area of research. In particular, we look at the fossil field hypothesis which links magnetism in compact stars to magnetism in main sequence and pre-main sequence stars and we consider why its feasibility has now been questioned particularly in the context of highly magnetic white dwarfs. We also review the fossil versus dynamo debate in the context of neutron stars and the roles played by key physical processes such as buoyancy, helicity, and superfluid turbulence,in the generation and stability of neutron star fields. Independent information on the internal magnetic field of neutron stars will come from future gravitational wave detections. Thus we maybe at the dawn of a new era of exciting discoveries in compact star magnetism driven by the opening of a new, non-electromagnetic observational window. We also review recent advances in the theory and computation of magnetohydrodynamic turbulence as it applies to stellar magnetism and dynamo theory. These advances offer insight into the action of stellar dynamos as well as processes whichcontrol the diffusive magnetic flux transport in stars.Comment: 41 pages, 7 figures. Invited review chapter on on magnetic field generation in stars to appear in Space Science Reviews, Springe

Gene-environment interactions, stress, and depression

Depression is one of the most prevalent disorders worldwide, with high comorbidity with cardiovascular disease (CVD). Despite significant heritability, robust genetic associations are yet to be identified in depression. Multiple factors are accountable for this, including that genetic studies have not widely considered environmental factors, despite their established association with depression. One such factor is stress, a robust risk factor for depression; many genetic studies have failed to include nurture in their research into depression. The first gene-environment interaction (GxE) study in depression was published in 2003, reporting a significant interaction between a functional polymorphism in the serotonin transporter gene (5-HTTLPR) and recent stressors to predict depression. Many studies aimed to replicate this finding, as well as investigate other candidate genes (i.e., CRHR1, GR, FKBP5, BDNF). Initially, findings appeared not to reach a clear consensus; however, a closer analysis of the literature has shown that there are consistencies when specific methodological aspects are considered (i.e., timing of stressors). While there are some exciting and strongly evidenced findings, GxE research continues to face some significant challenges. This includes recognition of the importance of subtle method differences and also sample size. Samples are relatively small due to the time required to ascertain high-quality environmental data relative to standard genetic association studies, compromising power. Ascertaining large samples must therefore be made a priority in GxE research to enable further discoveries. GxE studies in depression have the potential to inform disease mechanisms that may be relevant to CVD, informing future CVD-depression research.Sarah Cohen-Woods and Kaitlin Nicole Harkes

Extended burnup demonstration reactor fuel program. Semi-annual progress report, January 1979-September 1979

This is the first semi-annual progress report for the DOE-sponsored Extended Burnup Demonstration program. The program objectives, description, and organization are detailed. Characteristics are given for the 64 Big Rock Point fuel rods and the four 8 x 8 Oyster Creek fuel assemblies which will be driven to extended burnup. The transfer of 64 Big Rock Point fuel rods from their original assemblies into host assemblies and the results of the fuel examination of these rods are described

The Influence of Chain Dynamics on theFar-Infrared Spectrum of Liquid Methanol

Far-infrared absorption spectroscopy is used to investigate the low frequency ({center_dot} 100 cm{sup -1}) intermolecular interactions in liquid methanol. Using an intense source of far-infrared radiation, modes are elucidated at approximately 30 cm{sup -1} and 70 cm{sup -1} in the absorption spectrum. These modes are believed to arise from intermolecular bending and librational motions respectively and are successfully reproduced in an ab initio molecular dynamics simulation of methanol

The Influence of Chain Dynamics on the Far Infrared Spectrum of Liquid Methanol-Water Mixtures

Far-infrared absorption spectroscopy has been used to study the low frequency ({center_dot} 100 cm{sup -1}) intermolecular modes of methanol in mixtures with water. With the aid of a first principles molecular dynamics simulation on an equivalent system, a detailed understanding about the origin of the low frequency IR modes has been established. The total dipole spectrum from the simulation suggests that the bands appearing in the experimental spectra at approximately 55 cm{sup -1} and 70 cm{sup -1} in methanol and methanol-rich mixtures arise from both fluctuations and torsional motions occurring within the methanol hydrogen-bonded chains. The influence of these modes on both the solvation dynamics and the relaxation mechanisms in the liquid are discussed within the context of recent experimental and theoretical results that have emerged from studies focusing on the short time dynamics in the methanol hydrogen bond network

A molecular time-scale for eukaryote evolution recalibrated with the continuous microfossil record

Recent attempts to establish a molecular time-scale of eukaryote evolution failed to provide a congruent view on the timing of the origin and early diversification of eukaryotes. The major discrepancies in molecular time estimates are related to questions concerning the calibration of the tree. To limit these uncertainties, we used here as a source of calibration points the rich and continuous microfossil record of dinoflagellates, diatoms and coccolithophorids. We calibrated a small-subunit ribosomal RNA tree of eukaryotes with four maximum and 22 minimum time constraints. Using these multiple calibration points in a Bayesian relaxed molecular clock framework, we inferred that the early radiation of eukaryotes occurred near the Mesoproterozoic–Neoproterozoic boundary, about 1100 million years ago. Our results indicate that most Proterozoic fossils of possible eukaryotic origin cannot be confidently assigned to extant lineages and should therefore not be used as calibration points in molecular dating