The g-modes of white dwarfs

The neutral g-modes of a degenerate fluid at zero temperature are analyzed. The g-modes of a degenerate fluid at finite but small temperatures are then expanded in terms of those of the zero temperature fluid. For nonrelativistic degenerate fluids it is found that (1) the g-eigenvalues are proportional to T mu(6)sub e mu(-1)sub i, where T is the internal temperature of the fluid, mu sub e and mu sub i are the mean molecular weights of electrons and ions, respectively; (2) the ion pressure is solely responsible for driving the g-modes. For white dwarfs of about a solar mass, the periods of the g-oscillations are in the range of a few hundredths of seconds

Micromegas TPC studies at high magnetic fields using the charge dispersion signal

The International Linear Collider (ILC) Time Projection Chamber (TPC) transverse space-point resolution goal is 100 microns for all tracks including stiff 90 degree tracks with the full 2 meter drift. A Micro Pattern Gas Detector (MPGD) readout TPC can achieve the target resolution with existing techniques using 1 mm or narrower pads at the expense of increased detector cost and complexity. The new MPGD readout technique of charge dispersion can achieve good resolution without resorting to narrow pads. This has been demonstrated previously for 2 mm x 6 mm pads with GEMs and Micromegas in cosmic ray tests and in a KEK beam test in a 1 Tesla magnet. We have recently tested a Micromegas-TPC using the charge dispersion readout concept in a high field super-conducting magnet at DESY. The measured Micromegas gain was found to be constant within 0.5% for magnetic fields up to 5 Tesla. With the strong suppression of transverse diffusion at high magnetic fields, we measure a flat 50 micron resolution at 5 Tesla over the full 15 cm drift length of our prototype TPC.Comment: 7 pages, 3 figure

Past alcohol consumption and incident atrial fibrillation: The Atherosclerosis Risk in Communities (ARIC) Study.

BackgroundAlthough current alcohol consumption is a risk factor for incident atrial fibrillation (AF), the more clinically relevant question may be whether alcohol cessation is associated with a reduced risk.Methods and resultsWe studied participants enrolled in the Atherosclerosis Risk in Communities Study (ARIC) between 1987 and 1989 without prevalent AF. Past and current alcohol consumption were ascertained at baseline and at 3 subsequent visits. Incident AF was ascertained via study ECGs, hospital discharge ICD-9 codes, and death certificates. Of 15,222 participants, 2,886 (19.0%) were former drinkers. During a median follow-up of 19.7 years, there were 1,631 cases of incident AF, 370 occurring in former consumers. Former drinkers had a higher rate of AF compared to lifetime abstainers and current drinkers. After adjustment for potential confounders, every decade abstinent from alcohol was associated with an approximate 20% (95% CI 11-28%) lower rate of incident AF; every additional decade of past alcohol consumption was associated with a 13% (95% CI 3-25%) higher rate of AF; and every additional drink per day during former drinking was associated with a 4% (95% CI 0-8%) higher rate of AF.ConclusionsAmong former drinkers, the number of years of drinking and the amount of alcohol consumed may each confer an increased risk of AF. Given that a longer duration of abstinence was associated with a decreased risk of AF, earlier modification of alcohol use may have a greater influence on AF prevention

RF amplification property of the MgO-based magnetic tunnel junction using field-induced ferromagnetic resonance

The radio-frequency (RF) voltage amplification property of a tunnel magnetoresistance device driven by an RF external-magnetic-field-induced ferromagnetic resonance was studied. The proposed device consists of a magnetic tunnel junction (MTJ) and an electrically isolated coplanar waveguide. The input RF voltage applied to the waveguide can excite the resonant dynamics in the free layer magnetization, leading to the generation of an output RF voltage under a DC bias current. The dependences of the RF voltage gain on the static external magnetic field strength and angle were systematically investigated. The design principles for the enhancement of the gain factor are also discussed.Comment: 12 pages, 3 figure

A mixed methodology, non-interventional study to evaluate the use of direct oral anticoagulants in UK clinical practice for patients with a first stroke associated with non-valvular atrial fibrillation: study protocol.

BACKGROUND: Treatment with anticoagulants, including direct oral anticoagulants (DOACs), should be considered for patients diagnosed with atrial fibrillation (AF) deemed at risk of ischaemic stroke. There are limited real world data related to the characteristics of patients with non-valvular AF who were not taking anticoagulants at the time of first ischaemic stroke and their subsequent DOAC treatment for the secondary prevention of stroke. Furthermore, little is known about patient adherence and experiences of DOAC treatment, especially for patients with non-valvular AF receiving DOAC therapy for the secondary prevention of stroke. METHODS: This is a UK mixed methodology, non-interventional study, involving retrospective and prospective medical record reviews and a prospective patient survey, in progress in six UK National Health Service secondary/tertiary care centres. The study comprises two groups of patients. Group 1 will include 300 eligible consenting patients with a first ischaemic stroke associated with non-valvular AF untreated with anticoagulants in the 12 months prior to stroke. Group 2 will include a subgroup of 150 patients from Group 1 initiated on one of the DOACs targeting activated Factor X (n = 50 on apixaban, n = 50 on edoxaban and n = 50 on rivaroxaban). The primary endpoint of the study is the CHA2DS2-VASc Risk Score prior to initiation of anticoagulation for patients included in Group 1. Secondary endpoints to be evaluated in Group 1 include patient demographics, clinical characteristics, relevant medical history, anticoagulant therapy initiated for secondary prevention of stroke, and relevant concomitant medication. Secondary endpoints to be evaluated in Group 2 include the time between stroke and DOAC initiation; prescribing of DOACs, other anticoagulants and concomitant medication; clinical assessments and hospital resource use; patient reported outcome measures, including the Morisky Medication Adherence Scale questionnaire and the Treatment Satisfaction Questionnaire for Medication. DISCUSSION: This mixed methodology study will provide new real world insights into the characteristics and management pathways and patient-reported experiences of this important group of patients. It is anticipated that the results of this study will provide the medical community and patients with important information to inform clinical decision-making and help facilitate meaningful improvements in the care of patients with non-valvular AF

Groundwater resilience Nepal: preliminary findings from a case study in the Middle Hills

Groundwater resources in the Middle Hills of Nepal perform a major role in supplying domestic and irrigation water and in regulating river flows. However, there has been little systematic study of groundwater within the region, making it difficult to evaluate how water supplies and river flows may change in response to climatic and anthropogenic change. To begin to build an evidence base, two catchments in the Middle Hills were investigated. The aim of the study was to characterise the hydrogeology of the catchments, assess water supplies and water usage and evaluate how resilient groundwater may be to change. Two contrasting sub-catchments within the Kali Gandaki River catchment were chosen: Ramche Village Development Committee (VDC), at an elevation of 2000 – 3000 m, with subsistence terraced farming and highly forested slopes, and Madanpokhara VDC which is largely below 1000 m, with expanding commercial agriculture. Groundwater sampling was undertaken during the post-monsoon season 2013 and pre-monsoon season 2014. Springs, tube wells and rivers across the two catchments were investigated using a combination of surveys, flow measurements, and sampling for inorganic chemistry, stable isotopes, groundwater residence time indicators (CFC and SF6) and noble gases. In addition, 12 months of weekly hydrological monitoring and monthly water usage surveys were undertaken at several sites. There is a heavy reliance on springs for water supply in Ramche. The springs are typically perennial but with significantly reduced flows during the winter and pre-monsoon season. The springs have bicarbonate groundwater chemistry and generally low overall mineralisation. Springs issuing from the higher slopes are reliant on seasonal monsoon rainfall and snow to sustain higher flows, but baseflows are sustained by groundwater storage within the weathered aquifer and will therefore have some inter-annual storage. Discrete springs issuing from lower slopes are most likely to be fed from groundwater storage within the fractured aquifer network. Groundwater residence time indicators (CFC and SF6) suggest a mean residence time of 10-20 years for pre-monsoon groundwater, implying inter-annual storage and therefore some built in resilience. However the general low storage of the groundwater environment suggests that none of the springs would be resilient to a long term reduction in precipitation. In the lower catchment of Madanpokhara where floodplain and outwash deposits are present, many hand-drilled shallow tubewells have been installed in the last 5-10 years, decreasing the reliance on springs. The development of groundwater resources has resulted in a thriving agricultural co-operative, inward migration and a growing population. These shallow tubewells have increased the resilience of the water supplies to change but are potentially vulnerable to over-exploitation as a result of the rapid increase in abstraction. Groundwater sampled in tubewells along the margin of the floodplain is modern (~20 yrs Mean Residence Time (MRT)) with bicarbonate groundwater chemistry and no significant water quality concerns. Groundwater sampled from tubewells towards the centre of the floodplain appears to be older (~50 yrs MRT) with elevated concentrations of iron, manganese, zinc and arsenic detected at some sites. With a growing recognition of the importance of groundwater storage in the Middle Hills there is significant potential to further advance the characterisation of groundwater systems and investigate the resilience of groundwater supplies to change. Systematic monitoring of groundwater, as springs flows, groundwater levels and chemistry would give a much better understanding of emerging trends. Likewise, monitoring current yields of springs and comparing to historic values at installation may allow some conclusions to be drawn about the trajectory of springflow. There are several groundwater-related initiatives underway within organisations in Nepal; the lessons learned from this current research, the methodologies used and the preliminary findings will be of value to these

Springs, storage and sensitivity to change : groundwater in Nepal's Middle Hills

The valleys in the foothills of the Himalayas may be some of the most sensitive areas to environmental and societal changes in Asia. Changes to the Asian monsoon and increasing temperatures could lead to variations in snow melt and runoff, and forecasts of increasingly inhospitable temperatures for lowland areas of Nepal and northern India (up to 60 oC) are already leading to migration to the cooler middle-hills. The use of groundwater within these catchments (from spring flows, tube wells and indirectly through baseflow) is vital for continued secure water supply for the growing populations and increased agricultural production. However groundwater resources in these valleys are poorly characterised and the resilience of water supplies dependant on these resources largely unknown

Microscopic description of light unstable nuclei with the stochastic variational method

The structure of the light proton and neutron rich nuclei is studied in a microscopic multicluster model using the stochastic variational method. This approach enables us to describe the weakly bound nature of these nuclei in a consistent way. Applications for various nuclei $^{6-9}$Li, $^7$Be, $^8$B, $^9$C, $^{9-10}$Be, $^{9-10}$B presented. The paper discusses the relation of this model to other models as well as the possible extension for p and sd shell nuclei.Comment: 11 pages, latex, no figures