410 research outputs found
Experimental investigation of the radial structure of energetic particle driven modes
Alfv\'en eigenmodes (AEs) and energetic particle modes (EPMs) are often
excited by energetic particles (EPs) in tokamak plasmas. One of the main open
questions concerning EP driven instabilities is the non-linear evolution of the
mode structure. The aim of the present paper is to investigate the properties
of beta-induced AEs (BAEs) and EP driven geodesic acoustic modes (EGAMs)
observed in the ramp-up phase of off-axis NBI heated ASDEX Upgrade (AUG)
discharges. This paper focuses on the changes in the mode structure of
BAEs/EGAMs during the non-linear chirping phase. Our investigation has shown
that in case of the observed down-chirping BAEs the changes in the radial
structure are smaller than the uncertainty of our measurement. This behaviour
is most probably the consequence of that BAEs are normal modes, thus their
radial structure strongly depends on the background plasma parameters rather
than on the EP distribution. In the case of rapidly upward chirping EGAMs the
analysis consistently shows shrinkage of the mode structure. The proposed
explanation is that the resonance in the velocity space moves towards more
passing particles which have narrower orbit widths.Comment: submitted to Nuclear Fusio
Validity of models for Dreicer generation of runaway electrons in dynamic scenarios
Runaway electron modelling efforts are motivated by the risk these energetic
particles pose to large fusion devices. The sophisticated kinetic models can
capture most features of the runaway electron generation but have high
computational costs which can be avoided by using computationally cheaper
reduced kinetic codes. In this paper, we compare the reduced kinetic and
kinetic models to determine when the former solvers, based on analytical
calculations assuming quasi-stationarity, can be used. The Dreicer generation
rate is calculated by two different solvers in parallel in a workflow developed
in the European Integrated Modelling framework, and this is complemented by
calculations of a third code that is not yet integrated into the framework.
Runaway Fluid, a reduced kinetic code, NORSE, a kinetic code using non-linear
collision operator, and DREAM, a linearized Fokker-Planck solver, are used to
investigate the effect of a dynamic change in the electric field for different
plasma scenarios spanning across the whole tokamak-relevant range. We find that
on time scales shorter than or comparable to the electron collision time at the
critical velocity for runaway electron generation kinetic effects not captured
by reduced kinetic models play an important role. This characteristic time
scale is easy to calculate and can reliably be used to determine whether there
is a need for kinetic modelling, or cheaper reduced kinetic codes are expected
to deliver sufficiently accurate results. This criterion can be automated, and
thus it can be of great benefit for the comprehensive self-consistent modelling
frameworks that are attempting to simulate complex events such as tokamak
start-up or disruptions
Revision of the genus Tapholeon Wells, 1967 (Copepoda, Harpacticoida, Laophontidae)
To date, only two species are known in the laophontid genus Tapholeon Wells, 1967 (Copepoda, Harpacticoida). In the present contribution, a redescription of the type species T. ornatus Wells, 1967, based on the type material, is provided. Furthermore, two new species are described from the coast of Kenya, T. inconspicuus sp. nov. and T. tenuis sp. nov. Two species, formerly attributed to Asellopsis Brady and Robertson, 1873 (namely A. arenicola Chappuis, 1954 and A. chappuisius Krishnaswamy, 1957), are allocated to Tapholeon based on the absence of sexual dimorphism in the swimming legs P2-P4. The former of the two species is redescribed based on additional material from the Comoros. An updated generic diagnosis and a key to the six species of Tapholeon are included
Review of high-contrast imaging systems for current and future ground- and space-based telescopes I. Coronagraph design methods and optical performance metrics
The Optimal Optical Coronagraph (OOC) Workshop at the Lorentz Center in
September 2017 in Leiden, the Netherlands gathered a diverse group of 25
researchers working on exoplanet instrumentation to stimulate the emergence and
sharing of new ideas. In this first installment of a series of three papers
summarizing the outcomes of the OOC workshop, we present an overview of design
methods and optical performance metrics developed for coronagraph instruments.
The design and optimization of coronagraphs for future telescopes has
progressed rapidly over the past several years in the context of space mission
studies for Exo-C, WFIRST, HabEx, and LUVOIR as well as ground-based
telescopes. Design tools have been developed at several institutions to
optimize a variety of coronagraph mask types. We aim to give a broad overview
of the approaches used, examples of their utility, and provide the optimization
tools to the community. Though it is clear that the basic function of
coronagraphs is to suppress starlight while maintaining light from off-axis
sources, our community lacks a general set of standard performance metrics that
apply to both detecting and characterizing exoplanets. The attendees of the OOC
workshop agreed that it would benefit our community to clearly define
quantities for comparing the performance of coronagraph designs and systems.
Therefore, we also present a set of metrics that may be applied to theoretical
designs, testbeds, and deployed instruments. We show how these quantities may
be used to easily relate the basic properties of the optical instrument to the
detection significance of the given point source in the presence of realistic
noise.Comment: To appear in Proceedings of the SPIE, vol. 1069
Spatiotemporal analysis of the runaway distribution function from synchrotron images in an ASDEX Upgrade disruption
Synchrotron radiation images from runaway electrons (REs) in an ASDEX Upgrade discharge disrupted by argon injection are analysed using the synchrotron diagnostic tool Soft and coupled fluid-kinetic simulations. We show that the evolution of the runaway distribution is well described by an initial hot-tail seed population, which is accelerated to energies between 25-50 MeV during the current quench, together with an avalanche runaway tail which has an exponentially decreasing energy spectrum. We find that, although the avalanche component carries the vast majority of the current, it is the high-energy seed remnant that dominates synchrotron emission. With insights from the fluid-kinetic simulations, an analytic model for the evolution of the runaway seed component is developed and used to reconstruct the radial density profile of the RE beam. The analysis shows that the observed change of the synchrotron pattern from circular to crescent shape is caused by a rapid redistribution of the radial profile of the runaway density
Major basic protein, but not eosinophil cationic protein or eosinophil protein X, is related to atopy in cystic fibrosis
Identification key for fishes from coastal streams of the Atlantic forest of southeastern Brazil
Self-Reported Serious Illnesses in Rural Cambodia: A Cross-Sectional Survey
BACKGROUND: There is substantial evidence that ill-health is a major cause of impoverishment in developing countries. Major illnesses can have a serious economic impact on poor households through treatment costs and income loss. However, available methods for measuring the impact of ill-health on household welfare display several shortcomings and new methods are thus needed. To understand the potential complex impact of major illnesses on household livelihoods, a study on poverty and illness was conducted in rural Cambodia, as part of an international comparative research project. A cross-sectional survey was performed to identify households affected by major illness for further in-depth interviews. METHODOLOGY AND PRINCIPAL FINDINGS: 5,975 households in three rural health districts were randomly selected through a two-stage cluster sampling and interviewed. 27% of the households reported at least one member with a serious illness in the year preceding the survey and 15% of the household members reported suffering from at least one serious illness. The most reported conditions include common tropical infectious diseases, chronic diseases (notably hypertension and heart diseases) and road traffic accidents. Such conditions were particularly concentrated among the poor, children under five, women, and the elderly. Poor women often reported complications related to pregnancy and delivery as serious illnesses. CONCLUSIONS AND SIGNIFICANCE: Despite some methodological limitations, this study provides new information on the frequency of self-reported serious illnesses among the rural Cambodia's population, which serves as a basis for further in-depth investigation on 'major illnesses' and their economic consequences on poor households. This can in turn help policy makers to formulate appropriate interventions to protect the poor from the financial burden associated with ill-health. Our findings suggest that every year a considerable proportion of rural population in Cambodia, especially the poor and vulnerable, are affected by serious illnesses, both communicable and non-communicable diseases
Adherence to and appropriateness of anti-osteoporotic treatments in patients aged 50 and over in the Valencia Region (Spain). The ESOSVAL-AD Study
<p>Summary</p> <p>Background</p> <p>A study to evaluate the adherence to and appropriateness of anti-osteoporotic treatments in a cohort of men and women aged 50 and over participating in the ESOSVAL-R study.</p> <p>Methods/Design</p> <p><it>Design</it>: An observational, longitudinal, prospective cohort study; Study subjects: Men and women aged 50 and over living in the Valencia Region (Spain) who initiated treatment between June 15, 2009, and June 15, 2011, in primary healthcare centers with electronic medical records; <it>Data sources</it>: The main data source will be electronic medical records. <it>Measurement of results: </it>Degree of compliance with and persistence of anti-osteoporotic treatments, and the proportion of patients with appropriate anti-osteoporotic treatment in accordance with the most relevant and high impact recommendations with clearly defined treatment algorithms in Spain (the Spanish National Health System guide (2010), the General Practitioners' Society (2007) and the General Directorate for Pharmacy and Medical Products of Madrid (2007)), and with the National Osteoporosis Foundation (NOF, 2010), and the International Osteoporosis Foundation guidelines (IOF, 2008); <it>Analysis</it>: 1.) Descriptive analysis of patients undergoing treatment and the treatments prescribed; 2.) Descriptive analysis of compliance with and persistence of anti-osteoporotic treatments; 3.) Analysis of factors associated with compliance with and persistence of treatments by Cox proportional hazard regression models, 4.) Descriptive analysis of appropriateness of treatment; 5.) Analysis of factors associated with the appropriateness of treatment by multilevel models (4 levels: patient, doctor, Basic Healthcare Zone/Primary Healthcare Center, and Health Area variables).</p> <p>Discussion</p> <p>ESOSVAL-AD will provide information regarding adherence to osteoporosis treatments and the factors associated with a higher or lower adherence (including the appropriateness of the treatment) in the Spanish context. A better understanding of this phenomenon and the interventions needed to address it would contribute to the increased effectiveness of therapeutic measures, a reduction in morbidity and mortality, and a corresponding reduction in healthcare costs.</p
- âŠ