7,029 research outputs found
Dusty plasma cavities: probe-induced and natural
A comprehensive exploration of regional dust evacuation in complex plasma
crystals is presented. Voids created in 3D crystals on the International Space
Station have provided a rich foundation for experiments, but cavities in dust
crystals formed in ground-based experiments have not received as much
attention. Inside a modified GEC RF cell, a powered vertical probe was used to
clear the central area of a dust crystal, producing a cavity with high
cylindrical symmetry. Cavities generated by three mechanisms are examined.
First, repulsion of micrometer-sized particles by a negatively charged probe is
investigated. A model of this effect developed for a DC plasma is modified and
applied to explain new experimental data in RF plasma. Second, the formation of
natural cavities is surveyed; a radial ion drag proposed to occur due to a
curved sheath is considered in conjunction with thermophoresis and a flattened
confinement potential above the center of the electrode. Finally, cavity
formation unexpectedly occurs upon increasing the probe potential above the
plasma floating potential. The cavities produced by these methods appear
similar, but each are shown to be facilitated by fundamentally different
processes.Comment: 10 pages, 12 figure
Detection of equine atypical myopathy-associated hypoglycin A in plant material: Optimisation and validation of a novel LC-MS based method without derivatisation
Hypoglycin A (HGA) toxicity, following ingestion of material from certain plants, is linked to an acquired multiple acyl-CoA dehydrogenase deficiency known as atypical myopathy, a commonly fatal form of equine rhabdomyolysis seen worldwide. Whilst some plants are known to contain this toxin, little is known about its function or the mechanisms that lead to varied HGA concentrations between plants. Consequently, reliable tools to detect this amino acid in plant samples are needed. Analytical methods for HGA detection have previously been validated for the food industry, however, these techniques rely on chemical derivatisation to obtain accurate results at low HGA concentrations. In this work, we describe and validate a novel method, without need for chemical derivatisation (accuracy = 84–94%; precision = 3–16%; reproducibility = 3–6%; mean linear range R2 = 0.999). The current limit of quantitation for HGA in plant material was halved (from 1μg/g in previous studies) to 0.5μg/g. The method was tested in Acer pseudoplatanus material and other tree and plant species. We confirm that A. pseudoplatanus is most likely the only source of HGA in trees found within European pastures
A study of intense magnetic fields for high energy forming and structural assembly Interim report
Determination of maximum force on static sheet of aluminum subjected to magnetic field of hammer coi
The interferon-stimulated gene IFITM3 restricts infection and pathogenesis of arthritogenic and encephalitic alphaviruses
Host cells respond to viral infections by producing type I interferon (IFN), which induces the expression of hundreds of interferon-stimulated genes (ISGs). Although ISGs mediate a protective state against many pathogens, the antiviral functions of the majority of these genes have not been identified. IFITM3 is a small transmembrane ISG that restricts a broad range of viruses, including orthomyxoviruses, flaviviruses, filoviruses, and coronaviruses. Here, we show that alphavirus infection is increased in Ifitm3(−/−) and Ifitm locus deletion (Ifitm-del) fibroblasts and, reciprocally, reduced in fibroblasts transcomplemented with Ifitm3. Mechanistic studies showed that Ifitm3 did not affect viral binding or entry but inhibited pH-dependent fusion. In a murine model of chikungunya virus arthritis, Ifitm3(−/−) mice sustained greater joint swelling in the ipsilateral ankle at days 3 and 7 postinfection, and this correlated with higher levels of proinflammatory cytokines and viral burden. Flow cytometric analysis suggested that Ifitm3(−/−) macrophages from the spleen were infected at greater levels than observed in wild-type (WT) mice, results that were supported by experiments with Ifitm3(−/−) bone marrow-derived macrophages. Ifitm3(−/−) mice also were more susceptible than WT mice to lethal alphavirus infection with Venezuelan equine encephalitis virus, and this was associated with greater viral burden in multiple organs. Collectively, our data define an antiviral role for Ifitm3 in restricting infection of multiple alphaviruses. IMPORTANCE The interferon-induced transmembrane protein 3 (IFITM3) inhibits infection of multiple families of viruses in cell culture. Compared to other viruses, much less is known about the antiviral effect of IFITM3 on alphaviruses. In this study, we characterized the antiviral activity of mouse Ifitm3 against arthritogenic and encephalitic alphaviruses using cells and animals with a targeted gene deletion of Ifitm3 as well as deficient cells transcomplemented with Ifitm3. Based on extensive virological analysis, we demonstrate greater levels of alphavirus infection and disease pathogenesis when Ifitm3 expression is absent. Our data establish an inhibitory role for Ifitm3 in controlling infection of alphaviruses
Conformational transformations induced by the charge-curvature interaction at finite temperature
The role of thermal fluctuations on the conformational dynamics of a single
closed filament is studied. It is shown that, due to the interaction between
charges and bending degrees of freedom, initially circular aggregates may
undergo transformation to polygonal shape. The transition occurs both in the
case of hardening and softening charge-bending interaction. In the former case
the charge and curvature are smoothly distributed along the chain while in the
latter spontaneous kink formation is initiated. The transition to a
non-circular conformation is analogous to the phase transition of the second
kind.Comment: 23 pages (Latex), 10 figures (Postscript), 2 biblio file (bib-file
and bbl-file
Use of small specimen creep data in component life management: a review
Small specimen creep testing techniques are novel mechanical test techniques that have been developed over the past 25 years. They mainly include the sub-size uniaxial test, the small punch creep test, the impression creep test, the small ring creep test and the two-bar creep test. This paper outlines the current methods in practice for data interpretation as well as the state-of-the-art procedures for conducting the tests. Case studies for the use of impression creep testing and material strength ranking of creep resistant steels are reviewed along with the requirement for the standardisation of the impression creep test method. A database of small specimen creep testing is required to prove the validity of the tests
Clinical assessors' working conceptualisations of undergraduate consultation skills: a framework analysis of how assessors make expert judgements in practice.
Undergraduate clinical assessors make expert, multifaceted judgements of consultation skills in concert with medical school OSCE grading rubrics. Assessors are not cognitive machines: their judgements are made in the light of prior experience and social interactions with students. It is important to understand assessors' working conceptualisations of consultation skills and whether they could be used to develop assessment tools for undergraduate assessment. To identify any working conceptualisations that assessors use while assessing undergraduate medical students' consultation skills and develop assessment tools based on assessors' working conceptualisations and natural language for undergraduate consultation skills. In semi-structured interviews, 12 experienced assessors from a UK medical school populated a blank assessment scale with personally meaningful descriptors while describing how they made judgements of students' consultation skills (at exit standard). A two-step iterative thematic framework analysis was performed drawing on constructionism and interactionism. Five domains were found within working conceptualisations of consultation skills: Application of knowledge; Manner with patients; Getting it done; Safety; and Overall impression. Three mechanisms of judgement about student behaviour were identified: observations, inferences and feelings. Assessment tools drawing on participants' conceptualisations and natural language were generated, including 'grade descriptors' for common conceptualisations in each domain by mechanism of judgement and matched to grading rubrics of Fail, Borderline, Pass, Very good. Utilising working conceptualisations to develop assessment tools is feasible and potentially useful. Work is needed to test impact on assessment quality
Dispersion Relations for Thermally Excited Waves in Plasma Crystals
Thermally excited waves in a Plasma crystal were numerically simulated using
a Box_Tree code. The code is a Barnes_Hut tree code proven effective in
modeling systems composed of large numbers of particles. Interaction between
individual particles was assumed to conform to a Yukawa potential. Particle
charge, mass, density, Debye length and output data intervals are all
adjustable parameters in the code. Employing a Fourier transform on the output
data, dispersion relations for both longitudinal and transverse wave modes were
determined. These were compared with the dispersion relations obtained from
experiment as well as a theory based on a harmonic approximation to the
potential. They were found to agree over a range of 0.9<k<5, where k is the
shielding parameter, defined by the ratio between interparticle distance a and
dust Debye length lD. This is an improvement over experimental data as current
experiments can only verify the theory up to k = 1.5.Comment: 8 pages, Presented at COSPAR '0
Explorer 12 magnetometer records, 16 August - 6 December 1961
Explorer XII magnetometer record
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