1,010 research outputs found

    Vitamin E and selenium: contrasting and interacting nutritional determinants of host resistance to parasitic and viral infections.

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    Beneficial effects of trace amounts of dietary Se were first observed in vitamin E-deficient rats so that a strong metabolic interaction between these two micronutrients was apparent since the initial discovery of the nutritional value of Se (Schwarz & Foltz, 1957). Later work showed that Se and vitamin E tended to spare one another's requirement for the prevention of certain nutritional deficiency diseases (e.g. exudative diathesis in chicks, see Thompson & Scott, 1969). However, there were other conditions that appeared to respond specifically to only one of these nutrients (e.g. resorption gestation in rats, see Harris et al. 1958). As our knowledge about Se and vitamin E grew, the complexity of their interactions became clear with some conditions being specific for one or the other nutrient, whereas other syndromes responded equally well to either nutrient (Table 1). Many of the early results could be adequately explained by the antioxidant properties of both these nutrients: Se as a component of the peroxide-destroying enzyme glutathione peroxidase (EC 1.11.1.9) and vitamin E as a lipid-soluble antioxidant (Hoekstra, 1975). More recent work has established metabolic roles for Se that appear to be unrelated to its antioxidant activity (e.g. as a component of iodothyronine 5’-deiodinase (EC 3.8.1.4), see Arthur et al. 1990)

    Cosmological Magnetogenesis driven by Radiation Pressure

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    The origin of large scale cosmological magnetic fields remains a mystery, despite the continuous efforts devoted to that problem. We present a new model of magnetic field generation, based on local charge separation provided by an anisotropic and inhomogeneous radiation pressure. In the cosmological context, the processes we explore take place at the epoch of the reionisation of the Universe. Under simple assumptions, we obtain results (i) in terms of the order of magnitude of the field generated at large scales and (ii) in terms of its power spectrum. The amplitudes obtained (B ~ 8.10^(-6) micro-Gauss) are considerably higher than those obtained in usual magnetogenesis models and provide suitable seeds for amplification by adiabatic collapse and/or dynamo during structure formation.Comment: 9 pages, 2 figure

    Stochastic Resonance in Ion Channels Characterized by Information Theory

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    We identify a unifying measure for stochastic resonance (SR) in voltage dependent ion channels which comprises periodic (conventional), aperiodic and nonstationary SR. Within a simplest setting, the gating dynamics is governed by two-state conductance fluctuations, which switch at random time points between two values. The corresponding continuous time point process is analyzed by virtue of information theory. In pursuing this goal we evaluate for our dynamics the tau-information, the mutual information and the rate of information gain. As a main result we find an analytical formula for the rate of information gain that solely involves the probability of the two channel states and their noise averaged rates. For small voltage signals it simplifies to a handy expression. Our findings are applied to study SR in a potassium channel. We find that SR occurs only when the closed state is predominantly dwelled. Upon increasing the probability for the open channel state the application of an extra dose of noise monotonically deteriorates the rate of information gain, i.e., no SR behavior occurs.Comment: 10 pages, 2 figures, to appear in Phys. Rev.

    Magnetic Fields in the Milky Way

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    This chapter presents a review of observational studies to determine the magnetic field in the Milky Way, both in the disk and in the halo, focused on recent developments and on magnetic fields in the diffuse interstellar medium. I discuss some terminology which is confusingly or inconsistently used and try to summarize current status of our knowledge on magnetic field configurations and strengths in the Milky Way. Although many open questions still exist, more and more conclusions can be drawn on the large-scale and small-scale components of the Galactic magnetic field. The chapter is concluded with a brief outlook to observational projects in the near future.Comment: 22 pages, 5 figures, to appear in "Magnetic Fields in Diffuse Media", eds. E.M. de Gouveia Dal Pino and A. Lazaria

    The Proton Spin and Flavor Structure in the Chiral Quark Model

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    After a pedagogical review of the simple constituent quark model and deep inelastic sum rules, we describe how a quark sea as produced by the emission of internal Goldstone bosons by the valence quarks can account for the observed features of proton spin and flavor structures. Some issues concerning the strange quark content of the nucleon are also discussed.Comment: 59 pages with table of contents, Lecture delivered at the Schladming Winter School (March 1997), to be published by Springer-Verlag under the title "Computing Particle Properties" (eds. C. B. Lang and H. Gausterer

    Consequences of temperature fluctuations in observables measured in high energy collisions

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    We review the consequences of intrinsic, nonstatistical temperature fluctuations as seen in observables measured in high energy collisions. We do this from the point of view of nonextensive statistics and Tsallis distributions. Particular attention is paid to multiplicity fluctuations as a first consequence of temperature fluctuations, to the equivalence of temperature and volume fluctuations, to the generalized thermodynamic fluctuations relations allowing us to compare fluctuations observed in different parts of phase space, and to the problem of the relation between Tsallis entropy and Tsallis distributions. We also discuss the possible influence of conservation laws on these distributions and provide some examples of how one can get them without considering temperature fluctuations.Comment: Revised version of the invited contribution to The European Physical Journal A (Hadrons and Nuclei) topical issue about 'Relativistic Hydro- and Thermodynamics in Nuclear Physics' guest eds. Tamas S. Biro, Gergely G. Barnafoldi and Peter Va

    Evaluating the feasibility of a nurse-led self-management support intervention for kidney transplant recipients: a pilot study

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    Background: To support effective self-management after kidney transplantation, a holistic nurse-led self-management support intervention was developed using the Intervention Mapping approach. The primary aim was to evaluate the feasibility, acceptability and fidelity of the intervention for kidney transplant recipients and professionals. The secondary aim was to explore preliminary effects on outcomes. Methods: A pilot study was conducted in 2015–2017 to evaluate the intervention. Nurse Practitioners (NP) guided recipients in assessing 14 life areas using the Self-Management Web. Participants were supported in developing selfregulation skills which can be applied to self-management of the illness. Strategies included goal setting, action planning, and promotion of motivation and self-efficacy. Adult recipients from an outpatient clinic of a Dutch University Hospital who underwent their transplant at least 1 month ago, were invited to participate. NPs, nephrologists and recipients were interviewed to assess feasibility, fidelity and implementation experience. Consultations were videoed and analysed to assess fidelity. To assess the preliminary effects, the intervention group completed baseline (T0) and follow-up (T1) questionnaires on self-management behavior, self-efficacy, quality of life and quality of care. A historical control group of kidney transplant recipients completed the same questionnaires at T1. Results: Twenty-seven recipients agreed to participate in the intervention group, of which 24 completed the intervention and 16 completed baseline and follow-up surveys. The control group consisted of 33 recipients. Professionals and recipients appraised the open, holistic focus of the intervention as a welcome addition to standard care and felt that this helped to build a relationship of trust. Recipients also felt they became more competent in problem-solving skills. The within-group analysis showed no significant increase in patients’ self-management skills. The between-groups analysis showed significantly higher medication adherence among the intervention group (P = 0.03; G = 0.81). The within-groups analysis showed a significantly higher perceived quality of care (P = 0.02) in the intervention group. Conclusion: This holistic nurse-led self-management support intervention was found to be feasible and acceptable by professionals and recipients alike. Thi

    A First Search for coincident Gravitational Waves and High Energy Neutrinos using LIGO, Virgo and ANTARES data from 2007

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    We present the results of the first search for gravitational wave bursts associated with high energy neutrinos. Together, these messengers could reveal new, hidden sources that are not observed by conventional photon astronomy, particularly at high energy. Our search uses neutrinos detected by the underwater neutrino telescope ANTARES in its 5 line configuration during the period January - September 2007, which coincided with the fifth and first science runs of LIGO and Virgo, respectively. The LIGO-Virgo data were analysed for candidate gravitational-wave signals coincident in time and direction with the neutrino events. No significant coincident events were observed. We place limits on the density of joint high energy neutrino - gravitational wave emission events in the local universe, and compare them with densities of merger and core-collapse events.Comment: 19 pages, 8 figures, science summary page at http://www.ligo.org/science/Publication-S5LV_ANTARES/index.php. Public access area to figures, tables at https://dcc.ligo.org/cgi-bin/DocDB/ShowDocument?docid=p120000
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