1,924 research outputs found
Selenium in biology: Facts and medical perspectives
Several decades after the discovery of setenium as an essential trace element in vertebrates approximately 20 eukaryotic and more than 15 prokaryotic selenoproteins containing the 21(st) proteinogenic amino acid, selenocysteine, have been identified, partially characterized or cloned from several species. Many of these proteins are involved in redox reactions with selenocysteine acting as an essential component of the catalytic cycle. Enzyme activities have been assigned to the glutathione peroxidase family, to the thioredoxin reductases, which were recently identified as selenoproteins, to the iodothyronine deiodinases, which metabolize thyroid hormones, and to the selenophosphate synthetase 2, which is involved in selenoprotein biosynthesis. Prokaryotic selenoproteins catalyze redox reactions and formation of selenoethers in (stress-induced) metabolism and energy production of E. coli, of the clostridial cluster XI and of other prokaryotes. Apart from the specific and complex biosynthesis of selenocysteine, selenium also reversibly binds to proteins, is incorporated into selenomethionine in bacteria, yeast and higher plants, or posttranslationally modifies a catalytically essential cysteine residue of CO dehydrogenase. Expression of individual eukaryotic selenoproteins exhibits high tissue specificity, depends on selenium availability, in some cases is regulated by hormones, and if impaired contributes to several pathological conditions. Disturbance of selenoprotein expression or function is associated with deficiency syndromes (Keshan and Kashin-Beck disease), might contribute to tumorigenesis and atherosclerosis, is altered in several bacterial and viral infections, and leads to infertility in male rodents
Early specific cognitive-behavioural psychotherapy in subjects at high risk for bipolar disorders: study protocol for a randomised controlled trial
Background: Bipolar disorders (BD) are among the most severe mental disorders with first clinical signs and symptoms frequently appearing in adolescence and early adulthood. The long latency in clinical diagnosis (and subsequent adequate treatment) adversely affects the course of disease, effectiveness of interventions and health-related quality of life, and increases the economic burden of BD. Despite uncertainties about risk constellations and symptomatology in the early stages of potentially developing BD, many adolescents and young adults seek help, and most of them suffer substantially from symptoms already leading to impairments in psychosocial functioning in school, training, at work and in their social relationships. We aimed to identify subjects at risk of developing BD and investigate the efficacy and safety of early specific cognitive-behavioural psychotherapy (CBT) in this subpopulation. Methods/Design: EarlyCBT is a randomised controlled multi-centre clinical trial to evaluate the efficacy and safety of early specific CBT, including stress management and problem solving strategies, with elements of mindfulness-based therapy (MBT) versus unstructured group meetings for 14 weeks each and follow-up until week 78. Participants are recruited at seven university hospitals throughout Germany, which provide in-and outpatient care (including early recognition centres) for psychiatric patients. Subjects at high risk must be 15 to 30 years old and meet the combination of specified affective symptomatology, reduction of psychosocial functioning, and family history for (schizo) affective disorders. Primary efficacy endpoints are differences in psychosocial functioning and defined affective symptomatology at 14 weeks between groups. Secondary endpoints include the above mentioned endpoints at 7, 24, 52 and 78 weeks and the change within groups compared to baseline; perception of, reaction to and coping with stress; and conversion to full BD. Discussion: To our knowledge, this is the first study to evaluate early specific CBT in subjects at high risk for BD. Structured diagnostic interviews are used to map the risk status and development of disease. With our study, the level of evidence for the treatment of those young patients will be significantly raised
Gold nanoparticles electrodeposited on glassy carbon using cyclic voltammetry: Application to Hg(II) trace analysis
The electrochemical determination of Hg(II) at trace level using gold nanoparticlesâmodified glassy carbon (AuNPsâGC) electrodes is described. Starting from HAuCl4 in NaNO3, gold nanoparticles (AuNPs) were deposited onto Glassy Carbon (GC) electrodes using Cyclic Voltammetry (CV). Different deposits were obtained by varying the global charge consumed during the whole electroreduction step, depending on the number of cyclic potential scans (N). AuNPs were characterized as a function of the charge using both CV in H2SO4 and Field Emission Gun Scanning Electron Microscopy (FEG-SEM). The AuNPsâGC electrodes were then applied to determine low Hg(II) concentrations using Square Wave Anodic Stripping Voltammetry (SWASV). The AuNPsâGC electrodes provided significantly improved performances in Hg(II) determination compared to unmodified GC and bare Au electrodes. It was shown that the physico-chemical properties of the deposits are correlated to the performances of the AuNPsâGC electrode with respect to Hg(II) assay. The best results were obtained for four electrodeposition cyclic scans, where small-sized particles (36 ± 13 nm) with high density (73 particles ÎŒm-ÂČ) were obtained. Under these conditions, a linearity range from 0.64 to 4.00 nM and a limit of detection of 0.42 nM were obtained
Natural living â a precondition for animal welfare in organic farming
Results from a four year interdisciplinary project are presented. Animal welfare is discussed in relation to values and aims in organic farming. Based on analyzes of organic standards and other publications from the organic movement, basic âorganic valuesâ were defined. In addition, two studies of Swedish organic livestock farmers (one quantitative and one qualitative) were made. Ecocentric ethics was then identified as an ethical position for organic farming. The overall concern in organic farming is to develop sustainable farming systems, although animal welfare is also important. These aims are partly contrary, causing some difficult dilemmas related to animal welfare. The actual welfare situation in organic animal husbandry was scrutinized through a literature study. The criticism regarding bad welfare in organic farming could not be confirmed, although parasitic diseases appear to be a problem. An important finding is that animal welfare is understood differently from what is usual in conventional agriculture. It is interpreted in terms of natural living, which includes the possibility to perform a natural behavior, feed adapted to animal physiology and a natural environment. Problems in organic production should be solved with this in mind
Testing fluvial erosion models using the transient response of bedrock rivers to tectonic forcing in the Apennines, Italy
The transient response of bedrock rivers to a drop in base level can be used to
discriminate between competing fluvial erosion models. However, some recent studies of
bedrock erosion conclude that transient river long profiles can be approximately
characterized by a transportâlimited erosion model, while other authors suggest that a
detachmentâlimited model best explains their field data. The difference is thought to be
due to the relative volume of sediment being fluxed through the fluvial system. Using a
pragmatic approach, we address this debate by testing the ability of endâmember fluvial
erosion models to reproduce the wellâdocumented evolution of three catchments in the
central Apennines (Italy) which have been perturbed to various extents by an
independently constrained increase in relative uplift rate. The transportâlimited model is
unable to account for the catchmentsâresponse to the increase in uplift rate, consistent with
the observed low rates of sediment supply to the channels. Instead, a detachmentâlimited
model with a threshold corresponding to the fieldâderived median grain size of the
sediment plus a slopeâdependent channel width satisfactorily reproduces the overall
convex long profiles along the studied rivers. Importantly, we find that the prefactor in the
hydraulic scaling relationship is uplift dependent, leading to landscapes responding faster
the higher the uplift rate, consistent with field observations. We conclude that a slopeâ
dependent channel width and an entrainment/erosion threshold are necessary ingredients
when modeling landscape evolution or mapping the distribution of fluvial erosion rates in
areas where the rate of sediment supply to channels is low
Widths of embeddings of 2-microlocal Besov spaces
We consider the asymptotic behaviour of the approximation, Gelfand and
Kolmogorov numbers of compact embeddings between 2-microlocal Besov spaces with
weights defined in terms of the distance to a -set .
The sharp estimates are shown in most cases, where the quasi-Banach setting is
included.Comment: 28 page
Limits to scale invariance in alluvial rivers
Assumptions about fluvial processes and processâform relations are made in general models and in many siteâspecific applications. Many standard assumptions about reachâscale flow resistance, bedâmaterial entrainment thresholds and transport rates, and downstream hydraulic geometry involve one or other of two types of scale invariance: a parameter (e.g. critical Shields number) has the same value in all rivers, or doubling one variable causes a fixed proportional change in another variable in all circumstances (e.g. powerâlaw hydraulic geometry). However, rivers vary greatly in size, gradient, and bed material, and many geomorphologists regard particular types of river as distinctive. This review examines the tension between universal scaling assumptions and perceived distinctions between different types of river. It identifies limits to scale invariance and departures from simple scaling, and illustrates them using large data sets spanning a wide range of conditions. Scaling considerations and data analysis support the commonly made distinction between coarseâbed and fineâbed reaches, whose different transport regimes can be traced to the different settlingâvelocity scalings for coarse and fine grains. They also help identify two endâmember subâtypes: steep shallow coarseâbed âtorrentsâ with distinctive flowâresistance scaling and increased entrainment threshold, and very large, lowâgradient âmega riversâ with predominantly suspended load, subdued secondary circulation, and extensive backwater conditions
Unity Through Diversity: A Case Study of Chrislam in Lagos
This article presents an ethnographic case study of Chrislam, a series of religious movements that fuse Christian and Muslim beliefs and practices, in its socio-cultural and political-economic setting in Nigeriaâs former capital Lagos. Against conventional approaches to study religious movements in Africa as syncretic forms of âAfrican Christianityâ or âAfrican Islamâ, I suggest that âsyncretismâ is a misleading appellation for Chrislam. In fact, Chrislam provides a rationale for scrutinizing the very concept of syncretism and offers an alternative analytical case for understanding its mode of religious pluralism. To account for the religious plurality in Chrislam, I employ assemblage theory as it proposes novel ways for looking at Chrislamâs religious mixing that are in line with how its worshippers perceive their religiosity. The underlying idea in Chrislamâs assemblage of Christianity and Islam is that to be a Christian or Muslim alone is not enough to guarantee success in this world and the hereafter and therefore Chrislam worshippers partake in Christian as well as Muslim practices, appropriating the perceived powers of both
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