537 research outputs found

    Variable sizes of Escherichia coli chemoreceptor signaling teams

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    Like many sensory receptors, bacterial chemotaxis receptors form clusters. In bacteria, large-scale clusters are subdivided into signaling teams that act as ‘antennas' allowing detection of ligands with remarkable sensitivity. The range of sensitivity is greatly extended by adaptation of receptors to changes in concentrations through covalent modification. However, surprisingly little is known about the sizes of receptor signaling teams. Here, we combine measurements of the signaling response, obtained from in vivo fluorescence resonance energy transfer, with the statistical method of principal component analysis, to quantify the size of signaling teams within the framework of the previously successful Monod–Wyman–Changeux model. We find that size of signaling teams increases 2- to 3-fold with receptor modification, indicating an additional, previously unrecognized level of adaptation of the chemotaxis network. This variation of signaling-team size shows that receptor cooperativity is dynamic and likely optimized for sensing noisy ligand concentrations

    The Psychological Society of South Africa’s guidelines for psychology professionals working with sexually and gender-diverse people: towards inclusive and affirmative practice

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    In this article, we outline the practice guidelines for psychology professionals working with sexually and gender-diverse people, ratified by the Psychological Society of South Africa’s Council in 2017. The guidelines are an augmentation of the Psychological Society of South Africa’s position statement of 2013 providing a framework for understanding the challenges that sexually and gender-diverse people face in patriarchal and hetero- and cis-normative societies. An affirmative stance towards sexual and gender diversity enables psychology practitioners to work ethically, effectively, and sensitively in this field. The guidelines – a first for Africa – are aspirational in nature and call on psychology professionals to become aware of their own biases, conscientise themselves of the best practices in the field by continued professional development, and to utilise the guidelines as a resource in their related work. Brief mention is made of the development process, before the rationale and possible applications of the 12 guidelines are explored.College of Human Science

    Effective String Theory Revisited

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    We revisit the effective field theory of long relativistic strings such as confining flux tubes in QCD. We derive the Polchinski-Strominger interaction by a calculation in static gauge. This interaction implies that a non-critical string which initially oscillates in one direction gets excited in orthogonal directions as well. In static gauge no additional term in the effective action is needed to obtain this effect. It results from a one-loop calculation using the Nambu-Goto action. Non-linearly realized Lorentz symmetry is manifest at all stages in dimensional regularization. We also explain that independent of the number of dimensions non-covariant counterterms have to be added to the action in the commonly used zeta-function regularization.Comment: 21 pages, 4 figures, v2: typo corrected, references added, published versio

    Consequences of converting graded to action potentials upon neural information coding and energy efficiency

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    Information is encoded in neural circuits using both graded and action potentials, converting between them within single neurons and successive processing layers. This conversion is accompanied by information loss and a drop in energy efficiency. We investigate the biophysical causes of this loss of information and efficiency by comparing spiking neuron models, containing stochastic voltage-gated Na+ and K+ channels, with generator potential and graded potential models lacking voltage-gated Na+ channels. We identify three causes of information loss in the generator potential that are the by-product of action potential generation: (1) the voltage-gated Na+ channels necessary for action potential generation increase intrinsic noise and (2) introduce non-linearities, and (3) the finite duration of the action potential creates a ‘footprint’ in the generator potential that obscures incoming signals. These three processes reduce information rates by ~50% in generator potentials, to ~3 times that of spike trains. Both generator potentials and graded potentials consume almost an order of magnitude less energy per second than spike trains. Because of the lower information rates of generator potentials they are substantially less energy efficient than graded potentials. However, both are an order of magnitude more efficient than spike trains due to the higher energy costs and low information content of spikes, emphasizing that there is a two-fold cost of converting analogue to digital; information loss and cost inflation

    The Role of Individual Variables, Organizational Variables and Moral Intensity Dimensions in Libyan Management Accountants’ Ethical Decision Making

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    This study investigates the association of a broad set of variables with the ethical decision making of management accountants in Libya. Adopting a cross-sectional methodology, a questionnaire including four different ethical scenarios was used to gather data from 229 participants. For each scenario, ethical decision making was examined in terms of the recognition, judgment and intention stages of Rest’s model. A significant relationship was found between ethical recognition and ethical judgment and also between ethical judgment and ethical intention, but ethical recognition did not significantly predict ethical intention—thus providing support for Rest’s model. Organizational variables, age and educational level yielded few significant results. The lack of significance for codes of ethics might reflect their relative lack of development in Libya, in which case Libyan companies should pay attention to their content and how they are supported, especially in the light of the under-development of the accounting profession in Libya. Few significant results were also found for gender, but where they were found, males showed more ethical characteristics than females. This unusual result reinforces the dangers of gender stereotyping in business. Personal moral philosophy and moral intensity dimensions were generally found to be significant predictors of the three stages of ethical decision making studied. One implication of this is to give more attention to ethics in accounting education, making the connections between accounting practice and (in Libya) Islam. Overall, this study not only adds to the available empirical evidence on factors affecting ethical decision making, notably examining three stages of Rest’s model, but also offers rare insights into the ethical views of practising management accountants and provides a benchmark for future studies of ethical decision making in Muslim majority countries and other parts of the developing world

    Rectal Transmission of Transmitted/Founder HIV-1 Is Efficiently Prevented by Topical 1% Tenofovir in BLT Humanized Mice

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    Rectal microbicides are being developed to prevent new HIV infections in both men and women. We focused our in vivo preclinical efficacy study on rectally-applied tenofovir. BLT humanized mice (n = 43) were rectally inoculated with either the primary isolate HIV-1(JRCSF) or the MSM-derived transmitted/founder (T/F) virus HIV-1(THRO) within 30 minutes following treatment with topical 1% tenofovir or vehicle. Under our experimental conditions, in the absence of drug treatment we observed 50% and 60% rectal transmission by HIV-1(JRCSF) and HIV-1(THRO), respectively. Topical tenofovir reduced rectal transmission to 8% (1/12; log rank p = 0.03) for HIV-1(JRCSF) and 0% (0/6; log rank p = 0.02) for HIV-1(THRO). This is the first demonstration that any human T/F HIV-1 rectally infects humanized mice and that transmission of the T/F virus can be efficiently blocked by rectally applied 1% tenofovir. These results obtained in BLT mice, along with recent ex vivo, Phase 1 trial and non-human primate reports, provide a critically important step forward in the development of tenofovir-based rectal microbicides

    AVALIAÇÃO DO CONTROLE POSTURAL E DA PRESSÃO PLANTAR EM PESSOAS COM ALTERAÇÃO VISUAL

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    O estudo objetivou avaliar o controle postural e a pressão plantar em pessoas com alteração visual, utilizando como referência o estrabismo. Participaram do estudo trinta e quatro voluntários, divididos em dois grupos: Grupo com Alteração Visual (GAV) com dezessete indivíduos com estrabismo e um Grupo Controle (GC) formado por dezessete indivíduos com visão normal. Todos os participantes foram submetidos às avaliações da pressão plantar e do equilíbrio através do exame da baropodometria computadorizada. Não houve diferença significativa na distribuição da pressão na região plantar entre os dois grupos. Na avaliação do equilíbrio, a velocidade média de oscilação e o deslocamento látero-lateral, com olhos abertos, apresentaram diferença estatística entre os grupos, bem como o deslocamento ântero-posterior, com olhos fechados. Conclui-se que não houve diferença estatisticamente significante na distribuição da pressão plantar ao comparar os dois grupos. Há alterações significativas no equilíbrio em indivíduos com alteração visual no deslocamento L/L e na velocidade média de oscilação, quando com os olhos abertos, no entanto existe uma correlação positiva em relação ao deslocamento A/P na condição olhos fechados, quando comparados com os indivíduos com visão normal
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