876 research outputs found

    Retinal Ganglion Cells Can Rapidly Change Polarity from Off to On

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    Retinal ganglion cells are commonly classified as On-center or Off-center depending on whether they are excited predominantly by brightening or dimming within the receptive field. Here we report that many ganglion cells in the salamander retina can switch from one response type to the other, depending on stimulus events far from the receptive field. Specifically, a shift of the peripheral image—as produced by a rapid eye movement—causes a brief transition in visual sensitivity from Off-type to On-type for approximately 100 ms. We show that these ganglion cells receive inputs from both On and Off bipolar cells, and the Off inputs are normally dominant. The peripheral shift strongly modulates the strength of these two inputs in opposite directions, facilitating the On pathway and suppressing the Off pathway. Furthermore, we identify certain wide-field amacrine cells that contribute to this modulation. Depolarizing such an amacrine cell affects nearby ganglion cells in the same way as the peripheral image shift, facilitating the On inputs and suppressing the Off inputs. This study illustrates how inhibitory interneurons can rapidly gate the flow of information within a circuit, dramatically altering the behavior of the principal neurons in the course of a computation

    A century of fish growth in relation to climate change, population dynamics and exploitation

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    Marine ecosystems, particularly in high‐latitude regions such as the Arctic, have been significantly affected by human activities and contributions to climate change. Evaluating how fish populations responded to past changes in their environment is helpful for evaluating their future patterns, but is often hindered by the lack of long‐term biological data available. Using otolith increments of Northeast Arctic cod (Gadus morhua) as a proxy for individual growth, we developed a century‐scale biochronology (1924–2014) based on the measurements of 3,894 fish, which revealed significant variations in cod growth over the last 91 years. We combined mixed‐effect modeling and path analysis to relate these growth variations to selected climate, population and fishing‐related factors. Cod growth was negatively related to cod population size and positively related to capelin population size, one of the most important prey items. This suggests that density‐dependent effects are the main source of growth variability due to competition for resources and cannibalism. Growth was also positively correlated with warming sea temperatures but negatively correlated with the Atlantic Multidecadal Oscillation, suggesting contrasting effects of climate warming at different spatial scales. Fishing pressure had a significant but weak negative direct impact on growth. Additionally, path analysis revealed that the selected growth factors were interrelated. Capelin biomass was positively related to sea temperature and negatively influenced by herring biomass, while cod biomass was mainly driven by fishing mortality. Together, these results give a better understanding of how multiple interacting factors have shaped cod growth throughout a century, both directly and indirectly.publishedVersio

    Century-long cod otolith biochronology reveals individual growth plasticity in response to temperature

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    Otolith biochronologies combine growth records from individual fish to produce long-term growth sequences, which can help to disentangle individual from population-level responses to environmental variability. This study assessed individual thermal plasticity of Atlantic cod (Gadus morhua) growth in Icelandic waters based on measurements of otolith increments. We applied linear mixed-effects models and developed a century-long growth biochronology (1908-2014). We demonstrated interannual and cohort-specific changes in the growth of Icelandic cod over the last century which were mainly driven by temperature variation. Temperature had contrasting relationships with growth-positive for the fish during the youngest ages and negative during the oldest ages. We decomposed the effects of temperature on growth observed at the population level into within-individual effects and among-individual effects and detected significant individual variation in the thermal plasticity of growth. Variance in the individual plasticity differed across cohorts and may be related to the mean environmental conditions experienced by the group. Our results underscore the complexity of the relationships between climatic conditions and the growth of fish at both the population and individual level, and highlight the need to distinguish between average population responses and growth plasticity of the individuals for accurate growth predictions

    Стратегії та підходи до реструктуризації підприємств сфери ЖКГ в умовах реформування власності України

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    Наведено результати дослідження існуючих підходів до стратегічних напрямів реструктуризації підприємств сфери ЖКГ в умовах реформування власності. Ключові слова: стратегія реструктуризації, ЖКГ України, реструктуризація підприємства, антикризове управління, стратегічний менеджмент.Приведены результаты исследования существующих подходов в стратегических направлениях реструктуризации предприятий сферы ЖКГ в условиях реформирования собственности. Ключевые слова: стратегия реструктуризации, ЖКХ Украины, реструктуризация предприятия, антикризисное управление, стратегический менеджмент.The paper presents the results of studying the approaches in strategic directions of restructuring of housing and communal enterprises under property reformation in Ukraine. Keywords: strategy of restructuring, housing and communal facilities of Ukraine, restructuring of enterprise, anti-crisis management, strategic management

    Strong ellipticity and spectral properties of chiral bag boundary conditions

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    We prove strong ellipticity of chiral bag boundary conditions on even dimensional manifolds. From a knowledge of the heat kernel in an infinite cylinder, some basic properties of the zeta function are analyzed on cylindrical product manifolds of arbitrary even dimension.Comment: 16 pages, LaTeX, References adde

    Biochemical characterization of New Delhi metallo-beta-lactamase variants reveals differences in protein stability

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    Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.Rhodes Trust (UK); a Clarendon Scholarship; a St Hugh's College W. Louey Scholarship; the Biotechnology & Biological Sciences Research Council (BBSRC); a Royal Society Dorothy Hodgkin Research Fellowship; and the Medical Research Council (MRC)/Canadian Grant G1100135

    Treatment goals and changes over time in older patients with non-curable cancer

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    PURPOSE: To investigate the treatment goals of older patients with non-curable cancer, whether those goals changed over time, and if so, what triggered those changes. METHODS: We performed a descriptive and qualitative analysis using the Outcome Prioritization Tool (OPT) to assess patient goals across four conversations with general practitioners (GPs) over 6 months. Text entries from electronic patient records (hospital and general practice) were then analyzed qualitatively for this period. RESULTS: Of the 29 included patients, 10 (34%) rated extending life and 9 (31%) rated maintaining independence as their most important goals. Patients in the last year before death (late phase) prioritized extending life less often (3 patients; 21%) than those in the early phase (7 patients; 47%). Goals changed for 16 patients during follow-up (12 in the late phase). Qualitative analysis revealed three themes that explained the baseline OPT scores (prioritizing a specific goal, rating a goal as unimportant, and treatment choices related to goals). Another three themes related to changes in OPT scores (symptoms, disease course, and life events) and stability of OPT scores (stable situation, disease-unrelated motivation, and stability despite symptoms). CONCLUSION: Patients most often prioritized extending life as the most important goal. However, priorities differed in the late phase of the disease, leading to changed goals. Triggers for change related to both the disease (e.g., symptoms and course) and to other life events. We therefore recommend that goals should be discussed repeatedly, especially near the end of life. TRIAL REGISTRATION: OPTion study: NTR5419

    OPTIMIZING OUTCOMES IN CT IMAGING Priceless Clinical Pearls in the Performance of Cardiac CT

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    T he emergence of 64-slice CT scanners and associated software capable of complex 3-dimensional image reconstruction of coronary arteries has revolutionized our approach to patients with cardiovascular disease. Ultrafast CT coronary angiography (CTCA) is capable of providing diagnosticquality coronary images of soft noncalcified plaque and calcified plaque in the vast majority of patients evaluated with impressive sensitivity and specificity. With spatial resolution of 64-slice CT scanners as low as 0.4 mm, coupled with a positive predictive accuracy above 95% for the presence of coronary artery disease RICMS0002(GE)_03-14.qxd 3/14/08 3:25 PM Page S
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