270 research outputs found

    Restricted diffusion of calretinin in cerebellar granule cell dendrites implies Ca²⁺-dependent interactions via its EF-hand 5 domain

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    Ca²⁺-binding proteins (CaBPs) are important regulators of neuronal Ca²⁺ signaling, acting either as buffers that shape Ca²⁺ transients and Ca²⁺ diffusion and/or as Ca²⁺ sensors. The diffusional mobility represents a crucial functional parameter of CaBPs, describing their range-of-action and possible interactions with binding partners. Calretinin (CR) is a CaBP widely expressed in the nervous system with strong expression in cerebellar granule cells. It is involved in regulating excitability and synaptic transmission of granule cells, and its absence leads to impaired motor control. We quantified the diffusional mobility of dye-labelled CR in mouse granule cells using two-photon fluorescence recovery after photobleaching (FRAP). We found that movement of macromolecules in granule cell dendrites was not well described by free Brownian diffusion and that CR diffused unexpectedly slow compared to fluorescein dextrans of comparable size. During bursts of action potentials, which were associated with dendritic Ca²⁺ transients, the mobility of CR was further reduced. Diffusion was significantly accelerated by a peptide embracing EF-hand 5 of CR. Our results suggest long-lasting, Ca²⁺-dependent interactions of CR with large and/or immobile binding partners. These interactions render CR a poorly mobile Ca²⁺ buffer and point towards a Ca²⁺ sensor function of CR

    Zehn Meilensteine für eine nachhaltige Bioenergiestrategie in Deutschland

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    Die Transformation des Energiesystems von fossilen zu erneuerbaren Energieträgern ist ein erklärtes politisches Ziel. Aus dieser Absichtserklärungergibt sich die Frage der konkreten Umsetzung. Welche Rolle kann dabei die Bioenergie übernehmen

    Formation and Evolution of Dust in Type IIb Supernova with Application to the Cassiopeia A Supernova Remnant

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    We investigate the formation of dust grains in the ejecta of a SN IIb and their evolution in the shocked gas in the SNR by considering the uniform and power-law density structures for the CSM. Based on these calculations, we also simulate the time evolution of thermal emission from the shock-heated dust in the SNR and compare the results with the observations of Cas A SNR. We find that the total mass of dust formed in the SN IIb is as large as 0.167 M_sun but the average radius of dust is smaller than 0.01 mum and is significantly different from those in SNe II-P with the massive H-envelope. In the explosion with the small-mass H-envelope, the expanding He core undergoes little deceleration, so that the gas density in the He core is too low for large-sized grains to form. In addition, the low-mass H-envelope of the SN IIb leads to the early arrival of the reverse shock at the dust-forming region. If the CSM is more or less spherical, therefore, the newly formed grains would be completely destroyed in the relatively dense shocked gas for the CSM density of n_H > 0.1 cm^{-3}. However, the actual CSM is likely to be non-spherical, so that a part of grains could be ejected into the ISM without being shocked. We demonstrate that the time evolution of the SED by thermal dust emission is sensitive to the ambient gas density and structure that affects the passage of the reverse shock into the ejecta. Thus, the SED evolution well reflects the evolution of dust through erosion by sputtering and stochastic heating. For Cas A, we consider the CSM produced by the steady mass loss of ~8x10^{-5} M_sun/yr during the supergiant phase. Then we find the infrared SED of Cas A is reasonably reproduced by thermal emission from the newly formed dust of 0.08 M_sun, which consists of 0.008 M_sun shocked warm dust and 0.072 M_sun unshocked cold dust.Comment: 50 pages, 17 figures, 3 tables. Accepted for publication in Ap

    Introduction : exploring forgiveness in nineteenth-century poetry

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    This essay serves as an introduction to the essays collected in the ‘Nineteenth-century Poetry and Forgiveness’ cluster. It takes as its foundation the recent turn to questions of hospitality, forgiveness and gift in the intra-disciplinary field of religion, philosophy and literature and highlights the centrality of these issues for reading nineteenth-century poetry. The essay argues that nineteenth-century poetry attempts to figure forgiveness as poetic sound and rhythm as a way of thinking reciprocal forgiving relationships between people. Part I contextualizes this argument and argues for an understanding of forgiveness through emotion. Part II offers an overview of the field of forgiveness scholarship and explores its relevance for nineteenth-century debate on the topic. Part III offers a way into thinking forgiveness as sound and rhythm in Wordsworth's poem ‘Airey-Force Valley’ through Martin Heidegger's reading of poetics and being

    Star-galaxy separation in the AKARI NEP Deep Field

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    Context: It is crucial to develop a method for classifying objects detected in deep surveys at infrared wavelengths. We specifically need a method to separate galaxies from stars using only the infrared information to study the properties of galaxies, e.g., to estimate the angular correlation function, without introducing any additional bias. Aims. We aim to separate stars and galaxies in the data from the AKARI North Ecliptic Pole (NEP) Deep survey collected in nine AKARI / IRC bands from 2 to 24 {\mu}m that cover the near- and mid-infrared wavelengths (hereafter NIR and MIR). We plan to estimate the correlation function for NIR and MIR galaxies from a sample selected according to our criteria in future research. Methods: We used support vector machines (SVM) to study the distribution of stars and galaxies in the AKARIs multicolor space. We defined the training samples of these objects by calculating their infrared stellarity parameter (sgc). We created the most efficient classifier and then tested it on the whole sample. We confirmed the developed separation with auxiliary optical data obtained by the Subaru telescope and by creating Euclidean normalized number count plots. Results: We obtain a 90% accuracy in pinpointing galaxies and 98% accuracy for stars in infrared multicolor space with the infrared SVM classifier. The source counts and comparison with the optical data (with a consistency of 65% for selecting stars and 96% for galaxies) confirm that our star/galaxy separation methods are reliable. Conclusions: The infrared classifier derived with the SVM method based on infrared sgc- selected training samples proves to be very efficient and accurate in selecting stars and galaxies in deep surveys at infrared wavelengths carried out without any previous target object selection.Comment: 8 pages, 8 figure

    Summary of Milestones 2030 : Elements and milestones for the development of a stable and sustainable bioenergy strategy

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    This publication is the English version of the summary of the German report „Meilensteine 2030“ (THRÄN et al. 2015) which is published in the series of the funding programme “Biomass energy use”. The report describes elements and milestones for the development of a stable and sustainable bioenergy strategy

    Number Counts At 3 < lambda < 10 um From the Spitzer Space Telescope

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    Infrared source counts at wavelengths 3 < lambda < 10 um cover more than 10 magnitudes in source brightness, four orders of magnitude in surface density, and reach an integrated surface density of 10^5 sources/deg^2. At m<14 mag, most of the sources are Galactic stars, in agreement with models. After removal of Galactic stars, galaxy counts are consistent with what few measurements exist at nearby wavelengths. At 3.6 and 4.5 um, the galaxy counts follow the expectations of a Euclidean world model down to ~16 mag and drop below the Euclidean curve for fainter magnitudes. Counts at these wavelengths begin to show decreasing completeness around magnitude 19.5. At 5.8 and 8 um, the counts relative to a Euclidean world model show a large excess at bright magnitudes. This is probably because local galaxies emit strongly in the aromatic dust (``PAH'') features. The counts at 3.6 um resolve <50% of the Cosmic Infrared Background at that wavelength.Comment: ApJS (in press), in the Spitzer Space Telescope special issue; 14 pages, 2 color figures, 1 table (electronic only

    Seeking legitimacy through CSR: Institutional Pressures and Corporate Responses of Multinationals in Sri Lanka

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    Arguably, the corporate social responsibility (CSR) practices of multinational enterprises (MNEs) are influenced by a wide range of both internal and external factors. Perhaps most critical among the exogenous forces operating on MNEs are those exerted by state and other key institutional actors in host countries. Crucially, academic research conducted to date offers little data about how MNEs use their CSR activities to strategically manage their relationship with those actors in order to gain legitimisation advantages in host countries. This paper addresses that gap by exploring interactions between external institutional pressures and firm-level CSR activities, which take the form of community initiatives, to examine how MNEs develop their legitimacy-seeking policies and practices. In focusing on a developing country, Sri Lanka, this paper provides valuable insights into how MNEs instrumentally utilise community initiatives in a country where relationship-building with governmental and other powerful non-governmental actors can be vitally important for the long-term viability of the business. Drawing on neo-institutional theory and CSR literature, this paper examines and contributes to the embryonic but emerging debate about the instrumental and political implications of CSR. The evidence presented and discussed here reveals the extent to which, and the reasons why, MNEs engage in complex legitimacy-seeking relationships with Sri Lankan institutions

    Extragalactic background light absorption signal in the TeV gamma-ray spectra of blazars

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    Recent observations of the TeV gamma-ray spectra of the two closest active galactic nuclei (AGNs), Markarian 501 (Mrk 501) and Markarian 421 (Mrk 421), by the Whipple and HEGRA collaborations have stimulated efforts to estimate or limit the spectral energy density (SED) of extragalactic background light (EBL) which causes attenuation of TeV photons via pair-production when they travel cosmological distances. In spite of the lack of any distinct cutoff-like feature in the spectra of Mrk 501 and Mrk 421 (in the interval 0.26-10 TeV) which could clearly indicate the presence of such a photon absorption mechanism, we demonstrate that strong EBL attenuation signal (survival probability of 10 TeV photon <10^{-2}) may still be present in the spectra of these AGNs. By estimating the minimal and maximal opacity of the universe to TeV gamma-ray photons, we calculate the visibility range for current and future gamma-ray observatories. Finally, we show that the proposed experiments, VERITAS, HESS, and MAGIC, may even be able to actually measure the EBL SED because their observations extend to the critical 75-150 GeV regime. In this transition region a distinct ``knee-like'' feature should exist in the spectra of blazars, which is invariant with respect to their intrinsic properties. The change of the spectral index and flux amplitude across this knee, if observed for several blazars, will provide missing pieces of information needed to measure EBL in the wavelength range 0.1-30 μ\mum.Comment: Accepted for publication in Astroparticle Physic
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