14,274 research outputs found

    Forward modelling of brightness variations in Sun-like stars I. Emergence and surface transport of magnetic flux

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    The latitudinal distribution of starspots deviates from the solar pattern with increasing rotation rate. Numerical simulations of magnetic flux emergence and transport can help model the observed stellar activity patterns and the associated brightness variations. We set up a composite model for the processes of flux emergence and transport on Sun-like stars, to simulate stellar brightness variations for various levels of magnetic activity and rotation rates. Assuming that the distribution of magnetic flux at the base of the convection zone follows solar scaling relations, we calculate the emergence latitudes and tilt angles of bipolar regions at the surface for various rotation rates, using thin-flux-tube simulations. Taking these two quantities as input to a surface flux transport SFT model, we simulate the diffusive-advective evolution of the radial field at the stellar surface, including effects of active region nesting. As the rotation rate increases, (1) magnetic flux emerges at higher latitudes and an inactive gap opens around the equator, reaching a half-width of 2020^\circ for 8Ω8\Omega_\odot, (2) the tilt angles of freshly emerged bipolar regions show stronger variations with latitude. Polar spots can form at 8Ω8\Omega_\odot by accumulation of follower-polarity flux from decaying bipolar regions. From 4Ω4\Omega_\odot to 8Ω8\Omega_\odot, the maximum spot coverage changes from 3 to 20%, respectively, compared to 0.4% for the solar model. Nesting of activity can lead to strongly non-axisymmetric spot distributions. On Sun-like stars rotating at 8Ω8\Omega_\odot (Prot3P_{\rm rot}\simeq 3 days), polar spots can form, owing to higher levels of flux emergence rate and tilt angles. Defining spots by a threshold field strength yields global spot coverages that are roughly consistent with stellar observations.Comment: 16 pages, 13 figures. Astron. & Astrophys. (in press); minor language corrections mad

    A hemophagocytic lymphohistiocytosis case with newly defined UNC13D (C.175G>C; p.Ala59Pro) mutation and a rare complication

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    Hemophagocytic lymphohistiocytosis (HLH) represents a severe hyperinflammatory condition with cardinal symptoms of prolonged fever, cytopenias, hepatosplenomegaly, and hemophagocytosis by activated, morphologically benign macrophages with impaired function of natural killer cells and cytotoxic T lymphocytes. A 2-month-old girl, who was admitted with fever, was diagnosed with HLH and her genetic examination revealed a newly defined mutation in the UNC13D (c.175G>C; p.Ala59Pro) gene. She was treated with dexamethasone, etoposide, and intrathecal methotrexate. During the second week of treatment, after three doses of etoposide, it was noticed that there was a necrotic plaque lesion on the soft palate. Pathologic examination of debrided material in PAS and Grocott staining revealed lots of septated hyphae, which was consistent with aspergillosis infection. Etoposide was stopped and amphotericin B treatment was given for six weeks. HLH 2004 protocol was completed to eight weeks with cyclosporine A orally. There was no patient with invasive aspergillosis infection as severe as causing palate and nasal septum perforation during HLH therapy. In immuncompromised patients, fungal infections may cause nasal septum perforation and treatment could be achieved by antifungal therapy and debridement of necrotic tissue. © 2015 Turkish Society of Hematology. All rights reserved

    An Empirical Analysis of Productivity Developments in "Traditional Banks" : The Initial Post-Liberalization Experience

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    By utilizing a non-parametric Malmquist index approach, we investigate the initial changes in the productivity and efficiency of the “traditional” Turkish banks in an era of financial liberalization (1980-1990). We hypothesize that the new liberal environment along with heightened competition from new banks coming from internal and external markets will discipline the traditional banks that are coming from the pre-liberalization period in resource management to economize their production inputs and/or in looking for new ways to expand their financial outputs, resulting in higher productivity and efficiency in these banks. Consistent with the expectations, we found that there is a significant upward trend in the productivity and efficiency of the traditional Turkish banks over the period under study. On the other hand, the results also indicate that the production technology of these banks has not advanced as expected. It appears that productivity growth in traditional Turkish banks mainly stems from the efforts of inefficient banks to catch up with the leading banks (efficiency increase) rather than the expansion of production frontier by the leading banks (technological progress).Traditional Banks, Productivity, Efficiency, Liberalization, Malmquist Index

    Philosophical Puzzles Evade Empirical Evidence: Some Thoughts and Clarifications Regarding the Relation Between Brain Sciences and Philosophy of Mind

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    This chapter analyzes the relation between brain sciences and philosophy of mind, in order to clarify in what ways philosophy can contribute to neuroscience and neuroscience can contribute to philosophy. Especially since the 1980s and the emergence of “neurophilosophy”, more and more philosophers have been bringing home morals from neuroscience to settle philosophical issues. I mention examples from the problem of consciousness, philosophy of perception and the problem of free will, and I argue that such attempts are not successful in trying to settle questions like whether psychology can be reduced to neuroscience, whether we see the external world directly in perception, or whether we have free will. The failure results from an ability of the philosophical questions to evade the data. What makes these questions persisting philosophical questions is precisely that there is no way to settle them through empirical evidence, as they are conceptual questions and their solution lies in conceptual analysis

    Looking for activity cycles in late-type Kepler stars using time-frequency analysis

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    We analyse light curves covering four years of 39 fast-rotating (Prot<1dP_\mathrm{rot}< 1d) late-type active stars from the Kepler database. Using time-frequency analysis (Short-Term Fourier-Transform), we find hints for activity cycles of 300-900 days at 9 targets from the changing typical latitude of the starspots, which, with the differential rotation of the stellar surface change the observed rotation period over the activity cycle. We also give a lowest estimation for the shear parameter of the differential rotation, which is ~0.001 for the cycling targets. These results populate the less studied, short period end of the rotation-cycle length relation.Comment: 12 pages, 7 figures, accepted for publication in MNRA

    Identity, face and (im)politeness

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    Face and (im)politeness are widely discussed and debated in the pragmatics literature. This special issue, which has developed out of a symposium presented at the 7th International Pragmatics Conference at Riva del Garda, Italy in 2005, aims to enrich our understanding of these concepts by examining them from the perspective of identity. The first three papers consider the conceptual insights that different (sub-)disciplines can offer for our understanding of face, (im)politeness and the management of rapport. They draw on work in social psychology on identity, and take a cognitive pragmatic perspective to deconstruct relevant emic concepts/lexemes. The next four papers present discourse-based research on the topic. They examine different types of identities, including role identities (e.g. leaders and mentors), national identities (e.g. Turkish and British), ethnic identities (e.g. Pakeha and Maori), community identities (e.g. Cyber-parish member), as well as individual identities, and analyse how these identities impact upon the (mis)management of face and rapport

    Maximum-order Complexity and Correlation Measures

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    We estimate the maximum-order complexity of a binary sequence in terms of its correlation measures. Roughly speaking, we show that any sequence with small correlation measure up to a sufficiently large order kk cannot have very small maximum-order complexity

    THE SYNERGY BETWEEN SUBSECTOR COMPETITIVENESS AND REGIONAL DEVELOPMENT: THE CASE OF TURKEY AND THE TOMATO SUBSECTOR

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    Abstract This study develops a conceptual model of the institutions and key factors that facilitate competitiveness on the national and subsector level and then determines how linkages between the factors that enhance competitiveness and regional development can be created. Turkey and the Turkish tomato subsector provided the case to test this model.Regional development, sustainable competitiveness, tomato processing industry, Turkey, industry clusters, Community/Rural/Urban Development,
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