476 research outputs found

    Positivity of Chern Classes for Reflexive Sheaves on P^N

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    It is well known that the Chern classes cic_i of a rank nn vector bundle on \PP^N, generated by global sections, are non-negative if i≀ni\leq n and vanish otherwise. This paper deals with the following question: does the above result hold for the wider class of reflexive sheaves? We show that the Chern numbers cic_i with i≄4i\geq 4 can be arbitrarily negative for reflexive sheaves of any rank; on the contrary for i≀3i\leq 3 we show positivity of the cic_i with weaker hypothesis. We obtain lower bounds for c1c_1, c2c_2 and c3c_3 for every reflexive sheaf \FF which is generated by H^0\FF on some non-empty open subset and completely classify sheaves for which either of them reach the minimum allowed, or some value close to it.Comment: 16 pages, no figure

    La crisis del fĂștbol ecuatoriano

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    El fútbol mundial y local cada vez moviliza más recursos. Se estima que los equipos europeos actualmente reciben ingresos cercanos a USD 23 mil millones al año, con un crecimiento del 5,6% anual en los últimos 5 años. En el caso del fútbol ecuatoriano, los equipos estiman gastar USD 54 millones en 2013, 8% más respecto al año pasado. Desde el punto de vista deportivo, los resultados alcanzados por el fútbol ecuatoriano en esta última década son los mejores de su historia. Sin embargo, la mayoría delos equipos atraviesan serias dificultades financieras. Ocho de los doce equipos de la Serie A suman deudas de alrededor de USD 33 millones. Las dificultades de los clubes ecuatorianos no son ajenas a los equipos del resto del mundo. La deuda de los equipos ingleses supera los USD 4 mil millones.Esta crisis financiera de los equipos radica en la estructura organizativa de las ligas de fútbol, que, desde inicios de la profesionalización, se diseñaron bajo la premisa de que los clubes no debían perseguir fines de lucro. Con el objeto de comprender mejor el origen y causas de la crisis del fútbol nacional, a continuación se repasa brevemente el inicio y evolución de la profesionalización del fútbol a nivel mundial y local. Posteriormente se expone el estado actual de las finanzas de los equipos ecuatorianos. Finalmente se presentan las dos relaciones fundamentales que rigen la industria de los clubes de fútbol producto de la estructura de las ligas, y que explican la crisis.El fĂștbol mundial y local cada vez moviliza mĂĄs recursos. Se estima que los equipos europeos actualmente reciben ingresos cercanos a USD 23 mil millones al año, con un crecimiento del 5,6% anual en los Ășltimos 5 años. En el caso del fĂștbol ecuatoriano, los equipos estiman gastar USD 54 millones en 2013, 8% mĂĄs respecto al año pasado. Desde el punto de vista deportivo, los resultados alcanzados por el fĂștbol ecuatoriano en esta Ășltima dĂ©cada son los mejores de su historia. Sin embargo, la mayorĂ­a delos equipos atraviesan serias dificultades financieras. Ocho de los doce equipos de la Serie A suman deudas de alrededor de USD 33 millones. Las dificultades de los clubes ecuatorianos no son ajenas a los equipos del resto del mundo. La deuda de los equipos ingleses supera los USD 4 mil millones.Esta crisis financiera de los equipos radica en la estructura organizativa de las ligas de fĂștbol, que, desde inicios de la profesionalizaciĂłn, se diseñaron bajo la premisa de que los clubes no debĂ­an perseguir fines de lucro. Con el objeto de comprender mejor el origen y causas de la crisis del fĂștbol nacional, a continuaciĂłn se repasa brevemente el inicio y evoluciĂłn de la profesionalizaciĂłn del fĂștbol a nivel mundial y local. Posteriormente se expone el estado actual de las finanzas de los equipos ecuatorianos. Finalmente se presentan las dos relaciones fundamentales que rigen la industria de los clubes de fĂștbol producto de la estructura de las ligas, y que explican la crisis

    Evaluation of the impact of heat-wave on distribution system resilience

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    This paper addresses the impact of heat waves on a real urban distribution system. A data-driven methodology is proposed to simulate the portion of faults that can be associated to normal conditions (and hence to reliability) and the portion correlated to the heat wave occurrence. Based on real data collected in the years 2012-2017, the fault rates associated to reliability and resilience have been calculated and then used to feed a Monte Carlo simulation aiming to manage the uncertainty in the fault occurrence. Finally, based on the Italian legislation, the avoided costs deriving by the substitution of the faulted portion of the system have been calculated. The results show the different nature of reliability and resilience in terms of empirical cumulative curve, suggesting the necessity of using a stochastic-based methodology within regulatory frameworks, especially in case of output-based regulation

    Occurrence of malignant neoplasia in patients with primary hyperparathyroidism

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    Introduction The association between primary hyperparathyroidism (1HPT) and cancer is debated. The present study was aimed to investigate the occurrence of neoplasia in 1HPT. Patients and methods All consecutive patients (n = 1750) referred to our \u201cOsteoporosis and Metabolic Disease\u201d outpatients clinic for osteoporosis or hypercalcemia were eligible for the study. The exclusion criteria were: the finding of osteoporosis and/or altered calcium-phosphorous metabolism in the context of investigations for malignancy, the presence of diseases known to influence the cancer risk and the heavy smoking habit. Eventually, 1606 patients (1407 females, 199 males) were enrolled. In all patients calcium-phosphorous metabolism, PTH and vitamin D levels were measured and the occurrence of cancer during the 10 years prior the study inclusion was recorded. Results One-hundred-sixty-three patients had 1HPT while 1443 had not. Patients with and without 1HPT were comparable for age and gender. In 1HPT patients the occurrence of all, breast, kidney and skin cancer was significantly higher (21.5%, 12.2%, 2.5%, 1.8%, respectively) than in patients without 1HPT (12.4%, 6.9%, 0.3%, 0.3%, p < 0.05 for all comparisons). The 1HPT presence was significantly associated with the occurrence of all neoplasia and of breast, skin and kidney neoplasia (odds ratio, 95% confidence interval, p value: 1.93, 1.27\u20132.92, 0.002; 1.93, 1.11\u20133.35, 0.002; 9.18, 2.16\u201338.8, 0.003; 8.23, 1.71\u201339.5, 0.008, respectively), after adjusting for age, gender (as appropriate), smoking habit and vitamin D levels. Conclusion During the 10 years prior the diagnosis of 1HPT, the occurrence of all, breast, skin and kidney neoplasia is increased

    Multiple Exportins Influence Thyroid Hormone Receptor Localization

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    The thyroid hormone receptor (TR) undergoes nucleocytoplasmic shuttling and regulates target genes involved in metabolism and development. Previously, we showed that TR follows a CRM1/calreticulinmediated nuclear export pathway. However, two lines of evidence suggest TR also follows another pathway: export is only partially blocked by leptomycin B (LMB), a CRM1-specific inhibitor; and we identified nuclear export signals in TR that are LMB-resistant. To determine whether other exportins are involved in TR shuttling, we used RNA interference and fluorescence recovery after photobleaching shuttling assays in transfected cells. Knockdown of exportins 4, 5, and 7 altered TR shuttling dynamics, and when exportins 5 and 7 were overexpressed, TR distribution shifted towards the cytosol. To further assess the effects of exportin overexpression, we examined transactivation of a TR-responsive reporter gene. Our data indicate that multiple exportins influence TR localization, highlighting a fine balance of nuclear import, retention, and export that modulates TR function
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