2,564 research outputs found

    CVA and vulnerable options pricing by correlation expansions

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    We consider the problem of computing the Credit Value Adjustment ({CVA}) of a European option in presence of the Wrong Way Risk ({WWR}) in a default intensity setting. Namely we model the asset price evolution as solution to a linear equation that might depend on different stochastic factors and we provide an approximate evaluation of the option's price, by exploiting a correlation expansion approach, introduced in \cite{AS}. We compare the numerical performance of such a method with that recently proposed by Brigo et al. (\cite{BR18}, \cite{BRH18}) in the case of a call option driven by a GBM correlated with the CIR default intensity. We additionally report some numerical evaluations obtained by other methods.Comment: 21 page

    The role of mass, equation of state and superfluid reservoir in large pulsar glitches

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    Observations of pulsar glitches may provide insights on the internal physics of neutron stars and recent studies show how it is in principle possible to constrain pulsar masses with timing observations. The reliability of these estimates depend on the current uncertainties about the structure of neutron stars and on our ability to model the dynamics of the superfluid neutrons in the internal layers. We assume a simplified model for the rotational dynamics of a neutron star and estimate an upper bound to the mass of 25 pulsars from their largest glitch and average activity: the aim is to understand to which extent the mass constraints are sensitive to the choice of the unknown structural properties of neutron stars, like the extension of the superfluid region and the equation of state. Reasonable values, within the range measured for neutron star masses, are obtained only if the superfluid domain extends for at least a small region inside the outer core, which is compatible with calculations of the neutron S-wave pairing gap. Moreover, the mass constraints stabilise when the superfluid domain extends to densities over nuclear saturation, irrespective of the equation of state tested.Comment: 11 pages, 6 figure

    The Very High Energy source catalog at the ASI Science Data Center

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    The increasing number of Very High Energy (VHE) sources discovered by the current generation of Cherenkov telescopes made particularly relevant the creation of a dedicated source catalogs as well as the cross-correlation of VHE and lower energy bands data in a multi-wavelength framework. The "TeGeV Catalog" hosted at the ASI Science Data Center (ASDC) is a catalog of VHE sources detected by ground-based Cherenkov detectors. The TeGeVcat collects all the relevant information publicly available about the observed GeV/TeV sources. The catalog contains also information about public light curves while the available spectral data are included in the ASDC SED Builder tool directly accessible from the TeGeV catalog web page. In this contribution we will report a comprehensive description of the catalog and the related tools.Comment: 5 pages, 3 figures - Proceeding of the 34th International Cosmic Ray Conferenc

    New therapies, markers and therapeutic targets in HCV chronic infection, and HCV extrahepatic manifestations

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    More than 180 millions of subjects in the world are infected by Hepatitis C Virus (HCV), and about 20% of them with HCV chronic infection progress to cirrhosis. Furthermore, numerous HCV extrahepatic manifestations have been reported in up to 74% of patients, as mixed cryoglobulinemia, lymphomas, rheumatic disorders, autoimmune thyroiditis, hypothyroidism, papillary thyroid cancer, and type 2 diabetes. Advances in understanding the HCV life cycle, and the inflammatory processes (involving a complex network of cytokines and chemokines) associated with HCV chronic infection, have led to substantial advancements in therapy. The combination of ribavirin and PEGylated interferon-gamma was the standard of therapy for HCV chronically infected patients in the last decades. However, interferon has limited effectiveness and is associated with severe adverse effects. Recently, direct-acting antivirals (DAAs) that act as inhibitors of N5SA, or polymerase, or protease have been shown to result in shorter duration of therapy, better efficacy and tolerance, with respect to ribavirin and PEGylated interferon-gamma. Circulating CXCL10 levels, and the interleukin(IL)-28B gene polymorphisms, are associated with the success of the therapy both with DAAs or ribavirin and PEGylated interferon-alpha. New DAAs targeting the HCV at various molecular levels have been developed to eradicate HCV. Moving to interferon-free therapies should offer new treatments for resistant HCV genotypes, and for ineligible patients or patients failing to respond to prior therapies. Many efforts have been made to understand the factors that are involved with clearance of HCV to personalize the therapy for each patient, with the aim to reduce side effects, increasing the sustained virologic response rate, and to prevent the progression of the disease

    Transdural Spread of Glioblastoma with Endonasal Growth in a Long-Term Survivor Patient: Case Report and Literature Review.

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    Glioblastoma (GBM) is the most aggressive primary tumor of the central nervous system (CNS) in adults. Its growth has been always described as locally invasive. This tumor rarely penetrates dura mater and invades extracranial structures. We present a case of GBM, which occurred in a 39-year-old man, with final involvement of the nasal cavity. The patient was operated four times in three years, and a personalized adjuvant chemotherapy regimen was administered in a neo-adjuvant fashion. Histopathological features of the tumor are described. To our knowledge, there are only 9 cases reported in the literature showing this growth pattern and the last case was reported in 1998

    A Patient-Specific Treatment Model for Graves’ Hyperthyroidism

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    Background: Graves’ is disease an autoimmune disorder of the thyroid gland caused by circulating anti-thyroid receptor antibodies (TRAb) in the serum. TRAb mimics the action of thyroid stimulating hormone (TSH) and stimulates the thyroid hormone receptor (TSHR), which results in hyperthyroidism (overactive thyroid gland) and goiter. Methimazole (MMI) is used for hyperthyroidism treatment for patients with Graves’ disease. Methods: We have developed a model using a system of ordinary differential equations for hyperthyroidism treatment with MMI. The model has four state variables, namely concentration of MMI (in mg/L), concentration of free thyroxine - FT4 (in pg/mL), and concentration of TRAb (in U/mL) and the functional size of the thyroid gland (in mL) with thirteen parameters. With a treatment parameter, we simulate the time-course of patients’ progression from hyperthyroidism to euthyroidism (normal condition). We validated the model predictions with data from four patients. Results: When there is no MMI treatment, there is a unique asymptotically stable hyperthyroid state. After the initiation of MMI treatment, the hyperthyroid state moves towards subclinical hyperthyroidism and then euthyroidism. Conclusion: We can use the model to describe or test and predict patient treatment schedules. More specifically, we can fit the model to individual patients’ data including loading and maintenance doses and describe the mechanism, hyperthyroidism → euthyroidism. The model can be used to predict when to discontinue the treatment based on FT4 levels within the physiological range, which in turn help maintain the remittance of euthyroidism and avoid relapses of hyperthyroidism. Basically, the model can guide with decision-making on oral intake of MMI based on FT4 levels

    Refractory hypothyroidism due to improper storage of levothyroxine tablets

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    Context: A not negligible part of hypothyroid patients on levothyroxine therapy do not normalize serum thyrotropin (TSH) concentrations. "Refractory hypothyroidism," i.e., a condition characterized by persistently abnormal serum TSH levels despite adequate titration of l-T4 substitution therapy, requires biochemical and instrumental investigation, but no definite etiology is found in up to 15% of cases. Objective: To report patients presenting with refractory hypothyroidism with proven improper storage of levothyroxine tablets. Design: Patients on l-T4 substitution therapy referred to three Italian outpatient Clinics of Endocrinology between January 2013 and December 2015 for refractory hypothyroidism were investigated for levothyroxine tablet exposure to humidity, light, and high temperature. Results: We report eight patients, accounting for approximately 1% of all hypothyroid patients and 5% of those with refractory hypothyroidism in our series. Careful anamnesis disclosed that these patients stored levothyroxine tablets inappropriately. Normalization of serum TSH concentrations was obtained in all cases by simply recommending to store the new levothyroxine tablets away from heat, light, and humidity. Conclusion: Refractory hypothyroidism linked to improper storage of l-T4 tablets does exist and might be an underrecognized entity. In addition to proper modalities of ingestion of l-T4 tablets, patients need to be instructed on proper modalities of storage, as well
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