4,951 research outputs found

    On affine scaling inexact dogleg methods for bound-constrained nonlinear systems

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    Within the framework of affine scaling trust-region methods for bound constrained problems, we discuss the use of a inexact dogleg method as a tool for simultaneously handling the trust-region and the bound constraints while seeking for an approximate minimizer of the model. Focusing on bound-constrained systems of nonlinear equations, an inexact affine scaling method for large scale problems, employing the inexact dogleg procedure, is described. Global convergence results are established without any Lipschitz assumption on the Jacobian matrix, and locally fast convergence is shown under standard assumptions. Convergence analysis is performed without specifying the scaling matrix used to handle the bounds, and a rather general class of scaling matrices is allowed in actual algorithms. Numerical results showing the performance of the method are also given

    What are the consequences of global banking for the international transmission of shocks? A quantitative analysis

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    The global financial crisis of 2008 was followed by a wave of regulatory reforms that affected large banks, especially those with a global presence. These reforms were reactive to the crisis. In this paper we propose a structural model of global banking that can be used proactively to perform counterfactual analysis on the effects of alternative regulatory policies. The structure of the model mimics the US regulatory framework and highlights the organizational choices that banks face when entering a foreign market: branching versus subsidiarization. When calibrated to match moments from a sample of European banks, the model is able to replicate the response of the US banking sector to the European sovereign debt crisis. Our counterfactual analysis suggests that pervasive subsidiarization, higher capital requirements, or ad hoc monetary policy interventions would have mitigated the effects of the crisis on US lending.https://www.nber.org/papers/w25203Published versio

    Action of HMGB1 on miR221/222 cluster in neuroblastoma cell lines

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    microRNA (miR/miRNA) are small non-coding RNAs that control gene expression at the post-transcriptional level by targeting mRNAs. Aberrant expression of miRNAs is often observed in different types of cancer. Specific miRNAs function as tumor suppressors or oncogenes and interfere with various aspects of carcinogenesis, including differentiation, proliferation and invasion. Upregulation of miRNAs 221 and 222 has been shown to induce a malignant phenotype in numerous human cancers via inhibition of phosphatase and tensin homolog (PTEN) expression. Neuroblastoma is the most common extracranial solid malignancy in children, which is characterized by cellular heterogeneity that corresponds to different clinical outcomes. The different cellular phenotypes are associated with different gene mutations and miRs that control genetic and epigenetic factors. For this reason miRs are considered a potential therapeutic target in neuroblastoma. The aim of the present study was to investigate the mechanisms by which extracellular high mobility group box 1 (HMGB1) promotes cell growth in neuroblastoma. SK-N-BE(2) and SH-SY5Y neuroblastoma derived cell lines were transfected with the antisense oligonucleotides, anti-miR-221 and -222, followed by treatment with HMGB1 to investigate the expression of the oncosuppressor PTEN. In this study, it was demonstrated that HMGB1, which is released by damaged cells and tumor cells, upregulates miR-221/222 oncogenic clusters in the two human neuroblastoma derived cell lines. The results revealed that the oncogenic cluster miRs 221/222 were more highly expressed by the most undifferentiated cell line [SK-N-BE(2)] compared with the the less tumorigenic cell line (SH-SY5Y) and that exogenous HMGB1 increases this expression. In addition, HMGB1 modulates PTEN expression via miR-221/222, as demonstrated by transiently blocking miR-221/222 with anti-sense oligonucleotides. These results may lead to the development of novel therapeutic strategies for neuroblastoma

    Identification of onosma visianii roots extract and purified shikonin derivatives as potential acaricidal agents against tetranychus urticae

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    There is an increasing need for the discovery of reliable and eco-friendly pesticides and natural plant-derived products may play a crucial role as source of new active compounds. In this research, a lipophilic extract of Onosma visianii roots extract containing 12% of shikonin derivatives demonstrated significant toxicity and inhibition of oviposition against Tetranychus urticae mites. Extensive chromatographic separation allowed the isolation of 11 naphthoquinone derivatives that were identified by spectral techniques and were tested against Tetranychus urticae. All the isolated compounds presented effects against the considered mite and isobutylshikonin (1) and isovalerylshikonin (2) were the most active, being valuable model compounds for the study of new anti-mite agents

    Serum dioxin concentrations and endometriosis: a cohort study in Seveso, Italy.

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    Dioxin, a ubiquitous contaminant of industrial combustion processes including medical waste incineration, has been implicated in the etiology of endometriosis in animals. We sought to determine whether dioxin exposure is associated with endometriosis in humans. We conducted a population-based historical cohort study 20 years after the 1976 factory explosion in Seveso, Italy, which resulted in the highest known population exposure to 2,3,7,8-tetrachlorodibenzo-(italic)p(/italic)-dioxin (TCDD). Participants were 601 female residents of the Seveso area who were (3/4) 30 years old in 1976 and had adequate stored sera. Endometriosis disease status was defined by pelvic surgery, current transvaginal ultrasound, pelvic examination, and interview (for history of infertility and pelvic pain). "Cases" were women who had surgically confirmed disease or an ultrasound consistent with endometriosis. "Nondiseased" women had surgery with no evidence of endometriosis or no signs or symptoms. Other women had uncertain status. To assess TCDD exposure, individual levels of TCDD were measured in stored sera collected soon after the accident. We identified 19 women with endometriosis and 277 nondiseased women. The relative risk ratios (RRRs) for women with serum TCDD levels of 20.1-100 ppt and >100 ppt were 1.2 [90% confidence interval (CI) = 0.3-4.5] and 2.1 (90% CI = 0.5-8.0), respectively, relative to women with TCDD levels (3/4) 20 ppt. Tests for trend using the above exposure categories and continuous log TCDD were nonsignificant. In conclusion, we report a doubled, nonsignificant risk for endometriosis among women with serum TCDD levels of 100 ppt or higher, but no clear dose response. Unavoidable disease misclassification in a population-based study may have led to an underestimate of the true risk of endometriosis

    Long time behavior of the Caginalp system with singular potentials and dynamic boundary conditions

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    This paper is devoted to the study of the well-posedness and the long time behavior of the Caginalpphase-field model with singular potentials and dynamic boundary conditions.Thanks to a suitable definition of solutions, coinciding with the strong ones underproper assumptions on the bulk and surfacepotentials, we are able to get dissipative estimates, leading tothe existence of the global attractor with finite fractal dimension,as well as of an exponential attractor

    Mathematics self-confidence and the "prepayment effect" in riskless choices

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    We extend the analysis of a riskless choice experiment reported recently by Hochman et al. (2014). Participants select from among sets of standard playing cards valued by a simple formula. In some sessions, participants are given a prepayment associated with some of the cards, which need not be the earnings-maximizing ones. Hochman et al. find that participants choose an earnings-maximizing card less frequently when another card is prepaid. We replicate this result under the original instructions, but not with instructions which explain the payment process more explicitly. Participants who state they do not consider themselves good at mathematics make earnings-maximizing choices much less frequently overall, but those who express self-confidence in mathematics drive the treatment effect. The results suggest that even when comparisons among choices require only simple quantitative reasoning steps, market designers and regulators may need to pay close attention to how the terms of offers are expressed, explained, and implemented
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