A sparse grid approach to balance sheet risk measurement

In this work, we present a numerical method based on a sparse grid approximation to compute the loss distribution of the balance sheet of a financial or an insurance company. We first describe, in a stylised way, the assets and liabilities dynamics that are used for the numerical estimation of the balance sheet distribution. For the pricing and hedging model, we chose a classical Black & Scholes model with a stochastic interest rate following a Hull & White model. The risk management model describing the evolution of the parameters of the pricing and hedging model is a Gaussian model. The new numerical method is compared with the traditional nested simulation approach. We review the convergence of both methods to estimate the risk indicators under consideration. Finally, we provide numerical results showing that the sparse grid approach is extremely competitive for models with moderate dimension.Comment: 27 pages, 7 figures. CEMRACS 201

Breakdown of Reye's theory in nanoscale wear

Building on an analogy to ductile fracture mechanics, we quantify the size of debris particles created during adhesive wear. Earlier work suggested a linear relation between tangential work and wear debris volume, assuming that the debris size is proportional to the micro contact size multiplied by the junction shear strength. However, the present study reveals deviations from linearity. These deviations can be rationalized with fracture mechanics and imply that less work is necessary to generate debris than what was assumed. Here, we postulate that the work needed to detach a wear particle is made of the surface energy expended to create new fracture surfaces, and also of plastic work within a fracture process zone of a given width around the cracks. Our theoretical model, validated by molecular dynamics simulations, reveals a super-linear scaling relation between debris volume ($V_d$) and tangential work ($W_t$): $V_d \sim W_t^{3/2}$ in 3D and $V_d \sim W_t^{2}$ in 2D. This study provides a theoretical foundation to estimate the statistical distribution of sizes of fine particles emitted due to adhesive wear processes

Les savoirs professionnels mobilisés dans le travail des conseillers pédagogiques de l’enseignement agricole public

L’article appréhende les séances de conseil pédagogique pendant les stages de pratique accompagnée des professeurs stagiaires de l’enseignement agricole public français, à partir du modèle des situations de tutelle proposé par Jérôme Bruner. Son objectif est de décrire les savoirs professionnels mobilisés par les conseillers pédagogiques pour permettre les apprentissages de leurs stagiaires. L’analyse de l’enregistrement de 14 séances de débriefing permet de repérer la mise en œuvre des six fonctions de l’étayage qu’a définies Bruner (caractéristiques des situations de tutelle et regroupées en « fonction relationnelle » et « fonction de guidance » et « fonction d’intervention ») et atteste ainsi de la mobilisation de savoirs professionnels spécifiques au conseil pédagogique. Quatre familles de savoirs ont pu être identifiées, les savoirs professionnels relatifs à l’instauration du dialogue, les savoirs professionnels relatifs à la théorisation de l’expérience, les savoirs professionnels relatifs à l’inférence et les savoirs professionnels relatifs à l’évaluation.The article dreads the sessions of educational advice during the training courses of practice accompanied with the professors trainees of the French public agricultural education, from the model of the situations of supervision proposed by Jérôme Bruner. His objective is to describe the professional knowledges mobilized by the educational advisers to allow the learnings of their trainees. The analysis of the recording of 14 sessions of debriefing allows to spot (locate) the implementation of six functions(offices) of the propping up which defined Bruner ( characteristics of the situations of supervision(guardianship) and grouped together(included) " relational function (office) " and " function(office) of guidance " and " function(office) of intervention ") and so gives evidence of the mobilization of specific professional knowledges in the educational advice(council). Four families of knowledges were able to be identified, the professional knowledges relative to the institution of the dialogue, the professional knowledges relative to the theorization of the experience(experiment), the professional knowledges relative to the inference and the professional knowledges relative to the evaluation.El artículo aprehende las sesiones de consejo pedagógico durante las prácticas de práctica acompañada por los profesores cursillistas de la enseñanza agrícola pública francesa, a partir del modelo de las situaciones de tutela propuesto por Jerôme Bruner. Su objetivo es describir el saber profesional movilizados por los consejeros pedagógicos para permitir los aprendizajes de sus curcillistas. El análisis del registro de 14 sesiones de débriefing permite reparar en la puesta en ejecución de las seis funciones del étayage que definió Bruner (características de las situaciones de tutela y reagrupadas " función relacional " y " función de guidance " y " función de intervención ") y atestigua así de la movilización de saber profesional específico al consejo pedagógico. Cuatro familias de saber pudieron ser identificadas, el saber profesional relativos a la instauración del diálogo, el saber profesional relativos a la teorización de la experiencia(experimento), el saber profesional relativos a la inferencia y el saber profesional relativos a la evaluación

Diagnostic procedures and long-term prognosis in bilateral renal cortical necrosis

Diagnostic procedures and long-term prognosis in bilateral renal cortical necrosis. Thirty-eight patients with bilateral renal cortical necrosis (BRCN) were studied with special reference to etiology, diagnostic procedures and ultimate prognosis. BRCN was of obstetrical origin in 26 patients and more frequent during the third trimester of pregnancy (21%) than earlier (1.5%). Renal biopsy, renal arteriography and hemodynamic data were useful procedures in the early differentiation of total from patchy BRCN. In patients with patchy BRCN, the percentage of destroyed glomeruli on the kidney biopsy specimen was lower than in those with total BRCN, renal arteriography showed that the cortical nephrogram was present but non-homogeneous and mean renal blood flow (MRBF) (85Kr method) fell within the range observed in patients with acute tubular nephropathy undergoing full recovery. In patients with total BRCN, cortical tissue was uniformly necrotic, the cortical nephrogram was completely absent, MRBF was always below 50 ml/100 g·min and a first component was never recognizable. Biological evidence of intravascular coagulation was inconstant. Intrarenal vascular thrombi were only found in the renal biopsy specimens of those patients with short survival. Partial recovery occurred in 16 patients and GFR increased over a one year period. Subsequent deterioration of renal function occurred in nine patients requiring chronic hemodialysis and/or renal transplantation.Diagnostic et pronostic lointain des nécroses corticales bilatérales des reins. Trente-huit malades atteints de nécrose corticale bilatérale des reins (NCR) ont été spécialement étudiés du point de vue de l'étiologie, des méthodes de diagnostic et du pronostic lointain. La NCR a été d'origine obstétricale chez 26 malades et a été plus souvent observée pendant le troisième trimestre de la grossesse (21%) que plus précocement (1, 5%). La biopsie rénale, l'artériographie rénale et les données hémodynamiques ont été utiles pour distinguer les NCR totales et partielles. Chez les malades atteints de NCR partielle, la biopsie rénale a montré que le pourcentage de glomérules détruits était plus bas que dans les NCR totales, l'artériographie rénale a montré que la néphrographie corticale était présente mais non-homogène et le flux sanguin rénal moyen (FSRM) (méthode au 85Kr) restait compris dans les limites observées chez les malades atteints de néphropathie tubulaire aiguë avec guérison complète. Chez les malades atteints de NCR totale, le tissu rénal cortical était uniformément nécrotique, la néphrographie corticale totalement absente, le FSRM était toujours inférieur à 50 ml/100 g·mn et aucun premier composant n'était individualisable. Les preuves biologiques d'une coagulation intravasculaire ont été inconstantes. Des thrombi vasculaires intrarénaux n'ont été rencontrés en biopsie que chez les malades ayant une courte survie. Une récupération partielle a été observée chez 16 malades et la FG a continué à s'élever au-delà de la première année. Une aggravation secondaire de la fonction rénale est survenue chez neuf malades, nécessit ant des hémodialyses périodiques et/ou une transplantation rénale

DC-SIGN–mediated Infectious Synapse Formation Enhances X4 HIV-1 Transmission from Dendritic Cells to T Cells

Dendritic cells (DCs) are essential for the early events of human immunodeficiency virus (HIV) infection. Model systems of HIV sexual transmission have shown that DCs expressing the DC-specific C-type lectin DC-SIGN capture and internalize HIV at mucosal surfaces and efficiently transfer HIV to CD4+ T cells in lymph nodes, where viral replication occurs. Upon DC–T cell clustering, internalized HIV accumulates on the DC side at the contact zone (infectious synapse), between DCs and T cells, whereas HIV receptors and coreceptors are enriched on the T cell side. Viral concentration at the infectious synapse may explain, at least in part, why DC transmission of HIV to T cells is so efficient

Primary Hyperparathyroidism: Can Parathyroid Carcinoma Be Anticipated on Clinical and Biochemical Grounds? Report of Nine Cases and Review of the Literature

Background: Parathyroid carcinoma (PC) mimics benign primary hyperparathyroidism (PHP), but the diagnosis of PC is seldom available at the time of the first operation. Because PC is plagued by recurrences usually beyond cure, one may wonder whether some of these could be prevented by more extensive resections initially, i.e., if the diagnosis of PC were available at that time. Methods: Over a 25-year period, 311 consecutive patients with PHP underwent operation in our department: 302 had benign disease (adenomas or hyperplasias), and 9 had PC. Several clinical parameters, serum calcium and parathyroid hormone (PTH) levels, and the weight of the parathyroid tumor removed were compared in both groups. Receiver operating characteristic curves and logistical regression analyses were used to distinguish PC from benign PHP. Results: Eight of 9 patients with PC had symptoms, versus 238 (79%) of 302 with benign PHP (not significant). In the PC subgroup, serum calcium and PTH levels and the tumor weights of the parathyroid glands removed were significantly higher than in the benign PHP cohort, even if these three parameters were regularly flawed by low positive predictive values (14%, 20%, and 15%, respectively). Conclusions: Serum calcium, PTH levels, and tumor weights were significantly greater in the PC subgroup, even if not invariably in a discriminatory way. However, when PTH is <4 times the upper limit of normal and tumor weight is <1.9 g, the probability of PC is ni

Lack of dietary polyunsaturated fatty acids causes synapse dysfunction in the drosophila visual system

Polyunsaturated fatty acids (PUFAs) are essential nutrients for animals and necessary for the normal functioning of the nervous system. A lack of PUFAs can result from the consumption of a deficient diet or genetic factors, which impact PUFA uptake and metabolism. Both can cause synaptic dysfunction, which is associated with numerous disorders. However, there is a knowledge gap linking these neuronal dysfunctions and their underlying molecular mechanisms. Because of its genetic manipulability and its easy, fast, and cheap breeding, Drosophila melanogaster has emerged as an excellent model organism for genetic screens, helping to identify the genetic bases of such events. As a first step towards the understanding of PUFA implications in Drosophila synaptic physiology we designed a breeding medium containing only very low amounts of PUFAs. We then used the fly’s visual system, a well-established model for studying signal transmission and neurological disorders, to measure the effects of a PUFA deficiency on synaptic function. Using both visual performance and eye electrophysiology, we found that PUFA deficiency strongly affected synaptic transmission in the fly’s visual system. These defects were rescued by diets containing omega-3 or omega-6 PUFAs alone or in combination. In summary, manipulating PUFA contents in the fly’s diet was powerful to investigate the role of these nutrients on the fly´s visual synaptic function. This study aims at showing how the first visual synapse of Drosophila can serve as a simple model to study the effects of PUFAs on synapse function. A similar approach could be further used to screen for genetic factors underlying the molecular mechanisms of synaptic dysfunctions associated with altered PUFA levels

Fluid-mediated impact of soft solids

A viscous, lubrication-like response can be triggered in a thin film of fluid squeezed between a rigid and flat surface and the tip of an incoming projectile. We develop a comprehensive theory for this viscous approach stage of fluid-mediated normal impact, applicable to soft impactors. Under the assumption of mediating fluid being incompressible, the impacting solid displays two limit regimes: one dominated by elasticity and the other by inertia. The transition between the two is predicted by a dimensionless parameter, which can be interpreted as the ratio between two time scales that are the time that it takes for the surface waves to warn the leading edge of the impactor of the forthcoming impact, and the characteristic duration of the final viscous phase of the approach. Additionally, we assess the role of solid compressibility and elucidate why nearly-incompressible solids feature (a) substancial "gliding" prior to contact at the transition between regimes, (b) the largest size of entrapped bubble between the deformed tip of the impactor and the flat surface, and (c) a sudden drop in entrapped bubble radius past the transition between regimes. Finally, we argue that the above time scale ratio (a dimensionless number) can govern the different dynamics reported experimentally for a fluid droplet as a function of its viscosity and surface tension.Comment: 14 pages, 9 figures, 3 table