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The development of the metal structure of a car is carried out throughout the vehicle project using numerical simulation. The simulation of the crash, which is representative of the most serious accidents, is the most expensive computation of the design process. Each simulation takes about 10 h on a high performance computer. The engineers must regularly carry out optimization studies using their crash model. The optimization method used is based on a Design Of Experiments and requires from 3 to 10 crash computations per parameter that are varied in the study. Studies with dozens of parameters, often cost hundreds of computations, that gives a study delay of several weeks. The statistical models model some scalar variables, which are objectives and constraints of the optimization study. This paper focuses on the use of a reduced crash model to perform an optimization study representative of the standard studies, replacing the statistical models created from the DOE method. The proposed method is based on Regression-CUR which combines features selection and a multiple linear regression model, here replaced by a Random Forest model. The aim is to model all the fields simulated by the crash calculation. The replacement of the linear regression by Random Forest has several advantages such as non-linearity, low memory footprint and efficient computing.

Enamel renal syndrome (ERS) is a rare recessive disorder caused by loss-of-function mutations in FAM20A (family with sequence similarity 20 member A, OMIM #611062). Enamel renal syndrome is characterized by amelogenesis imperfecta, delayed or failed tooth eruption, intrapulpal calcifications, gingival overgrowth and nephrocalcinosis. Although gingival overgrowth has consistently been associated with heterotopic calcifications the pathogenesis, structure and interactions of the mineral deposits with the surrounding connective tissue are largely unknown. We here report a novel FAM20A mutation in exon 1 (c.358C > T) introducing a premature stop codon (p.Gln120*) and resulting in a complete loss of FAM20A. In addition to the typical oral findings and nephrocalcinosis, ectopic calcified nodules were also seen in the cervical and thoracic vertebrae regions. Histopathologic analysis of the gingiva showed an enlarged papillary layer associated with aberrant angiogenesis and a lamina propria displaying significant changes in its extracellular matrix composition, including disruption of the collagen I fiber network. Ectopic calcifications were found throughout the connective gingival tissue. Immunomorphological and ultrastructural analyses indicated that the calcification process was associated with epithelial degeneration and transformation of the gingival fibroblasts to chondro/osteoblastic-like cells. Mutant gingival fibroblasts cultures were prone to calcify and abnormally expressed osteoblastic markers such as RUNX2 or PERIOSTIN. Our findings expand the previously reported phenotypes and highlight some aspects of ERS pathogenesis.

The response of a random dynamical system is totally characterized by its probability density function (pdf). However, determining a pdf by a direct approach requires a high numerical cost; similarly, surrogate models such as direct polynomial chaos expansions are not generally efficient, especially around the eigenfrequencies of the dynamical system. In the present study, a new approach based on Pade approximants to obtain moments and pdf of the dynamic response in the frequency domain is proposed. A key difference between the direct polynomial chaos representation and the Pade representation is that the Pade approach has polynomials in both numerator and denominator. For frequency response functions, the denominator plays a vital role as it contains the information related to resonance frequencies, which are uncertain. A Galerkin approach in conjunction with polynomial chaos is proposed for the Pade approximation. Another physics-based approach, utilizing polynomial chaos expansions of the random eigenmodes, is proposed and compared with the proposed Pade approach. It is shown that both methods give accurate results even if a very low degree of the polynomial expansion is used. The methods are demonstrated for two degree-of-freedom system with one and two uncertain parameters.

Designing a random dynamical system requires the prediction of the statistics of the response, knowing the random model of the uncertain parameters. Direct Monte Carlo simulation (MCS) is the reference method for propagating uncertainties but its main drawback is the high numerical cost. A surrogate model based on a polynomial chaos expansion (PCE) can be built as an alternative to MCS. However, some previous studies have shown poor convergence properties around the deterministic eigenfrequencies. In this study, an extended Pade approximant approach is proposed not only to accelerate the convergence of the PCE but also to have a better representation of the exact frequency response, which is a rational function of the uncertain parameters. A second approach is based on the random mode expansion of the response, which is widely used for deterministic dynamical systems. A PCE approach is used to calculate the random modes. Both approaches are tested on an example to check their efficiency.

Damping induced by frictional slipping in assembled structures is always a difficulty in vibration mechanics. Sometimes the cycling movement in riveted or bolted joint is generated by in-plane force field which is directly related to transverse deflection. Since this phenomenon cannot be described by classical plate theory, a general formulation based on von-Karman plate theory is proposed in this study. The response estimation involving damping is conducted with the Krylov-Bogoliubov linearization method (HBM). The notion of non-linear mode is introduced in the context of single mode method and multi-mode method. The influence of mode shape change on forced response is also analyzed.

Green tea is widely used as a &lsquo, &rsquo, healthy&rsquo, beverage due to its high level of antioxidant polyphenol compounds. However tea is also known to contain significant amount of oxalate. The objective was to determine, in a cross-sectional observational study among a population of 273 hypercalciuric stone-formers referred to our center for metabolic evaluation, whether daily green tea drinkers (n = 41) experienced increased stone risk factors (especially for oxalate) compared to non-drinkers. Stone risk factors and stone composition were analyzed according to green tea status and sex. In 24-h urine collection, the comparison between green tea drinkers and non-drinkers showed no difference for stone risk factors such as urine oxalate, calcium, urate, citrate, and pH. In females, the prevalence of calcium oxalate dihydrate (COD) and calcium phosphate stones, assessed by infrared analysis (IRS) was similar between green tea drinkers and non-drinkers, whereas prevalence of calcium oxalate monohydrate (COM) stones was strikingly decreased in green tea drinkers (0% vs. 42%, p = 0.04), with data in accordance with a decreased oxalate supersaturation index. In males, stone composition and supersaturation indexes were similar between the two groups. Our data show no evidence for increased stone risk factors or oxalate-dependent stones in daily green tea drinkers.

Resume L’email dentaire est un materiau modele pour appliquer une approche physicochimique. Des pathologies ou l’environnement peuvent induire une destruction, une degradation ou des malformations amelaires. Contrairement a la plupart des autres tissus biologiques mineralises, l’email est incapable de se regenerer naturellement. Comprendre les mecanismes de degradation de l'email presente un interet scientifique et economique. Cette revue se propose de donner un apercu bibliographique des travaux des dix dernieres annees. Les etudes de l'email par des techniques physiques ou chimiques classiques et disponibles ont ete presentees et commentees a la lumiere d'exemples recents. L'interface entre la physique, la chimie et la science orale est tres active depuis plusieurs decennies, avec un important regain au cours de ces dernieres annees en raison de l'acces a des techniques tres sensibles de la science des materiaux.

The JJ stent constitutes a medical device extensively used nowadays by urologists in more than 40,000 patients per year in France. In this investigation, we characterize the surface state and the elastic properties of a set of JJ stents on which pathological calcifications are present. These encrustations have been identified by Fourier transform infrared spectroscopy. A surface examination by scanning electron microscopy indicates the existence of defects. The striking point of these observations is that black marks, present at the surface to help urologists during the operation, significantly alter the surface and may serve as nucleation centers. Moreover, elastic properties are not preserved when the indwelling time of JJ stents is longer than 12 wk. Such data may help industrial companies to develop new JJ stents, which avoid the formation of encrustations and help the clinician to optimize the lifetime of JJ stents in patients.

Hundred kidney stones obtained from the University Hospital of Ouagadougou (Burkina Faso) were finally characterized by a panel of complementary spectroscopic and diffraction tools. The most surprising result is the high occurrence of opaline silica as a component in these kidney stones. Opaline silica is a scarce mineral phase in renal calcification; however, we found that at least 48% of the stones had a detectable proportion of silica. SEM images demonstrate the presence of micrometric objects (of spheroidal shape) in close association with monohydrated calcium oxalate crystals. X-ray fluorescence, XRD and 29Si solid state MAS NMR demonstrate unambiguously the presence of amorphous silica, whose composition is comparable to that of natural opals. As NMR is a local spectroscopic probe, other nuclei can be probed. We demonstrate that traces of aluminium are present in the kidney stones by using 27Al solid state MAS NMR. These experiments may offer the first clues of pathological processes that are responsible for these stones., Cent calculs rénaux obtenus du CHU de Ouagadougou (Burkina Faso) ont été caractérisés par une série d'outils spectroscopiques et de diffraction complémentaires. Le résultat le plus marquant a été la très haute prévalence de la silice opaline comme composant de ces calculs. La silice opaline est un composant rare des calculs rénaux. Cependant, nous l'avons trouvée dans près de 48% des calculs, dans des proportions suffisantes pour être détectables par analyse infrarouge. Les images au MEB démontrent la présence d'objets micrométriques (de forme sphérique) en association intime avec des cristaux d'oxalate de calcium monohydraté. La fluorescence des rayons X, la diffraction des rayons X et la RMN du solide du 29Si démontrent sans ambiguïté la présence de silice amorphe, de manière comparable au cas des opales naturelles. Comme la RMN est une sonde spectroscopique locale, d'autres noyaux peuvent être détectés. Nous avons ainsi démontré que des traces d'aluminium sont présentes dans les calculs rénaux étudiés en utilisant la RMN du solide du noyau 27 Al. Ces expériences peuvent offrir les premiers éléments de réponse concernant le processus pathologique conduisant à la formation de ces calculs.

Dentin differs in composition and morphology depending on its anatomical location and circumstances of formation (1). Circumpulpal dentinogenesis patterns, either in a physiological or reparative c...

Controlling the mechanical environment in bioreactors represents a key element in the reactors' optimization. Positive effects of fluid flow in three-dimensional bioreactors have been observed, but local stresses at cell scale remain unknown. These effects led to the development of numerical tools to assess the micromechanical environment of cells in bioreactors. Recently, new possible scaffold geometry has emerged: granular packings. In the present study, the primary goal was to compare the efficiency of such a scaffold to the other ones from literature in terms of wall shear stress levels and distributions. To that aim, three different types of granular packings were generated through discrete element method, and computational fluid dynamics was used to simulate the flow within these packings. Shear stress levels and distributions were determined. A linear relationship between shear stress and inlet velocity was observed, and its slope was similar to published data. The distributions of normalized stress were independent of the inlet velocity and were highly comparable to those of widely used porous scaffolds. Granular packings present similar features to more classical porous scaffolds and have the advantage of being easy to manipulate and seed. The methods of this work are generalizable to the study of other granular packing configurations.

L’email est un tissu unique chez les vertebres, acellulaire, forme sur un echafaudage matriciel labile et hypermineralise. Les cellules epitheliales responsables de sa formation sont les ameloblastes. Ces derniers secretent des proteines matricielles, secondairement detruites pendant la mineralisation. Cette sequence ordonnee implique que toute perturbation genetique ou environnementale produira une anomalie de l’email indelebile et reconnaissable, dont la specificite permettra d’identifier le processus cellulaire affecte. Les dents touchees permettront donc un diagnostic retrospectif de l’evenement teratogene. Les avancees du domaine font des defauts de l’email un outil pour les diagnostics moleculaires. Les multiples fonctions des peptides amelaires sont identifiees pas a pas, des mecanismes physico-chimiques de la mineralisation a la signalisation cellulaire, constituant une source d’innovations en medecine regenerative.

Background and objective: FAM20A gene mutations result in enamel renal syndrome (ERS) associated with amelogenesis imperfecta (AI), nephrocalcinosis, gingival fibromatosis, and impaired tooth eruption. FAM20A would control the phosphorylation of enamel peptides and thus enamel mineralization. Here, we characterized the structure and chemical composition of unerupted tooth enamel from ERS patients and healthy subjects. Methods: Tooth sections were analyzed by Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), X-Ray Diffraction (XRD), and X-Ray Fluorescence (XRF). Results: SEM revealed that prisms were restricted to the inner-most enamel zones. The bulk of the mineralized matter covering the crown was formed by layers with varying electron-densities organized into lamellae and micronodules. Tissue porosity progressively increased at the periphery, ending with loose and unfused nanonodules also observed in the adjoining soft tissues. Thus, the enamel layer covering the dentin in all ERS patients (except a limited layer of enamel at the dentino-enamel junction) displayed an ultrastructural globular pattern similar to one observed in ectopic mineralization of soft tissue, notably in the gingiva of Fam20a knockout mice. XRD analysis confirmed the existence of alterations in crystallinity and composition (vs. sound enamel). XRF identified lower levels of calcium and phosphorus in ERS enamel. Finally, EDS confirmed the reduced amount of calcium in ERS enamel, which appeared similar to dentin. Conclusion: This study suggests that, after an initial normal start to amelogenesis, the bulk of the tissue covering coronal dentin would be formed by different mechanisms based on nano- to micro-nodule aggregation. This evocated ectopic mineralization process is known to intervene in several soft tissues in FAM20A gene mutant.

The response of a random dynamical system is totally characterized by its probability density function (pdf). However, determining a pdf by a direct approach requires a high numerical cost; similarly, surrogate models such as direct polynomial chaos expansions are not generally efficient, especially around the eigenfrequencies of the dynamical system. In the present study, a new approach based on Padé approximants to obtain moments and pdf of the dynamic response in the frequency domain is proposed. A key difference between the direct polynomial chaos representation and the Padé representation is that the Padé approach has polynomials in both numerator and denominator. For frequency response functions, the denominator plays a vital role as it contains the information related to resonance frequencies, which are uncertain. A Galerkin approach in conjunction with polynomial chaos is proposed for the Padé approximation. Another physics-based approach, utilizing polynomial chaos expansions of the random eigenmodes, is proposed and compared with the proposed Padé approach. It is shown that both methods give accurate results even if a very low degree of the polynomial expansion is used. The methods are demonstrated for two degree-of-freedom system with one and two uncertain parameters.

Microarray analysis of odontoblastic cells treated with sodium fluoride has identified the asporin gene as a fluoride target. Asporin is a member of the small leucine-rich repeat proteoglycan/protein (SLRP) family that is believed to be important in the mineralization process. In this study, asporin expression and distribution were investigated by systematic analysis of dentin and enamel, with and without fluoride treatment. Specific attention was focused on a major difference between the two mineralized tissues: the presence of a collagenous scaffold in dentin, and its absence in enamel. Normal and fluorotic, continually growing incisors from Wistar rats treated with 2.5 to 7.5 mM sodium fluoride (NaF) were studied by immunochemistry, in situ hybridization, Western blotting, and RT-qPCR. Asporin was continuously expressed in odontoblasts throughout dentin formation as expected. Asporin was also found, for the first time, in dental epithelial cells, particularly in maturation-stage ameloblasts. NaF decreased asporin expression in odontoblasts and enhanced it in ameloblasts, both in vivo and in vitro. The inverse response in the two cell types suggests that the effector, fluoride, is a trigger that elicits a cell-type-specific reaction. Confocal and ultrastructural immunohistochemistry evidenced an association between asporin and type 1 collagen in the pericellular nonmineralized compartments of both bone and dentin. In addition, transmission electron microscopy revealed asporin in the microenvironment of all cells observed. Thus, asporin is produced by collagen-matrix-forming and non-collagen-matrix-forming cells but may have different effects on the mineralization process. A model is proposed that predicts impaired mineral formation associated with the deficiency and excess of asporin. © 2014 American Society for Bone and Mineral Research.

International audience; This paper proposes two methods based on the Polynomial Chaos to carry out the stochastic study of a self-excited non-linear system with friction which is commonly used to represent brake-squeal phenomenon. These methods are illustrated using three uncertain configurations and validated using comparison with Monte Carlo simulation results. First, the stability of the static equilibrium point is examined by computing stochastic eigenvalues. Then, for unstable ranges of the equilibrium point, a constrained harmonic balance method is developed to determine subsequent limit cycles in the deterministic case; it is then adapted to the stochastic case. This demonstrates the effectiveness of the methods to fit complex eigenmodes as well as limit cycles dispersion with a good accuracy.

International audience; Crystal formation in kidney tissue is increasingly recognized as a major cause of severe or acute renal failure. Kidney biopsies are currently performed and analyzed using different staining procedures. Unfortunately, none of these techniques are able to distinguish the different Ca phosphates (e.g., amorphous or nanostructured Ca phosphate apatite, octacalcium phosphate, brushite…) or Ca oxalates (whewellite and weddellite). Moreover, the crystal’s morphology, a structural parameter proven as a major information to the clinician regarding kidney stones, is not taken into account. Such major limitations call for a different research approach, based on physicochemical techniques. Here we propose classical observations through field-emission scanning electron microscopy experiments combined with energy dispersive spectroscopy as well as measurements through Raman and μFourier transform Infra-Red Spectroscopy. If necessary, in the case of microcrystals, observations using cutting edge technology such as Synchrotron Radiation (SR) – FTIR or SR-UV visible spectroscopy can be subsequently performed on the same sample. Taken together this set of diagnostic tools will help clinicians gather information regarding the nature and the spatial distribution at the subcellular scale of different chemical phases present in kidney biopsies as well as on the crystal morphology and therefore obtain more precise diagnosis.

International audience; The JJ stent constitutes a medical device extensively used nowadays by urologists in more than 40,000 patients per year in France. In this investigation, we characterize the surface state and the elastic properties of a set of JJ stents on which pathological calcifications are present. These encrustations have been identified by Fourier transform infrared spectroscopy. A surface examination by scanning electron microscopy indicates the existence of defects. The striking point of these observations is that black marks, present at the surface to help urologists during the operation, significantly alter the surface and may serve as nucleation centers. Moreover, elastic properties are not preserved when the indwelling time of JJ stents is longer than 12 wk. Such data may help industrial companies to develop new JJ stents, which avoid the formation of encrustations and help the clinician to optimize the lifetime of JJ stents in patients.; Les sondes JJ constituent un dispositif médical largement utilisé de nos jours par les urologues chez plus de 40 000 patients par an en France. Dans cette étude, nous caractérisons l'état de surface et les propriétés élastiques d'un ensemble de sondes JJ sur lesquelles des calcifications pathologiques sont présentes. Ces incrustations ont été identifiées par spectrophotométrie infrarouge à transformée de Fourier. Un examen de surface par microscopie électronique à balayage indique l'existence de défauts. Le point marquant de ces observations vient du fait que les marques noires présentes à la surface pour aider les urologues pendant l'opération modifient de manière significative la surface et peuvent servir de sites de nucléation. De plus, les propriétés élastiques ne sont pas conservées lorsque le temps de séjour de ces sondes chez le patient est supérieur à 12 semaines. Ces données peuvent donc aider les industriels à développer de nouvelles sondes JJ évitant la formation d'incrustations et aider le clinicien à optimiser la durée de vie des sondes JJ chez les patients.