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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.

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.

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.

Introduction Odontoblasts are responsible for the synthesis of dentin throughout the life of the tooth. Tooth pulp tissue may undergo a pathologic process of mineralization, resulting in formation of pulp stones. Although the prevalence of pulp stones in dental caries is significant, their development and histopathology are poorly understood, and their precise composition has never been established. The aim of the present study was to investigate the physicochemical properties of the mineralized tissues of teeth to elucidate the pathologic origin of pulp stones. Methods Areas of carious and healthy dentin of 8 decayed teeth intended for extraction were analyzed and compared. In addition, 6 pulp stones were recovered from 5 teeth requiring root canal treatment. The samples were embedded in resin, sectioned, and observed by scanning electron microscopy and energy-dispersive spectroscopy. X-ray diffraction was performed to identify phases and crystallinity. X-ray fluorescence provided information on the elemental composition of the samples. Results Pulp stones showed heterogeneous structure and chemical composition. X-ray diffraction revealed partially carbonated apatite. X-ray fluorescence identified P, Ca, Cu, Zn, and Sr within dentin and pulp stones. Zn and Cu concentrations were higher in pulp stones and carious dentin compared with healthy dentin. Conclusions Pulpal cells produce unstructured apatitic mineralizations containing abnormally high Zn and Cu levels.

A dynamical uncertain system is studied in this paper. Two kinds of uncertainties are addressed, where the uncertain parameters are described through random variables and/or fuzzy variables. A general framework is proposed to deal with both kinds of uncertainty using a polynomial chaos expansion (PCE). It is shown that fuzzy variables may be expanded in terms of polynomial chaos when Legendre polynomials are used. The components of the PCE are a solution of an equation that does not depend on the nature of uncertainty. Once this equation is solved, the post-processing of the data gives the moments of the random response when the uncertainties are random or gives the response interval when the variables are fuzzy. With the PCE approach, it is also possible to deal with mixed uncertainty, when some parameters are random and others are fuzzy. The results provide a fuzzy description of the response statistical moments.

International audience; The generalized use of physical methods, X-ray diffraction and Fourier transform infrared spectroscopy (FTIR) decisively improved urinary stone analysis by allowing to accurately identify the chemical nature, crystalline phases and relative proportions of stone constituents. Such compositional analysis is sufficient to identify stone diseases involving a single specific component such as cystine, 2,8-dihydroxyadenine (DHA), struvite, uric acid, ammonium hydrogen urate or a drug. However, for common calcium nephrolithiasis, which represents by far the largest part of urinary stones throughout the world, the simple identification of calcium oxalate (CaOx) and/or calcium phosphate (CaP) as constituents provides incomplete etiologic information because a same elemental stone composition may result from different lithogenic processes.A more comprehensive method combining careful morphologic examination of the surface and the section of stones with detailed FTIR analysis of the nature, location, crystalline phases and a respective proportion of stone constituents, therefore termed ‘morpho-constitutional’ analysis, as used in our laboratory for four decades provides more complete etiologic information. In common idiopathic CaOx nephrolithiasis, the predominance of the monohydrate form (COM) was shown to be associated with elevated urine Ox concentration, whereas the dihydrate form (COD) was associated with hypercalciuria, thus orienting dietary and/or pharmacological intervention. A major contribution of the method is to immediately orient the diagnosis of rare, but severe, diseases leading to a loss of renal function, when stone analysis reveals a peculiar morphology of common constituents. The most salient examples are the type Ic morphology of COM stones, pathognomonic of primary hyperoxaluria, type Ie morphology, which is highly suggestive of absorptive hyperoxaluria as seen in inflammatory bowel diseases and pathologies inducing steatorrhea, type IIId morphology of ammonium urate stones, which orientates towards chronic diarrhea with dietary imbalance and loss of electrolytes, and type IVa2 morphology of carbapatite, specific of distal renal tubular acidosis of congenital or acquired origin, and distinctive aspect of 2,8-DHA stones. In conclusion, the proposed morpho-constitutional method should be recommended for routine stone analysis, inasmuch as it is simple, rapid, reliable, clinically relevant and cost-effective.

International audience; Even though calcifications in thyroid nodules constitute a common finding in imaging and histopathology, and also may occur in both benign and malignant thyroid disease, their clinical importance remains unclear. A way to establish a possible relationship between their presence and the associated pathology may be given through a precise description of their chemical composition. In order to attain this goal, last generation Field Effect Scanning Electron Microscopy (FE-SEM) and classical Fourier Transform Infra Red (FT-IR) experiments have been performed on thyroid calcifications. Calcifications corresponding to different pathologies have been considered, including Graves' disease, papillary carcinoma or multinodular goiter. The complete set of experiments shows for the first time a chemical diversity of pathological calcifications but no correlation between the chemical composition of the pathological calcifications and the disease.

International audience; 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.

This paper investigates the fundamental nature of the polynomial chaos (PC) response of dynamic systems with uncertain parameters in the frequency domain. The eigenfrequencies of the extended matrix arising from a PC formulation govern the convergence of the dynamic response. It is shown that, in the particular case of uncertainties and with Hermite and Legendre polynomials, the PC eigenfrequencies are related to the roots of the underlying polynomials, which belong to the polynomial chaos set used to derive the polynomial chaos expansion. When Legendre polynomials are used, the PC eigenfrequencies remain in a bounded interval close to the deterministic eigenfrequencies because they are related to the roots of a Legendre polynomial. The higher the PC order, the higher the density of the PC eigenfrequencies close to the bounds of the interval, and this tends to smooth the frequency response quickly. In contrast, when Hermite polynomials are used, the PC eigenfrequencies spread from the deterministic eigenfrequencies (the highest roots of the Hermite polynomials tend to infinity when the order tends to infinity). Consequently, when the PC number increases, the smoothing effect becomes inefficient.

International audience; OBJECTIVE To underline peculiar composition of kidney stones and to propose an epidemiologic study of urinary stones in West African countries, where epidemiologic studies are scarce. Only few data are available regarding stone composition in sub-Saharan countries. Recently, a set of 100 stones consecutively removed by surgery in the Department of Urology of the University Hospital of Ouagadougou in Burkina Faso were collected for physical analysis, which provided the opportunity to obtain an epidemiologic profile of stone composition in this country. MATERIALS AND METHODS A total of 100 stones from 64 men, 22 women, 10 boys, and four girls were analyzed by morphologic examination, infrared spectroscopy, and electron microscopy in our laboratory. The results were considered by sex and separately for adults and children. RESULTS Sixty-five percent of the 100 stones contained calcium oxalate as the main component. Interestingly, the second main component was opaline silica (18%). Furthermore, opaline silica was identified in any proportion in 48% of the stones. The prevalence was sex and age dependent. Opaline silica was detected as the main component in 42% of the nuclei, which underlines its role as one of the main components involved in the initiation of calculi in this country. CONCLUSION For the first time, a dramatically high occurrence of a ``scarce'' urinary stone component, namely opaline silica, was reported in a series of consecutive calculi from a single country. We propose that a regular consumption of clay could be the origin of this phenomenon in these populations.

International audience; no abstract

Resume Objectif Donner une vue synthetique des phases cristallines existentes dans les calculs prostatiques, en insistant sur la diversite physico-chimique de ces phases. Materiel et methode Un ensemble de 32 calculs prostatiques provenant de patients traites dans differents hopitaux ont ete analyses par spectroscopie infrarouge a transformee de Fourier (IR-TF) et par microscopie electronique a balayage (MEB). Resultats L’analyse par infrarouge a permis de determiner les phases et leurs proportions au sein de chaque calcul prostatique. La topologie de ces phases a egalement ete etudiee par MEB. L’ensemble de ces donnees a mis en evidence la preponderance des phosphates calciques, majoritaires dans 90,7 % des cas, mais aussi l’existence de nouvelles phases chimiques jusqu’ici non-repertoriees dans la litterature, telles que la brushite ou le phosphate octocalcique pentahydrate. Conclusion L’analyse des calculs prostatiques a revele une diversite chimique et structurale plus grande que celle rapportee a ce jour. Comme pour les calculs urinaires, il pourrait etre interessant sur le plan clinique, de rechercher les correlations entre les caracteristiques morpho-constitutionnelles des calculs prostatiques et les facteurs etio-pathogeniques.

Wave propagation features in random guided elastic media are considered in this paper. A formulation named stochastic wave finite element (SWFE) is offered. This formulation allows wave characteristics definition by means of a stochastic finite element model. The case of spatially homogeneous random properties is dealt with, through a parametric probabilistic technique. Numerical experiments show the effectiveness of the proposed approach to predict the statistics of guided wave propagation characteristics (means and standard deviations) when compared to Monte Carlo calculations.

Enhanced photocatalytic properties of oriented films of rutile nanorods have previously been observed when the polarization of UV light is parallel to the rutile c axis. To reach a better understan...

Enamel is a unique tissue in vertebrates, acellular, formed on a labile scaffolding matrix and hypermineralized. The ameloblasts are epithelial cells in charge of amelogenesis. They secrete a number of matrix proteins degraded by enzymes during enamel mineralization. This ordered cellular and extracellular events imply that any genetic or environmental perturbation will produce indelible and recognizable defects. The specificity of defects will indicate the affected cellular process. Thus, depending on the specificity of alterations, the teratogenic event can be retrospectively established. Advances in the field allow to use enamel defects as diagnostic tools for molecular disorders. The multifunctionality of enamel peptides is presently identified from their chemical roles in mineralization to cell signaling, constituting a source of concrete innovations in regenerative medicine.

International audience; PurposeCalcium stones represent 85% to 90% of all urinary calculi, including various crystalline compositions and etiological conditions. Calcium phosphate accounts for 10% to 15% of cases. These stones are mainly related to 3 groups of risk factors, including calcium or phosphate metabolism disturbance, renal acidification defects and urinary tract infection. Identifying the stone etiology often requires extensive metabolic evaluation. We assessed whether stone analysis including morphological typing in addition to stone composition could be a valuable help for diagnosis.Materials and MethodsOf 60,564 stones analyzed by morphological examination and infrared spectroscopy at our laboratory 6,439 (10.6%) were mainly composed of carbapatite. Of these stone 1,093 patients were included in study who had an available etiological diagnosis and stones containing at least 70% of calcium phosphate without struvite.ResultsOf the 1,093 calcium phosphate stones 12.8% showed a peculiar morphology termed IVa2, characterized by a smooth aspect and a glazed brown-yellow appearance with tiny cracks. IVa2 morphology was observed in 96.1% of stones associated with inherited distal renal tubular acidosis. In contrast, the other stones of similar composition but different morphology were related to distal renal tubular acidosis in only 3.9% of cases. In addition, IVa2 stones were found in 65% of calcium phosphate stone formers associated with Sjögren syndrome and in 35% of calcium phosphate stones in patients with medullary sponge kidney. These 2 conditions are related to a mild to moderate distal acidification defect.ConclusionsIdentifying IVa2 stone morphology is clinically relevant because it should prompt clinicians to search for complete or incomplete distal acidosis and initiate specific therapy to decrease recurrence.

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.

Osteoporosis represents a major public health problem through its association with fragility fractures. The public health burden of osteoporotic fractures will rise in future generations, due in part to an increase in life expectancy. Strontium-based drugs have been shown to increase bone mass in postmenopausal osteoporosis patients and to reduce fracture risk but the molecular mechanisms of the action of these Sr-based drugs are not totally elucidated. The local environment of Sr2+cations in biological apatites present in pathological and physiological calcifications in patients without such Sr-based drugs has been assessed. In this investigation, X-ray absorption spectra have been collected for 17 pathological and physiological calcifications. These experimental data have been combined with a set of numerical simulations using theab initioFEFF9X-ray spectroscopy program which takes into account possible distortion and Ca/Sr substitution in the environment of the Sr2+cations. For selected samples, Fourier transforms of the EXAFS modulations have been performed. The complete set of experimental data collected on 17 samples indicates that there is no relationship between the nature of the calcification (physiological and pathological) and the adsorption mode of Sr2+cations (simple adsorption or insertion). Such structural considerations have medical implications. Pathological and physiological calcifications correspond to two very different preparation procedures but are associated with the same localization of Sr2+versusapatite crystals. Based on this study, it seems that for supplementation of Sr at low concentration, Sr2+cations will be localized into the apatite network.

This paper addresses the problem of mechanical systems in which parameters are uncertain and bounded. Interval calculation is used to find an envelope of transfer functions for mechanical systems modelled with finite elements. Within this context, a new formulation has been developed for finite element problems involving bounded parameters, to avoid the problems of overestimation. An iterative algorithm is introduced, which leads to a conservative solution for linear mechanical problems. A method to ensure the convergence of this algorithm is also proposed. This new algorithm has been tested on simple mechanical systems, and leads to a conservative envelope of the transfer functions.

International audience; Plasma urate levels are higher in humans than rodents (240-360 vs. ∼30 μM) because humans lack the liver enzyme uricase. High uricemia in humans may protect against oxidative stress, but hyperuricemia also associates with the metabolic syndrome, and urate and uric acid can crystallize to cause gout and renal dysfunctions. Thus, hyperuricemic animal models to study urate-induced pathologies are needed. We recently generated mice with liver-specific ablation of Glut9, a urate transporter providing access of urate to uricase (LG9KO mice). LG9KO mice had moderately high uricemia (∼120 μM). To further increase their uricemia, here we gavaged LG9KO mice for 3 days with inosine, a urate precursor; this treatment was applied in both chow- and high-fat-fed mice. In chow-fed LG9KO mice, uricemia peaked at 300 μM 2 h after the first gavage and normalized 24 h after the last gavage. In contrast, in high-fat-fed LG9KO mice, uricemia further rose to 500 μM. Plasma creatinine strongly increased, indicating acute renal failure. Kidneys showed tubule dilation, macrophage infiltration, and urate and uric acid crystals, associated with a more acidic urine. Six weeks after inosine gavage, plasma urate and creatinine had normalized. However, renal inflammation, fibrosis, and organ remodeling had developed despite the disappearance of urate and uric acid crystals. Thus, hyperuricemia and high-fat diet feeding combined to induce acute renal failure. Furthermore, a sterile inflammation caused by the initial crystal-induced lesions developed despite the disappearance of urate and uric acid crystals.

International audience; This paper proposes numerical developments based on polynomial chaos (PC) expansions to process stochastic eigenvalue problems efficiently. These developments are applied to the problem of linear stability calculations for a simplified brake system: the stability of a finite element model of a brake is investigated when its friction coefficient or the contact stiffness are modeled as random parameters. Getting rid of the statistical point of view of the PC method but keeping the principle of a polynomial decomposition of eigenvalues and eigenvectors, the stochastic space is decomposed into several elements to realize a low degree piecewise polynomial approximation of these quantities. An approach relying on continuation principles is compared to the classical dichotomy method to build the partition. Moreover, a criterion for testing accuracy of the decomposition over each cell of the partition without requiring evaluation of exact eigenmodes is proposed and implemented. Several random distributions are tested, including a uniform-like law for description of friction coefficient variation. Results are compared to Monte Carlo simulations so as to determine the method accuracy and efficiency. Some general rules relative to the influence of the friction coefficient or the contact stiffness are also inferred from these calculations.

Contains fulltext : 118931.pdf (Publisher’s version ) (Open Access) BACKGROUND: basic calcium phosphate (BCP) crystals are commonly found in osteoarthritis (OA) and are associated with cartilage destruction. BCP crystals induce in vitro catabolic responses with the production of metalloproteases and inflammatory cytokines such as interleukin-1 (IL-1). In vivo, IL-1 production induced by BCP crystals is both dependant and independent of NLRP3 inflammasome. We aimed to clarify 1/ the role of BCP crystals in cartilage destruction and 2/ the role of IL-1 and NLRP3 inflammasome in cartilage degradation related to BCP crystals. METHODOLOGY PRINCIPAL FINDINGS: synovial membranes isolated from OA knees were analysed by alizarin Red and FTIR. Pyrogen free BCP crystals were injected into right knees of WT, NLRP3 -/-, ASC -/-, IL-1alpha -/- and IL-1beta-/- mice and PBS was injected into left knees. To assess the role of IL-1, WT mice were treated by intra-peritoneal injections of anakinra, the IL-1Ra recombinant protein, or PBS. Articular destruction was studied at d4, d17 and d30 assessing synovial inflammation, proteoglycan loss and chondrocyte apoptosis. BCP crystals were frequently found in OA synovial membranes including low grade OA. BCP crystals injected into murine knee joints provoked synovial inflammation characterized by synovial macrophage infiltration that persisted at day 30, cartilage degradation as evidenced by loss of proteoglycan staining by Safranin-O and concomitant expression of VDIPEN epitopes, and increased chondrocyte apoptosis. BCP crystal-induced synovitis was totally independent of IL-1alpha and IL-1beta signalling and no alterations of inflammation were observed in mice deficient for components of the NLRP3-inflammasome, IL-1alpha or IL-1beta. Similarly, treatment with anakinra did not prevent BCP crystal effects. In vitro, BCP crystals elicited enhanced transcription of matrix degrading and pro-inflammatory genes in macrophages. CONCLUSIONS SIGNIFICANCE: intra-articular BCP crystals can elicit synovial inflammation and cartilage degradation suggesting that BCP crystals have a direct pathogenic role in OA. The effects are independent of IL-1 and NLRP3 inflammasome.

International audience; Prostatic stones are a common condition in older men in industrialized countries. However, aging appears not to be the unique pathogenesis of these calcifications. Our morpho-constitutional investigation of 23 stone samples suggested that infection has a significant role in the lithogenic process of prostate calcifications, even without detection of infection by clinical investigation. Most stones (83%) showed bacterial imprints and/or chemical composition, suggestive of a long-term infection process. Chronic infection may induce persistent inflammation of the tissue and secondarily, a cancerization process within a few years. Thus, the discovery of prostate calcifications by computerized tomodensitometry, for example, might warrant further investigation and management to search for chronic infection of the prostate gland.

International audience; We aimed to examine the presence of Zn, a trace element, in osteoarthritis (OA) cartilage and meniscus from patients undergoing total knee joint replacement for primary OA. We mapped Ca2+ and Zn2+ at the mesoscopic scale by X-ray fluorescence microanalysis (μX-ray) to determine the spatial distribution of the 2 elements in cartilage, μX-ray absorption near edge structure spectroscopy to identify the Zn species, and μX-ray diffraction to determine the chemical nature of the calcification. Fourier transform infrared spectroscopy was used to determine the chemical composition of cartilage and meniscus. Ca2+ showed a heterogeneous spatial distribution corresponding to the calcifications within cartilage (or meniscus) or at their surface. At least 2 Zn2+ species were present: the first may correspond to Zn embedded in protein (different Zn metalloproteins are known to prevent calcification in biological tissues), and the second may be associated with a Zn trap in or at the surface of the calcification. Calcification present in OA cartilage may significantly modify the spatial distribution of Zn; part of the Zn may be trapped in the calcification and may alter the associated biological function of Zn metalloproteins.

International audience; This paper proposes to use a polynomial chaos expansion approach to compute stochastic complex eigenvalues and eigenvectors of structures including damping or gyroscopic effects. Its application to a finite element rotor model is compared to Monte Carlo simulations. This lets us validate the method and emphasize its advantages. Three different uncertain configurations are studied. For each, a stochastic Campbell diagram is proposed and interpreted and critical speeds dispersion is evaluated. Furthermore, an adaptation of the Modal Accordance Criterion is proposed in order to monitor the eigenvectors dispersion.

National audience; See http://hal.archives-ouvertes.fr/docs/00/59/29/13/ANNEX/r_J7OGBX5D.pdf

Revisiting the chemical diversity of the crystalline phases of prostatic calculi by means of SEM and FT-IR analysis.A set of 32 prostatic calculi has been studied by FT-IR and SEM.FT-IR analysis has determined the chemical composition of each prostatic calculus and the SEM observation has described the morphology of the calculi surfaces and layers. Infrared analysis revealed that 90.7% of the stones were mainly composed of calcium phosphates. However, several mineral phases previously not reported in prostatic calculi were observed, as brushite or octocalcium phosphate pentahydrate.Prostatic calculi exhibited a diversity of crystalline composition and morphology. As previously reported for urinary calculi, relationships between composition and morphology of prostatic stones and étiopathogenic conditions could be of interest in clinical practice.

International audience; Spinodal decomposition in the TiO2-SnO2 system produces TiO2 rich/SnO2 rich nano-wide lamellae. The high density of coherent interfaces is expected to reduce thermal conductivity of the ceramic without blocking electron transport. These semiconductors could therefore be candidates for environmental friendly oxide thermo-electrics. However, dense materials are difficult to obtain by conventional sintering from a mixture of TiO2 and SnO2 powders due to evaporation of tin oxide. The article presents a novel route to produce, by aqueous co-precipitation, Ti0.5Sn0.5O2 nanopowders as precursors for dense ceramics. The nanostructure developed by spinodal decomposition inside the grains of the as obtained dense Ti0.5Sn0.5O2 ceramic is shown to be comparable to that of porous Ti0.5Sn0.5O2 ceramic obtained by conventional method.

In most industrialized countries, different epidemiologic studies show that chronic renal failure is dramatically increasing. Such major public health problem is a consequence of acquired systemic diseases such as type II diabetes, which is now the first cause for end stage renal failure. Furthermore, lithogenic diseases may also induce intratubular crystallization, which may finally result in end-stage renal failure (ESRF). Up to now, such rare diseases are often misdiagnosed. In this study, based on twenty four biopsies, we show that SR µFTIR (Synchrotron Radiation-µFourier transform infrared) spectroscopy constitutes a significant opportunity to characterize such pathological µcalcifications giving not only their chemical composition but also their spatial distribution in the tissues. This experimental approach offers new opportunities to the clinicians to describe at the cell level the physico-chemical processes leading to the formation of the pathological calcifications which lead to ESRF.

TiO2 rutile nanorods of average length L = 160 +/- 40 nm and average diameter D = 15 +/- 5 nm have been synthesized through a seed-mediated growth process by TiCl4 hydrolysis in concentrated acidic solution, inspired of a Chimie Douce method. These nanorods were dispersed in water to yield stable (aggregation-free) colloidal aqueous suspensions. At volume fractions phy > 3%, the suspensions spontaneously display a phase separation into an isotropic liquid phase and a liquid-crystalline phase identified as nematic by X-ray scattering. At phy > 12 %, the suspensions form a nematic single phase, with large order parameter, S = 0.75 +/- 0.05. Very well aligned rutile films on glass substrate were produced by spin-coating and their photocatalytic properties were examined by monitoring the decomposition of methylene blue under UV-light. We found that UV-light polarized along the quadratic axis of the rutile nanorods was most efficient for this photocatalytic reaction. Some experiments of conduction have been performed. TiO2 rutile is a semi conductor with, for the bulk, a gap of around 3 eV. As in the photocatalytic studies, the polarized UV-light has a huge influence on the charge transport. A Schottky diode behaviour has been observed and explained. Irradiation in the visible spectrum has been shown to have no consequence on the properties of conduction. Rutile films have been also characterized to estimate the correction for the gap of anisotropic nanoparticles. Finally, a thermal study and a comparison with a monocrystal have been done.; Les phases cristal-liquides minérales se situent à l'interface de la chimie colloïdale, de la physique de la matière molle et de la physique du solide. Largement utilisées dans l'industrie, les nanoparticules de TiO2 de variété rutile sont des candidates de choix à une étude visant à relier propriétés du matériau massif et propriétés d'une assemblée orientée de petits objets anisotropes.Le travail présenté montrera comment il est possible d'élaborer par Chimie Douce des nanoparticules anisotropes afin d'obtenir en milieu aqueux une mésophase, de nature nématique, et de la caractériser. De plus, des suspensions de bâtonnets, même relativement diluées, s'orientent sous cisaillement, ce qui permet de produire par spin-coating des films anisotropes. Ces films sont des échantillons de choix pour effectuer des mesures, sous irradiation ultraviolette, de photocatalyse d'espèces organiques dissoutes ou encore de photoconduction. Ces mesures peuvent être comparées avec les résultats obtenus à l'aide d'un monocristal de TiO2 présentant les mêmes facettes cristallographique [110] que les nanoparticules.Un film orienté de bâtonnets de rutile présente naturellement des propriétés anisotropes. En outre, nous avons mis en évidence une forte dépendance des propriétés catalytiques et de la conductivité électronique avec la polarisation de l'irradiation ultra-violette. Nous montrerons dans quelle mesure la théorie des bandes permet d'expliquer ces effets.

TiO2 rutile nanorods of average length L = 160 +/- 40 nm and average diameter D = 15 +/- 5 nm have been synthesized through a seed-mediated growth process by TiCl4 hydrolysis in concentrated acidic solution, inspired of a Chimie Douce method. These nanorods were dispersed in water to yield stable (aggregation-free) colloidal aqueous suspensions. At volume fractions phy > 3%, the suspensions spontaneously display a phase separation into an isotropic liquid phase and a liquid-crystalline phase identified as nematic by X-ray scattering. At phy > 12 %, the suspensions form a nematic single phase, with large order parameter, S = 0.75 +/- 0.05. Very well aligned rutile films on glass substrate were produced by spin-coating and their photocatalytic properties were examined by monitoring the decomposition of methylene blue under UV-light. We found that UV-light polarized along the quadratic axis of the rutile nanorods was most efficient for this photocatalytic reaction. Some experiments of conduction have been performed. TiO2 rutile is a semi conductor with, for the bulk, a gap of around 3 eV. As in the photocatalytic studies, the polarized UV-light has a huge influence on the charge transport. A Schottky diode behaviour has been observed and explained. Irradiation in the visible spectrum has been shown to have no consequence on the properties of conduction. Rutile films have been also characterized to estimate the correction for the gap of anisotropic nanoparticles. Finally, a thermal study and a comparison with a monocrystal have been done.; Les phases cristal-liquides minérales se situent à l'interface de la chimie colloïdale, de la physique de la matière molle et de la physique du solide. Largement utilisées dans l'industrie, les nanoparticules de TiO2 de variété rutile sont des candidates de choix à une étude visant à relier propriétés du matériau massif et propriétés d'une assemblée orientée de petits objets anisotropes.Le travail présenté montrera comment il est possible d'élaborer par Chimie Douce des nanoparticules anisotropes afin d'obtenir en milieu aqueux une mésophase, de nature nématique, et de la caractériser. De plus, des suspensions de bâtonnets, même relativement diluées, s'orientent sous cisaillement, ce qui permet de produire par spin-coating des films anisotropes. Ces films sont des échantillons de choix pour effectuer des mesures, sous irradiation ultraviolette, de photocatalyse d'espèces organiques dissoutes ou encore de photoconduction. Ces mesures peuvent être comparées avec les résultats obtenus à l'aide d'un monocristal de TiO2 présentant les mêmes facettes cristallographique [110] que les nanoparticules.Un film orienté de bâtonnets de rutile présente naturellement des propriétés anisotropes. En outre, nous avons mis en évidence une forte dépendance des propriétés catalytiques et de la conductivité électronique avec la polarisation de l'irradiation ultra-violette. Nous montrerons dans quelle mesure la théorie des bandes permet d'expliquer ces effets.

International audience; The dilute lamellar phase of the nonionic surfactant C12EO5 was doped with goethite (iron oxide) nanorods up to a fraction of 5 vol %. The interaction between the inclusions and the host phase was studied by polarized optical microscopy (with or without an applied magnetic field) and by small-angle X-ray scattering. We find that, when the orientation of the nanorods is modified using the magnetic field, the texture of the lamellar phase changes accordingly; one can thus induce a homeotropic-planar reorientation transition. On the other hand, the lamellar phase induces an attractive interaction between the nanorods. In more concentrated lamellar phases (under stronger confinement) the particles form aggregates. This behavior is not encountered for a similar system doped with spherical particles, emphasizing the role of particle shape in the interaction between doping particles and the host phase.