R. Charvet - Academia.edu (original) (raw)

Papers by R. Charvet

Techniques Sciences Méthodes, 2011

Journal européen d’hydrologie, 1999

Techniques Sciences Méthodes, 2013

Revue de Chirurgie Orthopédique et Traumatologique, 2011

EMC - Aparato Locomotor, 2010

ABSTRACT La rigidez del hombro, caracterizada desde el punto de vista clínico por la disminución ... more ABSTRACT La rigidez del hombro, caracterizada desde el punto de vista clínico por la disminución de los movimientos pasivos, sobre todo en rotación lateral E1 y en flexión, aún conserva una parte de su misterio fisiopatológico. En la mayoría de los casos, forma parte del síndrome de dolor regional complejo (SDRC) de tipo I, denominación que sustituye a las de capsulitis adhesiva o retracción capsular o síndrome algodistrófico. Los pocos estudios anatomopatológicos e inmunológicos realizados ponen de manifiesto una proliferación de células fibroblásticas, en algunos casos con asociación de signos inflamatorios de la sinovial. El tratamiento es ante todo conservador: rehabilitación, control del dolor y distensiones artrográficas que permiten, en la mayoría de los casos y al precio de una evolución de varios meses, la recuperación funcional. Las liberaciones artroscópicas, menos perjudiciales que las artrólisis a cielo abierto, pueden indicarse cuando fracasan los tratamientos conservadores. Las medidas preventivas de la rigidez tras cirugía del hombro son producto de un consenso profesional: rehabilitación precoz y control del dolor postoperatorio. En la cirugía del hombro, cualquiera que sea la técnica empleada, debe informarse al paciente acerca de la posibilidad de que se produzca un SDRC de tipo I.

EMC - Appareil locomoteur, 2009

Multiaxial experiments are performed on replicated aluminium foam using a custom-built apparatus.... more Multiaxial experiments are performed on replicated aluminium foam using a custom-built apparatus. The foam structure is isotropic, and features open monomodal pores 75μm in average diameter. Plane stress (σ1, σ2, σ3= 0) and axisymmetric (σ1, σ2= σ3) yield ...

It has been proposed in the literature, based on theoretical considerations and on finite-element... more It has been proposed in the literature, based on theoretical considerations and on finite-element calculations, that all three stress tensor invariants govern the yield surface of cellular materials. Recent experiments on 75μm pore size aluminium replicated foams ( ...

Journal of the Mechanics and Physics of Solids, 2011

Journal of Materials Science, 2012

ABSTRACT In the pressure infiltration of metal matrix composites, molten metal is injected under ... more ABSTRACT In the pressure infiltration of metal matrix composites, molten metal is injected under external pressure into a porous preform of the reinforcing material. Equilibrium capillary parameters characterizing wetting for this process are summarized in plots of metal saturation versus applied pressure, also known as drainage curves. Such curves can be measured in our laboratory during a single experiment with an infiltration apparatus designed to track the rate of metal penetration into porous preforms under conditions characteristic of metal matrix composite processing (temperatures in excess of 1000 °C and pressures in the order of 10 MPa). For such measurements to be valid, infiltration of the preform with molten metal must be mechanically quasi-static, i.e., the metal must flow at a rate sufficiently low for the metal pressure to be essentially uniform across the preform at all times. We examine this requirement quantitatively, using a finite-difference model that simulates the unsaturated unidirectional ingress of molten metal into a ceramic particle preform of finite width. We furthermore present improvements in the experimental apparatus developed in our laboratory to measure the entire drainage curve in a single experiment. We compare numerical results with new experimental data for the copper/alumina system to show (i) that pressurization rates sufficiently low for quasi-static infiltration can be produced with this apparatus, and (ii) that taking the relative permeability equal to the saturation yields better agreement with experiment than does the expression originally proposed by Brooks and Corey.

Acta Materialia, 2010

Environmental Chemistry, 2005

ABSTRACT Following evidence for the intoxication of bees, the systemic insecticide imidacloprid w... more ABSTRACT Following evidence for the intoxication of bees, the systemic insecticide imidacloprid was suspected from the mid nineties of having harmful effects. Recently, some studies have demonstrated that imidacloprid is toxic for the bees at sub-lethal doses. These doses are evaluated in the range between 1 and 20 µg kg−1, or less. It appeared thus necessary to study the fate of imidacloprid in the environment at such low levels. Thus, we developed methods for the determination of low amounts, in the µg kg−1 range, of the insecticide imidacloprid in soils, plants and pollens using high pressure liquid chromatography — tandem mass spectrometry (LC/APCI/MS/MS). The extraction and separation methods were performed according to quality assurance criteria, good laboratory practices and the European Community’s criteria applicable to banned substances (directive 96/23 EC). The linear concentration range of application was 1–50 µg kg−1 of imidacloprid, with a relative standard deviation of 2.9% at 1 µg kg−1. The limit of detection and quantification are respectively LOD = 0.1 µg kg−1 and LOQ = 1 µg kg−1 and are suited to the sub-lethal dose range. This technique allows the unambiguous identification and quantification of imidacloprid. The results show the remanence of the insecticide in soils, its ascent into plants during flowering and its bioavailability in pollens.

Analytical Chemistry, 2003

Imidacloprid, the most used systemic insecticide, is suspected of having harmful effects on honey... more Imidacloprid, the most used systemic insecticide, is suspected of having harmful effects on honeybees at nanogram per bee or at microgram per kilogram levels. However, there is a lack of methodology to detect imidacloprid and its metabolites at such low levels. We developed a method for the determination of low amounts of imidacloprid in soils, plants (leaves and flowers), and pollens by using HPLC coupled to tandem mass spectrometry (APCI-MS/MS). Extraction, separation, and detection were performed according to quality assurance criteria, to Good Laboratory Practice, and to criteria from the directive 96/23/EC, which is designed for banned substances. The linear range of application is 0.5-20 µg/ kg imidacloprid in soils, in plants, and in pollens, with a relative standard deviation of 2.9% at 1 µg/kg. The limits of detection and of quantification are LOD ) 0.1 µg/kg and LOQ ) 1 µg/kg, respectively. For the first time, this study permitted us to follow the fate of imidacloprid in the environment. When treated, flowers of sunflower and maize contain average values of ∼10 µg/kg imidacloprid. This explains that pollens from these crops are contaminated at levels of a few micrograms per kilogram, suggesting probable deleterious effects on honeybees.