Surface pre-coating of talc particles by carboxyl methyl cellulose adsorption : study of adsorption and consequences on surface properties and settling rate

This paper investigates the adsorption of different sized carboxyl methyl cellulose (CMC) onto talc particles (adsorption isotherm, adsorption reversibility), its consequences on the particles properties (electrophoretic mobility and surface wetting) and its effect on their dispersion (settling coefficient). Throughout the paper, the properties of talc particles dispersed in CMC solution are compared to CMC pre-coated talc particles: talc particles dried in a solution of CMC before their redispersion. The adsorption of CMC onto talc was quantified at around 0.4 mg of CMC per m2 of talc and was seen to be irreversible on washing the talc particles with distilled water. When characterising talc surface properties, it was found that CMC adsorption leads to an increase of the negative surface charge and to an increase of the wettability. The settling velocity of CMC pre-coated talc particles in water can be around 50 % lower than that of the initial talc particles. The pre-coating of talc particles by CMC is then assumed to increase their stabilization : particle aggregation is hindered by adsorbed CMC layer inducing electrosteric repulsion between the talc particles. The technique of talc pre-coating with CMC makes the talc dispersion easier and could open interesting perspectives in engineering processes using talc dispersions

High conductivity in Si-doped GaN wires

4 pagesInternational audienceTemperature-dependent resistivity measurements have been performed on single Si-doped GaN microwires grown by catalyst-free metal-organic vapour phase epitaxy. Metal-like conduction is observed from four-probe measurements without any temperature dependence between 10 K and 300 K. Radius-dependent resistivity measurements yield resistivity values as low as 0.37 mohm.cm. This is in agreement with the full width at half maximum (170 meV) of the near band edge luminescence obtained from low temperature cathodoluminescence study. Higher dopant incorporation during wire growth as compared to conventional epitaxial planar case is suggested to beresponsiblefortheuniqueconductivity

Thermoelectric and micro-Raman measurements of carrier density and mobility in heavily Si-doped GaN wires

International audienceCombined thermoelectric-resistivity measurements and micro-Raman experiments have been performed on single heavily Si-doped GaN wires. In both approaches, similar carrier concentration and mobility were determined taking into account the non-parabolicity of the conduction band. The unique high conductivity of Si-doped GaN wires is explained by a mobility µ=56 cm2 /V s at a carrier concentration n = 2.6 10^20 /cm 3. This is attributed to a more efficient dopant incorporation in Si-doped GaN microwires as compared to Si-doped GaN planar layers. (c) 2013 AIP Publishing LLC

Geometrical structure of an iron epilayer on Si (111) : an X-ray standing wave analysis

dépôt d'une copie effectué avec l'aimable autorisation de EDP SciencesThe structure of an iron film, deposited at low temperature (50 °C) upon a silicon (111) substrate, has been determined by means of X-ray Standing Wave experiments performed at LURE (Orsay, France). Experimental results are coherent with the model of an abrupt interface between the adsorbate and the surface : the first site of adsorption terminates the bulk silicon and a body-centred iron layer epitaxially grows on the substrate with a preferential growth orientation

Effect of Cold Pressor Test on the Internal Diameter of the Radial Artery

The aim of this study was to investigate in normal subjects the effect of a cold pressor test on the caliber of the radial artery, a muscular artery of medium size. The internal diameter of this artery was measured continuously using a recently developed ultrasonic device. Immersion of one hand in ice water for two minutes increased blood pressure from 115/75 ± 3/2 (Mean±SEM) to 136/90 ± 6/2 mm Hg (P <.001) and decreased the internal diameter of the radial artery from 2.82 ± 0.12 to 2.60 ± 0.09 mm ( P <.01). These data therefore indicate that the vasoconstriction induced by the cold pressor test involves not only arterioles, but also medium-size arteries. Am J Hypertens 1989; 2:727-72

Genetic and Epigenetic Factors at <i>COL2A1</i> and <i>ABCA4</i> Influence Clinical Outcome in Congenital Toxoplasmosis

Background: Primary Toxoplasma gondii infection during pregnancy can be transmitted to the fetus. At birth, infected infants may have intracranial calcification, hydrocephalus, and retinochoroiditis, and new ocular lesions can occur at any age after birth. Not all children who acquire infection in utero develop these clinical signs of disease. Whilst severity of disease is influenced by trimester in which infection is acquired by the mother, other factors including genetic predisposition may contribute. Methods and Findings: In 457 mother-child pairs from Europe, and 149 child/parent trios from North America, we show that ocular and brain disease in congenital toxoplasmosis associate with polymorphisms in ABCA4 encoding ATP-binding cassette transporter, subfamily A, member 4. Polymorphisms at COL2A1 encoding type II collagen associate only with ocular disease. Both loci showed unusual inheritance patterns for the disease allele when comparing outcomes in heterozygous affected children with outcomes in affected children of heterozygous mothers. Modeling suggested either an effect of mother's genotype, or parent-of-origin effects. Experimental studies showed that both ABCA4 and COL2A1 show isoform-specific epigenetic modifications consistent with imprinting. Conclusions: These associations between clinical outcomes of congenital toxoplasmosis and polymorphisms at ABCA4 and COL2A1 provide novel insight into the molecular pathways that can be affected by congenital infection with this parasite.</p

Genetic and Epigenetic Factors at COL2A1 and ABCA4 Influence Clinical Outcome in Congenital Toxoplasmosis

Background: Primary Toxoplasma gondii infection during pregnancy can be transmitted to the fetus. At birth, infected infants may have intracranial calcification, hydrocephalus, and retinochoroiditis, and new ocular lesions can occur at any age after birth. Not all children who acquire infection in utero develop these clinical signs of disease. Whilst severity of disease is influenced by trimester in which infection is acquired by the mother, other factors including genetic predisposition may contribute.Methods and Findings: In 457 mother-child pairs from Europe, and 149 child/parent trios from North America, we show that ocular and brain disease in congenital toxoplasmosis associate with polymorphisms in ABCA4 encoding ATP-binding cassette transporter, subfamily A, member 4. Polymorphisms at COL2A1 encoding type II collagen associate only with ocular disease. Both loci showed unusual inheritance patterns for the disease allele when comparing outcomes in heterozygous affected children with outcomes in affected children of heterozygous mothers. Modeling suggested either an effect of mother's genotype, or parent-of-origin effects. Experimental studies showed that both ABCA4 and COL2A1 show isoform-specific epigenetic modifications consistent with imprinting.Conclusions: These associations between clinical outcomes of congenital toxoplasmosis and polymorphisms at ABCA4 and COL2A1 provide novel insight into the molecular pathways that can be affected by congenital infection with this parasite

Peasant settlers and the ‘civilizing mission’ in Russian Turkestan, 1865-1917

This article provides an introduction to one of the lesser-known examples of European settler colonialism, the settlement of European (mainly Russian and Ukrainian) peasants in Southern Central Asia (Turkestan) in the late nineteenth and early twentieth centuries. It establishes the legal background and demographic impact of peasant settlement, and the role played by the state in organising and encouraging it. It explores official attitudes towards the settlers (which were often very negative), and their relations with the local Kazakh and Kyrgyz population. The article adopts a comparative framework, looking at Turkestan alongside Algeria and Southern Africa, and seeking to establish whether paradigms developed in the study of other settler societies (such as the ‘poor white’) are of any relevance in understanding Slavic peasant settlement in Turkestan. It concludes that there are many close parallels with European settlement in other regions with large indigenous populations, but that racial ideology played a much less important role in the Russian case compared to religious divisions and fears of cultural backsliding. This did not prevent relations between settlers and the ‘native’ population deteriorating markedly in the years before the First World War, resulting in large-scale rebellion in 1916

Isokinetic and high performance sport: application sport traumatology

Le sport de haut niveau par la pratique régulière de l’activité, la répétition de gestes stéréotypés à haute intensité et la spécificité de l’entraînement, expose les sportifs au risque de traumatismes. Risque qui a considérablement augmenté avec les exigences du haut niveau, la fréquence de plus en plus grande des compétitions, la pression du résultat et l’émergence du sport business. Face à ce risque, l’isocinétisme s’inscrit comme une technique de référence dans l’évaluation des performances musculaires. Le dynamomètre isocinétique permet une mesure précise et reproductible de la force musculaire dynamique, à condition de respecter une méthodologie rigoureuse. L’utilisation de l’isocinétisme dans le sport de haut niveau s’est nettement développée afin d’identifier les profils musculaires à risque, et corriger les déséquilibres musculaires, en prévention de blessures. En thérapeutique, nous utilisons l’isocinétisme pour la rééducation des pathologies musculaires, tendineuses et ligamentaires (rupture du LCAE). Aujourd’hui, le travail musculaire excentrique doit s’imposer dans les pathologies citées ci-dessus. Les modalités d’application du protocole conditionnent son efficacité. Nous prônons, depuis des années, une prise en charge précoce de la blessure par un travail isocinétique excentrique à vitesse lente, dans un but cicatriciel du tissu lésé. L’outil isocinétique permet de réaliser ce travail excentrique précocement de manière sécurisé. Il est complémentaire aux autres techniques kinésithérapiques. Il nous semble indispensable dans la prise en charge des sportifs de haut niveau pour le suivi de la rééducation et la complète récupération fonctionnelle. Il quantifie l’un des critères de reprise du sport permettant de réduire le risque de récidive tant redouté. Après chirurgie du ligament croisé antérieur, objectiver précisément le niveau de récupération musculaire permet de mieux individualiser la rééducation et la phase de réathlétisation

Bedload transport and bedforms migration under sand supply limitation

International audienceMost studies on sediment transport and bedforms migration consider unlimited sediment supply conditions. However, areas where the sediment supply is limited are common in coastal and fluvial environments. The present paper, based on physical modelling in a flume and on a re-analysis of field data obtained in the Eastern English Channel by Ferret [23], considers the effects of sediment supply limitation on bedload transport and bedforms migration velocity. The bedload transport is found to be proportional to the fraction of the bed covered by sediments for a bed exhibiting bedforms. The migration velocity of bedforms depends on the dominant mode of sediment transport. A new formulation showing a good agreement with experimental tests and observations in the field is proposed for the dimensionless migration velocity of these bedforms when sediment transport is dominated by bedload, under unlimited sediment supply conditions.For limited sediment supply conditions and sediment transport dominated by bedload, an adaptation of the formulation is suggested from flume data sets, based on the fraction of the bed covered by sediment