Influence de la phosphatation au zinc sur la résistance a la corrosion d’un acier au carbone en milieu maring

Zinc phosphatation influence on the resistance to corrosion of a carbonbased steel in marine mediumIn the frame of the present investigation, we have showed that the profile of the cathodic curves of a non phosphated metal, plead in favour to a kinetic profile essentially monitored by a pure diffusion. The corrosion rate, obtained from the cathodic curves as well as by a colorimetrical dosage of the dissolved iron, increases when the rotation speed of the electrode increases. Which show a diffusional control the phosphatation of the electrode does not seem to modify the cathodic curves profile. However the height of the diffusion palier depends on the thickness of the phosphatation layer. It takes values lower than those of an uncovered steel for a layer thickness of two micrometers the phosphatation layer reinforce notably the resistance to the corrosion of the internal layer which is essentially composed with iron oxides, by decreasing the corrosion rate with the increase of the layer. However, the benefical effect of the phosphatation is maximal for a thickness of three micrometers. This effect occurs also during the anodic behaviour

Proton conductivity in Al-stevensite pillared clays

Fine stevensite mineral fraction (< 2 m) has been extracted from natural Moroccan ghassoulite clay. Thereafter, it has been pillared by Al13 polycations species. Physico-chemical characterization, performed using X-ray diffraction (XRD), thermal analysis (TG-TDA) and Scanning Electron Microscopy (SEM) equipped with X-ray Energy Dispersion (XED) analysis, has proved that stevensite pillaring has been successfully achieved. Electrical impedance measurements, carried out onto samples before and after pillaring operation, have shown an increase in proton conductivity for pillared with respect to pristine stevensite clay mineral.Fine stevensite mineral fraction (< 2 m) has been extracted from natural Moroccan ghassoulite clay. Thereafter, it has been pillared by Al13 polycations species. Physico-chemical characterization, performed using X-ray diffraction (XRD), thermal analysis (TG-TDA) and Scanning Electron Microscopy (SEM) equipped with X-ray Energy Dispersion (XED) analysis, has proved that stevensite pillaring has been successfully achieved. Electrical impedance measurements, carried out onto samples before and after pillaring operation, have shown an increase in proton conductivity for pillared with respect to pristine stevensite clay mineral

Regional dissemination of Salmonella enterica serovar Enteritidis is season dependent

ObjectiveTo carry out epidemiological typing of clinical isolates of Salmonella enterica serovar Enteritidis by pulsed-field gel electrophoresis (PFGE), random amplified polymorphic DNA (RAPD) and analysis of their antibiotic resistance.MethodsOver a 12-month period, 44 Salmonella Enteritidis isolates, recovered from 40 patients admitted to the University Hospital Center of Amiens, France and from three outpatients, were characterized by the analysis of phenotypic and genotypic traits and clinical data from medical reports.ResultsForty nontyphoidal salmonellosis episodes were diagnosed in hospitalized patients (34 episodes of gastroenteritis, two episodes of bacteremia not affecting other organs, one episodes of bacteremia plus urinary infection, one episodes of bacteremia plus gastroenteritis, one episodes of chronic colitis plus gastroenteritis and one episode of peritonitis), and three carriers were observed in outpatients. By means of PFGE, RAPD and antibiotic susceptibility patterns 44 isolates were subdivided into 16 clonally related groups. Two of them were predominantly implicated in the course of these infections, being responsible for two successive waves of infection, while the others were encountered sporadically

Elucidating the crystal-chemistry of Jbel Rhassoul stevensite (Morocco) by advanced analytical techniques

The composition of Rhassoul clay is controversial regarding the nature of the puremineral clay fraction which is claimed to be stevensite rather than saponite. In this study, the raw and mineral fractions were characterized using various techniques including Fourier transform infrared spectroscopy and magic angle spinning nuclear magnetic resonance (MAS NMR). The isolated fine clay mineral fraction contained a larger amount of Al (>1 wt.%) than that reported for other stevensite occurrences. The 27Al MAS NMR technique confirmed that the mineral is stevensite in which the Al is equally split between the tetrahedral and octahedral coordination sites. The 29Si NMR spectrum showed a single unresolved resonance indicating little or no short-range ordering of silicon. The chemical composition of the stevensite from Jbel Rhassoul was determined to be ((Na0.25K0.20 (Mg5.04Al0.37Fe0.20&0.21)5.61(Si7.76Al0.24)8O20(OH)4). This formula differs from previous compositions described from this locality and shows it to be an Al-bearing lacustrine clay mineral

Comparative study of inhibitory efficacy of methionine and its derivatives in acidic medium by mild steel

Corrosion inhibition effect of L-Methionine (MT1), L-Methionine sulfoxide (MT2) and L-Methionine sulfone (MT3) on mild steel corrosion in 1M HCl solution was studied by using weight loss, electrochemical polarization and electrochemical impedance spectroscopy (EIS) techniques. The experimental results showed that the inhibitory efficiency of the three aminoacids improves with the increase of concentration to reach the maximum value of 95.20% for MT1, 94.14% for MT2 and 88.92% for MT3 for a concentration of 10-3M, which translates that the surface covered by the inhibitor increases with the concentration. The effect of temperature on the corrosion rate was investigated and some thermodynamic parameters were calculated. Polarization studies show that three studied inhibitors suggested that three inhibitors control the anodic as well as cathodic reactions and act as mixed type in nature. The results show that MT1, MT2 and MT3 are good inhibitors, and the adsorption of each inhibitor on mild steel surface obeys Flory-Huggins and Langmuir, with a better fit of the Langmuir isotherm through mixed adsorption (physisorption as well as chemisorption) process. In addition, the quantum approach based on density functional theory (DFT), monte Carlo (MC) and molecular dynamics (MD) simulations was confirmed the reactivity of the studied compound towards the corrosion process

Explorations électrophysiologiques visuelles : principes et indications.

Les explorations électrophysiologiques visuelles sont des examens fonctionnels qui explorent le fonctionnement de la rétine et des voies visuelles. Leurs indications sont très variées et doivent être connues par les médecins généralistes. Le but de ce travail est d’expliquer de façon claire et concise les principes de ces examens et de souligner leurs principales indications

Pronostic visuel et évolution réfractive après chirurgie de la cataracte congénitale avec implantation primaire: Étude d’une série de 108 cas

La cataracte congénitale constitue la cause la plus fréquente de cécité évitable chez les enfants. Le but de cette étude est d'évaluer le pronosticréfractif et fonctionnel, des enfants opérés de cataracte congénitale avec implantation. Il s'agit d'une étude rétrospective de 108 enfants, dont 85cataractes bilatérales, 23 unilatérales opérés entre 2007 et 2011. La réfraction a été mesurée à 1 mois, 3 mois, 6 mois, 1 an, 2 ans, 3 ans et/ou 4 ans en post-opératoire. La meilleure acuité visuelle corrigée, ainsi que l'incidence des complications post-opératoires ont été analysé. L'âge moyen de la chirurgie était de 25 mois avec une durée moyenne de suivi de 3,17 ans. Les complications retrouvées étaient l'inflammation, la prolifération secondaire, et le glaucome. L'acuité visuelle (AV) moyenne corrigée finale était de 5,75/10e pour les formes bilatérales, et de  4,16/10e pour les unilatérales (p = 0,001). Les facteurs de mauvais pronostic retrouvés étaient l'âge tardif de la chirurgie, la densité de la cataracte et la survenue de complications (p = 0,001). L'incidence des complications post-opératoires était significativement plus élevé chez les enfants opérés à un jeune âge (p = 0,001). Les facteurs de mauvais pronostic visuel chez les enfants opérés pour cataracte congénitale avec implantation, sont représentés par le caractère unilatéral de la cataracte, l'âge tardif de la chirurgie, la densité de la cataracte et la survenue de complications post opératoires