Local Mass Transfer in Turbulent Flow by Electrochemical Methods

Mass transfer to the surface of rotating electrodes during turbulent flow was studied by electrochemical methods under steady and non-steady state diffusion conditions. The flow was due to a large rotating disk made from insulating material, flush with the surface of which was mounted a ring shaped electrode of platinum or nickel. A local study of the radial component of the convective diffusion in turbulent flow was carried out with very thin ring electrodes (width ΔR ~ 0,05 mm). The diffusion layer thickness was varied relatively to the diffusion sublayer thickness by changing the ring width or the rotation speed so as to determine the eddy diffusivity in the viscous sublayer. The local viscous friction was measured at the wall by a steady state method. As an application, the drag reduction phenomenon was studied in the presence of high polymer additives. Using a non-steady state method which yields the electrochemical impedance, we examined the possibility of adsorption of polymers at the wall- fluid interface

Changements de phase du gallium à la pression atmosphérique

After pointing out the importance of the choice of small volume samples in the study of nucleation in liquid gallium, the authors show that homogeneous nucleation conditions are obtained at — 123 °C for droplets resulting from the emulsion of the liquid metal. The solid phase which then appears is the inetastable form Gaβ ; the free interfacial enthalpy between the liquid and a Gaβ nucleus is measured. Thèse liquid samples crystal-lise only exceptionally in the stable form Gaα but it is possible to obtain a second solid metastable form Gaγ of which some physical characteristics are determined. From their thermodynamic parameters, the forms Gaβ and Gaγ are respectively identified with the forms Ga II and Ga III, stable at high pressure. The production of these metastable forms from liquid or vapour states is proved by the Ostwald degree rule.Après avoir signalé l'importance du choix des échantillons de faible volume dans l'étude de la germination dans le gallium liquide, on montre que les conditions de la germination homogène sont réalisées vers — 123 °C pour certaines gouttelettes provenant de J'émulsion du métal liquide ; la phase solide qui apparaît est alors la forme métastable Gaβ et l'on mesure l'enthalpie libre interfaciale entre le liquide et un germe de Gaβ. Ces échantillons liquides ne cristallisent qu'exceptionnellement en la forme stable Gaα, mais on peut aussi obtenir une deuxième phase solide métastable Gaγ dont on détermine quelques propriétés physiques. Par leurs paramètres thermodynamiques, les formes Gaβ et Gaγ sont identifiées respectivement aux formes Ga II et Ga III stables à haute pression. Des considérations sur la règle des degrés d'Ostwald permettent de justifier l'obtention de ces formes métastables à partir des états liquide ou vapeur

Investigating the burden of antibiotic resistance in ethnic minority groups in high-income countries: protocol for a systematic review and meta-analysis.

BACKGROUND: Antibiotic resistance (ABR) is an urgent problem globally, with overuse and misuse of antibiotics being one of the main drivers of antibiotic-resistant infections. There is increasing evidence that the burden of community-acquired infections such as urinary tract infections and bloodstream infections (both susceptible and resistant) may differ by ethnicity, although the reasons behind this relationship are not well defined. It has been demonstrated that socioeconomic status and ethnicity are often highly correlated with each other; however, it is not yet known whether accounting for deprivation completely explains any discrepancy seen in infection risk. There have currently been no systematic reviews summarising the evidence for the relationship between ethnicity and antibiotic resistance or prescribing. METHODS: This protocol will outline how we will conduct this systematic literature review and meta-analysis investigating whether there is an association between patient ethnicity and (1) risk of antibiotic-resistant infections or (2) levels of antibiotic prescribing in high-income countries. We will search PubMed/MEDLINE, EMBASE, Global Health, Scopus and CINAHL using MESH terms where applicable. Two reviewers will conduct title/abstract screening, data extraction and quality assessment independently. The Critical Appraisal Skills Programme (CASP) checklist will be used for cohort and case-control studies, and the Cochrane collaboration's risk of bias tool will be used for randomised control trials, if they are included. Meta-analyses will be performed by calculating the minority ethnic group to majority ethnic group odds ratios or risk ratios for each study and presenting an overall pooled odds ratio for the two outcomes. The Grading of Recommendations, Assessments, Development and Evaluation (GRADE) approach will be used to assess the overall quality of the body of evidence. DISCUSSION: In this systematic review and meta-analysis, we will aim to collate the available evidence of whether there is a difference in rates of AMR and/or antibiotic prescribing in minority vs. majority ethnic groups in high-income countries. Additionally, this review will highlight areas where more research needs to be conducted and may provide insight into what may cause differences in this relationship, should they be seen. SYSTEMATIC REVIEW REGISTRATION: PROSPERO ( CRD42016051533 )

Epidemiology of Coxiella burnetii infection in Africa: a OneHealth systematic review

Background: Q fever is a common cause of febrile illness and community-acquired pneumonia in resource-limited settings. Coxiella burnetii, the causative pathogen, is transmitted among varied host species, but the epidemiology of the organism in Africa is poorly understood. We conducted a systematic review of C. burnetii epidemiology in Africa from a “One Health” perspective to synthesize the published data and identify knowledge gaps.<p></p> Methods/Principal Findings: We searched nine databases to identify articles relevant to four key aspects of C. burnetii epidemiology in human and animal populations in Africa: infection prevalence; disease incidence; transmission risk factors; and infection control efforts. We identified 929 unique articles, 100 of which remained after full-text review. Of these, 41 articles describing 51 studies qualified for data extraction. Animal seroprevalence studies revealed infection by C. burnetii (≤13%) among cattle except for studies in Western and Middle Africa (18–55%). Small ruminant seroprevalence ranged from 11–33%. Human seroprevalence was <8% with the exception of studies among children and in Egypt (10–32%). Close contact with camels and rural residence were associated with increased seropositivity among humans. C. burnetii infection has been associated with livestock abortion. In human cohort studies, Q fever accounted for 2–9% of febrile illness hospitalizations and 1–3% of infective endocarditis cases. We found no studies of disease incidence estimates or disease control efforts.<p></p> Conclusions/Significance: C. burnetii infection is detected in humans and in a wide range of animal species across Africa, but seroprevalence varies widely by species and location. Risk factors underlying this variability are poorly understood as is the role of C. burnetii in livestock abortion. Q fever consistently accounts for a notable proportion of undifferentiated human febrile illness and infective endocarditis in cohort studies, but incidence estimates are lacking. C. burnetii presents a real yet underappreciated threat to human and animal health throughout Africa.<p></p&gt

Sur l'impédance de deux types d'électrodes à goutte de mercure

Les auteurs analysent les résultats de la superposition d'un courant sinusoïdal au courant d'électrolyse, en comparant deux types d'électrodes, l'une à goutte de mercure renouvelée (électrode Heyrovsky), l'autre à goutte suspendue (électrode Kemula).Ils indiquent une méthode d'enregistrement potentiocinétique des composantes de l'impédance de l'électrode suspendue. L'examen de l'impédance des deux électrodes en solution KCl 0,1 N montre que la capacité de la double couche électrochimique est la même dans les deux cas, mais qu'il apparaît un phénomène de relaxation diélectrique avec l'électrode Kemula. Celui-ci dépend de la nature des ions dans la solution