The CONSTANCES cohort: an open epidemiological laboratory

<p>Abstract</p> <p>Background</p> <p>Prospective cohorts represent an essential design for epidemiological studies and allow for the study of the combined effects of lifestyle, environment, genetic predisposition, and other risk factors on a large variety of disease endpoints. The CONSTANCES cohort is intended to provide public health information and to serve as an "open epidemiologic laboratory" accessible to the epidemiologic research community. Although designed as a "general-purpose" cohort with very broad coverage, it will particularly focus on occupational and social determinants of health, and on aging.</p> <p>Methods/Design</p> <p>The CONSTANCES cohort is designed as a randomly selected representative sample of French adults aged 18-69 years at inception; 200,000 subjects will be included over a five-year period. At inclusion, the selected subjects will be invited to fill a questionnaire and to attend a Health Screening Center (HSC) for a comprehensive health examination: weight, height, blood pressure, electrocardiogram, vision, auditory, spirometry, and biological parameters; for those aged 45 years and older, a specific work-up of functional, physical, and cognitive capacities will be performed. A biobank will be set up. The follow-up includes a yearly self-administered questionnaire, and a periodic visit to an HSC. Social and work-related events and health data will be collected from the French national retirement, health and death databases. The data that will be collected include social and demographic characteristics, socioeconomic status, life events, behaviors, and occupational factors. The health data will cover a wide spectrum: self-reported health scales, reported prevalent and incident diseases, long-term chronic diseases and hospitalizations, sick-leaves, handicaps, limitations, disabilities and injuries, healthcare utilization and services provided, and causes of death.</p> <p>To take into account non-participation at inclusion and attrition throughout the longitudinal follow-up, a cohort of non-participants will be set up and followed through the same national databases as participants.</p> <p>A field-pilot was performed in 2010 in seven HSCs, which included about 3,500 subjects; it showed a satisfactory structure of the sample and a good validity of the collected data.</p> <p>Discussion</p> <p>The constitution of the full eligible sample is planned during the last trimester of 2010, and the cohort will be launched at the beginning of 2011.</p

Turbulent diffusion mass transfer in fluidised beds

The general principles of fluidisation are reviewed, followed by a description of the principles of electrochemical mass transfer measurement, local porosity measurement by electrical conductivity, and measurement of porosity fluctuations. An original experimental layout is briefly described in which these three quantities are measured locally in a fluid bed with an aqueous alkaline potassium ferro-and ferri-cyanide solution. The results of these measurements are given in the form of mass transfer vs. fluid flow velocity curves. Curves for vertical probe measurements show a maximum and some curves obtained with a horizontal probe also feature a minimum at high velocities. An explanation is given for this. Except near the ends of the bed, porosity and porosity fluctuations do not vary with probe position along the bed centreline. If the mass transfer data are plotted against porosity it is seen that maximum transfer is associated with a porosity value of 0.6, and if the difference between the coefficients measured in the bed and in the liquid alone at the same interstitial velocity are plotted against porosity, the data for various particle sizes can be combined into a single curve. The downward limb of curves obtained with the probe vertical can be put in the general form jDe = 1.21 (Ré) - 0.52 for 6 < Ré < 200 and agrees well with the Jagannadha Raju correlation. The mass transfer data for the liquid alone also agree satisfactorily with published data. Solid concentration fluctuations increase steadily with fluid velocity, and therefore also with porosity. With a similar theory to the van der Waals gas density fluctuation theory it can be shown that the bed particles do not behave as independent entities but that they agglomerate and form groups, and that the smaller the particles, the bigger the groups are

STUDY OF THE ELECTRICAL CONDUCTIVITY OF GRAPHITE FELT EMPLOYED AS A POROUS ELECTRODE

The objective of the present work is to study the variation of the electrode distribution potential under electrical conductivity variation of graphite felt RVG 4000 ( Le Carbone Lorraine) when submitted to a mechanical compression. Experimental and theoretical studies show that this electrical conductivity variation can changes the electrode potential distribution E(x) working under limiting current conditions. This may occur when graphite felt is confined in an electrochemical reactor compartment or simply when it is submitted to a force performed by an electrolyte percolation in a turbulent flow. This investigation can contribute to the improvement of electrochemical cells that may use this material as an electrode. Finally, one modification is suggested in the equation that gives the electrode potential distribution E(x) - E(0). In this case the parameter L (thickness in metal porous electrodes) is substituted for Lf = Li (1-j), where j corresponds to the reduction factor of the initial thickness Li