Prevalence of atopy, asthma and COPD in an urban and a rural area of an African country

SummaryThe objectives of this study were to determine the prevalence of asthma, atopy and COPD in Rwanda and to identify risk factors. The survey was conducted in Kigali, the Capital of Rwanda, and in Huye District, a rural area located in southern Rwanda.MethodsA total of 2138 subjects were invited to participate in the study.1920 individuals (90%) answered to questionnaires on respiratory symptoms and performed spirometry, 1824 had acceptable spirograms and performed skin-prick test. In case of airflow obstruction (defined as pre-bronchodilator ratio FEV1/FVC < LLN) a post bronchodilator spirometry was performed. Reversibility was defined as an increase in FEV1 of 200 ml and 12% above baseline FEV1 after inhalation of 400 mcg of salbutamol.ResultsThe mean age was 38.3 years; 48.1% of participants were males and 51.9% females. Airflow obstruction was found in 256 participants (14%); 163(8.9%) subjects were asthmatics and 82 (4.5%) had COPD. COPD was found in 9.6% of participants aged 45 years and above. 484 subjects had positive skin-prick tests (26.5%); house dust mite and grass pollen mix were the main allergens. Risk factors for asthma were allergy, female gender and living in Kigali. COPD was associated with cigarette smoking, age and male sex.Conclusionthis is the first study which shows the prevalence of atopy, asthma and COPD in Rwanda. Asthma and COPD were respectively diagnosed in 8.9% and 4.5% of participants. COPD was diagnosed in 9.6% of subjects aged ≥45 years.The prevalence of asthma was higher in urban compared to rural area

Multi-scale Periodic Homogenization of Ionic Transfer in Cementitious Materials

International audienc

Application of the periodic homogenization technique to ionic transfer in cementitious materials.

International audienc

Multi-scale periodic homogenization of ionic transfer in cementitious materials

International audienceA multi-scale periodic homogenization procedure of the ionic transfers in saturated porous media is proposed. An application on a multi-scale porous material was achieved for establishing models describing a ionic transfer from Nernst-Planck-Poisson-Boltzmann system. The first one is obtained by homogenization from the scale of Debye length to the capillary porosity scale, by taking into account the electrical double layer phenomenon. The second one results from another homogenization procedure from the capillary porosity scale to the scale of the material, where the electrical double layer effects are naturally negligible. A numerical parametric study is conducted on three dimensional elementary cells in order to highlight the effects of the electrical double layer on the ionic transfer parameters. Comparisons with existing experimental data are also presented and discussed. The double homogenization procedure gives homogenized diffusion coefficients very close to those obtained experimentally for chlorides ions from electrodiffusion tests carried out in laboratory

Determination of geometrical parameters of the microstructure of a porous medium Application to cementitious materials

International audienceMass transfer in porous media is governed, besides the species diffusion coefficient, by the porosity and the geometrical parameters of the materials microstructure. This paper aims at developing a methodology for the determination of tortuosity and constrictivity factor based on a diffusion modeling in a porous medium of neutral species. Tortuosity was obtained by the computation of particles trajectory. After which, constrictivity was deduced from the formation factor, represented by the relative diffusion coefficient. Results show that tortuosity evolves in the opposite direction that the porosity while constrictivity evolves in the same direction. In addition, both parameters further slowdown the transfer for lower porosities. © 2020 Elsevier Lt