Two-dimensional flow of foam around an obstacle: force measurements

A Stokes experiment for foams is proposed. It consists in a two-dimensional flow of a foam, confined between a water subphase and a top plate, around a fixed circular obstacle. We present systematic measurements of the drag exerted by the flowing foam on the obstacle, \emph{versus} various separately controlled parameters: flow rate, bubble volume, bulk viscosity, obstacle size, shape and boundary conditions. We separate the drag into two contributions, an elastic one (yield drag) at vanishing flow rate, and a fluid one (viscous coefficient) increasing with flow rate. We quantify the influence of each control parameter on the drag. The results exhibit in particular a power-law dependence of the drag as a function of the bulk viscosity and the flow rate with two different exponents. Moreover, we show that the drag decreases with bubble size, and increases proportionally to the obstacle size. We quantify the effect of shape through a dimensioned drag coefficient, and we show that the effect of boundary conditions is small.Comment: 26 pages, 13 figures, resubmitted version to Phys. Rev.

Aeration of a Free Jet Above a Spillway

A study of air entrainment above an spillway aerator is presented and discussed with a dimensional analysis. We conclude that similitude of air entrainment processes for spillway aerator is not possible between model and prototype. New informations on the aeration region are presented and an analytical solution of the upper nappe entrainment is developed

Risk factors for tuberculosis treatment failure, default, or relapse and outcomes of retreatment in Morocco

<p>Abstract</p> <p>Background</p> <p>Patients with tuberculosis require retreatment if they fail or default from initial treatment or if they relapse following initial treatment success. Outcomes among patients receiving a standard World Health Organization Category II retreatment regimen are suboptimal, resulting in increased risk of morbidity, drug resistance, and transmission.. In this study, we evaluated the risk factors for initial treatment failure, default, or early relapse leading to the need for tuberculosis retreatment in Morocco. We also assessed retreatment outcomes and drug susceptibility testing use for retreatment patients in urban centers in Morocco, where tuberculosis incidence is stubbornly high.</p> <p>Methods</p> <p>Patients with smear- or culture-positive pulmonary tuberculosis presenting for retreatment were identified using clinic registries in nine urban public clinics in Morocco. Demographic and outcomes data were collected from clinical charts and reference laboratories. To identify factors that had put these individuals at risk for failure, default, or early relapse in the first place, initial treatment records were also abstracted (if retreatment began within two years of initial treatment), and patient characteristics were compared with controls who successfully completed initial treatment without early relapse.</p> <p>Results</p> <p>291 patients presenting for retreatment were included; 93% received a standard Category II regimen. Retreatment was successful in 74% of relapse patients, 48% of failure patients, and 41% of default patients. 25% of retreatment patients defaulted, higher than previous estimates. Retreatment failure was most common among patients who had failed initial treatment (24%), and default from retreatment was most frequent among patients with initial treatment default (57%). Drug susceptibility testing was performed in only 10% of retreatment patients. Independent risk factors for failure, default, or early relapse after initial treatment included male gender (aOR = 2.29, 95% CI 1.10-4.77), positive sputum smear after 3 months of treatment (OR 7.14, 95% CI 4.04-13.2), and hospitalization (OR 2.09, 95% CI 1.01-4.34). Higher weight at treatment initiation was protective. Male sex, substance use, missed doses, and hospitalization appeared to be risk factors for default, but subgroup analyses were limited by small numbers.</p> <p>Conclusions</p> <p>Outcomes of retreatment with a Category II regimen are suboptimal and vary by subgroup. Default among patients receiving tuberculosis retreatment is unacceptably high in urban areas in Morocco, and patients who fail initial tuberculosis treatment are at especially high risk of retreatment failure. Strategies to address risk factors for initial treatment default and to identify patients at risk for failure (including expanded use of drug susceptibility testing) are important given suboptimal retreatment outcomes in these groups.</p

Management of pulmonary tuberculosis patients in an urban setting in Zambia: a patient's perspective

<p>Abstract</p> <p>Background</p> <p>Zambia continues to grapple with a high tuberculosis (TB) burden despite a long running Directly Observed Treatment Short course programme. Understanding issues that affect patient adherence to treatment programme is an important component in implementation of a successful TB control programme. We set out to investigate pulmonary TB patient's attitudes to seek health care, assess the care received from government health care centres based on TB patients' reports, and to seek associations with patient adherence to TB treatment programme.</p> <p>Methods</p> <p>This was a cross-sectional study of 105 respondents who had been registered as pulmonary TB patients (new and retreatment cases) in Ndola District between January 2006 and July 2007. We administered a structured questionnaire, bearing questions to obtain individual data on socio-demographics, health seeking behaviour, knowledge on TB, reported adherence to TB treatment, and health centre care received during treatment to consenting respondents.</p> <p>Results</p> <p>We identified that respondents delayed to seek treatment (68%) even when knowledge of TB symptoms was high (78%) or when they suspected that they had TB (73%). Respondent adherence to taking medication was high (77%) but low adherence to submitting follow-up sputum (47%) was observed in this group. Similarly, caregivers educate their patients more often on the treatment of the disease (98%) and drug taking (100%), than on submitting sputum during treatment (53%) and its importance (54%). Respondent adherence to treatment was significantly associated with respondent's knowledge about the disease and its treatment (p < 0.0001), and with caregiver's adherence to treatment guidelines (p = 0.0027).</p> <p>Conclusions</p> <p>There is a need to emphasise the importance of submitting follow-up sputum during patient education and counselling in order to enhance patient adherence and ultimately treatment outcome.</p

Factors Associated with Tuberculosis Treatment Default in an Endemic Area of the Brazilian Amazon: A Case Control-Study

SETTING: Treatment default is a serious problem in tuberculosis control because it implies persistence of infection source, increased mortality, increased relapse rates and facilitates the development of resistant strains. OBJECTIVE: This study analyzed tuberculosis treatment default determinants in the Amazonas State to contribute in planning appropriate control interventions. DESIGN: Observational study with a retrospective cohort using Brazilian Disease Notification System data from 2005 to 2010. A nested case control study design was used. Patients defaulting from treatment were considered as 'cases' and those completing treatment as 'controls'. In the analysis, 11,312 tuberculosis patients were included, 1,584 cases and 9,728 controls. RESULTS: Treatment default was observed to be associated to previous default (aOR 3.20; p<0.001), HIV positivity (aOR 1.62; p<0.001), alcoholism (aOR 1.51; p<0.001), low education level (aOR 1.35; p<0.001) and other co-morbidities (aOR 1.31; p = 0.05). Older patients (aOR 0.98; p = 0.001) and DOT (aOR 0,72; p<0.01) were considered as protective factor for default. CONCLUSIONS: Associated factors should be considered in addressing care and policy actions to tuberculosis control. Information on disease and treatment should be intensified and appropriate to the level of education of the population, in order to promote adherence to treatment and counter the spread of multidrug resistance to anti-TB drugs

Etude de l'écoulement et de la répartition des pressions au voisinage du piston d'un amortisseur hydraulique

A criterion characterizing the flow in an oil damper is established. A phenomenological analysis is applied, based on the Navier-Stokes equations and show that, there are two regimes of flow in fonction of the pressure gradient values, in spite of the low Reynolds numbers involve. The losses of pressure occur either under viscous form, or under inertial form. A model based on the analogy between a radial divergent flow and a flow taking place under the piston, allows to evaluate quantitatively the pressure distribution and the expression of the resulting force at the piston level. The predictions of the phenomenological analysis are confirmed by experiments simulating the flow in the vicinity of the piston.Nous établissons un critère permettant de caractériser l'écoulement dans un amortisseur hydraulique. Pour cela, nous appliquons l'analyse phénoménologique aux équations de Navier-Stokes et parvenons à montrer que, selon la valeur du gradient de pression, il existe deux régimes d'écoulement, malgré les faibles nombres de Reynolds. On en déduit que les pertes de charge se produisent tantôt sous forme visqueuse, tantôt sous forme inertielle. Un modèle basé sur l'analogie entre un écoulement radial divergent et l'écoulement se produisant sous le piston, nous permet d'évaluer la répartition des pressions puis l'expression de la force résultante qui s'exerce à ce niveau. Les prévisions de l'analyse phénoménologique concordent avec les résultats établis par les essais expérimentaux simulant l'écoulement

Etude de l'écoulement et de la répartition des pressions au voisinage du piston d'un amortisseur hydraulique

Nous établissons un critère permettant de caractériser l'écoulement dans un amortisseur hydraulique. Pour cela, nous appliquons l'analyse phénoménologique aux équations de Navier-Stokes et parvenons à montrer que, selon la valeur du gradient de pression, il existe deux régimes d'écoulement, malgré les faibles nombres de Reynolds. On en déduit que les pertes de charge se produisent tantôt sous forme visqueuse, tantôt sous forme inertielle. Un modèle basé sur l'analogie entre un écoulement radial divergent et l'écoulement se produisant sous le piston, nous permet d'évaluer la répartition des pressions puis l'expression de la force résultante qui s'exerce à ce niveau. Les prévisions de l'analyse phénoménologique concordent avec les résultats établis par les essais expérimentaux simulant l'écoulement

Sur une méthode électrochimique pour l'étude des films d'eau en écoulement sur un plan

Pour étudier la dynamique d'un film liquide entraîné par l'air sur un plan, deux paramètres sont indispensables pour aboutir à une description correcte des phénomènes : l'épaisseur du film et le gradient de vitesse à la paroi solide. Nous avons proposé d'associer une mesure de conductivité en très hautes fréquences fournissant l'épaisseur du film, à une mesure, par une technique polarographique, du courant limite de diffusion, pour évaluer le module du gradient de vitesse pariétal et son signe. Nous avons mis au point une nouvelle méthode permettant la mesure simultanée, locale et instantanée, de ces deux grandeurs, de façon à suivre leur évolution temporelle et spatiale en fonction de l'écoulement de l'air