Bubble-based acoustic micropropulsors: active surfaces and mixers.

Acoustic micropropulsors present great potential for microfluidic applications. The propulsion is based on encapsulated 20 µm bubbles excited by a contacless ultrasonic transducer. The vibrating bubbles then generate a powerful streaming flow, with speeds 1-100 mm s-1 in water, through the action of viscous stresses. In this paper we introduce a full toolbox of micropropulsors using a versatile three-dimensional (3D) microfabrication setup. Doublets and triplets of propulsors are introduced, and the flows they generate are predicted by a theoretical hydrodynamic model. We then introduce whole surfaces covered with propulsors, which we term active surfaces. These surfaces are excited by a single ultrasonic wave, can generate collective flows and may be harnessed for mixing purposes. Several patterns of propulsors are tested, and the flows produced by the two most efficient mixers are predicted by a simple theoretical model based on flow singularities. In particular, the vortices generated by the most efficient pattern, an L-shaped mixer, are analysed in detail.

Prevalence and risk factors of sleep disturbances in a large HIV-infected adult population.

INTRODUCTION: Sleep disturbances are frequently reported in HIV-infected patients but there is a lack of large studies on prevalence and risk factors, particularly in the context of current improved immuno-clinical status and use of the newest antiretrovirals (ARV). METHOD: Cross-sectional study to evaluate the prevalence and factors associated with sleep disturbance in adult HIV-infected patients in six French centres of the region "Pays de la Loire". Patients filled a self-administered questionnaire on their health behaviour, sleep attitudes (Pittsburgh Sleep Quality Index PSQI), quality of life (WHO QOL HIV BREF questionnaire) and depression (Beck depression Inventory (BDI)-II questionnaire). Socio-demographic and immunovirologic data, medical history, ARVs were collected. RESULTS: From November 2012 to May 2013, 1354 consecutive non-selected patients were enrolled. Patients' characteristics were: 73.5% male, median age 47 years, active employment 56.7%, France-native 83% and Africa-native 14.7%, CDC stage C 21%, hepatitis co-infection 13%, lipodystrophy 11.8%, dyslipidemia 20%, high BP 15.1%, diabetes 3%, tobacco smokers 39%, marijuana and cocaine users, 11.7% and 1.7% respectively, and excessive alcohol drinkers 9%. Median (med) duration of HIV infection was 12.4 years, med CD4 count was 604/mm(3); 94% of Patients were on ARVs, 87% had undetectable viral load. Median sleeping time was 7 hours. Sleep disturbances (defined as PSQI score >5) were observed in 47% of the patients, more frequently in female (56.4%) than in male (43.9%) (p<0.05) and moderate to serious depressive symptoms (BDI score>19) in 19.7% of the patients. In multivariate analysis, factors associated with sleep disturbances (p<0.05) were depression (odds ratio [OR] 4.6; 95% confidence interval [CI] 3.2-6.8), male gender (OR 0.7; CI 0.5-0.9), active employment (OR 0.7; CI 0.5-0.9), living single (OR 1.5; CI 1.2-2.0), tobacco-smoking (OR 1.3; CI 1.0-1.8), duration of HIV infection (>10 vs. <10 y.) (OR 1.5; CI 1.1-2.0), ARV regimen containing nevirapine (OR 0.7; CI 0.5-0.9) or efavirenz (OR 0.5; CI 0.3-0.7). CONCLUSIONS: Prevalence of sleep disturbances is high in this HIV population and roughly similar to the French population. Associated factors are rather related to social and psychological status than HIV infection. Depression is frequent and should be taken in care to improve sleep quality.