Oscillating and star-shaped drops levitated by an air-flow

We investigate the spontaneous oscillations of drops levitated above an air cushion, eventually inducing a breaking of axisymmetry and the appearance of “star drops”. This is strongly reminiscent of the Leidenfrost stars that are observed for drops floating above a hot substrate. The key advantage of this work is that we inject the airflow at a constant rate below the drop, thus eliminating thermal effects and allowing for a better control of the flow rate. We perform experiments with drops of different viscosities and observe stable states, oscillations, and chimney instabilities. We find that for a given drop size the instability appears above a critical flow rate, where the latter is largest for small drops. All these observations are reproduced by numerical simulations, where we treat the drop using potential flow and the gas as a viscous lubrication layer. Qualitatively, the onset of instability agrees with the experimental results, although the typical flow rates are too large by a factor 10. Our results demonstrate that thermal effects are not important for the formation of star drops and strongly suggest a purely hydrodynamic mechanism for the formation of Leidenfrost stars

Crystal Growth and Unusual Electronic Transport Properties of Some Reduced Molybdenum Oxides with Bi-Octahedral Mo10 Clusters

Single crystals of AM05O3 (A = Ca, Sr, La-Gd), suitable for electrical conductivity measurements have been grown by high temperature and fused salt electrolytic techniques. The structures of all of these compounds are dominated by the presence of bi-octahedral clusters of Mo atoms joined together parallel to the monoclinic a axis, forming infinite chains. Temperature dependent electrical resistivity measurements on AMo5Og (A = La, Ce, Pr, Nd, Sm) show anomalous metal-semiconductor transitions near 180 and 30 K. The resistivities of the Eu and Gd analogues are different, in that the former is semiconducting while the latter shows a weak anomaly ~ 110 K. The Ca and Sr analogues are also semiconducting in the range 20-300 K. The electrical conductivity of these phases appears to be closely related to the inter-cluster separation and the number of metal-cluster electrons. The magnetic susceptibility of these compounds show no anomalies at the temperatures corresponding to the transitions seen in their electrical resistivities. The magnetic susceptibility of LaMosOg shows a small decrease in the !y (dy/dT) vs T plot in the vicinity of ~ 150 K

Absorption Enhancement in Organic-Inorganic Halide Perovskite Films with Embedded Plasmonic Gold Nanoparticles

We report on the numerical analysis of solar absorption enhancement in organic-inorganic halide perovskite films embedding plasmonic gold nanoparticles. The effect of particle size and concentration is analyzed in realistic systems in which random particle location within the perovskite film and the eventual formation of dimers are also taken into account. We find a maximum integrated solar absorption enhancement of ∼10% in perovskite films of 200 nm thickness and ∼6% in 300 nm films, with spheres of radii 60 and 90 nm, respectively, in volume concentrations of around 10% in both cases. We show that the presence of dimers boosts the absorption enhancement up to ∼12% in the thinnest films considered. Absorption reinforcement arises from a double contribution of plasmonic near-field and scattering effects, whose respective weight can be discriminated and evaluated from the simulations.Peer Reviewe

Spectrum of Illness in International Migrants Seen at GeoSentinel Clinics in 1997-2009, Part 2: Migrants Resettled Internationally and Evaluated for Specific Health Concerns

Of 7629 migrants, one third were infected with tuberculosis (22% active, 10% latent), one quarter with a variety of parasites (malaria 7%, schistosomes 6%, Strongyloides 5%, miscellaneous 5%), and 17% with chronic viral hepatitis (12% hepatitis B, 5% hepatitis C

Systematic review of studies generating individual participant data on the efficacy of drugs for treating soil-transmitted helminthiases and the case for data-sharing

Preventive chemotherapy and transmission control (PCT) by mass drug administration is the cornerstone of the World Health Organization (WHO)’s policy to control soil-transmitted helminthiases (STHs) caused by Ascaris lumbricoides (roundworm), Trichuris trichiura (whipworm) and hookworm species (Necator americanus and Ancylostama duodenale) which affect over 1 billion people globally. Despite consensus that drug efficacies should be monitored for signs of decline that could jeopardise the effectiveness of PCT, systematic monitoring and evaluation is seldom implemented. Drug trials mostly report aggregate efficacies in groups of participants, but heterogeneities in design complicate classical meta-analyses of these data. Individual participant data (IPD) permit more detailed analysis of drug efficacies, offering increased sensitivity to identify atypical responses potentially caused by emerging drug resistance