Magnon-driven quantum-dot heat engine

We investigate a heat- to charge-current converter consisting of a single-level quantum dot coupled to two ferromagnetic metals and one ferromagnetic insulator held at different temperatures. We demonstrate that this nano engine can act as an optimal heat to spin-polarized charge current converter in an antiparallel geometry, while it acts as a heat to pure spin current converter in the parallel case. We discuss the maximal output power of the device and its efficiency.Comment: 6 pages, 4 figures, published version, selected as Editor's choic

From thermal rectifiers to thermoelectric devices

We discuss thermal rectification and thermoelectric energy conversion from the perspective of nonequilibrium statistical mechanics and dynamical systems theory. After preliminary considerations on the dynamical foundations of the phenomenological Fourier law in classical and quantum mechanics, we illustrate ways to control the phononic heat flow and design thermal diodes. Finally, we consider the coupled transport of heat and charge and discuss several general mechanisms for optimizing the figure of merit of thermoelectric efficiency.Comment: 42 pages, 22 figures, review paper, to appear in the Springer Lecture Notes in Physics volume "Thermal transport in low dimensions: from statistical physics to nanoscale heat transfer" (S. Lepri ed.

Detection of dicistroviruses RNA in blood of febrile Tanzanian children.

Fever is the leading cause of paediatric outpatient consultations in Sub-Saharan Africa. Although most are suspected to be of viral origin, a putative causative pathogen is not identified in over a quarter of these febrile episodes. Using a de novo assembly sequencing approach, we report the detection (15.4%) of dicistroviruses (DicV) RNA in sera collected from 692 febrile Tanzanian children. In contrast, DicV RNA was only detected in 1/77 (1.3%) plasma samples from febrile Tanzanian adults, suggesting that children could represent the primary susceptible population. Estimated viral load by specific quantitative real-time RT-PCR assay ranged from < 1.32E3 to 1.44E7 viral RNA copies/mL serum. Three DicV full-length genomes were obtained, and a phylogenetic analyse on the capsid region showed the presence of two clusters representing tentative novel genus. Although DicV-positive cases were detected throughout the year, a significantly higher positivity rate was observed during the rainy season. This study reveals that novel DicV RNA is frequently detected in the blood of Tanzanian children, paving the way for further investigations to determine if DicV possibly represent a new agent in humans

Comparison of body mass index with waist circumference and skinfold-based percent body fat in firefighters: adiposity classification and associations with cardiovascular disease risk factors

PurposeThis study aims to examine whether body mass index (BMI) overestimates the prevalence of overweight or obese firefighters when compared to waist circumference (WC) and skinfold-based percent body fat (PBF) and to investigate differential relationships of the three adiposity measures with other biological cardiovascular disease (CVD) risk factors.MethodsThe adiposity of 355 (347 males and eight females) California firefighters was assessed using three different measures. Other CVD risk factors (high blood pressure, high lipid profiles, high glucose, and low VO2 max) of the firefighters were also clinically assessed.ResultsThe prevalence of total overweight and obesity was significantly (p < 0.01) higher by BMI (80.4 %) than by WC (48.7 %) and by PBF (55.6 %) in male firefighters. In particular, the prevalence of overweight firefighters was much higher (p < 0.01) by BMI (57.3 %) than by WC (24.5 %) and PBF (38.3 %). 60-64 % of male firefighters who were assessed as normal weight by WC and PBF were misclassified as overweight by BMI. When overweight by BMI was defined as 27.5-29.9 kg/m(2) (vs. the standard definition of 25.0-29.9 kg/m(2)), the agreement of the adiposity classification increased between BMI and other two adiposity measures. Obese firefighters had the highest CVD risk profiles across all three adiposity measures. Only when overweight by BMI was defined narrowly, overweight firefighters had substantially higher CVD risk profiles. Obesity and overweight were less prevalent in female and Asian male firefighters.ConclusionsBMI overestimated the prevalence of total overweight and obesity among male firefighters, compared to WC and skinfold-based PBF. Overweight by BMI needs to be more narrowly defined, or the prevalence of BMI-based overweight (27.5-29.9 kg/m(2)) should be reported additionally for prevention of CVD among male firefighters