Optimal quantum interference thermoelectric heat engine with edge states

We show theoretically that a thermoelectric heat engine, operating exclusively due to quantum-mechanical interference, can reach optimal linear-response performance. A chiral edge state implementation of a close-to-optimal heat engine is proposed in an electronic Mach-Zehnder interferometer with a mesoscopic capacitor coupled to one arm. We demonstrate that the maximum power and corresponding efficiency can reach 90\% and 83\%, respectively, of the theoretical maximum. The proposed heat engine can be realized with existing experimental techniques and has a performance robust against moderate dephasing.Comment: 5 pages, 3 figures, published versio

Hybrid Microwave-Cavity Heat Engine

We propose and analyze the use of hybrid microwave cavities as quantum heat engines. A possible realization consists of two macroscopically separated quantum dot conductors coupled capacitively to the fundamental mode of a microwave cavity. We demonstrate that an electrical current can be induced in one conductor through cavity-mediated processes by heating up the other conductor. The heat engine can reach Carnot efficiency with optimal conversion of heat to work. When the system delivers the maximum power, the efficiency can be a large fraction of the Carnot efficiency. The heat engine functions even with moderate electronic relaxation and dephasing in the quantum dots. We provide detailed estimates for the electrical current and output power using realistic parameters.Comment: 5 pages, 3 figures, final version as published in Phys. Rev. Let

Der Einfluss sozioökonomischer und soziogeographischer Determinanten auf das Risiko systemischer bakterieller Infektionen bei Kindern – Eine Fall-Kontroll-Studie in der periurbanen Zone der ghanaischen Großstadt Kumasi

Systemische bakterielle Infektionen tragen substantiell zur kindlichen Morbidität und Mortalität in Subsahara-Afrika bei. Ziel dieser Studie ist es, den Einfluss soziogeographischer und sozioökonomischer Faktoren auf das Risiko und Erregerspektrum systemischer bakterieller Infektionen bei Kindern in Ghana zu untersuchen. Kinder unter 15 Jahren, die sich mit Fieber ≥ 38°C in einem Krankenhaus in der peri-urbanen Zone der ghanaischen Großstadt Kumasi vorstellten, wurden in die Studie eingeschlossen. Es erfolgte eine Blutentnahme zur Malariadiagnostik und Bakterienkultur. Der sozioökomimischen Status der Patienten wurde mittels Hauptkomponentenanalyse berechnet. Zur Messung des Urbanitätsgrades des Wohnortes wurde eine numerischen Skala verwendet, die Schlüssel-Charakteristika des städtischen/ländlichen Siedlungsraumes quantifiziert. In der anschließenden Fall-Kontroll-Analyse wurden Patienten mit Bakteriämie als Fälle und Patienten ohne Bakteriämie entsprechend als Kontrollen definiert. Es wurden 2.306 Krankenhauskonsultationen in die Analyse eingeschlossen. Bei 72 (3,1%) Probanden wurde eine Bakteriämie festgestellt. Nicht-typhoide Salmonellen (NTS; n = 24; 33.3%) und Salmonella Typhi (n = 18; 25.0%) waren die häufigsten Isolate. In der logistischen Regression war Bakteriämie negativ mit Urbanität (Odds ratio [OR] = 0.8; 95% Konfidenzintervall [KI]: 0.7–1.0) und sozioökonomischem Status (OR = 0.8; 95% KI: 0.6–0.9) assoziiert. Beide Assoziationen waren stärker, wenn nur Fälle mit NTS-Bakteriämie in die Analyse eingingen (OR = 0.5; 95% KI: 0.3–0.8 und OR = 0.6; 95% KI: 0.4–1.0). Die Ergebnisse der Studie verdeutlichen die wichtigen Einfluss individueller und gesellschaftlicher Faktoren auf das Risiko systemischer bakterieller Infektionen – und besonders systemischer NTS-Infektionen – bei Kindern in Ghana

a cross-sectional study on the association between urbanicity and the acquisition of immunity

Background Malaria incidence has declined considerably over the last decade. This is partly due to a scale-up of control measures but is also attributed to increasing urbanization. This study aimed to analyse the association between malaria and urbanization and the effect of urbanicity on the acquisition of semi-immunity. Methods In 2012, children with fever presenting to St Michael’s Hospital Pramso/Ghana were recruited. The malaria-positive-fraction (MPF) of fever cases was calculated on community-level to approximate the malaria risk. The mean age of malaria cases was calculated for each community to estimate the acquisition of semi-immunity. The level of urbanicity for the communities was calculated and associations between MPF, urbanicity and immunity were modelled using linear regression. Results Twenty-six villages were included into the study with a mean MPF of 35 %. A linear decrease of 5 % (95 % CI: 4–6 %) in MPF with every ten-point increase in urbanicity was identified. The mean age of malaria patients increased by 2.9 months (95 % CI: 1.0–4.8) with every ten-point increase in urbanicity. Discussion The results confirm an association between an increase in urbanicity and declining malaria risk and demonstrate that the acquisition of semi-immunity is heterogeneous on a micro- epidemiological scale and is associated with urbanicity

Urbanicity and Paediatric Bacteraemia in Ghana-A Case-Control Study within a Rural-Urban Transition Zone.

BACKGROUND: Systemic bacterial infections are a major cause of paediatric febrile illness in sub-Saharan Africa. Aim of this study was to assess the effects of social and geographical determinants on the risk of bacteraemia in a rural-urban transition zone in Ghana. METHODS: Children below 15 years of age with fever were recruited at an outpatient department in the suburban belt of Kumasi, Ghana's second largest city. Blood was taken for bacterial culture and malaria diagnostics. The socio-economic status of participants was calculated using Principle Component Analysis. A scale, based on key urban characteristics, was established to quantify urbanicity for all communities in the hospital catchment area. A case-control analysis was conducted, where children with and without bacteraemia were cases and controls, respectively. RESULTS: Bacteraemia was detected in 72 (3.1%) of 2,306 hospital visits. Non-typhoidal Salmonella (NTS; n = 24; 33.3%) and Salmonella typhi (n = 18; 25.0%) were the most common isolates. Logistic regression analysis showed that bacteraemia was negatively associated with urbanicity (odds ratio [OR] = 0.8; 95% confidence interval [CI]: 0.7-1.0) and socio-economic status (OR = 0.8; 95% CI: 0.6-0.9). Both associations were stronger if only NTS infections were used as cases (OR = 0.5; 95% CI: 0.3-0.8 and OR = 0.6; 95% CI: 0.4-1.0, respectively). CONCLUSIONS: The results of this study highlight the importance of individual as well as community factors as independent risk factors for invasive bacterial infection (IBI) and especially NTS. Epidemiological data support physicians, public health experts and policy makers to identify disease prevention and treatment needs in order to secure public health in the transitional societies of developing countries

Spatial heterogeneity of malaria in Ghana: a cross-sectional study on the association between urbanicity and the acquisition of immunity.

BACKGROUND: Malaria incidence has declined considerably over the last decade. This is partly due to a scale-up of control measures but is also attributed to increasing urbanization. This study aimed to analyse the association between malaria and urbanization and the effect of urbanicity on the acquisition of semi-immunity. METHODS: In 2012, children with fever presenting to St Michael's Hospital Pramso/Ghana were recruited. The malaria-positive-fraction (MPF) of fever cases was calculated on community-level to approximate the malaria risk. The mean age of malaria cases was calculated for each community to estimate the acquisition of semi-immunity. The level of urbanicity for the communities was calculated and associations between MPF, urbanicity and immunity were modelled using linear regression. RESULTS: Twenty-six villages were included into the study with a mean MPF of 35 %. A linear decrease of 5 % (95 % CI: 4-6 %) in MPF with every ten-point increase in urbanicity was identified. The mean age of malaria patients increased by 2.9 months (95 % CI: 1.0-4.8) with every ten-point increase in urbanicity. DISCUSSION: The results confirm an association between an increase in urbanicity and declining malaria risk and demonstrate that the acquisition of semi-immunity is heterogeneous on a micro-epidemiological scale and is associated with urbanicity

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

Steady-state chlorophyll a fluorescence detection from canopy derivative reflectance and double-peak red-edge effects

A series of experiments carried out in a controlled environment facility to induce steady-state chlorophyll a fluorescence variation demonstrate that natural fluorescence emission is observable on the derivative reflectance spectra as a double-peak feature in the 690–710 nm spectral region. This work describes that the unexplained double-peak feature previously seen on canopy derivative reflectance is due entirely to chlorophyll fluorescence (CF) effects, demonstrating the importance of derivative methods for fluorescence detection in vegetation. Measurements were made in a controlled environmental chamber where temperature and humidity were varied through the time course of the experiments in both short- and long-term trials using Acer negundo ssp. californium canopies. Continuous canopy reflectance measurements were made with a spectrometer on healthy and stressed vegetation, along with leaf-level steady-state fluorescence measurements with the PAM-2000 Fluorometer during both temperature–stress induction and recovery stages. In 9-h trials, temperatures were ramped from 10 to 35 jC and relative humidity adjusted from 92% to 42% during stress induction, returning gradually to initial conditions during the recovery stage. Canopy reflectance difference calculations and derivative analysis of reflectance spectra demonstrate that a double-peak feature created between 688, 697 and 710 nm on the derivative reflectance is a function of natural steady-state fluorescence emission, which gradually diminished with induction of maximum stress. Derivative reflectance indices based on this doublepeak feature are demonstrated to track natural steady-state fluorescence emission as quantified by two indices, the double-peak index (DPi) and the area of the double peak (Adp). Results obtained employing these double-peak indices from canopy derivative reflectance suggest a potential for natural steady-state fluorescence detection with hyperspectral data. Short- and long-term stress effects on the observed doublepeak derivative indices due to pigment degradation and canopy structure changes were studied, showing that both indices are capable of tracking steady-state fluorescence changes from canopy remote sensing reflectance.California Space Institute and NASA Space Grant ProgramPeer reviewe