Bismuth telluride (Bi2Te3) based alloys are preferred thermoelectric materials for room temperature thermoelectric applications. Electrical transport and thermopower properties of n-type ...nanostructured BixSb2-xTe3 films were tuned by post-growth heat treatment. We report that annealing of sputter-deposited nanostructured Bi0.7Sb1.3Te3 films lead to several-fold increases in thermoelectric power factor α2σ, where σ is electronic conductivity and α is Seebeck coefficient. Annealing at Tanneal = 200 °C nearly quadruples the power factor to α2σ = 3.1 μW cm−1 K−2. Spectroscopy and microscopy analyses indicate that the power factor increase is attributable to ~50% decrease in the Bi/Sb ratio, and grain growth, which increase the charge carrier concentration and mobility. The observed Bi depletion is contrary to annealing-induced Te depletion reported in p-type films. For Tanneal > 200 °C, although continued Bi depletion increases σ, a precipitous decrease in α sharply lowers the power factor, yielding tenfold lower α2σ for Tanneal = 400 °C than the as-deposited films. Our findings indicate that post-deposition annealing is a potent way to tune the thermoelectric properties of n-type Bi2Te3-based alloy films to fabricate devices for high-efficiency solid-state refrigeration and power harvesting from waste heat.
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•Compositional, microstructural and thermoelectric properties of nanostructured n-type bismuth antimony telluride (BixSb2-xTe3)•Multifold enhancement in thermoelectric power factor (PF) in BixSb2-xTe3 films•PF enhancement correlates with annealing-induced grain growth and Bi depletion.•Thermal annealing potent way to improve PF by tuning composition and microstructure
Epidemiological studies have associated chronic exposure to arsenic (As) from drinking water with increased risk of hypertension. However, evidence of an association between As exposure from food and ...hypertension risks is sparse. To quantify the association between daily As intake from both food (rice, wheat and potatoes) and drinking water (Aswater) along with total exposure (Astotal) and hypertension risks in a study population in Bihar, India, we conducted an individual level cross-sectional analysis between 2017 and 2019 involving 150 participants. Arsenic intake variables and three indicators of hypertension risks (general hypertension, low-density lipoprotein (LDL) and high-density lipoprotein (HDL)) were derived, and any relationship was quantified using a series of crude and multivariable log-linear or logistic regression models. The prevalence of general hypertension was 40% for the studied population. The median level of HDL was 45 mg/dL while median value of LDL was 114 mg/dL. Apart from a marginally significant positive relationship between As intake from rice and the changes of LDL (p-value = 0.032), no significant positive association between As intake and hypertension risks could be ascertained. In fact, Astotal was found to be associated with lower risks of general hypertension and higher levels of HDL (p-value = 0.020 and 0.010 respectively) whilst general hypertension was marginally associated with lower Aswater (p-value = 0.043). Due to limitations regarding study design and residual confounding, all observed marginal associations should be treated with caution.
•Cross-sectional study of hypertension risks associated with arsenic exposure from food and drinking water.•Total median arsenic intake of 36 µg/day for the study population in Bihar, India.•Total arsenic intake marginally associated with lower risks of general hypertension and higher levels of HDL.•Marginal positive relationship between arsenic intake from rice and level of LDL.•Limitations regarding study design and residual confounding problems should not be neglected.
•Electrochemical mott–Schottky method is a tool to characterize GaN surface states.•The barrier height, calculated from electrochemical data (Nd, Vfb) is an efficient indicator.•This method enables ...to distinguish plasma features on n-GaN.•The good repeatability obtained on robust conventional LETI process validates this electrochemical short loop characterization.•Electrochemical results confirm that the coupling of optimised RIE with ALE plasma processes (Steady A+ALE) induces less defects among the investigated RIE without additional treatment.
Plasma etching treatments are important steps in GaN-based devices fabrication, but can create defects on GaN surfaces. These surface defects can strongly alter device performances. The main objective of this work is to characterize the impact of different plasma etching recipes using an innovative electrochemical short loop based on Mott-Schottky (MS) method. The effect of defects has been studied in terms of Fermi Level pinning. Barrier height has been identified as a relevant criteria to describe surface damage induced by plasma treatment. Probing Conventional LETI plasma etching process with the Mott-Schottky method demonstrates a good reproducibility of the electrochemical data and confirms the reliability of the developed method. Various electrochemical tests conducted on 3 plasmas recipes demonstrated that: 1) the RIE etching is damaging, 2) the optimized RIE (Steady A) is less damaging than the other RIE (Steady B) and 3) the RIE associated with ALE process shows the least damaging plasma recipe, as expected.
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Background: Arsenic contamination of groundwater and food has become a challenging public health problem in the world. This study is a part of the UK-India bilateral project NutriSAM (2017-2020) and ...includes a population-based household survey in arsenic-affected areas of Bihar to determine how social and economic parameters and nutritional status are affecting the arsenic toxicity and vice-versa, in the exposed population of Bihar. Methods: A cross-sectional survey was completed in Bihar (n=192) and data were collected on social status, nutritional status, food habits, and health status including signs and symptoms of arsenic toxicity along with commonly consumed foods, and water samples from 20 villages of eight arsenic exposed districts during April 2017 - December 2020.Results: Findings of this study revealed that most of the participants were living in poor housing conditions (63%), as a joint family (84%), with poor financial status (84%) with an annual household income of less than one Lacs Indian Rupees, and most of them used agriculture wastes as kitchen fuel (73%) and untreated groundwater for drinking (63%). Cereals, especially wheat was the major food consumed, providing more than 60 per cent of total calories preceded by milk and milk products (10.5%), fruits and vegetables (9.4%), pulses (7.2%), and oil (6.6%). More than half of the participants (62%) did not meet the recommended calorie requirement. Nutritional adequacy in females from the lower socioeconomic class was significantly lower than the male and higher socioeconomic status group. The prevalence of undernutrition was significantly higher in males (21%) whereas overnutrition was more prevalent in females (31%). The estimated total arsenic exposure and arsenic toxicity were significantly higher in males, underweight, and participants from lower socioeconomic status groups. The folic acid, cooking oil, and vitamin K intake has a protective effect on arsenic toxicity while higher manganese intake was positively associated with arsenicosis. Conclusions: The male participants who had poor nutritional status and those from households with lower socioeconomic status were at an increased risk of arsenic-induced toxicity in an arsenic-exposed population of Bihar.
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•Arsenic exposure from wheat is substantial and increasing.•The home-made bread (chapati) contributed most of the wheat intake in Bihar, India.•Arsenic concentration in the wheat ...flour was not lower than in the grains.•Arsenic exposure from wheat-based food intake is of concern.
In arsenic (As) endemic areas of south-east Asia, where a subsistence rice-based diet is prevalent, As exposure from food is mainly focused on rice intake. However, consumption of wheat is substantial and increasing. We present a probabilistic assessment of increased cancer risk from wheat-based food intake in a study population of rural Bihar, India where As exposure is endemic. Total As in wheat grains (43.64 ± 48.19 µg/kg, n = 72) collected from 77 households across 19 villages was found to be lower than reported As in wheat grains from other south-east Asian countries but higher than a previous study from Bihar. This is the first study where As concentration in wheat flour was used for risk estimation, bearing in mind that it was the flour obtained after indigenous household processing of the grains that was used for making the home-made bread (chapati) which contributed 95% of wheat intake for the studied population. Interestingly, while 78% of the surveyed participants (n = 154) consumed rice every day, chapati was consumed every day by 99.5% of the participants. In contrast to previous studies, where As concentration in wheat grains was found to be lower than the flour due to the removal of the bran on grinding, we did not find any appreciable lowering of arsenic in the wheat flour (49.80 ± 74.08 µg/kg, n = 58), most likely due to external contamination during processing and grinding. Estimated gender adjusted excess lifetime cancer risk of 1.23 × 10−4 for the studied rural population of Bihar indicated risk higher than the 10−4–10−6 range, typically used by the USEPA as a threshold to guide regulatory values. Hence, our findings suggest As exposure from wheat-based food intake to be of concern not only in As endemic areas of rural Bihar but also in non-endemic areas with similar wheat-based diet due to public distribution of the wheat across India.
Extensive evidence of elevated arsenic (As) in the food-chain, mainly rice, wheat and vegetables exists. Nevertheless, the importance of exposure from food towards total As exposure and associated ...health risks in areas with natural occurring As in drinking water is still often neglected, and accordingly mitigations are largely focused on drinking water only. In this study, the contribution of food over drinking water to overall As exposure was estimated for As exposed populations in Bihar, India. Increased lifetime cancer risk was predicted using probabilistic methods with input parameters based on detailed dietary assessment and estimation of As in drinking water, cooked rice, wheat flour and potato collected from 91 households covering 19 villages. Median total exposure was 0.83 μg/kgBW/day (5th and 95th percentiles were 0.21 and 11.1 μg/kgBW/day) and contribution of food (median = 49%) to overall exposure was almost equal to that from drinking water (median = 51%). More importantly and contrary to previous studies, food was found to contribute more than drinking water to As exposure, even when drinking water As was above the WHO provisional guide value of 10 μg/L. Median and 95th percentile excess lifetime cancer risks from food intake were 1.89 × 10−4 and 7.32 × 10−4 respectively when drinking water As was below 10 μg/L and 4.00 × 10−4 and 1.83 × 10−3 respectively when drinking water As was above 10 μg/L. Our results emphasise the importance of food related exposure in As-endemic areas, and, perhaps surprisingly, particularly in areas with high As concentrations in drinking water – this being partly ascribed to increases in food As due to cooking in high As water. These findings are timely to stress the importance of removing As from the food chain and not just drinking water in endemic areas.
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•Food contributes equally as drinking water towards total As exposure in Bihar, India.•Cooked rice was the most significant As contributor to food exposure.•With increase in As concentrations in drinking water As exposure from food increased.•Median excess lifetime cancer risk of 2 per 10,000, from food As exposure in Bihar.
Surface states and contamination affects the efficiency of Gallium Nitride (GaN) based devices such as HEMTs, LEDs, photodetectors etc. In this work, several wet chemical treatment has been performed ...for the surface treatment of p-GaN, in order to achieve low-resistance ohmic contacts. The effect of surface treatment is observed by studying the flatband potential across the p-GaN/electrolyte interface via, electrochemical characterization. The electrochemical method of “Mott-Schottky characterization” gives simple and quick way of analysing the effect of different treatments, without the need of device fabrication. The effect of surface treatment are further investigated via, X-ray Photoelectron Spectroscopy and Atomic Force Microscopy. The potential surface treatments from experimental findings are integrated into device processing steps in order to realize effect of surface treatment on the p-GaN/metal contacts. The electrochemical characterization shows that HCl results in least flatband potential. Further, The electrical test shows that HCl treatment results in significant orders of magnitude improvement in contact resistance and electrical performance of the devices. This shows that short loop electrochemical characterization can be used for predicting surface treatment in order to improve electrical characteristics of the device.
Nowadays, Electro-spinning has gained an increased attention towards gas sensing material, battery and solar cells. Among the other one dimensional nanostructures, nano-fibers have an advantage of ...large surface to volume ratio, long axial ratio, large porosity and good mechanical properties. The metal oxides are extremely important technological materials for use in electronic and photonic devices. Electrospinning method is well due to its easier performation and mass production of fibers and variety of applications in various fields. This paper describes about the sensing studies of zinc oxide and nickel oxide nanocomposite fibers prepared by electro-spinning method. Polyvinyl Alcohol is used as a polymer to form fibers of zinc oxide and nickel oxide nanocomposite which was deposited on the glass substrate at room temperature. The basic characterization studies and gas sensing studies of as-spun fibers on formaldehyde and ammonia were studied.
This book constitutes the refereed proceedings of the 9th International Colloquium on Theoretical Aspects of Computing, ICTAC 2012 held in Bangalore, India, in September 2012. The 16 revised full ...papers presented together with the abstracts of three keynote talks were carefully reviewed and selected from 73 submissions. The papers cover various topics related to both theoretical aspects of computing and the exploitation of theory through methods and tools for system development.
Path Loss Model for UAV-Assisted RFET Suman, Suraj; Kumar, Sidharth; De, Swades
IEEE communications letters,
10/2018, Letnik:
22, Številka:
10
Journal Article
Recenzirano
In this letter, we develop channel models for unmanned aerial vehicle-aided air-to-ground (AtG) radio frequency energy transfer (RFET). AtG path loss plays a key role in RFET-based recharging of ...field nodes. Representative field environments consist of different types of built-up areas, namely, suburban, urban, dense urban, urban high-rise, and rural agriculture deployment scenarios. For emulating the built-up areas, ITU-R recommendations are considered, whereas for rural agricultural field deployment scenario, dynamics of vegetation growth with time is considered. Accuracy of the proposed path loss models are validated by conducting real AtG radio frequency transmission experiments in emulated suburban and agricultural fields.
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