Studies on temperature dependent semiconductor to metal transitions in ZnO thin films sparsely doped with Al

For a detailed study on the semiconductor to metal transition (SMT) in ZnO thin films doped with Al in the concentration range from 0.02 to 2%, we grew these films on (0001) sapphire substrates using sequential pulsed laser deposition. It was found that the Al concentration in the films increased monotonically with the ratio of ablation durations of the Alumina and ZnO targets used during the deposition. Using X-ray photo electron spectroscopy it was found that while most of the Al atoms occupy the Zn sites in the ZnO lattice, a small fraction of the Al also gets into the grain boundaries present in the films. The observed SMT temperature decreased from ~ 270 to ~ 50 K with increase in the Al concentration from 0.02 to 0.25 %. In the Al concentration range of ~ 0.5 to 2 % these doped ZnO films showed metallic behavior at all the temperatures without undergoing any SMT. A theoretical model based on thermal activation of electrons and electron scatterings due to the grain boundaries, ionic impurities and phonons has been developed to explain the observed concentration and temperature dependent SMT.Comment: 5 figures, 24 page

Are environmental factors for atopic eczema in ISAAC Phase Three due to reverse causation?

Some previously described environmental associations for atopic eczema (AE) may be due to reverse causation. We explored the role of reverse causation by comparing individual- and school-level results for multiple AE risk factors. ISAAC Phase Three surveyed children within schools (the sampling unit) on AE symptoms and potential risk factors. We assessed the effect of these risk factors on AE symptoms using mixed-effect logistic regression models, first with individual-level exposure data and second with school-level exposure prevalence. 546,348 children from 53 countries were included. At age 6-7 the strongest individual-level associations were with current paracetamol use (odds ratio=1.45, 95% confidence interval 1.37-1.54), which persisted at school-level (1.55, 1.10-2.21), antibiotics (1.41, 1.34-1.48) and early life paracetamol use (1.28, 1.21-1.36) with the former persisting at school-level while the latter was no longer observed (1.35, 1.00-1.82 and 0.94, 0.69-1.28 respectively). At age 13-14 the strongest associations at individual-level were with current paracetamol use (1.57, 1.51-1.63) and open-fire cooking (1.46, 1.33-1.62); both were stronger at school-level (2.57, 1.84-3.59 and 2.38, 1.52-3.73 respectively). Association with exposure to heavy traffic (1.31, 1.27-1.36) also persisted at school-level (1.40, 1.07-1.82). Most individual- and school level effects were consistent tending to exclude reverse causation

Are environmental risk factors for current wheeze in the International Study of Asthma and Allergies in Childhood (ISAAC) phase three due to reverse causation?

BACKGROUND: Phase Three of the International Study of Asthma and Allergies in Childhood (ISAAC) measured the global prevalence of symptoms of asthma in children. We undertook comprehensive analyses addressing risk factors for asthma symptoms in combination, at both the individual and the school level, to explore the potential role of reverse causation due to selective avoidance or confounding by indication. OBJECTIVE: To explore the role of reverse causation in risk factors of asthma symptoms. METHODS: We compared two sets of multilevel logistic regression analyses, using (a) individual level exposure data and (b) school level average exposure (ie prevalence), in two different age groups. In individual level analyses, reverse causation is a possible concern if individual level exposure statuses were changed as a result of asthma symptoms or diagnosis. School level analyses may suffer from ecologic confounding, but reverse causation is less of a concern because individual changes in exposure status as a result of asthma symptoms would only have a small effect on overall school exposure levels. RESULTS: There were 131 924 children aged 6-7 years (2428 schools, 25 countries) with complete exposure, outcome and confounder data. The strongest associations in individual level analyses (fully adjusted) were for current paracetamol use (odds ratio = 2.06; 95% confidence interval 1.97-2.16), early life antibiotic use (1.65; 1.58-1.73) and open fire cooking (1.44; 1.26-1.65). In school level analyses, these risk factors again showed increased risks. There were 238 586 adolescents aged 13-14 years (2072 schools, 42 countries) with complete exposure, outcome and confounder data. The strongest associations in individual level analyses (fully adjusted) were for current paracetamol use (1.80; 1.75-1.86), cooking on an open fire (1.32; 1.22-1.43) and maternal tobacco use (1.23; 1.18-1.27). In school level analyses, these risk factors again showed increased risks. CONCLUSIONS & CLINICAL RELEVANCE: These analyses strengthen the potentially causal interpretation of previously reported individual level findings, by providing evidence against reverse causation

Are environmental factors for atopic eczema in ISAAC Phase Three due to reverse causation?

Some previously described environmental associations for atopic eczema (AE) may be due to reverse causation. We explored the role of reverse causation by comparing individual- and school-level results for multiple AE risk factors. ISAAC Phase Three surveyed children within schools (the sampling unit) on AE symptoms and potential risk factors. We assessed the effect of these risk factors on AE symptoms using mixed-effect logistic regression models, first with individual-level exposure data and second with school-level exposure prevalence. 546,348 children from 53 countries were included. At age 6-7 the strongest individual-level associations were with current paracetamol use (odds ratio=1.45, 95% confidence interval 1.37-1.54), which persisted at school-level (1.55, 1.10-2.21), antibiotics (1.41, 1.34-1.48) and early life paracetamol use (1.28, 1.21-1.36) with the former persisting at school-level while the latter was no longer observed (1.35, 1.00-1.82 and 0.94, 0.69-1.28 respectively). At age 13-14 the strongest associations at individual-level were with current paracetamol use (1.57, 1.51-1.63) and open-fire cooking (1.46, 1.33-1.62); both were stronger at school-level (2.57, 1.84-3.59 and 2.38, 1.52-3.73 respectively). Association with exposure to heavy traffic (1.31, 1.27-1.36) also persisted at school-level (1.40, 1.07-1.82). Most individual- and school level effects were consistent tending to exclude reverse causation

A new aircraft architecture based on the ACHEON Coanda effect nozzle: flight model and energy evaluation

Purpose Aeronautic transport has an effective necessity of reducing fuel consumption and emissions to deliver efficiency and competitiveness driven by today commercial and legislative requirements. Actual aircraft configurations scenario allows envisaging the signs of a diffused technological maturity and they seem very near their limits. This scenario clearly shows the necessity of radical innovations with particular reference to propulsion systems and to aircraft architecture consequently. Methods This paper presents analyses and discusses a promising propulsive architecture based on an innovative nozzle, which allows realizing the selective adhesion of two impinging streams to two facing jets to two facing Coanda surfaces. This propulsion system is known with the acronym ACHEON (Aerial Coanda High Efficiency Orienting Nozzle). This paper investigates how the application of an all-electric ACHEONs propulsion system to a very traditional commuter aircraft can improve its relevant performances. This paper considers the constraints imposed by current state-of-the-art electric motors, drives, storage and conversion systems in terms of both power/energy density and performance and considers two different aircraft configurations: one using battery only and one adopting a more sophisticated hybrid cogeneration. The necessity of producing a very solid analysis has forced to limit the deflection of the jet in a very conservative range (±15°) with respect to the horizontal. This range can be surely produced also by not optimal configurations and allow minimizing the use of DBD. From the study of general flight dynamics equations of the aircraft in two-dimensional form it has been possible to determine with a high level of accuracy the advantages that ACHEON brings in terms of reduced stall speed and of reduced take-off and landing distances. Additionally, it includes an effective energy analysis focusing on the efficiency and environmental advantages of the electric ACHEON based propulsion by assuming the today industrial grade high capacity batteries with a power density of 207 Wh/kg. Results It has been clearly demonstrated that a short flight could be possible adopting battery energy storage, and longer duration could be possible by adopting a more sophisticated cogeneration system, which is based on cogeneration from a well-known turboprop, which is mostly used in helicopter propulsion. This electric generation system can be empowered by recovering the heat and using it to increase the temperature of the jet. It is possible to transfer this considerable amount of heat to the jet by convection and direct fluid mixing. In this way, it is possible to increase the energy of the jets of an amount that allows more than recover the pressure losses in the straitening section. In this case, it is then possible to demonstrate an adequate autonomy of flight and operative range of the aircraft. The proposed architecture, which is within the limits of the most conservative results obtained, demonstrates significant additional benefits for aircraft manoeuvrability. In conclusion, this paper has presented the implantation of ACHEON on well-known traditional aircraft, verifying the suitability and effectiveness of the proposed system both in terms of endurance with a cogeneration architecture and in terms of manoeuvrability. It has demonstrated the potential of the system in terms of both takeoff and landing space requirements. Conclusions This innovation opens interesting perspectives for the future implementation of this new vector and thrust propulsion system, especially in the area of greening the aeronautic sector. It has also demonstrated that ACHEON has the potential of renovating completely a classic old aircraft configuration such as the one of Cessna 402