585 research outputs found

    Hydrogen adsorption and cohesive energy of single-walled carbon nanotubes

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    Hydrogen adsorption on crystalline ropes of carbon single-walled nanotubes (SWNT) was found to exceed 8 wt.%, which is the highest capacity of any carbon material. Hydrogen is first adsorbed on the outer surfaces of the crystalline ropes. At pressures higher than about 40 bar at 80 K, however, a phase transition occurs where there is a separation of the individual SWNTs, and hydrogen is physisorbed on their exposed surfaces. The pressure of this phase transition provides a tube-tube cohesive energy for much of the material of 5 meV/C atom. This small cohesive energy is affected strongly by the quality of crystalline order in the ropes

    Missileborne Artificial Vision System (MAVIS)

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    Several years ago when INTEL and China Lake designed the ETANN chip, analog VLSI appeared to be the only way to do high density neural computing. In the last five years, however, digital parallel processing chips capable of performing neural computation functions have evolved to the point of rough equality with analog chips in system level computational density. The Naval Air Warfare Center, China Lake, has developed a real time, hardware and software system designed to implement and evaluate biologically inspired retinal and cortical models. The hardware is based on the Adaptive Solutions Inc. massively parallel CNAPS system COHO boards. Each COHO board is a standard size 6U VME card featuring 256 fixed point, RISC processors running at 20 MHz in a SIMD configuration. Each COHO board has a companion board built to support a real time VSB interface to an imaging seeker, a NTSC camera, and to other COHO boards. The system is designed to have multiple SIMD machines each performing different corticomorphic functions. The system level software has been developed which allows a high level description of corticomorphic structures to be translated into the native microcode of the CNAPS chips. Corticomorphic structures are those neural structures with a form similar to that of the retina, the lateral geniculate nucleus, or the visual cortex. This real time hardware system is designed to be shrunk into a volume compatible with air launched tactical missiles. Initial versions of the software and hardware have been completed and are in the early stages of integration with a missile seeker

    Galactic Plane Hα\alpha Surveys: IPHAS & VPHAS+

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    The optical Galactic Plane Hα\alpha surveys IPHAS and VPHAS+ are dramatically improving our understanding of Galactic stellar populations and stellar evolution by providing large samples of stars in short lived, but important, evolutionary phases, and high quality homogeneous photometry and images over the entire Galactic Plane. Here I summarise some of the contributions these surveys have already made to our understanding of a number of key areas of stellar and Galactic astronomy.Comment: 5 pages, 2 figures, refereed proceeding of the "The Universe of Digital Sky Surveys" conference, November 2014, to be published in the Astrophysics and Space Science Proceeding

    Variability in the clinical management of iron deficiency anaemia in older adults : results from a survey of UK specialists in the care of older people

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    Acknowledgements We would like to thank the British Geriatrics Society for hosting the survey link and formally endorsing the survey through its electronic communications. We gratefully acknowledge the participants of the survey. Funding This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.Peer reviewedPublisher PD

    Metal hydrides as electrode/catalyst materials for oxygen evolution/reduction in electrochemical devices

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    An at least ternary metal alloy of the formula, AB.sub.(5-Y)X(.sub.y), is claimed. In this formula, A is selected from the rare earth elements, B is selected from the elements of groups 8, 9, and 10 of the periodic table of the elements, and X includes at least one of the following: antimony, arsenic, and bismuth. Ternary or higher-order substitutions, to the base AB.sub.5 alloys, that form strong kinetic interactions with the predominant metals in the base metal hydride are used to form metal alloys with high structural integrity after multiple cycles of hydrogen sorption

    Development and external validation of an acute kidney injury risk score for use in the general population

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    Background: Improving recognition of patients at increased risk of acute kidney injury (AKI) in the community may facilitate earlier detection and implementation of proactive prevention measures that mitigate the impact of AKI. The aim of this study was to develop and externally validate a practical risk score to predict the risk of AKI in either hospital or community settings using routinely collected data. Methods: Routinely collected linked datasets from Tayside, Scotland, were used to develop the risk score and datasets from Kent in the UK and Alberta in Canada were used to externally validate it. AKI was defined using the Kidney Disease: Improving Global Outcomes serum creatinine–based criteria. Multivariable logistic regression analysis was performed with occurrence of AKI within 1 year as the dependent variable. Model performance was determined by assessing discrimination (C-statistic) and calibration. Results: The risk score was developed in 273 450 patients from the Tayside region of Scotland and externally validated into two populations: 218 091 individuals from Kent, UK and 1 173 607 individuals from Alberta, Canada. Four variables were independent predictors for AKI by logistic regression: older age, lower baseline estimated glomerular filtration rate, diabetes and heart failure. A risk score including these four variables had good predictive performance, with a C-statistic of 0.80 [95% confidence interval (CI) 0.80–0.81] in the development cohort and 0.71 (95% CI 0.70–0.72) in the Kent, UK external validation cohort and 0.76 (95% CI 0.75–0.76) in the Canadian validation cohort. Conclusion We have devised and externally validated a simple risk score from routinely collected data that can aid both primary and secondary care physicians in identifying patients at high risk of AKI

    On the dispersionless Kadomtsev-Petviashvili equation in n+1 dimensions: exact solutions, the Cauchy problem for small initial data and wave breaking

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    We study the (n+1)-dimensional generalization of the dispersionless Kadomtsev-Petviashvili (dKP) equation, a universal equation describing the propagation of weakly nonlinear, quasi one dimensional waves in n+1 dimensions, and arising in several physical contexts, like acoustics, plasma physics and hydrodynamics. For n=2, this equation is integrable, and it has been recently shown to be a prototype model equation in the description of the two dimensional wave breaking of localized initial data. We construct an exact solution of the n+1 dimensional model containing an arbitrary function of one variable, corresponding to its parabolic invariance, describing waves, constant on their paraboloidal wave front, breaking simultaneously in all points of it. Then we use such solution to build a uniform approximation of the solution of the Cauchy problem, for small and localized initial data, showing that such a small and localized initial data evolving according to the (n+1)-dimensional dKP equation break, in the long time regime, if and only if n=1,2,3; i.e., in physical space. Such a wave breaking takes place, generically, in a point of the paraboloidal wave front, and the analytic aspects of it are given explicitly in terms of the small initial data.Comment: 20 pages, 10 figures, few formulas adde

    The Interplay between Social and Ecological Determinants of Mental Health for Children and Youth in the Climate Crisis

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    Children and youth are showing increasing levels of mental health distress due to the climate crisis, characterized by feelings of sadness, guilt, changes in sleep and appetite, difficulty concentrating, solastalgia, and disconnection from land. To gain a deeper understanding of the relationship between climate change and children and youth’s mental health, we conducted a rapid review and a thematic analysis of the results in NVivo 12. Our findings show that children and youth experience a plethora of direct and indirect effects from climate change and this impacts their mental wellbeing in diverse and complex ways. Young people also have varied perceptions of climate change based on their social locations and many are dealing with feelings of immense worry and eco-anxiety. The mental health impacts of climate change on children/youth are tied to Social Determinants of Health (SDoH) but also need to be understood in relation to the Ecological Determinants of Health (EDoH). Through an eco-social lens, this paper explores these conceptual issues and uses them to provide a framework for understanding the interplay of social and ecological determinants of mental health for children/youth

    Ultrafine hydrogen storage powders

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    A method of making hydrogen storage powder resistant to fracture in service involves forming a melt having the appropriate composition for the hydrogen storage material, such, for example, LaNi5 and other AB5 type materials and AB5+x materials, where x is from about -2.5 to about +2.5, including x=0, and the melt is gas atomized under conditions of melt temperature and atomizing gas pressure to form generally spherical powder particles. The hydrogen storage powder exhibits improved chemcial homogeneity as a result of rapid solidfication from the melt and small particle size that is more resistant to microcracking during hydrogen absorption/desorption cycling. A hydrogen storage component, such as an electrode for a battery or electrochemical fuel cell, made from the gas atomized hydrogen storage material is resistant to hydrogen degradation upon hydrogen absorption/desorption that occurs for example, during charging/discharging of a battery. Such hydrogen storage components can be made by consolidating and optionally sintering the gas atomized hydrogen storage powder or alternately by shaping the gas atomized powder and a suitable binder to a desired configuration in a mold or die

    On the Theory of Relativistic Strong Plasma Waves

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    The influence of motion of ions and electron temperature on nonlinear one-dimensional plasma waves with velocity close to the speed of light in vacuum is investigated. It is shown that although the wavebreaking field weakly depends on mass of ions, the nonlinear relativistic wavelength essentially changes. The nonlinearity leads to the increase of the strong plasma wavelength, while the motion of ions leads to the decrease of the wavelength. Both hydrodynamic approach and kinetic one, based on Vlasov-Poisson equations, are used to investigate the relativistic strong plasma waves in a warm plasma. The existence of relativistic solitons in a thermal plasma is predicted.Comment: 13 pages, 8 figure
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