4,253 research outputs found

    Study protocol for a randomised controlled trial of electronic cigarettes versus nicotine patch for smoking cessation

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    PMCID: PMC3602285This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited

    Fibre Bundles and Generalised Dimensional Reduction

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    We study some geometrical and topological aspects of the generalised dimensional reduction of supergravities in D=11 and D=10 dimensions, which give rise to massive theories in lower dimensions. In these reductions, a global symmetry is used in order to allow some of the fields to have a non-trivial dependence on the compactifying coordinates. Global consistency in the internal space imposes topological restrictions on the parameters of the compactification as well as the structure of the space itself. Examples that we consider include the generalised reduction of the type IIA and type IIB theories on a circle, and also the massive ten-dimensional theory obtained by the generalised reduction of D=11 supergravity.Comment: 23 pages, Late

    Einstein-Weyl structures and Bianchi metrics

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    We analyse in a systematic way the (non-)compact four dimensional Einstein-Weyl spaces equipped with a Bianchi metric. We show that Einstein-Weyl structures with a Class A Bianchi metric have a conformal scalar curvature of constant sign on the manifold. Moreover, we prove that most of them are conformally Einstein or conformally K\"ahler ; in the non-exact Einstein-Weyl case with a Bianchi metric of the type VII0,VIIIVII_0, VIII or IXIX, we show that the distance may be taken in a diagonal form and we obtain its explicit 4-parameters expression. This extends our previous analysis, limited to the diagonal, K\"ahler Bianchi IXIX case.Comment: Latex file, 12 pages, a minor modification, accepted for publication in Class. Quant. Gra

    AGBT Advanced Counter-Rotating Gearbox Detailed Design Report

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    An Advanced Counter-Rotating (CR) Gearbox was designed and fabricated to evaluate gearbox efficiency, durability and weight characteristics for emerging propfan-powered airplanes. Component scavenge tests showed that a constant volume collector had high scavenge effectiveness, which was uneffected by added airflow. Lubrication tests showed that gearbox losses could be reduced by controlling the air/oil mixture and by directing the oil jets radially, with a slight axial component, into the sun/planet gears

    Radiation reaction and renormalization in classical electrodynamics of point particle in any dimension

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    The effective equations of motion for a point charged particle taking account of radiation reaction are considered in various space-time dimensions. The divergencies steaming from the pointness of the particle are studied and the effective renormalization procedure is proposed encompassing uniformly the cases of all even dimensions. It is shown that in any dimension the classical electrodynamics is a renormalizable theory if not multiplicatively beyond d=4. For the cases of three and six dimensions the covariant analogs of the Lorentz-Dirac equation are explicitly derived.Comment: minor changes in concluding section, misprints corrected, LaTeX2e, 15 page

    On Four-Point Functions of Half-BPS Operators in General Dimensions

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    We study four-point correlation functions of half-BPS operators of arbitrary weight for all dimensions d=3,4,5,6 where superconformal theories exist. Using harmonic superspace techniques, we derive the superconformal Ward identities for these correlators and present them in a universal form. We then solve these identities, employing Jack polynomial expansions. We show that the general solution is parameterized by a set of arbitrary two-variable functions, with the exception of the case d=4, where in addition functions of a single variable appear. We also discuss the operator product expansion using recent results on conformal partial wave amplitudes in arbitrary dimension.Comment: The discussion of the case d=6 expanded; references added/correcte

    Compounding Hazards and Intersecting Vulnerabilities: Experiences and Responses to Extreme Heat During COVID-19

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    Extreme heat is a major threat to human health worldwide. The COVID-19 pandemic, with its complexity and global reach, created unprecedented challenges for public health and highlighted societal vulnerability to hazardous hot weather. In this study, we used data from a three-wave nationally representative survey of 3036 American adults to examine how the COVID-19 pandemic affected extreme heat vulnerability during the summer of 2020. We used mixed effects models to examine the roles of socio-demographic characteristics and pandemic-related factors in the distribution of negative heat effects and experiences across the United States. The survey findings show that over a quarter of the US population experienced heat-related symptoms during the summer of 2020. Mixed effects models demonstrate that among all socio-economic groups, those who were most vulnerable were women, those in low-income households, unemployed or on furlough, and people who identify as Hispanic or Latino or as other non-white census categories (including Asian, American Indian or Alaska Native, Native Hawaiian or other Pacific Islander, and multi-racial US residents). The study findings indicate that millions of people in the US had difficulty coping with or responding to extreme heat because of the direct and indirect effects of the COVID-19 pandemic. Limited access to cooling as well as COVID-19 related social isolation played a major role in adverse heat health effects. Geographically, the South and the West of the US stood out in terms of self-reported negative heat effects. Overall, the study suggests that the intersection of two health hazards—extreme heat and coronavirus SARS-CoV2—amplified existing systemic vulnerabilities and expanded the demographic range of people vulnerable to heat stress

    Different Ways of Reading, or Just Making the Right Noises?

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    What does reading look like? Can learning to read be reduced to the acquisition of a set of isolable skills, or proficiency in reading be equated with the independence of the solitary, silent reader of prose fiction? These conceptions of reading and reading development, which figure strongly in educational policy, may appear to be simple common sense. But both ethnographic data and evidence from literary texts suggest that such paradigms offer, at most, a partial and ahistorical picture of reading. An important dimension, neglected in the dominant paradigms, is the irreducibly social quality of reading practices

    Peripheral photoplethysmography variability analysis of sepsis patients

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    Sepsis is associated with impairment in autonomic regulatory function. This work investigates the application of heart rate and photoplethysmogram (PPG) waveform variability analysis in differentiating two categories of sepsis, namely systemic inflammatory response syndrome (SIRS) and severe sepsis. Electrocardiogram-derived heart period (RRi) and PPG waveforms, measured from fingertips (Fin-PPG) and earlobes (Ear-PPG), of Emergency Department sepsis patients (n = 28) with different disease severity, were analysed by spectral technique, and were compared to control subjects (n = 10) in supine and 80° head-up tilted positions. Analysis of covariance (ANCOVA) was applied to adjust for the confounding factor of age. Low-frequency (LF, 0.04-0.15 Hz), mid-frequency (MF, 0.09-0.15 Hz) and high-frequency (HF, 0.15-0.60 Hz) powers were computed. The normalised MF power in Ear-PPG (MFnu Ear) was significantly reduced in severe sepsis patients with hyperlactataemia (lactate > 2 mmol/l), compared to SIRS patients (P 0.05), suggesting that there may be a link between 0.1 Hz ear blood flow oscillation and tissue metabolic changes in sepsis, in addition to autonomic factors. The study highlighted the value of PPG spectral analysis in the non-invasive assessment of peripheral vascular regulation in sepsis patients, with potential implications in monitoring the progression of sepsis

    Fermion Helicity Flip Induced by Torsion Field

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    We show that in theories of gravitation with torsion the helicity of fermion particles is not conserved and we calculate the probability of spin flip, which is related to the anti-symmetric part of affine connection. Some cosmological consequences are discussed.Comment: 6 pages, to appear in Europhysics Letter
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