6,461 research outputs found

    Stable One-Dimensional Integral Representations of One-Loop N-Point Functions in the General Massive Case: I - Three Point Functions

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    In this article we provide representations for the one-loop three point functions in 4 and 6 dimensions in the general case with complex masses. The latter are part of the GOLEM library used for the computation of one-loop multileg amplitudes. These representations are one-dimensional integrals designed to be free of instabilites induced by inverse powers of Gram determinants, therefore suitable for stable numerical implementations.Comment: 40 pages, 1 figur

    Laid Off: American Workers and Employers Assess a Volatile Labor Market

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    This Work Trends survey shows that despite economic growth, worker concern for the economy, their job security, and the threat of terrorism is increasing; workers and employers express fear about outsourcing jobs abroad

    Local molecular field theory for the treatment of electrostatics

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    We examine in detail the theoretical underpinnings of previous successful applications of local molecular field (LMF) theory to charged systems. LMF theory generally accounts for the averaged effects of long-ranged components of the intermolecular interactions by using an effective or restructured external field. The derivation starts from the exact Yvon-Born-Green hierarchy and shows that the approximation can be very accurate when the interactions averaged over are slowly varying at characteristic nearest-neighbor distances. Application of LMF theory to Coulomb interactions alone allows for great simplifications of the governing equations. LMF theory then reduces to a single equation for a restructured electrostatic potential that satisfies Poisson's equation defined with a smoothed charge density. Because of this charge smoothing by a Gaussian of width sigma, this equation may be solved more simply than the detailed simulation geometry might suggest. Proper choice of the smoothing length sigma plays a major role in ensuring the accuracy of this approximation. We examine the results of a basic confinement of water between corrugated wall and justify the simple LMF equation used in a previous publication. We further generalize these results to confinements that include fixed charges in order to demonstrate the broader impact of charge smoothing by sigma. The slowly-varying part of the restructured electrostatic potential will be more symmetric than the local details of confinements.Comment: To be published in J Phys-Cond Matt; small misprint corrected in Eq. (12) in V

    History of Prairie Chickens in Iowa

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    The peak period for prairie chickens (Tympanuchus cupido pinnatus) in Iowa was about 1880 when 69% of the state was in farms. They were found in prairie areas throughout the state. Hunters found this grouse ideal game and bags of 25 to 50 per day were easily taken. Market hunters frequently killed 200 or more per day. Farmers trapped and shot the birds to sell or to eat. As long as marginal prairie areas were only lightly disturbed by agriculture, the prairie chickens held on, but when intensive farming began, the birds nested in hayfields or in over-grazed pastures where brooding was unsuccessful. By 1900, 90% of the state was in farms and birds were vanishing. A few remained until 1954 in a poorly drained portion of Appanoose County. Since then only occasional strays have been reported

    Time Variability in the X-ray Nebula Powered by Pulsar B1509-58

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    We use new and archival Chandra and ROSAT data to study the time variability of the X-ray emission from the pulsar wind nebula (PWN) powered by PSR B1509-58 on timescales of one week to twelve years. There is variability in the size, number, and brightness of compact knots appearing within 20" of the pulsar, with at least one knot showing a possible outflow velocity of ~0.6c (assuming a distance to the source of 5.2 kpc). The transient nature of these knots may indicate that they are produced by turbulence in the flows surrounding the pulsar. A previously identified prominent jet extending 12 pc to the southeast of the pulsar increased in brightness by 30% over 9 years; apparent outflow of material along this jet is observed with a velocity of ~0.5c. However, outflow alone cannot account for the changes in the jet on such short timescales. Magnetohydrodynamic sausage or kink instabilities are feasible explanations for the jet variability with timescale of ~1.3-2 years. An arc structure, located 30"-45" north of the pulsar, shows transverse structural variations and appears to have moved inward with a velocity of ~0.03c over three years. The overall structure and brightness of the diffuse PWN exterior to this arc and excluding the jet has remained the same over the twelve year span. The photon indices of the diffuse PWN and possibly the jet steepen with increasing radius, likely indicating synchrotron cooling at X-ray energies.Comment: accepted to ApJ, 14 pages, 8 figure

    Influence of Ageing, pH and Various Additives on Crystal Formation in Artificial Urine

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    In order to investigate the effect of various factors on urinary crystallization processes, a series of five experiments was carried out using an artificial urine (AU) in a rotary evaporator. The influence of ageing, pH and organic, inorganic and potential inhibitory additives formed the basis of the study. Precipitates were characterized by X-ray powder diffraction, scanning electron microscopy and energy dispersive X-ray analysis. In the ageing experiment, AU aliquots, adjusted to various pH values, were allowed to stand for several days and were not evaporated. Calcium oxalate monohydrate (COM) was formed at low pH, while whitlockite, apatite and struvite occurred at pH \u3e 7. In the second experiment, AU aliquots at various pH values, were evaporated. Similar results to those of series 1 were recorded but, in addition, calcium oxalate trihydrate (COT) precipitated in the pH range 3 to 6.5 and brushite at pH \u3e 5.5. In series 3, uric acid, creatinine and urea were included in AU aliquots (pH 5.5) which were subjected to evaporation. Uric acid promoted the formation of uric acid dihydrate; however, when present with creatinine, dihydrate formation was inhibited. Urea appeared to inhibit precipitation. In the fourth experiment, MgO, methylene blue and chondroitin sulphate A were independently included in the AU (pH 5.5). Precipitates of calcium oxalate mono-, di- and trihydrates were obtained. In the final experiment fluoride aliquots of variable concentrations were included in the AU (pH 5.5 and 6.5). COT crystals of superior quality to those observed in control solutions were obtained

    The parasitic worm-derived immunomodulator, ES-62 and its drug-like small molecule analogues exhibit therapeutic potential in a model of chronic asthma

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    Chronic asthma is associated with persistent lung inflammation and long-term remodelling of the airways that have proved refractory to conventional treatments such as steroids, despite their efficacy in controlling acute airway contraction and bronchial inflammation. As its recent dramatic increase in industrialised countries has not been mirrored in developing regions, it has been suggested that helminth infection may protect humans against developing asthma. Consistent with this, ES-62, an immunomodulator secreted by the parasitic worm Acanthocheilonema viteae, can prevent pathology associated with chronic asthma (cellular infiltration of the lungs, particularly neutrophils and mast cells, mucus hyper-production and airway thickening) in an experimental mouse model. Importantly, ES-62 can act even after airway remodelling has been established, arresting pathogenesis and ameliorating the inflammatory flares resulting from repeated exposure to allergen that are a debilitating feature of severe chronic asthma. Moreover, two chemical analogues of ES-62, 11a and 12b mimic its therapeutic actions in restoring levels of regulatory B cells and suppressing neutrophil and mast cell responses. These studies therefore provide a platform for developing ES-62-based drugs, with compounds 11a and 12b representing the first step in the development of a novel class of drugs to combat the hitherto intractable disorder of chronic asthma

    The resistance of randomly grown trees

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    Copyright @ 2011 IOP Publishing Ltd. This is a preprint version of the published article which can be accessed from the link below.An electrical network with the structure of a random tree is considered: starting from a root vertex, in one iteration each leaf (a vertex with zero or one adjacent edges) of the tree is extended by either a single edge with probability p or two edges with probability 1 − p. With each edge having a resistance equal to 1 omega, the total resistance Rn between the root vertex and a busbar connecting all the vertices at the nth level is considered. A dynamical system is presented which approximates Rn, it is shown that the mean value (Rn) for this system approaches (1 + p)/(1 − p) as n → ∞, the distribution of Rn at large n is also examined. Additionally, a random sequence construction akin to a random Fibonacci sequence is used to approximate Rn; this sequence is shown to be related to the Legendre polynomials and its mean is shown to converge with |(Rn) − (1 + p)/(1 − p)| ∼ n−1/2.Engineering and Physical Sciences Research Council (EPSRC
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