6,358 research outputs found

    Closed-form sums for some perturbation series involving associated Laguerre polynomials

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    Infinite series sum_{n=1}^infty {(alpha/2)_n / (n n!)}_1F_1(-n, gamma, x^2), where_1F_1(-n, gamma, x^2)={n!_(gamma)_n}L_n^(gamma-1)(x^2), appear in the first-order perturbation correction for the wavefunction of the generalized spiked harmonic oscillator Hamiltonian H = -d^2/dx^2 + B x^2 + A/x^2 + lambda/x^alpha 0 0, A >= 0. It is proved that the series is convergent for all x > 0 and 2 gamma > alpha, where gamma = 1 + (1/2)sqrt(1+4A). Closed-form sums are presented for these series for the cases alpha = 2, 4, and 6. A general formula for finding the sum for alpha/2 = 2 + m, m = 0,1,2, ..., in terms of associated Laguerre polynomials, is also provided.Comment: 16 page

    A Luminous Be+White Dwarf Supersoft Source in the Wing of the SMC: MAXI J0158-744

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    We present a multi-wavelength analysis of the very fast X-ray transient MAXI J0158-744, which was detected by MAXI/GSC on 2011 November 11. The subsequent exponential decline of the X-ray flux was followed with Swift observations, all of which revealed spectra with low temperatures (~100eV) indicating that MAXI J0158-744 is a new Supersoft Source (SSS). The Swift X-ray spectra near maximum show features around 0.8 keV that we interpret as possible absorption from OVIII, and emission from O, Fe, and Ne lines. We obtained SAAO and ESO optical spectra of the counterpart early in the outburst and several weeks later. The early spectrum is dominated by strong Balmer and HeI emission, together with weaker HeII emission. The later spectrum reveals absorption features that indicate a B1/2IIIe spectral type, and all spectral features are at velocities consistent with the Small Magellanic Cloud. At this distance, it is a luminous SSS (>10^37 erg/s) but whose brief peak luminosity of >10^39 erg/s in the 2-4 keV band makes it the brightest SSS yet seen at "hard" X-rays. We propose that MAXI J0158-744 is a Be-WD binary, and the first example to possibly enter ULX territory. The brief hard X-ray flash could possibly be a result of the interaction of the ejected nova shell with the B star wind in which the white dwarf (WD) is embedded. This makes MAXI J0158-744 only the third Be/WD system in the Magellanic Clouds, but it is by far the most luminous. The properties of MAXI J0158-744 give weight to previous suggestions that SSS in nearby galaxies are associated with early-type stellar systems.Comment: 15 pages, 8 figures; ApJ accepte

    Well-being over time in Britain and the USA

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    This paper studies happiness in the United States and Great Britain. Reported levels of well-being have declined over the last quarter of a century in the US; life satisfaction has run approximately flat through time in Britain. These findings are consistent with the Easterlin hypothesis [Nations and Households in Economic Growth: Essays in Honour of Moses Abramowitz (1974) Academic Press; J. Econ. Behav. Org., 27 (1995) 35]. The happiness of American blacks, however, has risen. White women in the US have been the biggest losers since the 1970s. Well-being equations have a stable structure. Money buys happiness. People care also about relative income. Well-being is U-shaped in age. The paper estimates the dollar values of events like unemployment and divorce. They are large. A lasting marriage (compared to widowhood as a ‘natural’ experiment), for example, is estimated to be worth $100,000 a year

    Cloning and expression of activation induced cytidine deaminase from Bos taurus'

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    Activation induced cytidine deaminase is an enzyme crucial to somatic hypermutation and gene conversion, processes that are essential for the diversification of Ig V genes. The bovine Ig repertoire appears to be diversified by mechanisms that are significantly different to those that operate in humans and mice. This study set out to test the hypothesis that differences in the organization, coding sequence, expression or genomic location of the bovine AICDA gene enables the encoded enzyme to catalyse the unusual Ig diversification mechanism seen in cattle as well as conventional antigen-driven mutation. Characterization of bovine AICDA excluded the first two possibilities. AICDA expression was detected in lymphoid tissues from neonatal and older cattle, but AICDA cDNA could not be detected in muscle tissue. The pattern of gene expression did not therefore differ from that in other vertebrates. The AICDA cDNA was cloned and expressed successfully in Escherichia coli generating a phenotype consistent with the mutating action of this deaminase. Using a whole genome radiation hybrid panel, bovine AICDA was mapped to a region of bovine chromosome 5 syntenic with the location of human AICDA on chromosome 12. We conclude that the unusual nature of Ig diversification in cattle is unlikely to be attributable to the structure, sequence, activity or genomic location of bovine AICDA

    Money, sex and happiness : an empirical study

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    The links between income, sexual behavior and reported happiness are studied using recent data on a sample of 16,000 adult Americans. The paper finds that sexual activity enters strongly positively in happiness equations. Higher income does not buy more sex or more sexual partners. Married people have more sex than those who are single, divorced, widowed or separated. The happiness‐maximizing number of sexual partners in the previous year is calculated to be 1. Highly educated females tend to have fewer sexual partners. Homosexuality has no statistically significant effect on happiness

    Palaeolithic extinctions and the Taurid Complex

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    Intersection with the debris of a large (50-100 km) short-period comet during the Upper Palaeolithic provides a satisfactory explanation for the catastrophe of celestial origin which has been postulated to have occurred around 12900 BP, and which presaged a return to ice age conditions of duration ~1300 years. The Taurid Complex appears to be the debris of this erstwhile comet; it includes at least 19 of the brightest near-Earth objects. Sub-kilometre bodies in meteor streams may present the greatest regional impact hazard on timescales of human concern.Comment: 7 pages, 3 figures; accepted for Monthly Notices of the Royal Astronomical Society (definitive version will be available at www.blackwell-synergy.com

    Effects of dietary salt on gene and protein expression in brain tissue of a model of sporadic small vessel disease

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    Background: The effect of salt on cerebral small vessel disease (SVD) is poorly understood. We assessed the effect of dietary salt on the cerebral tissue of the strokeprone spontaneously hypertensive rat (SHRSP) - a relevant model of sporadic SVD - at both the gene and protein level. Methods: Brains from 21 week old SHRSP and Wistar-Kyoto rats, half additionally salt-loaded (via a 3 week regime of 1% NaCl in drinking water) were split into 2 hemispheres and sectioned coronally – one hemisphere for mRNA microarray and qRT-PCR, the other for immunohistochemistry using a panel of antibodies targeting components of the neurovascular unit. Results: We observed differences in gene and protein expression affecting the acute phase pathway and oxidative stress (ALB, AMBP, APOH, AHSG and LOC100129193, up-regulated in salt-loaded WKY versus WKY, >2-fold), active microglia (increased Iba-1 protein expression in salt-loaded SHRSP versus saltloaded WKY, p<0.05), vascular structure (ACTB & CTNNB, up-regulated in saltloaded SHRSP versus SHRSP, >3-fold; CLDN-11,VEGF and VGF downregulated >- 2-fold in salt-loaded SHRSP versus SHRSP) and myelin integrity (MBP downregulated in salt loaded WKY rats versus WKY, >2.5-fold). Changes of salt-loading were more pronounced in SHRSP and occurred without an increase in blood pressure in WKY rats. Conclusion: Salt exposure induced changes in gene and protein expression in an experimental model of SVD and its parent rat strain in multiple pathways involving components of the glio-vascular unit. Further studies in pertinent experimental models at different ages would help clarify the short and long-term effect of dietary salt in SVD

    Thermal Infrared Imaging from Drones Offers a Major Advance for Spider Monkey Surveys

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    Accurate and precise population estimates form the basis of conservation action but are lacking for many arboreal species due to the high costs and difficulty in surveying these species. Recently, researchers have started to use drones to obtain data on animal distribution and density. In this study, we compared ground and drone counts for spider monkeys (Ateles geoffroyi) at their sleeping sites using a custom-built drone fitted with a thermal infrared (TIR) camera. We demonstrated that a drone with a TIR camera can be successfully employed to determine the presence and count the number of spider monkeys in a forested area. Using a concordance analysis, we found high agreement between ground and drone counts for small monkey subgroups (10 individuals), with drone counts being higher than the corresponding ground counts in 83% of surveys. We could identify additional individuals from TIR drone footage due to a greater area covered compared to ground surveys. We recommend using TIR drones for surveys of spider monkey sleeping sites and discuss current challenges to implementation

    A complete X-ray spectral coverage of the 2010 May-June outbursts of Circinus X-1

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    Circinus X-1 is a neutron-star-accreting X-ray binary in a wide (Porb_{\rm orb} = 16.6 d), eccentric orbit. After two years of relatively low X-ray luminosity, in May 2010 Circinus X-1 went into outburst, reaching 0.4 Crab flux. This outburst lasted for about two orbital cycles and was followed by another shorter and fainter outburst in June. We focus here on the broadband X-ray spectral evolution of the source as it spans about three order of magnitudes in flux. We attempt to relate luminosity, spectral shape, local absorption, and orbital phase. We use multiple Rossi-XTE/PCA (3.0--25 keV) and Swift/XRT (1.0--9.0 keV) observations and a 20 ks long Chandra/HETGS observation (1.0--9.0 keV), to comprehensively track the spectral evolution of the source during all the outbursting phases. These observations were taken every two/three days and cover about four orbital cycles. The PCA data mostly cover the major outburst, the XRT data monitor the declining phase of the major outburst and all the phases of the minor outburst, and Chandra data provide an essential snapshot of the end of this overall outbursting phase. The X-ray spectrum can be satisfactorily described by a thermal Comptonization model with variable neutral local absorption in all phases of the outburst. No other additive component is statistically required. The first outburst decays linearly, with an ankle in the light curve as the flux decreases below ∌\sim\,5 ×\times 10−10^{-10} erg cm−2^{-2} s−1^{-1}. At the same time, the source shows a clear spectral state transition from an optically thick to an optically thin state. While the characteristics of the first, bright, outburst can be interpreted within the disk-instability scenario, the following, minor, outburst shows peculiarities that cannot be easily reconciled in this framework.Comment: Accepted for publication in Astronomy and Astrophysic
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