31 research outputs found

    Search for gravitational waves from Scorpius X-1 in the second Advanced LIGO observing run with an improved hidden Markov model

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    We present results from a semicoherent search for continuous gravitational waves from the low-mass x-ray binary Scorpius X-1, using a hidden Markov model (HMM) to track spin wandering. This search improves on previous HMM-based searches of LIGO data by using an improved frequency domain matched filter, the J-statistic, and by analyzing data from Advanced LIGO's second observing run. In the frequency range searched, from 60 to 650 Hz, we find no evidence of gravitational radiation. At 194.6 Hz, the most sensitive search frequency, we report an upper limit on gravitational wave strain (at 95% confidence) of h095%=3.47×10-25 when marginalizing over source inclination angle. This is the most sensitive search for Scorpius X-1, to date, that is specifically designed to be robust in the presence of spin wandering. © 2019 American Physical Society

    Search for Tensor, Vector, and Scalar Polarizations in the Stochastic Gravitational-Wave Background

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    The detection of gravitational waves with Advanced LIGO and Advanced Virgo has enabled novel tests of general relativity, including direct study of the polarization of gravitational waves. While general relativity allows for only two tensor gravitational-wave polarizations, general metric theories can additionally predict two vector and two scalar polarizations. The polarization of gravitational waves is encoded in the spectral shape of the stochastic gravitational-wave background, formed by the superposition of cosmological and individually unresolved astrophysical sources. Using data recorded by Advanced LIGO during its first observing run, we search for a stochastic background of generically polarized gravitational waves. We find no evidence for a background of any polarization, and place the first direct bounds on the contributions of vector and scalar polarizations to the stochastic background. Under log-uniform priors for the energy in each polarization, we limit the energy densities of tensor, vector, and scalar modes at 95% credibility to Ω0T<5.58×10-8, Ω0V<6.35×10-8, and Ω0S<1.08×10-7 at a reference frequency f0=25 Hz. © 2018 American Physical Society

    Lattice Strain in Magnetic Ultrathin Films

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    A clear understanding of the mechanisms of interfacial magnetic anisotropy rests on the structural characterisation of magnetic multilayers which, typically, consist of two ferromagnetically coupled (F) layers separated by a non-magnetic spacer layer. Fe/Cu/Fe trilayers are of special interest since the coupling between the F layers of Fe changes from F to antiferromagnetic depending on the thickness of the Cu spacer layer. Here, a magnetic multilayer system, grown by molecular beam epitaxy (MBE), was modified by inserting Cr in the Cu : Ag(001)/8.7 Fe/3 Cu/6 Cr/3 Cu/5 Fe/10 Au where the integers refer to monolayers. Polarized K-edge XAFS spectra (E parallel to the substrate) were obtained from fluorescence measurements in the total reflection geometry. The multiple scattering paths were analysed for the Cr edge. The initial Cu grew pseudomorphically in a BCC structure on Fe/Ag(001). The Cr proved to be tetragonally distorted from its BCC structure. The overlayers of Fe on Cu are contracted by 1.27% within the plane and conserve the c lattice parameter of Fe, though the atomic volume is contracted by 2.8%. The Cu adopts a BCT, rather than keeping its bulk FCC, structure and the corresponding decrease in its atomic volume from the FCC is only 0.3%

    Effective Coordination Numbers in Ultrathin Metallic Films

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    Nanostructures bave become a major field in material science. With molecular beam epitaxy it is possible to engineer multilayers with unusual anisotropic properties and metastable structures. For ultrathin films, or particles of small size, the coordination numbers are less than their bulk values. In fitting E X A F S data it is useful to be able to place limits on the coordination numbers or their ratios. W e have calculated the effective coordination numbers Ni , i= 1 to 5 for thin films with different crystal structures. The thickness o f the film is specified by the number o f layers Nz in the z-direction and the area in the x y plane by the number o f rows of atoms NXY along the side of a square domain. For fixed Nz, with the x-ray beam unpolarized or its electric vector parallel or perpendicular to the substrate (xy plane), the effective H approach hyperbolically the coordination number for a layer o f infinite area. Simple analytical expressions are fitted to the numerical results fix- bcc and fee crystals from which the H can be calculated for both NXY and Nz ≥ 2. Comparison is made with the effective coordination numbers obtained from polarized E X A F S measurements on epitaxial metallic films less than 10 monolayers thick

    Efeito do estresse térmico e do exercício sobre parâmetros fisiológicos de cavalos do exército brasileiro Effect of heat stress and exercise on physiological parameters of horses of the Brazilian army

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    Os cavalos do exército brasileiro são usados em dias de exposição e, muitas vezes, submetidos a exercício intenso, que, aliado às condições climáticas do cerrado do Centro-Oeste brasileiro, resulta na necessidade de extrema aclimatação dos mesmos. O objetivo desse estudo foi determinar o efeito do estresse térmico e do exercício a que estão submetidas às raças de eqüinos estudadas. Foram utilizados 40 cavalos adultos (4 a 13 anos) do 1º Regimento de Cavalaria de Guarda (10 animais de cada uma das raças Puro Sangue de Corrida - PSC, Mestiço <FONT FACE=Symbol>&frac34;</FONT> M e Brasileiro de Hipismo - BH) e do 32º Grupo de Artilharia de Campanha (10 animais da raça Bretã), localizado no Setor Militar Urbano do Distrito Federal. Foram realizadas três medidas das freqüências cardíaca e respiratória, da temperatura retal e colhidas amostras de sangue quatro vezes por dia, de manhã e à tarde, antes e depois dos animais terem sido submetidos a exercício. A raça afetou todas as características exceto VCM, HCM e CHCM. Animais da raça PSC tiveram médias mais altas para leucócitos (7,83 &plusmn; 1,59), hemácias (9,21 &plusmn; 1,27), VG (40,75 &plusmn; 4,58) e hemoglobina (14,34 &plusmn; 1,67), enquanto os mestiços tiveram médias mais altas para proteína plasmática total (6,93 &plusmn; 0,66). Na raça Bretã foram observados níveis mais baixos para a maioria das características examinadas. O exercício afetou todas as características exceto VCM, HCM e CHCM com o nível das características aumentando em todos os casos. As correlações entre as características investigadas variam muito, sendo que entre hemácias, hemoglobina, VG foram em geral altas e positivas (>0,58), enquanto com a proteína plasmática total foram de médias a baixas (<0,26). O presente experimento nos permite concluir que os animais da raça PSC são os mais susceptíveis e os da raça Bretã os melhores adaptados às condições do clima do DF.<br>The horses of the Brazilian army are used for expositions, and frequently subjected to intense exercise. This, together with environmental conditions of the Central west savanna result in the need for acclimatization. The objective of this study was to determine what is the effect of thermal and exercise stress on four groups of stabled horses in the savanna region. 40 Adult horses (4 to 13 years of age) from the 1st Mounted Guard Regiment (10 of each breed Thoroughbred <FONT FACE=Symbol>&frac34;</FONT> PSC, Crossbred <FONT FACE=Symbol>&frac34;</FONT> M and Brazilian Showjumper <FONT FACE=Symbol>&frac34;</FONT> BH) as well as 10 Bretãs from the 32nd Campaign Artillery Group, were used. All horses were kept in the Urban Military Sector in the Federal District. The measurements made on the animals included heart and respiratory rates, rectal temperature and blood samples were taken at four opportunities during the day, in the morning and afternoon, before and after exercise. Genetic group influenced all traits except VCM, HCM e CHCM. Animals of the PSC group had higher means for leukocytes (7.83 &plusmn; 1.59), hematocytes (9.21 &plusmn; 1.27), VG (40.75 &plusmn; 4.58) and hemoglobin (14.34 &plusmn; 1.67), while crossbreds had higher total plasmatic protein levels (6,93 &plusmn; 0,66). The Breton breed had lowest levels for the majority traits examined. Exercise increased all traits except VCM, HCM and CHCM. The correlations between traits vary greatly, the highest being between hematocytes, hemoglobin and VG (>0.58), while with total plasma protein they were low (<0.26). The present work allows us to conclude that in terms of exercise of horses of the Brazilian army PSC are worst adapted and Bretã best adapted to the conditions of this study

    Genome-wide study identifies association between HLA-B∗55:01 and Self-Reported Penicillin Allergy

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    Hypersensitivity reactions to drugs are often unpredictable and can be life threatening, underscoring a need for understanding their underlying mechanisms and risk factors. The extent to which germline genetic variation influences the risk of commonly reported drug allergies such as penicillin allergy remains largely unknown. We extracted data from the electronic health records of more than 600,000 participants from the UK, Estonian, and Vanderbilt University Medical Center’s BioVU biobanks to study the role of genetic variation in the occurrence of self-reported penicillin hypersensitivity reactions. We used imputed SNP to HLA typing data from these cohorts to further fine map the human leukocyte antigen (HLA) association and replicated our results in 23andMe’s research cohort involving a total of 1.12 million individuals. Genome-wide meta-analysis of penicillin allergy revealed two loci, including one located in the HLA region on chromosome 6. This signal was further fine-mapped to the HLA-B∗55:01 allele (OR 1.41 95% CI 1.33–1.49, p value 2.04 × 10−31) and confirmed by independent replication in 23andMe’s research cohort (OR 1.30 95% CI 1.25–1.34, p value 1.00 × 10−47). The lead SNP was also associated with lower lymphocyte counts and in silico follow-up suggests a potential effect on T-lymphocytes at HLA-B∗55:01. We also observed a significant hit in PTPN22 and the GWAS results correlated with the genetics of rheumatoid arthritis and psoriasis. We present robust evidence for the role of an allele of the major histocompatibility complex (MHC) I gene HLA-B in the occurrence of penicillin allergy
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