374 research outputs found
Meissner state in finite superconducting cylinders with uniform applied magnetic field
We study the magnetic response of superconductors in the presence of low
values of a uniform applied magnetic field. We report measurements of DC
magnetization and AC magnetic susceptibility performed on niobium cylinders of
different length-to-radius ratios, which show a dramatic enhance of the initial
magnetization for thin samples, due to the demagnetizing effects. The
experimental results are analyzed by applying a model that calculates the
magnetic response of the superconductor, taking into account the effects of the
demagnetizing fields. We use the results of magnetization and current and field
distributions of perfectly diamagnetic cylinders to discuss the physics of the
demagnetizing effects in the Meissner state of type-II superconductors.Comment: Accepted to be published in Phys. Rev. B; 15 pages, 7 ps figure
A model of CP Violation from Extra Dimension
We construct a realistic model of CP violation in which CP is broken in the
process of dimensional reduction and orbifold compactification from a five
dimensional theories with gauge symmetry. CP
violation is a result of the Hosotani type gauge configuration in the higher
dimension.Comment: 5 page
Postcopulatory sexual selection
The female reproductive tract is where competition between the sperm of different males takes place, aided and abetted by the female herself. Intense postcopulatory sexual selection fosters inter-sexual conflict and drives rapid evolutionary change to generate a startling diversity of morphological, behavioural and physiological adaptations. We identify three main issues that should be resolved to advance our understanding of postcopulatory sexual selection. We need to determine the genetic basis of different male fertility traits and female traits that mediate sperm selection; identify the genes or genomic regions that control these traits; and establish the coevolutionary trajectory of sexes
Prior HIV Testing Among STD Patients in Guangdong Province, China: Opportunities for Expanding Detection of Sexually Transmitted HIV Infection
Expanding HIV testing is important among individuals at increased risk for sexual HIV transmission in China, but little is known about prior HIV testing experiences among sexually transmitted disease (STD) patients
Genome-wide linkage of plasma adiponectin reveals a major locus on chromosome 3q distinct from the adiponectin structural gene - The IRAS family study
Adiponectin (APM1) is an adipocyte-derived peptide that contributes to glucose, lipid, and energy homeostasis. We assessed the genetic basis of plasma adiponectin in Hispanic-American and African-American families enrolled through the Insulin Resistance Atherosclerosis Study Family Study. A 10-cM genome scan was performed in two batches: an original set (set 1) consisting of 66 families (45 Hispanic American and 21 African American) and a replication set (set 2) consisting of 66 families (45 Hispanic American and 21 African American). Adiponectin levels were measured by radioimmunoassay in 1,727 individuals from 131 of 132 families. Linkage analysis was carried out in Hispanic Americans and African Americans separately in set 1, set 2, and the pooled set (set I plus set 2), with and without diabetic subjects. A major gene was mapped to 3q27 with a logarithm of odds (LOD) score of 8.21 in the Hispanic-American sample. Ninety-six unrelated individuals were screened for polymorphisms in the APMI gene, and 18 single nucleotide polyporphisms (SNPs) were genotyped in the Hispanic-American sample. Plasma adiponeetin level was modestly associated with two SNPs and their accompaning haplotypes. Incorporating each or both SNPs in the linkage analysis, however, did not significantly re- duce the LOD score. Therefore, a quantitative trait locus at 3q27, likely distinct from the APM1 gene, contributes to the variation of plasma adiponectin levels in the Hispanic-American population
Gravitational Lensing by Black Holes
We review the theoretical aspects of gravitational lensing by black holes,
and discuss the perspectives for realistic observations. We will first treat
lensing by spherically symmetric black holes, in which the formation of
infinite sequences of higher order images emerges in the clearest way. We will
then consider the effects of the spin of the black hole, with the formation of
giant higher order caustics and multiple images. Finally, we will consider the
perspectives for observations of black hole lensing, from the detection of
secondary images of stellar sources and spots on the accretion disk to the
interpretation of iron K-lines and direct imaging of the shadow of the black
hole.Comment: Invited article for the GRG special issue on lensing (P. Jetzer, Y.
Mellier and V. Perlick Eds.). 31 pages, 12 figure
Strong Gravitational Lensing of Quasi-Kerr Compact Object with Arbitrary Quadrupole Moments
We study the strong gravitational lensing on the equatorial plane of a
quasi-Kerr compact object with arbitrary quadrupole moments which can be used
to model the super-massive central object of the galaxy. We find that, when the
quadrupolar correction parameter takes the positive (negative) value, the
photon-sphere radius , the minimum impact parameter , the
coefficient , the relative magnitudes and the angular position
of the relativistic images are larger (smaller) than the
results obtained in the Kerr black hole, but the coefficient , the
deflection angle and the angular separation are smaller
(larger) than that in the Kerr black hole. These features may offer a way to
probe special properties for some rotating compact objects by the astronomical
instruments in the future.Comment: 17 pages, 4 figures. Accepted for publication in JHE
Testing for Associations between Loci and Environmental Gradients Using Latent Factor Mixed Models
Adaptation to local environments often occurs through natural selection
acting on a large number of loci, each having a weak phenotypic effect. One way
to detect these loci is to identify genetic polymorphisms that exhibit high
correlation with environmental variables used as proxies for ecological
pressures. Here, we propose new algorithms based on population genetics,
ecological modeling, and statistical learning techniques to screen genomes for
signatures of local adaptation. Implemented in the computer program "latent
factor mixed model" (LFMM), these algorithms employ an approach in which
population structure is introduced using unobserved variables. These fast and
computationally efficient algorithms detect correlations between environmental
and genetic variation while simultaneously inferring background levels of
population structure. Comparing these new algorithms with related methods
provides evidence that LFMM can efficiently estimate random effects due to
population history and isolation-by-distance patterns when computing
gene-environment correlations, and decrease the number of false-positive
associations in genome scans. We then apply these models to plant and human
genetic data, identifying several genes with functions related to development
that exhibit strong correlations with climatic gradients.Comment: 29 pages with 8 pages of Supplementary Material (V2 revised
presentation and results part
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