584 research outputs found
Eliminating ambiguities for quantum corrections to strings moving in
We apply a physical principle, previously used to eliminate ambiguities in
quantum corrections to the 2 dimensional kink, to the case of spinning strings
moving in , thought of as another kind of two
dimensional soliton. We find that this eliminates the ambiguities and selects
the result compatible with AdS/CFT, providing a solid foundation for one of the
previous calculations, which found agreement. The method can be applied to
other classical string "solitons".Comment: 18 pages, latex; references added, comments added at end of section
4, a few words changed; footnote added on page 1
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Population History and Gene Divergence in Native Mexicans Inferred from 76 Human Exomes.
Native American genetic variation remains underrepresented in most catalogs of human genome sequencing data. Previous genotyping efforts have revealed that Mexico's Indigenous population is highly differentiated and substructured, thus potentially harboring higher proportions of private genetic variants of functional and biomedical relevance. Here we have targeted the coding fraction of the genome and characterized its full site frequency spectrum by sequencing 76 exomes from five Indigenous populations across Mexico. Using diffusion approximations, we modeled the demographic history of Indigenous populations from Mexico with northern and southern ethnic groups splitting 7.2 KYA and subsequently diverging locally 6.5 and 5.7 KYA, respectively. Selection scans for positive selection revealed BCL2L13 and KBTBD8 genes as potential candidates for adaptive evolution in RarĂĄmuris and Triquis, respectively. BCL2L13 is highly expressed in skeletal muscle and could be related to physical endurance, a well-known phenotype of the northern Mexico RarĂĄmuri. The KBTBD8 gene has been associated with idiopathic short stature and we found it to be highly differentiated in Triqui, a southern Indigenous group from Oaxaca whose height is extremely low compared to other Native populations
On the unimpairable resistance of the guinea pig to dietary amino azo dye hepatocarcinogenesis
Die Resistenz des Meerschweinchens gegenĂŒber der hepatocarcinogenen Wirkung von 3âČ-Methyl-4-dimethylaminoazobenzene, das mit 0,12% insgesamt 8 Monate gefĂŒttert wurde, wird auch durch den starken co-carcinogenen EinfluĂ einer Partialhepatektomie nicht gebrochen. The resistance of the guinea pig to carcinogenesis by 3âČ-methyl-4-dimethylaminoazobenzene fed at the level of 0.12% for a total of 8 months is not overcome by the potent cocarcinogenic influence of partial hepatectomy performed at 4 weeks.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47536/1/432_2004_Article_BF00524400.pd
Torsion and the Gravitational Interaction
By using a nonholonomous-frame formulation of the general covariance
principle, seen as an active version of the strong equivalence principle, an
analysis of the gravitational coupling prescription in the presence of
curvature and torsion is made. The coupling prescription implied by this
principle is found to be always equivalent with that of general relativity, a
result that reinforces the completeness of this theory, as well as the
teleparallel point of view according to which torsion does not represent
additional degrees of freedom for gravity, but simply an alternative way of
representing the gravitational field.Comment: Version 2: minor presentation changes, a reference added, 11 pages
(IOP style
Matrix theory of gravitation
A new classical theory of gravitation within the framework of general
relativity is presented. It is based on a matrix formulation of
four-dimensional Riemann-spaces and uses no artificial fields or adjustable
parameters. The geometrical stress-energy tensor is derived from a matrix-trace
Lagrangian, which is not equivalent to the curvature scalar R. To enable a
direct comparison with the Einstein-theory a tetrad formalism is utilized,
which shows similarities to teleparallel gravitation theories, but uses complex
tetrads. Matrix theory might solve a 27-year-old, fundamental problem of those
theories (sec. 4.1). For the standard test cases (PPN scheme,
Schwarzschild-solution) no differences to the Einstein-theory are found.
However, the matrix theory exhibits novel, interesting vacuum solutions.Comment: 24 page
Population Empirical Likelihood Estimation in Dual Frame Surveys
Dual frame surveys are a device to reduce the costs derived from data
collection in surveys and improve coverage for the whole target population. Since
their introduction, in the 1960âs, dual frame surveys have gained much attention
and several estimators have been formulated based on a number of different approaches. In this work, we propose new dual frame estimators based on the population empirical likelihood method originally proposed by Chen and Kim (2014) and
using both the dual and the single frame approach. The extension of the proposed
methodology to more than two frame surveys is also sketched. The performance
of the proposed estimators in terms of relative bias and relative mean squared
error is tested through simulation experiments. These experiments indicate that
the proposed estimators yield better results than other likelihood-based estimators
proposed in the literature.Ministerio de EconomĂa y Competitividad of Spai
A cooperative interaction between LPHN3 and 11q doubles the risk for ADHD
In previous studies of a genetic isolate, we identified significant linkage of attention deficit hyperactivity disorder (ADHD) to 4q, 5q, 8q, 11q and 17p. The existence of unique large size families linked to multiple regions, and the fact that these families came from an isolated population, we hypothesized that two-locus interaction contributions to ADHD were plausible. Several analytical models converged to show significant interaction between 4q and 11q (P<1 Ă 10â8) and 11q and 17p (P<1 Ă 10â6). As we have identified that common variants of the LPHN3 gene were responsible for the 4q linkage signal, we focused on 4qâ11q interaction to determine that single-nucleotide polymorphisms (SNPs) harbored in the LPHN3 gene interact with SNPs spanning the 11q region that contains DRD2 and NCAM1 genes, to double the risk of developing ADHD. This interaction not only explains genetic effects much better than taking each of these loci effects by separated but also differences in brain metabolism as depicted by proton magnetic resonance spectroscopy data and pharmacogenetic response to stimulant medication. These findings not only add information about how high order genetic interactions might be implicated in conferring susceptibility to develop ADHD but also show that future studies of the effects of genetic interactions on ADHD clinical information will help to shape predictive models of individual outcome
Torsion Gravity: a Reappraisal
The role played by torsion in gravitation is critically reviewed. After a
description of the problems and controversies involving the physics of torsion,
a comprehensive presentation of the teleparallel equivalent of general
relativity is made. According to this theory, curvature and torsion are
alternative ways of describing the gravitational field, and consequently
related to the same degrees of freedom of gravity. However, more general
gravity theories, like for example Einstein-Cartan and gauge theories for the
Poincare and the affine groups, consider curvature and torsion as representing
independent degrees of freedom. By using an active version of the strong
equivalence principle, a possible solution to this conceptual question is
reviewed. This solution favors ultimately the teleparallel point of view, and
consequently the completeness of general relativity. A discussion of the
consequences for gravitation is presented.Comment: RevTeX, 34 pages. Review article to be published by Int. J. Mod.
Phys.
Reducing recurrent stroke: methodology of the motivational interviewing in stroke (MIST) randomized clinical trial
Recurrent stroke is prevalent in both developed and developing countries, contributing significantly to disability and death. Recurrent stroke rates can be reduced by adequate risk factor management. However, adherence to prescribed medications and lifestyle changes recommended by physicians at discharge after stroke is poor, leading to a large number of preventable recurrent strokes. Using behavior change methods such as Motivational Interviewing early after stroke occurrence has the potential to prevent recurrent stroke
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