220 research outputs found
Quasiperiodic oscillations in a strong gravitational field around neutron stars testing braneworld models
The strong gravitational field of neutron stars in the brany universe could
be described by spherically symmetric solutions with a metric in the exterior
to the brany stars being of the Reissner-Nordstrom type containing a brany
tidal charge representing the tidal effect of the bulk spacetime onto the star
structure. We investigate the role of the tidal charge in orbital models of
high-frequency quasiperiodic oscillations (QPOs) observed in neutron star
binary systems. We focus on the relativistic precession model. We give the
radial profiles of frequencies of the Keplerian (vertical) and radial epicyclic
oscillations. We show how the standard relativistic precession model modified
by the tidal charge fits the observational data, giving estimates of the
allowed values of the tidal charge and the brane tension based on the processes
going in the vicinity of neutron stars. We compare the strong field regime
restrictions with those given in the weak-field limit of solar system
experiments.Comment: 26 pages, 6 figure
Magnetized Particle Capture Cross Section for Braneworld Black Hole
Capture cross section of magnetized particle (with nonzero magnetic moment)
by braneworld black hole in uniform magnetic field is considered. The magnetic
moment of particle was chosen as it was done by \citet{rs99} and for the
simplicity particle with zero electric charge is chosen. It is shown that the
spin of particle as well as the brane parameter are to sustain the stability of
particles circularly orbiting around the black hole in braneworld i.e. spin of
particles and brane parameter try to prevent the capture by black hole.Comment: 7 pages, 4 figures, Accepted for publication in Astrophysics & Space
Scienc
Binary black hole shadows, chaotic scattering and the Cantor set
We investigate the qualitative features of binary black hole shadows using the model of two
extremally charged black holes in static equilibrium (a MajumdarâPapapetrou solution). Our
perspective is that binary spacetimes are natural exemplars of chaotic scattering, because they
admit more than one fundamental null orbit, and thus an uncountably infinite set of perpetual null
orbits which generate scattering singularities in initial data. Inspired by the three-disc model, we
develop an appropriate symbolic dynamics to describe planar null geodesics on the double black
hole spacetime. We show that a one-dimensional (1D) black hole shadow may constructed through
an iterative procedure akin to the construction of the Cantor set; thus the 1D shadow is self-similar.
Next, we study non-planar rays, to understand how angular momentum affects the existence and
properties of the fundamental null orbits. Taking slices through 2D shadows, we observe three
types of 1D shadow: regular, Cantor-like, and highly chaotic. The switch from Cantor-like to
regular occurs where outer fundamental orbits are forbidden by angular momentum. The highly
chaotic part is associated with an unexpected feature: stable and bounded null orbits, which exist
around two black holes of equal mass M separated by a1 < a < â
2a1, where a1 = 4M/â
27. To
show how this possibility arises, we define a certain potential function and classify its stationary
points. We conjecture that the highly chaotic parts of the 2D shadow possess the Wada property.
Finally, we consider the possibility of following null geodesics through event horizons, and chaos in
the maximally extended spacetime
Appearance of Keplerian discs orbiting Kerr superspinars
We study optical phenomena related to appearance of Keplerian accretion discs
orbiting Kerr superspinars predicted by the string theory. The superspinar
exterior is described by the standard Kerr naked singularity geometry breaking
the black hole limit on the internal angular momentum (spin). We construct
local photon escape cones for a variety of orbiting sources that enable to
determine the superspinars silhouette in the case of distant observers. We show
that the superspinar silhouette depends strongly on the assumed edge where the
external Kerr spacetime is joined to the internal spacetime governed by the
string theory and significantly differs from the black hole silhouette. The
appearance of the accretion disc is strongly dependent on the value of the
superspinar spin in both their shape and frequency shift profile. Apparent
extension of the disc grows significantly with growing spin, while the
frequency shift grows with descending spin. This behavior differs substantially
from appearance of discs orbiting black holes enabling thus, at least in
principle, to distinguish clearly the Kerr superspinars and black holes. In
vicinity of a Kerr superspinar the non-escaped photons have to be separated to
those captured by the superspinar and those being trapped in its strong
gravitational field leading to self-illumination of the disc that could even
influence its structure and causes self-reflection effect of radiation of the
disc. The amount of trapped photons grows with descending of the superspinar
spin. We thus can expect significant self-illumination effects in the field of
Kerr superspinars with near-extreme spin .Comment: accepted in Classical and Quantum Gravity (September 1st, 2010
The influences of patient's trust in medical service and attitude towards health policy on patient's overall satisfaction with medical service and sub satisfaction in China
<p>Abstract</p> <p>Background</p> <p>It is widely accepted that patient generates overall satisfaction with medical service and sub satisfaction on the basis of response to patient's trust in medical service and response to patient's attitude towards health policy in China. This study aimed to investigate the correlations between patient's trust in medical service/patient's attitude towards health policy and patient's overall satisfaction with medical service/sub satisfaction in current medical experience and find inspiration for future reform of China's health delivery system on improving patient's overall satisfaction with medical service and sub satisfaction in considering patient's trust in medical service and patient's attitude towards health policy.</p> <p>Methods</p> <p>This study collaborated with the National Bureau of Statistics to collect a sample of 3,424 residents from 17 provinces and municipalities in a 2008 China household survey on patient's trust in medical service, patient's attitude towards health policy, patient's overall satisfaction and sub satisfaction in current medical experience.</p> <p>Results</p> <p>Patient's overall satisfaction with medical service and most kinds of sub satisfaction in current medical experience were significantly influenced by both patient's trust in medical service and patient's attitude towards health policy; among all kinds of sub satisfaction in current medical experience, patient's trust in medical service/patient's attitude towards health policy had the largest influence on patient's satisfaction with medical costs, the influences of patient's trust in medical service/patient's attitude towards health policy on patient's satisfaction with doctor-patient interaction and satisfaction with treatment process were at medium-level, patient's trust in medical service/patient's attitude towards health policy had the smallest influence on patient's satisfaction with medical facilities and hospital environment, while patient's satisfaction with waiting time in hospital was not influenced by patient's trust in medical service/patient's attitude towards health policy.</p> <p>Conclusion</p> <p>In order to improve patient's overall satisfaction with medical service and sub satisfaction in considering patient's trust in medical service and patient's attitude towards health policy, both improving patient's interpersonal trust in medical service from individual's own medical experience/public trust in medical service and improving patient's attitude towards health policy were indirect but effective ways.</p
Summary of session A4 at the GRG18 conference: Alternative Theories of Gravity
More than 50 abstracts were submitted to the A4 session on "Alternatives
Theories of Gravity" at the GRG18 conference. About 30 of them were scheduled
as oral presentations, that we summarize below. We do not intend to give a
critical review, but rather pointers to the corresponding papers. The main
topics were (i) brane models both from the mathematical and the
phenomenological viewpoints; (ii) Einstein-Gauss-Bonnet gravity in higher
dimensions or coupled to a scalar field; (iii) modified Newtonian dynamics
(MOND); (iv) scalar-tensor and f(R) theories; (v) alternative models involving
Lorentz violations, noncommutative spacetimes or Chern-Simons corrections.Comment: 9 pages, no figure; the GRG18 conference was held in Sydney,
Australia, 8-13 July 200
Pharmacogenomic associations of adverse drug reactions in asthma: systematic review and research prioritisation
A systematic review of pharmacogenomic studies capturing adverse drug reactions (ADRs) related to asthma medications was undertaken, and a survey of Pharmacogenomics in Childhood Asthma (PiCA) consortia members was conducted. Studies were eligible if genetic polymorphisms were compared with suspected ADR(s) in a patient with asthma, as either a primary or secondary outcome. Five studies met the inclusion criteria. The ADRs and polymorphisms identified were change in lung function tests (rs1042713), adrenal suppression (rs591118), and decreased bone mineral density (rs6461639) and accretion (rs9896933, rs2074439). Two of these polymorphisms were replicated within the paper, but none had external replication. Priorities from PiCA consortia members (representing 15 institution in eight countries) for future studies were tachycardia (SABA/LABA), adrenal suppression/crisis and growth suppression (corticosteroids), sleep/behaviour disturbances (leukotriene receptor antagonists), and nausea and vomiting (theophylline). Future pharmacogenomic studies in asthma should collect relevant ADR data as well as markers of efficacy
ANALYSIS OF LIFE INSURANCE INVESTMENT COMPOSITION
Economic recession and global mettle down have brought the question of insurance
company investment to the forefront. Growing attention has shifted to the pattern of investments by the
insurance and question of how to evaluate such investments. The aim of this research is to evaluate
investment compositions which are made by life insurance companies in Indonesia, as well as to know the
effects on the performance of Insurance companies
The CD14 functional gene polymorphism -260 C>T is not involved in either the susceptibility to Chlamydia trachomatis infection or the development of tubal pathology
BACKGROUND: The functional polymorphism -260 C>T in the LPS sensing TLR4 co-receptor CD14 gene enhances the transcriptional activity and results in a higher CD14 receptor density. Individuals carrying the T/T genotype also have significantly higher serum levels of soluble CD14. The T allele of this polymorphism has recently been linked to Chlamydia pneumoniae infection. We investigated the role of the CD14 -260 C>T polymorphism in the susceptibility to and severity (defined as subfertility and/or tubal pathology) of C. trachomatis infection in Dutch Caucasian women. METHODS: The different CD14 -260 C>T genotypes were assessed by PCR-based RFLP analysis in three cohorts: 1) A cohort (n = 576) of women attending a STD clinic, 2) a cohort (n = 253) of women with subfertility, and 3) an ethnically matched control cohort (n = 170). The following variables were used in the analysis: In cohort 1 the CT-DNA status, CT IgG serology status, self-reported symptoms and in cohort 2, the CT IgG serology status and the tubal status at laparoscopy. RESULTS: In the control cohort the CC, CT and TT genotype distribution was: 28.2%, 48.2%, and 23.5% respectively. No differences were found in the overall prevalence of CD14 -260 genotypes (28.1%, 50.7%, and 21.2%) in cohort 1 when compared to the control cohort. Also no differences were observed in women with or without CT-DNA, with or without serological CT responses, with or without symptoms, or in combinations of these three variables. In subfertile women with tubal pathology (cohort 2, n = 50) the genotype distribution was 28.0%, 48.0%, and 24.0% and in subfertile women without tubal pathology (n = 203), 27.6%, 49.3% and 23.2%. The genotype distribution was unchanged when CT IgG status was introduced in the analyses. CONCLUSION: The CD14 -260 C>T genotype distributions were identical in all three cohorts, showing that this polymorphism is not involved in the susceptibility to or severity of sequelae of C. trachomatis infection
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