168 research outputs found
Recommended from our members
Model independent expansion history from supernovae: Cosmology versus systematics
We examine the Pantheon supernovae distance data compilation in a model independent analysis to test the validity of cosmic history reconstructions beyond the concordance CDM cosmology. Strong deviations are allowed by the data at z 1 in the reconstructed Hubble parameter, Om diagnostic, and dark energy equation of state. We explore three interpretations: 1) possibility of the true cosmology being far from CDM, 2) supernovae property evolution, and 3) survey selection effects. The strong (and theoretically problematic) deviations at z 1 vanish and good consistency with CDM is found with a simple Malmquist-like linear correction. The adjusted data is robust against the model independent iterative smoothing reconstruction. However, we caution that while by eye the original deviation from CDM is striking, Ď2 tests do not show the extra linear correction parameter is statistically significant, and a model-independent Gaussian Process regression does not find significant evidence for the need for correction at high-redshifts
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
Looking Beyond Lambda with the Union Supernova Compilation
The recent robust and homogeneous analysis of the world's supernova
distance-redshift data, together with cosmic microwave background and baryon
acoustic oscillation data, provides a powerful tool for constraining
cosmological models. Here we examine particular classes of scalar field,
modified gravity, and phenomenological models to assess whether they are
consistent with observations even when their behavior deviates from the
cosmological constant Lambda. Some models have tension with the data, while
others survive only by approaching the cosmological constant, and a couple are
statistically favored over LCDM. Dark energy described by two equation of state
parameters has considerable phase space to avoid Lambda and next generation
data will be required to constrain such physics.Comment: 32 pages, 19 figure
Fluids in cosmology
We review the role of fluids in cosmology by first introducing them in
General Relativity and then by applying them to a FRW Universe's model. We
describe how relativistic and non-relativistic components evolve in the
background dynamics. We also introduce scalar fields to show that they are able
to yield an inflationary dynamics at very early times (inflation) and late
times (quintessence). Then, we proceed to study the thermodynamical properties
of the fluids and, lastly, its perturbed kinematics. We make emphasis in the
constrictions of parameters by recent cosmological probes.Comment: 34 pages, 4 figures, version accepted as invited review to the book
"Computational and Experimental Fluid Mechanics with Applications to Physics,
Engineering and the Environment". Version 2: typos corrected and references
expande
Cosmology with Gravitational Lensing
In these lectures I give an overview of gravitational lensing, concentrating
on theoretical aspects, including derivations of some of the important results.
Topics covered include the determination of surface mass densities of
intervening lenses, as well as the statistical analysis of distortions of
galaxy images by general inhomogeneities (cosmic shear), both in 2D projection
on the sky, and in 3D where source distance information is available. 3D mass
reconstruction and the shear ratio test are also considered, and the
sensitivity of observables to Dark Energy is used to show how its equation of
state may be determined using weak lensing. Finally, the article considers the
prospect of testing Einstein's General Relativity with weak lensing, exploiting
the differences in growth rates of perturbations in different models.}
\abstract{In these lectures I give an overview of gravitational lensing,
concentrating on theoretical aspects, including derivations of some of the
important results. Topics covered include the determination of surface mass
densities of intervening lenses, as well as the statistical analysis of
distortions of galaxy images by general inhomogeneities (cosmic shear), both in
2D projection on the sky, and in 3D where source distance information is
available. 3D mass reconstruction and the shear ratio test are also considered,
and the sensitivity of observables to Dark Energy is used to show how its
equation of state may be determined using weak lensing. Finally, the article
considers the prospect of testing Einstein's General Relativity with weak
lensing, exploiting the differences in growth rates of perturbations in
different models.Comment: Lectures given at Como Summer School 2007, now published (in 'Dark
Matter and Dark Energy', 2011, ASSL 370, eds. Matarrese, Colpi, Gorini,
Moschella
A Co-Opted DEAD-Box RNA Helicase Enhances Tombusvirus Plus-Strand Synthesis
Replication of plus-strand RNA viruses depends on recruited host factors that aid several critical steps during replication. In this paper, we show that an essential translation factor, Ded1p DEAD-box RNA helicase of yeast, directly affects replication of Tomato bushy stunt virus (TBSV). To separate the role of Ded1p in viral protein translation from its putative replication function, we utilized a cell-free TBSV replication assay and recombinant Ded1p. The in vitro data show that Ded1p plays a role in enhancing plus-strand synthesis by the viral replicase. We also find that Ded1p is a component of the tombusvirus replicase complex and Ded1p binds to the 3â˛-end of the viral minus-stranded RNA. The data obtained with wt and ATPase deficient Ded1p mutants support the model that Ded1p unwinds local structures at the 3â˛-end of the TBSV (â)RNA, rendering the RNA compatible for initiation of (+)-strand synthesis. Interestingly, we find that Ded1p and glyceraldehyde-3-phosphate dehydrogenase (GAPDH), which is another host factor for TBSV, play non-overlapping functions to enhance (+)-strand synthesis. Altogether, the two host factors enhance TBSV replication synergistically by interacting with the viral (â)RNA and the replication proteins. In addition, we have developed an in vitro assay for Flock house virus (FHV), a small RNA virus of insects, that also demonstrated positive effect on FHV replicase activity by the added Ded1p helicase. Thus, two small RNA viruses, which do not code for their own helicases, seems to recruit a host RNA helicase to aid their replication in infected cells
f(R) theories
Over the past decade, f(R) theories have been extensively studied as one of
the simplest modifications to General Relativity. In this article we review
various applications of f(R) theories to cosmology and gravity - such as
inflation, dark energy, local gravity constraints, cosmological perturbations,
and spherically symmetric solutions in weak and strong gravitational
backgrounds. We present a number of ways to distinguish those theories from
General Relativity observationally and experimentally. We also discuss the
extension to other modified gravity theories such as Brans-Dicke theory and
Gauss-Bonnet gravity, and address models that can satisfy both cosmological and
local gravity constraints.Comment: 156 pages, 14 figures, Invited review article in Living Reviews in
Relativity, Published version, Comments are welcom
X-Ray Spectroscopy of Stars
(abridged) Non-degenerate stars of essentially all spectral classes are soft
X-ray sources. Low-mass stars on the cooler part of the main sequence and their
pre-main sequence predecessors define the dominant stellar population in the
galaxy by number. Their X-ray spectra are reminiscent, in the broadest sense,
of X-ray spectra from the solar corona. X-ray emission from cool stars is
indeed ascribed to magnetically trapped hot gas analogous to the solar coronal
plasma. Coronal structure, its thermal stratification and geometric extent can
be interpreted based on various spectral diagnostics. New features have been
identified in pre-main sequence stars; some of these may be related to
accretion shocks on the stellar surface, fluorescence on circumstellar disks
due to X-ray irradiation, or shock heating in stellar outflows. Massive, hot
stars clearly dominate the interaction with the galactic interstellar medium:
they are the main sources of ionizing radiation, mechanical energy and chemical
enrichment in galaxies. High-energy emission permits to probe some of the most
important processes at work in these stars, and put constraints on their most
peculiar feature: the stellar wind. Here, we review recent advances in our
understanding of cool and hot stars through the study of X-ray spectra, in
particular high-resolution spectra now available from XMM-Newton and Chandra.
We address issues related to coronal structure, flares, the composition of
coronal plasma, X-ray production in accretion streams and outflows, X-rays from
single OB-type stars, massive binaries, magnetic hot objects and evolved WR
stars.Comment: accepted for Astron. Astrophys. Rev., 98 journal pages, 30 figures
(partly multiple); some corrections made after proof stag
Brane-World Gravity
The observable universe could be a 1+3-surface (the "brane") embedded in a
1+3+\textit{d}-dimensional spacetime (the "bulk"), with Standard Model
particles and fields trapped on the brane while gravity is free to access the
bulk. At least one of the \textit{d} extra spatial dimensions could be very
large relative to the Planck scale, which lowers the fundamental gravity scale,
possibly even down to the electroweak ( TeV) level. This revolutionary
picture arises in the framework of recent developments in M theory. The
1+10-dimensional M theory encompasses the known 1+9-dimensional superstring
theories, and is widely considered to be a promising potential route to quantum
gravity. At low energies, gravity is localized at the brane and general
relativity is recovered, but at high energies gravity "leaks" into the bulk,
behaving in a truly higher-dimensional way. This introduces significant changes
to gravitational dynamics and perturbations, with interesting and potentially
testable implications for high-energy astrophysics, black holes, and cosmology.
Brane-world models offer a phenomenological way to test some of the novel
predictions and corrections to general relativity that are implied by M theory.
This review analyzes the geometry, dynamics and perturbations of simple
brane-world models for cosmology and astrophysics, mainly focusing on warped
5-dimensional brane-worlds based on the Randall--Sundrum models. We also cover
the simplest brane-world models in which 4-dimensional gravity on the brane is
modified at \emph{low} energies -- the 5-dimensional Dvali--Gabadadze--Porrati
models. Then we discuss co-dimension two branes in 6-dimensional models.Comment: A major update of Living Reviews in Relativity 7:7 (2004)
"Brane-World Gravity", 119 pages, 28 figures, the update contains new
material on RS perturbations, including full numerical solutions of
gravitational waves and scalar perturbations, on DGP models, and also on 6D
models. A published version in Living Reviews in Relativit
45S rDNA external transcribed spacer organization reveals new phylogenetic relationships in Avena genus
Research ArticleThe genus Avena comprises four distinct genomes organized in diploid (AA or CC), tetraploid
(AABB or AACC) and hexaploid species (AACCDD), constituting an interesting model
for phylogenetic analysis. The aim of this work was to characterize 45S rDNA intergenic
spacer (IGS) variability in distinct species representative of Avena genome diversityÂąA.
strigosa (AA), A. ventricosa (CvCv), A. eriantha (CpCp), A. barbata (AABB), A. murphyi
(AACC), A. sativa (AACCDD) and A. sterilis (AACCDD) through the assessment of the 5'
external transcribed spacer (5'-ETS), a promising IGS region for phylogenetic studies poorly
studied in Avena genus. In this work, IGS length polymorphisms were detected mainly due
to distinct 5'-ETS sequence types resulting from major differences in the number and organization
of repeated motifs. Although species with A genome revealed a 5'-ETS organization
(A-organization) similar to the one previously described in A. sativa, a distinct organization
was unraveled in C genome diploid species (C-organization). Interestingly, such new organization
presents a higher similarity with other Poaceae species than A-genome sequences,
supporting the hypothesis of C-genome being the ancestral Avena genome. Additionally,
polyploid species with both genomes mainly retain the A-genome 5'-ETS organization, confirming
the preferential elimination of C-genome sequences in Avena polyploid species.
Moreover, 5'-ETS sequences phylogenetic analysis consistently clustered the species studied
according to ploidy and genomic constitution supporting the use of ribosomal genes to
highlight Avena species evolutive pathways.info:eu-repo/semantics/publishedVersio
- âŚ