9,643 research outputs found
Dust absorption and scattering in the silicon K-edge
The composition and properties of interstellar silicate dust are not well
understood. In X-rays, interstellar dust can be studied in detail by making use
of the fine structure features in the Si K-edge. The features in the Si K-edge
offer a range of possibilities to study silicon-bearing dust, such as
investigating the crystallinity, abundance, and the chemical composition along
a given line of sight. We present newly acquired laboratory measurements of the
silicon K-edge of several silicate-compounds that complement our measurements
from our earlier pilot study. The resulting dust extinction profiles serve as
templates for the interstellar extinction that we observe. The extinction
profiles were used to model the interstellar dust in the dense environments of
the Galaxy. The laboratory measurements, taken at the Soleil synchrotron
facility in Paris, were adapted for astrophysical data analysis and implemented
in the SPEX spectral fitting program. The models were used to fit the spectra
of nine low-mass X-ray binaries located in the Galactic center neighborhood in
order to determine the dust properties along those lines of sight. Most lines
of sight can be fit well by amorphous olivine. We also established upper limits
on the amount of crystalline material that the modeling allows. We obtained
values of the total silicon abundance, silicon dust abundance, and depletion
along each of the sightlines. We find a possible gradient of
dex/kpc for the total silicon abundance versus the Galactocentric distance. We
do not find a relation between the depletion and the extinction along the line
of sight.Comment: 18 pages, 16 figures. Accepted for publication in Astronomy and
Astrophysic
The relation between cardiac 123I-mIBG scintigraphy and functional response 1 year after CRT implantation
Cardiac resynchronization therapy (CRT) is a disease-modifying therapy in patients with chronic heart failure (CHF). Current guidelines ascribe CRT eligibility on three parameters only: left ventricular ejection fraction (LVEF), QRS duration, and New York Heart Association (NYHA) functional class. However, one-third of CHF patients does not benefit from CRT. This study evaluated whether 123I-meta-iodobenzylguanidine (123I-mIBG) assessed cardiac sympathetic activity could optimize CRT patient selection
Band Offsets at the Interface between Crystalline and Amorphous Silicon from First Principles
The band offsets between crystalline and hydrogenated amorphous silicon
(a-Si:H) are key parameters governing the charge transport in modern silicon
hetrojunction solar cells. They are an important input for macroscopic
simulators that are used to further optimize the solar cell. Past experimental
studies, using X-ray photoelectron spectroscopy (XPS) and capacitance-voltage
measurements, have yielded conflicting results on the band offset. Here we
present a computational study on the band offsets. It is based on atomistic
models and density-functional theory (DFT). The amorphous part of the interface
is obtained by relatively long DFT first-principles molecular-dynamics (MD)
runs at an elevated temperature on 30 statistically independent samples. In
order to obtain a realistic conduction band position the electronic structure
of the interface is calculated with a hybrid functional. We find a slight
asymmetry in the band offsets, where the offset in the valence band (0.30 eV)
is larger than in the conduction band (0.17 eV). Our results are in agreement
with the latest XPS measurements that report a valence band offset of 0.3 eV
[M. Liebhaber et al., Appl. Phys. Lett. 106, 031601 (2015)]
Correlated evolution of nucleotide substitution rates and allelic variation in Mhc-DRB lineages of primates
<p>Abstract</p> <p>Background</p> <p>The major histocompatibility complex (MHC) is a key model of genetic polymorphism. Selection pressure by pathogens or other microevolutionary forces may result in a high rate of non-synonymous substitutions at the codons specifying the contact residues of the antigen binding sites (ABS), and the maintenance of extreme MHC allelic variation at the population/species level. Therefore, selection forces favouring MHC variability for any reason should cause a correlated evolution between substitution rates and allelic polymorphism. To investigate this prediction, we characterised nucleotide substitution rates and allelic polymorphism (i.e. the number of alleles detected in relation to the number of animals screened) of several <it>Mhc </it>class II <it>DRB </it>lineages in 46 primate species, and tested for a correlation between them.</p> <p>Results</p> <p>First, we demonstrate that species-specific and lineage-specific evolutionary constraints favour species- and lineage-dependent substitution rate at the codons specifying the ABS contact residues (i.e. certain species and lineages can be characterised by high substitution rate, while others have low rate). Second, we show that although the degree of the non-synonymous substitution rate at the ABS contact residues was systematically higher than the degree of the synonymous substitution rate, these estimates were strongly correlated when we controlled for species-specific and lineage-specific effects, and also for the fact that different studies relied on different sample size. Such relationships between substitution rates of different types could even be extended to the non-contact residues of the molecule. Third, we provide statistical evidence that increased substitution rate along a MHC gene may lead to allelic variation, as a high substitution rate can be observed in those lineages in which many alleles are maintained. Fourth, we show that the detected patterns were independent of phylogenetic constraints. When we used phylogenetic models that control for similarity between species, due to common descent, and focused on variations within a single lineage (<it>DRB1*03</it>), the positive relationship between different substitution rates and allelic polymorphisms was still robust. Finally, we found the same effects to emerge in the analyses that eliminated within-species variation in MHC traits by using strictly single population-level studies. However, in a set of contrasting analyses, in which we focused on the non-functional <it>DRB6 </it>locus, the correlation between substitution rates and allelic variation was not prevalent.</p> <p>Conclusion</p> <p>Our results indicate that positive selection for the generation of allelic polymorphism acting on the functional part of the protein has consequences for the nucleotide substitution rate along the whole exon 2 sequence of the <it>Mhc-DRB </it>gene. Additionally, we proved that an increased substitution rate can promote allelic variation within lineages. Consequently, the evolution of different characteristics of genetic polymorphism is not independent.</p
Energy and entropy of relativistic diffusing particles
We discuss energy-momentum tensor and the second law of thermodynamics for a
system of relativistic diffusing particles. We calculate the energy and entropy
flow in this system. We obtain an exact time dependence of energy, entropy and
free energy of a beam of photons in a reservoir of a fixed temperature.Comment: 14 pages,some formulas correcte
Optical supercavitation in soft-matter
We investigate theoretically, numerically and experimentally nonlinear
optical waves in an absorbing out-of-equilibrium colloidal material at the
gelification transition. At sufficiently high optical intensity, absorption is
frustrated and light propagates into the medium. The process is mediated by the
formation of a matter-shock wave due to optically induced thermodiffusion, and
largely resembles the mechanism of hydrodynamical supercavitation, as it is
accompanied by a dynamic phase-transition region between the beam and the
absorbing material.Comment: 4 pages, 5 figures, revised version: corrected typos and reference
Форми затримки статевого дозрівання дівчаток, що проживають за умов дефіциту йоду
Вступ. У районах йодного дефіциту виявлена низька частка школярів, що мають гармонійний розвиток особистості, у третини дітей реєструються відхилення у статевому розвитку, а у половини дівчаток спостерігаються порушення показників репродуктивного здоров’я. Мета. Вивчити показники статевого розвитку у дітей із зони йодного дефіциту
The thermodynamic dual structure of linear-dissipative driven systems
The spontaneous emergence of dynamical order, such as persistent currents, is
sometimes argued to require principles beyond the entropy maximization of the
second law of thermodynamics. I show that, for linear dissipation in the
Onsager regime, current formation can be driven by exactly the Jaynesian
principle of entropy maximization, suitably formulated for extended systems and
nonequilibrium boundary conditions. The Legendre dual structure of equilibrium
thermodynamics is also preserved, though it requires the admission of
current-valued state variables, and their correct incorporation in the entropy
Web-based personalised information and support for patients with a neuroendocrine tumour:randomised controlled trial
BackgroundPatients with a neuroendocrine tumour (NET) frequently have physical and psychosocial complaints. Aim of this study is to determine whether a web-based, personalised information and support system (WINS) reduces distress and/or improves patients' perception of and satisfaction with information received.MethodsPatients with NET, stratified for those newly diagnosed (</p
Phase separation of binary fluids with dynamic temperature
Phase separation of binary fluids quenched by contact with cold external
walls is considered. Navier-Stokes, convection-diffusion, and energy equations
are solved by lattice Boltzmann method coupled with finite-difference schemes.
At high viscosity, different morphologies are observed by varying the thermal
diffusivity. In the range of thermal diffusivities with domains growing
parallel to the walls, temperature and phase separation fronts propagate
towards the inner of the system with power-law behavior. At low viscosity
hydrodynamics favors rounded shapes, and complex patterns with different
lengthscales appear. Off-symmetrical systems behave similarly but with more
ordered configurations.Comment: Accepted for publication in Phys. Rev. E, 11 figures, best quality
figures available on reques
- …