1,000 research outputs found
Stellar model atmospheres with magnetic line blanketing
Model atmospheres of A and B stars are computed taking into account magnetic
line blanketing. These calculations are based on the new stellar model
atmosphere code LLModels which implements direct treatment of the opacities due
to the bound-bound transitions and ensures an accurate and detailed description
of the line absorption. The anomalous Zeeman effect was calculated for the
field strengths between 1 and 40 kG and a field vector perpendicular to the
line of sight. The model structure, high-resolution energy distribution,
photometric colors, metallic line spectra and the hydrogen Balmer line profiles
are computed for magnetic stars with different metallicities and are discussed
with respect to those of non-magnetic reference models. The magnetically
enhanced line blanketing changes the atmospheric structure and leads to a
redistribution of energy in the stellar spectrum. The most noticeable feature
in the optical region is the appearance of the 5200 A depression. However, this
effect is prominent only in cool A stars and disappears for higher effective
temperatures. The presence of a magnetic field produces opposite variation of
the flux distribution in the optical and UV region. A deficiency of the UV flux
is found for the whole range of considered effective temperatures, whereas the
``null wavelength'' where flux remains unchanged shifts towards the shorter
wavelengths for higher temperatures.Comment: accepted by Astronomy & Astrophysic
Stellar model atmospheres with magnetic line blanketing. III. The role of magnetic field inclination
Context. See abstract in the paper.
Aims. In the last paper of this series we study the effects of the magnetic
field, varying its strength and orientation, on the model atmosphere structure,
the energy distribution, photometric colors and the hydrogen Balmer line
profiles. We compare with the previous results for an isotropic case in order
to understand whether there is a clear relation between the value of the
magnetic field angle and model changes, and to study how important the
additional orientational information is. Also, we examine the probable
explanation of the visual flux depressions of the magnetic chemically peculiar
stars in the context of this work.
Methods. We calculated one more grid of the model atmospheres of magnetic A
and B stars for different effective temperatures (Teff=8000K, 11000K, 15000K),
magnetic field strengths (B=0, 5, 10, 40 kG) and various angles of the magnetic
field (Omega=0-90 degr) with respect to the atmosphere plane. We used the
LLmodels code which implements a direct method for line opacity calculation,
anomalous Zeeman splitting of spectral lines, and polarized radiation transfer.
Results. We have not found significant changes in model atmosphere structure,
photometric and spectroscopic observables or profiles of hydrogen Balmer lines
as we vary the magnetic field inclination angle Omega. The strength of the
magnetic field plays the main role in magnetic line blanketing. We show that
the magnetic field has a clear relation to the visual flux depressions of the
magnetic CP stars.
Conclusions. See abstract in the paper.Comment: 10 pages, 5 figure
Angle dependence of Andreev scattering at semiconductor-superconductor interfaces
We study the angle dependence of the Andreev scattering at a
semiconductor-superconductor interface, generalizing the one-dimensional theory
of Blonder, Tinkham and Klapwijk. An increase of the momentum parallel to the
interface leads to suppression of the probability of Andreev reflection and
increase of the probability of normal reflection. We show that in the presence
of a Fermi velocity mismatch between the semiconductor and the superconductor
the angles of incidence and transmission are related according to the
well-known Snell's law in optics. As a consequence there is a critical angle of
incidence above which only normal reflection exists. For two and
three-dimensional interfaces a lower excess current compared to ballistic
transport with perpendicular incidence is found. Thus, the one-dimensional BTK
model overestimates the barrier strength for two and three-dimensional
interfaces.Comment: 8 pages including 3 figures (revised, 6 references added
Regulation of theTNFR1-signalling complex by LUBAC and associated deubiquitinases
TNF is an inflammatory cytokine, vital for innate immune responses but also involved in pathological conditions including rheumatoid arthritis, psoriasis and inflammatory bowel disease. Assembly of the TNFR1-signalling complex (SC) is regulated and post-translational modifications play a crucial part in executing this regulation. The aim of this study was to characterise how LUBAC contributes to TNFR1-SC assembly, NF-B and MAPK pathway activation and prevention of cell death by influencing complex composition and ubiquitination. Using mass spectrometry OTULIN, CYLD and SPATA2 were identified as constitutive interaction partners of LUBAC. Interaction studies revealed that despite constitutive binding of OTULIN, SPATA2 and CYLD with the LUBAC component HOIP, only SPATA2 and CYLD are recruited to SCs. Strikingly, CYLD requires HOIP and SPATA2 for its recruitment to SCs, where CYLD counteracts LUBAC by cleaving ubiquitin chains. Consequently, CYLD enables TNF-induced cell death and supresses NF-B and MAPK activation in NOD2 signalling. Using a newly developed methodology TNFR1 and TRADD were identified as LUBAC substrates and absence of CYLD leads to increased ubiquitination of these proteins. In line with pro-survival functions of linear ubiquitination, depletion of either CYLD or SPATA2 protects cells from TNF-induced necroptosis. OTULIN, on the other hand, antagonises linear ubiquitination and regulates LUBAC in basal conditions by deubiquitinating its subunits and preventing aberrant linear ubiquitination. The protein A20 was found to require linear ubiquitin chains for its recruitment to the TNFR1-SC. A20, although negatively regulating NF-B signalling, is required to prevent TNF-induced cell death by stabilising linear ubiquitination of TNFR1-SC components. In summary, this study identified LUBAC to be central for CYLD and A20 recruitment to SCs and provides an explanation for the opposing role of CYLD and A20 in regulating TNF-mediated cell death despite their overlapping function in suppression of gene activatory pathways
Electronic States in Diffused Quantum Wells
In the present study we calculate the energy values and the spatial
distributions of the bound electronic states in some diffused quantum wells.
The calculations are performed within the virtual crystal approximation, spin dependent empirical tight-binding model and the surface Green
function matching method. A good agreement is found between our results and
experimental data obtained for AlGaAs/GaAs quantum wells with thermally induced
changes in the profile at the interfaces. Our calculations show that for
diffusion lengths {\AA} the transition (C3-HH3) is not
sensitive to the diffusion length, but the transitions (C1-HH1), (C1-LH1),
(C2-HH2) and (C2-LH2) display large "blue shifts" as L_{D} increases. For
diffusion lengths {\AA} the transitions (C1-HH1) and (C1-LH1)
are less sensitive to the L_{D} changes than the (C3-HH3) transition. The
observed dependence is explained in terms of the bound states spatial
distributions.Comment: ReVTeX file, 7pp., no macros, 4 figures available on the reques
Recommended from our members
Cost-effectiveness of community-based screening and treatment of moderate acute malnutrition in Mali.
IntroductionModerate acute malnutrition (MAM) causes substantial child morbidity and mortality, accounting for 4.4% of deaths and 6.0% of disability-adjusted life years (DALY) lost among children under 5 each year. There is growing consensus on the need to provide appropriate treatment of MAM, both to reduce associated morbidity and mortality and to halt its progression to severe acute malnutrition. We estimated health outcomes, costs and cost-effectiveness of four dietary supplements for MAM treatment in children 6-35 months of age in Mali.MethodsWe conducted a cluster-randomised MAM treatment trial to describe nutritional outcomes of four dietary supplements for the management of MAM: ready-to-use supplementary foods (RUSF; PlumpySup); a specially formulated corn-soy blend (CSB) containing dehulled soybean flour, maize flour, dried skimmed milk, soy oil and a micronutrient pre-mix (CSB++; Super Cereal Plus); Misola, a locally produced, micronutrient-fortified, cereal-legume blend (MI); and locally milled flour (LMF), a mixture of millet, beans, oil and sugar, with a separate micronutrient powder. We used a decision tree model to estimate long-term outcomes and calculated incremental cost-effectiveness ratios (ICERs) comparing the health and economic outcomes of each strategy.ResultsCompared to no MAM treatment, MAM treatment with RUSF, CSB++, MI and LMF reduced the risk of death by 15.4%, 12.7%, 11.9% and 10.3%, respectively. The ICER was US347 per DALY averted for RUSF compared with no MAM treatment.ConclusionMAM treatment with RUSF is cost-effective across a wide range of willingness-to-pay thresholds.Trial registrationNCT01015950
Ispitivanja statičke kompresije i rezonantne vibracije celularnih materijala dobivenih gravitacijskim sinterovanjem šupljih brončanih kugli
The cylindrical and rod-shaped specimens were prepared by gravity sintering from Cu-Sn hollow spheres. On these samples, both static compression tests and measurements of resonance frequencies were performed. The compressive stress-strain curves revealed the features characteristic for a closed-cell ductile cellular solid. The removal of in general open porosity among loosely packed closed metallic hollow spheres was recognized as the principal mode of plastic deformation. The approximative effective moduli of elasticity were determined for cellular materials under consideration by means of the measurements of resonance frequencies on rod-shaped specimens.Cilindrični i šipkasti uzorci su pripremljeni gravitacionim sinterovanjem šupljih Cu-Sn kugli. Na tim uzorcima su provedena ispitivanja statičke kompresije i mjerenja rezonantnih frekvencija. Krivulja naprezanje-rastezanje nam pokazuje svojstva karakteristična za plastične celularne krute materijale sa zatvorenim ćelijama. Uklanjanje uglavnom otvorene povezanosti među labavo povezanim šupljim metalnim kuglama prepoznajemo kao glavni način plastične deformacije. Za celularne materijale koji se razmatraju određeni su približno učinkoviti moduli elastičnosti mjerenjem frekvencija rezonancije na šipkasto oblikovanim uzorcima
The broadening of Fe II lines by neutral hydrogen collisions
Data for the broadening of 24188 Fe II lines by collisions with neutral
hydrogen atoms have been computed using the theory of Anstee & O'Mara as
extended to singly ionised species and higher orbital angular momentum states
by Barklem & O'Mara. Data have been computed for all Fe II lines between
observed energy levels in the line lists of Kurucz with log gf > -5 for which
the theory is applicable. The variable energy debt parameter Ep used in
computing the second order perturbation theory potential is chosen to be
consistent with the long range dispersion interaction constant C6 computed
using the f-values from Kurucz.Comment: Accepted for A&A. 5 pages, 5 figures, 2 electronic tables. Tables
will be available via CDS; presently also at
http://www.astro.uu.se/~barklem/papers/fe2_data.tar.g
Turbulent convection: comparing the moment equations to numerical simulations
The non-local hydrodynamic moment equations for compressible convection are
compared to numerical simulations. Convective and radiative flux typically
deviate less than 20% from the 3D simulations, while mean thermodynamic
quantities are accurate to at least 2% for the cases we have investigated. The
moment equations are solved in minutes rather than days on standard
workstations. We conclude that this convection model has the potential to
considerably improve the modelling of convection zones in stellar envelopes and
cores, in particular of A and F stars.Comment: 10 pages (6 pages of text including figure captions + 4 figures),
Latex 2e with AAS Latex 5.0 macros, accepted for publication in ApJ
Evidence of inhibin/activin subunit betaC and betaE synthesis in normal human endometrial tissue
<p>Abstract</p> <p>Background</p> <p>Inhibins are important regulators of the female reproductive system. Recently, two new inhibin subunits betaC and betaE have been described, although it is unclear if they are synthesized in normal human endometrium.</p> <p>Methods</p> <p>Samples of human endometrium were obtained from 82 premenopausal, non-pregnant patients undergoing gynecological surgery for benign diseases. Endometrium samples were classified according to anamnestic and histological dating into proliferative (day 1-14, n = 46), early secretory (day 15-22, n = 18) and late secretory phase (day 23-28, n = 18). Immunohistochemical analyses were performed with specific antibodies against inhibin alpha (n = 81) as well as inhibin betaA (n = 82), betaB (n = 82), betaC (n = 74) and betaE (n = 76) subunits. RT-PCR was performed for all inhibin subunits. Correlation was assessed with the Spearman factor to assess the relationship of inhibin-subunits expression within the different endometrial samples.</p> <p>Results</p> <p>The novel inhibin betaC and betaE subunits were found in normal human endometrium by immunohistochemical and molecular techniques. Inhibin alpha, betaA, betaB and betaE subunits showed a circadian expression pattern, being more abundant during the late secretory phase than during the proliferative phase. Additionally, a significant correlation between inhibin alpha and all inhibin beta subunits was observed.</p> <p>Conclusions</p> <p>The differential expression pattern of the betaC- and betaE-subunits in normal human endometrial tissue suggests that they function in endometrial maturation and blastocyst implantation. However, the precise role of these novel inhibin/activin subunits in human endometrium is unclear and warrants further investigation.</p
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