2,537 research outputs found
On the accuracy of the Perturbative Approach for Strong Lensing: Local Distortion for Pseudo-Elliptical Models
The Perturbative Approach (PA) introduced by \citet{alard07} provides
analytic solutions for gravitational arcs by solving the lens equation
linearized around the Einstein ring solution. This is a powerful method for
lens inversion and simulations in that it can be used, in principle, for
generic lens models. In this paper we aim to quantify the domain of validity of
this method for three quantities derived from the linearized mapping: caustics,
critical curves, and the deformation cross section (i.e. the arc cross section
in the infinitesimal circular source approximation). We consider lens models
with elliptical potentials, in particular the Singular Isothermal Elliptic
Potential and Pseudo-Elliptical Navarro--Frenk--White models. We show that the
PA is exact for this first model. For the second, we obtain constraints on the
model parameter space (given by the potential ellipticity parameter
and characteristic convergence ) such that the PA is
accurate for the aforementioned quantities. In this process we obtain analytic
expressions for several lensing functions, which are valid for the PA in
general. The determination of this domain of validity could have significant
implications for the use of the PA, but it still needs to be probed with
extended sources.Comment: Accepted for publication in MNRA
INTEGRAL Spectroscopy of IRAS 17208-0014: Implications for the Evolutionary Scenarios of Ultraluminous Infrared Galaxies
New integral field optical fiber spectroscopy obtained with the INTEGRAL
system, together with archival {\it {\it HST}} WFPC2 and NICMOS images, have
been used to investigate the ultraluminous infrared galaxy IRAS 172080014,
one of the coldest and most luminous objects in the IRAS 1 Jy sample. The 2D
gas velocity field identifies the {\it optically faint} K-band nucleus as the
{\it true} dynamical nucleus of the galaxy, and shows that the 3 kpc, tilted (i
35 degree) disk is rotating at Vsin= 250 km s. The
kinematical, morphological and photometric evidence presented here supports the
idea that in IRAS 17208-0014 we are witnessing a luminous, cool ULIRG which is
at the final coalescence phase of a system composed of two spirals with m
m, a mass ratio of 2:1, each consisting of a disk+bulge internal
structure, that have been involved in a prograde encounter. This system will
most likely evolve into an intermediate-mass ( L) elliptical. The
multifrequency empirical evidence gathered so far shows no trace of a luminous
QSO, and indicates that starbursts dominate the energy output in this galaxy.
Therefore IRAS 172080014 questions the universality of the ULIRG to QSO
evolutionary scenario proposed by Sanders and collaborators, and supports the
one recently proposed by Colina et al, where two low mass disk galaxies would
produce luminous cool ULIRGs that would not evolve into a QSO phase. (abridge)Comment: Astrophysical Journal (in press
Glatiramer acetate treatment does not modify the clinical course of (NZB × BXSB)F1 lupus murine model
Glatiramer acetate (GA, copolymer-1, Copaxone®), a therapy approved for treatment of multiple sclerosis (MS), prevents and reverses experimental autoimmune encephalomyelitis, the animal model of MS. In central nervous system autoimmune disease, GA is thought to act through modulation of antigen-presenting cells, such as monocytes, mediating an antigen-independent Th2 shift and development of FoxP3+ regulatory T cells. Recent reports indicate that GA may also be effective in models of other autoimmune diseases such as uveoretinitis, inflammatory bowel disease and graft rejection. To date, the potential effect of GA in lupus animal models has not been described. (NZB × BXSB)F1, male mice bearing Y-linked autoimmune acceleration , is a lupus-prone mouse model which is associated with a monocytosis accelerating disease progression. These mice were treated with GA before disease onset until death and both mortality rate and biological parameters were assessed to investigate whether GA may be beneficial in this spontaneous model of systemic lupus erythematosus. GA exerted no beneficial effect on the median survival after up to 7 months of treatment. Humoral and cellular parameters used as markers for lupus progression, such as anti-chromatin, anti-double-stranded DNA and anti-erythrocytes antibodies, hematocrit and monocytosis, were similarly unchanged. Our study demonstrates that GA has no significant effect on the progression of the (NZB × BXSB)F1 lupus-prone animal model. These results reinforce the hypothesis that GA may exert its beneficial effect in some specific autoimmune diseases onl
Pancreatic intraductal papillary mucinous neoplasm associated colloid carcinoma
Funding Information: Acknowledgments: Special thanks to Celso Matos, MD/PhD, for assistance with manuscrip preparation. The authors received no financial support for the publication of this article. Publisher Copyright: © 2021Colloid carcinomas are rare pancreatic tumors characterized by the presence of mucin pools with scarce malignant cells. Most of these neoplasms arise from intestinal-type intraductal papillary mucinous neoplasms (IPMNs). We report a case of a 77-year-old male patient who presented with weight loss, asthenia, lumbar pain and diabetes. Imaging studies revealed a mixed-type IPMN with high-risk features and a possible invasive component. The patient underwent surgical resection and the histology confirmed an invasive colloid carcinoma of the pancreas associated with an intestinal-type IPMN. Although invasive ductal and colloid carcinomas may look similar on imaging studies, its distinction is important because the latter have a better prognosis.publishersversionpublishe
Parton distributions from deep-inelastic-scattering data
We perform the analysis of existing light-targets deep-inelastic-scattering
(DIS) data in the leading-order (LO), next-to-leading-order (NLO), and
next-to-next-to-leading-order (NNLO) QCD approximations and extract PDFs
simultaneously with the value of the strong coupling constant and
the high-twist contribution to the structure functions. The main theoretical
uncertainties and experimental uncertainties due to all sources of experimental
errors in data are estimated, the latter generally dominate for the obtained
PDFs. The uncertainty in Higgs boson production cross section due to errors in
PDFs is % for the LHC and varies from 2% to 10% for the Fermilab
collider under variation of the Higgs boson mass from to . For the -boson production cross section the uncertainty is % for the both colliders. The value of is obtained, while the high-twist terms do
not vanish up to the NNLO as required by comparison to data
The SOAR Gravitational Arc Survey - I: Survey overview and photometric catalogs
We present the first results of the SOAR (Southern Astrophysical Research)
Gravitational Arc Survey (SOGRAS). The survey imaged 47 clusters in two
redshift intervals centered at and , targeting the richest
clusters in each interval. Images were obtained in the , and
bands using the SOAR Optical Imager (SOI), with a median seeing of 0.83, 0.76
and 0.71 arcsec, respectively, in these filters. Most of the survey clusters
are located within the Sloan Digital Sky Survey (SDSS) Stripe 82 region and all
of them are in the SDSS footprint. Photometric calibration was therefore
performed using SDSS stars located in our SOI fields. We reached for galaxies
in all fields the detection limits of , and for a signal-to-noise ratio (S/N) = 3. As a by-product of the image
processing, we generated a source catalogue with 19760 entries, the vast
majority of which are galaxies, where we list their positions, magnitudes and
shape parameters. We compared our galaxy shape measurements to those of local
galaxies and concluded that they were not strongly affected by seeing. From the
catalogue data, we are able to identify a red sequence of galaxies in most
clusters in the lower range. We found 16 gravitational arc candidates
around 8 clusters in our sample. They tend to be bluer than the central
galaxies in the lensing cluster. A preliminary analysis indicates that of the clusters have arcs around them, with a possible indication of a
larger efficiency associated to the high- systems when compared to the
low- ones. Deeper follow-up images with Gemini strengthen the case for the
strong lensing nature of the candidates found in this survey.Comment: 17 pages, 11 figures (most of them multi-panel) MNRAS (2013
Impact of Higher Order and Soft Gluon Corrections on the Extraction of Higher Twist Effects in DIS
The impact of recently calculated next-to-next-to-leading order QCD
corrections and soft gluon resummations on the extraction of higher twist
contributions to the deep-inelastic structure function F_2 is studied using the
BCDMS and SLAC data. It is demonstrated to which extent the need for higher
twist terms is diminishing due to these higher order effects in the kinematical
region, 0.35 \le x \le 0.85 and Q^2>1.2 GeV^2, investigated. In addition,
theoretical uncertainties in the extraction of higher twist contributions are
discussed, and comparisons to results obtained previously are made.Comment: 16 pages, 3 figure
Exploring the Impact of the HOMO–LUMO Gap on Molecular Thermoelectric Properties: A Comparative Study of Conjugated Aromatic, Quinoidal, and Donor–Acceptor Core Systems
Thermoelectric materials have garnered significant interest for their potential to efficiently convert waste heat into electrical energy at room temperature without moving parts or harmful emissions. This study investigated the impact of the HOMO–LUMO (H-L) gap on the thermoelectric properties of three distinct classes of organic compounds: conjugated aromatics (isoindigos (IIGs)), quinoidal molecules (benzodipyrrolidones (BDPs)), and donor–acceptor systems (bisÂ(pyrrol-2-yl)Âsquaraines (BPSs)). These compounds were chosen for their structural simplicity and linear Ï€-conjugated conductance paths, which promote high electrical conductance and minimize complications from quantum interference. Single-molecule thermoelectric measurements revealed that despite their low H-L gaps, the Seebeck coefficients of these compounds remain low. The alignment of the frontier orbitals relative to the Fermi energy was found to play a crucial role in determining the Seebeck coefficients, as exemplified by the BDP compounds. Theoretical calculations support these findings and suggest that anchor group selection could further enhance the thermoelectric behavior of these types of molecules
Calculation of on the Z
We perform a new, detailed calculation of the hadronic contributions to the
running electromagnetic coupling, , defined on the Z particle (91
GeV). We find for the hadronic contribution, including radiative corrections,
10^5\times \deltav_{\rm had.}\alpha(M_Z^2)= 2740\pm12, or, excluding the
top quark contribution, 10^5\times \deltav_{\rm had.}\alpha^{(5)}(M_Z^2)=
2747\pm12.
Adding the pure QED corrections we get a value for the running
electromagnetic coupling of Comment: Version to appear in Phys. Rev. D. Plain TeX fil
Transient evolution of C-type shocks in dusty regions of varying density
Outflows of young stars drive shocks into dusty, molecular regions. Most
models of such shocks assume that they are steady and propagating perpendicular
to the magnetic field. Real shocks often violate both of these assumptions and
the media through which they propagate are inhomogeneous. We use the code
employed previously to produce the first time-dependent simulations of
fast-mode, oblique C-type shocks interacting with density perturbations. We
include a self-consistent calculation of the thermal and ionisation balances
and a fluid treatment of grains. We identify features that develop when a
multifluid shock encounters a density inhomogeneity to investigate whether any
part of the precursor region ever behaves in a quasi-steady fashion. If it does
the shock may be modelled approximately without solving the time-dependent
hydromagnetic equations. Simulations were made for initially steady oblique
C-type shocks encountering density inhomogeneities. For a semi-finite
inhomogeneity with a density larger than the surrounding medium, a transmitted
shock evolves from being J-type to a steady C-type shock on a timescale
comparable to the ion-flow time through it. A sufficiently upstream part of the
precursor of an evolving J-type shock is quasi-steady. The ion-flow timescale
is also relevant for the evolution of a shock moving into a region of
decreasing density. The models for shocks propagating into regions in which the
density increases and then decreases to its initial value cannot be entirely
described in terms of the results obtained for monotonically increasing and
decreasing densities. For the latter model, the long-term evolution to a C-type
shock cannot be approximated by quasi-steady models.Comment: 11 pages, 9 figure
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