1,152 research outputs found
The Sloan Lens ACS Survey. VI: Discovery and analysis of a double Einstein ring
We report the discovery of two concentric Einstein rings around the
gravitational lens SDSSJ0946+1006, as part of the Sloan Lens ACS Survey. The
main lens is at redshift zl=0.222, while the inner ring (1) is at zs1=0.609 and
Einstein radius . The wider image separation () of the outer ring (2) implies that it is at higher redshift. Its
detection in the F814W filter implies zs2<6.9. The configuration can be well
described by a total density profile with
and velocity dispersion \sigma_{SIE}=287\pm5\kms. [...] We consider whether
this configuration can be used to constrain cosmological parameters exploiting
angular distance ratios entering the lens equations. Constraints for
SDSSJ0946+1006, are uninteresting due to the sub-optimal lens and source
redshifts. We then consider the perturbing effect of the mass associated with
Ring 1 building a double lens plane compound lens model. This introduces minor
changes to the mass of the main lens and allows to estimate the mass of Ring 1
(\sigma_{SIE,s1}=94\pm30\kms). We examine the prospects of doing cosmography
with a sample of 50 double lenses, expected from future space based surveys
such as DUNE or JDEM. Taking full account of the model uncertainties, such a
sample could be used to measure and with 10% accuracy, for a
flat cosmology
Assessment of the allergic potential of food protein extracts and proteins on oral application using the brown Norway rat model.
The need for widely accepted and validated animal models to test the potential allergenicity and potency of novel (biotechnology-derived) proteins has become an important issue for their safety evaluation. In this article, we summarize the results of the development of an oral sensitization protocol for food proteins in the rat. Young Brown Norway rats were exposed to either various purified allergenic proteins (e.g., ovalbumin, partly purified), a whole food (cow's milk), or total protein extracts (hen's egg white, peanut) by daily gavage dosing during 42 days without the use of an adjuvant. The results showed that Brown Norway rats can be sensitized orally to the various allergenic food proteins tested, resulting in antigen-specific immunoglobulin (Ig) G and IgE responses, without the use of adjuvants. Animals orally exposed to cow's milk or total protein extracts of egg white also developed specific IgE and IgG antibodies that recognized the same proteins compared with antibodies from patients allergic to egg white or cow's milk. We also studied local and systemic immune-mediated effects. In ovalbumin-sensitized rats, some clinical symptoms of food allergy were studied upon an oral challenge with ovalbumin. The results demonstrated that gut permeability was increased and that in some animals breathing frequency and systolic blood pressure were temporarily decreased. The results obtained show that the Brown Norway rat provides a suitable animal model for food allergy research and for the study of relative allergenicity of existing and novel food proteins
The SWELLS survey. IV. Precision measurements of the stellar and dark matter distributions in a spiral lens galaxy
We construct a fully self-consistent mass model for the lens galaxy J2141 at
z=0.14, and use it to improve on previous studies by modelling its
gravitational lensing effect, gas rotation curve and stellar kinematics
simultaneously. We adopt a very flexible axisymmetric mass model constituted by
a generalized NFW dark matter halo and a stellar mass distribution obtained by
deprojecting the MGE fit to the high-resolution K'-band LGSAO imaging data of
the galaxy, with the (spatially constant) M/L ratio as a free parameter. We
model the stellar kinematics by solving the anisotropic Jeans equations. We
find that the inner logarithmic slope of the dark halo is weakly constrained
(gamma = 0.82^{+0.65}_{-0.54}), and consistent with an unmodified NFW profile.
We infer the galaxy to have (i) a dark matter fraction within 2.2 disk radii of
0.28^{+0.15}_{-0.10}, independent of the galaxy stellar population, implying a
maximal disk for J2141; (ii) an apparently uncontracted dark matter halo, with
concentration c_{-2} = 7.7_{-2.5}^{+4.2} and virial velocity v_{vir} =
242_{-39}^{+44} km/s, consistent with LCDM predictions; (iii) a slightly oblate
halo (q_h = 0.75^{+0.27}_{-0.16}), consistent with predictions from
baryon-affected models. Comparing the stellar mass inferred from the combined
analysis (log_{10} Mstar/Msun = 11.12_{-0.09}^{+0.05}) with that inferred from
SPS modelling of the galaxies colours, and accounting for a cold gas fraction
of 20+/-10%, we determine a preference for a Chabrier IMF over Salpeter IMF by
a Bayes factor of 5.7 (substantial evidence). We infer a value beta_{z} = 1 -
sigma^2_{z}/sigma^2_{R} = 0.43_{-0.11}^{+0.08} for the orbital anisotropy
parameter in the meridional plane, in agreement with most studies of local disk
galaxies, and ruling out at 99% CL that the dynamics of this system can be
described by a two-integral distribution function. [Abridged]Comment: Accepted for publication in MNRAS. 17 pages, 9 figure
Characterization of aerosol pollution events in France using ground-based and POLDER-2 satellite data
We analyze the relationship between daily fine particle mass concentration (PM2.5) and columnar aerosol optical thickness derived from the Polarization and Directionality of Earth's Reflectances (POLDER) satellite sensor. The study is focused over France during the POLDER-2 lifetime between April and October 2003. We have first compared the POLDER derived aerosol optical thickness (AOT) with integrated volume size distribution derived from ground-based Sun Photometer observations. The good correlation (R=0.72) with sub-micron volume fraction indicates that POLDER derived AOT is sensitive to the fine aerosol mass concentration. Considering 1974 match-up data points over 28 fine particle monitoring sites, the POLDER-2 derived AOT is fairly well correlated with collocated PM2.5 measurements, with a correlation coefficient of 0.55. The correlation coefficient reaches a maximum of 0.80 for particular sites. We have analyzed the probability to find an appropriate air quality category (AQC) as defined by U.S. Environmental Protection Agency (EPA) from POLDER-2 AOT measurements. The probability can be up to 88.8% (±3.7%) for the "Good" AQC and 89.1% (±3.6%) for the "Moderate" AQC
Human Germinal Center CD4+ CD57+ T Cells Act Differently On B Cells Than Do Classical T-Helper Cells
We have isolated two subtypes of helper T cells from human tonsils: CD4+ CD57+ cells,
mostly located in the germinal center (GC), and CD4+ CD57- cells, distributed through the
interfollicular areas but also present in the GC. In a functional study, we have compared the
capacities of these T-cell subtypes to stimulate B cells in cocultures. In order to block T-cell
proliferation while maintaining their activation level, we pretreated isolated T cells with
mitomycin C prior to culture in the presence of B cells and added polyclonal activators such
as PHA and Con A, combined or not with IL-2. Contrary to CD4+ CD57- cells,
CD4+ CD57+ cells did not markedly enhance B-cell proliferation. Even when sIgD-B cells
typical of germinal center cells were tested, the CD4 CD57 cells had no significant effect.
This is in accordance with the location of these cells: They mainly occupy the light zones
of the GC where few B cells divide. Even when added to preactivated, actively proliferating
cells, CD4+ CD57+ cells failed to modulate B-cell multiplication. On the supernatants of
B-cell-T-cell cocultures, we examined by the ELISA technique the effect of T cells on Ig
synthesis. Contrary to CD57- T cells, whose effect was strong, CD57+ T cells weakly
stimulated Ig synthesis. More IgM than IgG was generally found. Because CD57 antigen is
a typical marker of natural killer cells, we tested the cytolytic activity of tonsillar
CD4+ CD57+ cells on K562 target cells. Unlike NK cells, neither CD4+CD57+ nor
CD4+ CD57- cells exhibit any cytotoxicity. Thus, germinal center CD4+ CD57+ cells are not
cytolytic and do not strongly stimulate either B-cell proliferation or Ig secretion.
CD4+ CD57- cells, however, enhance B-cell proliferation and differentiation, thus acting
like the classical helper cells of the T-dependent areas
La Société de protection des plantes du Québec, 1908-2008
Ă lâaide de documents Ă©crits et dâarchives, lâhistoire de la SociĂ©tĂ© de protection des plantes du QuĂ©bec (SPPQ) est retracĂ©e tout au cours de son existence. Son but et ses objectifs sont dĂ©crits ainsi que les moyens employĂ©s pour protĂ©ger les plantes et lutter contre leurs ennemis. Au cours de son existence, la SPPQ a contribuĂ©, par ses congrĂšs annuels et directement par ses membres, Ă faire avancer la lutte aux ennemis des cultures. Ses publications ont aussi menĂ© au dĂ©veloppement dâoutils qui ont aidĂ© Ă mieux connaĂźtre et Ă identifier les insectes, les maladies et les mauvaises herbes qui affectent les cultures et les forĂȘts.With the help of written documents and archives, the history of the QuĂ©bec Society for the Protection of Plants (QSPP) is revealed along with its objectives and the methods used to protect plants from their enemies. Over the last century, the QSPP has contributed, through its annual congresses and more directly through its members, to the development of methods to control plant enemies. Its publications have also helped to develop tools that have led to a better understanding and identification of insects, diseases and weeds affecting plant crops and forests
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