988 research outputs found
The Mid-Infrared Instrument for the James Webb Space Telescope, V: Predicted Performance of the MIRI Coronagraphs
The imaging channel on the Mid-Infrared Instrument (MIRI) is equipped with
four coronagraphs that provide high contrast imaging capabilities for studying
faint point sources and extended emission that would otherwise be overwhelmed
by a bright point-source in its vicinity. Such bright sources might include
stars that are orbited by exoplanets and circumstellar material, mass-loss
envelopes around post-main-sequence stars, the near-nuclear environments in
active galaxies, and the host galaxies of distant quasars. This paper describes
the coronagraphic observing modes of MIRI, as well as performance estimates
based on measurements of the MIRI flight model during cryo-vacuum testing. A
brief outline of coronagraphic operations is also provided. Finally, simulated
MIRI coronagraphic observations of a few astronomical targets are presented for
illustration
Search for positively charged strangelets and other related results with E864 at the AGS
We report on the latest results in the search for positively charged
strangelets from E864's 96/97 run at the AGS with sensitivity of about per central collision. This contribution also contains new results of
a search for highly charged strangelets with . Production of light
nuclei, such as and , is presented as well. Measurements of yields
of these rarely produced isotopes near midrapidity will help constrain the
production levels of strangelets via coalescence. E864 also measures antiproton
production which includes decays from antihyperons. Comparisons with antiproton
yields measured by E878 as a function of centrality indicate a large
antihyperon-to-antiproton ratio in central collisions.Comment: 8 pages, 4 figures; Talk at SQM'98, Padova, Italy (July 20-24th,
1998
High Level of Soluble HLA-G in the Female Genital Tract of Beninese Commercial Sex Workers Is Associated with HIV-1 Infection
Most HIV infections are transmitted across mucosal epithelium. Understanding the role of innate and specific mucosal immunity in susceptibility or protection against HIV infection, as well as the effect of HIV infection on mucosal immunity, are of fundamental importance. HLA-G is a powerful modulator of the immune response. The aim of this study was to investigate whether soluble HLA-G (sHLA-G) expression in the female genital tract is associated with HIV-1 infection.Genital levels of sHLA-G were determined in 52 HIV-1-uninfected and 44 antiretroviral naïve HIV-1-infected female commercial sex workers (CSWs), as well as 71 HIV-1-uninfected non-CSW women at low risk of exposure, recruited in Cotonou, Benin. HIV-1-infected CSWs had higher genital levels of sHLA-G compared with those in both the HIV-1-uninfected CSW (P = 0.009) and non-CSW groups (P = 0.0006). The presence of bacterial vaginosis (P = 0.008), and HLA-G*01:01:02 genotype (P = 0.002) were associated with higher genital levels of sHLA-G in the HIV-1-infected CSWs, whereas the HLA-G*01:04:04 genotype was also associated with higher genital level of sHLA-G in the overall population (P = 0.038). When adjustment was made for all significant variables, the increased expression of sHLA-G in the genital mucosa remained significantly associated with both HIV-1 infection (P = 0.02) and bacterial vaginosis (P = 0.03).This study demonstrates that high level of sHLA-G in the genital mucosa is independently associated with both HIV-1 infection and bacterial vaginosis
Antideuteron yield at the AGS and coalescence implications
We present Experiment 864's measurement of invariant antideuteron yields in
11.5A GeV/c Au + Pt collisions. The analysis includes 250 million triggers
representing 14 billion 10% central interactions sampled for events with high
mass candidates. We find (1/2 pi pt) d^(2)N/dydpt = 3.5 +/- 1.5 (stat.)
+0.9,-0.5 (sys.) x 10^(-8) GeV^(-2)c^(2) for 1.8=0.35 GeV/c
(y(cm)=1.6) and 3.7 +/- 2.7 (stat.) +1.4,-1.5 (sys.) x 10^(-8) GeV^(-2)c^(2)
for 1.4=0.26 GeV/c, and a coalescence parameter B2-bar of 4.1 +/-
2.9 (stat.) +2.3,-2.4 (sys.) x 10^(-3) GeV^(2)c^(-3). Implications for the
coalescence model and antimatter annihilation are discussed.Comment: 8 pages, 4 figures, Latex, submitted to Phys. Rev. Let
JWST/MIRI Data Reduction and Products
The Mid-Infrared Instrument (MIRI) is one of four science instruments to be flown aboard the James Webb Space Telescope (JWST). MIRI operates from 5 to 28.5 microns and provides a suite of versatile capabilities including imaging, low-resolution spectroscopy (LRS), medium-resolution spectroscopy (MRS) via an integral field unit, and coronagraphy. The MIRI pipeline consists of three stages: 1) Raw to Slope Images, 2) Calibrated Slope Images, and 3) Multiple Exposures Combined. The pipeline is designed to provide well-calibrated, high level data products that maximize the scientific return from the instrument
JWST/MIRI coronagraphic performances as measured on-sky
Characterization of directly imaged exoplanets is one of the most eagerly
anticipated science functions of the James Webb Space Telescope. MIRI, the
mid-IR instrument has the capability to provide unique spatially resolved
photometric data points in a spectral range never achieved so far for such
objects. We aim to present the very first on-sky contrast measurements of the
MIRI's coronagraphs. In addition to a classical Lyot coronagraph at the longest
wavelength, this observing mode implements the concept of the four quadrant
phase mask for the very first time in a space telescope. We observed single
stars together with a series of reference stars to measure raw contrasts as
they are delivered on the detector, as well as reference subtracted contrasts.
MIRI's coronagraphs achieve raw contrasts greater than at the smallest
angular separations (within ) and about further out (beyond
). Subtracting the residual diffracted light left unattenuated by the
coronagraph has the potential to bring the final contrast down to the
background and detector limited noise floor at most angular separations (a few
times at less than ). MIRI coronagraphs behave as expected from
simulations. In particular the raw contrasts for all four coronagraphs are
fully consistent with the diffractive model. Contrasts obtained with
subtracting reference stars also meet expectations and are fully demonstrated
for two four quadrant phase masks (F1065C and F1140C). The worst contrast,
measured at F1550C, is very likely due to a variation of the phase aberrations
at the primary mirror during the observations, and not an issue of the
coronagraph itself. We did not perform reference star subtraction with the Lyot
mask at F2300C, but we anticipate that it would bring the contrast down to the
noise floor.Comment: submitted to A&
Differences in the signaling pathways of α1A- and α1B-adrenoceptors are related to different endosomal targeting
Aims: To compare the constitutive and agonist-dependent endosomal trafficking of α1A- and α1B-adrenoceptors (ARs) and to establish if the internalization pattern determines the signaling pathways of each subtype.
Methods: Using CypHer5 technology and VSV-G epitope tagged α1A- and α1B-ARs stably and transiently expressed in HEK 293 cells, we analyzed by confocal microscopy the constitutive and agonist-induced internalization of each subtype, and the temporal relationship between agonist induced internalization and the increase in intracellular calcium (determined by FLUO-3 flouorescence), or the phosphorylation of ERK1/2 and p38 MAP kinases (determined by Western blot).
Results and Conclusions: Constitutive as well as agonist-induced trafficking of α1A and α1B ARs maintain two different endosomal pools of receptors: one located close to the plasma membrane and the other deeper into the cytosol. Each subtype exhibited specific characteristics of internalization and distribution between these pools that determines their signaling pathways: α1A-ARs, when located in the plasma membrane, signal through calcium and ERK1/2 pathways but, when translocated to deeper endosomes, through a mechanism sensitive to β-arrestin and concanavalin A, continue signaling through ERK1/2 and also activate the p38 pathway. α1B-ARs signal through calcium and ERK1/2 only when located in the membrane and the signals disappear after endocytosis and by disruption of the membrane lipid rafts by methyl-β-cyclodextrin
N-body simulations of gravitational dynamics
We describe the astrophysical and numerical basis of N-body simulations, both
of collisional stellar systems (dense star clusters and galactic centres) and
collisionless stellar dynamics (galaxies and large-scale structure). We explain
and discuss the state-of-the-art algorithms used for these quite different
regimes, attempt to give a fair critique, and point out possible directions of
future improvement and development. We briefly touch upon the history of N-body
simulations and their most important results.Comment: invited review (28 pages), to appear in European Physics Journal Plu
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