685 research outputs found
Variation of the Diameter of the Sun as Measured by the Solar Disk Sextant (SDS)
The balloon-borne Solar Disk Sextant (SDS) experiment has measured the
angular size of the Sun on seven occasions spanning the years 1992 to 2011. The
solar half-diameter -- observed in a 100-nm wide passband centred at 615 nm --
is found to vary over that period by up to 200 mas, while the typical estimated
uncertainty of each measure is 20 mas. The diameter variation is not in phase
with the solar activity cycle; thus, the measured diameter variation cannot be
explained as an observational artefact of surface activity. Other possible
instrument-related explanations for the observed variation are considered but
found unlikely, leading us to conclude that the variation is real. The SDS is
described here in detail, as is the complete analysis procedure necessary to
calibrate the instrument and allow comparison of diameter measures across
decades.Comment: 41 pages; appendix and 2 figures added plus some changes in text
based on referee's comments; to appear in MNRA
Interstellar Krypton Abundances: The Detection of Kiloparsec-scale Differences in Galactic Nucleosynthetic History
We present an analysis of Kr I 1236 line measurements from 50 sight lines in
the Hubble Space Telescope Space Telescope Imaging Spectrograph and Goddard
High Resolution Spectrograph data archives that have sufficiently high
resolution and signal-to-noise ratio to permit reliable krypton-to-hydrogen
abundance ratio determinations. The distribution of Kr/H ratios in this sample
is consistent with a single value for the ISM within 5900 pc of the Sun,
log(Kr/H) = -9.02+/-0.02, apart from a rough annulus from between about 600 and
2500 pc distant. The Kr/H ratio toward stars within this annulus is elevated by
approximately 0.11 dex, similar to previously noted elevations of O/H and Cu/H
gas-phase abundances beyond about 800 pc. A significant drop in the gas-phase
N/O ratio in the same region suggests that this is an artifact of
nucleosynthetic history. Since the physical scale of the annulus' inner edge is
comparable to the radius of the Gould Belt and the outer limit of heliocentric
distances where the D/H abundance ratio is highly variable, these phenomena may
be related to the Gould Belt's origins.Comment: 32 pages, including 6 figures; accepted by Ap
The Homogeneity of Interstellar Oxygen in the Galactic Disk
We present an analysis of high resolution HST Space Telescope Imaging
Spectrograph (STIS) observations of O I 1356 and H I Lyman-alpha absorption in
36 sight lines that probe a variety of Galactic disk environments and include
paths that range over nearly 4 orders of magnitude in f(H_2), over 2 orders of
magnitude in mean sight line density, and that extend up to 6.5 kpc in length.
Consequently, we have undertaken the study of gas-phase O/H abundance ratio
homogeneity using the current sample and previously published Goddard
High-Resolution Spectrograph (GHRS) results. Two distinct trends are identified
in the 56 sight line sample: an apparent decrease in gas-phase oxygen abundance
with increasing mean sight line density and a gap between the mean O/H ratio
for sight lines shorter and longer than about 800 pc. The first effect is a
smooth transition between two depletion levels associated with large mean
density intervals; it is centered near a density of 1.5 cm^-3 and is similar to
trends evident in gas-phase abundances of other elements. Paths less dense than
the central value exhibit a mean O/H ratio of log_10 (O/H) = -3.41+/-0.01 (or
390+/-10 ppm), which is consistent with averages determined for several long,
low-density paths observed by STIS (Andre et al. 2003) and short low-density
paths observed by FUSE (Moos et al. 2002). Sight lines of higher mean density
exhibit an average O/H value of log_10 (O/H) = -3.55+/-0.02 (284+/-12 ppm). The
datapoints for low-density paths are scattered more widely than those for
denser sight lines, due to O/H ratios for paths shorter than 800 pc that are
generally about 0.10 dex lower than the values for longer ones.Comment: 33 pages, including 8 figures and 4 tables; accepted for publication
in ApJ, tentatively in Oct 200
Galactic Abundances: Report of Working Group 3
We summarize the various methods and their limitations and strengths to derive galactic abundances from in-situ and remote-sensing measurements, both from ground-based observations and from instruments in space. Because galactic abundances evolve in time and space it is important to obtain information with a variety of different methods covering different regions from the Very Local Insterstellar Medium (VLISM) to the distant galaxy, and different times throughout the evolution of the galaxy. We discuss the study of the present-day VLISM with neutral gas, pickup ions, and Anomalous Cosmic Rays, the study of the local interstellar medium (ISM) at distances <1.5 kpc utilizing absorption line measurements in H I clouds, and the study of galactic cosmic rays, sampling contemporary (~15 Myr) sources in the local ISM within a few kiloparsec of the solar system. Solar system abundances, derived from solar abundances and meteorite studies are discussed in several other chapters of this volume. They provide samples of matter from the ISM from the time of solar system format ion, about 4.5 Gyr ago. The evolution of galactic abundances on longer time scales is discussed in the context of nuclear synthesis in the various contributing stellar objects
Surface modification of pig endothelial cells with a branched heparin conjugate improves their compatibility with human blood
Corline Heparin Conjugate (CHC), a compound of multiple unfractionated heparin chains, coats cells with a glycocalyx-like layer and may inhibit (xeno) transplant-associated activation of the plasma cascade systems. Here, we investigated the use of CHC to protect WT and genetically modified (GTKO. hCD46. hTBM) pig aortic endothelial cells (PAEC) in two pig-to-human in vitro xenotransplantation settings. Model 1: incubation of untreated or hTNFa-treated PAEC with 10% human plasma induced complement C3b/c and C5b-9 deposition, cellular activation and coagulation activation in WT and GTKO. hCD46. hTBM PAEC. Coating of untreated or hTNFa-treated PAEC with CHC (100 mu g/ml) protected against human plasma-induced endothelial activation and damage. Model 2: PAEC were grown on microcarrier beads, coated with CHC, and incubated with non-anticoagulated whole human blood. Genetically modified PAEC significantly prolonged clotting time of human blood (115.0 +/- 16.1 min, p < 0.001) compared to WT PAEC (34.0 +/- 8.2 min). Surface CHC significantly improved the human blood compatibility of PAEC, as shown by increased clotting time (WT: 84.3 +/- 11.3 min, p < 0.001;GTKO. hCD46. hTBM: 146.2 +/- 20.4 min, p < 0.05) and reduced platelet adhesion, complement activation, coagulation activation and inhibition of fibrinolysis. The combination of CHC coating and genetic modification provided the greatest compatibility with human blood, suggesting that pre-transplant perfusion of genetically modified porcine organs with CHC may benefit post-transplant xenograft function
The Gaia-ESO survey: Radial metallicity gradients and age-metallicity relation of stars in the milky way disk
We study the relationship between age, metallicity, and α-enhancement of FGK stars in the Galactic disk. The results are based upon the analysis of high-resolution UVES spectra from the Gaia-ESO large stellar survey. We explore the limitations of the ob
Primary vs. Secondary Antibody Deficiency: Clinical Features and Infection Outcomes of Immunoglobulin Replacement
<div><p>Secondary antibody deficiency can occur as a result of haematological malignancies or certain medications, but not much is known about the clinical and immunological features of this group of patients as a whole. Here we describe a cohort of 167 patients with primary or secondary antibody deficiencies on immunoglobulin (Ig)-replacement treatment. The demographics, causes of immunodeficiency, diagnostic delay, clinical and laboratory features, and infection frequency were analysed retrospectively. Chemotherapy for B cell lymphoma and the use of Rituximab, corticosteroids or immunosuppressive medications were the most common causes of secondary antibody deficiency in this cohort. There was no difference in diagnostic delay or bronchiectasis between primary and secondary antibody deficiency patients, and both groups experienced disorders associated with immune dysregulation. Secondary antibody deficiency patients had similar baseline levels of serum IgG, but higher IgM and IgA, and a higher frequency of switched memory B cells than primary antibody deficiency patients. Serious and non-serious infections before and after Ig-replacement were also compared in both groups. Although secondary antibody deficiency patients had more serious infections before initiation of Ig-replacement, treatment resulted in a significant reduction of serious and non-serious infections in both primary and secondary antibody deficiency patients. Patients with secondary antibody deficiency experience similar delays in diagnosis as primary antibody deficiency patients and can also benefit from immunoglobulin-replacement treatment.</p></div
Search for coherent charged pion production in neutrino-carbon interactions
We report the result from a search for charged-current coherent pion
production induced by muon neutrinos with a mean energy of 1.3 GeV. The data
are collected with a fully active scintillator detector in the K2K
long-baseline neutrino oscillation experiment. No evidence for coherent pion
production is observed and an upper limit of is set on
the cross section ratio of coherent pion production to the total
charged-current interaction at 90% confidence level. This is the first
experimental limit for coherent charged pion production in the energy region of
a few GeV.Comment: 5 pages, 4 figure
Evidence for muon neutrino oscillation in an accelerator-based experiment
We present results for muon neutrino oscillation in the KEK to Kamioka (K2K)
long-baseline neutrino oscillation experiment. K2K uses an accelerator-produced
muon neutrino beam with a mean energy of 1.3 GeV directed at the
Super-Kamiokande detector. We observed the energy dependent disappearance of
muon neutrino, which we presume have oscillated to tau neutrino. The
probability that we would observe these results if there is no neutrino
oscillation is 0.0050% (4.0 sigma).Comment: 5 pages, 4 figure
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