505 research outputs found
Weak-Lensing by Large-Scale Structure and the Polarization Properties of Distant Radio-Sources
We estimate the effects of weak lensing by large-scale density
inhomogeneities and long-wavelength gravitational waves upon the polarization
properties of electromagnetic radiation as it propagates from cosmologically
distant sources. Scalar (density) fluctuations do not rotate neither the plane
of polarization of the electromagnetic radiation nor the source image. They
produce, however, an appreciable shear, which distorts the image shape, leading
to an apparent rotation of the image orientation relative to its plane of
polarization. In sources with large ellipticity the apparent rotation is rather
small, of the order (in radians) of the dimensionless shear. The effect is
larger at smaller source eccentricity. A shear of 1% can induce apparent
rotations of around 5 degrees in radio sources with the smallest eccentricity
among those with a significant degree of integrated linear polarization. We
discuss the possibility that weak lensing by shear with rms value around or
below 5% may be the cause for the dispersion in the direction of integrated
linear polarization of cosmologically distant radio sources away from the
perpendicular to their major axis, as expected from models for their magnetic
fields. A rms shear larger than 5% would be incompatible with the observed
correlation between polarization properties and source orientation in distant
radio galaxies and quasars. Gravity waves do rotate both the plane of
polarization as well as the source image. Their weak lensing effects, however,
are negligible.Comment: 23 pages, 2 eps figures, Aastex 4.0 macros. Final version, as
accepted by ApJ. Additional references and some changes in the introduction
and conclusion
Regulation of the Human Taurine Transporter by Oxidative Stress in Retinal Pigment Epithelial Cells Stably Transformed to Overexpress Aldose Reductase
In diabetes, overexpression of aldose reductase (AR) and consequent glucose-induced impairment of antioxidant defense systems may predispose to oxidative stress and the development of diabetic complications, but the mechanisms are poorly understood. Taurine (2-aminoethanesulfonic acid) functions as an antioxidant, osmolyte, and calcium modulator such that its intracellular depletion could promote cytotoxicity in diabetes. The relationships of oxidative stress and basal AR gene expression to Na+-taurine cotransporter (TT) gene expression, protein abundance, and TT activity were therefore explored in low AR-expressing human retinal pigment epithelial (RPE) 47 cells and RPE 47 cells stably transformed to overexpress AR (RPE 75). Changes in TT gene expression were determined using a 4.6-kb TT promoter-luciferase fusion gene. Compared with RPE 47 cells, in high AR-expressing RPE 75 cells, TT promoter activity was decreased by 46%, which was prevented by an AR inhibitor. TT promoter activity increased up to 900% by prooxidant exposure, which was associated with increased TT peptide abundance and taurine transport. However, induction of TT promoter activity by oxidative stress was attenuated in high AR-expressing cells and partially corrected by AR inhibitor. Finally, exposure of RPE 75 cells to high glucose increased oxidative stress, but down-regulated TT expression. These studies demonstrate for the first time that the TT is regulated by oxidative stress and that overexpression of AR and high glucose impair this response. Abnormal expression of AR may therefore impair antioxidant defense, which may determine tissue susceptibility to chronic diabetic complications. Antioxid. Redox Signal. 7, 1530–1542.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/63284/1/ars.2005.7.1530.pd
The Local Group Census: planetary nebulae in IC 10, Leo A and Sextans A
In the framework of our narrow-band survey of the Local Group galaxies, we
present the results of the search for planetary nebulae (PNe) in the dwarf
irregular galaxies IC10, LeoA and SextansA. Using the standard on-band/off-band
technique, sixteen new candidate PNe have been discovered in the closest
starburst galaxy, IC10. The optical size of this galaxy is estimated to be much
larger than previously thought, considering the location of the new PNe in an
area of 3.6 kpc X 2.7 kpc. We also confirm the results of previous studies for
the other two dwarf irregular galaxies, with the detection of one candidate PN
in LeoA and another one in SextansA. We review the number of planetary nebulae
discovered in the Local Group to date and their behaviour with metallicity. We
suggest a possible fall in the observed number of PNe when [Fe/H]-1.0,
which might indicate that below this point the formation rate of PNe is much
lower than for stellar populations of near Solar abundances. We also find
non-negligible metallicity effects on the [OIII] luminosity of the brightest PN
of a galaxy.Comment: 10 pages, 4 figures, A&A accepte
Impact of introducing an electronic physiological surveillance system on hospital mortality
YesBackground Avoidable hospital mortality is often attributable to inadequate patient vital signs monitoring, and failure to recognise or respond to clinical deterioration. The processes involved with vital sign collection and charting; their integration, interpretation and analysis; and the delivery of decision support regarding subsequent clinical care are subject to potential error and/or failure.
Objective To determine whether introducing an electronic physiological surveillance system (EPSS), specifically designed to improve the collection and clinical use of vital signs data, reduced hospital mortality.
Methods A pragmatic, retrospective, observational study of seasonally adjusted in-hospital mortality rates in three main hospital specialties was undertaken before, during and after the sequential deployment and ongoing use of a hospital-wide EPSS in two large unconnected acute general hospitals in England. The EPSS, which uses wireless handheld computing devices, replaced a paper-based vital sign charting and clinical escalation system.
Results During EPSS implementation, crude mortality fell from a baseline of 7.75% (2168/27 959) to 6.42% (1904/29 676) in one hospital (estimated 397 fewer deaths), and from 7.57% (1648/21 771) to 6.15% (1614/26 241) at the second (estimated 372 fewer deaths). At both hospitals, multiyear statistical process control analyses revealed abrupt and sustained mortality reductions, coincident with the deployment and increasing use of the system. The cumulative total of excess deaths reduced in all specialties with increasing use of the system across the hospital.
Conclusions The use of technology specifically designed to improve the accuracy, reliability and availability of patients’ vital signs and early warning scores, and thereby the recognition of and response to patient deterioration, is associated with reduced mortality in this study
APEX CO(3-2) observations of NGC6822
We observed the CO(3-2) emission of the emission-line regions HubbleI,
HubbleV, HubbleX, Holmberg 18, and the stellar emission-line object S28 in
NGC6822 with the ESO Atacama Pathfinder Experiment (APEX) 12m telescope as part
of its science verification. The very low system temperature of 130-180K
enabled us to achieve detections in 4 single pointings and in a high spatial
resolution 70''x70'' map of HubbleV. We compare the spectra with HI
observations, obtained with the Australia Telescope Compact Array, of the same
regions. In combination with previous multi-line CO observations, we perform a
preliminary investigation of the physical conditions in HubbleV using a simple
LTE model. We estimate the mass of the HubbleV region and the H_2/I_CO(3-2)
conversion factor. Also, we show that HubbleV is located very near the
line-width versus size relation traced by the Milky Way and LMC molecular
clouds.Comment: 4 pages, 3 figures, accepted for publication in the Astronomy &
Astrophysics Letters special issue on the APEX science verificatio
Prediction of the Onset of Disturbed Eating Behavior in Adolescent Girls With Type 1 Diabetes
OBJECTIVE—The purpose of this study was to identify predictors of the onset of disturbed eating behavior (DEB) in adolescent girls with type 1 diabetes
Intraspecific variation in thermal tolerance differs between tropical and temperate fishes
How ectothermic animals will cope with global warming is a critical determinant of the ecological impacts of climate change. There has been extensive study of upper thermal tolerance limits among fish species but how intraspecific variation in tolerance may be affected by habitat characteristics and evolutionary history has not been considered. Intraspecific variation is a primary determinant of species vulnerability to climate change, with implications for global patterns of impacts of ongoing warming. Using published critical thermal maximum (CTmax) data on 203 fish species, we found that intraspecific variation in upper thermal tolerance varies according to a species’ latitude and evolutionary history. Overall, tropical species show a lower intraspecific variation in thermal tolerance than temperate species. Notably, freshwater tropical species have a lower variation in tolerance than freshwater temperate species, which implies increased vulnerability to impacts of thermal stress. The extent of variation in CTmax among fish species has a strong phylogenetic signal, which may indicate a constraint on evolvability to rising temperatures in tropical fishes. That is, in addition to living closer to their upper thermal limits, tropical species may have higher sensitivity and lower adaptability to global warming compared to temperate counterparts. This is evidence that freshwater tropical fish communities, worldwide, are especially vulnerable to ongoing climate change
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