603 research outputs found
Strong Water Absorption in the Dayside Emission Spectrum of the Planet HD 189733b
Recent observations of the extrasolar planet HD 189733b did not reveal the
presence of water in the emission spectrum of the planet. Yet models of such
'Hot Jupiter' planets predict an abundance of atmospheric water vapour.
Validating and constraining these models is crucial for understanding the
physics and chemistry of planetary atmospheres in extreme environments.
Indications of the presence of water in the atmosphere of HD 189733b have
recently been found in transmission spectra, where the planet's atmosphere
selectively absorbs the light of the parent star, and in broadband photometry.
Here we report on the detection of strong water absorption in a high
signal-to-noise, mid-infrared emission spectrum of the planet itself. We find
both a strong downturn in the flux ratio below 10 microns and discrete spectral
features that are characteristic of strong absorption by water vapour. The
differences between these and previous observations are significant and admit
the possibility that predicted planetary-scale dynamical weather structures
might alter the emission spectrum over time. Models that match the observed
spectrum and the broadband photometry suggest that heat distribution from the
dayside to the night side is weak. Reconciling this with the high night side
temperature will require a better understanding of atmospheric circulation or
possible additional energy sources.Comment: 11 pages, 1 figure, published in Natur
From Molecular Cores to Planet-forming Disks with SIRTF
The SIRTF mission and the Legacy programs will provide coherent data bases
for extra-galactic and Galactic science that will rapidly become available to
researchers through a public archive. The capabilities of SIRTF and the six
legacy programs are described briefly. Then the cores to disks (c2d) program is
described in more detail. The c2d program will use all three SIRTF instruments
(IRAC, MIPS, and IRS) to observe sources from molecular cores to protoplanetary
disks, with a wide range of cloud masses, stellar masses, and star-forming
environments. The SIRTF data will stimulate many follow-up studies, both with
SIRTF and with other instruments.Comment: 6 pages, from Fourth Cologne-Bonn-Zermatt-Symposium, The Dense
Interstellar Matter in Galaxie
Chronic voluntary alcohol consumption causes persistent cognitive deficits and cortical cell loss in a rodent model
Chronic alcohol use is associated with cognitive decline that impedes behavioral change during rehabilitation. Despite this, addiction therapy does not address cognitive deficits, and there is poor understanding regarding the mechanisms that underlie this decline. We established a rodent model of chronic voluntary alcohol use to measure ensuing cognitive effects and underlying pathology. Rats had intermittent access to alcohol or an isocaloric solution in their home cage under voluntary 2-bottle choice conditions. In Experiments 1 and 2 cognition was assessed using operant touchscreen chambers. We examined performance in a visual discrimination and reversal task (Experiment 1), and a 5-choice serial reaction time task (Experiment 2). For Experiment 3, rats were perfused immediately after cessation of alcohol access period, and volume, cell density and microglial populations were assessed in the prefrontal cortex and striatum. Volume was assessed using the Cavalieri probe, while cell and microglial counts were estimated using unbiased stereology with an optical fractionator. Alcohol-exposed and control rats showed comparable acquisition of pairwise discrimination; however, performance was impaired when contingencies were reversed indicating reduced behavioral flexibility. When tested in a 5-choice serial reaction time task alcohol-exposed rats showed increased compulsivity and increased attentional bias towards a reward associated cue. Consistent with these changes, we observed decreased cell density in the prefrontal cortex. These findings confirm a detrimental effect of chronic alcohol and establish a model of alcohol-induced cognitive decline following long-term voluntary intake that may be used for future intervention studies
Physics of Neutron Star Kicks
It is no longer necessary to `sell' the idea of pulsar kicks, the notion that
neutron stars receive a large velocity (a few hundred to a thousand km
s) at birth. However, the origin of the kicks remains mysterious. We
review the physics of different kick mechanisms, including hydrodynamically
driven, neutrino and magnetically driven kicks.Comment: 8 pages including 1 figure. To be published in "Stellar Astrophysics"
(Pacific Rim Conference Proceedings), (Kluwer Pub.
Ecological and methodological drivers of species' distribution and phenology responses to climate change
Climate change is shifting species’ distribution and phenology. Ecological traits, such as mobility or reproductive mode, explain variation in observed rates of shift for some taxa. However, estimates of relationships between traits and climate responses could be influenced by how responses are measured. We compiled a global data set of 651 published marine species’ responses to climate change, from 47 papers on distribution shifts and 32 papers on phenology change. We assessed the relative importance of two classes of predictors of the rate of change, ecological traits of the responding taxa and methodological approaches for quantifying biological responses. Methodological differences explained 22% of the variation in range shifts, more than the 7.8% of the variation explained by ecological traits. For phenology change, methodological approaches accounted for 4% of the variation in measurements, whereas 8% of the variation was explained by ecological traits. Our ability to predict responses from traits was hindered by poor representation of species from the tropics, where temperature isotherms are moving most rapidly. Thus, the mean rate of distribution change may be underestimated by this and other global syntheses. Our analyses indicate that methodological approaches should be explicitly considered when designing, analysing and comparing results among studies. To improve climate impact studies, we recommend that (1) reanalyses of existing time series state how the existing data sets may limit the inferences about possible climate responses; (2) qualitative comparisons of species’ responses across different studies be limited to studies with similar methodological approaches; (3) meta-analyses of climate responses include methodological attributes as covariates; and (4) that new time series be designed to include the detection of early warnings of change or ecologically relevant change. Greater consideration of methodological attributes will improve the accuracy of analyses that seek to quantify the role of climate change in species’ distribution and phenology changes
Two cases of occupational allergic contact dermatitis from a cycloaliphatic epoxy resin in a neat oil: Case Report
BACKGROUND: Metal-working fluids contain complex mixtures of chemicals and metal workers constitute a potential risk group for the development of allergic contact dermatitis. CASE PRESENTATION: Two metal workers developed allergic contact dermatitis on the hands and lower arms from exposure to a neat oil used in metal processing. Patch testing revealed that the relevant contact allergen was a cycloaliphatic epoxy resin, 1,2-cyclohexanedicarboxylic acid, bis(oxiranylmethyl) ester, added to the oil as a stabilizer. None of the patients had positive reactions to the bisphenol A-based epoxy resin in the standard series. CONCLUSIONS: These cases emphasize that well-known contact allergens may show up from unexpected sources of exposure. Further, it can be a long-lasting, laborious process to detect an occupational contact allergen and cooperation from the patient and the manufacturer of the sensitizing product is essential
Probing the close environment of young stellar objects with interferometry
The study of Young Stellar Objects (YSOs) is one of the most exciting topics
that can be undertaken by long baseline optical interferometry. The magnitudes
of these objects are at the edge of capabilities of current optical
interferometers, limiting the studies to a few dozen, but are well within the
capability of coming large aperture interferometers like the VLT
Interferometer, the Keck Interferometer, the Large Binocular Telescope or
'OHANA. The milli-arcsecond spatial resolution reached by interferometry probes
the very close environment of young stars, down to a tenth of an astronomical
unit. In this paper, I review the different aspects of star formation that can
be tackled by interferometry: circumstellar disks, multiplicity, jets. I
present recent observations performed with operational infrared
interferometers, IOTA, PTI and ISI, and I show why in the next future one will
extend these studies with large aperture interferometers.Comment: Review to be published in JENAM'2002 proceedings "The Very Large
Telescope Interferometer Challenges for the future
Evolution in the Cluster Early-type Galaxy Size-Surface Brightness Relation at z =~ 1
We investigate the evolution in the distribution of surface brightness, as a
function of size, for elliptical and S0 galaxies in the two clusters RDCS
J1252.9-2927, z=1.237 and RX J0152.7-1357, z=0.837. We use multi-color imaging
with the Advanced Camera for Surveys on the Hubble Space Telescope to determine
these sizes and surface brightnesses. Using three different estimates of the
surface brightnesses, we find that we reliably estimate the surface brightness
for the galaxies in our sample with a scatter of < 0.2 mag and with systematic
shifts of \lesssim 0.05 mag. We construct samples of galaxies with early-type
morphologies in both clusters. For each cluster, we use a magnitude limit in a
band which closely corresponds to the rest-frame B, to magnitude limit of M_B =
-18.8 at z=0, and select only those galaxies within the color-magnitude
sequence of the cluster or by using our spectroscopic redshifts. We measure
evolution in the rest-frame B surface brightness, and find -1.41 \+/- 0.14 mag
from the Coma cluster of galaxies for RDCS J1252.9-2927 and -0.90 \+/- 0.12 mag
of evolution for RX J0152.7-1357, or an average evolution of (-1.13 \+/- 0.15)
z mag. Our statistical errors are dominated by the observed scatter in the
size-surface brightness relation, sigma = 0.42 \+/- 0.05 mag for RX
J0152.7-1357 and sigma = 0.76 \+/- 0.10 mag for RDCS J1252.9-2927. We find no
statistically significant evolution in this scatter, though an increase in the
scatter could be expected. Overall, the pace of luminosity evolution we measure
agrees with that of the Fundamental Plane of early-type galaxies, implying that
the majority of massive early-type galaxies observed at z =~ 1 formed at high
redshifts.Comment: Accepted in ApJ, 16 pages in emulateapj format with 15 eps figures, 6
in colo
Strengthening confidence in climate change impact science
Aim: To assess confidence in conclusions about climate-driven biological change through time, and identify approaches for strengthening confidence scientific conclusions about ecological impacts of climate change. Location: Global. Methods: We outlined a framework for strengthening confidence in inferences drawn from biological climate impact studies through the systematic integration of prior expectations, long-term data and quantitative statistical procedures. We then developed a numerical confidence index (Cindex) and used it to evaluate current practices in 208 studies of marine climate impacts comprising 1735 biological time series. Results: Confidence scores for inferred climate impacts varied widely from 1 to 16 (very low to high confidence). Approximately 35% of analyses were not associated with clearly stated prior expectations and 65% of analyses did not test putative non-climate drivers of biological change. Among the highest-scoring studies, 91% tested prior expectations, 86% formulated expectations for alternative drivers but only 63% statistically tested them. Higher confidence scores observed in studies that did not detect a change or tracked multiple species suggest publication bias favouring impact studies that are consistent with climate change. The number of time series showing climate impacts was a poor predictor of average confidence scores for a given group, reinforcing that vote-counting methodology is not appropriate for determining overall confidence in inferences. Main conclusions: Climate impacts research is expected to attribute biological change to climate change with measurable confidence. Studies with long-term, high-resolution data, appropriate statistics and tests of alternative drivers earn higher Cindex scores, suggesting these should be given greater weight in impact assessments. Together with our proposed framework, the results of our Cindex analysis indicate how the science of detecting and attributing biological impacts to climate change can be strengthened through the use of evidence-based prior expectations and thorough statistical analyses, even when data are limited, maximizing the impact of the diverse and growing climate change ecology literature
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