3,946 research outputs found
Discovery of a Binary Centaur
We have identified a binary companion to (42355) 2002 CR46 in our ongoing
deep survey using the Hubble Space Telescope's High Resolution Camera. It is
the first companion to be found around an object in a non-resonant orbit that
crosses the orbits of giant planets. Objects in orbits of this kind, the
Centaurs, have experienced repeated strong scattering with one or more giant
planets and therefore the survival of binaries in this transient population has
been in question. Monte Carlo simulations suggest, however, that binaries in
(42355) 2002 CR46 -like heliocentric orbits have a high probability of survival
for reasonable estimates of the binary's still-unknown system mass and
separation. Because Centaurs are thought to be precursors to short period
comets, the question of the existence of binary comets naturally arises; none
has yet been definitively identified. The discovery of one binary in a sample
of eight observed by HST suggests that binaries in this population may not be
uncommon.Comment: 20 pages, 4 figures, 1 table accepted for publication in Icaru
Why Hot Water Pipes in Household Plumbing Burst More Frequently Than Cold Water Pipes
Plumbers often notice that the hot water pipes in a plumbing system that lead to the bathroom or kitchen burst more frequently than the pipes carrying cold water. It is said that the ratio is at least four to one. The Cold Water usually freezes so as to lessen the flow of water in the pipes, or to stop the flow altogether, but the freezing seldom bursts the pipes unless the temperature is very low
Molecfit: A general tool for telluric absorption correction II. Quantitative evaluation on ESO-VLT X-Shooter spectra
Context: Absorption by molecules in the Earth's atmosphere strongly affects
ground-based astronomical observations. The resulting absorption line strength
and shape depend on the highly variable physical state of the atmosphere, i.e.
pressure, temperature, and mixing ratio of the different molecules involved.
Usually, supplementary observations of so-called telluric standard stars (TSS)
are needed to correct for this effect, which is expensive in terms of telescope
time. We have developed the software package molecfit to provide synthetic
transmission spectra based on parameters obtained by fitting narrow ranges of
the observed spectra of scientific objects. These spectra are calculated by
means of the radiative transfer code LBLRTM and an atmospheric model. In this
way, the telluric absorption correction for suitable objects can be performed
without any additional calibration observations of TSS. Aims: We evaluate the
quality of the telluric absorption correction using molecfit with a set of
archival ESO-VLT X-Shooter visible and near-infrared spectra. Methods: Thanks
to the wavelength coverage from the U to the K band, X-Shooter is well suited
to investigate the quality of the telluric absorption correction with respect
to the observing conditions, the instrumental set-up, input parameters of the
code, the signal-to-noise of the input spectrum, and the atmospheric profiles.
These investigations are based on two figures of merit, I_off and I_res, that
describe the systematic offsets and the remaining small-scale residuals of the
corrections. We also compare the quality of the telluric absorption correction
achieved with moelcfit to the classical method based on a telluric standard
star. (Abridged)Comment: Acc. by A&A; Software available via ESO:
http://www.eso.org/sci/software/pipelines/skytools
Spontanous periodic breathing is associated with sympathetic hyperreactivity and baroreceptor dysfunction in hypertension
OBJECTIVES: Intermittent periods of hypoxemia such as during periodic breathing are associated with hypertension and increased sympathetic activity. In patients with sleep apnea syndrome, hypertension is common. Treating apnea improves hypertension and reduces sympathetic outflow. The aim of the present study was to investigate the phenomenon and mechanisms of spontaneous periodic breathing in patients with hypertension. METHOD: We examined 43 hypertensive patients with untreated hypertension without left-ventricular dysfunction, heart failure or sleep apnea syndrome. Muscle sympathetic nerve activity (MSA), heart rate (HR), blood pressure (BP) and respiration were continuously recorded at rest and during cold-pressor testing. Oxygen and a CO2-enriched gas were used to test central and peripheral chemoreceptors, respectively. Baroreceptor gain was measured using the alpha method. RESULTS: Seven out of 43 patients showed spontaneous periodic breathing while awake. No difference in MSA, HR and BP was seen between patients with and without periodic breathing at rest except the breathing pattern. However, the cold-pressor test caused a larger increase of MSA in patients with periodic breathing (203 +/- 62 vs. 62 +/- 8%, P < 0.0001 by ANOVA), as well as systolic (46 +/- 6 vs. 25 +/- 3 mmHg, P = 0.002) and diastolic BP (26 +/- 5 vs. 12 +/- 1 mmHg, P = 0.004, ANOVA). Baroreceptor gain was markedly higher in patients with periodic breathing. Chemoreceptor sensitivity was comparable. CONCLUSION: Spontaneous periodic breathing is relatively common in patients with hypertension and is associated with greatly enhanced responses to cold-pressor testing. We suggest increased baroreceptor gain and sympathetic outflow as a cause for the oscillatory respiration pattern via barorespiratory coupling
Images in cardiovascular medicine. The blue man: amiodarone-induced skin discoloration
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Passive incentive requirements: a regional assessment
The nation's goal of 20% solar contribution by the turn of the century will be achieved, in part, by the construction of residences heated by virtue of their passive solar designs. These designs are not economically competitive against all conventional fuels in all locations. Some degree of government incentive will be required to assure a competitive position for these designs. A methodology is presented which is used to assess the magnitude of the government incentive required to assure feasibility. The methodology is used to provide a regional assessment for the Pacific Northwest under alternative home ownership periods and conventional fuel types
Evidence for Two Populations of Classical Transneptunian Objects: The Strong Inclination Dependence of Classical Binaries
We have searched 101 Classical transneptunian objects for companions with the
Hubble Space Telescope. Of these, at least 21 are binary. The heliocentric
inclinations of the objects we observed range from 0.6-34 degrees. We find a
very strong anticorrelation of binaries with inclination. Of the 58 targets
that have inclinations of less than 5.5 degrees, 17 are binary, a binary
fraction of 29 +7/-6%. All 17 are similar-brightness systems. On the contrary,
only 4 of the 42 objects with inclinations greater than 5.5 degrees have
satellites and only 1 of these is a similar-brightness binary. This striking
dichotomy appears to agree with other indications that the low eccentricity,
non-resonant Classical transneptunian objects include two overlapping
populations with significantly different physical properties and dynamical
histories.Comment: 32 pages, 4 figures, 2 tables in press for Icarus volume 194 Note
added in proof and reference updates in this corrected versio
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