49,967 research outputs found
A Line Survey of Orion KL from 325 to 360 GHz
We present a high-sensitivity spectral line survey of the high-mass star-forming region Orion KL in the 325-360 GHz frequency band. The survey was conducted at the Caltech Submillimeter Observatory on Mauna Kea, Hawaii. The sensitivity achieved is typically 0.1-0.5 K and is limited mostly by the sideband separation method utilized. We find 717 resolvable features consisting of 1004 lines, among which 60 are unidentified. The identified lines are due to 34 species and various isotopomers. Most of the unidentified lines are weak, and many of them most likely due to isotopomers or vibrationally or torsionally excited states of known species with unknown line frequencies, but a few reach the 2-5 K level. No new species have been identified, but we were able to strengthen evidence for the identification of ethanol in Orion and found the first nitrogen sulfide line in this source. The molecule dominating the integrated line emission is SO_2, which emits twice the intensity of CO, followed by SO, which is only slightly stronger than CO. In contrast, the largest number of lines is emitted from heavy organic rotors like HCOOCH_3, CH_3CH_2CN, and CH_3OCH_3, but their contribution to the total flux is unimportant. CH_3OH is also very prominent, both in the number of lines and in integrated flux. An interesting detail of this survey is the first detection of vibrationally excited HCN in the v_2 = 2 state, 2000 K above ground. Clearly this is a glimpse into the very inner part of the Orion hot core
Search for Rapid Changes in the Visible-Light Corona during the 21 June 2001 Total Solar Eclipse
Some 8000 images obtained with the SECIS fast-frame CCD camera instrument
located at Lusaka, Zambia, during the total eclipse of 21 June 2001 have been
analyzed to search for short-period oscillations in intensity that could be a
signature of solar coronal heating mechanisms by MHD wave dissipation. Images
were taken in white- light and Fe XIV green-line (5303 A) channels over 205
seconds (frame rate 39 s-1), approximately the length of eclipse totality at
this location, with a pixel size of four arcseconds square. The data are of
considerably better quality than were obtained during the 11 August 1999 total
eclipse, observed by us (Rudawy et al.: Astron. Astrophys. 416, 1179, 2004), in
that the images are much better exposed and enhancements in the drive system of
the heliostat used gave a much improved image stability. Classical Fourier and
wavelet techniques have been used to analyze the emission at 29518 locations,
of which 10714 had emission at reasonably high levels, searching for periodic
fluctuations with periods in the range 0.1-17 seconds (frequencies 0.06-10 Hz).
While a number of possible periodicities were apparent in the wavelet analysis,
none of the spatially and time-limited periodicities in the local brightness
curves was found to be physically important. This implies that the pervasive
Alfven wave-like phenomena (Tomczyk et al.: Science 317, 1192, 2007) using
polarimetric observations with the CoMP instrument do not give rise to
significant oscillatory intensity fluctuations.Comment: Accepted by Solar Physics; 16 figure
Energy landscape and rigidity
The effects of floppy modes in the thermodynamical properties of a system are
studied. From thermodynamical arguments, we deduce that floppy modes are not at
zero frequency and thus a modified Debye model is used to take into account
this effect. The model predicts a deviation from the Debye law at low
temperatures. Then, the connection between the topography of the energy
landscape, the topology of the phase space and the rigidity of a glass is
explored. As a result, we relate the number of constraints and floppy modes
with the statistics of the landscape. We apply these ideas to a simple model
for which we provide an approximate expression for the number of energy basins
as a function of the rigidity. This allows to understand certains features of
the glass transition, like the jump in the specific heat or the reversible
window observed in chalcogenide glasses.Comment: 1 text+3 eps figure
Stressful life events are associated with low secretion rates of immunoglobulin A in saliva in the middle aged and elderly
Whether chronic stress experience is related to down-regulation of secretory immunoglobulin A (S-IgA) was tested in two substantial cohorts, one middle-aged (N = 640) and one elderly (N = 582), comprising similar numbers of men (N = 556) and women (N = 666) and manual (N = 606) and non-manual (N = 602) workers. Participants indicated from a list of major stressful life events up to six they had experienced in the previous two years. They also rated how disruptive and stressful the events were, at the time and now, as well as their perceived seriousness; the products of these impact values and event frequency were adopted as measures of stress load. From unstimulated 2-minute saliva samples, saliva volume and S-IgA concentration were measured, and S-IgA secretion rate determined as their product. There was a negative association between the stress load measures and S-IgA secretion rate, still evident following adjustment for such variables as smoking and saliva volume. The associations also withstood adjustment for sex, cohort, and household occupational status. Although these associations are small in terms of the amount of variance explained, they nonetheless suggest that chronic stress experience either decreases IgA production by the local plasma cells or reduces the efficiency with which S-IgA is transported from the glandular interstitium into saliva. Given the importance of S-IgA in immune defence at mucosal surfaces and the frequency with which infections are initiated at these surfaces, S-IgA down-regulation could be a means by which chronic stress increases susceptibility to upper respiratory tract infection
Advance care planning in 21st century Australia: a systematic review and appraisal of online advance care directive templates against national framework criteria
Objectives A drive to promote advance care planning at a population level has led to a proliferation of online advance care directive (ACD) templates but little information to guide consumer choice. The current study aimed to appraise the quality of online ACD templates promoted for use in Australia.
Methods A systematic review of online Australian ACD templates was conducted in February 2014. ACD templates were identified via Google searches, and quality was independently appraised by two reviewers against criteria from the 2011 report A National Framework for Advance Care Directives. Bias either towards or against future medical treatment was assessed using criteria designed to limit subjectivity.
Results Fourteen online ACD templates were included, all of which were available only in English. Templates developed by Southern Cross University best met the framework criteria. One ACD template was found to be biased against medical treatment – the Dying with Dignity Victoria Advance Healthcare Directive.
Conclusions More research is needed to understand how online resources can optimally elicit and record consumers’ individual preferences for future care. Future iterations of the framework should address online availability and provide a simple rating system to inform choice and drive quality improvement
A Low Noise Receiver for Submillimeter Astronomy
A broadband, low noise heterodyne receiver, suitable for astronomical use, has been built using a Pb alloy superconducting tunnel junction (SIS). The RF coupling is quasioptical via a bowtie antenna on a quartz lens and is accomplished without any tuning elements. In its preliminary version the double sideband receiver noise temperature rises from 205 K at 116 GHz to 815 K at 466 GHz. This is the most sensitive broadband receiver yet reported for sub-mm wavelengths. Its multi-octave sensitivity and low local oscillator power requirements make this receiver ideal for remote ground observatories or space-borne telescopes such as NASA's Large Deployable Reflector. A version of this receiver is now being built for NASA's Kuiper Airborne Observatory
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Near infrared spectroscopy of W51 IRS-2
Near-infrared spectra at 2.95-3.5 μm and 3.99-10 μm have been obtained towards W51 IRS-2 and its surroundings, in order to investigate the spatial variations in intensity of the 3.28 μm unidentified feature and the 4.05 μm Brackett-α line. The Br-α and 3.28 μm features occupy a broadly similar spatial zone, which is characterised by an unresolved core responsible for most of the emission, and an extended and considerably weaker halo. Grain properties required to excite the 4.28 microns line, the nature of the 3.28 μm emission, and its relation to the source structure are discussed
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