3,063 research outputs found
Systems comparison of direct and relay link data return modes for advanced planetary missions
Advanced planetary missions using direct and relay link data return mode
Cortisol levels and neuropsychiatric diagnosis as markers of postoperative delirium: a prospective cohort study
Polish Ministry of Science and Higher Education, Grant No. 0174/P01/2010/70; 504-06-011
Spitzer spectral line mapping of protostellar outflows: I. Basic data and outflow energetics
We report the results of spectroscopic mapping observations carried out
toward protostellar outflows in the BHR71, L1157, L1448, NGC 2071, and VLA 1623
molecular regions using the Infrared Spectrograph (IRS) of the Spitzer Space
Telescope. These observations, covering the 5.2 - 37 micron spectral region,
provide detailed maps of the 8 lowest pure rotational lines of molecular
hydrogen and of the [SI] 25.25 micron and [FeII] 26.0 micron fine structure
lines. The molecular hydrogen lines, believed to account for a large fraction
of the radiative cooling from warm molecular gas that has been heated by a
non-dissociative shock, allow the energetics of the outflows to be elucidated.
Within the regions mapped towards these 5 outflow sources, total H2
luminosities ranging from 0.02 to 0.75 L(solar) were inferred for the sum of
the 8 lowest pure rotational transitions. By contrast, the much weaker [FeII]
26.0 micron fine structure transition traces faster, dissociative shocks; here,
only a small fraction of the fast shock luminosity emerges as line radiation
that can be detected with Spitzer/IRS.Comment: 38 pages including 17 figures. Accepted for publication in Ap
The Intrinsic Shapes of Molecular Cloud Fragments over a Range of Length Scales
We decipher intrinsic three-dimensional shape distributions of molecular
clouds, cloud cores, Bok globules, and condensations using recently compiled
catalogues of observed axis ratios for these objects mapped in carbon monoxide,
ammonia, through optical selection, or in continuum dust emission. We apply
statistical techniques to compare assumed intrinsic axis ratio distributions
with observed projected axis ratio distributions. Intrinsically triaxial shapes
produce projected distributions which agree with observations. Molecular clouds
mapped in CO are intrinsically triaxial but more nearly prolate than
oblate, while the smaller cloud cores, Bok globules, and condensations are also
intrinsically triaxial but more nearly oblate than prolate.Comment: 12 pages, 11 figures. Version with color figures can be found at
http://www.astro.uwo.ca/~cjones/ or http://www.astro.uwo.ca/~basu/. To appear
in ApJ, 10 April 2002, v. 569, no.
The Dynamical State of Barnard 68: A Thermally Supported, Pulsating Dark Cloud
We report sensitive, high resolution molecular-line observations of the dark
cloud Barnard 68 obtained with the IRAM 30-m telescope. We analyze
spectral-line observations of C18O, CS(2--1), C34S(2--1), and N2H+(1--0) in
order to investigate the kinematics and dynamical state of the cloud. We find
extremely narrow linewidths in the central regions of the cloud. These narrow
lines are consistent with thermally broadened profiles for the measured gas
temperature of 10.5 K. We determine the thermal pressure to be a factor 4 -- 5
times greater than the non-thermal (turbulent) pressure in the central regions
of the cloud, indicating that thermal pressure is the primary source of support
against gravity in this cloud. This confirms the inference of a thermally
supported cloud drawn previously from deep infrared extinction measurements.
The rotational kinetic energy is found to be only a few percent of the
gravitational potential energy, indicating that the contribution of rotation to
the overall stability of the cloud is insignificant. Finally, our observations
show that CS line is optically thick and self-reversed across nearly the entire
projected surface of the cloud. The shapes of the self-reversed profiles are
asymmetric and are found to vary across the cloud in such a manner that the
presence of both inward and outward motions are observed within the cloud.
Moreover, these motions appear to be globally organized in a clear and
systematic alternating spatial pattern which is suggestive of a small
amplitude, non-radial oscillation or pulsation of the outer layers of the cloud
about an equilibrium configuration.Comment: To appear in the Astrophysical Journal; 23 pages, 8 figures;
Manuscript and higher resolution images can be obtained at
http://cfa-www.harvard.edu/~ebergin/pubs_html/b68_vel.htm
On the Identification of High Mass Star Forming Regions using IRAS: Contamination by Low-Mass Protostars
We present the results of a survey of a small sample (14) of low-mass
protostars (L_IR < 10^3 Lsun) for 6.7 GHz methanol maser emission performed
using the ATNF Parkes radio telescope. No new masers were discovered. We find
that the lower luminosity limit for maser emission is near 10^3 Lsun, by
comparison of the sources in our sample with previously detected methanol maser
sources. We examine the IRAS properties of our sample and compare them with
sources previously observed for methanol maser emission, almost all of which
satisfy the Wood & Churchwell criterion for selecting candidate UCHII regions.
We find that about half of our sample satisfy this criterion, and in addition
almost all of this subgroup have integrated fluxes between 25 and 60 microns
that are similar to sources with detectable methanol maser emission. By
identifying a number of low-mass protostars in this work and from the
literature that satisfy the Wood & Churchwell criterion for candidate UCHII
regions, we show conclusively for the first time that the fainter flux end of
their sample is contaminated by lower-mass non-ionizing sources, confirming the
suggestion by van der Walt and Ramesh & Sridharan.Comment: 8 pages with 2 figures. Accepted by Ap
Influence of hand position on the near-effect in 3D attention
Voluntary reorienting of attention in real depth situations is characterized by an attentional bias to locations near the viewer once attention is deployed to a spatially cued object in depth. Previously this effect (initially referred to as the ‘near-effect’) was attributed to access of a 3D viewer-centred spatial representation for guiding attention in 3D space. The aim of this study was to investigate whether the near-bias could have been associated with the position of the response-hand, always near the viewer in previous studies investigating endogenous attentional shifts in real depth. In Experiment 1, the response-hand was placed at either the near or far target depth in a depth cueing task. Placing the response-hand at the far target depth abolished the near-effect, but failed to bias spatial attention to the far location. Experiment 2 showed that the response-hand effect was not modulated by the presence of an additional passive hand, whereas Experiment 3 confirmed that attentional prioritization of the passive hand was not masked by the influence of the responding hand on spatial attention in Experiment 2. The pattern of results is most consistent with the idea that response preparation can modulate spatial attention within a 3D viewer-centred spatial representation
Dune formation on the present Mars
We apply a model for sand dunes to calculate formation of dunes on Mars under
the present Martian atmospheric conditions. We find that different dune shapes
as those imaged by Mars Global Surveyor could have been formed by the action of
sand-moving winds occuring on today's Mars. Our calculations show, however,
that Martian dunes could be only formed due to the higher efficiency of Martian
winds in carrying grains into saltation. The model equations are solved to
study saltation transport under different atmospheric conditions valid for
Mars. We obtain an estimate for the wind speed and migration velocity of
barchan dunes at different places on Mars. From comparison with the shape of
bimodal sand dunes, we find an estimate for the timescale of the changes in
Martian wind regimes.Comment: 16 pages, 12 figure
The relationship of certain word analysis abilities to the reading achievement of first, second, and third grade children,
Thesis (M.A.)--Boston Universit
The Mariner 5 flight path and its determination from tracking data
Mariner 5 flight path and its determination from tracking dat
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