11,676 research outputs found
APEX/SABOCA observations of small-scale structure of infrared-dark clouds I. Early evolutionary stages of star-forming cores
Infrared-dark clouds (IRDCs) harbor the early phases of cluster and high-mass
star formation and are comprised of cold (~20 K), dense (n > 10 cm)
gas. The spectral energy distribution (SED) of IRDCs is dominated by the
far-infrared and millimeter wavelength regime, and our initial Herschel study
examined IRDCs at the peak of the SED with high angular resolution. Here we
present a follow-up study using the SABOCA instrument on APEX which delivers
7.8" angular resolution at 350 micron, matching the resolution we achieved with
Herschel/PACS, and allowing us to characterize substructure on ~0.1pc scales.
Our sample of 11 nearby IRDCs are a mix of filamentary and clumpy morphologies,
and the filamentary clouds show significant hierarchical structure, while the
clumpy IRDCs exhibit little hierarchical structure. All IRDCs, regardless of
morphology, have about 14% of their total mass in small scale core-like
structures which roughly follow a trend of constant volume density over all
size scales. Out of the 89 protostellar cores we identified in this sample with
Herschel, we recover 40 of the brightest and re-fit their SEDs and find their
properties agree fairly well with our previous estimates ( ~ 19K). We detect
a new population of "cold cores" which have no 70 micron counterpart, but are
100 and 160 micron-bright, with colder temperatures ( ~ 16K). This latter
population, along with SABOCA-only detections, are predominantly low-mass
objects, but their evolutionary diagnostics are consistent with the earliest
starless or prestellar phase of cores in IRDCs.Comment: accepted to A&A. 28 pages, 27 figures. For full-resolution image
gallery, see http://www.mpia.de/~ragan/saboca.html (v2 includes only minor
typographical corrections, changed to agree with published version
Growth and sensory characteristics of alternative genotype broilers reared in organic orchards
The effects of age, sex and genotype on growth and sensory characteristics in organically produced broilers, when kept considerably longer before slaughtering, were examined. A total of 450 birds consisting of three genotypes, Light Sussex, New Hampshire, and the commercial strain I 657 were inserted at Fejoe Research Orchard. Half the birds were slaughtered at 91 days of age and half at 120 days of age. I 657 was significantly heavier compared to the slower growing breeds and Light Sussex was significantly heavier than New Hampshire. Males were significantly heavier than females across genotype, but weight ratios differed with genotype. No overall effect of genotype was found on the flavour or smell of the breast meat, but the commercial strain went towards a tougher and less tender consistency at 120 days of age, whereas the opposite was the case for the slower growing pure breeds. The positive flavour of salt was significantly improved at 120 days of age across genotype and age, with females having saltier flavour than the males. The positive flavour of sweet corn was improved in the meat from the males, but the positive smell of sweet corn was significantly improved in both males and females. No negative consequences of age were found
Space Station Freedom technology payload user operations facility concept
This report presents a concept for a User Operations Facility (UOF) for payloads sponsored by the NASA Office of Aeronautics and Space Technology (OAST). The UOF can be located at any OAST sponsored center; however, for planning purposes, it is assumed that the center will be located at Langley Research Center (LaRC)
Parallax measurements of cool brown dwarfs
Accurate parallax measurements allow us to determine physical properties of
brown dwarfs, and help us to constrain evolutionary and atmospheric models,
break the age-mass degeneracy and reveal unresolved binaries.
We measured absolute trigonometric parallaxes and proper motions of 6 cool
brown dwarfs using background galaxies to establish an absolute reference
frame. We derive the absolute J-mag. The six T brown dwarfs in our sample have
spectral types between T2.5 and T7.5 and magnitudes in J between 13.9 and 18.0,
with photometric distances below 25 pc.
The observations were taken in the J-band with the Omega-2000 camera on the
3.5 m telescope at Calar Alto, during a time period of 27 months, between March
2011 and June 2013. The number of epochs varied between 11 and 12 depending on
the object. The reduction of the astrometric measurements was carried out with
respect to the field stars. The relative parallax and proper motions were
transformed into absolute measurements using the background galaxies in our
fields.
We obtained absolute parallaxes for our six brown dwarfs with a precision
between 3 and 6 mas. We compared our results in a color-magnitude diagram with
other brown dwarfs with determined parallax and with the BT-Settl 2012
atmospheric models. For four of the six targets we found a good agreement in
luminosity with objects of similar spectral types. We obtained an improved
accuracy in the parallaxes and proper motions in comparison to previous works.
The object 2MASS J11061197+2754225 is more than 1 mag overluminous in all bands
pointing to binarity or high order multiplicity.Comment: 9 pages, 15 figures. Astronomy & Astrophysics, 201
High-fidelity view of the structure and fragmentation of the high-mass, filamentary IRDC G11.11-0.12
Star formation in molecular clouds is intimately linked to their internal
mass distribution. We present an unprecedentedly detailed analysis of the
column density structure of a high-mass, filamentary molecular cloud, namely
IRDC G11.11-0.12 (G11). We use two novel column density mapping techniques:
high-resolution (FWHM=2", or ~0.035 pc) dust extinction mapping in near- and
mid-infrared, and dust emission mapping with the Herschel satellite. These two
completely independent techniques yield a strikingly good agreement,
highlighting their complementarity and robustness. We first analyze the dense
gas mass fraction and linear mass density of G11. We show that G11 has a top
heavy mass distribution and has a linear mass density (M_l ~ 600 Msun pc^{-1})
that greatly exceeds the critical value of a self-gravitating, non-turbulent
cylinder. These properties make G11 analogous to the Orion A cloud, despite its
low star-forming activity. This suggests that the amount of dense gas in
molecular clouds is more closely connected to environmental parameters or
global processes than to the star-forming efficiency of the cloud. We then
examine hierarchical fragmentation in G11 over a wide range of size-scales and
densities. We show that at scales 0.5 pc > l > 8 pc, the fragmentation of G11
is in agreement with that of a self-gravitating cylinder. At scales smaller
than l < 0.5 pc, the results agree better with spherical Jeans' fragmentation.
One possible explanation for the change in fragmentation characteristics is the
size-scale-dependent collapse time-scale that results from the finite size of
real molecular clouds: at scales l < 0.5 pc, fragmentation becomes sufficiently
rapid to be unaffected by global instabilities.Comment: 8 pages, 8 figures, accepted to A&
The Star-Forming Region NGC 346 in the Small Magellanic Cloud with Hubble Space Telescope ACS Observations I. Photometry
We present a photometric study of the star-forming region NGC 346 and its
surrounding field in the Small Magellanic Cloud, using data taken with the
Advanced Camera for Surveys (ACS) on board the Hubble Space Telescope (HST).
The data set contains both short and long exposures for increased dynamic
range, and photometry was performed using the ACS module of the stellar
photometry package DOLPHOT. We detected almost 100,000 stars over a magnitude
range of V ~ 11 to V ~ 28 mag, including all stellar types from the most
massive young stars to faint lower main sequence and pre-main sequence stars.
We find that this region, which is characterized by a plethora of stellar
systems and interesting objects, is an outstanding example of mixed stellar
populations. We take into account different features of the color-magnitude
diagram of all the detected stars to distinguish the two dominant stellar
systems: The stellar association NGC 346 and the old spherical star cluster BS
90. These observations provide a complete stellar sample of a field about 5
arcmin x 5 arcmin around the most active star-forming region in this galaxy.
Considering the importance of these data for various investigations in the
area, we provide the full stellar catalog from our photometry. This paper is
the first part of an ongoing study to investigate in detail the two dominant
stellar systems in the area and their surrounding field.Comment: 8 pages, 5 figures, Accepted for publication in The Astrophysical
Journal Supplement Series, A high-resolution version can be found at:
http://www.astro.uni-bonn.de/~dgoulier/Science/Gouliermis+_NGC346_I.pd
Paraphimosis in Equine
Paraphimosis is a condition in which the glans of the penis cannot be withdrawn into the prepuce. The condition is probably more common in the horse than any other domestic animal with the possible exception of the dog
Inconsistent use of gesture space during abstract pointing impairs language comprehension
Pointing toward concrete objects is a well-known and efficient communicative strategy. Much less is known about the communicative effectiveness of abstract pointing where the pointing gestures are directed to “empty space.” McNeill's (2003) observations suggest that abstract pointing can be used to establish referents in gesture space, without the referents being physically present. Recently, however, it has been shown that abstract pointing typically provides redundant information to the uttered speech thereby suggesting a very limited communicative value (So et al., 2009). In a first approach to tackle this issue we were interested to know whether perceivers are sensitive at all to this gesture cue or whether it is completely discarded as irrelevant add-on information. Sensitivity to for instance a gesture-speech mismatch would suggest a potential communicative function of abstract pointing. Therefore, we devised a mismatch paradigm in which participants watched a video where a female was interviewed on various topics. During her responses, she established two concepts in space using abstract pointing (e.g., pointing to the left when saying Donald, and pointing to the right when saying Mickey). In the last response to each topic, the pointing gesture accompanying a target word (e.g., Donald) was either consistent or inconsistent with the previously established location. Event related brain potentials showed an increased N400 and P600 when gesture and speech referred to different referents, indicating that inconsistent use of gesture space impairs language comprehension. Abstract pointing was found to influence comprehension even though gesture was not crucial to understanding the sentences or conducting the experimental task. These data suggest that a referent was retrieved via abstract pointing and that abstract pointing can potentially be used for referent indication in a discourse. We conclude that abstract pointing has a potential communicative function
Investigation of vertical cavity surface emitting laser dynamics for neuromorphic photonic systems
We report an approach based upon vertical cavity surface emitting lasers (VCSELs) to reproduce optically different behaviors exhibited by biological neurons but on a much faster timescale. The technique proposed is based on the polarization switching and nonlinear dynamics induced in a single VCSEL under polarized optical injection. The particular attributes of VCSELs and the simple experimental configuration used in this work offer prospects of fast, reconfigurable processing elements with excellent fan-out and scaling potentials for use in future computational paradigms and artificial neural networks. © 2012 American Institute of Physics
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