2,166 research outputs found
IRAS colors of VLA identified objects in the galaxy
Infrared Astronomy Satellite (IRAS) sources found within 4 degrees of l = 125 deg, b = 2 deg on the 3rd HCON 60 micron Sky Brightness Images were observed at the Very Large Array (VLA). Regions were to be identified where massive stars are forming by looking for small areas of radio continuum emissions. The IRAS sources could be divided into three groups by their IRAS 12 micron/25 micron and 60 micron/100 micron color. The group identified with star forming regions contained essentially all of the objects with extended radio emission. In all of these cases the extended radio emission showed a morphology consistent with the identification of these objects as HII regions. The conclusion drawn is that star formation regions can be distinguished from other objects by their infrared colors
IRAS results on outer galaxy star formation
An infrared defined (60 micron) sample of IRAS sources were systematically studied in order to investigate star formation in the outer Galaxy. Five percent of the sample are point sources with IRAS spectra that suggest the emission is from a dust shell surrounding a mature star. Ninety five percent have spectra where flux density strictly rises with wavelength. The sources are extended, and it is shown that Point Source Catalog fluxes seriously underestimate total fluxes. CO kinematic distances were reliably assigned to two thirds of the sources. Most of the infrared luminosities correspond to B spectral types. Six cm continuum emission were detected from all sources inferred to have spectral type B1 or earlier. The combined IRAS/CO/6 cm data show these sources are young, moderately massive stars that are embedded in interstellar clouds. The young embedded sources define a distinct band in an IRAS color-colar diagram. Normal IRAS galaxies fall in the same band, consistent with the interpretation that their infrared emission is due to star formation
The origin of organic emission in NGC 2071
Context: The physical origin behind organic emission in embedded low-mass
star formation has been fiercely debated in the last two decades. A multitude
of scenarios have been proposed, from a hot corino to PDRs on cavity walls to
shock excitation.
Aims: The aim of this paper is to determine the location and the
corresponding physical conditions of the gas responsible for organics emission
lines. The outflows around the small protocluster NGC 2071 are an ideal testbed
to differentiate between various scenarios.
Methods: Using Herschel-HIFI and the SMA, observations of CH3OH, H2CO and
CH3CN emission lines over a wide range of excitation energies were obtained.
Comparisons to a grid of radiative transfer models provide constraints on the
physical conditions. Comparison to H2O line shape is able to trace gas-phase
synthesis versus a sputtered origin.
Results: Emission of organics originates in three spots: the continuum
sources IRS 1 ('B') and IRS 3 ('A') as well as a outflow position ('F').
Densities are above 10 cm and temperatures between 100 to 200 K.
CH3OH emission observed with HIFI originates in all three regions and cannot be
associated with a single region. Very little organic emission originates
outside of these regions.
Conclusions: Although the three regions are small (<1,500 AU), gas-phase
organics likely originate from sputtering of ices due to outflow activity. The
derived high densities (>10 cm) are likely a requirement for organic
molecules to survive from being destroyed by shock products. The lack of
spatially extended emission confirms that organic molecules cannot (re)form
through gas-phase synthesis, as opposed to H2O, which shows strong line wing
emission. The lack of CH3CN emission at 'F' is evidence for a different history
of ice processing due to the absence of a protostar at that location and recent
ice mantle evaporation.Comment: 10 Pages, 8 figures, Accepted for Astronomy and Astrophysic
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Voluntary and Involuntary Self-Disclosure in Decision-Making Virtual Teams
This study investigates the roles of visual representation and verbal self-disclosure in decision making virtual teams via a content analysis of group discussions. Findings indicate that visual representation encourages increased self-disclosure in the form of personal and universal revelations of facts and thoughts during virtual group communication. Increased revelations are in turn found to impact the nature of group decisions. These results theoretical and practical implications for virtual decision making
Solving Case Studies through Asynchronous Learning Networks: Possibilities and Limitations
Business Schools have been using case studies to present real or hypothetical situations to bridge the gap
between knowledge and action. New communication technologies can be incorporated into the case
method of teaching, allowing participants to be in different locations and to work at their own convenience.
An Asynchronous Learning Network is a Computer-Mediated Communication System to support
"anytime/anywhere" interaction by providing a combination of database and conferencing system. A field
experiment was conducted to test the effectiveness of an ALN vs. traditional manual methods at both the
individual and group level for the solution of a case study. Findings indicate that groups working in an
asynchronous networked environment produced better and more complete solutions to the case study, but
were less satisfied with the interaction process. Further research in the implementation of ALN's promises
to enhance the quality of education and to provide future managers with essential expertise in new
communication technologies.Information Systems Working Papers Serie
A sharper view of the outer Galaxy at 1420 and 408 MHz from the Canadian Galactic Plane Survey II: The catalogue of extended radio sources
A new catalogue of extended radio sources has been prepared based on
arcminute-resolution 1420 MHz images from the Canadian Galactic Plane Survey
(CGPS). The new catalogue provides both 1420 MHz and 408 MHz flux density
measurements on sources found near the Galactic plane in the second quadrant of
our Galaxy. In addition cross-identifications are made with other major radio
catalogues and information is provided to facilitate the recovery of CGPS image
data associated with each catalogued source. Numerous new radio sources are
identified and the catalogue provides a comprehensive summary of both newly
discovered and previously known HII regions and supernova remnants in the outer
Galaxy. The catalogue should be of use both for synoptic studies of Galactic
structure and for placing higher resolution observations, at radio and other
wavelengths, in context.Comment: accepted for publication in MNRAS, 8 pages, 6 figure
On the Optimal Space Complexity of Consensus for Anonymous Processes
The optimal space complexity of consensus in shared memory is a decades-old
open problem. For a system of processes, no algorithm is known that uses a
sublinear number of registers. However, the best known lower bound due to Fich,
Herlihy, and Shavit requires registers.
The special symmetric case of the problem where processes are anonymous (run
the same algorithm) has also attracted attention. Even in this case, the best
lower and upper bounds are still and . Moreover, Fich,
Herlihy, and Shavit first proved their lower bound for anonymous processes, and
then extended it to the general case. As such, resolving the anonymous case
might be a significant step towards understanding and solving the general
problem.
In this work, we show that in a system of anonymous processes, any consensus
algorithm satisfying nondeterministic solo termination has to use
read-write registers in some execution. This implies an lower bound
on the space complexity of deterministic obstruction-free and randomized
wait-free consensus, matching the upper bound and closing the symmetric case of
the open problem
Stock option grants to target CEOs during private merger negotiations
Unscheduled stock options to target chief executive officers (CEOs) are a nontrivial phenomenon during private merger negotiations. In 920 acquisition bids during 1999-2007, over 13% of targets grant them. These options substitute for golden parachutes and compensate target CEOs for the benefits they forfeit because of the merger. Targets granting unscheduled options are more likely to be acquired but they earn lower premiums. Consequently, deal value drops by '62 for every dollar target CEOs receive from unscheduled options. Conversely, acquirers of targets offering these awards experience higher returns. Therefore, deals involving unscheduled grants exhibit a transfer of wealth from target shareholders to bidder shareholders
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