1,640 research outputs found
High resolution observations of compact H II regions at 230 GHz
Based on the idea that star formation goes on progressively in molecular clouds, a search was conducted for protostars by mapping compact H II regions at a frequency of 250 GHz. The IRAM 30 m radio telescope was used with a (3)He cooled bolometer. Twenty compact H II regions usually obtaining twice the expected free-free flux density, positionally coincident with the H II region, were observed. Even fine structure within the H II regions can be traced in the maps as in the case of G75.84+0.40 near ON-2. The high degree of coincidence between the 250 and 5 GHz map of Harris shows that the excess flux density observed must come from dust mixed with the ionized gas. Part of the dust must however be accumulated in the outer part of the H II region, since in some cases the contours are shifted outwards relative to the radio maps. This is consistent with the fact that in those cases where enough information is available to make a model fit, temperatures were derived of 80 + or - 30 K
Current balance levels in deaf and hearing impaired children
The purpose of this systematic review of literature is to evaluate the current balance levels in deaf and hearing-impaired children. Children with hearing impairments show balance and motor deficits mainly due to damaged or undeveloped areas of the vestibular system. The auditory sense plays a dynamic role in producing functional movements and motor coordination skills. Researchers founded that motor development skills are especially important to Deaf children because better skills lead to participation in Deaf sports as well as increased opportunities for social interaction. For children born or diagnosed as deaf or hearing-impaired, there is still the opportunity to keeping up with their peers through modifying of the learning environment. These capabilities are essential to the attainment of cognition, behavior, social speech, and development. Having the clinics, programs, and teachers understand the capabilities, limitations, and current level of abilities can help educators, paraprofessionals, and other specialist develop appropriate instruction, activities, lessons, and goals for deaf and hearing-impaired children. Recognizing the national need to improve physical activity, accessible assessments, and appropriate techniques can benefit children with hearing impairments in motor development and balance levels
The Nature of Optical Features in the Inner Region of the 3C48 Host Galaxy
The well-known quasar 3C48 is the most powerful compact steep-spectrum
radio-loud QSO at low redshifts. It also has two unusual optical features
within the radius of the radio jet (~1"): (1) an anomalous, high-velocity
narrow-line component, having several times as much flux as does the
narrow-line component coinciding with the broad-line redshift; and (2) a bright
continuum peak (3C48A) ~1" northeast of the quasar. Both of these optical
features have been conjectured to be related to the radio jet. Here we explore
these suggestions. We have obtained Gemini North GMOS integral-field-unit (IFU)
spectroscopy of the central region around 3C48. We use the unique features of
the IFU data to remove unresolved emission at the position of the quasar. The
resolved emission at the wavelength of the high-velocity component is peaked
<~0.25" north of the quasar, at virtually the same position angle as the base
of the radio jet. These observations appear to confirm that this high-velocity
gas is connected with the radio jet. However, most of the emission comes from a
region where the jet is still well collimated, rather than from the regions
where the radio maps indicate strong interaction with an external medium. We
also present the results of HST STIS spectroscopy of 3C48A. We show that 3C48A
is dominated by stars with a luminosity-weighted age of ~1.4 X 10^8 years,
substantially older than any reasonable estimate for the age of the radio
source. Our IFU data indicate a similar age. Thus, 3C48A almost certainly
cannot be attributed to jet-induced star formation. The host galaxy of 3C48 is
clearly the result of a merger, and 3C48A seems much more likely to be the
distorted nucleus of the merging partner, in which star formation was induced
during the previous close passage.Comment: 10 pages, accepted by The Astrophysical Journa
3C 48: Stellar Populations and the Kinematics of Stars and Gas in the Host Galaxy
We present deep Keck LRIS spectroscopy of the host galaxy of 3C 48. Our
observations at various slit positions sample the different luminous components
near the quasar, including the apparent tidal tail to the NW and several strong
emission line regions.
By fitting Bruzual & Charlot (1996) population synthesis models to our
spectra, we obtain ages for the most recent major episodes of star formation in
various parts of the host galaxy covered by our slits. There is vigorous
current star formation in regions just NE and SE of the quasar and
post-starburst regions with ages up to ~10^8 years in other parts of the host
galaxy, but most of the NW tidal tail shows no sign of significant recent star
formation. We use these model fits, together with the kinematics of the stars
and gas, to outline a plausible evolutionary history for the host galaxy, its
recent starburst activity, the triggering of the quasar, and the interaction of
the radio jet with the ambient gas.
There is strong evidence that the 3C 48 host is an ongoing merger, and that
it is probably near the peak of its starburst activity. Nevertheless, the
quasar itself seems to suffer little extinction, perhaps because we are viewing
it along a particularly favorable line-of-sight.Comment: 27 pages plus 11 figures (7 postscript, 4 gif). Postscript version
including figures (1840 kb) available at
http://www.ifa.hawaii.edu/~canaguby/preprints.html . Accepted for publication
in Ap
Radio Supernova SN 1998bw and Its Relation to GRB 980425
SN 1998bw is an unusual Type Ic supernova that may be associated with the
-ray burst GRB 980425. We use a synchrotron self-absorption model for
its radio emission to deduce that the synchrotron-emitting gas is expanding
into a circumstellar medium of approximately density profile, at a
speed comparable to the speed of light. We assume that the efficiencies of
production of relativistic electrons and magnetic field are constant through
the evolution. The circumstellar density is consistent with that expected
around the massive star core thought to be the progenitor of SN 1998bw. The
explosion energy in material moving with velocity is ergs, with some preference for the high values. The rise in
the radio light curves observed at days 20-40 is inferred to be the result of a
rise in the energy of the blast wave by a factor . Interaction with a
jump in the ambient density is not consistent with the observed evolution. We
infer that the boost in energy is from a shell of matter from the explosion
that catches up with the decelerating shock front. Both the high explosion
energy and the nature of the energy input to the blast wave are difficult to
reconcile with energy input from the shock-accelerated high velocity ejecta
from a supernova. The implication is that there is irregular energy input from
a central engine, which is the type of model invoked for normal -ray
bursts. The link between SN 1998bw and GRB 980425 is thus strengthened.Comment: 21 pages, 9 figures, revised version to appear in Ap
Successional change in phosphorus stoichiometry explains the inverse relationship between herbivory and lupin density on Mount St. Helens
Background: The average nitrogen-to-phosphorus ratio (N:P) of insect herbivores is less than that of leaves, suggesting that P may mediate plant-insect interactions more often than appreciated. We investigated whether succession-related heterogeneity in N and P stoichiometry influences herbivore performance on N-fixing lupin (Lupinus lepidus) colonizing primary successional volcanic surfaces, where the abundances of several specialist lepidopteran herbivores are inversely related to lupin density and are known to alter lupin colonization dynamics. We examined larval performance in response to leaf nutritional characteristics using gelechiid and pyralid leaf-tiers, and a noctuid leaf-cutter. Methodology/Principal Findings: We conducted four studies. First, growth of larvae raised on wild-collected leaves responded positively to leaf %P and negatively to leaf carbon (%C), but there was no effect of %N or quinolizidine alkaloids (QAs). Noctuid survival was also positively related to %P. Second, we raised gelechiid larvae on greenhouse-grown lupins with factorial manipulation of competitors and soil N and P. In the presence of competition, larval mass was highest at intermediate leaf N:P and high %P. Third, survival of gelechiid larvae placed on lupins in high-density patches was greater when plant competitors were removed than on controls. Fourth, surveys of field-collected leaves in 2000, 2002, and 2003 indicated that both %P and %N were generally greater in plants from low-density areas. QAs in plants from low-density areas were equal to or higher than QAs in high-density areas. Conclusions/Significance: Our results demonstrate that declines in lupin P content under competitive conditions are associated with decreased larval growth and survival sufficient to cause the observed negative relationship between herbivore abundance and host density. The results support the theoretical finding that declines in stoichiometric resource quality (caused here by succession) have the potential to cause a decrease in consumer abundance despite very dense quantities of the resource. © 2009 Apple et al
Hot gas and dust in a protostellar cluster near W3(OH
We used the IRAM Interferometer to obtain sub-arcsecond resolution
observations of the high-mass star-forming region W3(OH) and its surroundings
at a frequency of 220 GHz. With the improved angular resolution, we distinguish
3 peaks in the thermal dust continuum emission originating from the hot core
region about 6 arcsec (0.06 pc) east of W3(OH). The dust emission peaks are
coincident with known radio continuum sources, one of which is of non-thermal
nature. The latter source is also at the center of expansion of a powerful
bipolar outflow observed in water maser emission. We determine the hot core
mass to be 15 solar masses based on the integrated dust continuum emission.
Simultaneously many molecular lines are detected allowing the analysis of the
temperature structure and the distribution of complex organic molecules in the
hot core. From HNCO lines, spanning a wide range of excitation, two 200 K
temperature peaks are found coincident with dust continuum emission peaks
suggesting embedded heating sources within them.Comment: 12 pages, 3 figure
Achieving mouse-level strategic evasion performance using real-time computational planning
Planning is an extraordinary ability in which the brain imagines and then
enacts evaluated possible futures. Using traditional planning models, computer
scientists have attempted to replicate this capacity with some level of success
but ultimately face a reoccurring limitation: as the plan grows in steps, the
number of different possible futures makes it intractable to determine the
right sequence of actions to reach a goal state. Based on prior theoretical
work on how the ecology of an animal governs the value of spatial planning, we
developed a more efficient biologically-inspired planning algorithm, TLPPO.
This algorithm allows us to achieve mouselevel predator evasion performance
with orders of magnitude less computation than a widespread algorithm for
planning in the situations of partial observability that typify predator-prey
interactions. We compared the performance of a real-time agent using TLPPO
against the performance of live mice, all tasked with evading a robot predator.
We anticipate these results will be helpful to planning algorithm users and
developers, as well as to areas of neuroscience where robot-animal interaction
can provide a useful approach to studying the basis of complex behaviors.Comment: 6 pages, 4 figures, ICRA 202
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