1,243 research outputs found
Social Interaction Between Deaf and Hearing People
This study examined the personal experiences of hearing people in their interactions with Deaf persons and their knowledge about Deaf culture. The research involved questioning hearing people about their perceptions and interactions with Deaf people and Deaf culture in an effort to gain insight as to how the lives of Deaf people can be improved in mainstream culture. It was predicted that a majority of hearing participants would describe a lack of knowledge about Deaf culture, discomfort interacting with a Deaf person, and an agreement that a need exists for better understanding of Deaf culture. A survey was conducted with 582 undergraduates at the University of Mississippi. Of the original six hypotheses, the results supported the predictions that a majority of hearing participants would report a lack of knowledge about Deaf culture and how to interact with a Deaf person and that hearing participants would agree that there is a need for better understanding of Deaf culture. The results indicate positive attitudes about Deaf people and further show the need for improvement of public knowledge about Deaf culture and people, which fits within the existing body of research
Multifrequency Observations of Giant Radio Pulses from the Millisecond Pulsar B1937+21
Giant pulses are short, intense outbursts of radio emission with a power-law
intensity distribution that have been observed from the Crab Pulsar and PSR
B1937+21. We have undertaken a systematic study of giant pulses from PSR
B1937+21 using the Arecibo telescope at 430, 1420, and 2380 MHz. At 430 MHz,
interstellar scattering broadens giant pulses to durations of secs,
but at higher frequencies the pulses are very short, typically lasting only
-secs. At each frequency, giant pulses are emitted only in narrow
(\lsim10 \mus) windows of pulse phase located -sec after the
main and interpulse peaks. Although some pulse-to-pulse jitter in arrival times
is observed, the mean arrival phase appears stable; a timing analysis of the
giant pulses yields precision competitive with the best average profile timing
studies. We have measured the intensity distribution of the giant pulses,
confirming a roughly power-law distribution with approximate index of -1.8,
contributing \gsim0.1% to the total flux at each frequency. We also find that
the intensity of giant pulses falls off with a slightly steeper power of
frequency than the ordinary radio emission.Comment: 21 pages, 10 Postscript figures; LaTeX with aaspp4.sty and epsf.tex;
submitted to Ap
An Infrared Study of the Circumstellar Material Associated with the Carbon Star R Sculptoris
The asymptotic giant branch (AGB) star R Sculptoris (R Scl) is one of the
most extensively studied stars on the AGB. R Scl is a carbon star with a
massive circumstellar shell () which
is thought to have been produced during a thermal pulse event years
ago. To study the thermal dust emission associated with its circumstellar
material, observations were taken with the Faint Object InfraRed CAMera for the
SOFIA Telescope (FORCAST) at 19.7, 25.2, 31.5, 34.8, and 37.1 m. Maps of
the infrared emission at these wavelengths were used to study the morphology
and temperature structure of the spatially extended dust emission. Using the
radiative transfer code DUSTY and fitting the spatial profile of the emission,
we find that a geometrically thin dust shell cannot reproduce the observed
spatially resolved emission. Instead, a second dust component in addition to
the shell is needed to reproduce the observed emission. This component, which
lies interior to the dust shell, traces the circumstellar envelope of R Scl. It
is best fit by a density profile with where
and dust mass of
. The strong departure from an
law indicates that the mass-loss rate of R Scl has not been constant.
This result is consistent with a slow decline in the post-pulse mass-loss which
has been inferred from observations of the molecular gas.Comment: 10 pages, 10 figures, accepted to Ap
The Extremal Structure Of Locally Compact Convex Sets
Let X be a locally compact closed convex subset of a locally convex Hausdorff topological linear space E. Then every exposed point of X is strongly exposed. The definitions of denting (strongly extreme) ray and strongly exposed ray are given for convex subsets of E. If X does not contain a line, then every extreme ray is strongly extreme and every exposed ray is strongly exposed. An example is given to show that the hypothesis that X be locally compact is necessary in both cases. © 1976 Pacific Journal of Mathematics. All rights reserved
Simultaneous Dual Frequency Observations of Giant Pulses from the Crab Pulsar
Simultaneous measurements of giant pulses from the Crab pulsar were taken at
two widely spaced frequencies using the real-time detection of a giant pulse at
1.4 GHz at the Very Large Array to trigger the observation of that same pulse
at 0.6 GHz at a 25-m telescope in Green Bank, WV. Interstellar dispersion of
the signals provided the necessary time to communicate the trigger across the
country via the Internet. About 70% of the pulses are seen at both 1.4 GHz and
0.6 GHz, implying an emission mechanism bandwidth of at least 0.8 GHz at 1 GHz
for pulse structure on time scales of one to ten microseconds.
The arrival times at both frequencies display a jitter of 100 microseconds
within the window defined by the average main pulse profile and are tightly
correlated. This tight correlation places limits on both the emission mechanism
and on frequency dependent propagation within the magnetosphere.
At 1.4 GHz the giant pulses are resolved into several, closely spaced
components. Simultaneous observations at 1.4 GHz and 4.9 GHz show that the
component splitting is frequency independent. We conclude that the multiplicity
of components is intrinsic to the emission from the pulsar, and reject the
hypothesis that this is the result of multiple imaging as the signal propagates
through the perturbed thermal plasma in the surrounding nebula. At both 1.4 GHz
and 0.6 GHz the pulses are characterized by a fast rise time and an exponential
decay time which are correlated. The pulse broadening with its exponential
decay form is most likely the result of multipath propagation in intervening
ionized gas.Comment: LaTeX, 18 pages, 7 figures, accepted for publication in The
Astrophysical Journa
What makes the Crab pulsar shine?
Our high time resolution observations of individual pulses from the Crab
pulsar show that the main pulse and interpulse differ in temporal behavior,
spectral behavior, polarization and dispersion. The main pulse properties are
consistent with one current model of pulsar radio emission, namely, soliton
collapse in strong plasma turbulence. The high-frequency interpulse is quite
another story. Its dynamic spectrum cannot easily be explained by any current
emission model; its excess dispersion must come from propagation through the
star's magnetosphere. We suspect the high-frequency interpulse does not follow
the ``standard model'', but rather comes from some unexpected region within the
star's magnetosphere. Similar observations of other pulsars will reveal whether
the radio emission mechanisms operating in the Crab pulsar are unique to that
star, or can be identified in the general population.Comment: 5 pages, 2 figures, to appear in proceedings of meeting "Forty Years
of Pulsars: Millisecond Pulsars, Magnetars and More", Montreal, August 200
Giant Radio Pulses from the Crab Pulsar
Individual giant radio pulses (GRPs) from the Crab pulsar last only a few
microseconds. However, during that time they rank among the brightest objects
in the radio sky reaching peak flux densities of up to 1500 Jy even at high
radio frequencies. Our observations show that GRPs can be found in all phases
of ordinary radio emission including the two high frequency components (HFCs)
visible only between 5 and 9 GHz (Moffett & Hankins, 1996). This leads us to
believe that there is no difference in the emission mechanism of the main pulse
(MP), inter pulse (IP) and HFCs. High resolution dynamic spectra from our
recent observations of giant pulses with the Effelsberg telescope at a center
frequency of 8.35 GHz show distinct spectral maxima within our observational
bandwidth of 500 MHz for individual pulses. Their narrow band components appear
to be brighter at higher frequencies (8.6 GHz) than at lower ones (8.1 GHz).
Moreover, there is an evidence for spectral evolution within and between those
structures. High frequency features occur earlier than low frequency ones.
Strong plasma turbulence might be a feasible mechanism for the creation of the
high energy densities of ~6.7 x 10^4 erg cm^-3 and brightness temperatures of
10^31 K.Comment: accepted by Advances in Space Research, to appear in the 35th COSPAR
assembly proceeding
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