396 research outputs found
Obstacles and Opportunities: Funding Research at the 1890 Land Grant Institutions
Similar to other university faculties, faculty members at 1890 land grant institutions are expected to support their research programs with grants from sources outside their institutions. Although the expectation of securing grants has not received the public attention that the publish or perish dictum has, faculty at the 1890 institutions seeking promotion and tenure must increasingly demonstrate that they can procure grant funds. Numerous inhibitive factors, however, tend to attenuate the success of 1890 faculty in obtaining research grant funding and in implementing such research projects. In this study, three key factors are examined: political, research infrastructure, and faculty initiative. The perceived importance of benefits of conducting research is also examined. Descriptive statistics and analysis of covariance are used to evaluate potential barriers to research, faculty access to information about research grants programs, opportunities to compete for grants, and experience in obtaining competitive grants. Data for this analysis are taken from a probability sample of faculty members at the 1890 land grant institutions and Tuskegee University. Also, activities are proposed that need to be implemented in order to minimize the factors preventing many scientists at the 1890 institutions from obtaining more competitive grants
Sociodemographic Predictors of Rural Poverty: A Regional Analysis
The focus of the present study is to determine the extent to which the socio-demographic variables of education, occupation, number of children, race, sex, age, and willingness to travel for employment and predictors of a rural family\u27s level of poverty. Discriminant analysis is employed to assess the accuracy of these variables in - discriminating between poor and nonpoor families randomly selected from thirty low income, rural counties in ten contiguous southeastern states. The results are supportive of previous studies as these variables are found to be statistically significant discriminants between the poor and the nonpoor. The profile of a rural poor head of household is a poorly educated, semi-skilled, female, black, farm resident who tends to be old, have a large number of children, and be less willing to travel for employment outside of one\u27s immediate area
Radiation Pressure Supported Starburst Disks and AGN Fueling
We consider the structure of marginally Toomre-stable starburst disks under
the assumption that radiation pressure on dust grains provides the dominant
vertical support against gravity. This is particularly appropriate when the
disk is optically thick to its own IR radiation, as in the central regions of
ULIRGs. Because the disk radiates at its Eddington limit, the Schmidt-law for
star formation changes in the optically-thick limit, with the star formation
rate per unit area scaling as Sigma_g/kappa, where Sigma_g is the gas surface
density and kappa is the mean opacity. We show that optically thick starburst
disks have a characteristic flux and dust effective temperature of F ~ 10^{13}
L_sun/kpc^2 and T_eff ~ 90K, respectively. We compare our predictions with
observations and find good agreement. We extend our model from many-hundred
parsec scales to sub-parsec scales and address the problem of fueling AGN. We
assume that angular momentum transport proceeds via global torques rather than
a local viscosity. We account for the radial depletion of gas due to star
formation and find a strong bifurcation between two classes of disk models: (1)
solutions with a starburst on large scales that consumes all of the gas with
little fueling of a central AGN and (2) models with an outer large-scale
starburst accompanied by a more compact starburst on 1-10 pc scales and a
bright central AGN. The luminosity of the latter models is in many cases
dominated by the AGN. We show that the vertical thickness of the starburst disk
on pc scales can approach h ~ r, perhaps accounting for the nuclear obscuration
in some Type 2 AGN. We also argue that the disk of young stars in the Galactic
Center may be the remnant of such a compact nuclear starburst.Comment: 26 pages, 9 figures, emulateapj, accepted to ApJ, minor changes,
discussion tightened, references adde
Theory, construction, and applications of the water table
This thesis document was issued under the authority of another institution, not NPS. At the time it was written, a copy was added to the NPS Library collection for reasons not now known. Â It has been included in the digital archive for its historical value to NPS. Â Not believed to be a CIVINS (Civilian Institutions) title.The object of this thesis is threefold, to present the theoretical analogy between the flow of a compressible gas, such as air, and the flow of water with a free surface, to describe the details of construction of the water table which utilizes the above analogy, and to outline the demonstrate the applications of the water table in the investigation of air flow.http://www.archive.org/details/theoryconstructi00smolLieutenant Commander, United States Nav
Dust emissivity in the Submm/Mm: SCUBA and SIMBA observations of Barnard 68
We have observed the dark cloud Barnard 68 with SCUBA at 850 um and with
SIMBA at 1.2 mm. The submillimetre and millimetre dust emission correlate well
with the extinction map of Alves, Lada and Lada (2001).The A_V/850um
correlation is clearly not linear and suggests lower temperatures for the dust
in the inner core of the cloud. Assuming a model for the temperature gradient,
we derive the cloud-averaged dust emissivities (normalised to the V-Band
extinction efficiency) at 850 um and 1.2 mm. We find k_850um/k_V = 4.0 +/- 1.0
x 10^-5 and k_1.2mm/k_V = 9.0 +/- 3.0 x 10^-6. These values are compared with
other determinations in this wavelength regime and with expectations for models
of diffuse dust and grain growth in dense clouds.Comment: 8 pages, 4 figures, A&A accepted (Letter), referee forma
The Role of Galactic Winds on Molecular Gas Emission from Galaxy Mergers
We assess the impact of starburst and AGN feedback-driven winds on the CO
emission from galaxy mergers, and, in particular, search for signatures of
these winds in the simulated CO morphologies and emission line profiles. We do
so by combining a 3D non-LTE molecular line radiative transfer code with
smoothed particle hydrodynamics (SPH) simulations of galaxy mergers that
include prescriptions for star formation, black hole growth, a multiphase
interstellar medium (ISM), and the winds associated with star formation and
black hole growth. Our main results are: (1) Galactic winds can drive outflows
of masses ~10^8-10^9 Msun which may be imaged via CO emission line mapping. (2)
AGN feedback-driven winds are able to drive imageable CO outflows for longer
periods of time than starburst-driven winds owing to the greater amount of
energy imparted to the ISM by AGN feedback compared to star formation. (3)
Galactic winds can control the spatial extent of the CO emission in post-merger
galaxies, and may serve as a physical motivation for the sub-kiloparsec scale
CO emission radii observed in local advanced mergers. (4) Secondary emission
peaks at velocities greater than the circular velocity are seen in the CO
emission lines in all models. In models with winds, these high velocity peaks
are seen to preferentially correspond to outflowing gas entrained in winds,
which is not the case in the model without winds. The high velocity peaks seen
in models without winds are typically confined to velocity offsets (from the
systemic) < 1.7 times the circular velocity, whereas the models with AGN
feedback-driven winds can drive high velocity peaks to ~2.5 times the circular
velocity.Comment: Accepted by ApJ; Minor revisions; Resolution tests include
Properties of Nearby Starburst Galaxies Based on their Diffuse Gamma-ray Emission
The physical relationship between the far-infrared and radio fluxes of star
forming galaxies has yet to be definitively determined. The favored
interpretation, the "calorimeter model," requires that supernova generated
cosmic ray (CR) electrons cool rapidly via synchrotron radiation. However, this
cooling should steepen their radio spectra beyond what is observed, and so
enhanced ionization losses at low energies from high gas densities are also
required. Further, evaluating the minimum energy magnetic field strength with
the traditional scaling of the synchrotron flux may underestimate the true
value in massive starbursts if their magnetic energy density is comparable to
the hydrostatic pressure of their disks. Gamma-ray spectra of starburst
galaxies, combined with radio data, provide a less ambiguous estimate of these
physical properties in starburst nuclei. While the radio flux is most sensitive
to the magnetic field, the GeV gamma-ray spectrum normalization depends
primarily on gas density. To this end, spectra above 100 MeV were constructed
for two nearby starburst galaxies, NGC 253 and M82, using Fermi data. Their
nuclear radio and far-infrared spectra from the literature are compared to new
models of the steady-state CR distributions expected from starburst galaxies.
Models with high magnetic fields, favoring galaxy calorimetry, are overall
better fits to the observations. These solutions also imply relatively high
densities and CR ionization rates, consistent with molecular cloud studies.Comment: Accepted to Ap
The structure of protostellar envelopes derived from submillimeter continuum images
High dynamic range imaging of submillimeter dust emission from the envelopes
of eight young protostars in the Taurus and Perseus star-forming regions has
been carried out using the SCUBA submillimeter camera on the James Clerk
Maxwell Telescope. Good correspondence between the spectral classifications of
the protostars and the spatial distributions of their dust emission is
observed, in the sense that those with cooler spectral energy distributions
also have a larger fraction of the submillimeter flux originating in an
extended envelope compared with a disk. This results from the cool sources
having more massive envelopes rather than warm sources having larger disks.
Azimuthally-averaged radial profiles of the dust emission are used to derive
the power-law index of the envelope density distributions, p (defined by rho
proportional to r^-p), and most of the sources are found to have values of p
consistent with those predicted by models of cloud collapse. However, the
youngest protostars in our sample, L1527 and HH211-mm, deviate significantly
from the theoretical predictions, exhibiting values of p somewhat lower than
can be accounted for by existing models. For L1527 heating of the envelope by
shocks where the outflow impinges on the surrounding medium may explain our
result. For HH211-mm another explanation is needed, and one possibility is that
a shallow density profile is being maintained in the outer envelope by magnetic
fields and/or turbulence. If this is the case star formation must be determined
by the rate at which the support is lost from the cloud, rather than the
hydrodynamical properties of the envelope, such as the sound speed.Comment: Accepted for publication in the Astrophysical Journa
Getting Human Papillomavirus Vaccination Back on Track: A National Survey
Purpose: Adolescent human papillomavirus (HPV) vaccine uptake in the United States dropped during the COVID-19 pandemic due to a decrease in well visits. This study sought to identify opportunities for primary care professionals (PCPs) to get adolescent vaccination back on track. Methods: In early 2021, we recruited 1,047 PCPs (71% physicians) who provided adolescent vaccines in the United States from an existing panel. Participants completed an online survey about changes in adolescent HPV vaccine uptake and actions taken to promote vaccination during the pandemic, as well as intentions to engage in activities to increase adolescent vaccination in the next 3 months. Results: A substantial proportion of PCPs (43%) reported that HPV vaccine uptake decreased in the first year of the pandemic; few (7%) PCPs reported an increase in uptake. PCPs reporting increased uptake were more likely to have used nurse-only vaccination visits, held drop-in and drive-through vaccination clinics, and used telehealth visits to recommend vaccination (all p < .05). Nearly two-thirds (62%) of all PCPs planned to promote adolescent vaccine uptake in the next 3 months. Planning was more common among PCPs who believed HPV vaccine uptake at their clinics increased during the pandemic, who saw more than 10 adolescent patients per week, who had ever reviewed their clinic's vaccination rates, and were nurses (all p < .05). Discussion: Many PCPs saw HPV vaccination drop during the pandemic. Several interventions could help clinics get HPV vaccination back on track, including increasing the availability of nurse-only vaccination visits and vaccination-only clinics
Extraplanar Dust in Spiral Galaxies: Tracing Outflows in the Disk-Halo Interface
There is now ample evidence that the interstellar thick disks of spiral
galaxies are dusty. Although the majority of extraplanar gas in the first few
kiloparsecs above the plane of a spiral galaxy is matter that has been expelled
from the thin disk, the feedback-driven expulsion does not destroy dust grains
altogether (and there is not yet any good measure suggesting it changes the
dust-to-gas mass ratio). Direct optical imaging of a majority of edge-on spiral
galaxies shows large numbers of dusty clouds populating the thick disk to
heights z~2 kpc. These observations are likely revealing a cold, dense phase of
the thick disk interstellar medium. New observations in the mid-infrared show
emission from traditional grains and polycyclic aromatic hydrocarbons (PAHs) in
the thick disks of spiral galaxies. PAHs are found to have large scale heights
and to arise both in the dense dusty clouds traced through direct optical
imaging and in the diffuse ionized gas. In this contribution, we briefly
summarize these probes of dust in the thick disks of spiral galaxies. We also
argue that not only can dust can be used to trace extraplanar material that has
come from within the thick disk, but that its absence can be a marker for newly
accreted matter from the circumgalactic or intergalactic medium. Thus,
observations of dust can perhaps provide a quantitative measure of the
importance of "outflow versus infall" in spiral galaxies.Comment: 8 pages; Invited review for the proceedings of "The Role of Disk-Halo
Interaction in Galaxy Evolution: Outflow vs. Infall?" (Ed. M. de Avillez), in
Espinho, Portugal, 18-22 August 2008 ; high resolution version at
http://www.nd.edu/~jhowk/Papers/papers.html#conferenc
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