746 research outputs found
An analysis of reported student satisfaction and student satisfaction as perceived by academic advisors and student affairs staff at Iowa State University
The Public Trust and Parens Patriae Doctrines: Protecting Wildlife in Uncertain Political Times
HIghMass - High HI Mass, HI-Rich Galaxies at : Combined HI and H Observations
We present resolved HI and CO observations of three galaxies from the
HIghMass sample, a sample of HI-massive (), gas-rich
( in top for their ) galaxies identified in the ALFALFA
survey. Despite their high gas fractions, these are not low surface brightness
galaxies, and have typical specific star formation rates (SFR) for their
stellar masses. The three galaxies have normal star formation rates for their
HI masses, but unusually short star formation efficiency scale lengths,
indicating that the star formation bottleneck in these galaxies is in the
conversion of HI to H, not in converting H to stars. In addition, their
dark matter spin parameters () are above average, but not
exceptionally high, suggesting that their star formation has been suppressed
over cosmic time but are now becoming active, in agreement with prior H
observations.Comment: 20 pages, 13 figure
Trends and issues involving disabilities in higher education
People with disabilities have often been discriminated against in higher education; however, many institutions of higher education find ways of providing access to higher education for those with most forms of disabilities. Progress has been made in providing such access but undoubtedly there is still a need for more disability awareness, anti-stigma, and anti-discrimination training. At the same time higher education requirements, by default, involve higher cognitive capabilities. Some disabilities, those involving severe limitations of cognitive functioning, face insurmountable difficulties in meeting these higher intellectual demands, even with the most reasonable accommodations. Teacher education, for example, requires special attention to the cognitive tasks for which students are being prepared. We, therefore, discuss the role of teacher education in higher education and its special relationship to the matter of disability and inclusion. We also consider perspectives on the inclusion of individuals with disabilities in various other aspects of higher education
The ALFALFA "Almost Darks" Campaign: Pilot VLA HI Observations of Five High Mass-to-Light Ratio Systems
We present VLA HI spectral line imaging of 5 sources discovered by ALFALFA.
These targets are drawn from a larger sample of systems that were not uniquely
identified with optical counterparts during ALFALFA processing, and as such
have unusually high HI mass to light ratios. These candidate "Almost Dark"
objects fall into 4 categories: 1) objects with nearby HI neighbors that are
likely of tidal origin; 2) objects that appear to be part of a system of
multiple HI sources, but which may not be tidal in origin; 3) objects isolated
from nearby ALFALFA HI detections, but located near a gas-poor early-type
galaxy; 4) apparently isolated sources, with no object of coincident redshift
within ~400 kpc. Roughly 75% of the 200 objects without identified counterparts
in the .40 database (Haynes et al. 2011) fall into category 1. This
pilot sample contains the first five sources observed as part of a larger
effort to characterize HI sources with no readily identifiable optical
counterpart at single dish resolution. These objects span a range of HI mass
[7.41 < log(M) < 9.51] and HI mass to B-band luminosity ratios (3 <
M/L < 9). We compare the HI total intensity and velocity
fields to SDSS optical imaging and to archival GALEX UV imaging. Four of the
sources with uncertain or no optical counterpart in the ALFALFA data are
identified with low surface brightness optical counterparts in SDSS imaging
when compared with VLA HI intensity maps, and appear to be galaxies with clear
signs of ordered rotation. One source (AGC 208602) is likely tidal in nature.
We find no "dark galaxies" in this limited sample. The present observations
reveal complex sources with suppressed star formation, highlighting both the
observational difficulties and the necessity of synthesis follow-up
observations to understand these extreme objects. (abridged)Comment: Astronomical Journal, in pres
Mid-IR spectroscopy of T Tauri stars in Chamealeon I: evidence for processed dust at the earliest stages
We present mid-IR spectroscopy of three T Tauri stars in the young Chamealeon
I dark cloud obtained with TIMMI2 on the ESO 3.6m telescope. In these three
stars, the silicate emission band at 9.7 micron is prominent. We model it with
a mixture of amorphous olivine grains of different size, crystalline silicates
and silica. The fractional mass of these various components change widely from
star to star. While the spectrum of CR Cha is dominated by small amorphous
silicates, in VW Cha (and in a lesser degree in Glass I), there is clear
evidence of a large amount of processed dust in the form of crystalline
silicates and large amorphous grains. This is the first time that processed
dust has been detetected in very young T Tauri stars (~ 1 Myr).Comment: 5 pages, 4 Postscript figures. accepted for A&A Letter
C2D Spitzer-IRS spectra of disks around T Tauri stars V. Spectral decomposition
(Abridged) Dust particles evolve in size and lattice structure in
protoplanetary disks, due to coagulation, fragmentation and crystallization,
and are radially and vertically mixed in disks. This paper aims at determining
the mineralogical composition and size distribution of the dust grains in disks
around 58 T Tauri stars observed with Spitzer/IRS. We present a spectral
decomposition model that reproduces the IRS spectra over the full spectral
range. The model assumes two dust populations: a warm component responsible for
the 10\mu m emission arising from the disk inner regions and a colder component
responsible for the 20-30\mu m emission, arising from more distant regions. We
show evidence for a significant size distribution flattening compared to the
typical MRN distribution, providing an explanation for the usual boxy 10\mu m
feature profile generally observed. We reexamine the crystallinity paradox,
observationally identified by Olofsson et al. (2009), and we find a
simultaneous enrichment of the crystallinity in both the warm and cold regions,
while grain sizes in both components are uncorrelated. Our modeling results do
not show evidence for any correlations between the crystallinity and either the
star spectral type, or the X-ray luminosity (for a subset of the sample). The
size distribution flattening may suggests that grain coagulation is a slightly
more effective process than fragmentation in disk atmospheres, and that this
imbalance may last over most of the T Tauri phase. This result may also point
toward small grain depletion via strong stellar winds or radiation pressure in
the upper layers of disk. The non negligible cold crystallinity fractions
suggests efficient radial mixing processes in order to distribute crystalline
grains at large distances from the central object, along with possible nebular
shocks in outer regions of disks that can thermally anneal amorphous grains
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