21 research outputs found
California Proposition 227: An Examination of the Legal, Educational and Practical Issues Surrounding the New Law
The structure, geologic evolution and regional significance of the Bethel Creek-North Fork area, Coos and Curry counties, Oregon
The original purpose of this study was a detailed structural analysis of the Jurassic Otter Point Formation in order to determine if the Canyonville Fault Zone, which forms the northern boundary of the Klamath Mountains in the Riddle - Canyonville area (Benson and Perttu, 1980), extends westward to the coast and, if possible, to characterize the structure of the Otter Point Formation. Further, a detailed examination of the structural and stratigraphic relationships between the Otter Point Formation and the Eocene Roseburg and Lookingglass Formations was to be performed in an attempt to determine the tectonic history of the area
Rethinking Retention: Using Engagement to Increase Adult Distance Learner Persistence
University of Minnesota Ph.D. dissertation. August 2015. Major: Organizational Leadership, Policy, and Development. Advisors: Rosemarie Park, Catherine Twohig. 1 computer file (PDF); viii, 92 pages.As a result of the growth in distance education, and subsequently, the growth of distance learners, it is exceedingly important, and necessary, to find ways for the institution to retain these students by identifying their needs and implementing practices that facilitate persistence (Tinto, 2012). Research shows that engagement from the institution through student services advisement (Nichols, 2010) and orientations (Braxton, et al., 2014; Nash, 2005; Radwan & Leeds, 2009; Wojciechowski & Palmer, 2005) is some of the most effective ways in which to engage, and thereby retain, students and help them persist. The retention of adult distance learners is vital to any university that depends on this population for revenue; therefore, determining the ways in which engagement assists with distance learner persistence is important for perpetuation of the institution. This study aimed to identify which engagement initiatives and practices are expected, effective, and predictive for retaining nontraditional distance learners. Identifying effective practices can help practitioners determine the ways to translate current research into effective practice for that of adult distance learners. Failure to retain any student � traditional or nontraditional - has obvious consequences, many of which are detrimental to the institution, such as reputation, loss of revenue, and cost to continuously recruit new (or more) learners. Institutional, individual, and societal benefits confirm the importance of this topic. However, it is also important to note that a higher education likely improves lives in many ways that cannot be easily quantified. Knowing this, it is necessary to identify ways to promote learner persistence and increase retention and completion
HII regions in IC 1613: The ISM in a nearby dwarf irregular galaxy
IC 1613, a nearby (725 kpc distant) dwarf irregular galaxy, has always been known to contain large, ring-shaped HII regions in its northeast corner. A new H alpha image has been obtained using the Bell Labs Charge Coupled Device (CCD) camera, an RCA 320 X 512 pixel-thinned, back-illuminated CCD, an H alpha filter of central wavelength 6562 A and width (full width half maximum) of 30 A, and the 42 inch telescope at Lowell Observatory. The low resolution images exhibit many new, faint features
VGCF Detection of Galaxy Systems at Intermediate Redshift
We continue the development of our Voronoi Galaxy Cluster Finder (VGCF)
technique by applying it to galaxy catalogs obtained with B and R band
observations of four high galactic latitude fields of 0.5x0.5 square degrees
each. These fields are deep R_lim ~23, B_lim ~26 and partially overlap the
Palomar Distant Cluster Survey (PDCS) fields at 0h and 2h. We run the VGCF also
on the original V and I bands PDCS galaxy catalogs.
We identify a total of 48 clusters that are particularly reliable being
detected in at least two bands. The analysis of color-magnitude diagrams and,
in a few cases, spectroscopic observations allow us to further increase the
reliability of 25 of the 48 clusters. For these 26 clusters we also estimate
redshifts that fall in the approximate range 0.2 < z < 0.6.
We detect 41 VGCF clusters within the strict limits of the PDCS fields at 0h
and 2h. The PDCS catalog for the same regions consists of 28 clusters. The two
catalogs have 20 clusters in common. These clusters together with the remaining
PDCS and VGCF clusters lead to a total number of 46 "independent" clusters. The
total number of clusters is therefore 20% larger than the number of VGCF
clusters and more than 60% larger than the number of PDCS clusters. These
results confirm a) that the VGCF is a competitive algorithm for the
identification of optical clusters, and b) that a combined catalog of
matched-filter and VGCF clusters constitutes a significant progress toward a
more complete selection of clusters from bidimensional optical data.Comment: 15 pages, 6 figures, accepted in A&
Cluster Abell 520: a perspective based on member galaxies. A cluster forming at the crossing of three filaments?
The connection of cluster mergers with the presence of extended, diffuse
radio sources in galaxy clusters is still debated. An interesting case is the
rich, merging cluster Abell 520, containing a radio halo. A recent
gravitational analysis has shown in this cluster the presence of a massive dark
core suggested to be a possible problem for the current cold dark matter
paradigm.
We aim to obtain new insights into the internal dynamics of Abell 520
analyzing velocities and positions of member galaxies.
Our analysis is based on redshift data for 293 galaxies in the cluster field
obtained combining new redshift data for 86 galaxies acquired at the TNG with
data obtained by CNOC team and other few data from the literature. We also use
new photometric data obtained at the INT telescope. We combine galaxy
velocities and positions to select 167 cluster members around z~0.201. We
analyze the cluster structure using the weighted gap analysis, the KMM method,
the Dressler-Shectman statistics and the analysis of the velocity dispersion
profiles. We compare our results with those from X-ray, radio and gravitational
lensing analyses.
We find that Abell 520 is definitely a very complex system. Our results
suggest that we are looking at a cluster forming at the crossing of three
filaments of the large scale structure. In particular, we detect a filament
aligned with the LOS and projected onto the center of the forming cluster. It
might explain the apparent massive dark core shown by gravitational lensing
analysis.Comment: 18 pages, 16 figures, 4 tables. Accepted for publication on A&
Detection of weak gravitational lensing distortions of distant galaxies by cosmic dark matter at large scales
Most of the matter in the universe is not luminous and can be observed
directly only through its gravitational effect. An emerging technique called
weak gravitational lensing uses background galaxies to reveal the foreground
dark matter distribution on large scales. Light from very distant galaxies
travels to us through many intervening overdensities which gravitationally
distort their apparent shapes. The observed ellipticity pattern of these
distant galaxies thus encodes information about the large-scale structure of
the universe, but attempts to measure this effect have been inconclusive due to
systematic errors. We report the first detection of this ``cosmic shear'' using
145,000 background galaxies to reveal the dark matter distribution on angular
scales up to half a degree in three separate lines of sight. The observed
angular dependence of this effect is consistent with that predicted by two
leading cosmological models, providing new and independent support for these
models.Comment: 18 pages, 5 figures: To appear in Nature. (This replacement fixes tex
errors and typos.
Supernovae without host galaxy? - Hypervelocity stars in foreign galaxies
Harvesting the SAI supernova catalog, we search for SNe that apparently do
not occur within a distinct host galaxy but lie a great distance apart from
their assigned host galaxy. Assuming two possible explanations for this
host-lessness of a fraction of reported SNe, namely (i) a host galaxy which is
too faint to be detected within the limits of currently available surveys or
(ii) a hypervelocity star (HVS) as progenitor of the SN,we want to distinguish
between these two cases. To do so, we use deep imaging to test explanation (i).
If within our detection limit of 27 mag/arcsec^2, the central surface
brightness of the faintest known LSB galaxy so far, no galaxy could be
identified, we discard this explanation and regard the SN, after several other
checks, to have had a hypervelocity star progenitor. Analyzing a selected
subsample of five host-less SNe we find one, SN 2006bx in UGC5434, to be put in
the hypervelocity progenitor category with a high probability, exhibiting a
projected velocity of > 800 km/s. SN 1969L in NGC1058 is most likely an example
for a very extended star-forming disk visible only in the far-UV, not in the
optical wavebands. Therefore this SN is clearly due to in situ star formation.
This mechanism may also apply for two other SNe we investigated (SN 1970L and
SN 1997C), but this cannot be determined with final certainty. Another one, SN
2005nc associated with a gamma-ray burst (GRB 050525), is a special case not
covered by our initial assumptions. Even with deep Hubble data, a host galaxy
could not be unambiguously identified.Comment: 11 pages, 7 figures, accepted for publication by A&A, abstract
abridged due to arXiv requirements, rev. 2 after language correction
ISO observations of 3 - 200 micron emission by three dust populations in an isolated local translucent cloud
We present ISOPHOT spectrophotometry of three positions within the isolated
high latitude cirrus cloud G 300.2 - 16.8, spanning from the near- to
far-infrared. The positions exhibit contrasting emission spectrum contributions
from the UIBs, very small grains and large classical grains, and both
semi-empirical and numerical models are presented. At all three positions, the
UIB spectrum shapes are found to be similar, and the large grain emission may
be fitted by an equilibrium temperature of ~17.5 K. The energy requirements of
both the observed emission spectrum and optical scattered light are shown to be
satisfied by the incident local ISRF. The FIR emissivity of dust in G 300.2 -
16.8 is found to be lower than in globules or dense clouds, and is even lower
than model predictions for dust in the diffuse ISM. The results suggest
physical differences in the ISM mixtures between positions within the cloud,
possibly arising from grain coagulation processes.Comment: 22 pages, 8 tables, 11 figures (figure 8 is in colour). Landscape
table included as separate LaTeX file. Accepted for publication in MNRA