2,008 research outputs found
History of the Pruet School of Christian Studies/Department of Religion at Ouachita Baptist University/Ouachita Baptist College (1886-2021)
This is a short history of the Religion Department/School of Christian Studies at Ouachita Baptist University. This document includes a historical overview, faculty publications, the theological and educational philosophy of the school, history of Bible-related CORE courses, curriculum, and lists of faculty/staff with some biographical information
Empirical Estimate of Lyman-alpha Escape Fraction in a Statistical Sample of Lyman-alpha Emitters
The Lyman-alpha (Lya) recombination line is a fundamental tool for galaxy
evolution studies and modern observational cosmology. However, subsequent
interpretations are still prone to a number of uncertainties. Besides numerical
efforts, empirical data are urgently needed for a better understanding of Lya
escape process. We empirically estimate the Lyman-alpha escape fraction
fesc(Lya) in a statistically significant sample of z ~ 0 - 0.3 galaxies in
order to calibrate high-redshift Lyman-alpha observations. An optical
spectroscopic follow-up of a sub-sample of 24 Lyman-alpha emitters (LAEs)
detected by GALEX at z ~ 0.2-0.3, combined with a UV-optical sample of local
starbursts, both with matched apertures, allow us to quantify the dust
extinction through Balmer lines, and to estimate the Lyman-alpha escape
fraction from the Halpha flux corrected for extinction in the framework of the
recombination theory. The global escape fraction of Lyman-alpha radiation spans
nearly the entire range of values, from 0.5 to 100 %, and fesc(Lya) clearly
decreases with increasing nebular dust extinction E(B-V). Several objects show
fesc(Lya) greater than fesc(continuum) which may be an observational evidence
for clumpy ISM geometry or for an aspherical ISM. Selection biases and aperture
size effects may still prevail between z ~ 0.2-0.3 LAEs and local starbursts,
which may explain the difference observed for fesc(Lya).Comment: 4 pages, 2 figures, accepted for publication in Astronomy and
Astrophysic
On the influence of physical galaxy properties on Lyman-alpha escape in star-forming galaxies
[abridged] Among the different observational techniques used to select
high-redshift galaxies, the hydrogen recombination line Lyman-alpha (Lya) is of
particular interest as it gives access to the measurement of cosmological
quantities such as the star formation rate of distant galaxy populations.
However, the interpretation of this line and the calibration of such
observables is still subject to serious uncertainties. Therefore, it important
to understand under what conditions the Lya line can be used as a reliable star
formation diagnostic tool. We use a sample of 24 Lya emitters at z ~ 0.3 with
an optical spectroscopic follow-up to calculate the Lya escape fraction and its
dependency upon different physical properties. We also examine the reliability
of Lya as a star formation rate indicator. We combine these observations with a
compilation of Lya emitters selected at z = 0 - 0.3 to assemble a larger
sample. The Lya escape fraction depends clearly on the dust extinction
following the relation fesc(Lya) = C(Lya) x 10^(-0.4 E(B-V) k(Lya)), but with a
shallower slope than previously reported, with k(Lya) ~ 6.67 and C(Lya) = 0.22.
However, the correlation does not follow the expected curve for a simple dust
attenuation. We explore the various mechanisms than lead to fesc(Lya) values
above the continuum extinction curve, i.e. to an enhancement of the Lya output.
We also observe that the strength of Lya and the escape fraction appear
unrelated to the galaxy metallicity. Regarding the reliability of Lya as a star
formation rate (SFR) indicator, we show that the deviation of SFR(Lya) from the
true SFR (as traced by the UV continuum) is a function of the observed SFR(UV),
which can be seen as the decrease of fesc(Lya) with increasing UV luminosity.
Moreover, we observe a redshift-dependence of this relationship revealing the
underlying evolution of fesc(Lya) with redshift.Comment: 17 pages. Accepted for publicatio
AN ANALYSIS OF REGIONAL ECONOMIC GROWTH IN THE US MIDWEST
In this paper we examine more closely some of the forces that underlie economic growth at the county level. In an effort to describe a much more comprehensive regional economic growth model, we address a variety of different growth hypotheses by introducing a large number of growth related variables. When formulating our hypotheses and specifying our growth model we make liberal use of GIS mapping software to "paint" a picture of where growth spots exist and why. Our empirical estimation indicates amenities, state and local tax burdens, population, amount of agricultural activity, and demographics have important economic growth impacts.Community/Rural/Urban Development,
The Importance of extraction protocol on the analysis of novel waste sources of lignocellulosic biomass
peer-reviewedAs the utilization and consumption of lignocellulosic biomass increases, so too will the need for an adequate supply of feedstock. To meet these needs, novel waste feedstock materials will need to be utilized. Exploitation of these novel feedstocks will require information both on the effects of solvent extraction on the succeeding analysis of potential novel feedstocks and how accurate current methodologies are in determining the composition of novel lignocellulosic feedstocks, particularly the carbohydrate and lignin fractions. In this study, the effects of solvent extraction on novel feedstocks, including tree foliage, tree bark and spent mushroom compost, with 95% ethanol, water and both
sequentially were examined. Chemical analyses were carried out to determine the moisture content, ash, extractives, post-hydrolysis sugars, Klason lignin (KL) and acid-soluble lignin (ASL) within the selected feedstocks. The result of extraction could be seen most strongly for Klason lignin, with a strong association between higher levels of Klason lignin levels and greater amounts of non-removed extractives (tree foliage and bark). Higher Klason lignin levels are reported to be due the condensation of non-removed extractives during hydrolysis, hence the lower Klason lignin determinations following extraction are more exact. In addition, total sugar determinations were lower following extractions. This is because of the solubility of non-cell-wall carbohydrates; thus,
the determinations following extraction are more accurate representations of structural cell-wall polysaccharides such as cellulose. Such determinations will assist in determining the best way to utilize novel feedstocks such as those analyzed in this work
The escape of Lyman photons from a young starburst: the case of Haro 11
(Abridged) Lyman-alpha (Lya) is a dominant probe of the galaxy population at
high-z. However, interpretation of data drawn from Lya alone hinges on the Lya
escape fraction which, due to the complex radiative transport, may vary
greatly. Here we map the Lya emission from local starburst Haro 11, a Lya
emitter and the only known candidate for low-z Lyman continuum emission (LyC).
To aid in the interpretation we perform a detailed multi-wavelength analysis
and model the stellar population, dust distribution, ionising photon budget,
and star-cluster population. We use archival X-ray observations to further
constrain properties of the starburst and estimate the HI column density.
The Lya morphology is found to be strongly decoupled from stellar and nebular
(H-alpha) morphologies. General surface photometry finds only very slight
correlation between Lya and H-halpha, E(B-V), and stellar age. Only around the
central Lya-bright cluster do we find the Lya/Ha ratio at values predicted by
recombination theory. The total Lya escape fraction is found to be just 3%. We
compute that ~90% of the Lya photons that escape do so after undergoing
multiple resonance scattering events, masking their point of origin. This leads
to a largely symmetric distribution and, by increasing the distance that
photons must travel to escape, decreases the escape probability significantly.
While dust must ultimately be responsible for the destruction of Lya, it plays
little role in governing the observed morphology, which is regulated more by
ISM kinematics and geometry. We find tentative evidence for local Lya
equivalent width in the immediate vicinity of star-clusters being a function of
cluster age, consistent with hydrodynamic studies. We estimate the ionising
photon production and further constrain the escape fraction at 900 AA to <~9% .Comment: In press for MNRAS. 18 pages, 9 figures. Version with full resolution
images to be found at
http://www.astro.su.se/~matthew/english/papers/hayes_lya_haro11_hires.pd
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Androgen receptor as a mediator and biomarker of radioresistance in triple-negative breast cancer.
Increased rates of locoregional recurrence have been observed in triple-negative breast cancer despite chemotherapy and radiation therapy. Thus, approaches that combine therapies for radiosensitization in triple-negative breast cancer are critically needed. We characterized the radiation therapy response of 21 breast cancer cell lines and paired this radiation response data with high-throughput drug screen data to identify androgen receptor as a top target for radiosensitization. Our radiosensitizer screen nominated bicalutamide as the drug most effective in treating radiation therapy-resistant breast cancer cell lines. We subsequently evaluated the expression of androgen receptor in >2100 human breast tumor samples and 51 breast cancer cell lines and found significant heterogeneity in androgen receptor expression with enrichment at the protein and RNA level in triple-negative breast cancer. There was a strong correlation between androgen receptor RNA and protein expression across all breast cancer subtypes (R2â=â0.72, pâ<â0.01). In patients with triple-negative breast cancer, expression of androgen receptor above the median was associated with increased risk of locoregional recurrence after radiation therapy (hazard ratio for locoregional recurrence 2.9-3.2)) in two independent data sets, but there was no difference in locoregional recurrence in triple-negative breast cancer patients not treated with radiation therapy when stratified by androgen receptor expression. In multivariable analysis, androgen receptor expression was most significantly associated with worse local recurrence-free survival after radiation therapy (hazard ratio of 3.58) suggesting that androgen receptor expression may be a biomarker of radiation response in triple-negative breast cancer. Inhibition of androgen receptor with MDV3100 (enzalutamide) induced radiation sensitivity (enhancement ratios of 1.22-1.60) in androgen receptor-positive triple-negative breast cancer lines, but did not affect androgen receptor-negative triple-negative breast cancer or estrogen-receptor-positive, androgen receptor-negative breast cancer cell lines. androgen receptor inhibition with MDV3100 significantly radiosensitized triple-negative breast cancer xenografts in mouse models and markedly delayed tumor doubling/tripling time and tumor weight. Radiosensitization was at least partially dependent on impaired dsDNA break repair mediated by DNA protein kinase catalytic subunit. Our results implicate androgen receptor as a mediator of radioresistance in breast cancer and identify androgen receptor inhibition as a potentially effective strategy for the treatment of androgen receptor-positive radioresistant tumors
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Remote sensing for monitoring regional carbon dynamics associated with land cover and land use change along the Mesoamerican Biological Corridor
Human activities are causing profound changes to the global environment, yet the potential consequences of these changes on rising atmospheric carbon dioxide and climate change are not well understood. Improving our understanding of these processes requires an enhanced awareness of how global ecosystems are changing and how these changes affect the global carbon cycle. Tropical ecosystems are considered crucial to the global carbon budget, and more reliable data on the rates and extent of land cover and land use changes in these ecosystems are needed to reduce the uncertainty of global carbon flux estimates. Spatially explicit and repeatable observations from remotely sensed data offer the best opportunity for monitoring the rapid changes taking place over large spatial scales in tropical ecosystems. As an important regional case study among global-wide efforts to understand land cover and land use change and its effects on terrestrial carbon dynamics, the objective of this research was to develop and test models based on high temporal frequency MODIS data for monitoring land cover changes and modeling associated carbon flux over tropical Central America. The first chapter introduces the issue involved with the development of a methodology for scaling observations of changes in tropical forest cover to large areas at high temporal frequency from coarse resolution satellite imagery. The approach for estimating proportional forest cover change as a continuous variable was based on a regression model that relates multi-spectral, multi-temporal MODIS data, transformed to optimize the spectral detection of vegetation changes, to reference change data sets derived from a Landsat data record for an individual study site. Chapter 2 reports on a series of fundamental analyses designed to test and compare the utility of various MODIS data and products for expanding the forest cover change models over multiple study sites and time periods. The study described in Chapter 3 integrates satellite-derived data sets on land cover and land use change with field-based parameters on terrestrial carbon stocks and flux in a simple accounting model to track carbon dynamics associated with these changes
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