6,584 research outputs found
Wage and Occupational Differences Between Black and White Men: Labor Market Discrimination in the Rural South
The existence of labor market discrimination based on race is well established.However, study continues into a variety of aspects of discrimination-among them the extent to which it exists in different regions. Gwartney has estimated the ratio of black to white earnings to be between .83 and .88 for the North and between .68 and .74 for the South. Masters, in a study of earnings differentials between black and white men, found a ratio of .79 for the non-South and .69 for the South. Although considerable literature has developed concerning earnings differentials, wage discrimination in rural areas is one topic which has received relatively little attention. In an attempt to eliminate this oversight this paper concentrates on the extent of wage differences between black and white men in the rural South attributable to labor market discrimination
Validating Semi-Analytic Models of High-Redshift Galaxy Formation using Radiation Hydrodynamical Simulations
We use a cosmological hydrodynamic simulation calculated with Enzo and the
semi-analytic galaxy formation model (SAM) GAMMA to address the chemical
evolution of dwarf galaxies in the early universe. The long-term goal of the
project is to better understand the origin of metal-poor stars and the
formation of dwarf galaxies and the Milky Way halo by cross-validating these
theoretical approaches. We combine GAMMA with the merger tree of the most
massive galaxy found in the hydrodynamic simulation and compare the star
formation rate, the metallicity distribution function (MDF), and the
age-metallicity relationship predicted by the two approaches. We found that the
SAM can reproduce the global trends of the hydrodynamic simulation. However,
there are degeneracies between the model parameters and more constraints (e.g.,
star formation efficiency, gas flows) need to be extracted from the simulation
to isolate the correct semi-analytic solution. Stochastic processes such as
bursty star formation histories and star formation triggered by supernova
explosions cannot be reproduced by the current version of GAMMA. Non-uniform
mixing in the galaxy's interstellar medium, coming primarily from
self-enrichment by local supernovae, causes a broadening in the MDF that can be
emulated in the SAM by convolving its predicted MDF with a Gaussian function
having a standard deviation of ~0.2 dex. We found that the most massive galaxy
in the simulation retains nearby 100% of its baryonic mass within its virial
radius, which is in agreement with what is needed in GAMMA to reproduce the
global trends of the simulation.Comment: 26 pages, 13 figures, 2 tables, submitted to ApJ (version 2
Continuous phase stabilization and active interferometer control using two modes
We present a computer-based active interferometer stabilization method that
can be set to an arbitrary phase difference and does not rely on modulation of
the interfering beams. The scheme utilizes two orthogonal modes propagating
through the interferometer with a constant phase difference between them to
extract a common phase and generate a linear feedback signal. Switching times
of 50ms over a range of 0 to 6 pi radians at 632.8nm are experimentally
demonstrated. The phase can be stabilized up to several days to within 3
degrees.Comment: 3 pages, 2 figure
Recommendations for Future Efforts in RANS Modeling and Simulation
The roadmap laid out in the CFD Vision 2030 document suggests that a decision to move away from RANS research needs to be made in the current timeframe (around 2020). This paper outlines industry requirements for improved predictions of turbulent flows and the cost-barrier that is often associated with reliance on scale resolving methods. Capabilities of RANS model accuracy for simple and complex flow flow fields are assessed, and modeling practices that degrade predictive accuracy are identified. Suggested research topics are identified that have the potential to improve the applicability and accuracy of RANS models. We conclude that it is important that some part of a balanced turbulence modeling research portfolio should include RANS efforts
Early Olfactory, but not Gustatory Processing, is Affected by the Selection of Heritable Cognitive Phenotypes in Honey Bee
Associative learning enables animals to predict rewards or punishments by their associations with predictive stimuli, while non-associative learning occurs without reinforcement. The latter includes latent inhibition (LI), whereby animals learn to ignore an inconsequential ‘familiar’ stimulus. Individual honey bees display heritable differences in expression of LI. We examined the behavioral and neuronal responses between honey bee genetic lines exhibiting high and low LI. We observed, as in previous studies, that high LI lines learned a familiar odor more slowly than low LI bees. By measuring gustatory responses to sucrose, we determined that perception of sucrose reward was similar between both lines, thereby not contributing to the LI phenotype. We then used extracellular electrophysiology to determine differences in neural responses of the antennal lobe (AL) to familiar and novel odors between the lines. Low LI bees responded significantly more strongly to both familiar and novel odors than the high LI bees, but the lines showed equivalent differences in response to the novel and familiar odors. This work suggests that some effects of genotype are present in early olfactory processing, and those effects could complement how LI is manifested at later stages of processing in brains of bees in the different lines
Normalization of QCD corrections in top quark decay
We discuss the effects of QCD corrections to the on-shell decay .
We resolve the scale ambiguity using the Brodsky-Lepage-Mackenzie scheme, and
find that the appropriate coupling constant is . The largest long distance contribution comes from the definition
of the on-shell mass of the top quark. We note that QCD corrections to the
electroweak parameter are extremely small when the parameter is
expressed in terms of the top quark width.Comment: 7 pages (LaTeX), TPI-MINN-94/16-T, UMN-TH-1252/9
IL-21 receptor expression in human tendinopathy
The pathogenetic mechanisms underlying tendinopathy remain unclear,
with much debate as to whether inflammation or degradation has the prominent
role. Increasing evidence points toward and early inflammatory infiltrate and
associated inflammatory cytokine production in human and animal models of
tendon disease.
The IL-21/IL-21R axis is a proinflammatory cytokine complex that has
been associated with chronic inflammatory diseases including rheumatoid
arthritis and inflammatory bowel disease. This project aimed to investigate the
role and expression of the cytokine/receptor pair IL-21/IL-21R in human
tendinopathy.
We found significantly elevated expression of IL-21 receptor message and
protein in human tendon samples but found no convincing evidence of the
presence of IL-21 at message or protein level. The level of expression of IL-21R
message/protein in human tenocytes was significantly up regulated by
proinflammatory cytokines (TNFα/IL-1β) in vitro.
These findings demonstrate that IL-21R is present in early human
tendinopathy mainly expressed by tenocytes and macrophages. Despite a lack of
IL-21 expression these data again suggest that early tendinopathy has an
inflammatory/cytokine phenotype, which may provide novel translational targets
in the treatment of tendinopathy
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