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 $t \to b W$. We resolve the scale ambiguity using the Brodsky-Lepage-Mackenzie scheme, and find that the appropriate coupling constant is $\alpha_{s}^{ \overline{MS}} (0.122m_{t})$. 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 $\rho$ parameter are extremely small when the $\rho$ parameter is expressed in terms of the top quark width.Comment: 7 pages (LaTeX), TPI-MINN-94/16-T, UMN-TH-1252/9

Alterations in Multiple Measures of White Matter Integrity in Normal Women at High Risk for Alzheimer\u27s Disease

There is evidence that disruption of white matter (WM) microstructure is an early event in the course of Alzheimer\u27s disease (AD). However, the neurobiological bases of WM microstructural declines in presymptomatic AD are unknown. In the present study we address this issue using a multimodal imaging approach to the study of presymptomatic AD. Participants were 37 high-risk (both family history of dementia and one or more APOE4 alleles) women and 20 low-risk (neither family history nor APOE4) women. Groups were matched for age, education, neuropsychological performance, and vascular factors that could affect white matter. Whole-brain analyses of diffusion tensor imaging data [including fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (DA) and radial diffusivity (DR)] and volumetric comparisons of medial temporal lobe (MTL) structures were conducted. Results indicated equivalent entorhinal cortex and hippocampal volumes between risk groups. Nevertheless, the high risk group showed decreased microstructural integrity in WM tracts with direct and secondary connections to the MTL. The predominant alteration in WM integrity in the high AD-risk group was decreased FA not solely driven by either DA or DR changes alone in regions where no MD changes were observed. A second pattern observed in a smaller number of regions involved decreased FA and increased DR. These results suggest that disconnection of MTL-neocortical fiber pathways represents a very early event in the course of AD and suggest that demyelination may represent one contributing mechanism