Because minorities typically fare poorly on standardized tests, job testing is thought to pose an equality-efficiency trade-off: testing improves selection but reduces minority hiring. We develop a conceptual framework to assess when this trade-off is likely to apply and evaluate the evidence for such a trade-off using hiring and productivity data from a national retail firm whose 1,363 stores switched from informal to test-based worker screening over the course of one year. We document that testing yielded more productive hires at this firm-raising mean and median tenure by 10% or more. Consistent with prior research, minorities performed worse on the test. Yet, testing had no measurable impact on minority hiring, and productivity gains were uniformly large among minority and nonminority hires. These results suggest that job testing raised the precision of screening without introducing additional negative information about minority applicants, most plausibly because both the job test and the informal screen that preceded it were unbiased.

No abstract

A rapidly expanding body of evidence indicates that cytokines do indeed regulate pituitary hormone secretion. Recent studies with cytokines in vivo and in vitro support the idea that cytokines are the principal mediators of the neuroendocrine responses previously observed in infectious and inflammatory states. The dominant route of this modulation appears to be via the brain and hypothalamus, although a role for direct effects on the pituitary has not been excluded. These effects may be mediated by circulating cytokines, endogenously produced cytokines, or both. A number of receptor systems and second messengers may be involved, and a role for arachidonate metabolite pathways appears particularly likely. A final question: Of what use to the organism is the ability of immune activation to control pituitary hormone secretion? For some pituitary secretions there is a reasonable basis for speculation. Glucocorticoids serve to limit the severity of immune responses and recent studies argue that defects in this pathway permit the expression of autoimmune disease. Inhibition of thyroid function may limit the catabolic side effects of infectious illness. Stimulation of growth hormone could have the same effect, and growth hormone and prolactin may serve to enhance some immune responses.

Interleukin-1 (IL-1), a secretory product of activated macrophages and many other cell types, is an important mediator of the acute phase reaction to infection and to endotoxin administration. Previous reports that GH and TSH secretion are decreased following injection of endotoxin or IL-1 led us to test the hypothesis that IL-1 acts by releasing increased amounts of somatostatin (SS), a hypothalamic factor inhibitory of both GH and TSH release. Primary cultures of dispersed fetal rat diencephalic cells were found to contain increasing amounts of immunoreactive SS in both cells and media after addition of recombinant human IL-1 beta. This increase was detectable at 24 hours and continued for up to 6 days, the longest time interval tested. Increased content of SS peptide was accompanied by marked increases in SS mRNA. These changes were dose-related, the lowest effective dose being 10(-10) M. In contrast to the long term response, exposure of the cells to IL-1 beta for one hour had only minimal stimulating effects on somatostatin release. These data indicate that IL-1 beta is neurotrophic for the somatostatinergic neuron, an action that may be responsible at least in part, for the neuroendocrine response to infection.

No abstract

No abstract

A linear deterministic simulation model was developed to examine the historical rate of movement of the boll weevil, Anthonomus grandis grandis Boheman, across the southeastern United States. This manuscript addresses the hypotheses proposed during the initial invasion of the boll weevil that cotton production and prevailing winds were the primary factors regulating movement of this pest. A modification of the historical model was used to predict defensive strategies required to maintain boll weevil-free areas resulting from the current program efforts. KEY A boll weevil eradication program was begun in North Carolina in 1978 and was extended through South Carolina in 1983. By the end of 1986 the success of the program in the Carolinas was evident because the only areas with significant boll weevil populations were in the buffer zone, an area approximately 150 km wide in South Carolina along the Georgia border (USDA-APHIS 1986).Bottrell (1976) stated that a major shortcoming of an earlier eradication effort was the lack of attention toward practices required to maintain boll weevil-free areas upon the successful completion of the experiment. This manuscript describes a model developed to simulate the historical dispersal of the boll weevil from western Louisiana through North Carolina. A modification of this historical model is then used to predict the timing and degree of induced mortality required to maintain boll weevil-free areas resulting from the current eradication program. Predictions are based on the potential for reinfestation under several control I Department of Entomology, Clemson University, Clemson, S.c. 29634-0365.• Correspondence regarding this manuscript, or requests for copies of the model should be addressed to J. Culin. Requests for copies of the model, for both historic and current conditions, should be accompanied by a blank diskette (5Y," or 3~").8 Department of Entomology, Auburn University, Auburn, Ala. 36849., Entomology Branch, Department of Primary Industries, Kingaroy, Queensland. Australia 4610.• Division of Computing and Information Technology, Information Systems Development, Clemson University, Clemson, S.c. 29634.• (Fig. 1). These were located approximately 50, 200, and 350 km from the coast. The annual distance the infestation moved from its position in 1903 along each of these transects was measured, and the relationship between distance moved and time was investigated by regression analysis using pooled data from the three transects (PROC GLM, SAS Institute 1985b, 433-506). The Cotton Belt states east of Texas were used in developing the model because infestation fronts in Texas were such that accurate distance measurements could not be made on either the 200 or 350 km transects.The relationship between the distance moved and time is almost entirely linear (Fig. 2). The coefficient of determination (r 2 ) from the linear regression was 0.9594 with the slope of the regression line indicating that the front advanced at a rate of 95.26 ± 5.14 km (x ± 95% CL) per yea...

Increasing concerns about climate change have encouraged interest in zero-CO2 emission hydrocarbon combustion techniques. In one approach, nitrogen is removed from the combustion air and replaced with another diluent, typically carbon dioxide or steam. In this way, formation of nitrogen oxides is prevented and the exhaust stream can be separated into concentrated CO2 and water by a simple condensation process. The concentrated CO2 stream can then be sequestered or used for enhanced oil recovery. Burning fuels in an O2/CO2 diluent raises new combustion opportunities and challenges for both emissions and operability: this study focuses on the latter aspect. CH4/O2/CO2 flames have slower chemical kinetics than methane-air flames and as such, flame stability is more problematic as they are easier to blow off. This issue was investigated experimentally by characterizing the stability boundaries of a swirl stabilized combustor. Near stoichiometric CO2 and N2 diluted methane/oxygen flames were considered and compared with lean methane/air flames. Numerical modeling of chemical kinetics was also performed to analyze the dependence of laminar flame speeds and extinction strain rates upon dilution by different species and to develop correlations for blowoff boundaries. Finally, blowoff trends at high pressure were extrapolated from atmospheric pressure data to simulate conditions closer to those of gas turbines.