Shock Tube Study of the Effects of Large Density Differences and Blowing Ratio on Heat Transfer to a Film-Cooled Flat Plate

The effects of coolant-to-mainstream density ratio (D.R.) and mass flux (blowing) ratio (Mb) on flat plate heat transfer were investigated in a shock tube. The round-nosed plate has a single row of holes inclined 35° downstream with two-diameter lateral spacing and hole length of three diameters. Mixing helium with air in the shock tube produced a D.R. range of 1.2 to 2.1. The parameters studied approach those of film-cooled turbine components. For an Mb range of 0.4 to 3 and 10% mainstream turbulence, heat flux was measured with thin-film heat flux gauges located 4 to 30 hole diameters downstream of the cooling holes using an electrical analog. Various flow conditions were produced over the flat plate. The \u27steady\u27 portion of turbulent flow heat transfer data compared within 20% of the theoretical flat plate solution. Ratios of heat flux with cooling to heat flux without cooling versus M. and D.R. were determined. Analysis of the results showed film cooling heat transfer is correlated by coolant-to-mainstream velocity ratio. Effectiveness of cooling was reduced by the high mainstream turbulence

Factors affecting flea densities in prairie dog colonies: implications for the maintenance and spread of plague

2014 Fall.Plague is a re-emerging, rodent-associated disease caused by the primarily flea-borne bacterium Yersinia pestis. The bacterium likely originated 1,500-20,000 years ago in Asia but has been transported by humans to multiple additional continents and islands where it degrades populations of a wide array of rodents. In the western United States, there is an urgent need to acquire a deeper understanding of plague because over half the rodent species of conservation concern occur within its introduced range. This dissertation describes research on fleas in colonies of black-tailed prairie dogs (Cynomys ludovicianus), colonial rodents that amplify Y. pestis in the Great Plains. Adult fleas were combed from live-trapped prairie dogs during June-August 2010-2012 in the short-grass prairie of Vermejo Park Ranch, New Mexico, USA. We evaluated correlations between flea densities and the attributes of soils, prairie dog colonies, and weather. Adult fleas were most abundant in portions of prairie dog colonies with coarse surface-soils and moderately textured subsurface-soils. Coarse surface-soils may allow precipitation to infiltrate to the depth of prairie dog nests, where the moisture could create humid microclimates that are preferred by fleas. Inside burrows, moderately textured soils may hold considerable amounts of water, some of which could evaporate into prairie dog nests, thereby creating humid microclimates. Although fleas tend to fare best under humid conditions, they were scarce in areas with very wet subsurface-soils, presumably because sodden soils can facilitate the accumulation of fungi and mites, some of which are lethal to fleas. We also studied the abundance of fleas in old colonies (initially 8-11 years-old) and young colonies (3-6 years). Fleas were 110% more abundant in old colonies and their abundance was positively correlated with the number of years since a colony was established. Fleas may accumulate to high densities in old colonies because prairie dogs have created deep burrows there, and deep burrows provide ectothermic fleas with humid microclimates and stable temperatures. Moreover, older burrows presumably contain a wealth of organic matter upon which flea larvae feed. Fleas desiccate under dry conditions and, consequently, their densities are thought to decline during droughts. At Vermejo, February-June precipitation was relatively plentiful in 2010 and 2012 but scarce in 2011, the driest spring-summer on record for New Mexico. Unexpectedly, fleas were 250% more abundant in 2011 than in other years. During the dry 2011 field season, prairie dogs were in poor condition and devoted little time to grooming. In contrast, during 2010 and 2012, prairie dogs were in 27% better condition and, when controlling for month and observer variation, devoted 450% more time to grooming. Prairie dogs provided with supplemental food and water during March-May 2012 were in 18% better condition and carried 40% fewer fleas during June-August. Increased flea densities during droughts may provide context for the maintenance and spread of plague. Three additional studies are presented herein. First, we developed a new method for combing fleas from hosts. The method and resulting data can be used with occupancy models to estimate prevalence rates for ectoparasites while accounting for imperfect detection. Second, we used the combing new method to estimate prevalence rates for the generalist flea Pulex simulans during June-August 2012. Prevalence estimates were >30% higher than indices from studies with substantial sample sizes for prairie dogs. If P. simulans can attain high prevalence on prairie dogs, the species may commonly serve as a bridge vector between Cynomys and other mammalian hosts of Y. pestis, and even function as a reservoir of plague. Third, a case study is presented to describe how Y. pestis can transform grassland ecosystems by devastating populations of prairie dogs and, thereby, causing (1) declines in native species abundance and diversity, including threatened and endangered forms, (2) alterations in food web connections, (3) alterations in the import/export of nutrients, (4) loss of ecosystem resilience to encroaching invasive plants, and (5) modifications of prairie dog burrows

Practice continuation agreements : a practice survival kit

https://egrove.olemiss.edu/aicpa_guides/1315/thumbnail.jp

The Effects of Parental Age and Housing Type on the Reproductive Success of the Purple Martin (\u3cem\u3eProgne subis subis\u3c/em\u3e)

The reproductive success of the Purple Martin is dependent upon many factors. This study measured reproductive success of the Purple Martin (Progne subis subis) based on parental age and type of housing used. Reproductive parental ages consist of adults (experienced breeders) and subadults (first time breeders). Housing types included in this study were aluminum housing, wooden housing, plastic gourds, natural gourds, SuperGourds, and mailbox housing. The reproductive success was defined as the percentage of the original clutch that fledged. Study sites were located in Alabama, Indiana, North Carolina, Oklahoma, Tennessee, and Virginia. Pairs mating nonassortatively by age group had lower reproductive success than adults and subadults that were paired assortatively. Purple Martins were the most reproductively successful in SuperGourds and the least reproductively successful in wooden housing. This study provides evidence that may be basis for further research, help support the conservation of the Purple Martin, and aid reproductive success on its breeding grounds

Epigenetics as a mechanism driving polygenic clinical drug resistance

Aberrant methylation of CpG islands located at or near gene promoters is associated with inactivation of gene expression during tumour development. It is increasingly recognised that such epimutations may occur at a much higher frequency than gene mutation and therefore have a greater impact on selection of subpopulations of cells during tumour progression or acquisition of resistance to anticancer drugs. Although laboratory-based models of acquired resistance to anticancer agents tend to focus on specific genes or biochemical pathways, such 'one gene : one outcome' models may be an oversimplification of acquired resistance to treatment of cancer patients. Instead, clinical drug resistance may be due to changes in expression of a large number of genes that have a cumulative impact on chemosensitivity. Aberrant CpG island methylation of multiple genes occurring in a nonrandom manner during tumour development and during the acquisition of drug resistance provides a mechanism whereby expression of multiple genes could be affected simultaneously resulting in polygenic clinical drug resistance. If simultaneous epigenetic regulation of multiple genes is indeed a major driving force behind acquired resistance of patients' tumour to anticancer agents, this has important implications for biomarker studies of clinical outcome following chemotherapy and for clinical approaches designed to circumvent or modulate drug resistance

Search for a Narrow ttbar Resonance in ppbar Collisions at sqrt{s}=1.96 TeV

We report a search for a narrow ttbar resonance that decays into a lepton+jets final state based on an integrated luminosity of 5.3/fb of proton-antiproton collisions at sqrt{s}=1.96 TeV collected by the D0 Collaboration at the Fermilab Tevatron Collider. We set upper limits on the production cross section of such a resonance multiplied by its branching fraction to ttbar which we compare to predictions for a leptophobic topcolor Z' boson. We exclude such a resonance at the 95% confidence level for masses below 835 GeV.Comment: 7 pages, 3 figures, submitted to Physical Review Letter

Search for the Higgs boson in lepton, tau and jets final states

We present a search for the standard model Higgs boson in final states with an electron or muon and a hadronically decaying tau lepton in association with two or more jets using 9.7 fb^{-1} of Run II Fermilab Tevatron Collider data collected with the D0 detector. The analysis is sensitive to Higgs boson production via gluon fusion, associated vector boson production, and vector boson fusion, followed by the Higgs boson decay to tau lepton pairs or to W boson pairs. The ratios of 95% C.L. upper limits on the cross section times branching ratio to those predicted by the standard model are obtained for orthogonal subsamples that are enriched in either H -> tau tau decays or H -> WW decays, and for the combination of these subsample limits. The observed and expected limit ratios for the combined subsamples at a Higgs boson mass of 125 GeV are 11.3 and 9.0 respectively

Precise measurement of the top quark mass in the dilepton channel at D0

We measure the top quark mass (mt) in ppbar collisions at a center of mass energy of 1.96 TeV using dilepton ttbar->W+bW-bbar->l+nubl-nubarbbar events, where l denotes an electron, a muon, or a tau that decays leptonically. The data correspond to an integrated luminosity of 5.4 fb-1 collected with the D0 detector at the Fermilab Tevatron Collider. We obtain mt = 174.0 +- 1.8(stat) +- 2.4(syst) GeV, which is in agreement with the current world average mt = 173.3 +- 1.1 GeV. This is currently the most precise measurement of mt in the dilepton channel.Comment: 7 pages, 4 figure