Chesapeake Energy

About: Chesapeake Energy is a based out in . It is known for research contribution in the topics: Population & Prostate cancer. The organization has 1367 authors who have published 1345 publications receiving 30351 citations.

Routes of Infection, Viremia, and Liver Disease in Blood Donors Found to Have Hepatitis C Virus Infection

Abstract: Background For many people infected with the hepatitis C virus (HCV), the route of exposure, risk of transmission, and severity of associated liver disease are unknown. We studied these variables in people who donated blood voluntarily. Methods Blood donors who tested positive for HCV antibodies on enzyme immunoassay were classified according to whether the results of a confirmatory second-generation recombinant immunoblot assay (RIBA) for HCV were positive, negative, or indeterminate. The evaluations also included an assessment of risk factors, a physical examination, serial determinations of alanine aminotransferase levels and HCV serologic assays, a polymerase-chain-reaction assay for HCV RNA, testing of sexual contacts and family members, and liver biopsies in some participants who were HCV-positive by RIBA. Results A total of 481 donors were studied, among whom 248 were positive for HCV by RIBA, 102 had indeterminate results, and 131 were HCV-negative. In a logistic-regression analysis, significant r...

Inputs, transformations, and transport of nitrogen and phosphorus in Chesapeake Bay and selected tributaries

Abstract: In this paper we assemble and analyze quantitative annual input-export budgets for total nitrogen (TN) and total phosphorus (TP) for Chesapeake Bay and three of its tributary estuaries (Potomac, Patuxent, and Choptank rivers). The budgets include estimates of TN and TP sources (point, diffuse, and atmospheric), internal losses (burial in sediments, fisheries yields, and denitrification), storages in the water column and sediments, internal cycling rates (zooplankton excretion and net sediment-water flux), and net downstream exchange. Annual terrestrial and atmospheric inputs (average of 1985 and 1986 data) of TN and TP ranged from 4.3 g TN m−2 yr−1 to 29.3 g TN m−2 yr−1 and 0.32 g TP m−2 yr−1 to 2.42 g TP m−2 yr−1, respectively. These rates of TN and TP input represent 6-fold to 8-fold and 13-fold to 24-fold increases in loads to these systems since the precolonial period. A recent 11-yr record for the Susquehanna River indicates that annual loads of TN and TP have varied by about 2-fold and 4-fold, respectively. TN inputs increased and TP inputs decreased during the 11-yr period. The relative importance of nutrient sources varied among these estuaries: point sources of nutrients delivered about half the annual TN and TP load to the Patuxent and nearly 60% of TP inputs to the Choptank; diffuse sources contributed 60–70% of the TN and TP inputs to the mainstream Chesapeake and Potomac River. The direct deposition of atmospheric wet-fall to the surface waters of these estuaries represented 12% or less of annual TN and TP loads except in the Choptank River (37% of TN and 20% of TP). We found direct, although damped, relationships between annual rates of nutrient input, water-column and sediment nutrient stocks, and nutrient losses via burial in sediments and denitrification. Our budgets indicate that the annual mass balance of TN and TP is maintained by a net landward exchange of TP and, with one exception (Choptank River), a net seaward transport of TN. The budgets for all systems revealed that inorganic nutrients entering these estuaries from terrestrial and atmospheric sources are rapidly converted to particulate and organic forms. Discrepancies between our budgets and others in the literature were resolved by the inclusion of sediments derived from shoreline erosion. The greatest potential for errors in our budgets can be attributed to the absence of or uncertainties in estimates of atmospheric dry-fall, contributions of nutrients via groundwater, and the sedimentation rates used to calculate nutrient burial rates.

Mineralogy of a Mudstone at Yellowknife Bay, Gale Crater, Mars

Abstract: Sedimentary rocks at Yellowknife Bay (Gale crater) on Mars include mudstone sampled by the Curiosity rover. The samples, John Klein and Cumberland, contain detrital basaltic minerals, calcium sulfates, iron oxide or hydroxides, iron sulfides, amorphous material, and trioctahedral smectites. The John Klein smectite has basal spacing of similar to 10 angstroms, indicating little interlayer hydration. The Cumberland smectite has basal spacing at both similar to 13.2 and similar to 10 angstroms. The larger spacing suggests a partially chloritized interlayer or interlayer magnesium or calcium facilitating H2O retention. Basaltic minerals in the mudstone are similar to those in nearby eolian deposits. However, the mudstone has far less Fe-forsterite, possibly lost with formation of smectite plus magnetite. Late Noachian/Early Hesperian or younger age indicates that clay mineral formation on Mars extended beyond Noachian time.

Development of Visual Preference for Natural Environments

Abstract: Human visual preferences for slides of five natural landscapes or biomes-tropical rain forest, temperate deciduous forest, coniferous forest, savanna, and desert-were examined. Subjects were third graders, sixth graders, ninth graders, college students, adults, senior citizens, and a group of professional foresters. A series of 20 slides, 4 examples of each biome, was shown twice to each group of subjects. On one pass through the slides, subjects judged how much they would like to live in an area similar to the one represented; on the other pass, subjects rated the slides for how much they would like to visit an area similar to the one shown. Judgments were made on a 6-point Likert scale. Elementary schoolchildren showed a significant preference for savanna over all other biomes. From midadolescence and through adulthood, more familiar natural environments were equally preferred to savanna. Results were interpreted as providing limited support for the hypothesis that humans have an innate preference for s...