Polyparameter linear free energy models for polyacrylate fiber-water partition coefficients to evaluate the efficiency of solid-phase microextraction

The fiber-water partition coefficient, K(fw), is decisive for performance of solid-phase microextraction (SPME) techniques in organic chemical analyses. In this study, polyacrylate (PA)-coated fiber was evaluated for its K(fw) values toward diverse neutral organic compounds. Literature K(fw) data were thoroughly evaluated, and additional K(fw) values for 69 compounds were measured in phosphate-buffered saline (PBS) solution at 37 °C. These K(fw) data, spanning over 6 orders of magnitude, were used to construct polyparameter linear free energy relationship (PP-LFER) models. The PP-LFER models fit well to the data with a standard deviation of 0.15-0.23 log units. Additional experiments indicated that the differences in temperature (25 vs 37 °C), electrolyte concentrations (pure water vs PBS), and conditioning methods (heat vs methanol) had only minor influences (<0.3 log units) on K(fw). Using the established PP-LFERs, the SPME extraction efficiency of PA coating toward compounds of differing polarity was evaluated in comparison to poly(dimethylsiloxane) (PDMS) coating. PA exhibited higher extraction capacities for H-bond donor compounds (e.g., phenols, anilines, amides, and many drugs and pesticides) with the estimated K(fw) values being 1-4 log units higher than those of PDMS. Also, PA was shown to be more efficient than PDMS for hydrophobic aromatic compounds.     

Team task analysis: identifying tasks and jobs that are team based

This paper presents initial information on the development and validation of three team task analysis scales. These scales were designed to quantitatively assess the extent to which a group of tasks or a job is team based. During a 2-week period, 52 male students working in 4-person teams were trained to perform a complex highly interdependent computer-simulated combat mission consisting of both individual- and team-based tasks. Our results indicated that the scales demonstrated high levels of interrater agreement. In addition, the scales differentiated between tasks that were predetermined to be individual versus team based. Finally, the results indicated that job-level ratings of team workflow were more strongly related to team performance than were aggregated task-level ratings of team-relatedness or team workflow. These results suggest that the scales presented here are an effective means of quantifying the extent to which tasks or jobs are team based. A research and practical implication of our findings is that the team task analysis scales could serve as criterion measures in the evaluation of team training interventions or predictors of team performance.     

Physical structures of lipid layers on pyrite

The physical structures of lipid layers on pyrite (FeS2), a ubiquitous sulfide mineral, were studied in air and in water by atomic force microscopy (AFM). Egg PC, a phospholipid that forms bilayer structures on atomically flat substrates, was investigated, and our experimental observations show that this lipid formed bilayers on an atomically rough pyrite surface, as inferred by a measured layer thickness of 5.0 +/- 0.2 nm. The surface coverage of the lipid coating increased from approximately 15% to 80% when the concentration of the lipid suspension was increased from 0.014 to 0.15 mM. Although further increases up to 1.5 mM resulted in an incremental increase in surface coverage of only 5%, multilayer structures of 20- to 40-nm height formed on top of the first bilayer. The findings provide a structural explanation for the results of earlier kinetic studies showing that the presence of the lipid decreases the rate of pyrite oxidation in air and in water. Lipid coatings applied to iron-sulfide bearing minerals are a possible approach to preventing oxidation and acidification and thereby mitigating environmental damage that can result from acid mine drainage.     

油页岩综合利用途径探讨

某煤矿含有大量的油页岩,属煤系高岭岩系列.根据油页岩的鉴定结果和实验室初步试验研究,认为可以利用该油页岩干馏脱水后生成的偏高岭石,作为生产高强混凝土的添加剂;也可以经过脱除显色物质后,制取高附加值的优质高岭土产品或深加工生产高质量的白炭黑及铝盐等产品.综合利用油页岩资源,是该煤矿可持续发展必须解决的重要问题.     

Extended ceftiofur therapy for treatment of experimentally-induced Streptococcus uberis mastitis in lactating dairy cattle

Streptococcus uberis is an important cause of mastitis in dairy cows throughout the world, particularly during the dry period, the period around calving, and during early lactation. Strategies for controlling Strep. uberis mastitis are poorly defined and are currently inadequate. Objectives of the present study were to evaluate efficacy of ceftiofur, a new broad-spectrum cephalosporin antibiotic, for treatment of experimentally induced Strep. uberis intramammary infections (IMI) in lactating dairy cows during early lactation and to determine whether extended therapy regimens enhanced efficacy of ceftiofur. Efficacy of extended ceftiofur intramammary therapy regimens was investigated in 37 mammary quarters of 23 dairy cows that developed clinical mastitis following experimental infection with Strep. uberis during early lactation. Cows that developed clinical mastitis during the challenge period were allocated randomly to 3 groups representing 3 different ceftiofur treatment regimens: 2-d (n = 7 mammary quarters), 5-d (n = 16 mammary quarters), and 8-d (n = 14 mammary quarters) treatment regimens. For all groups, 125 mg of ceftiofur hydrochloride was administered via intramammary infusion. A bacteriological cure was defined as an experimentally infected quarter that was treated and was bacteriologically negative for the presence of Strep. uberis at 7, 14, 21, and 28 d posttreatment. Percentage of Strep. uberis IMI eliminated was 43, 88, and 100% for the 2-, 5-, and 8-d ceftiofur treatment regimens, respectively. Both the 5- and 8-d ceftiofur extended therapy treatment regimens had significantly higher bacterial cure rates than the standard 2-d ceftiofur treatment regimen. The bacterial cure rate of the 8-d ceftiofur extended therapy group was marginally better (P = 0.052) than the 5-d ceftiofur extended therapy group. Results of this study indicate that ceftiofur therapy was effective for eliminating Strep. uberis experimental IMI, and 5- and 8-d extended ceftiofur therapy regimens were more effective than the standard 2-d treatment.