Mechanomyography and oxygen consumption during incremental cycle ergometry

Brucella abortus strain RB51 was recently approved as an official brucellosis calfhood vaccine for cattle by the Animal and Plant Health Inspection Service branch of the United States Department of Agriculture. Currently available serologic surveillance tests for B. abortus do not detect seroconversion following SRB51 vaccination. The purpose of this study was to evaluate a dot-blot assay using gamma-irradiated strain RB51 bacteria for its specificity and sensitivity to detect antibody responses of cattle vaccinated with strain RB51. Dot-blot titers of sera at a recommended dosage (10(10) colony-forming units) were similar to those of sera from cattle vaccinated with similar numbers of B. abortus strain 19 and greater (P < 0.05) than titers of nonvaccinated cattle. In the first 12 weeks after vaccination with 10(10) colony-forming units of strain RB51, the RB51 dot-blot assay had 100% specificity for titers of 80 or less and a 53% sensitivity for titers of 160 or greater. Sensitivity of the RB51 dot-blot assay peaked at 4 weeks after vaccination with 10(10) colony-forming units of strain RB51. Dot-blot responses of sera from cattle vaccinated with a reduced dosage of strain RB51 (10(9) colony-forming units) did not differ (P > 0.05) from titers of sera from nonvaccinated cattle. Following intraconjunctival challenge with B. abortus strain 2308, titers on the RB51 dot-blot assay did not differ (P > 0.05) between nonvaccinated cattle and cattle vaccinated at calfhood with strain 19 or strain RB51.     

Analysis of interfacial failure in a composite microbundle pull-out experiment

Modeling of the failure of polymer-matrix composites requires substantial information about the mechanisms of failure at the interface, and load redistribution around fiber breaks in the composite. Current interface experiments involving the use of ‘microcomposites’ of single embedded fibers in a matrix generally do not include all the key geometric features of the real composite; in particular, they do not include the effects of fiber volume fraction and the higher matrix shear resulting from closely neighboring fibers. A new experiment was recently devised to assess some of these effects: it is referred to as the single-fiber pull-out from microbundle (SFPOM) experiment. It consists of a hexagonal arrat of seven fibers in a matrix where the outer six fibers are restrained and the center fiber is pulled out. Recent experimental data from tests with this geometry are analyzed here using three mechanical models of the failure process, and parametric studies of the data are performed to assess the appropriateness of each model. Two of the models, based on fracture energy considerations as applied earlier to single embedded fibers in a matrix and adapted to our geometry, were found to model data from the SFPOM experiments poorly. The third model assumes the existence of three zones near a fiber break, including elastic, plastic and frictional debond zones, and was found to provide reasonable fit to the data under realistic assumptions.     

The additivity of substrate fragments in enzyme-ligand binding

BACKGROUND: Enzymes have evolved to recognise their target substrates with exquisite selectivity and specificity. Whether fragments of the substrate--perhaps never available to the evolving enzyme--are bound in the same manner as the parent substrate addresses the fundamental basis of specificity. An understanding of the relative contributions of individual portions of ligand molecules to the enzyme-binding interaction may offer considerable insight into the principles of substrate recognition. RESULTS: We report 12 crystal structures of Escherichia coli thymidylate synthase in complexes with available fragments of the substrate (dUMP), both with and without the presence of a cofactor analogue. The structures display considerable fidelity of binding mode and interactions. These complexes reveal several interesting features: the cofactor analogue enhances the localisation of substrate and substrate fragments near the reactive thiol; the ribose moiety reduces local disorder through additional specific enzyme-ligand interactions; the pyrimidine has multiple roles, ranging from stereospecificity to mechanistic competence; and the glycosidic linkage has an important role in the formation of a covalent attachment between substrate and enzyme. CONCLUSIONS: The requirements of ligand-protein binding can be understood in terms of the binding of separate fragments of the ligand. Fragments which are subsystems of the natural substrate for the enzyme confer specific contributions to the binding affinity, orientation or electrostatics of the enzymatic mechanism. This ligand-binding analysis provides a complementary method to the more prevalent approaches utilising site-directed mutagenesis. In addition, these observations suggest a modular approach for rational drug design utilising chemical fragments.     

Matching treatment focus to patient social investment and support: 18-month follow-up results.

Patients were randomly assigned to 1 of 3 treatments: brief broad-spectrum (BBS), extended relationship enhancement (ERE), or extended cognitive–behavioral (ECB). A hierarchical latent growth model was used to analyze the data of 188 patients (82%) followed for 18 months. ERE treatment was significantly more effective in increasing abstinence of patients entering treatment with a network unsupportive of abstinence or with a low level of investment in their network, whereas BBS treatment was more effective for patients with either (a) both a social network unsupportive of abstinence and a low level of network investment or (b) high investment in a network supportive of abstinence. ECB outcomes were neither as good as those matched nor as bad as those mismatched to the different exposures of relationship enhancement. This suggests that dose of relationship enhancement should be determined after assessing patient relationships. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Structure of a novel phytoecdysteroid,vitexirone, and efficient isolation of phytoecdysteroids fromVitex fisherii

A novel phytoecdysteroid, vitexirone, has been isolated from a MeOH extract of the root bark of the East African medicinal plantVitex fisherii by recycling high-performance liquid chromatography on a semipreparative scale. In addition, three known phytoecdysteroids, 20-hydroxyecdysone, ajugasterone C, and turkesterone, also were isolated. The structure of vitexirone has been established spectroscopically. The position and stereochemistry of the 11--hydroxy group of ajugasterone C and vitexirone were confirmed by the¹H-¹H homonuclear COSY NMR data. These phytoecdysteroids disrupt the molting process of the pink bollwormPectinophora gossypiella.     

Diffusion of lignin macromolecules within the fibre walls of kraft pulp. Part I: Determination of the diffusion coefficient under alkaline conditions

The intrinsic rate of diffusion of soluble lignin from fibre walls to bulk liquor has never been determined previously because of experimental difficulties; for example, the diffusion rate determined in a stirred cell is affected by the mechanical action of stirring. In our work, the intrinsic rate of diffusion of lignin macromolecules from the fibre walls of a softwood kraft pulp was determined under alkaline conditions using a displacement cell which eliminated external heat and mass transfer resistances and pulp fibre disturbances. The effects of such experimental conditions as pulp bed height and liquid flow rate were studied. The diffusion rate can be described by a diffusion model for a hollow cylinder with a very wide range of diffusion coefficients. The diffusion rate increased with increasing pH. Our results provide a new understanding of the lignin diffusion process in fibre walls, which is affected by the size of lignin molecules and the pores, and by the electrostatic interactions between intrafibre pore walls and lignin.     

白炭黑胎面胶的新一代硅烷偶联剂

填充白炭黑的低滚动阻力轮胎的开发不断获得新进展。与填充普通炭黑的轮胎相比，白炭黑轮胎不仅降低了油耗，而且具有优异的牵引性能和与后者相当的磨耗寿命。高分散性白炭黑和多硫化双-烷氧基硅烷的发展使高填充白炭黑轮胎商品化获得重大突破。炭黑胶料和白炭黑-硅烷胶料的能耗散机理差异很大，     

Optimal classification methods for diagnosing latent skills and misconceptions for option-scored multiple-choice item quizzes

Behaviormetrika - The paper’s extended Diagnostic Classification Modeling setting assumes (a) nominal item (question) coding, thus&nbsp;including multiple-choice (MC) items, and (b)...