The neuropeptide red pigment concentrating hormone affects rhythmic pattern generation at multiple sites

The level of LamB protein in the outer membrane of Escherichia coli was derepressed in the absence of a known inducer (maltodextrins) under carbohydrate-limiting conditions in chemostats. LamB protein contributed to the ability of the bacteria to remove sugar from glucose-limited chemostats, and well-characterized lamB mutants with reduced stability constants for glucose were less growth competitive under glucose limitation than those with wild-type affinity. In turn, wild-type bacteria were less growth competitive than lamB mutants with enhanced sugar affinity. In contrast to an earlier report, we found that LamB- bacteria were less able to compete in carbohydrate-limited chemostats (with glucose, lactose, arabinose, or glycerol as the carbon and energy sources) when mixed with LamB+ bacteria. The transport Km for [14C]glucose was affected by the presence or affinity of LamB, but only in chemostat-grown bacteria, with their elevated LamB levels. The pattern of expression of LamB and the advantage it confers for growth on low concentrations of carbohydrates are consistent with a wider role in sugar permeation than simply maltosaccharide transport, and hence the well-known maltoporin activity of LamB is but one facet of its role as the general glycoporin of E. coli. A corollary of these findings is that OmpF/OmpC porins, present at high levels in carbon-limited bacteria, do not provide sufficient permeability to sugars or even glycerol to support high growth rates at low concentrations. Hence, the sugar-binding site of LamB protein is an important contributor to the permeability of the outer membrane to carbohydrates in habitats with low extracellular nutrient concentrations.     

论网络升级方式与光纤选择的关系

在重点说明影响传输光纤设计的主要问题的同时，简要介绍了各种升级方式所面临的主要技术挑战，并详细说明这些挑战对传输光纤提出的技术要求。     

Benzodiazepine-induced outcome revaluation and the motivational control of instrumental action in rats

It has been argued that the control of instrumental action by motivational states is indirect, being mediated by the effects these states have on the incentive value of the instrumental outcome (A. Dickinson & B. W. Balleine, 1994). In this study, the benzodiazepine agonist midazolam was found to control instrumental action in a similar manner. Midazolam (1 mg/kg) increased rewarded instrumental performance in rats trained undeprived but only elevated performance in extinction when rats were reexposed to the instrumental outcome under midazolam before the test. This effect of reexposure under midazolam did not transfer to a test conducted under food deprivation, suggesting that it was not produced by drug-induced hunger. Finally, in animals trained hungry, midazolam was found to block outcome devaluation induced by a reduction in food deprivation, indicating that midazolam and food deprivation affect outcome value via a common substrate.     

Enterocolitis associated with Clostridium perfringens infection in neonatal foals: 54 cases (1988-1997)

OBJECTIVE: To identify clinical signs, physical examination findings, results of diagnostic tests, treatments administered, and clinical outcome of neonatal foals with enterocolitis associated with Clostridium perfringens infection. DESIGN: Retrospective study. ANIMALS: 54 neonatal foals. RESULTS: Most foals had acute onset of obtunded mentation, colic, or diarrhea and developed leukopenia, neutropenia, an abnormally high number of band neutrophils, toxic WBC, and hypoproteinemia within 24 hours after admission, despite high serum IgG concentrations (> 800 mg/dl). Abdominocentesis and abdominal radiography of some foals revealed exudative peritonitis and gaseous distention of the small and large intestine, respectively. Cytologic examination of feces revealed spores or gram-positive rods in 8 of 10 foals. The most common genotypes of C perfringens isolates were type A and C, alone or in combination. Treatment did not alter mortality rate for most foals that had a positive culture for C perfringens type C. Of 54 foals, 29 (54%) that had C perfringens-associated enterocolitis died. Foals that had a culture that yielded C perfringens had higher sepsis scores, IgG concentrations, and mortality rates, compared with the overall hospital population of neonatal foals. CLINICAL IMPLICATIONS: Foals less than 7 days old that have enterocolitis associated with C perfringens infections, especially type C, have a guarded prognosis. Cytologic examination of feces to determine spore counts and detect rods may be a means for early identification of C perfringens infections. Polymerase chain reaction assays to determine genotype are important for designing preventive treatment regimens.     

The interactive editing and contouring of empirical fields

A system for the interactive editing and contouring of surfaces derived from empirical fields is described. The approach taken begins with the representation of a field as a general-order, nonuniform, tensor-product, B-spline surface. It provides an interactive display for editing the surface by control-vertex manipulation and a contouring algorithm that is specifically designed for the fast and robust contouring of B-spline surfaces. Interactive editing of the resulting model is feasible because of the local nature of editing changes when B-splines are used. The use of nonuniform B-splines gives the flexibility required to model highly irregular data efficiently     

Questionnaire development: an examination of the Nordic Musculoskeletal questionnaire

This paper describes the outcome of user trials of the Nordic Musculoskeletal Questionnaire which encompassed the views of the following groups: data entry clerks, technical staff, administrative clerks and 481 subjects employed in 10 supermarkets. A significant number of improvements was identified, especially concerning its wording, layout and administration. This has led to a standardized version being produced for use in studying the prevalence of reported symptoms in many types of occupational groups.     

The use of γ -alumina-polymerized furfuryl alcohol resin binders in the fabrication of graphite

Two kinds of γ-alumina-polymerized furfuryl alcohol resins were synthesized and examined as graphite binder materials. Prior to their use, the resins were characterized according to viscosity and molecular size distribution. Investigation by gas chromatography showed that, relative to acid-polymerized resins, the γ-alumina-polymerized furfuryl alcohol resins contain large amounts of products that will not polymerize further. Extruded graphite rods were manufactured from both the γ-alumina-polymerized resins and from comparable acid-polymerized resins. The graphites fabricated with the γ-alumina-polymerized resins are shown to have generally poorer physical properties than those made with acid-polymerized resins of similar viscosities. Evidence is presented to show that not only must molecular size distribution be considered when evaluating the suitability of furfuryl alcohol resins as graphite binder materials, but also of importance is the capability of the low-molecular-weight resin components to further polymerize during heat-treatment.     

Performance of Methanol Oxidation Catalysts with Varying Pt:Ru Ratio as a Function of Temperature

This paper describes the effects of varying the Pt to Ru ratio in carbon-supported catalysts for methanol oxidation as a function of temperature. Previously these effects were studied in isolation, but now it is shown that the composition of a given catalyst as a function of temperature is extremely important for its activity towards methanol oxidation. Platinum rich 3:2 atomic ratio catalysts perform better than a 1:1 catalyst at 25 °C, where only Pt is believed to be active towards methanol dehydrogenation, since this process is a highly thermally activated process on Ru sites. This result is reversed at 65 °C, where the 1:1 catalyst displays much higher currents across the entire range of polarization. This may result from methanol dehydrogenation occurring on both Ru and Pt sites at higher temperatures. At an intermediate temperature, 45 °C, the 3:2 catalyst is seen to perform better at lower current values, while the 1:1 catalyst is superior at higher current densities, with the crossover occurring at 62 A g^–1. As a consequence, when designing fuel cell catalysts, the composition of the catalyst employed should be tailored with respect to the exact operating conditions, in order to promote optimum fuel cell performance.