双路输出降压型控制器可产生准确、高效和可靠的高电流轨-设计要点478

引言 LTC(R)3855能够以上佳的准确度和效率来产生高电流轨,旨在满足当今最先时的网络、电信和服务器应用极其苛刻的要求.     

The location of inhibitory specificities in human mucus proteinase inhibitor (MPI): separate expression of the COOH-terminal domain yields an active inhibitor of three different proteinases

Human mucus proteinase inhibitor (MPI) consists of 107 aminoacids arranged in two domains showing high homology to eachother. This protein is an inhibitor of different serine proteinasesincluding trypsin, chymotrypsin, leukocyte elastase and cathepsinG. On the basis of sequence comparisons it has been suggestedthat the first domain inhibits trypsin, whereas the second onewas thought to be active against chymotrypsin and elastase.To prove the location of the different inhibitory activitiesgene fragments for both domains have been cloned separatelyand expressed in Escherichia coli. Inhibition assays with theisolated recombinant domains showed that the second domain isactive against chymotrypsin, neutrophil elastase and trypsin,whereas for the first domain only a weak activity against trypsincould be detected. These results suggest that the inhibitoryactivities of the native molecule towards these three proteinasesare all located in the second domain.     

Report of an IEEE Task Force?An IEEE Opinion on Research Needs for Biomedical Engineerng Systems

MORE than 200 years ago, our forefathers made note of man's inalienable rights to life, liberty, and the pursuit of happiness. To the engineering community (applied science in the service of man), these may be coincident with applications to medicine and biology (biomedical engineering), defense, and entertainment. Biomedical engineering research has the distinction, among these three missions, of not only contributing to the quality of human life through the industrial economy but also to life itself?the most fundamental concern of all people. It is through biomedical engineering research that we have been able to learn much concerning the functioning of living systems, and it is through such knowledge that we have been able to develop improved clinical diagnosis, monitoring, and treatment, including life-sustaining devices and aids to the handicapped. Each step represents an improvement in the quality of life, and each step forms the foundation upon which to gain new knowledge to improve upon earlier developments.     

Hydrolytic degradation of oligo(lactic acid): a kinetic and mechanistic study

This study shows that the degradation mechanism and kinetics of monodisperse oligo(lactic acid)s esterified with N-(2-hydroxypropyl)methacrylamide (HPMAm) are strongly influenced by the nature of the chain end. Oligomers with free hydroxyl chain ends degraded predominantly by chain end scission via a backbiting mechanism with a pseudo first-order rate constant k_bb=2.7 h⁻¹ in aqueous buffer (37 °C, pH 7.2). Once the hydroxyl groups were protected by acetylation, random chain scission became the rate limiting step with k_r=0.022 h⁻¹ under the same conditions. Using these rate constants, the theoretical time-resolved degradation profile was calculated for every (intermediate) degradation product and corresponded very well with the experimental results. The rate of formation of HPMAm was independent of the chain length for the acetylated oligomers, while the hydroxyl terminated oligomers with an even number of lactic acid units formed HPMAm more rapidly than oligomers with an odd number of units. The possibility to fine-tune the degradation rate is relevant when applied as e.g. hydrogels for controlled release or tissue engineering materials.     

Influence of agronomic management of legume crops on soil accumulation with nitrate

Nitrate is known to accumulate under legume crops. The effects of legume crop, inoculation, row width, sowing rate, sowing date, and intra-cropping with wheat, on the amount and soil distribution of mineral N, residual soil water, crop biomass and crop N were studied at Wagga Wagga in south-east Australia. After removal of most of the above-ground plant material, the treatment effects on the biomass, N content, grain yield and grain N of wheat, established in the following season, were also measured. In a later experiment at Wagga, the recovery of 15N applied to the mid-row of lupin crops established at three row widths was estimated at crop maturity. At Condobolin, row width effects on the soil distribution of mineral N, biomass, N accumulation and N fixation of crop legumes and cereals, were determined. At physiological maturity, at Wagga Wagga, very little nitrate was left beneath cereals. Significantly more was left under legume crops, mostly below 30 cm of soil depth, and it was distributed differently depending on crop, inoculation, and sampling location. More nitrate was left under pea and faba than under lupin, and in response to inoculation. Mixing wheat with narrow-leaf lupin did not prevent nitrate accumulation in soil. For most of the legumes more nitrate was left in the mid-row than in the in-row; and more nitrate was left at the mid-row of lupin crops sown with wider rows. The additional nitrate left with wider rows increased the growth, N content, grain yield and protein of wheat established in the following season. 15N labelled nitrate applied mid-row was used less effectively by lupin as row width increased, in a dry season. At Condobolin, lupin established with wide rows used less soil nitrate than with narrower rows but maintained crop N by increased N fixation. In contrast, field pea maintained N demand by increasing nitrate uptake at intermediate row spacing. The study shows that the amount of nitrate accumulated in soil during legume cropping is susceptible to agronomic management, particularly crop selection, row width and inoculation; and that variation in the amount of this nitrate may carry forward to impact wheat production in the follow-on season.     

Microrheology: new methods to approach the functional properties of food

Three configurations have been developed to improve the understanding of structural element interactions in food material during deformation. The three configurations combine an inverted confocal scanning laser microscope (CSLM) and a cell that can apply to the sample a specific deformation: continuous shear, linear oscillatory shear and biaxial extension (compression).In the continuous shear and oscillatory shear configurations (OSCs), a zero-velocity plane is created in the sample by moving two plates in opposite direction, maintaining stable observation conditions of the structural behaviour under deformation. The OSC allows simultaneous application of CSLM and diffusing wave spectroscopy, a multiple light scattering technique. The third configuration (compression configuration) allows observation at a stagnation point during rheometric measurements. The configurations accept semi-liquid products (dressing, sauces, dairy products, etc.) for investigations in area such as aggregation, gelation, interactions at interface, coalescence, break-up.     

A micromechanically motivated finite element approach to the fracture toughness of silicon nitride

Silicon nitride is often used, when high fracture toughness and strength is needed. For a safe and economic structural design with this material, a prediction of its resistance against thermal and mechanical loads is important. The finite element method together with a continuum damage mechanics model allows for such calculations. The parameters of the suggested model have been adjusted to three-dimensional micromechanical finite element simulations, which include models for the microstructure, the thermoelasticity and the fracture. The material model is used for four-point bend test simulations. The results are compared to recent experiments.     

Effect of calcium and/or barium crosslinking on the physical and antimicrobial properties of natamycin-loaded alginate films

The preparation of alginate films with suitable properties requires a two-step contact with reticulating agents: initially a weakly structured pre-film is formatted which is further crosslinked in a second stage by immersion in a more concentrated solution. The present work evaluated the effects of a combined crosslinking procedure using calcium and barium ions on the physical and morphological properties of alginate-based films containing natamycin as antimicrobial agent. The release behavior of natamycin in water was evaluated as well as the antimicrobial activity against four target microorganisms, which are common cheese product contaminants. Films attributes were affected by the type of ion used in the second stage while the natamycin release rate and the antimicrobial activity were influenced by the ion used in the first stage. Films crosslinked with Ba²⁺ in the first and Ca²⁺ in the second stage (Ba–Ca films) exhibited physical properties very similar to films crosslinked with calcium in both stages. Release kinetics of natamycin in water fitted well to Fick's second law diffusional model, with effective diffusivity values ranging from 0.40 × 10⁻¹¹ to 1.74 × 10⁻¹¹ cm²/s. Ba–Ca films presented the lowest natamycin diffusion coefficient and the smallest inhibition zone diameter against the four microorganisms tested.     

The inherently integrative approach of positive psychotherapy.

Positive Psychotherapy (PPT) is a therapeutic metatheory and approach that was developed in 1968 by Dr. Nossrat Peseschkian. His contribution to psychotherapy is not to be confused with what is being called PPT and is an outgrowth of Positive Psychology begun by Dr. Martin Seligman in the U.S. Peseschkian's approach to therapy is inherently and systematically integrative, along the lines of being cross-cultural, multidisciplinary, therapeutically, and psychologically intertheoretic. This article presents some basic premises of PPT: the use of stories; having a positive starting point; basic and actual capacities; five-stage therapeutic model; as well as mentioning other aspects of PPT and a case study. PPT is well suited to therapists advocating integrative psychotherapy as demonstrated by empirical research. (PsycINFO Database Record (c) 2010 APA, all rights reserved)