DBS电视接收机低中频与直接转换调谐器的比较

CMOS技术是把L波段卫星调谐器、解调器和其它功能整合至低成本、高效能单芯片的关键。本文将探讨新型低中频和传统零中频DBS调谐器架构在单芯片DBS射频前端设计中的优缺点。     

The effect of an antiphlogistic incorporated in liposomes on experimentally induced inflammation

The antiphlogistic Ibuprofen incorporated in liposomes caused a decrease of the inflammatory edema induced by Carrageenan in the distal part of the rat's hind leg after both the intramuscular and percutaneous administration. The antiphlogistic effect of free Ibuprofen in the cream was weaker. Intramuscular administration of empty liposomes slowed down in the initial stages the development of inflammation and slightly diminished the size of edema.     

An automated enzymic micromethod for the measurement of fat in human milk

Most (98%) of the fat in human milk is present as triglycerides. This paper describes the use of a clarification procedure that enables the level of human milk fat to be determined by measurement of glycerol released by enzymic hydrolysis of triglycerides. The method requires only 10-50 microliters milk, thus presenting a possible technique for work with small mammals, and is suitable for use with autoanalysers, permitting rapid sample throughput.     

Numerical investigation of the error on flow measurements due to exhaust gas heating and cooling in the SBI‐configuration

The possible flow measurement error due to heating or cooling of exhaust gases in the Single‐Burning‐Item (SBI) test is estimated from numerical experiments. It is illustrated that there is no one‐to‐one correspondence between the velocity profile shape and the instantaneous Reynolds number, due to the time‐dependent temperature and density profile evolution in the exhaust gas pipe. A non‐ambiguous relation is found between the velocity profile shape and an ‘effective’ Reynolds number, based on the turbulent viscosity. Maximum variations of the velocity correction factors, relating the mean velocity to the velocity on the pipe axis, are found to be in the order of 2% for limiting circumstances for the SBI test. The primary effect is caused by instantaneous Reynolds number variations. The effect of heating or cooling of the flow by the hot or cold pipe is noticeable, too. The statements are proved to be valid independent of the computational grid, the turbulence model and the time steps taken to obtain the numerical solutions. Copyright © 2006 John Wiley & Sons, Ltd.     

Geographic distribution and clinical description of leishmaniasis cases in Peru

Asymmetric acetylcholinesterase (AChE) is anchored to the basal lamina (BL) of cholinergic synapses via its collagenic tail, yet the complement of matrix receptors involved in its attachment remains unknown. The development of a novel overlay technique has allowed us to identify two Torpedo BL components that bind asymmetric AChE: a polypeptide of approximately 140 kDa and a doublet of 195-215 kDa. These were found to stain metachromatically with Coomassie blue R-250, were solubilized by acetic acid, and were sensitive to collagenase treatment. Upon sequence analysis, the 140 kDa polypeptide yielded a characteristic collagenous motif. Another AChE-binding BL constituent, identified by overlay, corresponded to a heparan sulfate proteoglycan. Lastly, we established that this proteoglycan, but not the collagenous proteins, interacted with at least one heparin binding domain of the collagenic tail of AChE. Our results indicate that at least two BL receptors are likely to exist for asymmetric AChE in Torpedo electric organ.     

Flow patterns and mass transfer rates in fluidized bed ion exchange equipment

The axial mixing of ion exchange resin and liquid in fluidized beds is modelled by a series of well-mixed cells for the resin and an equal or larger number of mixed cells for the liquid. Concentration breakthrough curves are calculated using this mixing model, assuming finite mass transfer kinetics and irreversible equilibrium. The model is used to describe mixing patterns and kinetics in static fluidized beds (no resin flow); the information so obtained can be used to design continuous and periodic flow counter-current fluidized bed ion exchange systems.     

Use of renewables for the production of chemicals: Glycerol oxidation over carbon supported gold catalysts

As a renewable feedstock and due to its high functionality glycerol is an attractive reactant for the production of a large number of valuable compounds. We report on an environmentally friendly alternative to produce chemicals from the glycerol oxidation, which are currently produced either by stoichiometric oxidation processes or by enzymatic routes. We investigate the heterogeneously catalyzed liquid-phase oxidation of glycerol with carbon supported gold catalysts. The prepared nanosized gold catalysts are highly active, so that the reaction could be performed under atmospheric pressure. The influence of the preparation method of the catalysts has been investigated. Moreover, the support effect on the catalytic process has been studied and discussed in terms of pore structure of the investigated carbon materials. The promotor effect of platinum on Au/C catalysts was examined and it could be shown that the presence of Pt increases not only the catalyst activity but also the selectivity. By promoting the gold catalysts with platinum the selectivity to dihydroxyacetone could be increased from 26% (Au/C) to 36% (Au–Pt/C).