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91.
Bruce Diamond 《电子产品世界》2006,(16):23-24
近几年,无论是手机代表的无线移动网络及其基础设施,还是以蓝牙(Bluetooth)、无线局域网(WLAN)、Zigbee等长、短距离的无线通信技术,或者是WiMax、RFID等面向特定应用的专门技术,给人们带来了种种方便,也在悄悄改变着产业的格局.作为各种无线技术基础的RF技术,也在不断吸纳新技术、新设计,以满足系统对于更大数据传输量、更低的功耗和成本要求、更苛刻的信号可靠性要求等挑战.从另一侧面看,由于RF技术固有的较高门坎,并非一些新手力所能及,虽然半导体产业链以厂商数量众多著称,但RF技术供应商则相对较少. 相似文献
92.
Gel permeation chromatography with application of the universal calibration concept was found to be a rapid and effective method for quantification of extrusion-induced starch fragmentation. This method (Timpa. J.D., J. Agr. Food Chem. 39 (1991), 270–275) employs dimethyl acetamide (DMAC) with lithium chloride to solubilize samples and automated gel permeation chromatography for fractionation. Instrumentation was equipped with a viscometer and refractometer, data was interpreted by application of the universal calibration concept. These results confirm that the largest starch molecules in corn meal (107 to 108 Daltons) were slightly prone to fragmentation. Fragments produced were primarily in the weight range of 104–107 Daltons. In addition, some smaller fragments (ranging between 5,000 and 7.500) were also generated by extrusion. 相似文献
93.
Chain interactions of sodium alginate during its gelation were investigated by a new gelation method which was based on a Ca2+-concentrating gelling process (CCGP) produced by water evaporation of an alginate solution containing CaCl2. For two commercially available sodium alginate samples (low viscosity (LA) and medium viscosity (MA)) having different molecular weight distributions but the same G/M blocks, the critical Ca2+ concentrations for their gelation were found to be 4.6 (for LA) and 4.5 (for MA) μmol/mL after evaporating water from 1% of alginate solutions containing 4 μmol/mL of CaCl2. The CCGP gelation method for alginate under the above conditions were confirmed by rheological measurements and the observed highly ordered and uniform mesh structure of the CCGP-formed alginate gels shown in cryo-SEM images. Combinations of LA and MA at different ratios (0:4, 1:3, 2:2, 3:1, 4:0 on weight basis) were studied using the CCGP gelation method to further the understanding of the alginate chain interactions during gelation. Different LA/MA mixtures exhibited different rheological properties in either non-gelled or gelled systems, indicating that the molecular weight distributions of the sodium alginates influence the alginate chain interactions mediated by Ca2+. Thus, an appropriate combination of LA and MA is required for a strong alginate interchain interaction during CCGP, and alginate products with desirable characteristics can be produced by manipulating the mixing ratios of sodium alginates having different molecular weight distributions even at the same total composition and distribution of G/M blocks. 相似文献
94.
Michael S. Koch John M. DeSesso Amy Lavin Williams Suzanne Michalek Bruce Hammond 《Critical reviews in food science and nutrition》2016,56(3):512-526
To determine the reliability of food safety studies carried out in rodents with genetically modified (GM) crops, a Food Safety Study Reliability Tool (FSSRTool) was adapted from the European Centre for the Validation of Alternative Methods’ (ECVAM) ToxRTool. Reliability was defined as the inherent quality of the study with regard to use of standardized testing methodology, full documentation of experimental procedures and results, and the plausibility of the findings. Codex guidelines for GM crop safety evaluations indicate toxicology studies are not needed when comparability of the GM crop to its conventional counterpart has been demonstrated. This guidance notwithstanding, animal feeding studies have routinely been conducted with GM crops, but their conclusions on safety are not always consistent. To accurately evaluate potential risks from GM crops, risk assessors need clearly interpretable results from reliable studies. The development of the FSSRTool, which provides the user with a means of assessing the reliability of a toxicology study to inform risk assessment, is discussed. Its application to the body of literature on GM crop food safety studies demonstrates that reliable studies report no toxicologically relevant differences between rodents fed GM crops or their non-GM comparators. 相似文献
95.
Microbial fuel cells--challenges and applications 总被引:4,自引:0,他引:4
96.
The rates of CO and CO/CO2 hydrogenation at 4.2 MPa and 523 K are reported for a series of Cu/SiO2 catalysts containing 2 to 88 wt.% Cu. These catalysts were prepared on a variety of silica sources using several different Cu deposition techniques. In CO/CO2 hydrogenation, the rate of methanol formation is proportional to the exposed Cu surface area of the reduced catalyst precursor, as determined by N2O frontal chromatography. The observed rate, 4.2×10–3 mole CH3OH/Cu site-sec, is within a factor of three of the rates reported by others over Cu/ZnO and Cu/ZnO/Al2O3 catalysts under comparable conditions. These results suggest that the ZnO component is only a moderate promoter in methanol synthesis. Hydrogenation of CO over these catalysts also gives methanol with high selectivity, but the synthesis rate is not proportional to the Cu surface area. This implies that another type of site, either alone or in cooperation with Cu, is involved in the synthesis of methanol from CO. 相似文献
97.
The efficacy of individual ω-t-3 polyunsaturated fatty acids (PUFA) in altering eicosanoid synthesis in peritoneal macrophages
was studied by feeding mice for 10 days a diet containing 2 wt% fat, which included 0.5 wt% ethyl esters of eicosapentaenoic
acid (EPA), docosahexaenoic acid (DHA) or linolenic acid (LNA). Upon stimulation with calcium ionophore A23187, macrophages
from these animals produced significantly lower amounts of leukotriene C4, leukotriene B4 and 12-hydroxyeicosatetraenoic acid, prostaglandin E2 and 6-keto prostaglandin F1α compared with those obtained from animals on the diets containing olive oil or safflower oil. The decrease in leukotriene
synthesis was similar in the animals fed DHA, EPA or LNA diets. This depression of eicosanoids by DHA and EPA was associated
with decreased levels of arachidonic acid (AA); however, LA that altered eicosanoids did not have the same effect on AA levels. 相似文献
98.
Catherine Simoneau J. Bruce German 《Journal of the American Oil Chemists' Society》1996,73(8):955-961
Milkfat was separated into major chainlength fractions by solid-phase extraction. The effect on thermal behavior and texture
of replacing both saturated and monounsaturated long-chain triglycerides from milkfat by long-chain monounsaturated triglycerides
with an unsaturated fatty acid in thesn-2 position is reported. Increasing proportions of cocoa butter were added to fractions of short-to medium-chain triglycerides
(C22−C44) and medium- to long-chain triglycerides (C36−C48) isolated from milkfat. Thermal behavior and texture of the mixtures were measured. Results indicated that long-chain monounsaturated
triglycerides from cocoa butter enhanced co-crystallization and co-operative melting and did not induce polymorphic transitions
upon crystallization and melting of the fractions. At 4°C, they acted as texture builder if present in proportions of more
than 30%, whereas below this level, they acted as texture softeners. The effect of the long-chain monounsaturated triglycerides
on the texture of fractions that melt at low temperature could not be predicted from the proportion of solid fat at that temperature.
Presented at the 1995 AOCS Annual Meeting & Expo, San Antonio, Texas, May 1995. 相似文献
99.
100.
Raman spectroscopic and conductivity studies show that pyridinium derivatives of the TlCl52⊖, TlCl63⊖ and Tl2Cl93⊖ species dissociate in ethanol solution to yield the TlCl4⊖ ion, but the [(C2H5)4N]2TlCl5 salt does not dissociate further and behaves like a 2:1 electrolyte. 相似文献