硬件锁中的无线USB

无线USB的前途似乎无与伦比——它能消除那些把大家桌面弄得像鼠窝一样小小的不怎么灵便的电缆。但事实上,只有需要大量的外设时无线USB设备才有优势,而且它必须非常微型而廉价,否则带来的麻烦远多于缠绕的电缆。因此,插在PC USB端口作为无线基站的硬件锁就必须有尽可能高的集成度。但一片芯片中要包含USB有线接口、控制器、无线基带和RF电路,技术上还无法实现。下面我们将看到一家供应商Wisalr的一种可量产参考设计,它是如何接近于解决这个问题的。     

Thermal Diffusivity/Conductivity of Alumina—Silicon Carbide Composites

Thermal diffusivity and conductivity values for several Al₂O₃-SiC whisker composites were determined. The thermal diffusivity values spanned the range from 373 to 1473 K, and thermal conductivity data wre obtained between 305 and 365 K. The thermal diffusivity decreased with increasing temperature and increased with SiC-whisker content. An estimate of the thermal conductivity of the whiskers was obtained from the direct thermal conductivity measurements, but attempts to derive whisker conductivity values from the thermal diffusivity data were not successful because the laser flash method lacks the required accuracy and precision. Specimens were subjected to two different thermal quench experiments to investigate the effect of thermal history on diffusivity. In the most severe case, multiple 1073- to 373-K quenches, radial cracks were observed in the test specimens; however, there was no change in diffusivity. The lack of sensitivity to thermal cycling appears to be related to the sample size.     

Phospholipids ofRhizobium meliloti andAgrobacterium tumefaciens: Lack of effect of Ti plasmid

We have studied the phospholipid composition ofRhizobium meliloti strains which do or do not contain the large, tumor-inducing (Ti) plasmid ofAgrobacterium tumefaciens. The major phospholipids of stationary phase cells were phosphatidylethanolamine (PE) (22%), phosphatidyl-N-methylethanolamine (22%), phosphatidylcholine (PC) (27%), phosphatidylglycerol (11.4%), and cardiolipin (11%); as average percent of lipid phosphorus. Phosphatidyl-N,N-dimethylethanolamine (3.7%) was also present. The proportions of PE were higher, and PC lower, in logarithmic phase cells. No significant differences were seen in the proportions of phospholipids in strains with or without the Ti plasmid. Qualitative examination of the phospholipids ofA. tumefaciens with or without the Ti plasmid similarly revealed no differences.     

Transureteroureterostomy for urinary diversion in children

We report here a model of submaximal spinal cord injury, employing direct thoracic cord compression in ferrets. This yields consistent and reproducible long term consequences on local cellular structure and on locomotive function. We show also that both the anatomical and functional losses can be measured objectively using simple techniques, and that useful long-tract mediated locomotion is preserved after severe axonal losses at the site of injury.     

Taste aversions to food flavors and vaginal secretion in golden hamsters.

Although rodents readily associate virtually any distinctive flavor with gastrointestinal illness when the flavor and illness have been paired, experience with a flavor can provide information that interferes with later attempts to produce aversions to the familiar taste. The vaginal secretion of female hamsters carries sexual information for males, which does not depend on previous experience; it was studied, in the present 3 experiments, whether that built-in information might interfere with associations between flavor of the excretion and illness. Surprisingly, the Ss, 32 male Syrian hamsters, showed dramatic changes in behavior toward the vaginal secretion when its presentation was followed by lithium chloride poisoning. Results suggest that mammalian responses to sex pheromones are far more easily modified by experience than has been supposed. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Biochemical changes during ripening of some sudanese date varieties

Changes in the chemical composition of three popular Sudanese varieties of date (Jawa, Bentamoda and Mishrig Wad Laggai) during ripening are described and are related to changes in texture and in the activities of various degradative enzymes in the fruit. Total invertase levels were high throughout maturation of the three varieties. Although the proportion of soluble enzyme increased during ripening solubilisation did not appear to influence the relative amounts of sucrose and reducing sugars in the ripening fruit. Both cellulase and polygalacturonase were absent or at low levels in the green fruit but displayed large increases in activity during ripening. This enhancement was reflected in a reduction in fruit firmness although little change in cellulose or pectin levels was apparent analytically until the final stage of ripening. Despite a considerable rise in pectinesterase activity during ripening no significant trend could be discerned in the degree of esterification of pectin suggesting that the enzyme is of minor importance in softening of these fruit.     

A small,simple sorghum decorticating device

A small commercially available laboratory mill was found to be suitable to dehull small batches of sorghum grain. The device used one grinding plate and an agitating dimpled plate and took about 1 min to adequately dehull the grain. At the completion of dehulling period decorticated grain was collected directly in a sample holder. Data from various cultivars, grain sizes and types of grain were reproducible. It only required 10 s to clear the device between samples.     

Preparation and characterisation of 2-formyl-1,4,5,6-tetrahydropyridine,a compound with a cracker-like odour

2-Acetyltetrahydropyridine is an important flavour constituent that imparts roasty, popcorn-like, and cracker-like odours to foods, such as bread, rice, popcorn, taco shells and tortilla chips. We postulated that the homologue with a formyl group in the C-2 position, 2-formyltetrahydropyridine, might have similar desirable odour qualities. Synthesis of this compound was performed by oxidation of 2-piperidinemethanol with silver carbonate supported on Celite®. This reaction produced a major volatile (46.9% of the total volatiles) with a retention index of 1023 on DB-1. GC–O revealed that the unknown had a strong cracker-like odour. The electron impact mass spectrum of the unknown had the following major ions: m/z 82, 111, 54, 68, 28, 43. The m/z 53–54 ratio and m/z 82–83 ratio were consistent with a 1,4,5,6-tetrahydropyridine ring structure. GC-FTIR of the unknown revealed an N–H stretching band at 3435 cm⁻¹ and a Fermi doublet at 2827 and 2713 cm⁻¹ that indicated the presence of an aldehyde. A strong carbonyl absorption band was present at 1703 cm⁻¹. The unknown was tentatively identified as 2-formyl-1,4,5,6-tetrahydropyridine, based on its retention index, odour quality, mass spectrum, and vapour phase infrared spectrum.