Shigella isolates in stool

A total of 447 Shigella strains were isolated from stool samples during 1989-1991. Of these 270 (60%) were from children. Among the different species and serotypes Sh. flexneri 60 (13.4%) and Sh. sonnei Phage 139 (65%) were the most frequently isolated strains. 154 (34.4%) strains were resistant to three and 179 (40%) to more than three antibiotics. Some strains of Shigella were found to be resistant to furazolidine and neomycin.     

Fire resistant fluids for industrial transformers

A search is under way for the ultimate replacement of polychlorinated biphenyls used as insulation in industrial transformers. Some possibilities have surfaced, but others are yet to be explored. Note: Mr. Pearce presented this paper at the 81st Annual Meeting of the National Fire Protection Association on May 18, 1977.     

空间圆弧逼近法加工螺旋曲面的参数优化

螺旋机械的核心部件——螺杆转子的螺旋曲面成形复杂、加工难度大，国内外较多采用成形车削方法加工，此法在加工精度、加工效率及螺杆表面质量上存在不足，为了获得更好的螺旋表面加工质量，提出了外切圆弧母线逼近加工方法.依据圆弧逼近原理，建立了螺杆转子空间螺旋曲面的铣削模型，确定了刀具空间逼近圆弧的基本结构参数，求解了逼近圆弧的加工误差，实现了刀具逼近圆弧参数的优化设计，并给出了相应的计算实例.计算结果表明，提出的刀具参数优化方法具有可行性.     

The chemical constitution of the proteoglycan of human intervertebral disc

Proteoglycan was prepared from three pools of normal human intervertebral discs by extraction with buffered 4M-guanidinium chloride followed by CsCl-density-gradient ultracentrifugation. Chromatography on agarose (Bio-Gel A-150m) and on DEAE-cellulose suggested a single polydisperse proteoglycan species. The intrinsic viscosities of three preparations were 166, 122 and 168 ml/g. After degradation with 0.5M-KOH containing 0.02M-NaBH4, the glycosaminoglycans were recovered quantitatively and their Ca2+ salts separated into a hexuronate-rich fraction (fraction 1), which was precipitated in 0-45% (v/v) ethanol, and a hexose-rich fraction (fraction2), which was precipitated in 45-70% (v/v) ethanol. Qualitative and quantitative analyses of the glycosaminoglycans revealed fraction 1 to be chondroitin sulphate, and fraction 2 to be keratan sulphate; the latter was contaminated with protein and possibly a small amount of another glycosaminoglycan. For both glycosaminoglycans, plots of log(mol.wt.) against weight fell close to a normal distribution. The mode for chondroitin sulphate was close to 20000; that for keratan sulphate, 10000. A threefold range of molecular weight included the central 16-84% [+/- 1 S.D. of log(mol.wt.)] of the weight of both fractions.     

Analog VLSI Circuit Implementation of an Adaptive Neuromorphic Olfaction Chip

In this paper, we present the analog circuit design and implementation of the components of an adaptive neuromorphic olfaction chip. A chemical sensor array employing carbon black composite sensing materials with integrated signal processing circuitry forms the front end of the chip. The sensor signal processing circuitry includes a dc offset cancellation circuit to ameliorate loss of measurement range associated with chemical sensors. Drawing inspiration from biological olfactory systems, the analog circuits used to process signals from the on-chip odor sensors make use of temporal "spiking" signals to act as carriers of odor information. An on-chip spike time dependent learning circuit is integrated to dynamically adapt weights for odor detection and classification. All the component subsystems implemented on chip have been successfully tested in silicon     

Storage of hydrogen in floating catalytic carbon nanotubes after graphitizing

Hydrogen storage under moderate pressure (~10 MPa) and ambient temperature (~25℃) in multi-walled carbon nanotubes (MWNTs) prepared by the floating catalyst method is investigated. The capacity of hydrogen adsorption is evaluated based on both the nanotubes diameter and morphology. Indirect evidence indicates that hydrogen adsorption not only occurs on tube surface and interiors, but also in tube interlayers. The results show that the floating catalytic carbon nanotubes might be a candidate hydrogen storage material for fuel cell electric vehicles.