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1. Nine male volunteers were exposed to the pyrethroid insecticide cyfluthrin. The study was performed in an exposure room, where an aerosol containing cyfluthrin was sprayed to obtain atmospheres with mean cyfluthrin concentrations of 160 and 40 micrograms/m3. Four volunteers were exposed for 10, 30 and 60 min at 160 micrograms/m3 and another five volunteers were exposed for 60 min at 40 micrograms/m3. For 160 micrograms/m3 exposure urine samples were collected before and immediately after exposure as well as for the periods 1-2, 2-3, 3-4, 4-5, 5-6, 6-12 and 12-24 h after exposure. For 40 micrograms/m3 exposure urine samples were collected before and 2 h after exposure. 2. The main urinary cyfluthrin metabolites, cis-/trans-3-(2,2-dichlorovinyl)-2,2-dimethylycyclopropane carboxylic acid (DCCA) and 4-fluoro-3-phenoxybenzoic acid (FPBA), were determined. The limit of detection (LOD) for all metabolites was 0.0025 microgram in an urine sample of 5 ml (0.5 microgram/l). After inhalative exposure of 40 micrograms cyfluthrin/m3 air for 60 min, the amount of metabolites in urine collected in the first 2 h after exposure was less than the LOD, namely 0.14 microgram for cis-DCCA, 0.15-0.28 microgram for trans-DCCA and 0.12-0.23 microgram for FPBA. 3. Of the metabolites, 93% was excreted within the first 24 h (peak excretion rates between 0.5 and 3 h) after inhalative exposure of 160 micrograms/m3. The mean half-lives were 6.9 h for cis-DCCA, 6.2 h for trans-DCCA and 5.3 h for FPBA. 4. The mean trans-:cis-DCCA ratio was 1.9 for the time course as well as for each subject. 5. The amount of metabolites in urine depends on the applied dose, on the exposure time and shows interindividual differences. 相似文献
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Direction-dependent scaling, shaping, and rotation of Gaussian basis functions are introduced for maximal trend sensing with minimal parameter representations for input output approximation. It is shown that shaping and rotation of the radial basis functions helps in reducing the total number of function units required to approximate any given input-output data, while improving accuracy. Several alternate formulations that enforce minimal parameterization of the most general radial basis functions are presented. A novel "directed graph" based algorithm is introduced to facilitate intelligent direction based learning and adaptation of the parameters appearing in the radial basis function network. Further, a parameter estimation algorithm is incorporated to establish starting estimates for the model parameters using multiple windows of the input-output data. The efficacy of direction-dependent shaping and rotation in function approximation is evaluated by modifying the minimal resource allocating network and considering different test examples. The examples are drawn from recent literature to benchmark the new algorithm versus existing methods 相似文献
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Low-power and high-speed discrete cosine transform (DCT) implementation of the images captured by the satellites presents a hardware design problem. The cost of the DCT implementation is dominated by the complexity of the multiplication of input data (image) with the DCT matrix. The techniques for minimising the complexity of multiplication by employing a differential pixel method are presented. In the proposed method 8times8 blocks of input image matrix are considered, the difference between the adjacent pixels is calculated and those differential pixels are used in DCT transformation. Synthesis results on 0.18 mum CMOS technology show that the proposed method gives an average of 13.2% reduction in power consumption and 10.9% improvement in speed over the conventional method. The proposed method can also be combined with the common subexpression elimination method for further reduction. 相似文献
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非线性地基上桩结构物空间分析 总被引:1,自引:0,他引:1
本文提出了桩结构物-非线性地基空间相互作用分析的迭代法和非线性有限元法。其中,桩基分析用p-y曲线法。结合实际结构物进行了大量的计算及比较分析,成果是令人满意的,可以付诸应用。 相似文献
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Composites of starch-g-polyacrylamide, starch, and polyacrylamide have been prepared by gamma radiation-initiated polymerization of acrylamide in the presence of starch in aqueous medium. The polymerization was studied as a function of the (i) amount of water (ii) monomer concentration, and (iii) total dose. The optimum conditions for maximum conversion of the monomer to homopolymer and graft copolymer have been evaluated. Percentage of grafting of polyacrylamide could not be determined precisely as both the homopolymer and the graft are soluble in common solvents and all attempts to separate the graft from the homopolymer were unsuccessful. However, the formation of the starch-g-polyacrylamide copolymer was confirmed by the turbidimetric studies using acetone as a nonsolvent. The products of polymerization of acrylamide in the presence of starch consisted of unreacted starch, starch-g-polyacrylamide, and polyacrylamide and is referred to as the composite. Acrylamide was also polymerized in the absence of starch using γ-rays as means of initiation and the optimum conditions for maximum conversion of acrylamide to polyacrylamide have been evaluated. Viscosity behavior of the composite and polyacrylamide was studied in aqueous medium at 30±0.04°C. The reduced specific viscosity of the aqueous solution of acrylamide and the composite as well was found to increase with increasing dilution, the effect being more pronounced in the composite. This tends to indicate that both the homopolymer and the composite behave as polyelectrolytes. An attempt has been made to explain the polyelectrolytic behavior of the homopolymer and the composite. © 1993 John Wiley & Sons, Inc. 相似文献
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为增强我国通信制造业在全球市场中的核心竞争力,分析发展现状,探讨我国通信制造业转型升级的必要性;基于价值链理论与核心-边缘理论,研究适合我国通信制造业实情的转型升级路径,即核心企业选择构建国家价值链的跨越式转型升级路径,边缘企业选择嵌入全球价值链的渐进式转型升级路径,给出了相应对策。 相似文献
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Ultra-Stable and Sensitive Ultraviolet Photodetectors Based on Monocrystalline Perovskite Thin Films
Xu Li Chang Liu Feng Ding Zheyi Lu Peng Gao Ziwei Huang Weiqi Dang Liqiang Zhang Xiaohui Lin Shuimei Ding Bailing Li Ying Huangfu Xiaohua Shen Bo Li Xuming Zou Yuan Liu Lei Liao Yiliu Wang Xidong Duan 《Advanced functional materials》2023,33(15):2213360
The detection of ultraviolet (UV) radiation with effective performance and robust stability is essential to practical applications. Metal halide single-crystal perovskites (ABX3) are promising next-generation materials for UV detection. The device performance of all-inorganic CsPbCl3 photodetectors (PDs) is still limited by inner imperfection of crystals grown in solution. Here wafer-scale single-crystal CsPbCl3 thin films are successfully grown by vapor-phase epitaxy method, and the as-constructed PDs under UV light illumination exhibit an ultralow dark current of 7.18 pA, ultrahigh ON/OFF ratio of ≈5.22 × 105, competitive responsivity of 32.8 A W−1, external quantum efficiency of 10867% and specific detectivity of 4.22 × 1012 Jones. More importantly, they feature superb long-term stability toward moisture and oxygen within twenty-one months, good temperature tolerances at low and high temperatures. The ability of the photodetector arrays for excellent UV light imaging is further demonstrated. 相似文献