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991.
We proposed a 1 × 2 and 2×2 SOI switches for applying in fiber optic communication network. The optical path loss and signal-to-noise ratio are evaluated and compared in this paper. 相似文献
992.
We compared efficiencies of different PMD compensation feedback methods against transmission signal bandwidth,including NRZ, RZ, CRZ format under various duty cycles. We found that the critical factor determining the efficiency of PMD compensation is not the modulation format, but the spectral bandwidth of the transmission signal. 相似文献
993.
A semi-classical quantum theory of the cyclotron radiation of the nonrelativistic thermal electrons in a very strong magnetic
field is presented. The basic formulae of the absorption coefficient of cyclotron resonancek
vand the absorption (scattering) cross-section of cyclotron resonance σ
v
have been derived under the quadrupole approximation. σ
v
is an important quantity in the study of the “magnetic inverse-Compton scattering”. It is shown that σ
v
is greatly larger than the Thomson cross-sectron σT, which is important in discussing the magnetic inverse-Compton scattering of the relativistic electrons in a very strong
magnetic field.
Project supported by the National Natural Science Foundation of China and the Climbing Plan. 相似文献
994.
A discrete three trophic level food chain model with ratio-dependent Michaelis-Menten type functional response is investigated. It is shown that under some appropriate conditions the system is permanent. The results indicate that, to make the species coexist in the long run, it is a surefire strategy to keep the death rate of the predator and top predator rather small and the intrinsic growth rate of the prey relatively large. 相似文献
995.
Ming Xu Yong Ji Jing‐Lin Zuo Yi‐Zhi Li Xiao‐Zeng You 《Journal of heterocyclic chemistry》2005,42(5):847-850
Two new unsymmetrical tetrathiafulvalene (TTF) derivatives, 2,3‐bis(cyanoethylthio)‐6,7‐(methyl‐ethylenedithio)tetrathiafulvalene ( 6a ) and 2,3‐bis(cyanoethylthio)‐6,7‐(cyclopentodithio)tetrathiafulvalene ( 6b ), have been prepared and characterized by NMR, MS, IR and Elemental analyses. The molecular structures have been determined by X‐ray crystallography. Their redox properties have been investigated by cyclic voltammetry in dichloromethane solution and each compound shows two reversible single‐electron redox couples. 相似文献
996.
Yu‐Liang Yang Dr. Wen‐Ying Liao Wan‐Yun Liu Chih‐Chuang Liaw Dr. Chia‐Ning Shen Dr. Zih‐You Huang Shih‐Hsiung Wu Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(43):11573-11580
Six photosensitive polyketides, malbranpyrroles A–F, were discovered from the thermophilic fungus Malbranchea sulfurea by using intact‐cell desorption/ionization on silicon mass (ICD‐MS) and LC‐SPE‐NMR. These two strategies facilitate the searching and structural determination of unstable natural products. The ICD‐MS indicated that only brown hyphae of M. sulfurea can produce malbranpyrroles. The biosynthetic pathway of malbranpyrroles was evidenced by 13C isotope precursors and amino acid feeding experiments. The cytotoxicity data revealed that the conformation of the conjugated system in malbranpyrroles does not affect cytotoxic potency against cancer cell lines. In addition, the chlorine atom was shown to be the pharmacophore for cytotoxicity. 相似文献
997.
Wen‐Na Zhao Lei Han Cheng‐Cai Luo 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(8):m280-m282
The title novel mixed μ2‐SH‐ and μ3‐SH‐bridged tetranuclear copper(I) complex, cyclo‐bis[μ2‐bis(diphenylphosphino)amine]di‐μ3‐sulfanido‐di‐μ2‐sulfanido‐tetracopper(I) methanol disolvate, [Cu4(SH)4(C24H21NP2)2]·2CH3OH, has crystallographically imposed centrosymmetry and affords a neutral Cu4S4 core with a distorted step‐like structure. The distances of 2.8458 (16) and 2.8179 (16) Å between copper(I) centres indicate the presence of ligand‐supported Cu...Cu interactions. Strong N—H...O and O—H...S hydrogen bonds between the tetranuclear cluster and methanol solvent molecules result in a two‐dimensional hydrogen‐bonded supramolecular network. This complex is the first example of a coinage tetranuclear metal complex with mixed μ2‐SH‐ and μ3‐SH‐bridged chromophores. 相似文献
998.
第二代H1抗组胺类药物——依巴斯汀 总被引:1,自引:0,他引:1
概述了近年来国内外依巴斯汀的研究及生产状况,对其合成路线进行了较深入的介绍,同时展望了依巴斯汀在医药领域的发展前景. 相似文献
999.
人工神经网络应用于维生素B族4组分同时测定 总被引:7,自引:0,他引:7
应用人工神经网络原理,采用Levenberg-Marquardt BP算法,对于吸收光谱严重重叠的维生素B1,B2,B6和烟酰胺4组分同时进行含量测定。四者的平均回收率分别为100%,98%,96%,100%。该方法用于复合维生素B片剂中B1,B2,B6和烟酰胺的同时测定,获得较满意的结果。实验表明,该方法与现有的算法相比具有训练速度快、预测结果准确度高等特点,有望能成为多组分分析的有效方法之一。 相似文献
1000.
In this work, a novel flow-through solid-phase based chemiluminescence (CL) optical sensor is described for the trace determination of orthophosphate in waters exploiting the multisyringe flow injection analysis (MSFIA) concept with multicommutation. The proposed time-based injection flow system relies upon the in-line derivatisation of the analyte with ammonium molybdate in the presence of vanadate, and the transient immobilisation of the resulting heteropolyacid in a N-vinylpyrrolidone/divinylbenzene copolymer packed spiral shape flow-through cell located in front of the window of a photomultiplier tube. The simultaneous injection of well-defined slugs of luminol in alkaline medium and methanol solution towards the packed reactor is afterwards performed by proper switching of the solenoid valves. Then, the light emission from the luminol oxidation by the oxidant species retained onto the sorbent material is readily detected. At the same time, the generated molybdenum-blue compound is eluted by the minute amount of injected methanol, rendering the system prepared for a new measuring cycle. Therefore, the devised sensor enables the integration of the solid-phase CL reaction with elution and detection of the emitted light without the typical drawbacks of the molybdenum-blue based spectrophotometric procedures regarding the excess of molybdate anion, which causes high background signals due to its self-reduction. The noteworthy features of the developed CL-MSFIA system are the feasibility to accommodate reactions with different pH requirements and the ability to determine trace levels of orthophosphate in high silicate content samples (Si/P ratios up to 500). Under the optimised conditions, a dynamic linear range from 5 to 50 μg P l−1 for a 1.8 ml sample, repeatability better than 3.0% and a quantification limit of 4 μg P l−1 were attained. The flowing stream system handles 11 analysis h−1 and has been successfully applied to the determination of trace levels of orthophosphate in environmental samples such as mineral, ground, tap and pond waters as well as samples from a water-steam cycle of an incineration plant. The t-test comparison of the means for the developed optical sensor and the molybdenum-blue spectrophotometric APHA/AWWA/WPCF reference method revealed that there is no evidence of significant differences between the obtained results at the 95% confidence level. 相似文献