用于数字化电视信号传输的同轴电缆与光纤的比较

比较同轴电缆和光纤在数字化电视信号传输中的性能，并介绍两种通用型光纤和两种通用型光纤连接器。     

Bias-induced forces in conducting atomic force microscopy and contact charging of organic monolayers

Contact electrification, a surface property of bulk dielectric materials, has now been observed at the molecular scale using conducting atomic force microscopy (AFM). Conducting AFM measures the electrical properties of an organic film sandwiched between a conducting probe and a conducting substrate. This paper describes physical changes in the film caused by the application of a bias. Contact of the probe leads to direct mechanical stress and the applied electric field results in both Maxwell stresses and electrostriction. Additional forces arise from charge injection (contact charging). Electrostriction and contact charging act oppositely from the normal long-range Coulomb attraction and dominate when a charged tip touches an insulating film, causing the tip to deflect away from the film at high bias. A bias-induced repulsion observed in spin-coated PMMA films may be accounted for by either mechanism. In self-assembled monolayers, however, tunnel current signals show that the repulsion is dominated by contact charging.     

First-principles investigation of ag-doped gold nanoclusters

Gold nanoclusters have the tunable optical absorption property, and are promising for cancer cell imaging, photothermal therapy and radiotherapy. First-principle is a very powerful tool for design of novel materials. In the present work, structural properties, band gap engineering and tunable optical properties of Ag-doped gold clusters have been calculated using density functional theory. The electronic structure of a stable Au(20) cluster can be modulated by incorporating Ag, and the HOMO-LUMO gap of Au(20-) (n)Ag(n) clusters is modulated due to the incorporation of Ag electronic states in the HOMO and LUMO. Furthermore, the results of the imaginary part of the dielectric function indicate that the optical transition of gold clusters is concentration-dependent and the optical transition between HOMO and LUMO shifts to the low energy range as the Ag atom increases. These calculated results are helpful for the design of gold cluster-based biomaterials, and will be of interest in the fields of radiation medicine, biophysics and nanoscience.     

Synthesis and anti-HIV activity of aryl-2-[(4-cyanophenyl)amino]-4-pyrimidinone hydrazones as potent non-nucleoside reverse transcriptase inhibitors

A series of novel diarylpyrimidines (DAPYs) with a ketone hydrazone substituent on the methylene linker between the pyrimidine nucleus and the aryl moiety at the C‐4 position were synthesized, and their antiviral activity against human immunodeficiency virus (HIV)‐1 in MT‐4 cells was evaluated. Most compounds of this class exhibited excellent activity against wild‐type HIV‐1, with EC₅₀ values in the range of 1.7–13.2 nM . Of these compounds, 2‐bromophenyl‐2‐[(4‐cyanophenyl)amino]‐4‐pyrimidinone hydrazone ( 9 k ) displayed the most potent anti‐HIV‐1 activity (EC₅₀=1.7±0.6 nM ), with excellent selectivity for infected over uninfected cells (SI=5762). In addition, the 4‐methyl phenyl analogue 9 d (EC₅₀=2.4±0.2 nM , SI=18461) showed broad spectrum HIV inhibitory activity, with EC₅₀ values of 2.4±0.2 nM against wild‐type HIV‐1, 5.3±0.4 μM against HIV‐1 double‐mutated strain RES056 (K103N+Y181C), and 5.5 μM against HIV‐2 ROD strain. Furthermore, structure–activity relationship (SAR) data and molecular modeling results for these compounds are also discussed.     

Relationship between serum concentrations of polychlorinated biphenyls and organochlorine pesticides and dietary habits of pregnant women in Shanghai

The use of most polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) has been restricted in China; however, their use remains a concern because of their adverse effects on human health, especially on fetuses and infants. To date, there is no data regarding the exposure levels of pregnant women to PCBs and OCPs in Shanghai. In order to evaluate PCB and OCP exposure levels and the contribution of dietary habits to these levels, we determined the concentrations of 8 PCBs and 14 OCPs in the umbilical cord blood serum of healthy pregnant women in Shanghai. Dietary habits of the pregnant women were obtained from a self-administered questionnaire. Results showed that p, p′-DDE, HCB and β-HCH were the major pollutants present in the serum samples; PCBs were detected in a few samples at low concentrations. Age, weight and body mass index before delivery were positively associated with serum levels of p, p′-DDE and β-HCH. Women and their husbands who had higher education levels, higher income levels, tended to have higher levels of p, p′-DDE and β-HCH. Spearman correlation analysis results suggested that consumption of foods such as milk, eggs, meat, fish, and shrimp may contribute to higher serum levels of p, p′-DDE and β-HCH. Furthermore, multiple linear regression analyses indicated that the age and educational levels of the pregnant women and their intake of fried/flamed food and shellfish were positively associated with β-HCH levels, and that the age and educational levels of the pregnant women and their intake of parity, beef, pork, mutton, and shrimp were positively associated with p, p′-DDE levels. This is the first study to investigate the exposure levels of pregnant women to PCBs and OCPs in Shanghai, and it should provide useful information for future related research.     

Sensitive discrimination and detection of prion disease-associated isoform with a dual-aptamer strategy by developing a sandwich structure of magnetic microparticles and quantum dots

The major challenge of prion disease diagnosis at the presymptomatic stage is how to sensitively or selectively discriminate and detect the minute quantity of disease-associated prion protein isoform (PrP(Res)) in complex biological systems such as serum and brain homogenate. In this contribution, we developed a dual-aptamer strategy by taking the advantages of aptamers, the excellent separation ability of magnetic microparticles (MMPs), and the high fluorescence emission features of quantum dots (QDs). Two aptamers (Apt1 and Apt2), which can recognize their two corresponding distinct epitopes of prion proteins (PrP), were coupled to the surfaces of MMPs and QDs, respectively, to make MMPs-Apt1 and QDs-Apt2 ready at first, which then could be coassociated together through the specific recognitions of the two aptamers with their two corresponding distinct epitopes of PrP, forming a sandwich structure of MMPs-Apt1-PrP-Apt2-QDs and displaying the strong fluorescence of QDs. Owing to the different binding affinities of the two aptamers with PrP(Res) and cellular prion protein (PrP(C)), both of which have distinct denaturing detergent resistance, our dual-aptamer strategy could be applied to discriminate PrP(Res) and PrP(C) successfully in serum. Further identifications showed that the present dual-aptamer assay could be successfully applied to the detection of PrP in 0.01% brain homogenate, about 1000-fold lower than that of commonly applied antibody-mediated assays, which can detect PrP just in 10% brain homogenate, indicating that the present designed dual-aptamer assay is highly sensitive and adequate for clinical diagnosis without isolation of target protein prior to assay.     

Antibacterial silver-containing silica glass prepared by ion implantation

Recently, there is much interest in nanocomposites consisting of metal nanoparticles dispersed in dielectric matrix. Silver is the first candidate used in antibacterial research. In the present study, sliver-containing silica glass is prepared by ion implantation. The bactericidal properties of Ag-implanted samples are investigated using E. coli. The implanted samples are characterized by optical absorption spectroscopy, atomic force microscopy and transmission electron microscopy. The size and position of the silver nanoparticles formed by ion implantation can be optimized by adjusting the implanted process parameters. All the implanted samples show antibacterial properties. But the samples with silver nanoparticle-enriched surfaces possess excellent antibacterial properties in comparison with other implanted samples. This indicates that ion implantation is a potential method for synthesizing antibacterial biomaterials.     

光缆及其系统的设计基础

为光缆系统的初学者和有扎实基础的专家提供光纤技术基本的背景信息和光缆系统的设计准则。     

XLPE电线／光纤复合海缆

１９９２年藤仓公司向中国电力公司提供了一根６６ｋＶ交联聚乙烯（ＸＬＰＥ）绝缘电线／光纤复合海缆。海缆可能会遭受船锚或捕鱼设备严重的机械损伤。检测海缆的机械损伤，是提高海缆传输传可靠性的一种极为有用的技术。中国电力公司和藤仓公司研制出机械损坏检测光纤传感器。制作了一根试验用含机械损坏检测传感器的６６ｋＶＸＬＰＥ海缆，压缩试验证实了该传感器的可行性。光纤受外来因素损坏时，传输损耗会增加。我们可以通过观