双轴晶体主平面上倍频的相位匹配

从折射率椭球方程和折射率椭球面出发，讨论光束在双轴晶体中传播及偏振的特性、主平面倍频共线相位匹配（PM）问题，得到了双轴晶体主平面内激光所有可能PM倍频的8种偏振组合及其相应的PM角公式、有效非线性（NL）系数deff的一般表达式。结果表明：得到的公式简单，可大大简化PM参数计算及优化设计；折射率椭球面是单层曲面，比双层的折射率面简单；基于折射率椭球面寻找所有可能PM的类型、偏振组合的方法物理图像简明，易于理解，大大降低了双轴晶体PM问题分析的难度。     

Structure and electrochemical behaviour of 4,7-diazaheptyl-trimethoxy-silane and vinyl-trialkoxy-silane adsorbed at silver surface

Novel self-assembled monolayers were obtained on silver using 4,7-diazaheptyl-trimethoxy-silane (SiN) and vinyl-trialkoxy-silane (SiVA, where the alkyl group is 3,6,9,12,15,18,21,24,27,30,33,36,39,42,45,48,51,54,57,60-eicozaoxa- hexaheptaconan). It was shown that thus modified metal surface was protected against electrooxidation. A densely packed monolayer remained stable and did not desorb from the Ag electrode on the potential cycling. The structure of SiN and SiVA as well as their complexes with Li⁺ cations were calculated and visualised by the AM1d and PM5 semi-empirical methods.     

Deorthogonalization of ODS-CDMA QPSK by AM/PM Nonlinearity

When using a conventional demodulator, a sufficient condition to maintain ODS-CDMA codeword orthogonality is constant relative channel amplitude over the codeword duration. When transmitted over a memoryless, AM/PM nonlinearity channel, the chip-to-chip fluctuating amplitude of a composite ODS-CDMA QPSK waveform produces a chip-to-chip fluctuating phase that deorthogonalizes the ODS-CDMA codewords, resulting in an additional multiple access self-interference similar to that found in asynchronous DS-CDMA. For ODS-CDMA QPSK in an AM/PM nonlinearity channel, we utilize the Central Limit Theorem, derive, and evaluate: (i) an expression for the signal-to-distortion ratio at the demodulator output, (ii) an expression for the uncoded bit error probability, and (iii) an upper bound on the convolutionally-coded bit error probability. We find that the degradation to BER depends on both the AM/PM nonlinearity slope and the ODS-CDMA channel loading.     

多信道E1映射复用成帧芯片PM8316及其应用

PM8316是PMC-Sierra公司生产的一种低功耗、高性能的多信道E1映射复用成帧芯片。该芯片内部集成了映射器、复用器、成帧器，其处理容量为63路E1，并含有8位微处理器总线接口和5个标准信号的JTAG测试端口，可支持收发抖动衰减。文中介绍了PM8316的主要功能和接口，给出了它在SDH终端设备中的主要信号电路框图。     

环己硅烷类液晶化合物的量子化学研究

运用AM1和PM3两种SCF-MO方法，通过能量梯度全优化计算，给出20种环己硅烷类（苯基乙烷系）液晶化合物的稳定几何构型、电子结构和基本性质．联系有机电子结构理论进行了细致的讨论．     

Analysis of the effect of the electronic structure of the Cl atom in complexes of chlorides of group IV elements on Cl NQR frequency and asymmetry parameter

Analysis of changes in ³⁵Cl NQR frequency of complexes MCl₄.L and MCl₄.2L for M = Si, Ge, Sn and Ti was performed. The population of the atomic orbitals was calculated by the quantum chemistry methods PM3 and INDO. The results provided an explanation of the changes in ³⁵Cl NQR frequency and the asymmetry parameter upon complex formation. In the complexes of non-transition elements, a decrease in ³⁵Cl NQR frequency is first of all related to increasing population of p_z orbitals on Cl atoms. In the complexes of Ti, the increase in ³⁵Cl NQR frequency depends on a decrease in the p_π to d_π electron density transfer.     

Theoretical Investigation on the Second-order Nonlinear Optical Properties of Chiral Amino Acid Zinc（Ⅱ） Porphyrins

Static second-order nonlinear optical effects of amino acid zinc(Ⅱ) porphyrins 1, 2,3 and 4 were calculated by the TDHF/PM3 method based on the molecular structures optim.zed at the semiempirical PM3 quantum chemistry level, showing due to the cancellation of symmetric center, these amino acid zinc(H) porphyrins exhibit second order nonlinear optical response. The analysis of β components indicated that these amino acid zinc(Ⅱ) porphyrins are of multipolarizabilities, and they may be ascribed as the “mixture” of octupolar and dipoar molecules with ||βJ=3||/||βJ=1||≈5. It is found that there are no significant differences between the static β values of non-chiral and chiral amino acid zinc(Ⅱ) porphyrins. However, the βxyz component, which is quite important to quadratic macroscopic X^(2) susceptibility of chiral material, is increased significantly with the increase of side chain group of amino acids.     

The role of C-centered radicals on the mechanism of action of artemisinin

Artemisinin is a sesquiterpene lactone with an endoperoxide function that is essential for its antimalarial activity. Endoperoxides are supposed to act on heme leading to the reduction of the peroxide bond and production of radicals, which can be responsible for killing the parasite. The geometries of artemisinin, radical anions and neutral species generated by rearrangement after reduction of the peroxide bond were fully optimized with the AM1 and PM3 semi-empirical methods, in order to characterize the intermediates formed during the process. Among the radicals calculated along the pathway for reductive decomposition of artemisinin, the secondary radical centered on carbon C₄ has the highest stability when compared to other radicals that can be achieved either by hydrogen migration to the original O-centered radical or by homolytic break of C–C bond. This suggests that the C₄-centered radical may be the species responsible for killing the parasite, as has been indicated previously in experimental studies.     

Synthesis of (+)-goniothalesdiol and (+)-7-epi-goniothalesdiol

A total synthesis of (+)-goniothalesdiol, a 3,4-dihydroxy-2,5-disubstituted tetrahydrofuran isolated from Goniothalamus borneensis (Annonaceae), and its 7-epimer is reported using oxycarbonylation methodology for construction of polyhydroxylated substituted heterocycles. Diastereoselectivity of addition of organometallic reagents to 2,3-O-isopropylidene-d-threose derivatives using theoretical calculations based on the semiempirical PM5 was studied.     

Theoretical investigation of 1,4-dioxane complexes with water in the <Emphasis Type="Italic">chair</Emphasis> conformation by semiempiric MNDO/PM3 method

The structure and relative stability of 1,4-dioxane-water, (Diox)_n·(H₂O )_m (n = 1, 2, m = 1–6), molecular complexes have been calculated by semiempirical MNDO/PM3 method. A considerable variety of (Diox)_n·(H₂O )_m isomeric structures was stated. The mean energy of O_Diox…H_W-O_W hydrogen bond in (Diox)_n·(H₂O)_m complexes formed by 1,4-dioxane molecules in the chair conformation amounts to ?2.293 ± 0.210 kcal/mol with the average bond length 2.797 0.015 Å.