Anti-symplectic involutions with lagrangian fixed loci and their quotients

We study the lagrangian embedding as a fixed point set of anti-symplectic involution on a symplectic 4-manifold . Suppose the fixed loci of are the disjoint union of smooth Riemann surfaces ; then each component becomes a lagrangian submanifold. Furthermore, if one of the components is a Riemann surface of genus , then its quotient has vanishing Seiberg-Witten invariants. We will discuss some examples which allow an anti-symplectic involution with lagrangian fixed loci.

     

Nuclear magnetic resonance shifts in paramagnetic metalloporphyrins and metalloproteins

We report the first detailed investigation of the (1)H, (13)C, (15)N, and (19)F nuclear magnetic resonance (NMR) spectroscopic shifts in paramagnetic metalloprotein and metalloporphyrin systems. The >3500 ppm range in experimentally observed hyperfine shifts can be well predicted by using density functional theory (DFT) methods. Using spin-unrestricted methods together with large, locally dense basis sets, we obtain very good correlations between experimental and theoretical results: R(2) = 0.941 (N = 37, p < 0.0001) when using the pure BPW91 functional and R(2) = 0.981 (N = 37, p < 0.0001) when using the hybrid functional, B3LYP. The correlations are even better for C(alpha) and C(beta) shifts alone: C(alpha), R(2) = 0.996 (N = 8, p < 0.0001, B3LYP); C(beta), R(2) = 0.995 (N = 8, p < 0.0001, B3LYP), but are worse for C(meso), in part because of the small range in C(meso) shifts. The results of these theoretical calculations also lead to a revision of previous heme and proximal histidine residue (13)C NMR assignments in deoxymyoglobin which are confirmed by new quantitative NMR measurements. Molecular orbital (MO) analyses of the resulting wave functions provide a graphical representation of the spin density distribution in the [Fe(TPP)(CN)(2)](-) (TPP = 5,10,15,20-tetraphenylporphyrinato) system (S = (1)/(2)), where the spin density is shown to be localized primarily in the d(xz) (or d(yz)) orbital, together with an analysis of the frontier MOs in Fe(TPP)Cl (S = (5)/(2)), Mn(TPP)Cl (S = 2), and a deoxymyoglobin model (S = 2). The ability to now begin to predict essentially all heavy atom NMR hyperfine shifts in paramagnetic metalloporphyrins and metalloproteins using quantum chemical methods should open up new areas of research aimed at structure prediction and refinement in paramagnetic systems in much the same way that DFT methods have been used successfully in the past to predict/refine elements of diamagnetic heme protein structures.     

Mössbauer quadrupole splittings and electronic structure in heme proteins and model systems: a density functional theory investigation

We report the results of a series of density functional theory (DFT) calculations aimed at predicting the (57)Fe M?ssbauer electric field gradient (EFG) tensors (quadrupole splittings and asymmetry parameters) and their orientations in S = 0, (1)/(2), 1, (3)/(2), 2, and (5)/(2) metalloproteins and/or model systems. Excellent results were found by using a Wachter's all electron basis set for iron, 6-311G for other heavy atoms, and 6-31G for hydrogen atoms, BPW91 and B3LYP exchange-correlation functionals, and spin-unrestricted methods for the paramagnetic systems. For the theory versus experiment correlation, we found R(2) = 0.975, slope = 0.99, intercept = -0.08 mm sec(-)(1), rmsd = 0.30 mm sec(-)(1) (N = 23 points) covering a DeltaE(Q) range of 5.63 mm s(-)(1) when using the BPW91 functional and R(2) = 0.978, slope = 1.12, intercept = -0.26 mm sec(-)(1), rmsd = 0.31 mm sec(-)(1) when using the B3LYP functional. DeltaE(Q) values in the following systems were successfully predicted: (1) ferric low-spin (S = (1)/(2)) systems, including one iron porphyrin with the usual (d(xy))(2)(d(xz)d(yz))(3) electronic configuration and two iron porphyrins with the more unusual (d(xz)d(yz))(4)(d(xy))(1) electronic configuration; (2) ferrous NO-heme model compounds (S = (1)/(2)); (3) ferrous intermediate spin (S = 1) tetraphenylporphinato iron(II); (4) a ferric intermediate spin (S = (3)/(2)) iron porphyrin; (5) ferrous high-spin (S = 2) deoxymyoglobin and deoxyhemoglobin; and (6) ferric high spin (S = (5)/(2)) metmyoglobin plus two five-coordinate and one six-coordinate iron porphyrins. In addition, seven diamagnetic (S = 0, d(6) and d(8)) systems studied previously were reinvestigated using the same functionals and basis set scheme as used for the paramagnetic systems. All computed asymmetry parameters were found to be in good agreement with the available experimental data as were the electric field gradient tensor orientations. In addition, we investigated the electronic structures of several systems, including the (d(xy))(2)(d(xz),d(yz))(3) and (d(xz),d(yz))(4)(d(xy))(1) [Fe(III)/porphyrinate](+) cations as well as the NO adduct of Fe(II)(octaethylporphinate), where interesting information on the spin density distributions can be readily obtained from the computed wave functions.     

Synthesis of (+)-polyoxamic acid and D-sorbitol from simple achiral allylic halides employing (S,S)-hydrobenzoin as a chiral source

Coupling of cis-1-bromo-2-pentene and (S,S)-hydrobenzoin stannylene acetal followed by regio- and stereoselective transformations of the resulting allylic ether gave (+)-polyoxamic acid and a similar procedure was applied to the synthesis of D-sorbitol from trans-1-iodo-2-hexene.     

Synthesis and reversible thermo-induced conformational transitions of a stable nitroxide biradical based on calix[4]arene

A stable paramagnetic calix[4]arene(III) bearing two nitroxide groups on the upper rim is synthesized, which exhibits a strong intramolecular spin-spin exchange interaction and is found to be able to undergo reversible conformational transitions upon heating.     

Indium trichloride mediated intramolecular Prins-type cyclization

[reaction: see text] Intramolecular Prins-type reactions of compounds having both functionalities of homoallyl alcohol and acetal moiety are described. The intramolecular Prins cyclizations were performed using indium trichloride in chloroform or 25% aqueous THF. Both 9-oxabicyclo[3.3.1]nonane and 3,9-dioxabicyclo[3.3.1]nonane compounds were successfully obtained in moderate yields.     

Asymptotic analysis of dielectric coaxial fibers

Using an asymptotic analysis, we analytically calculate the dispersion and the field distribution of guided modes in an all-dielectric coaxial fiber. We compare the analytical results with those obtained from numerical calculations and find excellent agreement between them. We demonstrate that both the Bragg reflection and the total internal reflection play important roles in providing confinement and determining the dispersion characteristics of the coaxial fiber modes.     

x强流相对论环形电子束在低磁场中传输分析

 用理论和粒子模拟相结合的方法分析了强流薄环形相对论电子束在低磁场导引下，在均匀波导，无箔二极管，以及锥形波导和渐减磁场位形条件下的传输过程，研究了束包络的波动和如何减少波动的问题。分析表明：在无箔二极管中一个适当渐增的磁场位形可以有效地抑制束电子的径向运动，从而减少电子在波导中的波动幅度；电子束在锥形波导和渐减磁场位形中运动，不会增加束电子的波动。因此适当的磁场位形可以降低微波器件对导引磁场的要求，有利于实现永磁包装微波器件。     

运动涡旋脉冲引起的光学畸变

 主要研究了气动噪声对光传输和成像的影响。流场求解采用法福尔平均N-S方程，并分别利用基于MUSCL格式的AUSMPW+分裂和二阶中心格式对流通量和粘性通量进行离散处理；用四步四阶Runge-Kutta格式对方程进行时间推进求解，采用J-B两方程模型并经Sarkar方法进行可压缩修正后用于湍流的数值模拟。采用基于光学传递函数的物理光学方法分析平均流动和湍流对光质的影响。研究表明：涡脉冲在运动过程中会引起光束沿涡脉冲运动方向产生较大的整体偏折，偏折幅度随时间而变，最大偏折幅度可以达到1.7 μrad；在与涡脉冲运动的垂直方向，整体偏折基本可以忽略不记。在涡脉冲横穿光束的过程中，平均流动会导致焦平面光强峰值有两次下降，平均流动对光强重新分布的影响比湍流脉动影响更强。涡脉冲在运动过程中，先导致光束能量在与涡脉冲运动垂直的方向上扩散，随后使之在涡脉冲运动方向上向外转移。因能量向外扩散，导致Strehl比在0.9 s时刻降低到0.60左右。     

磁致伸缩-压电联合激励凹筒型发射换能器

设计制作了一种新型磁致伸缩-压电联合激励凹筒型发射换能器,采用稀土超磁致伸缩材料Terfenol-D与PZT压电陶瓷作为联合激励元件,模拟计算与实测结果均表明,与采用单一振子激励的凹筒型发射换能器相比,此种新型换能器在保持尺寸小、频率低等优点的同时,显著拓宽了工作频带并提高了辐射声功率.换能器外型尺寸为φ88 mm×316 mm,水中谐振频率1.30 kHz,-3 dB带通Q值1.43,谐振频率下发射电压响应级135.1 dB.