ON THE RIEMANNIAN SPACES ADMITTING PARALLEL YANG-MILLS FIELDS

如果一个Yang-Mills场(规范群为任意李群)的场强的所有规范导数均为0,则称这个场为平行的Yang-Mills场.平行规范场是微分几何中对称空间的推广,它是Yang-Mills方程的特解. 本文的主要结果是下列两个定理： 定理1 容有非平凡的平行Yang-Mills场的四维黎曼空间必须是Kahler流形或半对称空间.这里半对称流形是满足 \[R_{ijkl}^ - = 0\](或\[R_{ijkl}^ + = 0\]) 的黎曼流形,其中\[R_{ijkl}^ \pm \]分别是曲率张量的自对偶部份及反自对偶部份,而":"表示共变 导数. 定理2 半对称空间如果不是对称空向,则必为Kahler-Einstein空间或共形半平坦Einstein空间.这里共形半平坦是指Weyl张量的反自对偶部份或自对偶部份为0.在附录中作者给出了二维黎曼流形上Yang-Mills方程的所有的整体解.     

Oxidatively truncated docosahexaenoate phospholipids: total synthesis,generation, and Peptide adduction chemistry

The recent immunological detection of extraordinarily high levels of carboxyethylpyrrole (CEP) modifications of proteins from the retinas of individuals with age-related macular degeneration provided presumptive evidence for the involvement of docosahexaenoate-derived oxidatively truncated phospholipids in retinal pathology. To facilitate the in vivo detection and characterization of the chemistry and biological activities of these postulated naturally occurring molecules, a family of oxidatively truncated phospholipids was prepared by total syntheses. Their formation in oxidation reactions of a docosahexaenoate ester of 2-lysophosphatidylcholine (DHA-PC) was also demonstrated. Free radical-induced oxidative cleavage of DHA-PC promoted by myeloperoxidase or copper ions generates similar mixtures of these phospholipids. The most abundant products were 1-palmitoyl-2-succinoyl-sn-glycero-3-phosphatidylcholine (4.7%) and 2-(6-carboxy-4-oxohex-5-enoyl)-1-palmitoyl-sn-glycero-3-phosphatidylcholine (1.7%). Both of these oxidatively truncated phospholipids are homologues of biologically active arachidonate-derived phospholipids. A minor product from DHA-PC, 2-(4-hydroxy-7-oxohept-5-enoyl)-1-palmitoyl-sn-glycero-3-phosphatidylcholine (0.4% yield), reacted with the epsilon-amino group of a peptide lysyl residue to produce a CEP derivative in 0.7% yield. These observations support the previous conclusion, based on immunological evidence, that CEPs are generated by the reaction of an oxidatively truncated phospholipid with proteins in the retina and further indicate that CEP protein modifications probably represent only a tiny fraction of the products generated upon oxidative damage of DHA-PC in photoreceptor disk membranes.     

Two-photon excitation studies of hypocrellins for photodynamic therapy

The photophysical and photochemical properties of hypocrellins (HA and HB) are examined with two-photon excitations at 800 nm using femtosecond pulses from a Ti:sapphire laser. The two-photon excited fluorescence spectra of HA and HB are very similar to those obtained by one-photon excitation, which may indicate that the two-photon induced photodynamic processes of hypocrellins are similar to one-photon induced photodynamic processes. The two-photon excitation cross sections of HA and HB are measured at 800 nm as about 34.8 x 10(-50) cm(4) s/photon and 21.3 x 10(-50) cm(4) s/photon, respectively. The large two-photon cross sections of both HA and HB, suggest that the hypocrellins can be potential two-photon phototherapeutic agents. As an example for two-photon photodynamic therapy of hypocrellins, we also further examine the cell-damaging effects of HA upon two-photon illumination. Our preliminary results of cell viability test indicate hypocrellins can effectively damage the Hela cells under two-photon illumination.     

In situ tissue pathology from spatially encoded mass spectrometry classifiers visualized in real time through augmented reality

Integration between a hand-held mass spectrometry desorption probe based on picosecond infrared laser technology (PIRL-MS) and an optical surgical tracking system demonstrates in situ tissue pathology from point-sampled mass spectrometry data. Spatially encoded pathology classifications are displayed at the site of laser sampling as color-coded pixels in an augmented reality video feed of the surgical field of view. This is enabled by two-way communication between surgical navigation and mass spectrometry data analysis platforms through a custom-built interface. Performance of the system was evaluated using murine models of human cancers sampled in situ in the presence of body fluids with a technical pixel error of 1.0 ± 0.2 mm, suggesting a 84% or 92% (excluding one outlier) cancer type classification rate across different molecular models that distinguish cell-lines of each class of breast, brain, head and neck murine models. Further, through end-point immunohistochemical staining for DNA damage, cell death and neuronal viability, spatially encoded PIRL-MS sampling is shown to produce classifiable mass spectral data from living murine brain tissue, with levels of neuronal damage that are comparable to those induced by a surgical scalpel. This highlights the potential of spatially encoded PIRL-MS analysis for in vivo use during neurosurgical applications of cancer type determination or point-sampling in vivo tissue during tumor bed examination to assess cancer removal. The interface developed herein for the analysis and the display of spatially encoded PIRL-MS data can be adapted to other hand-held mass spectrometry analysis probes currently available.

Integration between a hand-held mass spectrometry desorption probe based on picosecond infrared laser technology (PIRL-MS) and an optical surgical tracking system demonstrates in situ tissue pathology from point-sampled mass spectrometry data.     

消旋反式菊酸α—氰基—4—氟—3—苯氧基苄酯的合成

含氟拟除虫菊酯的合成是近年来新型高效拟除虫菊酯研究工作的方向之一。该类化合物由于具有高效、低毒、广谱、低残留、无致癌、致畸作用,有的还具有低鱼毒,杀螨的特性,因此倍受注目。西德拜尔公司开发的百治菊酯(Baythroid)(1)便是其中一种高效杀虫剂。     

Kinetics of zinc and cadmium dissociation of metallothionein in the presence of chelating agents

The dissociation kinetics of metal ions from native metallothionein (Cd₅Zn₂-MT) of rat liver has been studied in the presence of external ligands including amino acids, peptide and polyamino polycarboxylic acids at 25°C. The study shows that the solution pH affects the metal dissociation process. Different ligands present different multiphasic kinetics. The possible mechanism of metal dissociation from metallothionein has been proposed.     

New Monoterpene-Substituted Dihydrochalcones from Piper aduncum

Five New unusual monoterpene-substituted dihydrochalcones, the adunctins A–E (1″S)-1-{2′-hydroxy-4′-methoxy-6′-[4″-methyl-1″-(1?-methylethyl)cyclohex-3″ -en-1″ -yloxy]phenyl}-3-phenylpropan-1-one ( 1 ), (5aR*,8R*,9aR*)-3-phenyl-1-[5′,8′,9′,9′a-tetrahydro-3′-hydroxy-1′-methoxy-8′-(1″-methylethyl)-5′-a-methyldibenzo-[b,d]furan-4′-yl]propan-1-one ( 2 ), (2′R*,4″S*)-1-{6′-hydroxy-4′-methoxy-4″-(1?-methylethyl)spiro[benzo[b]-furan-2′(3′H),1″ -cyclohex-2″ -en]-7′-yl}-3-phenylpropan-1-one ( 3 ), (2′R*,4″R*)-1-{6′-hydroxy-4′-methylethyl-4″-(1?-methylethyl)spiro[benzo[b]furan-2′(3′H),1″-cyclohex-2″-en]-7′-yl}-3-phenypropan-1-one ( 4 ), and (5′aR*,6′S*, 9′R*,9′aS*)-1-[5′a,6′,7′,8′,9′a-hexahydro-3′,6′-methoxy-6′-methyl-9′-(1″-methylethyl)dibenzo[b,d]-furan-4′-yl]-3-phenylpropan-1-one ( 5 ) were isolated from the leaves of Piper aduncum (Piperaceae) by preparative liquid chromatography. In addition, (?)-methyllindaretin ( 6 ), trans-phytol, and α-tocopherol ( = vitamin E) were also isolated and identified. The structures were elucidated by spectroscopic methods, including 1D- and 2D-NMR spectroscopy as well as single-crystal X-ray diffraction analysis. The antibacterial and cytotoxic potentials of the isolates were also investigated.     

Single electron emission from the closed-tips of single-walled carbon nanotubes

The single electron emission behaviors and characteristics from the well-defined quantized energy levels, corresponding to localized electronic states at the dome-structure tips, in single-walled carbon nanotubes (SWNTs) are investigated and illuminated by use of the energy level emission model in combination with the first-principles calculations on the electronic structures. Under the external electric field, the confined electrons are emitted simultaneously from each quantized energy level by virtue of the resonant tunneling effects. With increasing applied voltage, the emission current increases monotonically and exponentially up to the first peak value, and then steps into the increasing and decreasing "sawtoothlike" variations in sequence. The negative differential resistance or conductivity and the maximum current for SWNTs are simulated. The influences of localized electronic states and curvatures of the different closed tips on the single electron emission behaviors of SWNTs are evaluated and discussed. Also a few issues and applications relevant to electron emission of carbon nanotubes are addressed.     

Electrocatalysis of cytochrome c at a C(60)-gamma-cyclodextrin and Nafion chemically modified electrode

The C(60)-gamma-cyclodextrin and Nafion chemically modified electrode exhibits two redox waves by cyclic voltammetry. Such an electrode will effect reduction and oxidation of cytochrome c and be capable of mediating the electron transfer to cytochrome c.     

Schiff碱配合物的研究——Ⅸ.表面Schiff碱配合物对H2O2分解的催化作用

制备了两种表面Schiff碱及其Cu²⁺、Co²⁺、Ni²⁺、Zn²⁺配合物,考察了它们对H₂O₂分解的催化性能,其活性顺序为:Co²⁺>Cu²⁺>Ni²⁺>Zn²⁺,且与金属离子氧化还原电位有关。溶液的pH值增加有利于催化反应,有机配体的加入则对反应有所抑制。