汉字的S—E坐标提取及其骨架重构

本文从手写印刷体汉字的计算机光学输入的离散模式出发,提出一种称为S-E坐标的特征提取的新方法。S-E坐标的特征提取及基于S-E坐标的汉字骨架重构在快速实时、数据压缩、畸变消减以及抗干抗性等方面优于通常的细化算法。最后简介基于S-E坐标的汉字识别法。分析与实验表明,S-E坐标为进一步的特征提取和汉字识别提供了一种有效的工具。     

磷脂核苷缀合物甘油结构修饰新方法及应用

通过环甘油磷脂核苷缀合物的亲核开环,为甘油结构修饰提供了一条简便有效的新路线.三乙胺对环甘油磷脂核苷缀合物的亲核开环,在室温下就能进行,合成了一类结构新型的以卵磷脂类似物作载体的核苷前药.     

Crystal and molecular structure of (1S,2S,4aS, 8aS)-N-(N-allyldiaminomethanethione)-1-(2-hydroxy-2,5,5,8a-tetramethyldecahydronaphthalenyl) acetamide

Crystal and molecular structure of a new homodrimanic compound (1S,2S,4aS, 8aS)-N-(N-allyldiaminomethanethione)-1-(2-hydroxy-2,5,5,8a-tetramethyldecahydronaphthalenyl) acetamide has been determined by X-ray diffraction analysis. The crystal is monoclinic, unit cell parameters are: a = 9.577(2) Å, b = 7.414(1) Å, c = 16.856(3) Å; β = 94.83(3)°, space group P2₁, Z = 2, of composition C₂₀H₃₅N₃O₂S. Two cyclohexan fragments have ordinary structure and chair-configuration typical of this compound class in homodrimanic skeleton. Ethanol molecule is located in the outer sphere. The withdrawal of carbon atoms from planar fragments of cyclohexan rings varies within the limits from 0.722(5) Å to − 0.634(5) Å. A dihedral angle between the mean-square planes of the latter equals 16.0(2)°, torsion angle (5)-(5)-(10)-(16) 171.0(1)° indicates their trans-joint. In the side non linear chain allyl group is connected to terminal nitrogen atom of thiosemicarbazide molecule. Intermolecular hydrogen bonds between carbonyl atom of acetamide fragment, ethanol molecule, and donor-acceptor groups of thiosemicarbazide moiety play the main part in crystal structure organization. Original Russian Text Copyright ? 2005 by E. P. Styngach, S. T. Malinovskii, L. P. Bets, L. A. Vlad, M. Gdanets, and F. Z. Makaev __________ Translated from Zhurnal Strukturnoi Khimii, Vol. 46, No. 4, pp.785–789, July–August, 2005.     

铁基金属有机凝胶衍生的三氧化二铁纳米片用于光芬顿降解罗丹明B

光催化剂在工业废水处理中发挥着重要作用. 本工作以室温下一步合成的片状铁基金属有机凝胶(Fe-based Metal-organic gel, Fe-MOG)为前驱体, 在不同温度下煅烧得到了片状(300-Fe₂O₃和400-Fe₂O₃)和球形(500-Fe₂O₃和600-Fe₂O₃)两种形貌的衍生三氧化二铁(Fe₂O₃). 通过一系列测试手段对衍生Fe₂O₃的晶体结构和光电性能进行了表征. 其中, 具有碳骨架结构的400-Fe₂O₃因其优良的电子传输性能和较高的光生电荷分离效率表现出优异的光催化活性, 可在中性条件下60 min内光降解97.5%的罗丹明B (Rh B), 并且在连续五次循环实验后其降解效率仍能达到85.3%. 本工作为开发和设计具有优异催化活性的半导体光催化剂提供了新的思路.     

多环笼状骨架有机物的简易命名法*

将多环笼状骨架有机物在绘图软件ChemDraw中用“橡皮擦”分步擦去短桥转化为二环体系明确其主环和主桥头,其后在此化合物的结构式中用记号标明其主环和主桥头,按多环化合物的编号原则进行编号命名,即可得到此复杂结构有机物的命名。     

Group 14 chalcogenides featuring a bicyclo[3.3.0]octane skeleton

Reactions of mixtures of Cl₂MeSiSiMeCl₂ (1) and Me₂MCl₂ (M=Si, Ge, Sn) with either H₂S/NEt₃ or Li₂E (E=Se, Te) yielded the bicyclo[3.3.0]octanes Me₂M(E)₂Si₂Me₂(E)₂MMe₂. A carbon containing analog, (CH₂)₅C(S)₂Si₂Me₂(S)₂C(CH₂)₅, was prepared from 1 and (CH₂)₅C(SH)₂. Crystal structures of three of these compounds were determined and the observed conformations of the bicyclo[3.3.0]octane skeletons compared with results of density functional theory calculations. Another class of silchalcogenides featuring a bicyclo[3.3.0]octane skeleton, E(Me₂Si)₂Si₂Me₂(SiMe₂)₂E, was formed from the doubly branched hexasilane (ClMe₂Si)₂Si₂Me₂(SiMe₂Cl)₂ and H₂S/NEt₃ or Li₂E. All products were characterized by multinuclear NMR (¹H, ¹³C, ²⁹Si, ⁷⁷Se, ¹¹⁹Sn, and ¹²⁵Te).     

Formal total synthesis of (−)-hamigeran B from a chemo-enzymatically prepared building block with quaternary chiral center

A formal total synthesis of (?)-hamigeran B was achieved in 17 steps from commercially available ethyl 2-oxocyclopentanecarboxylate. Carbonyl reductase-catalyzed asymmetric reduction and the subsequent chemical transformations furnished an enantiomerically pure synthetic intermediate, (R)-5-formyl-2-isopropyl-5-methylcyclopent-1-en-1-yl trifluoromethylsulfonate. Suzuki-Miyaura coupling with Gao's arylboronate [2-(2-formyl-3-methoxy-5-methylphenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane], under PdCl₂(dppf)?CH₂Cl₂ catalysis, and the subsequent cyclization by way of intramolecular reductive SmI₂-mediated 1,2-diol formation provided a tricyclic skeleton with a tetrasubstituted double bond between C-1 and C-9b. Upon hydrogenation of this double bond, the proper stereochemistry of the remaining chiral centers was established. Exclusive addition of the hydrogen atom from the β-face occurred, owing to the shielding of the α-face with a bulky TBS protective group on the C-4 alcohol. The hydrogenation products were transformed into Clive's synthetic precursor for (?)-hamigeran B.     

Single-Fluorophore Dynamic Imaging in Living Cells

Recently, observation and tracking of single fluorophores, which we term single fluorophore dynamic imaging (SFDI) in this review, in living cells have been achieved. In particular, the recent success of SFDI of individual proteins tagged with green fluorescent protein (GFP) in live cells has opened new important possibilities for studying events occurring in living cells at the level of single molecules. Specifically, SFDI of GFP allows the tracking of movement and oligomerization levels of individual oligomers (monomers) in living cells and, thus, provides powerful means to investigate the movement, assembly, localization, and activation that signaling molecules undergo following an external stimulus. In this short account, we first review technologically important points for SFDI of GFP molecules in living cells, then give examples of its application, and, finally, propose a synergistic use of SFDI and single-particle tracking, a technique used for investigating single or small groups of molecules in live cells over the past 15 years.     

Synthesis of fluorene‐based high performance polymers. I. Poly(arylene thioether)s with excellent solubility and high refractive index

Several poly(arylene thioether)s ( PTEs ) containing a fluorene moiety were synthesized by the polycondensation of masked dithiols such as 9,9‐bis(4‐(N,N‐dimethyl‐S‐carbamoyl)phenyl)fluorene and various difluoroarenes. All PTEs were obtained in quantitative yields. The PTEs showed good thermal stability: the 10% weight loss temperature was over 480 °C under both nitrogen and air atmosphere by TGA, and glass temperature was within a range of 204–275 °C by DSC. Most PTEs exhibited remarkably high refractive index values in a range of 1.66–1.72 at 589 nm, whereas they had a very low degree of birefringence properties. Furthermore, the PTEs showed high solubility in ordinary organic solvents such as chloroform, N‐methylpyrrolidone, and tetrahydrofuran. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3073–3082, 2007     

N-策略GI／G／1排队系统瞬时队长分布

探讨了一个具有如下特征的排队系统,顾客到达的时间间隔和服务时间独立同分布,系统进入空闲之后,服务员开始休假,直到累积Ⅳ个顾客之后,才进入一个新的忙期．此系统是经典GI／G/1排队系统的拓广,利用补充变量法,可以得到一马尔可夫骨架过程,借助于马尔可夫骨架过程理论,该系统瞬时队长分布的积分表示被导出．