Chirality induction of polyaniline derivatives through chiral complexation

Chirality induction of π-conjugated polyaniline derivatives was achieved by chiral complexation with chiral palladium(II) complexes. The crystal structure of the chiral conjugated complex with a model compound of the polyaniline, N,N-bis(4^′-dimethylaminophenyl)-1,4-benzoquinonediimine, revealed a chiral propeller twist conformation of the π-conjugated moiety.     

Kinetic asymmetric protonation as a stereochemistry determining step in theMichael addition of acetic acid derivatives to α-substituted cinnamic acid derivatives

Summary The reaction between acetic acid derivatives and -substituted cinnamic acid derivatives has been studied inTHF andTHF:HMPT (80:20) as an alternative pathway of theMichael addition of phenylacetic and cinnamic acid derivatives. The regioselectivity observed is found to depend on the acceptor functional group and its geometry but not on the solvent used. The diastereoselectivity of the conjugate addition results from kinetic protonation of diastereotopic enolates (1,2-asymmetric induction). It varies from low in the presence ofHMPT to considerable or even high in pureTHF. The favouredanti orsyn configuration inTHF depends on the nature of the enolate. The results obtained are rationalized in terms of protonationvia transition structures different in type (openvs. chelated) and geometry.

---

Kinetische asymmetrische Protonierung als bestimmender Schritt für die Stereochemie bei derMichael-Addition von Essigsäurederivaten an -substitutierte Zimtsäurederivate

Zusammenfassung Die Reaktion zwischen Essigsäurederivaten und -substitutierten Zimtsäurederivaten wurde inTHF undTHF:HMPT=80:20 als ein alternative Weg derMichael-Addition von Phenylessigsäure und Zimtsäurederivaten untersucht. Es wurde gefunden, daß die beobachtete Stereoselektivität von der Akzeptorgruppe und ihrer Geometrie, nicht jedoch vom Lösungsmittel abhängig ist. Die Diastereoselektivität der konjugierten Addition folgt aus der kinetischen Protonierung der diastereotopen Enolate (1,2-asymmetrische Induktion). Sie variiert von klein (bei Anwesenheit vonHMPT) bis bedeutend oder sogar groß (in reinemTHF). Die bevorzugteanti odersyn Konfiguration inTHF hängt von der Natur der Enolate ab. Die Ergebnisse werden durch eine Protonierungvia bezüglich Typ (offen oder chelatiert) und Geometrie unterschiedliche Strukturen des Übergangszustands erklärt.

     

An optimal sequence in multicharacteristics inspection

Given a component withN critical characteristics, each characteristici has a cost of inspectionC _i>0 and a probability of rejectionR _i, 0R _i<1. an=" optimal=" sequence=" for=" ordering=" these=" critical=" characteristics=" for=" inspection=" is=" found.=" this=" sequence=" minimizes=" the=" total=" expected=" cost=" of=" inspection.=" the=" implications=" and=" the=" applications=" of=" this=" sequence=" are=">Communicated by M. D. Intriligator     

Accelerated nucleation of tetrahydrofuran(THF)hydrate in presence of ZIF-61

Clathrate hydrate can be used in energy gas storage and transportation,CO 2 capture and cool storage etc.However,these technologies are difficult to be used due to the low formation rate and long induction time of hydrate formation.In this paper,ZIF-61(zeolite imidazolate framework,ZIF) was first used in hydrate formation to stimulate hydrate nucleation.As an additive of clathrate hydrate,ZIF-61 promoted obviously the acceleration of tetrahydrofuran(THF) hydrate nucleation.It shortened the induction time of THF hydrate formation from 2-5 h to 0.3-1 h mainly due to the template function of ZIF-61 by which the nucleation of THF hydrate has been promoted.     

Asymmetric induction by helical poly(amino acid)s in cyanosilylation of aldehydes

It was first demonstrated that helical poly(amino acid)s have an ability to induce enantioselectivity in the cyanosilylation of aldehydes. The helicity of poly(amino acid)s and the N-terminal amino group were essential for the enantioinduction of the reaction.     

高速弹丸的磁感应测速方法

 由固定磁体感应弹速测试技术与数字化波形存储器、微机相结合组成的速度测量自动化系统，已在23 mm口径二级轻气炮上应用成功。采用压缩磁场结构设计和严格的信号计时处理方法，使1~7.5 km/s范围的时间判读精度达到0.03%，整套系统的速度测量误差约0.1%，给二级轻气炮这类动高压设备提供了一种精确可靠的速度测试手段。     

3 MV感应电压叠加器的磁感应腔研制

 根据脉冲驱动源和负载参数,提出了3 MV感应电压叠加器磁感应腔的设计指标为1.2 MV/70 ns。由感应腔的电流传输效率和真空同轴线绝缘要求,确定了磁芯的几何尺寸;研制了矩形比为0.5的预退火非晶磁环,明确磁环数量不少于6只;在30 T/s时,实验测量的最大脉冲相对磁导率与饱和波模型计算结果相当;估算磁感应腔的等效激磁电感约为7.3 μH,涡流损耗电阻约为139 Ω。根据临界击穿场强的经验公式,采用电场数值分析方法,确定了磁感应腔的电气结构;实验验证了磁感应腔设计有效性;建立了基于磁感应腔的3 MV感应电压叠加器全电路模型,阳极杆箍缩二极管电压、电流计算波形,与实验结果基本相符。     

采用Si薄膜的光子计数成像系统性能的研究

在陶瓷基底上利用电子束蒸镀方法制备了Si薄膜,用作感应读出方式光子计数成像系统的电荷感应层,并研究了薄膜的结构特征和表面形态.X射线衍射(XRD)测试和场发射扫描电子显微镜(FESEM)图像表明,沉积的Si薄膜为无定形态,由于陶瓷晶界的存在,薄膜较粗糙.搭建了相应的实验系统,对比了采用不同厚度Si薄膜时系统的空间分辨率、计数率、脉冲高度分布曲线等,发现薄膜的厚度对探测器的计数率影响较大.此外,实验还对比了采用相同电阻值的Si薄膜和常用的Ge薄膜时系统的性能.研究表明,采用Si薄膜时系统的畸变较小、计数率高     

基于Rb原子电磁诱导透明的量子干涉实验研究

报道了基于85RbD2线电磁诱导透明(EIT)的量子干涉现象,发现当一耦合光和探测光之间满足拉曼共振条件时出现电磁诱导透明现象,在某些条件下也观察到电磁诱导吸收(EIA).而当用一束耦合光和一束泵浦光共同作用于5S1/2,F=3→5P3/2,F′=3和5S1/2,F=3→5P3/2,F′=4能级上时,探测光的吸收谱表现出三峰结构,并且峰强弱与两耦合光之间的相对强度有关.