Shear-induced spiral-like morphology of a main-chain liquid crystalline poly(aryl ether ketone)

The shear-induced spiral-like morphology of a main-chain thermotropic liquid crystalline poly(aryl ether ketone) is observed and characterized by means of polarizing light microscopy, atomic force microscopy, transmission electron microscopy and electron diffraction techniques. The spiral-like texture is formed during shearing in the temperature range of liquid crystalline to isotropic transition (335-340 degreesC), and dispersed discontinuously in the mosaic matrix. Electron diffraction results indicate that the spiral exhibits orthorhombic lateral packing of the crystals and homeotropic alignment of the molecules. The spiral formation process and possible affecting factors are discussed.

Effect of cross-linking of high-density polyethylene. I. On spherulitic structures

Crystallization behavior and spherulitic structure of linear high-density polyethylene (HDPE), after being irradiated in its molten state by gamma -rays, was investigated by small-angle laser scattering (SALS) and differential scanning calorimetry (DSC). Significant changes in the crystallization of HDPE during cooling in air before and after being irradiated in the melt were observed. A critical minimum average molar mass between cross-links (200 carbon-carbon bonds) for spherulite formation in such an irradiated HDPE network was obtained.

Synchronous fluorescence spectra of myoglobin

The synchronous fluorescence spectra of myoglobin were studies for the first time. The fluorescence peals observed in the spectra were assigned, When the wavelength interval (Delta lambda) is 80 nm, the main peak at 335 nm is originated from the tryptophan residues in the myoglobin molecule. When Delta lambda is 20 nn, the peak at 308 nm is mainly due to the tyrosine residues in the myoglobin molecule and in a small part due to the tryptophan residues. Two peaks at 322 and 596 nm were observed in the spectrum of myoglobin for Delta lambda = 40 nm. The peak at 322 nm is due to both tyrosine and tryptophan residues. The peak at 596 nm is attributed to the heme group in the myoglobin molecule.

Study of energy transfer in KMgF3 : Eu-X (X = Gd, Cr, Ce) by the decay model of P-6(7/2) exited state of Eu2+

Energy transfer processes between Eu2+ and Gd3+, Cr3+, Ce3+ ions in KMgF3, which are difficult to study spectroscopically, have been investigated by using the proposed four-level decay model of the P-6(7/2) excited state of the Eu2+ ion. Gd3+ and Ce3+ transfer its energy to the vibronic transition of the P-6(7/2) --> S-8(7/2) transition of Eu2+, whereas Cr3+ receive energy from Eu2+ via the d-d interaction. The energy transfer from the Eu2+ 4f(6)5d level to the Ce3+ 4f5d state is observed spectroscopically, and the energy transfer mechanism is discussed. (C) 2001 Elsevier Science B.V. All rights reserved.

Effects of La3+ and Gd3+ on Ca2+ influx in rat hepatoma H-35 cells

Effects of La3+ and Gd3+ on Ca2+ influx were investigated in rat hepatoma H-35 cells by measuring the initial rate of Ca-45(2+) uptake. It was found that the maximum initial rate of Ca2+ uptake was increased six- to ten-fold at low concentrations of La3+ and Gd3+. Kinetic analyses by measuring the initial rate of Ca2+ influx at different external Ca2+ concentrations indicated the existence of two intracellular exchangeable components in the basal Ca2+ system, with low and high affinities for Ca2+, and only one class of Ca2+ binding sites was observed in the La3+- or Gd3+-treated cells. For high affinity, La3+ and Gc(3+) increased both kinetic parameters K-m and V-max of basal Ca2+ influx. La3+ and Gd3+ compete directly with Ca2+ for Ca2+ binding site for low affinity. The kinetics is competitive.

NMR titration and molecular model MOPAC calculation of protonation processes of two MRI ligands

The protonation process of two DTPA bis(amide) derivatives, DTPA-BDMA and DTPA-BDEA, was studied by using H-1 NMR titration and MOPAC calculation. Their protonation process was proposed in the order of the central amine, the terminal amines, the central carboxyl, the terminal carboxyl, the other terminal carboxyl and central amine. During the protonation of the terminal amine, there existed a large fraction of proton transfer from the central amine to the other terminal amine.

2,5-双(4-羟基苯亚甲基)环戊酮中双电荷离子存在的串联质谱证据

应用串联质谱的碰撞诱导解离和联动扫描技术，研究了2,5-双(4-羟基苯亚甲基)环戊酮的质谱解离特征，提供了双电荷离子存在的实验证据。进一步对双电荷离子(m/z146)的碰撞诱导解离碎裂进行了讨论。

Luminescence properties of sol-gel derived silica gels doped and undoped with RE-complexes (RE=Eu, Tb)

The luminescence properties of silica gels and silica gels doped with two rare earth complexes, Eu(TTA)(3) and Tb(o-CBA)(3) (TTA=thenoyltriffuocetate, o-CBA=o-chlorobenzoic acid) are reported and discussed. Pure silica gels show a blue luminescence, and the maximum excitation and emission wavelengths depend strongly on the solvents used. Both of the studied rare earth complexes exhibit the characteristic emissions of the rare earth ions in silica gels, i.e., Eu3+5D0-->F-7(J)(J=0,1,2,3,4), Tb3+5D4-->F-7(J)(J=3,4,5,6) transitions. Compared with the pure RE-complexes powder, the silica gels doped with RE-complexes show fewer emission lines of the rare earth ions. Furthermore the rare earth ion (Tb3+) presents a longer lifetime (1346 mu s) in silica gel doped with Tb(o-CBA)3 than in pure Tb((o-CBA)(3) powder (744 mu s). The reasons responsible for these results are discussed in the context.

RADIATION CROSS-LINKING OF POLYTETRAFLUOROETHYLENE

Polytetrafluoroethylene (PTFE) is considered to be a typical radiation degradative polymer. In this work the polymer was crosslinked by means of radiation at 335 +/- 5-degrees-C under vacuum. Crosslinked PTFE showed a great improvement in high temperature

温度和压力对六氟二酐型聚酰亚胺的透气性能的影响

本文研究了温度和压力对五种六氟二酐（６ＦＤＡ）型聚酰亚胺膜对Ｈ_２、ＣＯ_２、Ｏ_２、Ｎ_２和ＣＨ_４五种气体透过性能的影响．在３０－１００℃区间，五种聚酰亚胺的透气系数与温度的关系均符合Ａｒｒｈｅｎｉｕｓ关系式；在０．３－１．２ＭＰａ区间，压力对透气系数的影响很小．６ＦＤＡ－４，４＇－二氨基二苯酮（ＤＡＢＰ）和６ＦＤＡ－３，３＇－二甲基二苯甲烷二胺（ＤＭＭＤＡ）在１００℃仍然具有较大的透气选择系数，是比较好的气体分离膜材料．

水溶液中稀土离子与甘氨酸、丝氨酸、天冬氨酸作用的~(13)C NMR研究

测定了酸性水溶液中甘氨酸、丝氨酸和天冬氨酸稀土络合物(Ln=La、Pr、Nd、Eu、Tb、Dy、Ho、Er、Tm和Yb)的~(13)C诱导位移。对位移试剂的分析指出,三种氨基酸通过α-羧基以双齿形式配位于稀土,配位键长为0.23nm～0.25nm,天冬氨酸的y-羧基也是配位基团。由本文与文献中已报道的各种氨基酸稀土络合物的~(13)C诱导位移的系统分析表明,配体~(13)C超精细偶合常数A值和结构因子G值有如下规律:(1)│A(C_0)│<│A(C_α)│;A(C_0)为正,A(C_α)为负;(2)│G(C_0)│>│G(C_α)│;配体碳核的G均为负值。

DETERMINATION OF THE RATE-CONSTANT OF A CATALYTIC REACTION USING A PARALLEL INCIDENT SPECTROELECTROCHEMICAL CELL

The possibility of determining the rate constant of a catalytic reaction using a parallel incident spectroelectrochemical cell was investigated in this work. Various spectroelectrochemical techniques were examined, including single-potential-step chronoabsorptometry, single-potential-step open-circuit relaxation chronoabsorptometry and double-potential-step chronoabsorptometry. The values determined for the kinetics of the ferrocyanide-ascorbic acid system are in agreement with the reported values. The parallel incident method is much more sensitive than the normal transmission method and can be applied to systems which have smaller molar absorptivities, larger rate constants or lower concentrations.

SYNTHESES OF METHYLCYCLOPENTADIENYL DERIVATIVES OF LANTHANIDES (LN = LA-ND) AND CRYSTAL-STRUCTURES OF [(THF)2LI(MU-CL)2]2[MECPND(THF)] AND [LI(DME)3][MECPLA(NPH2)3]

The reaction of LnCl3.2LiCl with 1 equiv of MeCpNa in THF gives the complexes [(THF)2Li(mu-Cl)2]2[MeCpLn(THF)] (Ln = Nd (1), La (2)) in good yield. These precursors react further with 2 equiv of LiNPh2 to produce the new complexes [Li(DME)3][MeCpLn(NPh2)3] (Ln = La (3), Pr (4), Nd (5)). They have been characterized by elemental analyses and IR and NMR spectra, as well as by structural analyses of 1 and 3. The chloride 1 crystallizes in the monoclinic space group P2(1)/n (No. 14) with a = 12.130 (5) angstrom, b = 17.343 (5) angstrom, c = 17.016 (5) angstrom, beta = 108.54 (3)-degrees, V = 3393.87 angstrom3, Z = 4, and D(c) = 1.45 g/cm3. Least-squares refinement led to a final R value of 0.051 (I greater-than-or-equal-to 3-sigma(I(o))) for 2004 independent reflections. Complex 3 crystallizes in the monoclinic space group P2(1)/c (No. 14) with a = 18.335 (6) angstrom, b = 16.576 (5) angstrom, c = 17.461 (6) angstrom, beta = 96.04 (3)-degrees, V = 5277.17 angstrom3, D(c) = 1.26 g/cm3, Z = 4, and R = 0.057 (I greater-than-or-equal-to 2.5-sigma(I(o))) for 3378 reflections. The structure of 3 consists of discrete ion pairs [Li(DME)3]+ and [MeCpLa(NPh2)3]- with average La-N and La-C(ring) distances of 2.459 (8) and 2.84 (1) angstrom, respectively.

大豆食心虫性信息素的化学结构触角电位及田间诱蛾效果

用气相色谱(GC)和气相色谱-质谱(GC-MS)分析,证明反-8,反-10-十二碳二烯醇醋酸(B)是大豆食心虫[Leguminivora glycinivorella(Mats.)]性信息素的组分。通过触角电位(EAG)测试,发现反-10-十二碳烯醇醋酸酯(A)、B 和反-7,顺-9-十二碳二烯醇醋酸酯(C)对该虫雄蛾触角有强烈刺激作用。大量田间诱蛾试验表明,由 A 和 B 两化合物组成的性引诱剂,对该虫雄蛾有很高的引诱活性。其中 A 和 B 按5∶2混合,剂量50μg/诱捕盆,单盆每日最多诱捕雄蛾达776头,诱捕雄蛾总数是1头活雌蛾的16.8倍。顺-10-十二碳烯醇醋酸酯(D)和反-10-十四碳烯醇醋酸酯(E)降低 AB 的引诱活性,甘油作为缓释剂,能延长诱芯的有效期,即诱蛾活性。上述结果表明,我国大豆食心虫性信息素不同于日本大豆食心虫性信息素。小面积防治应用试验效果明显。