220-MHz NMR spectra of acrylic monomer–2-substituted 1,3-diolefin alternating copolymers

An investigation by 220-MHz NMR spectroscopy was carried out on the alternating copolymers of acrylic monomer with 2-substituted 1,3-diolefin. The chain structures were determined. The acrylic monomers used were methyl methacrylate (MMA), acrylonitrile (AN), and methacrylonitrile (MAN); isoprene (IP) and chloroprene (CLP) were the 1,3-diolefins. In the MAN–IP alternating copolymer, the 1-position methylene protons of IP showed an AB quartet peak, confirming the α-1 linkage structure. Similarly, in the MMA–CLP and AN–CLP copolymers, the 1-position methylene protons of CLP showed and AB quartet and an ABX pattern, respectively, confirming the α-1 linkage structure in both these cases also. The α-1 linkage structure was also revealed by the decoupling technique in the MAN–CLP alternating copolymer. The AN–IP and MMA–IP alternating copolymers also possess a bond between the α-position of the acrylic monomer and the 1-position of IP. The monomeric units in the alternating copolymers of acrylic monomers with 2-substituted 1,3-diolefins were generally linked at the α-position of acrylic monomer and the 1-position of 1,3-diolefin. On the other hand, in the Diels-Alder adducts of acrylic monomer with 2-substituted 1,3-diolefin, the reaction takes place between the α-position of acrylic monomer and the 4-position of 1,3-diolefin. The regioselectivity of the alternating copolymers and the Diels-Alder adducts is quite compatible with the expectations from molecular orbital theory.     

Preparation and Characterization of a Sol-Gel Prepared Ferroelectric Sandwich Structure

A novel silicon-based PbTiO₃/Pb(Zr,Ti)O₃/PbTiO₃ (PT/PZT/PT) sandwich structure has been prepared using a sol-gel method. The annealing temperature is greatly reduced compared with those structures without PT layers. Capacitance-voltage (C-V), leakage current-voltage (I-V), polarization-field (P-E), dielectric-frequency response and polarization fatigue of the sandwich structure are examined. The relative dielectric constant, the coercive field and the remanent polarization of the PZT films are measured to be about 900, 18 kV/cm and 16 C/cm² respectively. The current density is less than 5 × 10^–9 A/cm² below 200 kV/cm. The dielectric constant of the structure remains constant at low frequency, and decreases to some degree at high frequency. The retained polarization does not change significantly after 8 × 10⁹ read/write cycles. The PZT films are proved to have very good dielectric and ferroelectric properties. The new PT/PZT/PT sandwich structure can be valuable for memory devices and other applications.     

Analytical use of a biochemical luminous membrane

Luminous membranes were prepared by immobilizing peroxidase (POD) to collagen matrix. The POD luminous membrane generated luninescence in the presence of luminol and H₂O₂, and the peroxide was determined in the concentration range 10-⁶-10-³ M by following luminescence emitted from the membrane. Glucose was determined using a luminous membrane in which POD and glucose oxidase (GOD) were coimmobilized. The luminous membranes appear to be feasible for the determination of enzyme substrates and enzyme activity.     

Pharmacokinetics of caffeine and its metabolites in horses after intravenous, intramuscular or oral administration.

The pharmacokinetics of caffeine (CAF) and its metabolites, dimethylxanthines, were examined in horses administered 2.5 mg/kg of CAF intravenously (i.v.), intramusculary (i.m.), or orally (p.o.). The plasma samples were extracted by Extrelut and the concentrations of CAF and metabolites were determined by high performance liquid chromatography (HPLC) with a short column. The pharmacokinetics of CAF after bolus i.v. injection were described by the assumption of a two-compartment model, and those of CAF after i.m. or p.o. administration were done by the assumption of a one-compartment model. The biologic half lives of CAF were 15.5, 18.6, and 16.4 h after administering i.v., i.m. and p.o., respectively. The extent of the bioavailability of the p.o. administration was determined as 1.04 times the dose. The differences in pharmacokinetic parameters were not statistically significant among administration routes. A straight correlation existed between the logarithms of body weights of different species of animals and those of their biologic half lives of CAF. Therefore, the biologic half life of CAF in an animal might be predictable as a function of its body weight.     

Inverse relaxation-model and relation to recovery internal friction

Inverse relaxation is studied for hard elastic polypropylene (HEPP), rubber and non-elastic polypropylene. The results show that contractive stress, stress, and internal friction are three essential factors related to the phenomenon. A three-element model in which each element has a definite meaning is proposed to describe this phenomenon. The results also show that, in the first cyclic deformation, relaxation time increases with the increase of recovery for all the materials, which indicates that recovery viscosity increases with the increase of recovery, but the stress rising amplitude (SRA) of inverse relaxation has a maximum in the recovery range. Analysis indicates that SRA equals recovery internal friction (RIF) for ideal material in which stress is solely a function of strain, independent of paths, and approximately equals RIF for non-ideal material at a given strain. From this principle it is found that the order of the work counteracted by RIF for the four materials is the same as that of their second hysteresis loop, and the RIF of HEPP has a sudden increase at the later recovery range.     

Dual-mode electrochromism switched by proton transfer: dynamic redox properties of bis(diarylmethylenium)-type dyes

Upon oxidative dimerization of pale yellow Ar2C=CHPh 1 (Ar = 4-Me2NC6H4), deep blue 1,4-dication 2(2+) was obtained as a stable salt, which was transformed into 1 by reductive C-C bond fission; deprotonation of 2(2+) gave intense yellow diene 3, which was interconvertible with violet dication 4(2+) by two-electron transfer, thus exhibiting two distinct modes of electrochromism before and after proton transfer.     

合成云母蒙脱石及其交联物在乙醇氨化反应中的催化行为

用水热法合成了云母蒙脱石,并与羟基铝齐聚物交联,DTA和IR结果表明,由于柱的引进,高温焙烧时层内八面体上羟基脱除变得较为容易。由NH_3-TPD和吡啶吸附测得的表面酸性表明Al-CLS具有较SMM更多的弱酸和强酸中心。催化剂上弱酸中心有利于醇的脱水,而吸附在强酸中心上的NH_3有利于醇的胺化。     

The yields of photonuclear reactions for multielement photon-activation analysis

A comprehensive study on the yields of photonuclear reactions of various types has been performed, and sensitivities and the effects of interferences in multielement photon-activation analysis have been evaluated by bremsstrahlung activation of many elements with maximum energies ranging from 30 to 60 MeV. The applicability and reliability of the method were demonstrated by analyzing standard round-robin samples and then by presenting the elemental abundances in several geological, biological and environmental materials. The method was almost insensitive to matrix effects and was assessed to be promising for nondestructive multielement determination of the materials of wide variety, giving good reproducible results for 20 or more elements.     

Perfluoro-1,3,5-tris(p-oligophenyl)benzenes: Amorphous Electron-Transport Materials with High-Glass-Transition Temperature and High Electron Mobility

Perfluoro-1,3,5-tris(p-quaterphenyl)benzene (PF-13Y) and perfluoro-1,3,5-tris(p-quinquephenyl)benzene (PF-16Y) have been synthesized and characterized. They showed higher glass transition temperatures compared with perfluoro-1,3,5-tris(p-terphenyl)benzene (PF-10Y). Organic light-emitting diodes were fabricated using these materials as the electron-transport layers. PF-13Y and -16Y are better electron transporters than PF-10Y. The electron mobilities of PF-10Y and Alq₃ were measured by the time-of-flight technique. PF-10Y showed higher electron mobilities (10⁻⁴ cm²/V s) and weaker electric field dependence compared with Alq₃.     

Photoelectron kinetic energy dependence in near threshold ionization of NO from A state studied by time-resolved photoelectron imaging

Photoelectron angular distributions in the laboratory frame (LF-PADs) from the A((2)sigma(+)) state of NO molecule were measured by femtosecond time-resolved photoelectron imaging with (1 + 1(')) resonance enhanced multiphoton ionization via the A state. High-precision measurements of the anisotropy parameters of LF-PADs were performed for the photoelectron kinetic energy from 0.03 to 1.05 eV as a function of the pump-probe delay time. The revival feature of the rotational wave packet on the A state was clearly observed in the time dependence of the photoelectron anisotropy parameters. By approximating the phase shifts of the photoelectron partial waves by the quantum defects in the high-lying Rydberg states using the multichannel quantum defect theory, the energy-dependent photoionization transition dipole moments were determined, for the first time, from time-dependent LF-PADs measured by time-resolved photoelectron spectroscopy.