Study of salt permeation process into Vigna angularis using Ag/AgCl electrodes

In this work we report a novel method that can monitor in vivo the salt permeation process into a plant Vigna angularis using two Ag/AgCl electrodes. The method is based on the electromotive force (emf) measurement using two Ag/AgCl electrodes, one inserted into the V. angularis pith cavity and the other placed into saline ([NaCl]=1 M) surrounding the roots. Temporary change of emf ranging from 0 to ca. 0.115 V was measured in vivo using the system, and the possible physiological phenomenon during the period was discussed.     

Incorporating tritiated water into a 14C-sampling system for quantitative estimation of 14C activity in airborne effluent

The effects of incorporating tritiated water into a ¹⁴C-sampling system in sample preparation and ¹⁴C activity measurement by liquid scintillation counting were investigated. Experiments derived the limit of water content in the prepared sample, and also demonstrated that ¹⁴C activity can be determined without any interference from ³H contamination for a clear-sample solution. The results enabled us to estimate the permissible relative humidity of air required for accomplishing sample preparation and ¹⁴C activity measurement. These showed that for sampling of air with less than the permissible relative humidity, total ¹⁴C activity in airborne effluent can be evaluated accurately without dehumidification of air.The authors would like to thank T. Kozawa, K. Isaka and Y. Adachi of Inspection Development Company Ltd., Y. Hiyama of Zuihou Sangyou Company Ltd., and T. Mizutani, H. Watanabe, M. Takeishi and K. Shinohara of Japan Nuclear Cycle Development Institute for their valuable assistance.     

Kinetics of γ-ray polymerization of formaldehyde in the presence of carbon dioxide

A kinetic study of the γ-ray polymerization of formaldehyde in toluene solution in the presence of carbon dioxide was carried out at temperatures of + 13 to ?17°C. Two modes of the polymerization, spontaneous and γ-ray polymerization, occur in this system. The γ-ray polymerization, experimentally separated from the spontaneous polymerization, was investigated. The rate of γ-ray polymerization increased slightly with the square root of carbon dioxide concentration. The rate of polymerization was also found to be proportional to the dose rate and the square of monomer concentration. The molecular weight of polymer formed was independent of the reaction condition. The apparent activation energy was estimated to be 10.3 kcal./mole. The kinetics of the γ-ray polymerization in the presence of carbon dioxide are explained quantitatively by a cationic mechanism, and the role of carbon dioxide is as an action of retardation for neutralization of the cationic initiating species, which was produced by γ-radiation, by means of a reverse reaction with an electron. Physical and mechanical properties of the polymer obtained by γ-ray polymerization were also investigated.     

Cationic polymerization of formaldehyde in liquid carbon dioxide. Part I

A cationic polymerization of formaldehyde which gave a high molecular weight polymer was studied in liquid carbon dioxide at 20–50°C. In the polymerization without any catalyst both the rate of polymerization and the molecular weight of the resulting polymer increased rapidly with a decrease in the loading density of the monomer solution to the reaction vessel, and also increased with an increase in the initial monomer concentration. From these results it was concluded that the initiating species could be ascribed to an impurity contained in the monomer solution. Both the rate of polymerization and the degree of polymerization of the polymer also increased with rising temperature. The carboxylic acid added acted as a catalyst in the polymerization because of increase in the polymer yield, the molecular weight of polymer formed, and the number of moles of polymer chain with increasing dissociation constant of acid used. It was concluded that the polymerization in liquid carbon dioxide proceeded by a cationic mechanism. Methyl formate had no influence on the polymerization, but methanol and water acted as a chain-transfer agent.     

Preparation of novel,high‐modulus,swollen‐ or jungle‐gym‐type polyimide gels end‐crosslinked with 1,3,5‐tris(4‐aminophenyl)benzene

A novel preparation approach for high‐performance polyimide gels that are swollen or have a jungle‐gym‐type structure is proposed. A new rigid and symmetric trifunctional amine, 1,3,5‐tris(4‐aminophenyl)benzene (TAPB), was synthesized as a crosslinker. Three different kinds of amic acid oligomers derived from pyromellitic dianhydride (PMDA), 4,4′‐oxydiphthalic anhydride (ODPA), p‐phenylenediamine (PDA), and 4,4′‐oxydianiline (ODA) were end‐crosslinked with TAPB at a high temperature to make polyimide networks with different structures. Transparent polyimide gels were obtained from the ODPA–ODA/TAPB series with high compression moduli of about 1 MPa at their equilibrium swollen states in N‐methylpyrrolidone. Microscopic phase separation occurred during the gelation–imidization process when polyimide networks were generated from PMDA–PDA/TAPB and PMDA–ODA/TAPB. After these opaque polyimide networks were dried, a jungle‐gym‐like structure was obtained for the PMDA–PDA/TAPB and PMDA–ODA/TAPB series; that is, there was a high void content inside the networks (up to 70%) and little volume shrinkage. These polyimide networks did not expand but absorbed the solvent and showed moduli as high as those of solids. Therefore, using the highly rigid crosslinker TAPB combined with the flexible monomers ODPA and ODA and the rigid monomers PMDA and PDA, we prepared swollen, high‐performance polyimide gels and jungle‐gym‐type polyimide networks, respectively. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2501–2512, 2002     

Optical coupling characteristics of graded-index type photonic crystal fiber collimator depending on air hole diameter ratio to pitch

Optical Review - A graded-index type photonic crystal fiber (GI-PCF) has a graded effective index distribution that can be realized by an α-power air hole diameter distribution in radial...     

Phylogenetic analysis and homology modelling of <Emphasis Type="Italic">Paracentrotus lividus</Emphasis> nectin

The extracellular matrix protein Pl-nectin, a 210-kDa homodimer originally purified from sea urchin eggs, plays a crucial role in cell adhesion and embryonic morphogenesis. The compiled cDNA sequence, obtained by RT-PCR primer walking and 3′ RACE, identified a 984aa product containing a 23aa signal peptide and including all six internal peptides identified by protein microsequencing. The protein is a new member of the galactose-binding protein superfamily as it consists of six 151–156aa-long tandemly repeated domains (D1–D6), homologous to the discoidin-like domains, also known as F5/8-type C domains. Based on homology modelling, we present a three-dimensional structure (3D) for D5, identified as the prototype domain. The molecular modelling of the assembled Pl-nectin homodimer accounts for a Pl-nectin quaternary structure composed of two 105-kDa C-shaped monomers linked by a S–S bridge. The presence of an LDT motif between the first and the second exposed loops of the D2 domain suggests the binding of Pl-nectin to an integrin receptor. Altogether, the in silico analysis described here is consistent with previous biochemical reports and offers a basis for predictions to be experimentally tested.