Synthesis and characterization of poly(ethylene aspartate)-metal complexes

Poly(ethylene aspartate) [PEA] was synthesized by the melt condensation of D,L-aspartic acid and ethylene glycol. PEA containing pendent amino and carbonyl groups in its repeating chain was used as the polymeric ligand for complexation with transition metal ions, viz. Co(II), Ni(II), Cu(II), Mn(II), Zn(II), Cd(II), Ca(II), Mg(II), Pb(II) and Hg(II). Complexation was found to be most effective in DMSO. The resulting polyester-metal complexes were solid coloured materials which have been characterized by IR spectroscopy, elemental analysis and magnetic susceptibility measurements. The thermal stability of the polyester-metal complexes was investigated by thermogravimetric analysis (TGA). On the basis of the physico-chemical studies, an oxygen and nitrogen coordinated structure for the polyester-metal complexes is proposed.     

Investigations of surface characterization of silicone rubber due to tracking phenomena under a.c. and d.c. voltages

In the present work, tracking phenomena has been studied with silicone rubber material under the a.c. and d.c. voltages following IEC-587 standards. The surface condition of the tracked zone was analysed using wide angle X-ray diffraction (WAXD) and thermogravimetric differential thermal analysis (TG-DTA) studies. The tracking time was different for a.c. and d.c. voltages.     

Accommodation of a D-Phe residue into a right-handed 3(10)-helix: structure of Boc-D-Phe-(Aib)4-Gly-L-Leu-(Aib)2-OMe, an analogue of the amino terminal segment of antiamoebins and emerimicins

Recently an unstable trinucleotide CTG repeat, located within the 3' untranslated region of a gene on 19q13.3 was discovered in kindreds with myotonic dystrophy (DM). The age-of-onset/severity of DM shows a good correlation with CTG repeat size, and pedigrees and data reported to date have shown a striking trend toward amplification of the size of the CTG repeat during transmission from parent to child. The amplification has been accepted as the biological explanation for anticipation in the clinical severity observed in many families with DM. In this paper we report on 3 families where CTG amplification decreased during transmission from parent to child. In one case there was a gene conversion event, while in the remaining 2 there was a simpler reduction in the size of the repeat length. The changes appear to have been accompanied by a reduction in clinical severity in the child when compared to the parent. These observations are discussed in terms of their clinical implications and the biases that may exist in much of the reported data.     

One-step oxidation of cyclohexane to adipic acid

Liquid-phase oxidation of cyclohexane with Co(III) catalyst and gaseous oxygen was found to be influenced by reaction temperature, catalyst concentration and the duration. Maximum adipic acid product selectivity (77%) with about 85% cyclohexane conversion was attained at 100°C using catalyst: cyclohexane molar ratio 0·08. Under these conditions more than 80% cyclohexane was converted in the first hour, although selectivity to adipic acid continued to increase for the next 5 h. Cyclohexyl acetate and cyclohexyl monoadipate were identified as important intermediates. This study supports the mechanism proposed by Schultz, J. G. D. and Opchenko, A., J. Org. Chem., 38 (21) (1973) 3729.     

Transport properties in a mixed inorganic ion exchanger—zirconium phosphomolybdate—in comparison to its single salt counterparts

Amorphous inorganic ion exchangers zirconium phosphate, zirconium molybdate and zirconium phosphomolybdate have been prepared and characterized by elemental analysis, TGA, FTIR and surface area measurements. The protonic conductivity in these materials were determined at various temperatures and compared. It was found that the mixed material zirconium phosphomolybdate showed maximum conductivity at all temperatures.     

Countercurrent water-heating system with a heat exchanger in a solar energy collector loop

The counter current heat exchanger theory with periodic inlet temperatures has been applied to analyze the thermal performance of a water heating system. The theoretical results obtained are in agreement with the experimental data reported in the literature.