The infra-red absorption spectrum of diamond

Proceedings - Mathematical Sciences - The absorption spectra of four typical diamonds, three of them luminescent and the fourth non-luminescent, have been investigated in the infra-red in the...     

Rigidity of minimal surfaces inS 3

Isometric deformations of compact minimal surfaces in the standard three-sphere are studied. It is shown that a given surface admits only finitely many noncongruent minimal immersions intoS ³ with the same first fundamental form.     

Immobilization and Characterization of Lactate Dehydrogenase on TEOS Derived Sol-Gel Films

Physical adsorption and physical entrapment techniques have been utilized for the immobilization of lactate dehydrogenase (LDH) on tetraethylorthosilicate (TEOS) derived sol-gel films. The enzyme (LDH) activity has been assayed as a function of time, temperature, pH and pyruvate concentration. The results of photometric measurements used for monitoring the reaction yield a response time of about 1 min, linearity over a concentration range of 0–1.5 × 10^-3 M and detection limit of 5 × 10^-5 M. The TEOS sol-gel films containing LDH have been found to be stable for about 30 days at temperatures 4 to 10°C.     

Protection of plasmid pBR322 DNA by flavonoids against single-strand breaks induced by singlet molecular oxygen

Flavonoids, the dominant colouring pigments of plants, as well as the related polyphenol tannic acid significantly inhibit single-strand breaks in plasmid pBR322 DNA induced by singlet molecular oxygen (¹O₂). This reactive species of oxygen was generated in an aqueous buffer system by the thermal dissociation of the endoperoxide of 3,3′-(1,4-naphthylene)dipropionate. Among the antioxidants examined, myricetin showed the highest protective ability, followed by tannic acid, (+) catechin, rutin, fisetin, luteolin and apigenin, when the inhibitory abilities were compared at 90 min after incubation. The protective abilities of these compounds were both time and concentration dependent. At equimolar concentrations (100 μM) the antioxidant effect of myricetin was better than that of other known antioxidants such as lipoate, -tocopherol and β-carotene. Data, when analysed in relation to the structures of various compounds, showed a rough correlation with protective abilities. Owing to the abundance of these compounds in our normal diet, they may play significant roles in preventing oxidative damage resulting from potentially deleterious ¹O₂.     

Assignment of 13C resonances of a nematic liquid crystal using off-magic angle spinning

A novel method for assigning the resonances in the 13C NMR spectrum of a static liquid crystalline sample in its nematic phase is proposed. The method is based on the fact that the carbon chemical shifts in the isotropic phase and in the oriented phase under static and off-magic angle spinning (OMAS) conditions are uniquely related by the tensorial property of the CSA tensor, requiring just one OMAS spectrum and the assignment in the isotropic phase. A computational procedure is proposed to take into account deviations arising out of non-ideal experimental conditions and the assignments are made by identifying the minimum in the differences in the frequencies between calculated and experimental line positions. Practical implementation of the method has also been demonstrated in the case of the liquid crystal N-(4-ethoxybenzylidene)-4-n-butylaniline.     

A simple spectrophotometric method for the determination of zirconium in U–Zr alloy samples in presence of fluoride ions

Journal of Radioanalytical and Nuclear Chemistry - A spectrophotometric method, circumventing interference from F− ions, during estimation of Zr in U-Zr alloy fuel, has been developed....     

Nematogens containing oxyethylene units at a lateral or terminal position and their mixtures with salts

Short terminal polyoxyethylene chains may be introduced into mesogens containing lateral substituents such as two hexyloxy chains or a crown-ether fragment. These compounds have a large nematic range near room temperature and can dissolve large amounts of the salt LiBF₄ without destroying the nematic arrangment. In the nematic phase, the ions are ordered and the quadrupolar splitting associated with these ions can allow this ordering to be monitored. Increasing the salt concentration does not seem to change the ordering of the individual ions. The ¹³C thermal evolution of the field-induced chemical shift in the oxyethylene (OE) units with or without salt does not show any real difference, indicating that the interaction between the ions and the mesogen is small. This means that there is very little change in conformation in the OE unit when adding salt to the mesogen.