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P Babu

Publications and source records attributed to P Babu.

12 recordsLinked to original sources
PubMed2006

Fluorescence properties of Nd3+-doped tellurite glasses.

The compositional and concentration dependence of luminescence of the (4)F(3/2)-->(4)I(J) (J=13/2, 11/2 and 9/2) transitions in four Nd(3+)-doped tellurite based glasses has been studied. The free-ion energy levels obtained for 60TeO(2)+39ZnO(2)+1.0Nd(2)O(3) (TZN10) glass have been analysed using the free-ion Hamiltonian model and compared with similar results obtained for Nd(3+):glass systems. The absorption spectrum of TZN10 glass has been analysed using the Judd-Ofelt theory. Relatively longer decay rates have been obtained for Nd(3+)-doped phosphotellurite glasses. The emission characteristics of the (4)F(3/2)-->(4)I(11/2) transition, of the Nd(3+):TZN10 glass, are found to be comparable to those obtained for Nd(3+):phosphate laser glasses. The non-exponential shape of the emission decay curves for the (4)F(3/2)-->(4)I(11/2) transition is attributed to the presence of energy transfer processes between the Nd(3+) ions.

Fluorescence↗
PubMed2005

Fluorescence properties of Eu3+ ions doped borate and fluoroborate glasses containing lithium, zinc and lead.

The influence of glass composition on the fluorescence properties of Eu3+ ions doped borate and fluoroborate glasses modified with Li+, Zn2+ and Pb2+ cations have been investigated. The magnitude of splittings of 7F1 levels are analyzed using crystal-field (CF) analysis. The relative intensities of 5D0 --> 7F2 to 5D0 --> 7F1 transitions, crystal-field strength parameters and decay times of the 5D0 level have been determined and are found to be lower for Pb based glasses than those of Zn/Li based glasses. The lifetimes of 5D0 level are found to increase when borate glasses are modified with pure fluorides than with oxides and oxyfluorides. The fluorescence decay of 5D0 level fits perfect single exponential in the Eu3+:glass systems studied which indicates the absence of energy transfer between Eu3+ ions in these glasses.

Borates↗
PubMed2003

Pyrene-derived novel one- and two-component organogelators.

A new class of alkyl-chain-appended pyrene derivatives 4-14 were synthesized and evaluated for their gelation abilities. Depending on the nature of the linking group, these compounds gelated a number of organic solvents, either in the presence or in the absence of the acceptor molecule 2,4,7-trinitrofluorenone (TNF). Compounds with ester, ether, or alkyl linkages gelated a number of hydroxylic and hydrocarbon solvents by means of a charge-transfer interaction with TNF, while compounds with amide, urethane and urea linkers formed gels on their own in a variety of solvents by means of pi-pi stacking and hydrogen-bonding interactions. The Xray crystal structure of urethane (S)-12 showed hydrogen-bonding and stacking features, as suggested by the model. The gels obtained were investigated by spectroscopic and electron microscopic techniques which provided structural insights.

Journal Article↗
PubMed2001

Surfactant-induced lipid peroxidation in a tropical euryhaline teleost Oreochromis mossambicus (Tilapia) adapted to fresh water.

Exposure to anionic (sodium dodecyl sulfate, SDS), cationic (cetyl trimethyl ammonium bromide CTAB) and non ionic (Triton X-100) surfactants at a sub lethal concentration of 1 ppm resulted in severe oxidative stress in the hepatic, renal and cardiac tissues of fresh water adapted Oreochromis mossambicus. Hepatic catalase showed significant increase (P<0.001) in all the surfactant exposed fish, but the renal enzyme was significantly increased only in CTAB dosed fish (P<0.001) and the cardiac enzyme showed significant increase in Triton (P<0.05) and CTAB dosed fish (P<0.001). SOD levels were significantly increased (P<0.001) in hepatic, renal and cardiac tissues of all the surfactant-treated fish. Glutathione reductase also was significantly increased (P<0.001) in the hepatic and renal tissues of surfactant dosed fish except cardiac tissues of CTAB exposed animals. Glutathione levels in the tissues studied were significantly higher in the surfactant treated animals (P<0.001) whereas malondialdehyde levels were significantly elevated only in the hepatic tissues of animals exposed to Triton (P<0.001). The surfactants based on their charge, antioxidant profile and in vivo metabolism may be arranged in the order of decreasing toxicity as CTAB > Triton > SDS. Thus it may be inferred from the present study that the antioxidant defenses and the in vivo metabolism of the surfactants are key factors in deciding the surfactant toxicity.

Adaptation, Physiological↗
PubMed1987

Studies on transvection at the bithorax complex in Drosophila melanogaster.

We have studied the influence of some mutations in the bithorax complex on the observed synapsis dependent phenotype of the genotypes Cbx1Ubx1/+ and bx3 4e/Ubx1. The effect of these mutations is similar to that introduced by disruption of pairing or by the za mutation. Among the bx mutations, we find that bx8 behaves differently from most other bx mutations in its influence on the synapsis dependent phenotype. This observation induced us to map the position of bx8 with respect to other bx mutations; we find that it maps between bx3 4e and bx3. We show how some of the observations reported here can be fitted into a model of activation of the bithorax complex proposed by one of us.

Animals↗
PubMed1980

Genetic mosaics of Caenorhabditis elegans: a tissue-specific fluorescent mutant.

Genetic mosaics can be generated by x-irradiation in the simple nematode Caenorhabditis elegans. A mutation in the gene flu-3 alters the characteristic autofluorescence of intestinal cells under ultraviolet light and can be used as a cell- and tissue-specific marker. Embryos heterozygous for flu-3 give rise to adults with patches of these altered intestinal cells. The previously established intestinal cell lineage in Caenorhabditis elegans and the distribution and sizes of the fluorescent patches are consistent with a somatic segregation of the flu-3 allele.

Animals↗
PubMed1980

Mutagen sensitivity of kynureninase mutants of the nematode Caenorhabditis elegans.

Mutants in the gene flu-2 of the free-living nematode Caenorhabditis elegans are characterised by an altered autofluorescence of the intestine cells, from the light blue of wild-type to a dull green colour. The properties of flu-2 mutants have been investigated. L-kynureninase activity has been detected in wild-type C. elegans. The flu-2 mutants have markedly reduced kynureninase activity, as predicted earlier from chromatographic analysis of tryptophan catabolites of wild-type and mutant worms. Associated with this enzymatic block, all flu-2 mutants have enhanced sensitivity to ethyl methane sulfonate (EMS) and gamma-rays.

Animals↗
PubMed1980

Kynurenine hydroxylase mutants of the nematode Caenorhabditis elegans.

The relation of intestinal autofluorescence to tryptophan catabolism in the free-living nematode Caenorhabditis elegans has been investigated. L-Kynurenine hydroxylase (EC 1.14.13.9) activity has been detected in normal (wild-type) individuals. Mutants in the gene flu-1 which are characterized by an altered autofluorescence of the intestine cells, i.e., more intense than wild type and bluish purple instead of light blue have also been examined. They show a markedly reduced activity of kynurenine hydroxylase. The finding supports the previously proposed model for altered fluorescence based on chromatographic identification of tryptophan catabolites present.

Animals↗
PubMed1977

Early developmental subdivisions of the wing disk in Drosophila.

The properties of the mutation wingless discovered by Sharma are discussed. It appears that this mutation interferes with a step leading to normal wing-notum compartmentation of the wing disk. From the study of mutational mosaics in the wingless locus we conclude that mutations in this gene can be autonomous in mosaics.

Animals↗