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ABSTRACT: We have studied the ac conductivity of several compositions of strontium vanadate semiconducting glasses in the frequency range 10 Hz-2 MHz and in the temperature range 80-450 K. We have analysed the experimental results in the framework of the quantum tunnelling and classical hopping models. We observe that tunnelling of the overlapping large polarons is the most suitable mechanism for the ac conductivity of the strontium vanadate glasses.
Journal of Physics Condensed Matter 02/2001; 13(9):1979. · 2.55 Impact Factor
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ABSTRACT: The preparation of vanadate glasses containing barium oxide and their electrical properties in the temperature range of 80–500 K have been reported in this article. Analysis of the electrical properties has been made in the light of different hopping models. The multiphonon assisted hopping model of small polarons in the nonadiabatic regime, proposed by D. Emin [Phys. Rev. Lett. 32, 303 (1974)] have been observed to describe the temperature dependence of the conductivity data of these glasses over the entire temperature range of measurement. The parameters obtained from the fits of the experimental data to this model are reasonable and consistent with the glass composition. J. Schnakenberg’s model [Phys. Status Solidi 28, 623 (1968)] is also consistent with the temperature dependence of the conductivity data. Mott’s optical phonon assisted hopping model at high temperatures provides smaller values of the localization length. However, Mott’s variable range hopping model is valid at low temperatures. © 2000 American Institute of Physics.
Journal of Applied Physics 05/2000; · 2.17 Impact Factor
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ABSTRACT: The temperature and compositional dependences of the electrical conductivity of semiconducting calcium vanadate glasses have been reported in the temperature range 80-500 K. It has been observed that the multiphonon assisted hopping model of small polarons in the nonadiabatic regime, which considers the strong interaction of electrons with both the optical and acoustical phonons, can interpret the temperature dependence of the conductivity data of these glasses over the entire temperature range of measurement. The parameters obtained from the fits of the experimental data to this model appear reasonable and are consistent with the glass composition. On the other hand, Mott's nearest neighbour hopping model at high temperatures yields smaller values of the localization length. Moreover, Mott's variable range hopping model is consistent with the low temperature data.
Journal of Physics Condensed Matter 09/1999; 11(41):8061. · 2.55 Impact Factor
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ABSTRACT: The electrical conductivity of semiconducting magnesium vanadate glasses has been reported for a wide composition range in the temperature range of 80–500 K. The experimental results have been analyzed in the framework of different hopping models. It has been observed that the multiphonon assisted hopping model of small polarons in the nonadiabatic regime, proposed by Emin, can interpret the temperature dependence of the conductivity data of these glasses over the entire temperature range of measurement. The parameters obtained from the fits of the experimental data to this model appear reasonable and are consistent with the glass composition. On the other hand, Mott’s optical phonon assisted hopping model at high temperatures provides smaller values of the localization length. However, Mott’s variable range hopping model is consistent with the low temperature data. Schnakenberg’s model yields higher values of the hopping and the disorder energies than the activation energy obtained at the highest and the lowest temperature ranges. © 1999 American Institute of Physics.
Journal of Applied Physics 09/1999; · 2.17 Impact Factor
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ABSTRACT: Electrical conductivity of some alkaline earth vanadate glasses has been reported in the temperature range 80-500 K. It has been observed that the conductivity and the activation energy for different glass compositions did not differ markedly. The general behaviour of the temperature dependence of the conductivity is similar for all the glass compositions studied. At high temperatures, Mott's nearest neighbour hopping is applicable, while at low temperatures, variable range hopping is valid. The polaron hopping models of Schnakenberg and of Emin and coworkers are consistent with the experimental data in the entire temperature range of measurements. However, the polaron hopping model of Emin and coworkers is the most suitable to explain the observed behaviour. The effect of the different alkaline earth oxide modifiers on the electrical properties of the vanadate glasses is similar.
Journal of Physics Condensed Matter 12/1998; 10(34):7567. · 2.55 Impact Factor
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ABSTRACT: The effect of chlorophyllin (1.5 mg/kg body weight) on the clastogenicity of mercuric chloride (HgCl2) was studied in vivo in mouse bone marrow cells. HgCl2 (3.0, 6.0 and 12.0 mg/kg body weight) administered by gavage induced chromosomal aberrations at frequencies directly proportional to the dose. Chlorophyllin was not clastogenic, and significantly reduced the mitotic index when given alone. Chlorophyllin administered simultaneously with HgCl2 significantly reduced the frequencies of chromosomal aberrations in a dose-dependent manner. When given simultaneously with the lowest HgCl2 concentration tested (3.0 mg/kg body weight), chlorophyllin provided total protection. A lower degree of protection was given by chlorophyllin administered 2 hr before HgCl2. The data demonstrate the potential of green plant components to modify the genotoxic activity of HgCl2 when administered orally.
Food and Chemical Toxicology 12/1991; 29(11):777-9. · 3.00 Impact Factor
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ABSTRACT: The antagonistic effect of chlorophyllin was tested in reducing the clastogenic action of cesium chloride (CsCl) in vivo on mice bone marrow cells. CsCl induced chromosomal aberration in frequencies directly proportional to the dose administered. Chlorophyllin, when given alone, was not clastogenic even at a concentration of 1.5 mg/kg body wt. of the animal. Simultaneous administration of chlorophyllin and CsCl reduced chromosomal aberrations significantly at 24 h. Exposure to the same dose of chlorophyllin 2 h before exposure to CsCl also decreased clastogenic effects but to a lesser extent. These findings are of importance in view of the uptake of radioactive Cs by green plants after nuclear fallout.
Toxicology Letters 07/1991; 57(1):11-7. · 3.23 Impact Factor
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ABSTRACT: The potential of chlorophyllin in reducing clastogenicity was studied against two concentrations of each of three potent metallic clastogens (cesium chloride, mercuric chloride and cobalt chloride) in bone marrow cells of mice in vivo. The respective salts and chlorophyllin were administered orally to mice by gavaging in different combinations. Simultaneous administration of chlorophyllin with both concentrations of each salt reduced the clastogenic effects in the order Cs greater than Hg greater than Co. Chlorophyllin could not decrease the clastogenic effects when administered 2 h before the salts.
Biology of Metals 02/1991; 4(3):158-61.
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ABSTRACT: An attempt to summarise the phytochemical composition of the betel quid, formation of N-nitrosation products during chewing, results of carcinogenicity and mutagenicity studies and the relationship between betel chewing and submucous fibrosis have been made from presently available literature. The present review provides a better understanding of the capacity of the quid ingredients in inducing preneoplastic changes for evaluation of the risk involved with its chewing.
Journal of Ethnopharmacology 11/1989; 26(3):217-47. · 3.01 Impact Factor
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ABSTRACT: Chromosome analysis of bone marrow cells from 96 sex-matched Rattus norvegicus of 12 different age groups showed a significant increase in hypodiploid cells with ageing. However, in meiotic preparations from gonadal cells of male rats the frequency of hypodiploid or hyperdiploid cells did not change significantly. In situ DNA estimation of bone marrow nuclei, following Feulgen cytophotometry, also did not show any significant difference with gradual age changes.
Genome 07/1989; 32(3):389-92. · 1.65 Impact Factor
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ABSTRACT: Spawning of the two Indian major carps, rohu (Labeo rohita) and mrigal (Cirrhinus mrigala) could be induced by fish gonadotropin releasing hormone (GnRH) purified from murrel (Channa punctatus) hypothalamus. The ‘Linpe’ method i.e., GnRH plus a dopamine antagonist, pimozide, was used in combination with Ca2+. Channa GnRH (cGnRH) was injected in two different doses, 10 or 20 μg per kg body weight in combination with pimozide (1 mg per kg) and Ca2+ (300 μg per kg ) with an interval of 6 h. Induced spawning occurred in all six sets at the same time while control fish failed to spawn. The total number of eggs product was approximately 30 000–35 000 in mrigal and 50 000⧹260 000 in rohu. Percent of fertilized eggs in rohu was about 80% whereas it was about 90% in mrigal.The above mentioned combination of cGnRH, pimozide and Ca2+, was used to test germinal vesicle breakdown (GVBD) in catfish (Clarias batrachus) and perch (Anabas testudineus). Oocyte diameter was significantly increased in catfish (from 0.71 ± 0.08 to 1.03 ± 0.05 mm, P <0.005) and in perch (from 0.46± 0.03 to 0.74± 0.09 mm, P < 0.01) at 36 h in response to above mentioned treatment. Oocyte diameter remained unaltered in control fish. In catfish, 82% GVBD occurred between 40–44 h while in perch 67% GVBD could be noticed between 50–56 h in the treated fish. GVBD did not take place in control catfish and perch till after 10 days of observation. Results indicate that use of cGnRH in the ‘Linpe’ method with Ca2+ is highly satisfactory for induced breeding of Indian major carps and final maturation of catfish and perch ovary.
Aquaculture.
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ABSTRACT: The effect of chlorophyllin (1.5 mg/kg body weight) on the clastogenicity of mercuric chloride (HgCl2) was studied in vivo in mouse bone marrow cells. HgCl2 (3.0, 6.0 and 12.0 mg/kg body weight) administered by gavage induced chromosomal aberrations at frequencies directly proportional to the dose. Chlorophyllin was not clastogenic, and significantly reduced the mitotic index when given alone. Chlorophyllin administered simultaneously with HgCl2 significantly reduced the frequencies of chromosomal aberrations in a dose-dependent manner. When given simultaneously with the lowest HgCl2 concentration tested (3.0 mg/kg body weight), chlorophyllin provided total protection. A lower degree of protection was given by chlorophyllin administered 2 hr before HgCl2. The data demonstrate the potential of green plant components to modify the genotoxic activity of HgCl2 when administered orally.
Food and Chemical Toxicology.
