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  • Author or Editor: M Aggarwal x
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Abstract  

The glass-forming tendency and specific heat in ice cold water-quenched Ge1−xSnxSe2.5 glassy alloys with 0<x<0.6 were investigated by means of differential scanning calorimetry. The heat of fusion ΔH f, the heat ΔH c associated with the crystallization of an amorphous phase and the glass transition temperatureT g were deduced from the DSC curves. The composition dependence of glass forming ability,T g and crystallization behavior has been discussed.

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Abstract  

234U of high isotopic purity (>99 atom%) as well as of high radiochemical, purity was separated from aged238Pu prepared by neutron irradiation of237Np. Methodologies based on ion exchange and solvent extraction procedures were used to achieve high decontamination factor from238Pu owing to the very high α-specific activity of238Pu (2800 times) in comparison to that of234U. Isotopic composition of purified234U was determined by thermal ionisation mass spectrometry. Alpha spectrometry was used for checking the radiochemical purity of234U with respect to concomitant α-emitting nuclides. The separated234U will be useful for different investigations using mass spectrometry and alpha spectrometry.

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Abstract  

Determination of actinides in the environmental and bioassay samples is important in view of the following factors: increasing energy production by nuclear reactors; environmental contamination due to fallout from nuclear weapons testing and burn up of nuclear-powered satellites; the growing emphasis on the desirability of a cleaner environment; and public concern over the potential hazards associated with nuclear reactors. Among the various actinides, plutonium is one of the most important due to the large amounts produced in the nuclear fuel cycle. Further, the extremely low levels of plutonium in the different biological and environmental samples demand the development of precise, accurate, and sensitive methods to arrive at meaningful conclusions from the results obtained in various studies. In addition to various other techniques available, alpha spectrometry is commonly used.

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Bipolaris sorokiniana (Sacc.) Shoemaker (Teleomorph: Cochliobolus sativus (Ito and Kuribayashi) Drechs. Ex. Dastur) is a serious necrotrophic pathogen of wheat and barley in several countries. In this paper we report on mechanism of resistance and histopathological changes that occur on pathogen attack in resistant and susceptible genotypes. Callose deposition was observed in the epidermal cell wall of resistant genotype, Pusa T3336 at 2DAI. Lignin deposition around mesophyll tissues was also strongly observed by Phloroglucinol-HCl test in Pusa T3336. Four days after inoculation (4DAI), the pathogen colonized the leaf tissues showing inter and intracellular hyphae in susceptible genotype, Agralocal. In resistant genotype, no colonization was observed. The host tissue in susceptible genotype showed degeneration away from the site of colonization and also showed loss of structural integrity thereby indicating the role of toxin in pathogenesis. Separation of plasmalemma from the cell wall was observed due to loss of electrolytes and degradation of chloroplast at 5 DAI in the susceptible genotypes was prominently seen through light microscopy.

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Abstract  

The process of urbanization and industrialization during las two decades has resulted in increased level of air pollution causing hazards to human health. Instrumental neutron activation analysis (INAA) using short and long term irradiation has been employed for the determination of more than 30 elements in suspended particulate matter (SPM) from six metropolitan cities and three industrial surroundings. A comparison of mean elemental contents in dust particulates from commercial, industrial and residential zones of Delhi, Calcutta, Madras, Cochin, Bombay and Nagpur cities has shown wide variation in toxic pollutant (As, Br, Cr, Cu, Hg and Sb) concentrations. Coastal areas have shown higher concentrations of Na, K, Cl and Br. Highly industrialized Bombay showed highest levels of Br, Cl, Cr, Fe, Mg, P, Rb and Sc. Mean elemental contents in fugitive and ambient dust of a cement factory and thermal power station (both in central India) are widely different. SPM levels in fugitive dust of the two industrial surroundings are higher by an order of magnitude compared to ambient air. Analysis of ambient air dust from a paper mill showed highest concentrations of Hg, Sb and Zn. Elemental data have been compared with those of Urban Particulate Matter (SRM 1648), Coal Fly Ash (SRM 1633a) and Vehicle Exhaust Particulate (NIES No. 8) which were analysed for quality control. An attempt has been made to attribute the elemental contents to possible sources of origin.

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Karnal bunt of wheat (Tilletia indica) is an important internationally quarantined disease from food security point of view. For understanding host specificity and host-pathogen interaction, putative pathogenicity-related genes were analysed in Tilletia indica in response to host factor at different time points. Highest radial mycelia growth (3.4 cm) was recorded in media amended with susceptible host factor followed by resistant host (2.6 cm) and control (2.0 cm) at 30 days after incubation significantly. Fourteen homologous sequences of putative pathogenicity-related genes, viz. TiPmk1, TiKss1, TiHog1, TiHsp70, TiKpp2, TiCts1, TiHos2, TiChs1, TiPrf1, TiSid1, TiSsp1, TiSte20, TiUbc4 and TiUkc1, were identified in T. indica by in silico analysis. Some of the pathogenicity-related genes were highly expressed significantly in T. indica in response to susceptible host factor as compared to resistant host factor. TiPmk1, TiHog1, TiKss1 were found highly upregulated up to 26-fold (3 days), 20-fold (3 days) and 18-fold (4 days), respectively, significantly in presence of susceptible host factor. The TiCts1 and TiChs1 showed transcripts up to 26-fold (4 days) and 20-fold (3 days) in the presence of susceptible host factor. Further, the TiUbc4 and TiUkc1 were found upregulated up to 20-fold and 7-fold at 8 days and 3 days post incubation. This study provided the insight on expression of putative pathogenicity-related genes in T. indica which will help in understanding the infection mechanism and basis for further functional genomics approach.

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Bipolaris sorokiniana, causal agent of spot blotch of wheat is a hemibiotrophic pathogen. This fungus produced a toxin in culture that induced necrosis not only in wheat but also in barley, sorghum and some weeds. The toxic compound purified by prep TLC from culture filtrate of virulent strain BS-75, characterized using NMR and GC-MS techniques, was identified to be ‘Bipolaroxin’, which is a first report of its production by B. sorokiniana infecting wheat. It is a bicyclical sesquiterpene belonging to family Eremophilane. Besides producing necrotic lesions on wheat, toxin (30 ng/ml) caused necrotic lesions on barley, maize, sorghum, Phalaris minor, Avena sativa and Cynodon dactylon as studied using leaf infiltration bioassay. Qualitative and quantitative differences among the pathogenically variable isolates were observed with respect to toxin production by TLC and HPLC. Different isolates produced bipolaroxin in the range of 0.05 µg/ml (BS-41) to 1.4 µg/ml (BS-75).

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