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  • Author or Editor: R. Aggarwal x
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Abstract  

Investigations have been carried out for the electrodeposition of milligram amounts of uranium on electropolished stainless steel disks with an objective of preparing good quality sources for -spectrometric studies on uranium. The parameters studied include the variation of electrodeposition yield as a function of voltage, time, distance between the cathode and anode, and the volume of 0.2M ammonium oxalate solution. The conditions selected for preparing good quality sources with nearly 100% yield were: electrodeposition voltage 25 V, time of deposition 15 min, volume of 0.2M ammonium oxalate solution in the cell 4 ml and a distance of 2 cm between the cathode and anode. The sources prepared using this method have been used successfully for the -spectrometric determination of234U/238U ratios in uranium samples.

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Abstract  

Experimental evaluation of a commonly used silicon surface barrier detector and of the recently introduced passivated ion implanted detector for alpha spectrometry is reported in terms of FWHM, peak to valley ratio, tail parameter and % tail contribution per unit alpha activity ratio using electrodeposited sources of plutonium prepared on platinum backing material. For this purpose, detectors of nearly the same diameter were employed (100 mm2 silicon surface barrier detector with a diamater of 1.13 cm and 80 mm2 passivated ion implanted silicon detector with a diameter of 1.01 cm). It is shown that the recently introduced passivated ion implanted detectors give smaller tailing effects. But there is no significant difference between the two detectors used in the present work w.r.t. FWHM and peak to valley ratios. Further, it is observed that the peak to valley ratio can be used to get an idea about240Pu/239Pu and241Am/238Pu alpha-activity ratios in the sample.

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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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Abstract  

Determination of239Pu/233U,241Am/233U and244Cm/233U alpha activity ratios is required when using233U as a tracer for the determination of plutonium, americium and curium by alpha spectrometry. Precision and accuracy in the determination of these alpha activity ratios was evaluated by preparing synthetic mixtures from solutions of enriched isotopes of239Pu,241Am,244Cm and233U. Separate synthetic mixtures were prepared for each of the three alpha activity ratios. The sources from the synthetic mixtures were prepared by direct evaporation method using tetra ethylene glycol /TEG/ as a spreading agent, alpha spectra were recorded by employing solid state silicon surface barrier detectors coupled to a 4 K analyzer and the alpha spectra were evaluated by a method based on the geometric progression decrease for the far tail of the spectrum. Large area detector /i.e. 450 mm2/ was observed to reduce the effect of nonhomogeneous distribution, if any, of the two elements present in the source. Precision and accuracy of about 1% is demonstrated for the determination of239Pu/233U,241Am/233U and244Cm/233U alpha activity ratios using large area silicon surface barrier detector.

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Chickpea (Cicer arietinum) seeds treated with powdered preparation of Gliocladium virens (Gv) alone @ 3 g/kg seed or in combination with vitavax (0.1%) showed colonization of G. virens on seed coat, collar region, plumule and radicle. Microscopic examination revealed that colonization of seed with mycelia and spores of antagonist started 24 h after incubation. Major portion of the seedling was covered with in 48 hrs. Population dynamics of G. virens monitored at different time inter­vals in spermosphere, rhizosphere and non-rhizosphere region in pathogen infested and non-infested soil using Trichoderma Selective Medium showed that population of G. virens increased initially up to 30 days and then gradually declined. The highest population was observed in spermosphere (7 x 105/g) followed by rhizosphere (6.3 x 104/g), when seeds treated with Gv + vitavax were sown in pathogen infested soil.

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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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Abstract  

A reverse isotope dilution alpha spectrometric /R-IDAS/ method using239Pu as a spike is described for the determination of plutonium concentration in high burn-up fuel samples wth238Pu/(239Pu+240Pu) alpha activity ratio >0.5, without resorting to any purification from241Am and a bulk of other impurities. It involves the addition of a pre-clibrated spike solution to a known aliquot of the plutonium sample solution followed by source preparation using TEG as a spreading agent. The results obtained on a number of plutonium samples containing 20–80% of241Am /alpha activity wise/ using this method are compared with those achieved by R-IDAS using purification with TTA, with respect to precision and accuracy. Precision and accuracy of 0.5% are demonstrated. This method eliminates the need of any separation and purification of plutonium from241Am and a bulk of other impurities like uranium.

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Abstract  

A direct evaporation method is described for the preparation of sources using stainless steel as the backing material and tetraethylene glycol (TEG) as a spreading agent in the presence of large amounts of uranium. It is shown that FWHM and tail contribution at the low energy peak due to energy degradation of the high energy peak can be optimized by heating the source under controlled conditions in a furnace at 500–600°C for about 15 min. An accuracy of 0.5–1% is demonstrated for the determination of238Pu/(239Pu+240Pu) alpha activity ratio in the U/Pu range of 10 to 1500 generally encountered in dissolver solution of irradiated fuel.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
S. Aggarwal
,
A. Almaula
,
P. Khodade
,
A. Parab
,
R. Duggal
,
C. Singh
,
A. Rawat
,
G. Chourasiya
,
S. Chitambar
, and
H. Jain

Abstract  

K-factors (= certified isotope ratio/observed isotope ratio) are determined for the isotope abundance measurements of uranium and plutonium by thermal ionisation mass spectrometry. An mdf of 0.07% and 0.18% per mass unit differing by a factor of about 3, is obtained for uranium and plutonium, respectively, employing double rhenium filament assembly in the ion source and Faraday cup as the detector using the presently available isotopic reference materials of uranium and plutonium.

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