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  • Author or Editor: S. Kumar x
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Abstract  

The techniques of gamma-radiolysis, UV photolysis and hydrogen-induced reduction of aqueous palladium perchlorate to ultrafine particles of Pd, in the presence of alumina sol, have been studied. As compared to H2-induced reduction, both UV photolytic and gamma-radiolytic reduction methods lead to a very stable, brown colored Pd colloid with relatively less absorption in the higher wavelength region and possessing much smaller volume average particle size (62 and 61 nm, respectively). Higher concentration of alumina sol and increase in pH from 1.8 to 7.2, favour the formation of smaller sized particles as determined by the dynamic light scattering technique.

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Abstract  

57Fe Mössbauer spectroscopy has been employed to characterize the chemical composition of iron aerosols collected from three distinct groups of sites representing remote, urban and industrially active areas. The Mössbauer spectra clearly show this environmental difference. The fact that the spectra of the samples collected from the remote areas are quite similar to those of clay minerals corroborates the view that iron aerosols are soil derived. Similarly the predominant presence of -Fe2O3 and Fe3O4 in the close vicinity of industrial activities suggests that the Mössbauer spectroscopy can help identify the anthropogenic processes against the natural ones.

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Abstract  

During reductive partitioning, hydrazoic acid is produced by the reaction of hydrazine and nitrous acid. In this paper an empirical model for the extraction of hydrazoic acid and its temperature dependence is reported.

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Abstract  

The spin transitions in two new cationic complexes of iron, i. e., iron bipyridine formate, [Fe/bipy/3]/HCOO/2. 5/HCOOH/ and iron bipyridine tetrafluoro borate, [Fe/bipy/3]/BF4/2. 2H2O have been studied by using Mössbauer spectroscopy. From quadrupole splitting values, at different temperatures, it has been established that both the complexes show the coexistence of both the high spin state and the low spin state at 300 K while complete transformation to low spin state occurs at 77 K. Both compounds were prepared by electrochemical technique.

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Abstract  

A radiation dose assessment exercise was carried out for the Ipomea batata, Allium sativum, Dacaus carota, and Solanum tuberosum due to naturally available radionuclide 40K, 238U and 232Th in the Domiasiat area of Meghalaya. The concentration of radionuclides in biota as well as corresponding soil was measured by precipitation method using NaI detector for continuous 12 months. Transfer factor was calculated and was, for 40K(3.96E−05, 3.40E−05, 3.40E−05, 2.70E−05), for 232Th(3.94E−05, 3.20E−05, 3.20E−054.93E−05), for 238U(3.60E−05, 3.89E−05, 3.85E−054.57E−05), respectively in each biota due to each radionuclide. The point source dose distribution (source ↔ target) hypotheses was applied for the consideration of absorbed fraction. The generated data were modeled using the FASSET method and obtained dose was 8.42E−03, 8.36E−03, 7.78E−03, 7.74E−03 μGy h−1, respectively and finally compared with the IAEA and UNSCEAR dataset for screening level dose for terrestrial biota.

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Abstract  

Radiation dose-risk assessment was carried out for cereal species Brassica compestris var. dichotoma, Oryza sativa var. Shalum1, Zea mays, Lactuca indica, Cumunis sativum, and Clocasia esculanta due to naturally available radionuclides 40K, 238U and 232Th in Domiasiat area. The activity in biota and corresponding soil was measured by precipitation method using NaI(TI) detector. Transfer factor (TF) was for Oryza spp. (1.00E−01-40K, 8.76E−05-232Th, and 9.11E−05-238U), for Brassica spp. (5.39E−01-40K, 8.17E−04-232Th and 2.96E−04-238U) and for Zea spp. (3.41E−01-40K, 5.84E−05-232Th, 8.87E−05-238U) etc., respectively. A detailed physio-morphological study of the biota and extensive investigation of ecosystem was carried out for assessment. The data was modeled using FASSET for dose estimation and obtained total dose was 1.58E−04 
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in Oryza spp., 2.87E−04 
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Brassica spp. and 6.90E−03 
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in Zea spp. etc. The dose was compared with the UNSCEAR dataset for screening level dose for biota. Zea spp. was more susceptible for the chronic radiation exposure.
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A simple, rapid, and sensitive HPTLC method has been developed for determination of anticancer agent nimbolide in herbal extracts of Azadirachta indica . Samples were applied directly to silica gel 60 F 254 HPTLC plates as stationary phase. Plates were developed to a distance of 85 mm in a glass twin-trough chamber with ethyl acetate-hexane 5:5 ( v/v ) as mobile phase at room temperature (25 ± 2°C). This system was found to give compact spots for nimbolide ( R F 0.49 ± 0.02) for quantities in the range 2–20 μg. Densitometric analysis of nimbolide was carried out in the absorbance mode at 254 nm. Linear regression analysis data for the calibration plots showed a good linear relationship with r = 0.9997. The limits of detection and quantification were 3.3 μg and 11.03 μg, respectively. The method was confirmed to be suitable for accurate determination at nimbolide in extracts of neem leaves. Statistical analysis of the data showed that the method is reproducible and selective for the estimation of nimbolide.

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Abstract  

Sorption of some univalent, divalent and trivalent metal ions has been studied on the hydrogen form of titanium arsenate and titanium tungstoarsenate gels as a function of initial solution concentration at pH 5–6. The effect of pH on maximum uptake (Qmax) has also been seen for some representative ions. Sorption of metal ion becomes almost negligible below pH 1.8, with the exception of monovalent cations. Rubidium ions exhibit interesting adsorption behaviour. The data have been compared with the exchange properties of these two inorganic ion exchangers, as reported earlier6,8.

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Abstract

Heterobinuclear macrocyclic complexes, i.e. CuCoL 1, CuFeL 2 and CoVL 3, have been synthesized and anchored onto modified carbamate Al2O3 in order to obtain new hybrid supported catalysts. The identities of the supported metal complexes were confirmed by FT–IR, SEM–EDS and AAS. TGA indicated that the catalysts were thermally stable up to 230 °C. These catalysts have been tested for the functionalization of n-hexane with molecular O2. The best result was obtained with CuFeL 2 over Al2O3 (ca. 19% overall conversion; 78% selectivity: hexan-2-one plus hexan-2-ol) and promoted conversion could be obtained with 2-pyrazinecarboxylic acid (as co-catalyst). The effects of various factors (temperature, O2 pressure, reaction time and catalyst concentration) were also investigated in detail. The impact of both C- and O- centred radical traps was also assessed to establish a radical mechanism.

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