Detection of fallout155Eu and207Bi in a210Pb-dated lake sediment core

Low-energy -ray spectrometry is used to detect fallout¹⁵⁵Eu and²⁰⁷Bi in a²¹⁰Pb-dated sediment core from McKay Lake, Ottawa, Canada. Unlike²⁰⁷Bi which is detected only in two core sections deposited in the mid 1970's,¹⁵⁵Eu is consistently detectable to mid 1960's. A comparison of corresponding¹³⁷Cs and¹⁵⁵Eu inventories in the sediment core indicates that fallout¹⁵⁵Eu derives primarily from the thermal neutron fission of²³⁵U. The derived flux of unsupported²¹⁰Pb at the sediment/water interface is in agreement with previously estimated flux of atmospheric²¹⁰Pb in the Great Lakes region.     

Natural radioactivity distribution in geological matrices around Kaiga environment

Summary The activity and absorbed dose rate of the naturally occurring radionuclides, viz. ²³⁸U, ²³² Th and ⁴⁰K were determined in soil and rock samples collected around Kaiga site. The mean activity levels (Kaiga soil) of naturally occurring ²³² Th are comparable with that in worldwide soil, while concentrations of ²³⁸U and ⁴⁰K are lower than those in worldwide soil. The absorbed dose rate in outdoor air ranged 20-58 nGy ^. h^-1 with a mean of 33.3 nGy ^. h^-1, which is below the world average of 60 nGy ^. h^-1. The total effective dose rate in outdoor air for soils ranged 25.6-74.4 mSv ^. y^-1 with a mean of 43.0 mSv ^. y^-1. The estimated dose rate at Kaiga is comparable with that estimated at Kakrapar and Rawatbhata and much less than that estimated at coastal sites of India.     

Studies in spiroheterocycles. Part XVII. synthesis of novel fluorine containing spiro[indole-pyranobenzopyran] and spiro[indenopyran-indole] derivatives

An elegant one-step synthesis of two novel spiro ring systems viz: spiro[3H-indole-3,4′-(2′-amino-3′-carbonitrile-[4′H]-pyrano[3,2-c]benzopyran)]-2,5′(1H)-dione8 and spiro[(2-amino-3-carbonitrile-indeno[1,2-b]pyran)-4(5H)>3′-[3H]indole]-2′,5(1′H)-diones in 80–85% yields is described. The spiro heterocycles were prepared by the reactions of fluorine containing 3-dicyanomethylene-2H-indol-2-ones with 4-hydroxy-2H-1-benzopyran-2-one and 1H-indene-1,3(2H)-dione respectively. The synthesized compounds have been characterized on the basis of elemental analyses, ir, pmr, ¹⁹F nmr and mass spectral data.     

Determination of organophosphate pesticides at a carbon nanotube/organophosphorus hydrolase electrochemical biosensor

An amperometric biosensor for oganophosphorus (OP) pesticides based on a carbon nanotube (CNT)-modified transducer and an organophosphorus hydrolase (OPH) biocatalyst is described. A bilayer approach with the OPH layer atop of the CNT film was used for preparing the CNT/OPH biosensor. The CNT layer leads to a greatly improved anodic detection of the enzymatically generated p-nitrophenol product, including higher sensitivity and stability. The sensor performance was optimized with respect to the surface modification and operating conditions. Under the optimal conditions the biosensor was used to measure as low as 0.15 μM paraoxon and 0.8 μM methyl parathion with sensitivities of 25 and 6 nA/μM, respectively.     

Miscibility and phase separation in SAN/PMMA blends investigated by positron lifetime measurements

Miscibility and phase separation in SAN/PMMA blends have been investigated using DSC, IR spectroscopy and positron lifetime spectroscopy (PLS). Single broad glass transition observed throughout the blend compositions, may be due to overlap of two glass transitions. IR measurements clearly indicate the absence of strong interactions. This supports miscibility is due to intramolecular repulsive forces in the SAN component. On the other hand, free volume data show negative deviation from linear additivity indicating the blends are miscible. The interchain interaction parameter β exhibits a complex behavior and the extent of miscibility is not revealed. Following Wolf’s treatment, we have evaluated the geometry factor γ and hydrodynamic interaction parameter α and found α is a suitable parameter in predicting the miscibility window. The cloud points in SAN/PMMA blends increase with decreasing PMMA content. The change in free volume size correlates well with the observed change in cloud point.     

Electrometric end points in the oxidation of thiocyanate by permanganate. Determination of cerium

Summary Oxidation of thiocyanate by standard permanganate using electrometric end points is shown to be quantitative in 1.5–2.5N HCl medium and in the presence of ICl as catalyst. A method of estimating cerium(IV), based upon its reduction to cerium(III) by excess KSCN and potentiometric titration of the excess against KMnO₄, is also described.Sincere thanks of the author are due to Prof. S. S. Joshi for research facilities.     

Volumetric iodate method for the determination of thiocyanate

Direct titration of thiocyanate with standard potassium iodate solution is found to yield accurate results in a final hydrochloric acid concentration regulated between 1.5 and 3N. The end-point is determined either potentiometrically or with carbon tetrachloride indicator.     

Estimation of 90Sr in reprocessed uranium oxide samples

Summary A method has been developed for the estimation of ⁹⁰Sr in reprocessed uranium oxide samples obtained from the Purex processing of natural uranium spent fuel discharged from the research reactor. The method employs a combination of precipitation and solvent extraction procedure to eliminate other beta-impurities prior to resorting to the estimation of ⁹⁰Sr by beta-counting. ¹⁰⁶Ru was eliminated by volatalizing with perchloric acid, uranium was removed by carrier precipitation with strontium as sulphate. The sulphate precipitate was converted to carbonate and dissolved in nitric acid. ²³⁴Th and ²³⁴Pa were eliminated by synergistic solvent extraction using tri-n-butyl phosphate and thenoyl trifluoroacetone extractant mixture in xylene. An iron scavenging step was included to remove any residual impurities. Finally, strontium is precipitated as SrC₂O₄^. H₂O. The separated ⁹⁰Sr activity was followed to check the equilibrium growth of ⁹⁰Y.