Analysis of kinetic data for the dissolution of UO2 fuel pellets in nitric acid

Journal of Radioanalytical and Nuclear Chemistry - In the present study, the dissolution kinetics of UO2 pellets in nitric acid has been investigated. Kinetic rate expressions based on...     

Influence of K<Subscript>2</Subscript>Ti<Subscript>6</Subscript>O<Subscript>13</Subscript> on dielectric and barrier properties of polymer

Polymer composite comprising polyvinylidene fluoride (PVDF) and potassium hexatitante (K₂Ti₆O₁₃) was synthesized by solution casting. The effect of K₂Ti₆O₁₃ on surface, thermal, and electrical properties of polymer composite were investigated. The addition of K₂Ti₆O₁₃ with polymer leads to thermal degradation and transition of polymer composite from semi-crystalline to amorphous phase. The optimum results of contact angle for different loading wt% of K₂Ti₆O₁₃ were directly correlated with the surface morphology. Our experimental results confirmed the incorporation of K₂Ti₆O₁₃ in polymer by SEM micrographs. The evaluated dielectric properties (ε' = 424; tan δ = 2.14 at 130 °C and 100 Hz frequency for 20 wt% loading of K₂Ti₆O₁₃) for polymer composite are higher in compared to pure polymer. The enhancement in dielectric constant and changing the surface properties of polymer composite can be used for the development of electrochemical storage device applications.     

Luminescence in Ca1−xYxF2+x

Some compounds with fluorite structures in the system CaF₂–YF₃ were prepared by precipitation followed by thermal annealing at 1000 °C. Photoluminescence spectra of Ce³⁺ and Eu²⁺ were studied. In this host, Ce³⁺ exhibits PL, which is totally different from that observed for the constituent fluorides. Eu²⁺ emission, on the other hand, is almost the same as that for CaF₂. The changes are explained in terms of the defect structure of Ca_1?xY_xF_2+x.     

Use of chemical etching of CR-39 foils at elevated temperature for fast neutron personnel monitoring in India

CR-39 Solid State Nuclear Track Detecting foils (SSNTD), along with 1 mm thick polyethylene radiator, sealed in triple laminated pouches, are used for country wide Fast Neutron Personnel Monitoring in India. With the present system of processing by elevated temperature electrochemical etching (ETECE) and evaluation using automatic image analysis, only 16 foils are processed at a time and it is useful over the dose equivalent range 0.2 mSv to 10 mSv. It has been reported that, by processing CR-39 of good detection efficiency by chemical etching at elevated temperature, more numbers of foils can be processed simultaneously. In the present study, CR-39 foils from Pershore Moulding (UK) have been chemically etched using 7 N KOH under various conditions of temperature and etching durations and evaluated using high magnification microscope. The duration of chemical etching, has been optimized at a constant temperature of 60°C for chemical etching process. The characteristics of the chemically etched CR-39 foils are compared with the characteristics of the CR-39 foils processed by the existing system of ETECE and the detailed results are presented in the full text of the paper. It has been observed that by chemical etching process, the dose equivalent range of CR-39 foils can be extended above 60 mSv.      

Controllability of nonlinear systems

In this paper we obtain global controllability of a semilinear system involving monotone nonlinearities of both Lipschitzian and non-Lipschitzian types.     

One pot synthesis of important retinoid synthon by the catalytic regioselective bi-functionalization of acetylenes,alcohol and carbon monoxide

Base free Fe(CO)₅ catalyzed one-pot synthesis of E/Z alkyl 3-formyl-3-alkyl/aryl/ferrocenyl-2-propenoates (retinoid esters) was achieved by the photolysis of alcoholic solution of terminal acetylenes and carbon monoxide. 8–10 Mol% of ironpentacarbonyl was used as a catalyst for significant transformations of retinoid esters. During the photolysis, alkynes reduced by the simultaneous double functionalization esterification and formylation and resulted in regioselective E/Z isomers of alkyl 3-formyl-3-alkyl/aryl/ferrocenyl-2-propenoates. The bi-functionalization of acetylene is quite unusual and is not observed frequently. The highest yield of the retinoid esters was achieved with 3° alcohols (96%, for E and Z isomers) while the least yield was observed with 1° alcohols (25%, for E and Z isomers). All retinoid esters are regiospecific and have exceptional biological significance to serve as key structural motifs in drug and pharmaceutical applications.     

An Entire Function Defined by a Nonlinear Recurrence Relation

For the nonlinear recurrence relation it is proved that the limit exists and defines an entire function of ₂ = ₁(1-₁).     

Highly facile and stereoselective intramolecular [2 +2]photocycloadditions of bis(alkenoyl)ketenedithioacetals

The conformational change induced by the introduction of a ketenedithioacetal moiety at C-4 of 1,7-substituted-1,6-heptadiene-3,5-diones results in favorable spatial relationships between the alkenoyl groups to effect efficient intramolecular cycloadditions: irradiation of bis(alkenoyl)ketenedithioacetals in solution leads to facile and stereospecific intramolecular [2 + 2] photocycloadditions resulting in the formation of substituted bicyclo[3.2.0]heptane-2,4-diones, the observed conformational rigidity of which is attributed to the push-pull character of the ketenedithioacetal group.