Correlations between fission fragments for 172 MeV20Ne+197Au: A case study for incomplete fusion

Angular and energy correlations have been measured for coincident fission-fragment pairs from the reaction of¹⁹⁷Au with 8.6 MeV/u²⁰Ne. These data have been analyzed to test for fission after incomplete fusion and its admixture with fission generally attributed to the relatively pure compound-nucleus mechanism. A Monte Carlo kinematic simulation program has been written to provide a basis for detailed comparisons of the experimental data to the calculations that employ various mechanistic assumptions. We conclude that incomplete fusion is indeed a prominent precursor to fission even for incident energies of less than 10 MeV/u. Similar data from earlier studies have been reanalyzed and shown to be consistent with this conclusion.     

Nucleophilic behaviour of DBU towards imidazolides: one-pot synthesis of ε-caprolactam derived carbamates and amides

Herein, we report the DBU ring opening reactions with imidazolide which can be a facile method to generate the library of ε-caprolactam derived carbamates and amides under one-pot condition.     

Studies in claisen rearrangement : Novel thermal transformation of α-aryloxymethylacrylic acids and their derivatives

α-Aryloxymethylacrylic acids and their derivatives have been found to undergo some novel thermal transformations leading to the formation of ‘ene’ dimers. The structure of the dimer has been revised on the basis of degradation studies, extensive spectral data and isolation of intermediates.     

Trifluoroacetic acid catalyzed and thermal rearrangement ofα- aryloxymethyl cinnamic acids.

Severalα- aryloxymethyl cinnamic acids $\text{1}$ have been rearranged in refluxing trifluoroacetic acid (TFA). The thermal rearrangement of the same acids in Polyethylene glycol - 200 (PEG - 200) has also been investigated.     

A dianionic oxy-cope rearrangement route to benzotropones - part XII

The divinyl carbinols $\text{3}$ and $\text{6}$ furnished the benzotropones $\text{4}$ and $\text{7}$ respectively, when treated with base.     

A simple method for the determination of benzo[a]pyrene and benzo[k]fluoranthene in a mixture

Atmospheric particulate matter is routinely analysed for the concentration of the carcinogen benzo[a]pyrene (BaP). Benzo[k]fluoranthene (BkF) has identical spectral characteristics and interferes in the fluorimetric estimation. A simple method for the determination of BaP in the presence of BkF is described. Based on quenching of the fluorescence of BaP by the addition of small amounts of nitromethane, the method can be used for accurate estimation for wide concentration ratios of BaP to BkF ranging from 0.1 to 10.0.     

Nanocrystalline metal oxides as destructive adsorbents for organophosphorus compounds at ambient temperatures

Nanocrystals of magnesium oxide react with organophosphorus compounds at room temperature by dissociative chemisorption, which we term "destructive adsorption". This process involves cleavage of P-O and P-F bonds (but not P-C bonds) and immobilization of the resultant molecular fragments. These ultrafine powders have unusual crystalline shapes and possess high surface concentrations of reactive edge/corner and defect sites, and thereby display higher surface reactivity, normalized for surface area, than typical polycrystalline material. This high surface reactivity coupled with high surface area allows their use for effective decontamination of chemical warfare agents and related toxic substances. Herein data is presented for paraoxon, diisopropylfluorophosphate (DFP), and (CH3CH2O)2P(O)CH2-SC6H5 (DEPTMP). Solid-state NMR and IR spectroscopy indicate that all OR and F groups dissociate; this leaves bound -PO4, -F, and -OR groups for paraoxon, DFP, and DEPTMP, respectively. For paraoxon, it was shown that one monolayer reacts. For DEPTMP, the OR groups dissociate, but not the P-CH2SC6H5 group. The nanocrystalline MgO reacts much faster and in higher capacity than typical activated carbon samples, which physisorb but do not destructively adsorb these phosphorous compounds.     

Mixing Properties of Two-Dimensional Lattice Solutions of Amphiphiles

Lattice Monte Carlo simulations of two-dimensional amphiphile solutions are used to examine the accuracy of the mixing properties predicted by lattice theories such as the Flory-Huggins theory, random-solution approximation, and quasichemical approximation. The internal energy, Helmholtz free energy, and entropy of mixing have been calculated from the configurational energy data obtained from the simulations, and the effect of nonrandom mixing on these properties has been determined. The quasichemical approximation predicts the entropy and Helmholtz free energy of mixing accurately for the amphiphile solution, but fails to predict the energy of mixing, due to the presence of microphase (self-aggregation) separation, which is beyond the reach of the quasichemical approximation, a mean-field theory. Helmholtz free energy of mixing is predicted accurately, and the shielding of the solvophobic segments in the microphase leads to small energies of mixing compared to the entropy of mixing. Copyright 2000 Academic Press.     

Thermal decomposition of uranyl nitrate hexahydrate

TG-DTA-EGA studies have shown that anhydrous uranyl nitrate cannot be obtained by thermal decomposition of uranyl nitrate hexahydrate. Hydrolysis and polymerization of the salt during dehydration resulted in hydroxynitrates which decomposed in multiple steps with the evolution of oxides of nitrogen and water. The extent of hydrolysis dependend on the sample size, heating rate and nature of sample containment. Large samples on decomposition at relatively high heating rates showed evolution of nitric oxide even above 500°C. Infrared studies on the residues prepared at various temperatures supported the conclusions.