An organocatalytic route to the synthesis of (6S)-5,6-dihydro-6-[(2R)-2-hydroxy-6-phenylhexyl]-2H-pyran-2-one and ravensara lactones

An organocatalytic enantioselective synthesis of the title compounds has been achieved. The stereogenic centers were generated by the iterative use of proline catalyzed α-aminoxylations and HWE olefination of aldehydes while the lactone ring was constructed by ring closing metathesis.     

Preferential occupation of pyroxene sites by iron in diogenite meteorites

Three diogenite meteorites ALHA77256-121, Tatahounie and Bilanga are studied using Mössbauer spectroscopy to look at the iron occupancy in the two inequivalent pyroxene sites. Though the three meteorites belong to three different conditions, one is an Antarctica find, one is 75 years old fall and one is a recent fall, the iron occupancy in pyroxene sites is very similar. Fe^2?+? occupies only the less distorted site and hence a single sharp doublet is observed in the Mössbauer spectra of all these samples. In contrast eucrites show a distribution of iron ions in the two sites of pyroxenes.     

Extraction studies of plutonium from acidic solution using γ-ray induced PC-88A/TBP modified polymers

2-Ethylhexyl-2-ethylhexyl phosphonic acid (PC-88A) and Tributylphosphate (TBP) extractants have been attached to polypropylene (PP) in granular, film and non-woven fabric forms, by a simultaneous γ-ray irradiation method. The extraction of plutonium from the acidic radioactive liquid waste by modified polymers was studied by varying the γ-ray dose. The uptake of plutonium was also studied by polyethylene (PE) in film form. This modified polymer also showed extraction capability for plutonium from nitric acid medium. The uptake of plutonium depends upon the γ-ray dose as well as the nature and source of the polymer. Liquid–solid extraction studies showed that the equivalent amount of uptake of plutonium on TBP–polyethylene film requires twice the γ-ray dose as compare to TBP–polypropylene film. It was observed that at given γ-ray dose polypropylene fabric is not sturdy, compare to the granules and films, and material leach out in aqueous phase. The presence of other solvents like di-methyl formamide (DMF) and cyclohexane during γ-ray irradiation were able to enhance the extraction capabilities. The optimum conditions established during this study was successfully applied for the separation of plutonium, uranium and thorium from the fission products in acidic waste solution.     

Development of Raman-shifted probe laser beam for plasma diagnosis using polaro-interferometer

Optical diagnostics of laser-produced plasma requires a coherent, polarized probe beam synchronized with the pump beam. The probe beam should have energy above the background emission of plasma. Though the second harmonic probe beam satisfies most of the requirements, the plasma emission is larger at the harmonic frequencies of the pump. Hence, at high intensities we need a probe beam at non-harmonic frequencies. We have set up a Raman frequency shifted probe beam using a pressurized hydrogen cell that is pumped by the second harmonic of the Nd glass laser that operates at only one Stokes line of 673.75 nm.     

Optimization of headspace solid-phase microextraction for the determination of pesticide residues in vegetables and fruits.

A headspace solid-phase microextraction method has been developed for the determination of 8 pesticides in vegetables and fruits by using gas chromatography with an electron capture detector. Two types of fibers (polyacrylate, 85 microm and polydimethylsiloxane, 100 microm) have been assayed and compared. The main factors: extraction and desorption parameters, ionic strength, and the effects of dilution and organic solvents, were studied and optimized. The optimized procedures resulted in more than 80% recovery for all the investigated vegetable and fruit samples with RSD values below 10%.