Production of 99Mo and 64Cu in a mixed field of photons and neutrons in a clinical electron linear accelerator

Journal of Radioanalytical and Nuclear Chemistry - The medical isotopes 99Mo and 64Cu were produced via the dual routes of 100Mo(γ,n)99Mo + 98Mo(n,γ)99Mo and 65Cu(γ,n)...     

Characterization of cyclotetramethylenetetranitramine (HMX) thermal degradation by isotope analyses with analytical pyrolysis-atmospheric pressure ionization tandem mass spectrometry

Analytical pyrolysis-atmospberic pressure ionization (Py-API) tandem mass Spectrometry was used in the structure elucidation of the oxidalive and non-oxidative thermal decomposition products of cyclotetramethylenetetranitramine (HMX). The [¹⁵NO₂]-, [¹⁵N₈]- and [²H₈]-HMX isotope preparations provided fundamental information in the determination of the identities of the various pyrolyzate species. All RDX pyrolysis product ions that were identified by Py-API tandem mass Spectrometry, i.e. m/z 44, 60, 74, 75, 85 and 98, were present in the pyrolyzate of HMX. In both RDX and HMX investigations, these ions provided identical mass spectral daughter ion analyses. HMX, however, provided additional ions at m/z 30, 58, 69, 71, 83 and 141. Of all thirteen ions identified in the Py-APJ mass spectrum of HMX, only that at m/z 75 contained a nitrogen atom that originated from the NO₂ group. Standards analysis confirmed the identities of the ions at m/z 69, 71 and 141 as methyleneaminoacetonitrile, methylaminoacetonitrile and the caged compound hoxamethylenetetraamine, respectively. Isotopic analyses provided a high degree of confidence on the structural assignments of the ions at m/z 30 and 58 as methyleneimine and methyleneformamide; the ion at m/z 83, however, appeared to be a heterocyclic compound with daughter ion mass spectral elements similar to but not identical with that of 1-methylimidazole and 3-methylpyrazole.     

A new volumetric method for the determination of molybdenum(VI)

Summary A new volumetric method has been developed for the determination of molybdenum(VI). The method consists in the reduction of molybdenum(VI) by heating with a slight excess of hydrazine sulphate in 1 to 2 M hydrochloric acid medium for ten minutes on a water bath. The mixture is cooled and the molybdenum(V) obtained determined by titration with a standard solution of ceric sulphate at an overall acidity of 4 N hydrochloric acid, using diphenyl benzidine as indicator and adding 5 ml of syrupy phosphoric acid for 50 ml of the mixture. Alternately the molybdenum(V) can be titrated with a standard solution of ceric sulphate at an overall acidity of 3 N hydrochloric acid using ferroin as indicator and adding 5 ml of syrupy phosphoric acid for 50 ml of the titration mixture. The molybdenum(V) can also be titrated with a standard solution of sodium vanadate in 8 N sulphuric acid medium, using N-phenyl anthranilic acid as indicator. Alternately, the titration with sodium vanadate can be made with diphenyl benzidine as indicator in 4 N acid medium, adding 5 ml of syrupy phosphoric acid and 1 ml of 1.0 M oxalic acid to catalyse the indicator action. The method now proposed is much more convenient than the methods currently available. It is simple because it does not require any costly chemicals or complicated apparatus. Furthermore, it has the advantages of great rapidity and excellent precision.     

Development of an HPLC Assay Method for Lenalidomide

Chromatographic separation of lenalidomide and its impurities was achieved on an Inertsil ODS-3 V column using a mobile phase consisting of a mixture of buffer, acetonitrile and methanol in the ratio 80:8:12 v/v. Degradation studies were performed on bulk samples of lenalidomide subjected to 0.5 N hydrochloric acid, 0.5 N sodium hydroxide, 10% v/v hydrogen peroxide, heating to 60 °C and UV light at 254 nm. Degradation was observed only under base hydrolysis conditions. The developed LC method gave a mass balance close to 99.5%, proving it to be suitable for stability studies and was validated with respect to linearity, accuracy, precision and robustness.     

Review of electronic transport models for thermoelectric materials

Thermoelectric devices have gained importance in recent years as viable solutions for applications such as spot cooling of electronic components, remote power generation in space stations and satellites etc. These solid-state devices have long been known for their reliability rather than their efficiency; they contain no moving parts, and their performance relies primarily on material selection, which has not generated many excellent candidates. Research in recent years has been focused on developing both thermoelectric structures and materials that have high efficiency. In general, thermoelectric research is two-pronged with (1) experiments focused on finding new materials and structures with enhanced thermoelectric performance and (2) analytical models that predict thermoelectric behavior to enable better design and optimization of materials and structures. While numerous reviews have discussed the importance of and dependence on materials for thermoelectric performance, an overview of how to predict the performance of various materials and structures based on fundamental quantities is lacking. In this paper we present a review of the theoretical models that were developed since thermoelectricity was first observed in 1821 by Seebeck and how these models have guided experimental material search for improved thermoelectric devices. A new quantum model is also presented, which provides opportunities for the optimization of nanoscale materials to enhance thermoelectric performance.     

Chiral Recognition of Zolmitriptan by Modified Cyclodextrins

The two pyrrolidinylidenesulfamido‐modified β‐cyclodextrins (β‐CDs) 3 and 4 were prepared and studied for chiral discrimination of the enantiomers (R)‐ and (S)‐ 1 of zolmitriptan. The pyrrolidinylidenesulfamido spacer improved the chiral discrimination and binding abilities of these modified cyclodextrins. The hosts 3 and 4 showed higher selectivity for (S)‐ 1 . The association constants (Table) and enantioselectivity factors were calculated for the complexes of (R)‐ and (S)‐ 1 with the β‐CDs 2 – 4 . The formation of host?guest complexes was confirmed by ¹H‐NMR studies.     

Thermal behaviour of fentanyl and its analogues during flash pyrolysis

Flash pyrolysis of fentanyl and its analogues has been studied on pyrolysis-gas chromatograph-mass spectrometer (Py-GC-MS) system. Initial pyrolytic fragmentation of these compounds led to the formation of N-substituted-1,2,5,6-tetrahydropyridine and N-phenylpropanamide as the primary pyrolytic products. Moreover, depending up on the furnace temperature, these pyrolytic products can also undergo further fragmentation to give different compounds. We, herein, discuss the probable fragmentation routes of parent as well as pyrolytic products. This study will be useful while developing technologies for thermal aerosol generation of fentanyl and related compounds.     

Relative stability of planar versus double-ring tubular isomers of neutral and anionic boron cluster B20 and B20-

High-level ab initio molecular-orbital methods have been employed to determine the relative stability among four neutral and anionic B20 isomers, particularly the double-ring tubular isomer versus three low-lying planar isomers. Calculations with the fourth-order Moller-Plessset perturbation theory [MP4(SDQ)] and Dunning's correlation consistent polarized valence triple zeta basis set as well as with the coupled-cluster method including single, double, and noniteratively perturbative triple excitations and the 6-311G(d) basis set show that the double-ring tubular isomer is appreciably lower in energy than the three planar isomers and is thus likely the global minimum of neutral B20 cluster. In contrast, calculations with the MP4(SDQ) level of theory and 6-311+G(d) basis set show that the double-ring anion isomer is appreciably higher in energy than two of the three planar isomers. In addition, the temperature effects on the relative stability of both 10B20- and 11B20- anion isomers are examined using the density-functional theory. It is found that the three planar anion isomers become increasingly more stable than the double-ring isomer with increasing the temperature. These results are consistent with the previous conclusion based on a joint experimental/simulated anion photoelectron spectroscopy study [B. Kiran et al., Proc. Natl. Acad. Sci. U.S.A. 102, 961 (2005)], that is, the double-ring anion isomer is notably absent from the experimental spectra. The high stability of the double-ring neutral isomer of B20 can be attributed in part to the strong aromaticity as characterized by its large negative nucleus-independent chemical shift. The high-level ab initio calculations suggest that the planar-to-tubular structural transition starts at B20 for neutral clusters but should occur beyond the size of B20- for the anion clusters.     

Carrier-free estimation of106Ru in urine

A simple carrier-free method has been developed for estimating 0.1 to 1.1 Bq of¹⁰⁶Ru in urine. The organic matter present in urine samples was completely destroyed by wet ashing using nitric acid-peroxide mixture in presence of sulfuric acid. Ruthenium was oxidized to tetroxide using potassium periodate and allowed to react in-situ with polyethylene powder. The powder was separated, washed, pelletized and its -activity was counted. Recovery of¹⁰⁶Ru is found to be better than 80% with a minimum detection limit of 0.2 Bq/dm³ which is less than the DRL value specified by International Commission on Radiological Protection (ICRP).