General Synthesis of 1‐Substituted 2‐Methylbenzimidazoles from Ketones and 2‐Aminoacetanilide

A novel method for preparation of 1‐substituted benzimidazoles via reductive amination of ketones with N‐differentiated 1,2‐diaminobenzenes is described. The method appears to be general in application to acyclic and cyclic ketones, as well as heteroatom‐substituted cyclic ketones.     

Development of XUV lasers at the RAL Central Laser Facility

Recent progress in the development of XUV lasers by research teams using high-power and ultrashort-pulse Nd: glass and KrF laser facilities at the Rutherford Appleton Laboratory is reviewed. Injector-amplifier operation and prepulse enhanced output of the Ge XXIII collisional laser driven by a kilojoule glass laser, enhanced gain in CVI recombination with picosecond CPA drive pulses from a glass laser, and optical field ionization and XUV harmonic generation with a KrF CPA laser are described.     

Mathematical efficiency calibration methods for high quality laboratory based gamma spectrometry systems

The efficiency calibration of laboratory based gamma spectrometry systems typically involves the purchase or construction of calibration samples that are supposed to represent the geometries of the unknown samples to be measured. For complete and correct calibrations, these sample containers must span the operational range of the system, which at times can include difficult configurations of size, density, matrix, and source distribution. The efficiency calibration of a system is dependent not only on the detector, but on the radiation attenuation factors in the detector–source configuration, and therefore is invalid unless all parameters of the sample assay condition are identical to the calibration condition. An alternative to source-based calibrations is to mathematically model the efficiency response of a given detector–sample configuration. In this approach, the measurement system is calibrated using physically accurate models whose parameters can generally be easily measured. Using modeled efficiencies, systems can be quickly adapted to changing sample containers and detector configurations. This paper explores the advantages of using mathematically computed efficiencies in place of traditional source-based measured efficiencies for laboratory samples, focusing specifically on the possibility of sample optimization for a given detector, uncertainty estimation, and cascade summing corrections.     

Establishing reactor operations from uranium targets used for the production of plutonium

This paper presents results from the examination of a number of archived neutron-irradiated uranium targets used for past plutonium production testing. Three of these targets were destructively characterized using Los Alamos National Laboratory actinide analytical chemistry capabilities. A validated conduct-of-operations protocol was followed for this characterization effort. Chemical analyses included measurements for radionuclides, uranium assay, uranium isotopic abundances, trace actinides, trace metals, and non-metals. Material scientists also examined materials for morphological and microstructural properties and individual particles were examined for trace impurities. After characterization of the targets was completed, a reactor modeling effort was undertaken to corroborate target details in historical records. Time since irradiation calculations utilized both activation and fission products. The described examination of uranium targets has a tremendous impact from a safeguards verification and nuclear forensics perspective.     

A translation of Bolzano's paper on the intermediate value theorem

This is the first English translation of Bolzano's paper, Rein analytischer Beweis des Lehrsatzes, dass zwischen je zwey Werthen, die ein entgegengesetzes Resultat gewähren, wenigstens eine reelle Wurzel der Gleichung liege (Prague 1817). It has already appeared in French, Russian, and Czechoslovakian translations. The paper represents an important stage in the rigorous foundation of analysis and is one of the earliest occasions when the continuity of a function and the convergence of an infinite series are both defined and used correctly.     

Unsteadiness and mixing in thermal plasma jets

This study was undertaken to examine the mechanisms which produce the large entrainment measured at the exit of thermal plasma torches. The experiments studied a Metco 7MB plasma torch with a 706 (6.35 mm diameter) anode nozzle and swirled argon gas injection. The vortex structure produced in the shear layer of the plasma jet was visualized using a laser shadowgraph system with a short exposure lime (10^–4 s). A high-speed video system provided information on the structure and unsteadiness of the hot potential core of the plume. Tile shear layer visualizations were compared to previous measurements of acoustical power spectra and indicate coherent vortex structure formation at low gas flowrates. At higher gas flowrates the shear layer rapidly broke down, producing relatively small scale turbulence. The visualizations of the hot potential core were compared to previous measurements of the torch voltage fluctuations caused by arc instabilities. At low flowrates the arc-produced voltage fluctuations were guile low card the phone was very steady. At higher flowrates the voltage fluctuations increased and produced surging and whipping in the hot potential core.     

Coupled cluster calculations of optical rotatory dispersion of (S)-methyloxirane

Coupled cluster (CC) and density-functional theory (DFT) calculations of optical rotation, [alpha](lambda), have been carried out for the difficult case of (S)-methyloxirane for comparison to recently published gas-phase cavity ringdown polarimetry data. Both theoretical methods are exquisitely sensitive to the choice of one-electron basis set, and diffuse functions have a particularly large impact on the computed values of [alpha](lambda). Furthermore, both methods show a surprising sensitivity to the choice of optimized geometry, with [alpha](355) values varying by as much as 15 deg dm(-1) (g/mL)(-1) among molecular structures that differ only negligibly. Although at first glance the DFT/B3LYP values of [alpha](355) appear to be superior to those from CC theory, the success of DFT in this case appears to stem from a significant underestimation of the lowest (Rydberg) excitation energy in methyloxirane, resulting in a shift of the first-order pole in [alpha](lambda) (the Cotton effect) towards the experimentally chosen incident radiation lines. This leads to a fortuitous positive shift in the value of [alpha](355) towards the experimental result. The coupled cluster singles and doubles model, on the other hand, correctly predicts the position of the absorption pole (to within 0.05 eV of the experimental result), but fails to describe correctly the shape/curvature of the ORD region lambda=355, resulting in an incorrect prediction of both the magnitude and the sign of the optical rotation.