Activation of enriched environmental xenon by 14-MeV neutrons

The international monitoring system exists to verify compliance with the terms of the comprehensive test ban treaty. About 10% of the member stations will be capable of detecting radioxenon, which can be produced in nuclear detonations or through civilian processes. We have studied the activation of radioxenon by the prompt, intense spectrum of 14-MeV neutrons produced at the National Ignition Facility. While 14-MeV neutrons are not currently a significant contributor to the production of radioxenon, we find that radioxenon produced through activation of environmental xenon by 14-MeV neutrons would be distinguishable from activation by nuclear tests.     

Improved crystal quality and harmonic generation in GaSe doped with indium

GaSe crystals were doped with indium, and improvements in the mechanical properties and second-harmonic efficiency over pure crystals were obtained. Both effects are due to an improvement in the crystal quality of the material, and it was shown that doping with low levels of indium did not alter the intrinsic value of the nonlinear d coefficient.     

Silicium-Bestimmung in Stahl und Eisen

Ohne Zusammenfassung     

On-line HPLC combined with multivariate statistical process control for the monitoring of reactions

On-line high performance liquid chromatography is used to monitor a steady state reaction over 35.2 h, with 197 chromatograms recorded as the reaction progresses. For each chromatogram, peaks are detected, baseline corrected, aligned and integrated to provide a peak table consisting of the intensities of 19 peaks, two corresponding to the reactants, one to the product and one to the solvent, the remaining being impurities, by-products or intermediates. D-charts and Q-charts from multivariate statistical process control are applied to the data to determine which samples are out of control and also provide diagnostic insight into why these samples are problematic. The D-chart is best at looking at overall performance issues such as problems with mixing or difficulties with instrument operation, whereas the Q-charts are best at detecting impurities during the reaction.     

The First Bismuth Phosphide Complex: [Li(thf)4]+[{(tBuP)3}2Bi]−

Thermally unstable crystals of the title compound—the first bismuth phosphide complex to be structurally characterized (see picture)—are obtained by the reaction of [Bi(NMe₂)₃] with [tBuPHLi] (1:3) in THF/hexane. Berry pseudorotation of the pseudo-trigonal-bipyramidal [{(tBuP)₃}₂Bi]⁻ ion is prevented for steric reasons.     

Why Perform Code‐to‐Code Comparisons: A Vacuum Arc Discharge Simulation Case Study

Numerical modeling is increasingly becoming an indispensable tool for investigations in many fields of physics. Such modeling is especially useful in today's big science projects as a tool that can provide predictions and design parameters. The reliability of simulation results is thus essential. Code‐to‐code comparisons can help increase our confidence in simulation results, especially when other verification methods – such as comparison to theoretical models or experimental results – are limited or unavailable. In this paper, we describe a code‐to‐code comparison exercise wherein we compare one‐dimensional vacuum arc discharge simulation results from two independent particle‐in‐cell (PIC) codes. As part of our case study, we define a vacuum arc discharge test problem that can be used by other research groups for further comparison. Early disagreement between the two sets of our results motivated us to re‐examine the underlying methods in our codes. After remedying discrepancies, we observe good agreement in vacuum arc discharge time‐to‐breakdown, as well as in the time evolution of particle and current densities. This exercise demonstrates the usefulness of code‐to‐code comparisons and provides an example case study for the benefit of other research groups who may wish to carry out similar code‐to‐code comparisons (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Binaural temporal fine structure sensitivity, cognitive function, and spatial speech recognition of hearing-impaired listeners (L)

The relationships between spatial speech recognition (SSR; the ability to understand speech in complex spatial environments), binaural temporal fine structure (TFS) sensitivity, and three cognitive tasks were assessed for 17 hearing-impaired listeners. Correlations were observed between SSR, TFS sensitivity, and two of the three cognitive tasks, which became non-significant when age effects were controlled for, suggesting that reduced TFS sensitivity and certain cognitive deficits may share a common age-related cause. The third cognitive measure was also significantly correlated with SSR, but not with TFS sensitivity or age, suggesting an independent non-age-related cause.     

Thermal stability of brominated poly(isobutylene‐co‐isoprene)

The thermal stability of brominated isobutylene–isoprene rubber (BIIR) was investigated through studies of the elastomer and a model compound that accurately represented the reactive functionality within the polymer. An analysis of commercial BIIR and reaction products of brominated 2,2,4,8,8‐pentamethyl‐4‐nonene (BPMN) by NMR demonstrated that bromination of isobutylene–isoprene rubber by 1,3‐dibromo‐5,5‐dimethylhydantoin yielded a kinetically favored exomethylene substitution product, 3‐bromo‐6,6‐dimethyl‐2‐(2,2‐dimethylpropyl)‐1‐heptene ( 2 ), as opposed to the more stable endo‐isomer, (E,Z)‐4‐(bromomethyl)‐2,2,8,8‐tetramethyl‐4‐nonene ( 3 ). The exposure of BIIR and the brominated model compound BPMN to vulcanization temperatures led to the isomerization of 2 to 3 at a rate strongly dependent on HBr concentration. The elimination of HBr from these allylic bromides to produce exo‐ and endo‐conjugated dienes proceeded concurrently with isomerization, and the kinetics of these processes could be rationalized on the basis of a polar reaction mechanism. The product distributions obtained from both the model system and BIIR were consistent, thereby justifying an extension of the model compound approach to an analysis of BIIR vulcanization chemistry. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2019–2026, 2001     

Particle image velocimetry measurements in complex geometries

 One of the advantages of Particle Image Velocimetry (PIV) is its ability to determine the instantaneous flow field over two- or three-dimensional domains. Yet PIV has had limited application to complex flow passages because of the difficulty in replicating these geometries with optically transparent materials. In this work, we describe a method for overcoming this difficulty using rapid prototyping techniques. As an illustrative example, the technique has been used to characterize flow in a model of the human nasal cavity. Received: 12 January 1999/Accepted: 30 September 1999