Zeolites as hosts for novel optical and electronic materials

A review of the use of zeolites as hosts for electronically active guest materials is presented. Metal, semiconductor and conductive polymer nanoparticles as electronic and optical material composites are reported with special emphasis on their synthesis.     

Rapid detailed characterization of concrete shielding blocks utilizing internal natural radinuclides for calibration

Following many years of productive research, the 184-inch Cyclotron, the SuperHILAC, and the BEVALAC accelerators at the Berkeley Laboratory were closed, leaving thousands of concrete shielding blocks available for reuse, recycling, or disposal. The process history of these blocks precludes free release pending radiological characterization. This paper describes a procedure whereby a high efficiency shielded germanium spectrometer is used to rapidly characterize natural and man-made activity within the blocks. The spectrometer is moved up to the block and 5 minutes of data are collected at the point on the block that registers highest on a micro-R meter. Sensitivity is better than 1 pCi/g (0.037 Bq/g) for Co-60 and Eu-152, the prominent man-made activities observed. One-time calibration of the detector system is obtained from a sample of concrete, drilled with a hammer drill, counted in our low-background facility, and compared to crushed rock with known U, Th, and K activity. A simple relationship exists between the counts/minute observed in a characteristic gamma-ray peak and the activity in the block.     

Evaluation of Chinese medicinal herbs fingerprinting by HPLC-DAD for the detection of toxic aristolochic acids

Aristolochic acids are known to contribute to various renal disorders; therefore, expanding the availability of analytical methodology to detect these compounds is important in order to assess the quality of Chinese herbal medicines in which they can be found. Twelve medicinal herbal samples were procured from various sources and extracted in duplicate prior to a "fingerprint" analysis using conventional HPLC-DAD. Multivariate analysis was performed on the entire chromatographed fingerprints. The resulting output was a partial least-square discriminant analysis model, which was able to evaluate the potential presence of aristolochic acids I and II as well as providing an individual herbal "fingerprint". The results of this study provide evidence that the presence of aristolochic acids contained within certain herbal extractions could be detected using a simple method, although some limitations apply to this method for quality control, since newly detected samples for aristolochic acid (positives) will need further confirmation with purity checks or MS hyphenation.     

Colloidal interactions mediated by end-adsorbing polymer-like micelles

We derive a statistical mechanical model for colloidal interactions mediated by polymer-like micelles (PLMs) that adsorb at the colloid surface. The model considers the end-adsorption and reversible scission of ideal chains, and is based on experimentally measurable parameters relevant to PLMs. The model predicts interparticle attractions due to micellar bridging that are stronger and longer-range than those encountered in ordinary telechelic polymers. Mapping the analytical potential onto the more familiar Double Yukawa potential allows, for the first time, accurate, a priori prediction of suspension microstructure and phase behavior when compared to experimental data for model nanoparticles dispersed in wormlike micelles over a range of solution conditions.     

Relativistic contributions to single and double core electron ionization energies of noble gases

We have performed relativistic calculations of single and double core 1s hole states of the noble gas atoms in order to explore the relativistic corrections and their additivity to the ionization potentials. Our study unravels the interplay of progression of relaxation, dominating in the single and double ionization potentials of the light elements, versus relativistic one-electron effects and quantum electrodynamic effects, which dominate toward the heavy end. The degree of direct relative additivity of the relativistic corrections for the single electron ionization potentials to the double electron ionization potentials is found to gradually improve toward the heavy elements. The Dirac-Coulomb Hamiltonian is found to predict a scaling ratio of ～4 for the relaxation induced relativistic energies between double and single ionization. Z-scaling of the computed quantities were obtained by fitting to power law. The effects of nuclear size and form were also investigated and found to be small. The results indicate that accurate predictions of double core hole ionization potentials can now be made for elements across the full periodic table.