An electronic transition of iron in magnesiowuestite has been studied with synchrotron Moessbauer and X-ray emission spectroscopies under high pressures. Synchrotron Moessbauer studies show that the quadrupole splitting disappears and the isomer shift drops significantly across the spin-paring transition of iron in (Mg{sub 0.75},Fe{sub 0.25})O between 62 and 70 GPa, whereas X-ray emission spectroscopy of the Fe-K{sub {beta}} fluorescence lines in dilute (Mg{sub 0.95},Fe{sub 0.05})O also confirms that a high-spin to low-spin transition occurs between 46 GPa and 55 GPa. Based upon current results and percolation theory, we reexamine the high-pressure phase diagram of (Mg,Fe)O and find that iron-iron exchange interaction plays an important role in stabilizing the high-spin state of iron in FeO-rich (Mg,Fe)O.

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The RadPoleCam was developed to provide Department Of Energy (DOE) first responders the capability to assess the radiological and visual condition of remote or inaccessible locations. Real time gamma isotopic identification is provided to the first responder in the form of audio feedback (i.e. spoken through head phones) from a gamma detector mounted on a collapsible pole that can extend from 1 to 9 meters (6 to 29 feet). Simultaneously, selectable direct and side looking visual images are provided from the 5cm (2in) diameter, waterproof probe tip. The lightweight, self contained, ruggedized, system will provide a rapidly deployable field system for visual and radiological search and assessment of confined spaces and extended reach locations.

To provide a compact high-brightness heavy-ion beam source for Heavy Ion Fusion (HIF), we have been experimenting with merging multi-beamlets in an injector which uses an RF plasma source. An array of converging beamlets was used to produce a beam with the envelope radius, convergence, and ellipticity matched to an electrostatic quadrupole (ESQ) channel. Experimental results were in good quantitative agreement with simulation and have demonstrated the feasibility of this concept. The size of a driver-scale injector system using this approach will be several times smaller than one designed using traditional single large-aperture beams. The success of this experiment has possible significant economical and technical impacts on the architecture of HIF drivers.

Metal ions are essential for the folding of RNA into stable tertiary structures and for the catalytic activity of some RNA enzymes. To aid in the study of the roles of metal ions in RNA structural biology, we have created MeRNA (Metals in RNA), a comprehensive compilation of all metal binding sites identified in RNA three-dimensional structures available from the Protein Data Bank (PDB) and Nucleic Acid Database (NDB). Currently, our database contains information relating to binding of 9764 metal ions corresponding to 23 distinct elements; in 256 RNA structures. The metal ion locations were confirmed and ligands characterized using original literature references. MeRNA includes eight manually identified metal-ion binding motifs, which are described in the literature. MeRNA is searchable by PDB identifier, metal ion, method of structure determination, resolution and R-values for X-ray structure, and distance from metal to any RNA atom or to water. New structures with their respective binding motifs will be added to the database as they become available. The MeRNA database will further our understanding of the roles of metal ions in RNA folding and catalysis and have applications in structural and functional analysis, RNA design and engineering.

This article discusses a T-shaped three-coordinate nickel(l) carbonyl complex and the geometric preferences of three-coordinate d9 complexes.

The stability and NO{sub x} sensing performance of electrochemical cells of the structure Sr-doped LaCrO{sub 3-{delta}} (LSC)/yttria-stabilized zirconia (YSZ)/Pt are being investigated for use in NO{sub x} aftertreatment systems in diesel vehicles. Among the requirements for NO{sub x} sensor materials in these systems are stability and long lifetime (up to ten years) in the exhaust environment. In this study, cell aging effects were explored following extended exposure to a test environment of 10% O{sub 2} at operating temperatures of 600-700 C. The data show that aging results in changes in particle morphology, chemical composition and interfacial structure, Impedance spectroscopy indicated an initial increase in the cell resistance during the early stages of aging, which is correlated to densification of the Pt electrode. Also, x-ray photoelectron spectroscopy indicated formation of SrZrO{sub 2} solid state reaction product in the LSC, a process which is of finite duration. Subsequently, the overall cell resistance decreases with aging time due, in part, to roughening of YSZ-LSC interface, which improves interface adherence and enhances charge transfer kinetics at the O{sub 2}/YSZ/LSC triple phase boundary. This study constitutes a first step in the development of a basic understanding of aging phenomena in solid state electrochemical systems with …

A major concern in the design of thick-liquid protected inertial fusion reactors of all types is the dynamic response of the shielding liquid to the pulsed explosions. Induced liquid motion can stress and damage solid chamber structures such as the firstwall. In a z-pinch based inertial fusion (Z-IFE) reactor this issue becomes particularly critical due to the relatively large proposed target yields of several GJ. In this paper we summarize an analysis of the liquid response taking into account ablation of target facing surfaces, pocket venting, and neutron isochoric heating. The impact of varying several reactor parameters is also discussed.