There exists a growing body of literature that correlates the fraction of ''special'' boundaries in a microstructure, as described by the Coincident Site Lattice Model, to properties such as corrosion resistance, intergranular stress corrosion cracking, creep, etc. Several studies suggest that the grain boundary character distribution (GBCD), which is defined in terms of the relative fractions of ''special'' and ''random'' grain boundaries, can be manipulated through thermomechanical processing. This investigation evaluates the influence of specific thermomechanical processing methods on the resulting GBCD in FCC materials such as oxygen-free electronic (ofe) copper and Inconel 600. We also demonstrate that the primary effect of thermomechanical processing is to reduce or break the connectivity of the random grain boundary network. Samples of ofe Cu were subjected to a minimum of three different deformation paths to evaluate the influence of deformation path on the resulting GBCD. These include: rolling to 82% reduction in thickness, compression to 82% strain, repeated compression to 20% strain followed by annealing. In addition, the influence of annealing temperature was probed by applying, for each of the processes, three different annealing temperatures of 400, 560, and 800 C. The observations obtained from automated electron backscatter diffraction (EBSD) characterization of the …

The authors have developed a x-ray microprobe in the energy region from 6 to 20 keV using undulator radiation and zone-plate optics for microfocusing-based techniques and applications at a beamline at the Advanced Photon Source (APS). The performance of the beamline was shown to meet the design objectives, including preservation of the source brilliance and coherence, selectable transverse coherence length and energy bandwidth, high angular stability, and harmonic suppression of the beam. These objectives were achieved by careful thermal management and use of a novel mirror and crystal monochromator cooling geometry. All beamline optical components are water cooled, and the x-ray beam in the experiment station is stable in beam intensity, energy, and position over many days with no active feedback. Using a double-crystal Si(111) monochromator, they have obtained a focal spot size (FWHM) of 0.15 {micro}m (v) x 1.0 {micro}m (h), and a photon flux of 4 x 10{sup 9} photons/sec at the focal spot, and thus a photon flux density gain of 15,000. A circular beam spot of 0.15 {micro}m in diameter can be achieved by reducing the horizontal source size using a white beam slit located 43.5 meters upstream of the zone plate, with an order of …

To search for candidates for 2-phonon vibrations, {sup 170}Er was studied with the inelastic neutron scattering reaction. The level scheme was extended using {gamma}{gamma} coincidences and excitation functions. Spins were deduced from angular distribution measurements, and the Doppler-shift attenuation method (DSAM) was used to determine lifetimes.

Many of the {sub 48}Cd nuclei are good examples of U(5) or vibrational nuclei. Like the {sub 50}Sn nuclei and others in the region, states exist which are interpreted in terms of the excitation of a pair of protons across the shell gap (intruders). The features of the comparatively well-understood Cd nuclei will be considered and compared with the{sub 52}Te nuclei where intruders have not been identified experimentally and problems exist with the U(5) interpretation.

The authors have examined extracellular iron-bearing precipitates resulting from the growth of Desulfovibrio desulfuricans in a basal medium with lactate as the carbon source and ferrous sulfate. Black precipitates were obtained when D. desulfuricans was grown with an excess of FeSO{sub 4}. When D. desulfuricans was grown under conditions with low amounts of FeSO{sub 4}, brown precipitates were obtained. The precipitates were characterized by iron K-edge XAFS (X-ray absorption fine structure), {sup 57}Fe Moessbauer-effect spectroscopy, and powder X-ray diffraction. Both were noncrystalline and nonmagnetic (at room temperature) solids containing high-spin Fe(III). The spectroscopic data for the black precipitates indicate the formation of an iron-sulfur phase with 6 nearest S neighbors about Fe at an average distance of 2.24(1) {angstrom}, whereas the brown precipitates are an iron-oxygen-sulfur phase with 6 nearest O neighbors about Fe at an average distance of 1.95(1) {angstrom}.

Fresnel zone plates have been highly successful as focusing and imaging optics for soft x-ray microscopes and microprobe. More recently, with the advent of third-generation high-energy storage rings, zone plates for the hard x-ray regime have been put to use as well. The performance of zone plates manufactured using a combination of electron-beam lithography and x-ray lithography is described.

The role of biotic Np(V) reduction is studied in light of its potential role in the environmental immobilization of this hazardous radionuclide. The speciation of Np in Desulfovibrio desulfuricans cultures is compared with Np speciation in the spent medium and in the uninoculated medium. Precipitates formed in all three samples. Optical spectroscopy and X-ray absorption near edge structure (XANES) were used to determine that Np(V) is almost quantitatively reduced in all three samples and that the precipitate is an amorphous Np(IV) species. These results demonstrate that the reduction of Np is independent of Desulfovibrio desulfuricans. The underlying chemistry associated with these results is discussed.

The resonance X-ray scattering from the unmodified, clean Pt(111) surface is compared to theoretically predicted scattering. Self-consistent real-space multiple-scattering approach is used to calculate the real and imaginary parts of the atomic platinum scattering factor. The experimentally observed near-edge fine structures of the surface-scattering and fluorescence intensities are well reproduced by the calculations. In addition, more details are presented on their previous study [Phys.Rev.Lett. 83, 552 (1999)] of electrochemically formed oxide monolayer on the Pt(111) surface.

Multivariate calibration techniques have been used in a wide variety of spectroscopic situations. In many of these situations spectral variation can be partitioned into meaningful classes. For example, suppose that multiple spectra are obtained from each of a number of different objects wherein the level of the analyte of interest varies within each object over time. In such situations the total spectral variation observed across all measurements has two distinct general sources of variation: intra-object and inter-object. One might want to develop a global multivariate calibration model that predicts the analyte of interest accurately both within and across objects, including new objects not involved in developing the calibration model. However, this goal might be hard to realize if the inter-object spectral variation is complex and difficult to model. If the intra-object spectral variation is consistent across objects, an effective alternative approach might be to develop a generic intra-object model that can be adapted to each object separately. This paper contains recommendations for experimental protocols and data analysis in such situations. The approach is illustrated with an example involving the noninvasive measurement of glucose using near-infrared reflectance spectroscopy. Extensions to calibration maintenance and calibration transfer are discussed.

At Lawrence Livermore National Laboratory, they have extensive experience with the design and development of miniature photonic systems which require novel packaging schemes. Over the years they have developed silicon micro-optical benches to serve as a stable platform for precision mounting of optical and electronic components. They have developed glass ball lenses that can be fabricated in-situ on the microbench substrate. They have modified commercially available molded plastic fiber ribbon connectors (MT) and added thin film multilayer semiconductor coatings to create potentially low-cost wavelength combiners and wavelength selective filters. They have fabricated both vertical-cavity and in-plane semiconductor lasers and amplifiers, and have packaged these and other components into several miniature photonics systems. For example, they have combined the silicon optical bench with standard electronic packaging techniques and the custom-made wavelength-selective filters to develop a four-wavelength wavelength-division-multiplexing transmitter module mounted in a standard 120-pin ceramic PGA package that couples light from several vertical-cavity-surface-emitting-laser arrays into one multimode fiber-ribbon array. The coupling loss can be as low as 2dB, and the transmitters can be operated at over 1.25 GHz. While these systems were not designed for biomedical or environmental applications, the concepts and techniques are general and widely applicable.