The authors have shown that the hydroperoxide species in {gamma}-irradiated {sup 13}C-polyethylene can be directly observed by {sup 13}C MAS NMR spectroscopy. The experiment was performed without the need for special sample preparation such as chemical derivatization or dissolution. Annealing experiments were employed to study the thermal decomposition of the hydroperoxide species and to measure an activation energy of 98 kJ/mol. EPR spectroscopy suggests that residual polyenyl and alkylperoxy radicals are predominantly trapped in interracial or crystalline regions, while the peroxy radicals observed after UV-photolysis of hydroperoxides are in amorphous regions.

Artificial neural network (ANN) methods have been researched extensively within the nuclear community for applications in systems control, diagnostics, and signal processing. We consider here the use of multilayer perceptron ANNs as an alternative to finite-difference and finite-element methods for obtaining solutions to neutron diffusion problems. This work is based on a method proposed by van Milligen et. al. to obtain solutions of the differential equations arising in plasma physics applications. This ANN method has the potential advantage of yielding an accurate, differentiable approximation to the solution of diffusion problems at all points in the spatial domain.

Newsletter of the Texas Agricultural Extension Service discussing topics related to economic aspects of raising dairy cows, dairy production, and managing dairy operations.

Laser induced fluorescence was used to measure the spatially resolved CF, CF{sub 2} and SiF radical density in inductively driven discharges containing fluorocarbon gases. Measurements of the spatially resolved CF density were performed in C{sub 2}F{sub 6} and CHF{sub 3} containing discharges as functions of inductive power, pressure and bias condition on a silicon substrate. In addition, CF rotational temperatures were calculated, assuming saturated spectra. Measurements of the spatially resolved CF{sub 2} and SiF density were performed in C{sub 4}F{sub 8}, C{sub 2}F{sub 6} and CHF{sub 3} containing discharges as functions of inductive power, pressure and bias condition. SiF rotational temperatures were also estimated. As the induction coil power was increased, the SiF density in the center (r = 0 cm) increased while the CF{sub 2} density decreased and the CF density slightly decreased. In all cases, the radical density in the center of the glow increased with pressure changes from 5 to 30 mTorr while changes in the bias power had little influence on any of the measured radical densities. The spatial distribution of the CF and SiF density peaked in the center of the discharge. The CF{sub 2} density had a local maximum in the center of the …

The theoretical concepts of a chirally symmetric meson field theory are reviewed and an overview of the most relevant applications in nuclear physics is given. This includes a unified description of the vacuum properties of hadrons, finite nuclei and hot, dense and strange nuclear matter in an extended chiral SU(3){sub L}/SU(3){sub R} {sigma}-{omega} model.

The objective of this calculation is to compare several creep rupture correlations for use in calculating creep strain accrued by the Zircaloy cladding of spent nuclear fuel when it has been emplaced in the repository. These correlations are used to calculate creep strain values that are then compared to a large set of experimentally measured creep strain data, taken from four different research articles, making it possible to determine the best fitting correlation. The scope of the calculation extends to six different creep rupture correlations.

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Laboratory data acquired from two multistage, triaxial compression creep experiments are presented for bedded salt. The experiments were conducted to study the effect of pore pressure changes on the accumulation of damage (dilatant volumetric strain). The first experiment comprised five constant total stress tests in which the internal pore pressure was incremented during successive stages, while the externally applied axial and radial stresses were maintained constant. The second experiment comprised three constant effective stress tests in which the pore pressure and the externally applied axial and radial stresses were increased in equal increments in successive stages. Volumetric strain rates were determined both before and after the pore pressure changes were made in all tests. The data suggest pore pressure changes made during the constant total stress tests have a greater effect on salt dilation than do changes made during the constant effective stress tests.

Results are reported for the passivation of interface states near the conduction band edge in SiO{sub 2}/SiC MOS capacitors using post-oxidation anneals in nitric oxide, ammonia and forming gas (N{sub 2}5%H{sub 2}). Anneals in nitric oxide and ammonia reduce the interface state density significantly for 4H-SiC, while forming gas anneals are largely ineffective. Results suggest that interface states in SiO{sub 2}/SiC and SiO{sub 2}/SiC have different origins, and a model is described for interface state passivation by nitrogen in the SiO{sub 2}/SiC system. The peak inversion channel mobility measured for lateral 4H-SiC MOSFETs increases following NO passivation.

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Since the discovery of surfactant-templated silica mesophases, the development of organic modification schemes to impart functionality to the pore surfaces has received much attention. Most recently, using the general class of compounds referred to as bridged silsesquioxanes (RO){sub 3}Si-R{prime}-Si(OR){sub 3} (Scheme 1), three research groups have reported the formation of a new class of poly(bridgedsilsesquioxane) mesophases BSQMs with integral organic functionality. In contrast to previous hybrid mesophases where organic ligands or molecules are situated on pore surfaces, this class of materials necessarily incorporates the organic constituents into the framework as molecularly dispersed bridging ligands. Although it is anticipated that this new mesostructural organization should result in synergistic properties derived from the molecular scale mixing of the inorganic and organic components, few properties of BSQMs have been measured. In addition samples prepared to date have been in the form of granular precipitates, precluding their use in applications like membranes, fluidics, and low k dielectric films needed for all foreseeable future generations of microelectronics.

Under this CRADA, Berkeley Lab and the industry partner, General Atomics (GA), have cooperatively developed hadron therapy technologies for commercialization. Specifically, Berkeley Lab and GA jointly developed beam transport systems to bring the extracted protons from the accelerator to the treatment rooms, rotating gantries to aim the treatment beams precisely into patients from any angle, and patient positioners to align the patient accurately relative to the treatment beams. We have also jointly developed a patient treatment delivery system that controls the radiation doses in the patient, and hardware to improve the accelerator performances, including a radio-frequency ion source and its low-energy beam transport (LEBT) system. This project facilitated the commercialization of the DOE-developed technologies in hadron therapy by the private sector in order to improve the quality of life of the nation.

A brief review is given of recent progress in fabrication of high voltage GaN and AlGaN rectifiers. GaN/AlGaN heterojunction bipolar transistors and GaN metal-oxide semiconductor field effect transistors. Improvements in epitaxial layer quality and in fabrication techniques have led to significant advances in device performance.

A major cause of failures in heat exchangers and steam generators in nuclear power plants is degradation of the tubes within them. The tube failure is often caused by the development of cracks that begin on the outer surface of the tube and propagate both inwards and laterally. A new technique will be described for detection of defects using a continuous-wave radar device within metal tubing. The technique is 100% volumetric, and may find smaller defects, find them more rapidly, and find them less expensively than present methods. Because this project was started only recently, there is no demonstrated performance to report so far. However, the basic engineering concepts will be presented together with a description of the milestone tasks and dates.

A hybrid of a microfabricated planar preconcentrator and a four element chemiresistor array chip has been fabricated and the performance as a chemical sensor system has been demonstrated. The close proximity of the chemiresistor sensor to the preconcentrator absorbent layer allows for fast transfer of the preconcentrated molecules during the heating and resorption step. The hybrid can be used in a conventional flow sampling system for detection of low concentrations of analyte molecules or in a pumpless/valveless mode with a grooved lid to confine the desorption plume from the preconcentrator during heating.

The authors summarize the methods used for simulation of polarization effects in the front end of a possible neutrino factory. They first discuss the helicity of muons in the pion decay process. They find that, neglecting acceptance considerations, the average helicity asymptotically approaches a magnitude of 0.185 at large pion momenta. Next they describe the methods used for tracking the spin through the complicated electromagnetic field configurations in the front end of the neutrino factory, including rf phase rotation and ionization cooling channels. Various depolarizing effects in matter are then considered, including multiple Coulomb scattering and elastic scattering from atomic electrons. Finally, they include all these effects in a simulation of a 480 m long, double phase rotation front end scenario.

A letter report issued by the General Accounting Office with an abstract that begins "Pursuant to a congressional request, GAO provided information on the Federal Aviation Administration's (FAA) new navigation system, focusing on whether: (1) the Department of Defense's (DOD) current Global Positioning System (GPS) or its planned improvements for GPS can meet FAA's navigation requirements; (2) the benefits of FAA's chosen approach to an augmented system outweigh the cost of this system; and (3) other technologies are available to meet FAA's requirements and users' needs for a new navigation system."

The authors investigated the late-time (asymptotic) behavior of tracer test breakthrough curves (BTCs) with rate-limited mass transfer (e.g., in dual or multi-porosity systems) and found that the late-time concentration, c, is given by the simple expression: c = t{sub ad} (c{sub 0}g {minus} m{sub 0}{partial_derivative}g/{partial_derivative}t), for t >> t{sub ad} and t{sub a} >> t{sub ad} where t{sub ad} is the advection time, c{sub 0} is the initial concentration in the medium, m{sub 0} is the 0th moment of the injection pulse; and t{sub a} is the mean residence time in the immobile domain (i.e., the characteristic mass transfer time). The function g is proportional to the residence time distribution in the immobile domain, the authors tabulate g for many geometries, including several distributed (multirate) models of mass transfer. Using this expression they examine the behavior of late-time concentration for a number of mass transfer models. One key results is that if rate-limited mass transfer causes the BTC to behave as a power-law at late-time (i.e., c {approximately} t{sup {minus}k}), then the underlying density function of rate coefficients must also be a power-law with the form a{sup k{minus}}, as a {r_arrow}0. This is true for both density functions of first-order …

The National Spherical Torus Experiment (NSTX) is a proof-of-principle scale device whose mission is to establish the physics basis of low aspect configurations most notably in the areas of plasma stability, transport and non-inductive current drive. The first series of physics experiments was conducted during the period from Sept. 1999 through Jan. 2000. Among the first experiments was a study to map out and characterize the operational density and q-limits. Density limits have typically been associated with enhanced radiated power due to overfuelling or impurity influx, although ion neoclassical transport may impose a density limit at very high densities in ohmic, gas-fueled plasmas. q-limits have typically been manifestations of destabilization of m=2/n=1 kink or tearing modes that lead to a sudden discharge termination.

Recently, an EBSD system was developed that uses a 1024 x 1024 CCD camera coupled to a thin phosphor. This camera has been shown to produce excellent EBSD patterns. In this system, crystallographic information is determined from the EBSD pattern and coupled with the elemental information from energy or wavelength dispersive x-ray spectrometry. Identification of the crystalline phase of a sample is then made through a link to a commercial diffraction database. To date, this system has been applied almost exclusively to conventional, bulk samples that have been polished to a flat surface. In this investigation, the authors report on the application of the EBSD system to the phase identification analysis (PIA) of individual micrometer and submicrometer particles rather than flat surfaces.

The authors use low energy electron microscopy to identify a correlation between the growth shape of three-dimensional Pb islands on Cu(100)and the domain structure of the underlying Pb overlayer. Deposition of 0.6 monolayer Pb on Cu(100) produces a compressed c(2x2) overlayer, designated c(5{radical}2x{radical}2)R45{degree}, with periodic rows of anti-phase boundaries. They found that heating the surface to temperatures above 100 C coarsens the orientational domains of this structure to sizes that are easily resolved in the low energy electron microscope. Three-dimensional Pb islands, grown on the coarsened domains, are found to be asymmetric with orientations that correlate with the domain structure. Once nucleated with a preferred growth orientation, islands continue to grow with the same preferred orientation, even across domain boundaries.

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Highly concentrated, aqueous mullite slurries were characterized and stabilized at solids concentrations as high as 60 vol% using less than 2 vol% of an organic polyelectrolyte dispersant. The maximum slurry concentration (60 vol%) is within 3 vol% of the maximum consolidated density of the slurry. The slurries were subsequently cast into parts by a solid freeform fabrication technique termed robocasting and characterized. Sedimentation analysis and viscometry provided the means of slurry characterization, while knowledge of polyelectrolyte and interparticle forces was used to interpret the sedimentation and viscometry data. Through proper control of slurry conditions, pseudoplastic mullite slurries were fabricated for use in the robocasting process. The slurries were robocast at 52 vol% solids and subsequently yielded a green density of 55 vol%. Fired densities of the robocasted slurries were high, with mullite >96% dense at 1,650 C.

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