Interpretation of ultrasonic inspection data from stainless steel welds is difficult because the signal-to-noise ratio is very low. The three main reasons for this are the granular structure of the weld, the high attenuation of stainless steel, and electronic noise. Averaging in time at the same position in space reduces electronic noise, but does not reduce ultrasonic noise from grain boundary scattering. Averaging wave-forms from different spatial positions helps reduce grain noise, but desired signals can destructively interfere if they shift in time. If the defect geometry is known, the ultrasonic waveforms can be shifted before averaging, ensuring signal reinforcement. The simplest geometry results in a linear time shift. An averaging algorithm has been developed which finds the optimum shift. This algorithm computes the averaged, or composite waveform as a function of the time shift. The optimum occurs when signals from a reflector become aligned in time, producing a large amplitude composite waveform. This algorithm works very well, but requires significant computer time and storage. This paper discusses this linear shift averaging algorithm, and considers an implementation using frequency domain techniques. Also, data from several weld defects are presented and analyzed.

Human sperm tests provide a direct means of assessing chemically induced spermatogenic dysfunction in man. Available tests include sperm count, motility, morphology (seminal cytology), and Y-body analyses. Over 70 different human exposures have been monitored in various groups of exposed men. The majority of exposures studied showed a significant change from control in one or more sperm tests. When carefully controlled, the sperm morphology test is statistically the most sensitive of these human sperm tests. Several sperm tests have been developed in nonhuman mammals for the study of chemical spermatotoxins. The sperm morphology test in mice has been the most widely used. Results with this test seem to be related to germ-cell mutagenicity. In general, animal sperm tests should play an important role in the identification and assessment of potential human reproductive hazards. Exposure to spermatotoxins may lead to infertility, and more importantly, to heritable genetic damage. While there are considerable animal and human data suggesting that sperm tests may be used to detect agents causing infertility, the extent to which these tests detect heritable genetic damage remains unclear. (ERB)

MERCURY is a modern, parallel, general-purpose Monte Carlo code being developed at the Lawrence Livermore National Laboratory. Recently, a radiographic capability has been added. MERCURY can create a source of diagnostic, virtual particles that are aimed at pixels in an image tally. This new feature is compared to the radiography code, HADES, for verification and timing. Comparisons for accuracy were made using the French Test Object and for timing were made by tracking through an unstructured mesh. In addition, self consistency tests were run in MERCURY for the British Test Object and scattering test problem. MERCURY and HADES were found to agree to the precision of the input data. HADES appears to run around eight times faster than the MERCURY in the timing study. Profiling the MERCURY code has turned up several differences in the algorithms which account for this. These differences will be addressed in a future release of MERCURY.

We discuss the description of the proton structure function within the dipole factorization framework. We parameterize the forward dipole amplitude to account for saturation as predicted by the small-x QCD evolution equations. Contrarily to previous models, the saturation scale does not decrease when taking heavy quarks into account. We show that the same dipole amplitude also allows to reproduce diffractive data and exclusive vector meson production.

In magnetic cataclysmic variables (CVs) the primary is a highly magnetized white dwarf (WD) whose field controls the accretion flow close to the WD, leading to a shock and accretion column that radiate chiefly in X-rays. We present preliminary results from a 500 ks Chandra HETG observation of the brightest magnetic CV EX Hya. From the observational dataset we are able to measure the temperature and density at different points of the cooling accretion column using sensitive line ratios. We also construct line-based light curves to search for rotational modulation of the X-ray emission.

The apolipoprotein A5 gene (APOA5) is a key player in determining triglyceride concentrations in humans and mice. Since diabetes is often associated with hypertriglyceridemia, this study explores whether APOA5 gene expression is regulated by alteration in glucose homeostasis and the related pathways. D-glucose activates APOA5 gene expression in a time- and dose-dependent manner in hepatocytes, and the glycolytic pathway involved was determined using D-glucose analogs and metabolites. Together, transient transfections, electrophoretic mobility shift assays and chromatin immunoprecipitation assays show that this regulation occurs at the transcriptional level through an increase of USF1/2 binding to an E-box in the APOA5 promoter. We show that this phenomenon is not due to an increase of mRNA or protein expression levels of USF. Using protein phosphatases 1 and 2A inhibitor, we demonstrate that D-glucose regulates APOA5 gene via a dephosphorylation mechanism, thereby resulting in an enhanced USF1/2-promoter binding. Last, subsequent suppressions of USF1/2 and phosphatases mRNA through siRNA gene silencing abolished the regulation. We demonstrate that APOA5 gene is up regulated by D-glucose and USF through phosphatase activation. These findings may provide a new cross talk between glucose and lipid metabolism.

We illustrate how the midpoint and iterative cone (with progressive removal) algorithms fail to satisfy the fundamental requirements of infrared and collinear safety, causing divergences in the perturbative expansion. We introduce SISCone and the anti-k{sub t} algorithms as respective replacements that do not have those failures without any cost at the experimental level.

Currently two simple theories are heavily used in laser-fusion research: the Thomas-Fermi-Dirac statistical model, and an atomic ionization model based on screened hydrogen like energy levels. Recent improvements in these theories are summarized. We show representation calculations of thermodynamic properties, ionization, x-ray emission rates and fast-ion stopping powers, and give a brief sketch of the major unresolved scientific questions.

Ultra-high-energy cosmic rays are usually associated with an extragalactic origin. Active galactic nuclei are an unlikely source because of photon drag. Here the possibility of supernova events are considered. The time spread of arrival of 10/sup 20/ eV protons is 100 to 400 years at 10 to 20 kpc and the angular spread is +-15 to +-30/sup 0/ depending upon the Galactic field configuration. The time spread is sufficient to include several to a dozen type I SN. This is enough events and angular spread to include the observed data. The concentration of the observed events at the galactic poles is contradictory. The flux is reasonable if the observed flux and slope at 10/sup 12/ to 10/sup 15/ eV is characteristic of the source(s) and confined at this energy for roughly 100 traversals of the Galaxy, or 3 x 10/sup 6/ years.

The objectives are to summarize our knowledge of the way in which plutonium and some other transuranium elements migrate through ecosystems; to consider how the physiochemical state of these elements and the biological systems through which they pass may influence this movement; and to put into perspective the risks of serious illness in man resulting from his exposure to these elements in the environment.

The usual assumption of the acceleration of ultra high energy cosmic rays, greater than or equal to 10/sup 18/ eV in quasars, Seyfert galaxies and other active galactic nuclei is challenged on the basis of the photon interactions with the accelerated nucleons. This is similar to the effect of the black body radiation on particles > 10/sup 20/ eV for times of the age of the universe except that the photon spectrum is harder and the energy density greater by approx. = 10/sup 15/. Hence, a single traversal, radial or circumferential, of radiation whose energy density is no greater than the emitted flux will damp an ultra high energy. Hence, it is unlikely that any reasonable configuration of acceleration can void disastrous photon energy loss. A different site for ultra high energy cosmic ray acceleration must be found.

The tandem mirror device (TMX) exhibits gross stability to both MHD and microinstability modes. The end-cell plasmas provide the tandem with average minimum-B stability, while the efflux of plasma from the central cell maintains the end cells (plugs) at marginal stability to loss cone modes. For some operating conditions, a residual level of plug ion cyclotron fluctuations is detected. These oscillations dominate the fluctuation frequency spectra in both the plugs and the central cell. The presence of plug ion cyclotron fluctuations in the central cell leads to resonance heating of some of the central cell ions. This heating degrades the confinement of the central cell ions; thereby increasing the amount of warm plasma stream flowing through the plugs.

Quality systems development in environmental measurements for compliance with regulatory requirements for nuclear and other contaminants in the environment is one of the major challenges in current technology disciplines. Efforts to fulfill the mission and objectives of funded projects will not be successful on a timely and cost-effective schedule without adequate plans and credible action for the protection of workers, facilities, and the public in environment, safety, and health aspects. This can be accomplished through quality assurance planning and implementation of an effective, controlled environmental measurements program.

A non-destructive analysis technique using a portable, electric ion-tube neutron source (INS) and gamma ray detector has been used to identify the key constituent elements in a number of sealed munitions, and from the elemental makeup, infer the types of agent within each. The high energy (14 MeV) and pulsed character of the neutron flux from an INS provide a method of measuring, quantitatively, the oxygen, carbon, and fluorine content of materials in closed containers, as well as the other constituents that can be measured with low-energy neutron probes. The broad range of elements that can be quantitatively measured with INS-based instruments provides a capability of verifying common munition fills; it provides the greatest specificity of any portable neutron-based technique for determining the full matrix of chemical elements in completely unrestricted sample scenarios. The specific capability of quantifying the carbon and oxygen content of materials should lead to a fast screening technique which, can discriminate very quickly between high-explosive and chemical agent-filled containers.

The effect of preparation conditions on the structural and optical properties of silicon nanoparticles is investigated. Nanoscale reconstructions, unique to curved nanosurfaces, are presented for silicon nanocrystals and shown to have lower energy and larger optical gaps than bulk-derived structures. We find that high-temperature synthesis processes can produce metastable non-crystalline nanostructures with different core structures than bulk-derived crystalline clusters. The type of core structure that forms from a given synthesis process may depend on the passivation mechanism and time scale. The effect of oxygen on the optical of different types of silicon structures is calculated. In contrast to the behavior of bulk-like nanostructures, for non-crystalline and reconstructed crystalline structures surface oxygen atoms do not decrease the gap. In some cases, the presence of oxygen atoms at the nanocluster surface can significantly increase the optical absorption gap, due to decreased angular distortion of the silicon bonds. The relationship between strain and the optical gap in silicon nanoclusters is discussed.

Here we review experimental data and models of the ignition of aluminum (Al) particles and clouds in explosion fields. The review considers: (i) ignition temperatures measured for single Al particles in torch experiments; (ii) thermal explosion models of the ignition of single Al particles; and (iii) the unsteady ignition Al particles clouds in reflected shock environments. These are used to develop an empirical ignition model appropriate for numerical simulations of Al particle combustion in shock dispersed fuel explosions.

A heterogeneous continuum model is proposed to describe the dispersion of a dense Aluminum particle cloud in an explosion. Let {alpha}{sub 1} denote the volume fraction occupied by the gas and {alpha}{sub 2} the fraction occupied by the solid, satisfying the volume conservation relation: {alpha}{sub 1} + {alpha}{sub 2} = 1. When the particle phase occupies a non-negligible volume fraction (i.e., {alpha}{sub 2} > 0), additional terms, proportional to {alpha}{sub 2}, appear in the conservation laws for two-phase flows. These include: (i) a particle pressure (due to particle collisions), (ii) a corresponding sound speed (which produces real eigenvalues for the particle phase system), (iii) an Archimedes force induced on the particle phase (by the gas pressure gradient), and (iv) multi-particle drag effects (which enhance the momentum coupling between phases). These effects modify the accelerations and energy distributions in the phases; we call this the Dense Heterogeneous Continuum Model. A characteristics analysis of the Model equations indicates that the system is hyperbolic with real eigenvalues for the gas phase: {l_brace}v{sub 1}, v{sub 1} {+-} {alpha}{sub 1}{r_brace} and for the 'particle gas' phase: {l_brace}v{sub 2}, v{sub 2} {+-}{alpha}{sub 2}{r_brace} and the particles: {l_brace}v{sub 2}{r_brace}, where v{sub i} and {alpha}{sub i} denote the …

We report on the mineralogy, petrology, chemistry, oxygen isotopes, {sup 26}Al-{sup 26}Mg and {sup 36}Cl-{sup 36}S isotope systematics of the Allende chondrule Al3509 discovered and described by [1] and [2]. This spherical object ({approx}1cm {phi}) contains {approx}10% Na and 1% Cl, and nearly pure {sup 129}Xe [({sup 129}Xe/{sup 127}I) = 1.1 x 10{sup -4} (3)]. This high enrichment in halogens makes it of interest in searching for radiogenic {sup 36}S from {sup 36}Cl (t{sub 1/2} {approx} 0.3 Ma) decay. While there is strong evidence for the presence of {sup 36}Cl in sodalite and wadalite in CV CAIs [4,5], some sodalites show no evidence for excesses of {sup 36}S ({sup 36}S*). In contrast, high inferred initial {sup 36}Cl/{sup 35}Cl = 2 x 10{sup -5} has been found in wadalite from the Allende CAI AJEF [5]. The observed {sup 36}S excesses in sodalite are not correlated with radiogenic {sup 26}Mg, decay product of {sup 26}Al (t{sub 1/2} {approx} 0.72 Ma) [4]. From the inferred initial {sup 36}Cl/{sup 35}Cl ratios and consideration of both AGB and SNe stellar sources, {sup 36}Cl must be the product of charged particle irradiation within the early solar system. However, neither the specific nuclear production mechanism nor the …

In April 1974, the United States Energy Research and Development Administration (ERDA) authorized General Atomic Company, General Electric Company, and Westinghouse Astronuclear Laboratory to assess the available technology for producing process heat utilizing a very high temperature nuclear reactor (VHTR). The VHTR is defined as a gas-cooled graphite-moderated reactor. Oak Ridge National Laboratory has been given a lead role in evaluating the VHTR reactor studies and potential applications of the VHTR. Process temperatures up to the 760 to 871/sup 0/C range appear to be achievable with near-term technology. The major development considerations are high temperature materials, the safety questions (especially regarding the need for an intermediate heat exchanger) and the process heat exchanger. The potential advantages of the VHTR over competing fossil energy sources are conservation of fossil fuels and reduced atmospheric impacts. Costs are developed for nuclear process heat supplied from a 3000-MW(th) VHTR. The range of cost in process applications is competitive with current fossil fuel alternatives.

A Material Handling System Simulator (MHSS) program is described that provides specialized functional blocks for modeling and simulation of nuclear material handling systems. Models of nuclear fuel fabrication plants may be built using functional blocks that simulate material receiving, storage, transport, inventory, processing, and shipping operations as well as the control and reporting tasks of operators or on-line computers. Blocks are also provided that allow the user to observe and gather statistical information on the dynamic behavior of simulated plants over single or replicated runs. Although it is currently being developed for the nuclear materials handling application, MHSS can be adapted to other industries in which material accountability is important. In this paper, emphasis is on the simulation methodology of the MHSS program with application to the nuclear material safeguards problem. (auth)

We report on a reflection microscope that operates at 13.2-nm wavelength with a spatial resolution of 55{+-}3 nm. The microscope uses a table-top EUV laser to acquire images of photolithography masks in 20 seconds.

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Among its many unique and precedent-setting provisions, the Chemical Weapons Convention (CWC) includes important requirements for States Parties to protect the public safety and the environment in the course of carrying out the treaty. These obligations will apply to the destruction of chemical weapons, of former chemical weapons production facilities, and to other activities under the Convention such as the verification scheme. This morning, I will briefly discuss the Convention`s safety and environmental obligations, concentrating on their effects in this country as the United States chemical weapons stockpile is destroyed.

Analytical and finite element method (FEM) simulations of creep in idealized ductile-phase toughened intermetallic composites are described. For these strong-matrix materials, the two types of analyses predict similar time-independent composite creep rates if each phase individually exhibits only steady-state creep. The composite creep rate becomes increasingly higher than that of the monolithic intermetallic as the stress exponent of the intermetallic and the volume fraction and creep rate of the ductile phase increase. FEM analysis shows that the shape of the ductile phase does not affect the creep rate but may affect the internal stress and strain distributions, and thus damage accumulation rates. If primary creep occurs in one or both of the individual phases, the composite also exhibits primary creep. In this case, there can be significant deviations in the creep curves computed by the analytical and FEM models. The model predictions are compared with data for the Nb5Si3/Nb system.