Showing papers by "Pacific Northwest National Laboratory published in 1998"

Radiation effects in crystalline ceramics for the immobilization of high-level nuclear waste and plutonium

Abstract: This review provides a comprehensive evaluation of the state-of-knowledge of radiation effects in crystalline ceramics that may be used for the immobilization of high-level nuclear waste and plutonium. The current understanding of radiation damage processes, defect generation, microstructure development, theoretical methods, and experimental methods are reviewed. Fundamental scientific and technological issues that offer opportunities for research are identified. The most important issue is the need for an understanding of the radiation-induced structural changes at the atomic, microscopic, and macroscopic levels, and the effect of these changes on the release rates of radionuclides during corrosion.

Optical studies of single molecules at room temperature

Abstract: Recent developments in optical studies of single molecules at room temperature are reviewed, with an emphasis on the underlying principles and the potential of single-molecule experiments. Examples of single-molecule studies are given, including photophysics and photochemistry pertinent to single-molecule measurements, spectral fluctuations, Raman spectroscopy, diffusional motions, conformational dynamics, fluorescence resonant energy transfer, exciton dynamics, and enzymatic turnovers. These studies illustrate the information obtainable with the single-molecule approach that is hidden in ensemble-averaged measurements.

Unexpectedly high concentrations of molecular chlorine in coastal air

Abstract: The fate of many atmospheric trace species, including pollutants such as nitrogen oxides and some volatile organic compounds, is controlled by oxidation reactions In the daytime troposphere, these reactions are dominated by photochemically produced OH radicals; at night and in polluted environments, NO3 radicals are an important oxidant1 Ozone can contribute to the oxidation of atmospheric species during both day and night1 In recent years, laboratory investigations2,3,4, modelling studies5,6,7, measured Cl deficits in marine aerosols8 and species-nonspecific observations9,10,11 of gaseous inorganic chlorine compounds other than HCl have suggested that reactive halogen species may contribute significantly to—or even locally dominate—the oxidative capacity of the lower marine troposphere Here we report night-time observations of molecular chlorine concentrations at a North American coastal site during onshore wind flow conditions that cannot be explained using known chlorine chemistry The measured Cl2 mixing ratios range from <10 to 150 parts per 1012 (ppt), exceeding those predicted5 for marine air by more than an order of magnitude Using the observed chlorine concentrations and a simple photochemical box model, we estimate that a hitherto unrecognized chlorine source must exist that produces up to 330 ppt Cl2 per day The model also indicates that early-morning photolysis of molecular chlorine can yield sufficiently high concentrations of chlorine atoms to render the oxidation of common gaseous compounds by this species 100 times faster than the analogous oxidation reactions involving the OH radical, thus emphasizing the locally significant effect of chlorine atoms on the concentrations and lifetimes of atmospheric trace species in both the remote marine boundary layer and coastal urban areas

From molecules to materials : current trends and future directions

Abstract: The development, characterization, and exploitation of novel materials based on the assembly of molecular components is an exceptionally active and rapidly expanding field. For this reason, the topic of molecule-based materials (MBMs) was chosen as the subject of a workshop sponsored by the Chemical Sciences Division of the United States Department of Energy. The purpose of the workshop was to review and discuss the diverse research trajectories in the field from a chemical perspective, and to focus on the critical elements that are likely to be essential for rapid progress. The MBMs discussed encompass a diverse set of compositions and structures, including clusters, supramolecular assemblies, and assemblies incorporating biomolecule-based components. A full range of potentially interesting materials properties, including electronic, magnetic, optical, structural, mechanical, and chemical characteristics were considered. Key themes of the workshop included synthesis of novel components, structural control, characterization of structure and properties, and the development of underlying principles and models. MBMs, defined as auseful substances prepared from molecules or molecular ions that maintain aspects of the parent molecular frameworko are of special significance because of the capacity for diversity in composition, structure, and properties, both chemical and physical. Key attributes are the ability in MBMs to access the additional dimension of multiple length scales and available structural complexity via organic chemistry synthetic methodologies and the innovative assembly of such diverse components. The interaction among the assembled components can thus lead to unique behavior. A consequence of the complexity is the need for a multiplicity of both existing and new tools for materials synthesis, assembly, characterization, and

International Equity and Differentiation in Global Warming Policy

Abstract: ne of the major obstacles to reaching a comprehensive agreement on global warming is the setting of greenhouse gas emission reduction targets for individual countries. Long-standing tensions between industrialized and developing countries have raised the issue of equity in burden-sharing. Moreover, individual industrialized nations have pleaded special circumstances and have sought differentiation in their obligations. This paper analyzes alternative rules for distributing tradable carbon dioxide emissions permits. A non-linear programming model, which distinguishes between allocation-based and outcome-based rules, is used to analyze the relative welfare outcomes. The model is applied to the world body of nations and yields several important policy implications.

Hybrid Mesoporous Materials with Functionalized Monolayers

Abstract: Mesoporous materials have great potential for environmental and industrial processes, but many applications require the materials to exhibit specific surface chemistry and binding sites. A new approach has been developed so that organized functional monolayers are covalently bound to mesoporous supports. The functionalized hybrid materials show exceptional selectivity and capacity for removing heavy metals from waste streams. Tailored hybrid materials have also shown potential to selectively bind anions and radionuclides. Rational design of the surface properties of mesoporous materials will lead to more sophisticated functional composites.

Bacterial reduction of crystalline Fe (super 3+) oxides in single phase suspensions and subsurface materials

Abstract: Microbiologic reduction of synthetic and geologic Fe{sup 3+} oxides associated with four Pleistocene-age, Atlantic coastal plain sediments was investigated using a dissimilatory Fe reducing bacterium (Shewanella putrefaciens, strain CN32) in bicarbonate buffer. Experiments investigated whether phosphate and anthraquinone-2,6-disulfonate, (AQDS, a humic acid analogue) influenced the extent of crystalline Fe{sup 3+} oxide bioreduction and whether crystalline Fe{sup 3+} oxides in geologic materials are more or less reducible than comparable synthetic phases. Anaerobic incubations (10{sup 8} organisms/mL) were performed both with and without PO{sub 4} and AQDS that functions as an electron repository and shuttle. The production of Fe{sup 2+} (solid and aqueous) was followed with time, as was mineralogy by X-ray diffraction. The synthetic oxides were reduced in a qualitative trend consistent with their surface area and free energy: hydrous ferric oxide (HFO) > goethite > hematite. Bacterial reduction of the crystalline oxides was incomplete in spite of excess electron donor. Biogenic formation of vivianite [Fe{sub 3}(PO{sub 4}){sub 2}{center_dot}8H{sub 2}O] and siderite (FeCO{sub 3}) was observed; the conditions of their formation was consistent with their solubility. The geologic Fe{sup 3+} oxides showed a large range in reducibility, approaching 100% in some materials. The natural oxides were equally or more reducible thanmore » their synthetic counterparts, in spite of association with non-reducible mineral phases (e.g., kaolinite). The reducibility of the synthetic and geologic oxides was weakly effected by PO{sub 4}, but was accelerated by AQDS. CN32 produced the hydroquinone form of AQDS (AHDS), that, in turn, had thermodynamic power to reduce the Fe{sup 3+} oxides. As a chemical reductant, it could reach physical regions of the oxide not accessible by the organism. Electron microscopy showed that crystallite size was not the primary factor that caused differences in reducibility between natural and synthetic crystalline Fe{sup 3+} oxide phases. Crystalline disorder and microheterogeneities may be more important.« less

Chemically durable iron phosphate glass wasteforms

Abstract: Up to 40 wt% of a simulated high level waste, whose major components were 54.6 wt% Na2O, 14.9 wt% P2O5 and 8.3 wt% Fe2O3, was successfully vitrified into iron phosphate wasteforms whose chemical durability was equivalent to that of borosilicate glass wasteforms. Because of their high fluidity, the iron phosphate wasteforms could be melted in as little as 30 min at temperatures between 1015°C and 1200°C. The addition of 3–7 wt% CaF2 to the batch decreased the melting time and temperature, by as much as 100°C, and improved the chemical durability, especially for crystallized iron phosphate wasteforms. Iron phosphate wasteforms are concluded to be a practical alternative for vitrifying those nuclear wastes not well suited for borosilicate glasses.

Turn-key Raman lidar for profiling atmospheric water vapor, clouds, and aerosols

Abstract: We describe an operational, self-contained, fully autonomous Raman lidar system that has been developed for unattended, around-the-clock atmospheric profiling of water vapor, aerosols, and clouds During a 1996 three-week intensive observational period, the system operated during all periods of good weather (339 out of 504 h), including one continuous five-day period The system is based on a dual-field-of-view design that provides excellent daytime capability without sacrificing nighttime performance It is fully computer automated and runs unattended following a simple, brief (~5-min) start-up period We discuss the theory and design of the system and present detailed analyses of the derivation of water-vapor profiles from the lidar measurements

Modeling Multispecies Reactive Transport in Ground Water

Abstract: In this paper, the details of RT3D, a general purpose, multispecies, reactive transport code, are presented. The code uses MODFLOW to simulate flow and several MT3D sub-programs to simulate advection and dispersion. A set of reaction modules were developed and incorporated into RT3D to simulate various types of multispecies reactive transport. This new computer model can be used for analyzing different types of subsurface contaminant reactions, microbial metabolisms, and microbial transport kinetics. Details of the model and numerical solution procedure are presented. The numerical formulation of the code is general enough to allow description of any type of reaction with any number of mobile/immobile species. Several example problems are presented to test the performance of the code, and to illustrate its features. The presented numerical model is shown to be a useful tool for analyzing different types of subsurface bioremediation systems. Prediction based on this model can be used for screening remediation alternatives including natural attenuation and/or for forecasting contaminant exposure levels and environmental risks at sensitive, downgradient receptors.

Redd Site Selection and Spawning Habitat Use by Fall Chinook Salmon: The Importance of Geomorphic Features in Large Rivers

Abstract: ) spawning habitat. Information exists on the microhabitat characteristics that define suitable salmon spawning habitat. However, traditional spawning habitat models that use these characteristics to predict available spawning habitat are restricted because they can not account for the heterogeneous nature of rivers. We present a conceptual spawning habitat model for fall chinook salmon that describes how geomorphic features of river channels create hydraulic processes, including hyporheic flows, that influence where salmon spawn in unconstrained reaches of large mainstem alluvial rivers. Two case studies based on empirical data from fall chinook salmon spawning areas in the Hanford Reach of the Columbia River are presented to illustrate important aspects of our conceptual model. We suggest that traditional habitat models and our conceptual model be combined to predict the limits of suitable fall chinook salmon spawning habitat. This approach can incorporate quantitative measures of river channel morphology, including general descriptors of geomorphic features at different spatial scales, in order to understand the processes influencing redd site selection and spawning habitat use. This information is needed in order to protect existing salmon spawning habitat in large rivers, as well as to recover habitat already lost.

Improvements to the quantitative assay of nonrefractory minerals for Fe(II) and total Fe using 1,10-phenanthroline

Abstract: Abstraet--A method using 1,10-phenanthroline (phen) to quantify Fe(II) and total Fe in nonrefractory minerals was modified to improve the accuracy and precision and to eliminate the inconvenience of performing much of the analysis under darkroom conditions. Reagents were combined to minimize solution-handling errors, volumes of the reagent additions were determined gravimetrically and the acidmatrix solution was preheated to near-boiling before sample contact. The darkness requirement, which stems from the photoreduction of Fe(III) to Fe(II) in the presence of phen, was eliminated by the use of opaque amber-colored high-density-polyethylene bottles during the digestion step and for storage of the digestate and subsequent dilutions before Fe(II) analysis. Reduction of Fe(III) for total-Fe analysis was accomplished either by exposure to light from a Hg-vapor lamp or by reaction with hydroxylamine, NH2OH. Although the minimum periods required for adequate reduction ranged from 1.5 to 4 h, the optimum reduction periods were between 6 and 10 h. When standard samples containing Fe(II) and MnC12 were digested and analyzed for total-Fe using the light treatment (with incidental heating to 35-45 ~ significant decreases and in some instances, oscillations, in absorptivity were obtained. Similar experiments with NH2OH, or with CrC13 showed no effect. The absorptivity of most digestates stored in opaque bottles was stable for at least 2 weeks, although digestates with Mn concentrations above 3 ~g mL showed proportional decreases in absorptivity. Analysis of 8 geochemical reference materials by the modified method (using NH2OH) yielded excellent agreement with published values and a mean relative standard deviation of 0.6%. Total-Fe results obtained using the light treatment, however, were generally lower (-2% relative) than the NH2OH values, although this difference decreased with longer irradiation periods. Use of NH2OH was deemed preferable because it was simpler, faster, minimized interferences from Mn and eliminated the need for specialized apparatus. Lastly, MICA Fe was shown to be unreliable as a primary reference material for Fe(II) determinations.

Structure and properties of ion-beam-modified (6H) silicon carbide

Abstract: The ion-beam-induced crystalline-to-amorphous phase transition in single crystal ( 6 H) α -SiC has been studied as a function of irradiation temperature. The evolution of the amorphous state has been followed in situ by transmission electron microscopy in specimens irradiated with 0.8 MeV Ne + , 1.0 MeV Ar + , and 1.5 MeV Xe + ions over the temperature range from 20 to 475 K. The threshold displacement dose for complete amorphization in α -SiC at 20 K is 0.30 dpa (damage energy=15 eV atom −1 ). The dose for complete amorphization increases with temperature due to simultaneous recovery processes that can be adequately modeled in terms of a single-activated process. The critical temperature, above which amorphization does not occur, increases with particle mass and saturates at about 500 K. Single crystals of α -SiC with [0001] orientation have also been irradiated at 300 K with 360 keV Ar 2+ ions at an incident angle of 25° over fluences ranging from 1 to 8 Ar 2+ ions nm −2 . The damage accumulation in these samples has been characterized ex situ by Rutherford backscattering spectrometry–channeling (RBS/C) along the [0001] direction, Raman spectroscopy, cross-sectional transmission electron microscopy (XTEM), and mechanical microprobe measurements.

DOC-2, a candidate tumor suppressor gene in human epithelial ovarian cancer.

Abstract: Using RNA fingerprinting (RAP) strategy and Northern blot analysis, we identified a differentially expressed sequence DOC-2 which is detectable in all normal human ovarian surface epithelial (HOSE) cell cultures but not in ovarian cancer cell lines and tissues. Subsequent cloning of DOC-2 from a cDNA library generated from the HOSE cells was carried out using the 3′ and 5′ RACE approach. A 3268 base pair full length cDNA of DOC-2 was isolated and sequenced. The predicted protein has a length of 770 amino acids. Homology search of all NCBI sequences indicated that the amino acid sequence of DOC-2 shares 93% homology with the mouse p96/mDab2 phosphoprotein and has a phosphotyrosine interacting domain (PID) and multiple SH3 binding motifs. Chromosomal localization by FISH showed that the DOC-2 gene is located on 5p13. Western blot analysis showed that the 105 kDa DOC-2 protein was down-regulated in all the carcinoma cell lines. In-situ immunohistochemistry performed on normal ovaries, and benign, borderline and invasive ovarian tumor tissues showed down regulation of DOC-2 protein particularly in serous ovarian tumor tissues. When DOC-2 was transfected into the ovarian carcinoma cell line SKOV3, the stable transfectants showed significantly reduced growth rate and ability to form tumors in nude mice. These data suggest that down-regulation of DOC-2 may play an important role in ovarian carcinogenesis.

Microbial and surface chemistry controls on reduction of synthetic Fe(III) oxide minerals by the dissimilatory iron‐reducing bacterium Shewanella alga

Abstract: The role of Fe(II) biosorption and the effect of medium components on the rate and long‐term extent of Fe(III) oxide reduction (FeRed) by a dissimilatory Fe(III)‐reducing bacterium (Shewanella alga strain BrY) were examined in batch culture experiments. Introduction of fresh S. alga cells into month‐old cultures in which Fe(III) reduction had ceased resulted in further reduction of synthetic amorphous Fe(III) oxide, hematite, and two forms of goethite (Gt). Fresh S. alga cells were also able to reduce a substantial amount of synthetic Gt that had been partly or completely saturated with sorbed Fe(II). Cells that had been precoated with Fe(II) showed a reduced rate and capacity for FeRed. These results indicated that biosorption of Fe(II) had a major impact on FeRed. S. alga cells were shown to have an Fe(II) sorption capacity of ∼0.1 mmol g−1, compared with ∼0.25 mmol g−1 determined for the synthetic Gt. Sorption experiments with component mixtures indicated that direct interaction between cells and oxide...

Reverse Transcriptase (RT) Inhibition of PCR at Low Concentrations of Template and Its Implications for Quantitative RT-PCR

Abstract: Numerous instances of reverse transcriptase (RT) inhibition of the PCR were observed while developing nonquantitative uncoupled RT-PCR techniques for detecting nitrogenase and ammonia monooxygenase gene expression in situ. The inhibitory effect of RT on the PCR was removed with increasing template concentrations beyond 105 to 106 copies. Including T4 gene 32 protein during the reverse transcription phase of the RT-PCR reaction increased the RT-PCR product yield by as much as 483%; if gene 32 protein was introduced after reverse transcription but prior to the PCR phase, no improvement in product yield was observed. Addition of 1 μg of exogenous calf thymus DNA or yeast tRNA did little to relieve RT inhibition of the PCR on both genomic DNA and mRNA templates. These results suggest that RT inhibition of the PCR is mediated through direct interaction with the specific primer-template combination (DNA and RNA) and point to specific assay modifications for estimating the extent of RT inhibition and counteracting some of the inhibitory effect. Furthermore, the working hypothesis of RT inhibition below a 105 to 106 copy threshold has important implications for quantitative RT-PCR studies. In particular, competitive, quantitative RT-PCR systems will consistently underestimate the actual RNA concentration. Hence, enumerations of RNA templates below 105 to 106 copies will be relative to an internal standard and will not be an absolute measure of RNA abundance in situ.

Electronic Structure of Dipole-Bound Anions

Abstract: Dipole-bound anionic states of HCN, (HF)2, CH3CN, C3H2, C4H2, C5H2, and stretched CH3F are studied using extended one-electron basis sets at the coupled cluster level of theory with single, double, and noniterative triple excitations (CCSD(T)). Orbital relaxation and electron correlation corrections to the Koopmans' theorem prediction of electron binding energy are analyzed, and a physical interpretation of low-order corrections is proposed. It is demonstrated that the second-order dispersion interaction between the loosely bound electron and the electrons of the neutral host should be included into physical models of dipole-bound anions. Higher-order electron correlation corrections are also found to be important, and a slow convergence of the Moller−Plesset series for electron binding energies is documented. Modifications of the potential energy surfaces of the above polar molecules upon electron attachment are studied at the second-order Moller−Plesset level, and Franck−Condon factors for the anion/neu...

Competition between Sea Salt and Sulfate Particles as Cloud Condensation Nuclei

Abstract: The influence of sea salt on the cloud droplet activation of sulfate particles is investigated using a size-resolving model of the aerosol activation process. The authors found that the total number concentration of activated cloud droplets increases with increasing sea salt concentration if the sulfate number concentrations are relatively low and updrafts are strong, but it decreases with higher sea salt if sulfate number concentrations are high and cloud updrafts are weak. The increase is due to the activation of accumulation mode sea salt particles, while the decrease is due to the reduction in maximum cloud supersaturation due to competition with coarse mode sea salt particles. These conclusions are insensitive to the sulfate size distribution and surface wind speed.

TOPIC ISLANDS/sup TM/-a wavelet-based text visualization system

Abstract: We present a novel approach to visualize and explore unstructured text The underlying technology, called TOPIC-O-GRAPHY/sup TM/, applies wavelet transforms to a custom digital signal constructed from words within a document The resultant multiresolution wavelet energy is used to analyze the characteristics of the narrative flow in the frequency domain, such as theme changes, which is then related to the overall thematic content of the text document using statistical methods The thematic characteristics of a document can be analyzed at varying degrees of detail, ranging from section-sized text partitions to partitions consisting of a few words Using this technology, we are developing a visualization system prototype known as TOPIC ISLANDS to browse a document, generate fuzzy document outlines, summarize text by levels of detail and according to user interests, define meaningful subdocuments, query text content, and provide summaries of topic evolution

Phylogenetic Diversity of Archaea and Bacteria in a Deep Subsurface Paleosol

Abstract: A low-biomass paleosol 188 m below the ground surface at the Department of Energy's Hanford Site in south-central Washington State was recovered and maintained at the in situ temperature (17°C) as an intact core or homogenized sediment for 0, 1, 3, 10, and 21 weeks post-sampling. Bacterial and archaeal 16S rRNA genes were amplified by PCR and cloned. Of 746 bacterial and 190 archaeal clones that were categorized by restriction fragment length polymorphism (RFLP), 242 bacterial and 16 archaeal clones were partially sequenced and compared against the small subunit ribosomal RNA database (RDP) and GenBank. Six bacterial and 16 archaeal clones sequences, with little similarity to those in public databases, were sequenced in their entirety, and subjected to more detained phylogenetic analysis. The most frequently occurring clones types were related to Pseudomonas, Bacillus, Micrococcus, Clavibacter, Nocardioides, Burkholderia, Comamonas, and Erythromicrobium. Clone sequences whose RDP similarity value was ≥0.6 consistently grouped with their nearest RDP neighbor during phylogenetic analysis. Six truly novel eubacterial sequences were identified; they consistently cluster with or near the Chloroflexaceae and sequences recovered from the Sargasso Sea. Sixteen unique archaeal RFLP groups were identified from 190 randomly-sampled clones. The novel archaeal rDNA clones formed a coherent clade along the major Crenarchaea branch containing all previously described mesophilic crenarchae clones, but remained firmly associated with 16S rDNA clones previously obtained from a thermal Fe/S spring in Yellowstone National Park. The wealth of group-specific genetic information identified during this study will now allow us to address specific hypotheses related to in situ stimulation of these deep subsurface microorganisms and changes in microbial community composition resulting from subsurface contamination or remediation processes at the Hanford Site.

Reversible Surface Properties of Glass Plate and Capillary Tube Grafted by Photopolymerization of N-Isopropylacrylamide

Abstract: A new, simple, and effective method to modify the surface of glass plate and quartz capillary tube by ultraviolet (UV) photopolymerization of N-isopropylacrylamide (NIPAAm) has been developed. A photosensitizer, silane coupling agent with the dithiocarbamate group, was synthesized by the condensation reaction between chloropropyltrimethoxysilane and sodium N,N‘-diethyldithiocarbamate. The thiocarbamate groups were installed on the glass surface by coupling the silane agent with the hydroxyl groups on the glass surface. Subsequently, the silane-modified surface was photografted by NIPAAm in the presence of N,N‘-methylenebisacrylamide. The characteristics of the glass surfaces were examined by scanning electronic microscopy (SEM) and the static and dynamic contact angle techniques. The thickness of grafted PNIPAAm film is less than 320 nm, and the surface showed a completely hydrophilic nature at about room temperature and a hydrophobic nature above 40 °C. The water meniscus height in a capillary tube (2 mm...