Showing papers by "Pacific Northwest National Laboratory published in 1984"

Variational Transition State Theory

Abstract: In recent years our research group has made a systematic effort to study the validity of transition state theory (TST). We have found that the conventional theory is sometimes remarkably accurate, but in many other cases it leads to large errors. Fortunately we have found that a much more reliable theory that has many of the advantages of conventional TST can also be formulated, and it can be applied to practical problems with an effort that is much closer to that required for conventional transition state theory than to that required for quantal dynamics calculations. The two most important features in the improved approach to transition state theory state theory are the variational determination of the transition state and the incorporation of tunneling contributions by multidimensional semiclassical approximations. 13 refs.

Systematic GVB study of harmonic vibrational frequencies and dipole moment derivatives: The vinyl radical C2H3 and other simple molecules

Abstract: Structure, harmonic vibrational frequencies, and dipole moment derivatives of methane, ethylene, and acetylene have been obtained from generalized valence bond (GVB) wave function calculations. The results are compared to Hartree–Fock (HF) data, and other correlated wave function data. It is found that the GVB method consistently overemphasizes left–right electron correlation effects, and predicts bond lengths ∼0.01–0.02 A longer than experiment. However, the calculated harmonic frequencies are within 4.2% of the observed fundamentals and within 3.5% of the experimental harmonic frequencies. Dipole moment derivatives are in semi‐quantitative agreement with experiment. The method is used to predict the IR spectrum of the vinyl radical, including a very intense out of plane bending mode with frequency near 1000 cm−1.

Toxicity of uranium to Daphnia magna

Abstract: The toxicity of U to Daphnia magna was determined in acute and chronic tests. The 48-hr LC50 of U (VI) in Columbia River water was 6 mg L−1. Acute toxicity diminished by a factor of 7.5 as mean water hardness and alkalinity values increased from 70 mg L−1. and 57 mg L−1. to 195 mg L−1. and 130 mg L−1. respectively. This effect was most likely the result of complexation of uranyl ion with carbonate ions. D. magna reproduction was suppressed in Columbia River water at U concentrations between 0.5 and 3.5 mg L−1. Potential hazards of U to aquatic life are discussed as they relate to mining practices.

Movement and Activity Patterns of Mule Deer in the Sagebrush-Steppe Region

Abstract: The movements and activity patterns of radio-collared mule deer ( Odocoileus hemionus ) were studied from 1980 to 1982 in the sagebrush-steppe region of south-central Washington. The average home range size for adult deer was 39.3 ± 26.5 km2 ( n = 34). Home range sizes for male and female deer were not significantly different ( P = 0.48). Intensity of use of home range area by deer was not uniform and physical features within the home range, such as trees and large bodies of water, influenced deer movements. Three (8%) of 37 monitored deer dispersed from their original home ranges during approximately 25 deer-years of monitoring. In addition, seven (19%) deer made sporadic, temporary wandering movements of up to 15 km beyond their normal home range boundaries. Based on rate of movement, deer had clearly defined crepusular activity patterns.

Effect of irradiation particle mass on crystallization of amorphous alloys

Abstract: The crystallization temperature of amorphous alloys was found to be significantly lowered by heavy ion or electron irradiation during annealing However, only heavy ion irradiation altered the mode of crystallization Both a binary and multi-element amorphous alloy showed this type of response to irradiation Radiation-enhanced diffusion processes in the amorphous state can explain the increased crystallization kinetics during irradiation Heavy ion irradiation alters the crystallization mode by causing direct transformation to the final equilibrium phase as opposed to intermediate metastable phase formation during thermal annealing or electron irradiation The equilibrium phase is believed to nucleate directly in the displacement cascades, which only form during heavy ion bombardment

Hydrogen atom abstraction from aldehydes: OH+H2CO and O+H2CO

Abstract: The essential features of the potential energy surfaces governing hydrogen abstraction from formaldehyde by oxygen atom and hydroxyl radical have been characterized with ab inito multiconfiguration Hartree-Fock (MCHF) and configuration interaction (CI) wave functions. The results are consistent with a very small activation energy for the OH + H2CO reaction, and an activation energy of a few kcal/mol for the O + H2CO reaction. In the transition state structure of both systems, the attacking oxygen atom is nearly collinear with the attacked CH bond.

Seasonal and Habitat Distribution of Tenebrionid Beetles in Shrub-Steppe Communities of the Hanford Site in Eastern Washington

Abstract: The Tenebrionid beetle population of the Department of Energy's Hanford Site was studied during a 3-year period to determine the seasonal and habitat distribution of the 15 common species within six major biotic communities. Soil texture and vegetation type were examined to determine their influence on species distributions. Four species occurred in all six of the communities, whereas five species were restricted to one or two study sites. Three patterns of seasonal distributions were present. Two species were found only during the fall; a second group contained species which were encountered throughout the year; the third group consisted predominantly of summer species. Soils were divided into three classes: loamy sand, sandy loam, and loam. Several species were restricted to one soil type.

Statistically Designed Optimization of a Glass Composition

Abstract: An efficient, statistically based methodology for development and optimization of multicomponent materials is presented. The approach is illustrated with a five-component nuclear waste glass. A composition field is defined, test compositions are statistically chosen, and their measured property data are used to fit empirical models. These models are then used to predict the optimum composition. The following nuclear waste glass components were investigated: SiO/sub 2/, B/sub 2/O/sub 3/, Na/sub 2/O, CaO, and simulated nuclear waste. The following properties were modeled: viscosity, chemical durability, and crystallinity. Successful models were constructed by using data from 27 test melts. This methodology could be applied to a wide range of ceramic mixture problems.

Studies on prenatal and postnatal development in rats exposed to 60‐Hz electric fields

Abstract: A series of three experiments was performed to determine the effects of 30-day exposures to uniform 60-Hz electric fields (100 kV/m) on reproduction and on growth and development in the fetuses and offspring of rats. In the first experiment, exposure of females for 6 days prior to and during the mating period did not affect their reproductive performance, and continued exposure through 20 days of gestation (dg) did not affect the viability, size, or morphology of their fetuses. In the second experiment, exposure of the pregnant rat was begun on 0 dg and continued until the resulting offspring reached 8 days of age. In the third experiment, exposure began at 17 dg and continued through 25 days of postnatal life. In the second and third experiments, no statistically significant differences suggesting impairment of the growth or survival of exposed offspring were detected. In the second experiment, a significantly greater percentage of the exposed offspring showed movement, standing, and grooming at 14 days of age than among-sham-exposed offspring. There was a significant decrease at 14 days in the percentage of exposed offspring displaying the righting reflex in the second experiment and negative geotropism in the third experiment. These differences were all transient and were not found when the animals were tested again at 21 days of age. Evaluation of the reproductive integrity of the offspring of the second experiment did not disclose any deficits.

Electron production in collisions between light ions and rare gases: the importance of the charge-transfer and direct-ionization channels

Abstract: Coincidence measurements were performed to separate the charge-transfer and directionization channels for 15-100-keV ${\mathrm{H}}^{+}$, ${\mathrm{He}}^{+}$ collisions with Ne,Ar,Kr. Absolute cross sections are given for the production of single and multiple ionization of the target by these two ionization mechanisms. It is demonstrated that as the collision system becomes heavier, the multiple ionization components of these two channels become increasingly more important, and the production of free electrons results primarily from higher-order charge-transfer channels---not from direct single target ionization.

The Modification of Plume Models to Account for Dry Deposition

Abstract: The assumptions and predictions of four diffusion-deposition models are compared, and two simple plume depletion models are recommended. One model applies an analytical, constant eddy-diffusivity solution of the advection-diffusion equation as a deposition correction to the general Gaussian plume model. Predictions of this model compare moderately well with those of the surface depletion model, an exact treatment of plume depletion, and it is particularly useful for estimating the transport and deposition of settling particles. The second model is a correction to the simple source depletion model that also accounts for the change in the vertical concentration profile caused by deposition. The computational requirements of this model are similar to those of the unmodified source depletion model, while its predictions near the surface are very close to those of the surface depletion model.

Developmental toxicity following oral administration of a high‐boiling coal liquid to pregnant rats

Abstract: Heavy distillate (HD), the highest-boiling coal liquid from the solvent-refined coal-II process (SRC-II), was administered by intragastric (IG) intubation to pregnant rats. Five dose levels of HD (0.09, 0.14, 0.18, 0.36 and 0.74 g kg-1), were given daily from 12 to 16 days of gestation and the rats were killed at 20 days of gestation. Maternal body weights and weights of the liver, kidneys, spleen, adrenals, thymus, ovaries and the gravid uterus were obtained. Gravid uteri were evaluated for prenatal mortality. Live fetuses were examined for malformations and weighed; fetal lungs were excised and weighed. Maternal (extragestational) weight gains and thymic weights diminished in all groups that received the SRC material. Adrenal weights were increased in all treated animals, except for those in the lowest-dose group (0.9 g kg-1). There was significant maternal mortality at 0.74 g kg-1 and increased intrauterine mortality at doses of 0.37 and 0.74 g kg-1. Placental weight was depressed, and the incidence of fetal anomalies was increased at 0.14 g kg-1 and all higher dose levels.

Induced swelling in radiation damaged ZrSiO4

Abstract: A hydrothermal gelation method was used to prepare phase pure polycrystalline ZrSiO4 which was sintered to 95% theoretical density. Actinide doped samples containing 10 wt% 238Pu were prepared by an analogous procedure and incurred bulk radiation damage through internal alpha-decay processes. Undoped samples were subjected to external irradiation from 5.5 MeV alpha sources, and from a 60Co gamma source. Actinide doped ZrSiO4 exhibits dose dependent swelling caused by displacement processes leading to ingrowth of amorphous regions. Bulk density and XRD measurements, as a function of dose, showed first order exponential ingrowth behavior similar to that observed in other actinide doped materials. Results are compared with reported data for naturally damaged crystals subjected to significantly lower alpha decay rates. No significant dose rate dependence on damage ingrowth has been observed. Kinetic models for the observed dose dependent swelling are proposed and rate constants for damage ingrowth in synthetic and natural crystals are compared. To study localized damage induced by both external alpha and gamma irradiation, vibrational Raman measurements were obtained for several accumulated doses. Results indicate that the initial stage of damage ingrowth is confined to the silicate sublattice. Vibrational results will be discussed in terms of microstructural changes which result from irradiation.

Glass reactivity in aqueous solutions

Abstract: Surface analysis methods have been incorporated as part of several studies concerning the mechanisms and amount of glass leaching in aqueous solutions. The reactivity of simple glasses with water has been determined by measuring the uptake of D and 18O in soda‐lime silicate glass, amorphous and crystalline silica, and amorphous and crystalline albite leached in D218O at 90 °C as a function of time. The concentrations and profiles of 18O and D going into the glass were determined using nuclear reaction analysis and compared to the material leached from the glass as determined by solution and Rutherford backscattering (RBS) analyses. The measured ratio of D/18O does not follow any one simple uptake model. Reaction layers formed on simulated nuclear waste glasses containing Pu have also been measured using RBS. Specimens were leached in deionized water or brine at 90 °C. The concentration of Pu on the specimens generally decreased with time. Analysis of the leaching solution indicated that the rate of Pu release was considerably less than that of the glass matrix. The results support the buildup of a surface layer covering the Pu.

An Ultralow Background Germanium Gamma-Ray Spectrometer Using Superclean Materials and Cosmic Ray Anticoincidence

Abstract: Efforts to measure the double beta decay of /sup 76/Ge as predicted by Grand Unified Theories have resulted in the development of a high resolution germanium diode gamma-ray spectrometer with an exceptionally low background This paper describes the development of this system and how these techniques can be utilized to significantly reduce the background in high resolution photon spectrometers at only a moderate cost

Raman characterization of all-dielectric multilayer SiO 2 /TiO 2 optical coatings

Abstract: Raman spectroscopy can be used to characterize the rutile/anatase phase composition of TiO2 layers in all-dielectric filters and reflectors of arbitrary design. No special specimen preparation is necessary. Interference effects can enhance Raman scattering compared to single-layer coatings of the same total TiO2 thickness.

Kinetic Differences Between Fed and Starved Chinese Hamster Ovary Cells

Abstract: When Chinese hamster (CHO-K1) cells are grown as monolayer cultures, they eventually reach a population-density plateau after which no net increase in cell numbers occurs. The kinetics of aged cells in nutritionally deprived (starved) or density-inhibited (fed) late plateau-phase cultures were studied by four methods: (i) Reproductive integrity and cell viability were monitored daily by clonogenic-cell assay and erythrosin-b dye-exclusion techniques. (ii) Mitotic frequencies of cells from 18 day old cultures were determined during regrowth by analysing time-lapse video microscope records of dividing cells. (iii) Tritiated-thymidine ([3H]TdR) autoradiography was used to determine the fractions of DNA-synthesizing cells in cultures entering plateau phase and during regrowth after harvest. (iv) The rate of labelled nucleoside uptake and incorporation into DNA was measured using liquid scintillation or sodium iodide crystal counters after labelling with [3H]TdR or [125I]UdR. Non-cycling cells in starved cultures accumulate primarily as G1 phase cells. Most cells not in G1 phase had stopped in G2 phase. Very few cells (less than 2%) were found in S phase. In contrast, about half of the cells in periodically fed cultures were found to be in DNA-synthetic phase, and the percentage of these S phase cells fluctuated in a manner reflecting the frequency of medium replacement. Populations of both types of plateau-phase cultures demonstrate extremely coherent cyclic patterns of DNA synthesis upon harvest and reculturing. They retain this high degree of synchrony for more than three generations after the resumption of growth. From these data it is concluded that nutritionally deprived (starved) late plateau-phase cells generally stop in either G1 or G2 phase, whereas periodically fed late plateau-phase cultures contain a very large fraction of cycling cells. Populations of cells from these two types of non-expanding cultures are kinetically dissimilar, and should not be expected to respond to extracellular stimuli in the same manner.

Corrosion Resistance of Amorphous FeNiCrW Alloys

Abstract: The corrosion resistance of amorphous FeNiCrW alloys prepared by cosputtering of Type 304 stainless steel and W was studied in chloride solutions by potentiodynamic polarization methods. In both neutral and acidic solutions, the as-deposited amorphous FeNiCrW alloys had excellent corrosion resistance, similar to that of metal-metalloid amorphous alloys containing Cr and P. This result demonstrates that P is not essential for producing corrosion resistance in amorphous materials. More significantly, the corrosion resistance of amorphous FeNiCrW alloys in neutral solutions was preserved after heat treatment at the crystallization temperature. In acidic solutions, these heat treated alloys exhibited a slight increase in active dissolution but remained highly passivated at high potentials. The retention of corrosion resistance of the heat treated amorphous FeNiCrW alloys was attributed to a two stage crystallization process wherein fine BCC crystallites were formed in the amorphous matrix with no seg...

Reduction of substrate interference in Raman spectroscopy of submicron titania coatings

Abstract: Recent interests in low-loss and low-scatter optical coatings have generated a need for structural characterization of submicron dielectric films on a substrate. Conventional x-ray diffraction works well only for thick films; its required long measurement time, typically hours, leaves much to be desired. Recently, using Raman spectroscopy in a 180/sup 0/ backscattering geometry, Pawlewicz et al. were able to characterize crystalline single-layer optical dielectric coatings with a measurement time a factor of 100 less than that required for the conventional method of x-ray diffraction. The authors concluded that the minimum thickness for single-layer Raman spectroscopy of TiO/sub 2/ anatase coatings on silica substrates is approx. 125 nm and that for thinner coatings, the more sensitive interference-enhanced Raman scattering technique, should be used. This latter technique requires that the coating under investigation be deposited as the top layer of a specially prepared trilayer structure with a reflecting substrate and thus would require a modification to the original coating. The single-layer technique is a direct method and is more desirable if its sensitivity can be improved.