This thesis describes a number of diverse experiments whose common theme is to elaborate some aspect of DNA supercoiling. The torsion elastic constant of DNA is measure as a function of superhelix density using the technique of picosecond Time Resolved Fluorescence Polarization Anisotropy (FPA) of intercalated ethidium bromide. The results agree with theories which predict that the anisotropy decay should vary with the square root of the relative viscosity. This experiment furthermore demonstrates a sensitivity of FPA to a change in torsion elastic constant of less than 10%. A number of covalently closed DNA samples, ranging in superhelix density from = {minus}0.123 to {plus}0.042, are then examined. A novel method for measuring changes in local supercoiling on a large PNA molecule which is sensitive to changes in supercoiling of regions of chromosomal DNA as short as 1 kilobase in length is presented. Study of chromosomal supercoiling regulating anaerobic gene expression in the facultative photosynthetic bacterium, Rhodobacter capsulatus showed that no stable change in chromosomal supercoiling upon a shift from aerobic respiratory growth to anaerobic photosynthetic conditions. Studies to detect transient changes in DNA supercoiling indicate that DNA downstream from heavily transcribed genes for the photosynthetic reaction center are relaxed or …

Goal was to study effect of power level and distribution on thermocapiilary-induced weld shape and of arc factors on weld shape. Thermocapillarity was apparent in both conduction mode EB welds and GTA welds, particularly in the former. A non-Gaussian arc distribution is suggested for accounting for the differences between the twoss processes. At higher current levels (200--300 A), plasma shear force also contributes to weld shape development. Evidence suggests that thermocapillary flow reversal is not a factor in normal GTA welds; EDB flow reversal occurs only at high power density levels where the keyhole mode is present.

Gamma-ray excited emission spectrum, absolute scintillation yield, rise and decay time constants, and thermoluminescence emissions of CsI(Tl) were measured at {minus}100 to +50 C, for crystals from 4 different vendors. The thermoluminescence glow curves were the only property that varied significantly from crystal to crystal; room temperature operation in current mode could be susceptible to temperature fluctuations. The CsI(Tl) emission spectrum has emission bands peaking around 400 and 560 nm; the former band disappears between {minus}50 and {minus}75 C. The RT absolute scintillation yield was calculated to be 65,500{plus_minus}4,100 photons/MeV. The two primary decay time constants increases about exponentially with inverse temperature. An ultra-fast decay component was confirmed. Applications are discussed.

Replicate column experiments were done to quantify the effects of temperature and bacterial motility on advective transport through repacked, but otherwise unaltered, natural aquifer sediment. The bacteria used in this study, A0500, was a flagellated, spore-forming rod isolated from the deep subsurface at DOE`s Savannah River Laboratory. Motility was controlled by turning on flagellar metabolism at 18{degrees}C but off at 40{degrees}C. Microspheres were used to independently quantify the effects of temperature on the sticking efficiency ({alpha}), estimated using a steady-state filtration model. The observed greater microsphere removal at the higher temperature agreed with the physical-chemical model, but bacteria removal at 18{degrees}C was only half that at 4{degrees}C. The sticking efficiency for non-motile A0500 (4{degrees}C) was over three times that of the motile A0500 (18{degrees}C), 0.073 versus 0.022 respectively. Analysis of complete breakthrough curves using a non-steady, kinetically limited, transport model to estimate the time scales of attachment and detachment suggested that motile A 0500 bacteria traveled twice as far as non-motile A 0500 bacteria before becoming attached. Once attached, non-motile colloids detached on the time scale of 9 to 17 days. The time scale for detachment of motile A0500 bacteria was shorter, 4 to 5 days. Results indicate that bacterial …

The research illustrated in this thesis was performed under the guidance of Professor Dennis C. Johnson beginning in March 1987. Chapter 2 concentrates on the development and electrocatalytic properties of iron-doped {beta}-PbO{sub 2} films on noble-metal substrates. Chapter 3 focuses attention on the preparation and characterization of iron-doped {beta}-PbO{sub 2} films on titanium substrates (Fe-PbO{sub 2}/Ti). Chapter 4 discusses anodic evolution of ozone at Fe-PbO{sub 2}/Ti electrodes. Chapter 5 describes electrochemical incineration of p-benzoquinone (BQ) at Fe-PbO{sub 2}/Ti electrodes. In addition, the Appendix includes another published paper which is a detailed study of {alpha}-PbO{sub 2} films deposited on various types of stainless steel substrates.

A liquid chromatographic method for the determination of water in soil or clay samples is presented. In a separate study, the optimization of electrophoretic separation of alkylated phenolate ions was optimized by varying the pH and acetonitrile concentration of the buffer solutions.

In most episodes of health complaints reported in office buildings in the last-twenty years, causal factors have not been identified. In order to assess risk factors for work-related symptoms in office workers, a reanalysis was performed of previous studies, and an epidemiologic study was conducted. The reanalysis of data, showed remarkable agreement among studies. Air-conditioned buildings were consistently associated with higher prevalence of headache, lethargy, and eye, nose, or throat problems. Humidification was not a necessary factor for this higher prevalence. Mechanical ventilation without air-conditioning was not associated with higher symptom prevalence. A study was conducted among 880 office workers, within 12 office buildings selected without regard to worker complaints, in northern California. A number of factors were found associated with prevalence of work-related symptoms, after adjustment in a logistic regression model for personal, psychosocial, job, workspace, and building factors. Two different ventilation types were associated with increases Ln symptom prevalence, relative to workers in naturally ventilated buildings: mechanical supply and exhaust ventilation, without air conditioning and with operable windows; and air-conditioning with sealed windows. No study buildings were humidified. In both these ventilation types, the highest odds ratios (ORs) found were for skin symptoms (ORs-5.0, 5.6) and for tight …

BaF{sub 2} has the advantage over other scintillators, when comparing radiation hardness, scintillation decay time, and fast scintillation yield. Since the fast BaF{sub 2} emissions have peak wavelengths of 220, 195, and 170 nm, a wavelength shifter (WLS) is needed. Organic fluors were evaluated as WLS components. Results indicate that spectral separation using WLS is possible, but not to the extent desired; other techniques must be used also. Alternative scintillators, such as CeF{sub 3}, should be investigated.

The vibrational to translational (V{yields}T) energy transfer in collisions between large highly vibrationally excited polyatomics and rare gases was investigated by time-of-flight techniques. Two different methods, UV excitation followed by intemal conversion and infrared multiphoton excitation (IRMPE), were used to form vibrationally excited molecular beams of hexafluorobenzene and sulfur hexafluoride, respectively. The product translational energy was found to be independent of the vibrational excitation. These results indicate that the probability distribution function for V{yields}T energy transfer is peaked at zero. The collisional relaxation of large polyatomic molecules with rare gases most likely occurs through a rotationally mediated process. Photodissociation of nitrobenzene in a molecular beam was studied at 266 nm. Two primary dissociation channels were identified including simple bond rupture to produce nitrogen dioxide and phenyl radical and isomerization to form nitric oxide and phenoxy radical. The time-of-flight spectra indicate that simple bond rupture and isomerization occurs via two different mechanisms. Secondary dissociation of the phenoxy radicals to carbon monoxide and cyclopentadienyl radicals was observed as well as secondary photodissociation of phenyl radical to give H atom and benzyne. A supersonic methyl radical beam source is developed. The beam source configuration and conditions were optimized for CH{sub 3} production from …

A program is currently in progress at Argonne National Laboratory to evaluate and develop evaporator technology for concentrating radioactive waste streams. By concentrating radioactive waste streams, disposal costs can be significantly reduced. To effectively reduce the volume of waste, the evaporator must achieve high decontamination factors so that the distillate is sufficiently free of radioactive material. One technology that shows a great deal of potential for this application is being developed by LICON, Inc. In this program, Argonne plans to apply LICON`s evaporator designs to the processing of radioactive solutions. Concepts that need to be incorporated into the design of the evaporator include, criticality safety, remote operation and maintenance, and materials of construction. To design an effective process for concentrating waste streams, both solubility and vapor-liquid equilibrium data are needed. The key issue, however, is the high decontamination factors that have been demonstrated by this equipment. Two major contributions were made to this project. First, a literature survey was completed to obtain available solubility and vapor-liquid equilibrium data. Some vapor-liquid data necessary for the project but not available in the literature was obtained experimentally. Second, the decontamination factor for the evaporator was determined using neutron activation analysis (NAA).

This dissertation studies methods for estimating extremely small probabilities by Monte Carlo simulation. Problems in radiation transport typically involve estimating very rare events or the expected value of a random variable which is with overwhelming probability equal to zero. These problems often have high dimensional state spaces and irregular geometries so that analytic solutions are not possible. Monte Carlo simulation must be used to estimate the radiation dosage being transported to a particular location. If the area is well shielded the probability of any one particular particle getting through is very small. Because of the large number of particles involved, even a tiny fraction penetrating the shield may represent an unacceptable level of radiation. It therefore becomes critical to be able to accurately estimate this extremely small probability. Importance sampling is a well known technique for improving the efficiency of rare event calculations. Here, a new set of probabilities is used in the simulation runs. The results are multiple by the likelihood ratio between the true and simulated probabilities so as to keep the estimator unbiased. The variance of the resulting estimator is very sensitive to which new set of transition probabilities are chosen. It is shown that a zero …

The series of projects described in this dissertation was stimulated by the discovery of high temperature superconductivity. Our goal was to develop useful applications which would be competitive with the current state of technology. The high-{Tc} microbolometer was developed into the most sensitive direct detector of millimeter waves, when operated at liquid nitrogen temperatures. The thermal boundary resistance of thin YBa{sub 2}Cu{sub 3}0{sub 7-{delta}} films was subsequently measured and provided direct evidence for the bolometric response of high-{Tc} films to fast (ns) laser pulses. The low-{Tc} microbolometer was developed and used to make the first direct measurements of the frequency dependent optical efficiency of planar lithographed antennas. The hot-electron microbolometer was invented less than a year prior to the writing of this dissertation. Our analysis, presented here, indicates that it should be possible to attain up to two orders of magnitude higher sensitivity than that of the best available direct detectors when operated at the same temperature. The temperature readout scheme for this device could also be used to measure the intrinsic interaction between electrons and phonons in a metal with a sensitivity that is five orders of magnitude better than in previous measurements. Preliminary measurements of quasiparticle trapping effects …

Measurements have been made of the scaled jet energies (x{sub 1}, x{sub 2}, x{sub 3}) and the Ellis-Karliner angle (cos{theta}{sub EK}), which are sensitive to the spill of the gluon, in the 3-jet hadronic events from the e{sup +}e{sup {minus}} annihilation at the Z{sup 0} resonance. The experiment is performed with the SLD detector at the Stanford Linear Accelerator Center (SLAC). The data used in this analysis was collected during the 1992 physics run, which includes 10,252 hadronic Z{sup 0} events that have CDC information written out. Only charged tracks measured in the central drift chamber are used for the measurements of the above variables. The raw data are found to be in good agreement with the Monte Carlo simulations passing the same set of track and event selection cuts. A bin-to-bin correction is done for the distributions of x{sub 1}, x{sub 2}, x{sub 3}, and cos{theta}{sub EK} to account for the effects of hadronization, detector acceptance and resolution. The corrected data is compared to the parton level distributions of x{sub 1}, x{sub 2}, x{sub 3}, and cos{theta}{sub EK} simulated from the vector QCD model and the scalar gluon model respectively. The systematic errors, calculated for all the bins in …

Results are presented here from several two dimensional numerical calculations of events in Type II supernovae. A new 2-D hydrodynamics and neutrino transport code has been used to compute the effect on the supernova explosion mechanism of convection between the neutrinosphere and the shock. This convection is referred to as exterior convection to distinguish it from convection beneath the neutrinosphere. The model equations and initial and boundary conditions are presented along with the simulation results. The 2-D code was used to compute an exterior convective velocity to compare with the convective model of the Mayle and Wilson 1-D code. Results are presented from several runs with varying sizes of initial perturbation, as well as a case with no initial perturbation but including the effects of rotation. The M&W code does not produce an explosion using the 2-D convective velocity. Exterior convection enhances the outward propagation of the shock, but not enough to ensure a successful explosion. Analytic estimates of the growth rate of the neutron finger instability axe presented. It is shown that this instability can occur beneath the neutrinosphere of the proto-neutron star in a supernova explosion with a growth time of {approximately} 3 microseconds. The behavior of the …

This thesis develops and applies a technique for the simultaneous determination of P and S wave velocity models and hypocenters from a set of arrival times. The velocity models are parameterized in terms of cubic B-splines basis functions which permit the retrieval of smooth models that can be used directly for generation of synthetic seismograms using the ray method. In addition, this type of smoothing limits the rise of instabilities related to the poor resolving power of the data. V{sub P}/V{sub S} ratios calculated from P and S models display generally instabilities related to the different ray-coverages of compressional and shear waves. However, V{sub P}/V{sub S} ratios are important for correct identification of rock types and this study introduces a new methodology based on adding some coupling (i.e., proportionality) between P and S models which stabilizes the V{sub P}/V{sub S} models around some average preset value determined from the data. Tests of the technique with synthetic data show that this additional coupling regularizes effectively the resulting models.

The goal of this work was to study the behavior of the angular distribution of the electron form the decay of the W boson in a specific rest-frame of the W, the Collins-Soper frame. This thesis consists of four major divisions, each dealing with closely related themes: (a) Physics Background, (b) Description of the Hardware and General Software Tools, (c) Description of the Analysis and Specific Tools, and (d) Results and Conclusions. Each division is comprised of one or more chapters and each chapter is divided into sections and subsections.

Heliumlike ions play an extremely important role in X-ray astrophysics because of their emissivity and because the relative intensities of their emission lines can be used to infer physical characteristics of X-ray emitting plasmas, including temperature, electron density, and ionization balance. In order to properly apply these diagnostics, accurate atomic data are required, including cross sections for collisional excitation and ionization, radiative rates, and the wavelengths and strengths of satellite lines. Although theoretical atomic models have been created to estimate many of the rates and cross sections involved, very few experimental results are available for comparison with theoretical predictions. This thesis describes an experimental study of heliumlike neon using an electron beam ion trap, a device specifically designed to study X-ray emission from highly charged ions. Using a low-energy X-ray spectrometer designed and built for this experiment, electron impact excitation cross sections and dielectronic satellite strengths were measured for all significant n = 2{yields}1 emission lines in He-like and Li-like Ne over a range of energy extending from well below the direct excitation threshold of the lines to over fourteen times the threshold energy. The cross section for innershell ionization of Li-like Ne, which excites the He-like forbidden line, was …

The D0 Detector at the Fermi National Accelerator Laboratory is a large multipurpose detector facility designed for the study of proton-antiproton collision products at the center-of-mass energy of 2 TeV. It consists of an inner tracking volume, hermetic uranium/liquid argon sampling calorimetry, and an outer 47{pi} muon detector. In preparation for our first collider run, the collaboration organized a Cosmic Ray Commissioning Run, which took place from February--May of 1991. This thesis is a detailed study of the response of the central calorimeter to cosmic ray muons as extracted from data collected during this run. We have compared the shapes of the experimentally-obtained pulse height spectra to the Landau prediction for the ionization loss in a continuous thin absorber in the four electromagnetic and four hadronic layers of the calorimeter, and find good agreement after experimental effects are folded in. We have also determined an absolute energy calibration using two independent methods: one which measures the response of the electronics to a known amount of charge injected at the preamplifiers, and one which uses a carry-over of the calibration from a beam test of central calorimeter modules. Both absolute energy conversion factors agree with one another, within their errors. The …

A reproducible, high-yield synthesis of mono([8]annulene)uranium(4)dichloride (1) is reported, along with the X-ray crystal structural of the bis(pyridine) adduct. Metathesis reactions of the half-sandwich complex 1 with a variety of simple alkyl and alkoxy reagents failed to generate any isolable mono-ring complexes. Reactions of 1 with polydentate, delocalized anions did produce stable derivatives, including mono([8]annulene)uranium(4)bis(acetylacetonate) (4). An X-ray crystal structure of 4 is reported.

Research in the area of advanced batteries for electric-vehicle applications has increased steadily since the 1990 zero-emission-vehicle mandate of the California Air Resources Board. Due to their design flexibility and potentially high energy and power densities, lithium/polymer batteries are an emerging technology for electric-vehicle applications. Thermal modeling of lithium/polymer batteries is particularly important because the transport properties of the system depend exponentially on temperature. Two models have been presented for assessment of the thermal behavior of lithium/polymer batteries. The one-cell model predicts the cell potential, the concentration profiles, and the heat-generation rate during discharge. The cell-stack model predicts temperature profiles and heat transfer limitations of the battery. Due to the variation of ionic conductivity and salt diffusion coefficient with temperature, the performance of the lithium/polymer battery is greatly affected by temperature. Because of this variation, it is important to optimize the cell operating temperature and design a thermal management system for the battery. Since the thermal conductivity of the polymer electrolyte is very low, heat is not easily conducted in the direction perpendicular to cell layers. Temperature profiles in the cells are not as significant as expected because heat-generation rates in warmer areas of the cell stack are lower than …

Forest succession models and correlative models have predicted 200--650 kilometer shifts in the geographic range of temperate forests and forest species as one response to global climate change. Few studies have investigated whether population differences may effect the response of forest species to climate change. This study examines differences in tree-ring growth, and in the phenotypic plasticity of tree-ring growth in 16-year old white fir, Abies concolor, from ten populations grown in four common gardens in the Sierra Nevada of California. For each population, tree-ring growth was modelled as a function of precipitation and degree-day sums. Tree-ring growth under three scenarios of doubled C0{sub 2} climates was estimated.

In this study, the author examined the effect of grazing on phosphorus cycling in stream periphyton and leaf detritus communities using the snail Elimia clavaeformis. Phosphorus cycling fluxes and turnover rates were measured in a laboratory and in a natural stream, respectively, using radioactive tracer techniques.

Isotopically enriched {sup 70}Ge and {sup 74}Ge single crystals were successfully gown by a newly developed vertical Bridgman method. The system allows us to reliably grow high purity Ge single crystals of approximately 1 cm{sup 3} volume. To our knowledge, we have grown the first {sup 70}Ge single crystal. The electrically active chemical impurity concentration for both crystals was found to be {approximately}2 {times} cm{sup {minus}3} which is two order of magnitude better that of {sup 74}Ge crystals previously grown by two different groups. Isotopic enrichment of the {sup 70}Ge and the {sup 74}Ge crystals is 96.3% and 96.8%, respectively. The residual chemical impurities present in both crystals were identified as phosphorus, copper, aluminum, and indium. A wide variety of experiments which take advantage of the isotopic purity of our crystals are discussed.

Analysis of the literature indicated that radon transport models significantly and consistently underpredict the advective entry into houses of soil-gas borne radon. Advective entry is the dominant mechanism resulting in high concentrations of radon indoors. The author investigated the source of the model-measurement discrepancy via carefully controlled field experiments conducted at an experimental basement located in natural soil in Ben Lomond, California. Early experiments at the structure confirmed the existence and magnitude of the model-measurement discrepancy, ensuring that it was not merely an artifact of inherently complex and poorly understood field sites. The measured soil-gas entry rate during structure depressurization was found to be an order of magnitude larger than predicted by a current three-dimensional numerical model of radon transport. The exact magnitude of the discrepancy depends on whether the arithmetic or geometric mean of the small-scale measurements of permeability is used to estimate the effective permeability of the soil. This factor is a critical empirical input to the model and was determined for the Ben Lomond site in the typical fashion using single-probe static depressurization measurements at multiple locations. The remainder of the dissertation research tests a hypothesis to explain the observed discrepancy: that soil permeability assessed using relatively …