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A sample of 2500 {Xi}{sup -} and 500 {Xi}{sup 0} hyperons, produced in {Xi}K, {Xi}K{pi}, and {Xi}K{pi}{pi} final states by K{sup -} (in H{sub 2}) at incident momenta of 1.7 to 2.7 BeV/c, has been analyzed. The data are from an exposure (K-63) of 26 events/{mu}b in the 72-inch bubble chamber; approximately 85% of the {Xi}{sup -} events and 60% of the {Xi}{sup 0} events have been analyzed. For the {Xi}, they determine the spin and decay parameters a{sub {Xi}} and {Phi}{sub {Xi}} = tan{sup -1} ({beta}{sub {Xi}}/{Gamma}{sub {Xi}}). Combining their data with 900 {Xi}{sup -} and 150 {Xi}{sup 0} events from an earlier experiment (K-72), they obtain the following results: (1) {Xi} spin - J = 1/2 favored over J = 3/2 by {approx} 2.5 standard deviations; (2) {Xi} decay parameters (assuming a{sub {Lambda}} = 0.647 {+-} 0.048) - a{sub {Xi}{sup -}} = -0.398 {+-} 0.041, {Phi}{sub {Xi}{sup -}} = 9.8{sup o} {+-} 9.0{sup o}; a{sub {Xi}{sup 0}} = -0.413 {+-} 0.104. They observe {Xi}*(1530) and {Xi}*(1817); their data are insufficient for analysis of suggested {Xi}* resonances at 1705 and 1933 MeV. They measure the {Xi}*(1530) electromagnetic mass difference {Delta}m = m({Xi}*{sup -}) = m({Xi}*{sup 0}) = 2.0 {+-} …

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The safety and optimal performance of large, commercial, light-water reactors require the knowledge at all time of the neutron-flux distribution in the core. In principle, this information can be obtained by solving the time-dependent neutron diffusion equations. However, this approach is complicated and very expensive. Sufficiently accurate, real-time calculations (time scale of approximately one second) are not yet possible on desktop computers, even with fast-running, nodal kinetics codes. A semi-experimental, nodal synthesis method which avoids the solution of the time-dependent, neutron diffusion equations is described. The essential idea of this method is to approximate instantaneous nodal group-fluxes by a linear combination of K, precomputed, three-dimensional, static expansion-functions. The time-dependent coefficients of the combination are found from the requirement that the reconstructed flux-distribution agree in a least-squares sense with the readings of J ({ge}K) fixed, prompt-responding neutron-detectors. Possible numerical difficulties with the least-squares solution of the ill-conditioned, J-by-K system of equations are brought under complete control by the use of a singular-value-decomposition technique. This procedure amounts to the rearrangement of the original, linear combination of K expansion functions into an equivalent more convenient, linear combination of R ({le}K) orthogonalized ``modes`` of decreasing magnitude. Exceedingly small modes are zeroed to eliminate any …

Mechanisms and associated energetics for adatom diffusion on the (100) and (110) surfaces of Ni, Cu, Rh, Pd, and Ag are investigated. Self-diffusion was studied on (100) and (I 10) surfaces of Ni, Cu, Pd and Ag using corrected effective medium method (CEM) and approximation to CEM used for molecular dynamics and Monte Carlo studies (MD/MC-CEM). Self-diffusion on Pd(100), Ag(100), Ni(110), Cu(110), Pd(110), and Ag(110) is accomplished by classical diffusion: the adatom hops from its equilibrium adsorption site over an intervening bridge site to an adjacent equilibrium site. Self-diffusion on Ni(100) and Cu(100) proceeds by atomic-exchange diffusion: the adatom on the surface displaces an atom in the first surface layer. Aside from explicit inclusion of the kinetic-exchange-correlation energy, it is critical to include enough movable atoms in the calculation to insure correct energetics. Distortions induced by these diffusion mechanisms, especially atomic exchange, are long ranged in surface plane, owing to small distortions of many atoms being energetically favored over large distortions of few atoms. Energetics and rates of heterogeneous adatom diffusion on the (100) surfaces of Ni, Cu, Rh, Pd, and Ag show that the final state energies differ due to variation of metallic bonding with coordination for different types …

Role of H spillover to the silica support was studied using chemisorption; a strongly bound component of spilled over H was found in the silica support which interfered with accurate measurements of active metal sites via volumetric strong H chemisorption. The volumetric chemisorption technique was modified so that measurement times were reduced from 12--36 h to 1 h. The active Ru surface was characterized means of changes in proton spin counts and NMR Knight shifts vs alkali loading. Na, K blocked the active surface of Ru metal, but Cs was pushed off by H chemisorption. The alkali promoters restricted H mobility on both metal surface and at the metal support interfaces; this is consistent with effects on Fischer-Tropsch synthesis. {sup 1}H NMR was used to study the effect of the active metal and promoter on support hydroxyl groups. The OH group density in the silica support decreased with metal and/or promoter loading, but not on a one-to-one basis; the exchange efficiency of the hydroxyls decreased with atomic size of the alkali metal. An additional downfield proton resonance was detected which was assigned to the alkali hydroxide species in the support.

The relation of structure to lack of superconductivity in Pr-Ba-Cu-O was systematically investigated. First, the phase equilibria of this system was studied to find the processing parameters which maximize the cation-site ordering between Pr and Ba ions. Second, a comparative study between superconducting Nd-Ba-Cu-0 and non- superconducting Pr-Ba-Cu-0 was performed by forming solid-solution Nd- Pr-Ba-Cu-0. The relation between structure and superconductivity in Nd{sub 1{minus}x}Pr{sub x}Ba{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} is investigated. {Tc} decreases monotonically with increasing {times} and superconductivity disappears at around x=0.3-0.4. {Tc} is enhanced by 10K when the sample is processed at an oxygen partial pressure (PO{sub 2}) of 0.01 atm, followed by oxygenation at 450C. Depression of {Tc} as a function of {times} and PO {sub 2} is explained in terms of a charge-transfer model. It is suggested that destruction of superconductivity in the RE{sub 1{minus}x}Pr{sub x}Ba{sub 2}CU{sub 3}O{sub 7{minus}{delta}} (RE=rare-earth) system can be viewed as disruption of four-fold planar coordinated Cu ions in the chain-site due to permanent occupation of extra Pr ions on Ba sites.

Kinetic data for elimination of silylene supports formation of a ``tighter`` transition state, indicating a silacyclopropene intermediate. This extends the silacyclopropene mechanism to the cyclicdialkyne system and validates the consistency of the mechanism for silylakynes, in general. Investigation into the other possible silacyclopropene product established the instability of the product. The work with silylketenes proved that an inherent difference exists between reactivity of monosilyl-substituted ketenes and polysilyl-substituted ketenes. Although the mechanism for thermal decomposition of bis(silyl)ketenes can be modified to account for the unexpected silylene elimination products, reasons for the difference are limited to speculation. The photochemistry of silylketenes has not been previously studied, so a model system does not exist for comparison with our polysilylketene work. The photochemical experimentation suggests that the photochemistry and thermochemistry of polysilylketenes is not the same. A more extensive study of the mechanism of the systems covered in this research as well as with monosilyl-substituted systems is needed.

With the ever increasing awareness of the toxicity of Pb, significant pressure has been put on the electronics industry to get the Pb out of solder. This work pertains to the development and characterization of an alloy which is Pb-free, yet retains the proven positive qualities of current Sn-Pb solders while enhancing the shortcomings of Sn-Pb solder. The solder studied is the Sn-4.7Ag-1.7Cu wt% alloy. By utilizing a variety of experimental techniques the alloy was characterized. The alloy has a melting temperature of 217{degrees}C and exhibits eutectic melting behavior. The solder was examined by subjecting to different annealing schedules and examining the microstructural stability. The effect of cooling rate on the microstructure of the solder was also examined. Overall, this solder alloy shows great promise as a viable alternative to Pb-bearing solders and, as such, an application for a patent has been filed.

The fundamental and practical aspects are described for extracting ions from atmospheric pressure plasma sources into an analytical mass spectrometer. Methodologies and basic concepts of inductively coupled plasma mass spectrometry (ICP-MS) are emphasized in the discussion, including ion source, sampling interface, supersonic expansion, slumming process, ion optics and beam focusing, and vacuum considerations. Some new developments and innovative designs are introduced. The plasma extraction process in ICP-MS was investigated by Langmuir measurements in the region between the skimmer and first ion lens. Electron temperature (T{sub e}) is in the range 2000--11000 K and changes with probe position inside an aerosol gas flow. Electron density (n{sub e}) is in the range 10{sup 8}--10{sup 10} {sup {minus}cm }at the skimmer tip and drops abruptly to 10{sup 6}--10{sup 8} cm{sup {minus}3} near the skimmer tip and drops abruptly to 10{sup 6}--10{sup 8} cm{sup {minus}3} downstream further behind the skimmer. Electron density in the beam leaving the skimmer also depends on water loading and on the presence and mass of matrix elements. Axially resolved distributions of electron number-density and electron temperature were obtained to characterize the ion beam at a variety of plasma operating conditions. The electron density dropped by a factor of 101 …

Two reactions which are important to coal liquefaction include intermolecular transfer and the elimination of two hydrogen atoms. We have designed several model reactions to probe the viability of several hydrogen transfer and elimination pathways. This report described studies on these reactions using organic model compounds.

{sup 27}Al and {sup 61,65}Cu NMR measurements are reported for powder samples of stable AlCuFe and AlCuRu icosahedral quasicrystals and their crystalline approximants, and for a AlPdMn single grain quasicrystal. Furthermore, {sup 27}Al NQR spectra at 4.2 K have been observed in the AlCuFe and AlCuRu samples. From the quadrupole perturbed NMR spectra at different magnetic fields, and from the zero field NQR spectra, a wide distribution of local electric field gradient (EFG) tensor components and principal axis system orientations was found at the Al site. A model EFG calculation based on a 1/1 AlCuFe approximant was successful in explaining the observed NQR spectra. It is concluded that the average local gradient is largely determined by the p-electron wave function at the Al site, while the width of the distribution is due to the lattice contribution to the EFG. Comparison of {sup 63}Cu NMR with {sup 27}Al NMR shows that the EFG distribution at the two sites is similar, but that the electronic contribution to the EFG is considerably smaller at the Cu site, in agreement with a more s-type wave function of the conduction electrons.

Combined cross section times branching fraction limits are given for {Sigma}{sub c}{sup +}{sup +} {r_arrow} {Lambda}{sub c}{sup +}{pi}{sup +} and {Sigma}{sub c}{sup 0} {r_arrow} {Lambda}{sub c}{sup +}{pi}{sup {minus}} where {Lambda}{sub c}{sup +} {r_arrow} {Sigma}{sub s}{sup {plus_minus}}{pi}{sup {plus_minus}}{pi}{sup +}. The {Lambda}{sub c}{sup +} is reconstructed with partial information on the {Sigma}{sub s}; the missing {Sigma}{sub s} momentum is established through momentum conservation imposed by a constrained fit. The data are of {pi}{sup {minus}} beam interactions at 250 GeV from Fermilab experiment E769.

Photosynthesis is a complex process which results in the conversion of solar radiation into chemical energy. This chemical energy is then used as the free energy source for all living organisms. In its basic form, photosynthesis can be described as the light-activated synthesis of carbohydrates from the simple molecules of water and carbon dioxide: 6H{sub 2}O + 6 CO{sub 2} light C{sub 6}H{sub 12}O{sub 6} + 6 O{sub 2} This basic mechanism actually requires numerous reaction steps. The two primary steps being: the capture of light by pigment molecules in light-harvesting antenna complexes and the transfer of this captured energy to the so-called photochemical reaction center. While the preferred pathway for energy absorbed by the chromophores in the antenna complexes is transfer to the reaction center, energy can be lost to competing processes such as internal conversion or radiative decay. Therefore, the energy transfer must be rapid, typically on the order of picoseconds, to successfully compete. The focus of the present work is on the construction of light-harvesting antenna complexes incorporating modular pigment-proteins.

The single crystals of TiNiSn and polycrystalline PtMnSb were grown by the flux and melt cooling method. Their lattice parameters and structures were determined by x-ray diffraction. The effect of impurities on the growth of TiNiSn single crystals was investigated. It was found that the concentration of chlorine plays a key role in determining the chemical composition of the phases that are formed. The heat capacity and magnetic susceptibility of TiNiSn was measured in a temperature range from 4.7 K to room temperature. Magnetic measurements show that the TiNiSn is paramagnetic, and that it does not order magnetically.

Scanning probe microscopy (SPM) offers access to the structural and material properties of interfaces, and when combined with macroscopic characterization techniques results in a powerful interfacial development tool. However, the relative infancy of SPM techniques has dictated that initial investigations concentrate on model interfacial systems as benchmarks for testing the control and characterization capabilities of SPM. One such family of model interfacial systems results from the spontaneous adsorption of alkyl thiols to gold. This dissertation examines the application of SPM to the investigation of the interfacial properties of these alkyl thiolate monolayers. Structural investigations result in a proposed explanation for counterintuitive correlations between substrate roughness and heterogeneous electron transfer barrier properties. Frictional measurements are used for characterization of the surface free energy of a series of end-group functionalized monolayers, as well as for the material properties of monolayers composed of varying chain length alkyl thiols. Additional investigations used these characterization techniques to monitor the real-time evolution of chemical and electrochemical surface reactions. The results of these investigations demonstrates the value of SPM technology to the compositional mapping of surfaces, elucidation of interfacial defects, creation of molecularly sized chemically heterogeneous architectures, as well as to the monitoring of surface reactions. However, …

The Full Potential Linear Augmented Plane Wave (FPLAPW or FLAPW) method is used for a spin-polarized band calculation for ordered Fe{sub 3}Pt. As major purpose, the momentum distributions of the spin-polarized electrons are calculated and compared with results from a magnetic Compton scattering measurement. To get related information, the electronic behavior is also analyzed by examining the partial densities of states and the spatial electron distributions; the role of alloying effects is then explored by studying the electrons in some related alloys: Fe{sub 3}Ni, Fe{sub 3}Pd, Ni{sub 3}Pt and Co{sub 3}Pt.

Inductively coupled plasma mass spectrometry (ICP-MS) is the technique of choice for rapid, high precision, semiquantitative elemental and isotopic analysis for over 70 elements. Less than 20 years after the first mass spectrum was obtained by ICP-MS, this technique has applications in clinical chemistry, geochemistry, the semiconductor industry, the nuclear industry, environmental chemistry, and forensic chemistry. The determination of many elements, though, by ICP-MS is complicated by spectral interferences from background species, interelement spectral overlaps, and polyatomic ions of matrix elements. The emphasis of this thesis is the unique applications of solvent removal using cryogenic and membrane desolvation. Chapter 1 is a general introduction providing background information concerning the need for these methods and some information about the methods themselves. Chapter 5 discusses general conclusions and general observations pertaining to this work. Chapters 2, 3, and 4 have been processed separately for inclusion on the database. Chapter 2 describes a method to screen urine samples for vanadium using cryogenic desolvation. Chapter 3 compares solvent removal by cryogenic and membrane desolvation. Chapter 4 describes the use of cool plasma conditions for the determination of potassium in the presence of excess sodium by ICP-MS.

Methyltrioxorhenium (MTO) catalyzes the desulfurization of thiiranes by triphenylphosphine. Enormous enhancement in rate is observed when the catalyst is pretreated with hydrogen sulfide prior to the reaction. Using 2-mercaptomethylthiophenol as a ligand, the author synthesized several model complexes to study the mechanism of this reaction. With suitable model systems, they were able to show that the active catalyst is a Re(V) species. The reactions are highly stereospecific and very tolerant to functional groups. As part of the studies, he synthesized and crystallographically characterized the first examples of neutral terminal and bridging Re(V)sulfidocomplexes. Some of these complexes undergo fast oxygen atom transfer reactions with organic and inorganic oxidants. Studies on these model complexes led them to the discovery that MTO catalyzes the selective oxidation of thiols to disulfides. This report contains the Introduction; ``Chapter 6: Isomerization of Propargylic Alcohols to Enones and Enals Catalyzed by Methylrhenium Trioxide``; and Conclusions.

n-Butane selective oxidation over the VPO catalyst to maleic anhydride is the first and only commercialized process of light alkane selective oxidation. The mechanism of this reaction is still not well known despite over twenty years of extensive studies, which can partially be attributed to the extreme difficulties to characterize catalytic reactions real-time under typical reaction conditions. In situ spectroscopic characterization techniques such as Infrared spectroscopy and laser Raman spectroscopy were used in the current mechanistic investigations of n-butane oxidation over VPO catalysts. To identify the reaction intermediates, oxidation of n-butane, 1,3-butadiene and related oxygenates on the VPO catalyst were monitored using FTIR spectroscopy under transient conditions. n-Butane was found to adsorb on the VPO catalyst to form olefinic species, which were further oxidized to unsaturated, noncyclic carbonyl species. The open chain dicarbonyl species then experienced cycloaddition to form maleic anhydride. VPO catalyst phase transformations were investigated using in situ laser Raman spectroscopy. This report contains Chapter 1: General introduction; Chapter 2: Literature review; and Chapter 5: Conclusion and recommendations.

This dissertation focuses on the development of methods for stable isotope metabolic tracer studies in living systems using inductively coupled plasma single and dual quadrupole mass spectrometers. Sub-nanogram per gram levels of molybdenum (Mo) from human blood plasma are isolated by the use of anion exchange alumina microcolumns. Million-fold more concentrated spectral and matrix interferences such as sodium, chloride, sulfate, phosphate, etc. in the blood constituents are removed from the analyte. The recovery of Mo from the alumina column is 82 {+-} 5% (n = 5). Isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS) is utilized for the quantitative ultra-trace concentration determination of Mo in bovine and human blood samples. The average Mo concentration in reference bovine serum determined by this method is 10.2 {+-} 0.4 ng/g, while the certified value is 11.5 {+-} 1.1 ng/g (95% confidence interval). The Mo concentration of one pool of human blood plasma from two healthy male donors is 0.5 {+-} 0.1 ng/g. The inductively coupled plasma twin quadrupole mass spectrometer (ICP-TQMS) is used to measure the carbon isotope ratio from non-volatile organic compounds and bio-organic molecules to assess the ability as an alternative analytical method to gas chromatography combustion isotope ratio mass spectrometry …

Measurements of electrical resistivity as a function of temperature from 25 to 1,500 C were conducted on polycrystalline samples in the Mo-Si-B system. Single phase, or nearly single phase, samples were prepared for the following phases: Mo{sub 3}Si, Mo{sub 5}SiB{sub 2}, Mo{sub 5}Si{sub 3}B{sub x}, MoB, MoSi{sub 2}, and Mo{sub 5}Si{sub 3}. Thesis materials all exhibit resistivity values within a narrow range(4--22 x 10{sup {minus}7}{Omega}-m), and the low magnitude suggests these materials are semi-metals or low density of states metals. With the exception of MoSi{sub 2}, all single phase materials in this study were also found to have low temperature coefficient of resistivity(TCR) values. These values ranged from 2.10 x 10{sup {minus}10} to 4.74 x 10{sup {minus}10}{Omega}-m/{degree} C, and MoSi{sub 2} had a TCR of 13.77 x 10{sup {minus}10}{Omega}-m/{degree} C. The results from the single phase sample measurements were employed in a natural log rule-of-mixtures model to relate the individual phase resistivity values to those of multiphase composites. Three Mo-Si-B phase regions were analyzed: the binary Mo{sub 5}Si{sub 3}-MoSi{sub 2} system, the ternary phase field Mo{sub 5}Si{sub 3}B{sub x}MoB-MoSi{sub 2}, and the Mo{sub 3}Si-Mo{sub 5}SiB{sub 2}-Mo{sub 5} Si{sub 3}B{sub x} ternary region. The experimental data for samples in each of …