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Description: The potential for contamination of groundwater by organic pollutants leached from in-situ spent shale was studied in a series of laboratory leaching experiments. Both batch-mode and continuous-flow column experiments were conducted to study the leaching phenomenon. Experimental variables included retorting characteristics of spent shale, leaching time, initial quality of leach water, temperature of leach water, and particle size of spent shale. Several unique samples of spent shale were examined during the eaching experiments, including spent shale samples produced during combustion retorting, inert gas retorting, and combustion retorting employing recycle gas. The solid-phase organic carbon content of spent shale samples ranged from 0.2 to 3.9 percent by weight. Leachate derived from the batch-mode experiments was analyzed for organic carbon, organic nitrogen, phenols, and acid/base/netral fractions. The highest levels of organic carbon were detected in leachate derived from spent shale produced during either inert gas retorting or combstion retorting using recycle gas. The highest levels of phenols were observed in leachate obtained from spent shale produced during inert gas retorting; significant levels of organic nitrogen were also detected in various leachate samples. The most predominant organic fraction measured in leachate samples was the neutral fraction associated with spent shale produced during inert gas retorting. Batch-mode experimental results describing equilibrium conditions were analyzed according to the Freundlich and langmuir isotherm models. Those models were found to be appropriate for describing equilibrium relationships between leachate and spent shale produced during inert gas retorting. To a somewhat lesser extent, these same models were found to be appropriate for modeling equilibrium relationships involving combustion-retorted spent shale. A kinetic analysis of results derived from the continuous-flow column experiments was conducted in an attempt to identify a rate-controlling mass transfer mechanism. Internal diffusion appeared to be the most likely rate-limiting mechanism for leaching from combustion-retorted spent shale. In ...
Date: June 1, 1978
Creator: Amy, Gary L.
Partner: UNT Libraries Government Documents Department

Measurement of Single Spin Asymmetries in Semi-Inclusive Deep Inelastic Scattering Reaction n↑ ( e,e' pi{sup +}) X at Jefferson Lab

Description: What constitutes the spin of the nucleon? The answer to this question is still not completely understood. Although we know the longitudinal quark spin content very well, the data on the transverse quark spin content of the nucleon is still very sparse. Semi-inclusive Deep Inelastic Scattering (SIDIS) using transversely polarized targets provide crucial information on this aspect. The data that is currently available was taken with proton and deuteron targets. The E06-010 experiment was performed at Jefferson Lab in Hall-A to measure the single spin asymmetries in the SIDIS reaction n↑(e, e′π{sup ±}/K{sup ±})X using transversely polarized {sup 3}He target. The experiment used the continuous electron beam provided by the CEBAF accelerator with a beam energy of 5.9 GeV. Hadrons were detected in a high-resolution spectrometer in coincidence with the scattered electrons detected by the BigBite spectrometer. The kinematic coverage focuses on the valence quark region, x = 0.19 to 0.34, at Q{sup 2} = 1.77 to 2.73 (GeV/c){sup 2}. This is the first measurement on a neutron target. The data from this experiment, when combined with the world data on the proton and the deuteron, will provide constraints on the transversity and Sivers distribution functions on both the u and d-quarks in the valence region. In this work we report on the single spin asymmetries in the SIDIS n↑(e, e′π{sup +})X reaction.
Date: June 1, 2010
Creator: Allada, Kalyan
Partner: UNT Libraries Government Documents Department

Measurement of single-target spin asymmetries in the electroproduction of negative pions in the semi-inclusive deep inelastic reaction n{up_arrow}(e,e'{pi}{sup -})X on a transversely polarized {sup 3}He target

Description: The experiment E06010 measured the target single spin asymmetry (SSA) in the semiinclusive deep inelastic (SIDIS) n{up_arrow}(e, e'{pi}{sup -})X reaction with a transversely polarized {sup 3}He target as an e#11;ective neutron target. This is the very #12;rst independent measurement of the neutron SSA, following the measurements at HERMES and COMPASS on the proton and the deuteron. The experiment acquired data in Hall A at Je#11;erson Laboratory with a continuous electron beam of energy 5.9 GeV, probing the valence quark region, with x = 0.13 {rt_arrow} 0.41, at Q{sup 2} = 1.31 {rt_arrow} 3.1 GeV{sup 2}. The two contributing mechanisms to the measured asymmetry, viz, the Collins effect and the Sivers effect can be realized through the variation of the asymmetry as a function of the Collins and Sivers angles. The neutron Collins and Sivers moments, associated with the azimuthal angular modulations, are extracted from the measured asymmetry for the very #12;first time and are presented in this thesis. The kinematics of this experiment is comparable to the HERMES proton measurement. However, the COMPASS measurements on deuteron and proton are in the low-x region. The results of this experiment are crucial as the first step toward the extraction of quark transversity and Sivers distribution functions in SIDIS. With the existing results on proton and deuteron, these new results on neutron will provide powerful constraints on the transversity and Sivers distributions of both the u and d-quarks in the valence region.
Date: June 1, 2010
Creator: Dutta, Chiranjib
Partner: UNT Libraries Government Documents Department

Developing nanotechnology for biofuel and plant science applications

Description: This dissertation presents the research on the development of mesoporous silica based nanotechnology for applications in biofuels and plant science. Mesoporous silica nanoparticles (MSNs) have been the subject of great interest in the last two decades due to their unique properties of high surface area, tunable pore size and particle morphology. The robust nature of the silica framework is easily functionalized to make the MSNs a promising option for selective separations. Also, the independent channels that form the pores of MSN have been exploited in the use of particles as platforms for molecular delivery. Pore size and organic functionality are varied to identify the ideal adsorbent material for free fatty acids (FFAs). The resulting material is able to sequester FFAs with a high degree of selectivity from a simulated solution and microalgal oil. The recyclability and industrial implications are also explored. A continuation of the previous material, further tuning of MSN pore size was investigated. Particles with a smaller diameter selectively sequester polyunsaturated free fatty acids (PUFAs) over monounsaturated FFAs and saturated FFAs. The experimental results were verified with molecular modeling. Mesoporous silica nanoparticle materials with a pore diameter of 10 nm (MSN-10) were decorated with small gold nanoparticles. The resulting materials were shown to deliver proteins and DNA into plant cells using the biolistic method.
Date: June 20, 2012
Creator: Valenstein, Justin
Partner: UNT Libraries Government Documents Department

Electroproduction de pions neutres dans le Hall A au Jefferson Laboratory

Description: The past decade has seen a strong evolution of the study of the hadron structure through exclusive processes, allowing to access to a more complete description of this structure. Exclusive processes include DVCS (Deeply Virtual Compton Scattering) as well as hard exclusive meson production. This document is particularly focussed on the latter, and more particularly on exclusive neutral pion production. In this thesis is described the analysis of triple coincidence events H(e, e'{gamma}{gamma})X, which were a consequent by-product of the DVCS experiment which occured during Fall 2004 at Jefferson Lab Hall A, to extract the ep {yields} ep{pi}{sup 0} cross section. This cross section has been measured at two values of four-momentum transfer Q{sup 2} = 1.9 GeV{sup 2} and Q{sup 2} = 2.3 GeV{sup 2}. The statistical precision for these measurements is achieved at better than 5 %. The kinematic range allows to study the evolution of the extracted cross section as a function of Q{sup 2} and W. Results are be confronted with Regge inspired calculations and Generalized (GPD) predictions. An intepretation of our data within the framework of semi-inclusive deep inelastic scattering is also discussed.
Date: June 1, 2010
Creator: Fuchey, Eric
Partner: UNT Libraries Government Documents Department

Cellular membrane trafficking of mesoporous silica nanoparticles

Description: This dissertation mainly focuses on the investigation of the cellular membrane trafficking of mesoporous silica nanoparticles. We are interested in the study of endocytosis and exocytosis behaviors of mesoporous silica nanoparticles with desired surface functionality. The relationship between mesoporous silica nanoparticles and membrane trafficking of cells, either cancerous cells or normal cells was examined. Since mesoporous silica nanoparticles were applied in many drug delivery cases, the endocytotic efficiency of mesoporous silica nanoparticles needs to be investigated in more details in order to design the cellular drug delivery system in the controlled way. It is well known that cells can engulf some molecules outside of the cells through a receptor-ligand associated endocytosis. We are interested to determine if those biomolecules binding to cell surface receptors can be utilized on mesoporous silica nanoparticle materials to improve the uptake efficiency or govern the mechanism of endocytosis of mesoporous silica nanoparticles. Arginine-glycine-aspartate (RGD) is a small peptide recognized by cell integrin receptors and it was reported that avidin internalization was highly promoted by tumor lectin. Both RGD and avidin were linked to the surface of mesoporous silica nanoparticle materials to investigate the effect of receptor-associated biomolecule on cellular endocytosis efficiency. The effect of ligand types, ligand conformation and ligand density were discussed in Chapter 2 and 3. Furthermore, the exocytosis of mesoporous silica nanoparticles is very attractive for biological applications. The cellular protein sequestration study of mesoporous silica nanoparticles was examined for further information of the intracellular pathway of endocytosed mesoporous silica nanoparticle materials. The surface functionality of mesoporous silica nanoparticle materials demonstrated selectivity among the materials and cancer and normal cell lines. We aimed to determine the specific organelle that mesoporous silica nanoparticles could approach via the identification of harvested proteins from exocytosis process. Based on the study of endo- and exocytosis behavior ...
Date: June 21, 2012
Creator: Fang, I-Ju
Partner: UNT Libraries Government Documents Department

Controlling atomistic processes on Pb films via quantum size effects and lattice rotation

Description: The two main techniques used to record the data in this dissertation were Spot Profile Analysis - Low Energy Electron Diffraction (SPA-LEED) and Scanning Tunneling Microscopy (STM). A specific data analysis technique for LEED data called G(S) curves is described in depth. G(S) curves can provide a great deal of structural information about the surface; including step heights, island size, and island separation. The effects of quantum size effects (QSE) on the diffusion and critical island sizes of Pb and In on Pb #12;films are reported. Pb depositions on the 2D In phases {radical}3 and {radical}31 to see how the phases affect the Pb growth and its strong QSE are reported.
Date: June 14, 2012
Creator: Binz, Steven
Partner: UNT Libraries Government Documents Department

Search for Resonances in the Photoproduction of Proton-Antiproton Pairs

Description: Results are reported on the reaction {gamma}p {yields} p{bar p}p with beam energy in the range 4.8-5.5 GeV. The data were collected at the Thomas Jefferson National Accelerator Facility in CLAS experiment E01-017(G6C). The focus of this study is an understanding of the mechanisms of photoproduction of proton-antiproton pairs, and to search for intermediate resonances, both narrow and broad, which decay to p{bar p}. The total measured cross section in the photon energy range 4.8-5.5 GeV is {sigma} = 33 {+-} 2 nb. Measurement of the cross section as a function of energy is provided. An upper limit on the production of a narrow resonance state previously observed with a mass of 2.02 GeV/c{sup 2} is placed at 0.35 nb. No intermediate resonance states were observed. Meson exchange production appears to dominate the production of the proton-antiproton pairs.
Date: June 30, 2006
Creator: Stokes, Burnham
Partner: UNT Libraries Government Documents Department

Unorthodox theoretical methods

Description: The use of the ReaxFF force field to correlate with NMR mobilities of amine catalytic substituents on a mesoporous silica nanosphere surface is considered. The interfacing of the ReaxFF force field within the Surface Integrated Molecular Orbital/Molecular Mechanics (SIMOMM) method, in order to replicate earlier SIMOMM published data and to compare with the ReaxFF data, is discussed. The development of a new correlation consistent Composite Approach (ccCA) is presented, which incorporates the completely renormalized coupled cluster method with singles, doubles and non-iterative triples corrections towards the determination of heats of formations and reaction pathways which contain biradical species.
Date: June 20, 2012
Creator: Nedd, Sean
Partner: UNT Libraries Government Documents Department

Finite element method for neutron diffusion problems in hexagonal geometry

Description: The use of the finite element method for solving two-dimensional static neutron diffusion problems in hexagonal reactor configurations is considered. It is investigated as a possible alternative to the low-order finite difference method. Various piecewise polynomial spaces are examined for their use in hexagonal problems. The central questions which arise in the design of these spaces are the degree of incompleteness permissible and the advantages of using a low-order space fine-mesh approach over that of a high-order space coarse-mesh one. There is also the question of the degree of smoothness required. Two schemes for the construction of spaces are described and a number of specific spaces, constructed with the questions outlined above in mind, are presented. They range from a complete non-Lagrangian, non-Hermite quadratic space to an incomplete ninth order space. Results are presented for two-dimensional problems typical of a small high temperature gas-cooled reactor. From the results it is concluded that the space used should at least include the complete linear one. Complete spaces are to be preferred to totally incomplete ones. Once function continuity is imposed any additional degree of smoothness is of secondary importance. For flux shapes typical of the small high temperature gas-cooled reactor the linear space fine-mesh alternative is to be preferred to the perturbation quadratic space coarse-mesh one and the low-order finite difference method is to be preferred over both finite element schemes. (auth)
Date: June 1, 1975
Creator: Wei, T.Y.C. & Hansen, K.F.
Partner: UNT Libraries Government Documents Department

Study of Quasielastic 1p-shell proton Knockout in the {sup 16}O (e,e'p) reaction at Q{sup 2}=0.8 (GeV/c){sup 2}

Description: Coincidence cross sections and the structure functions R{sub L+TT},#2; R{sub T} and R{sub LT} have been obtained for the quasielastic #2;#3;{sup 16}O(#7;e,#2; e'p)#8; reaction with the proton knocked out from the #2;1p{sub 1/2}#2;#2;#4; and #2;1p{sub 3/2}#5;#2;#4; states in perpendicular kinematics. The nominal energy transfer #3;{omega} was 439#11; MeV#4; the nominal Q{sup 2}#4; was 0.8 (#7;GeV/#14;c){sup 2}#8;#4; and the kinetic energy of knocked-#15;out proton was 427#3;#16; MeV. The data was taken in Hall A#4; Je#17;erson Laboratory#4; using two high resolution spectrometers to detect electrons and protons respectively. Nominal beam energies 845#18; MeV#4;, #2;#19;1645#18; MeV#4; and #3;2445#18; MeV were employed. For each beam energy,#4; the momentum and angle of electron arm were #6;fixed,#4; while the angle between the proton momentum and the momentum transfer {vector #4;q} was varied to map out the missing momentum. R{sub LT} was separated out to ~350 MeV#14;/c in missing momentum. R{sub L+TT} and R{sub T} were separated out to #2;#3;~280 MeV/#14;c in missing momentum. R{sub L} and R{sub T} were separated at a missing momentum of #18;#3;52.5#18; MeV/#14;c for the data taken with hadron arm along #4;{vector q}. The measured cross sections and response functions agree with both relativistic and non#15;relativistic DWIA calculations employing spectroscopic factors between #19;60-75% for 1#2;p{sub 1/2}#2;#2;#4; and 1#2;p{sub 3/2}#5;#2;#4; states. The left-#15;right asymmetry does not support the non#15;-relativistic DWIA calculation using the Weyl gauge. Also#4; the left-#15;right asymmetry measurement favors the relativistic calculation. This thesis describes the details of the experimental setup#4;, the calibration of the spectrometers,#4; the techniques used in the data analysis to derive the fi#6;nal cross sec#15;tions as well as the response functions#4; and the comparison of the results with the theoretical calculations.
Date: June 1, 1999
Creator: Gao, Juncai
Partner: UNT Libraries Government Documents Department


Description: High resolution, proton decoupled {sup 13}C nmr are observed for a series of neat nematic liquid crystals, the p-alkoxyazoxybenzenes, and a smectic-A liquid crystal, diethylazoxydibenzoate in a magnetic field of 23 kG. The (uniaxial) order parameters S = <P{sub 2}(cos{theta})> are found to be about 0.4 and 0.9 for the nematic and smectic-A phase respectively at the clearing points. The order parameter increases with decreasing temperature in the nematic phase but is constant, or nearly so, with temperature in the smectic-A phase. In the nematic series studied, the ordering exhibits an even-odd alternation along the series and qualitative agreement with a recent theory due to Marcelja is found. In both phases, the spectra show that the molecule rotates rapidly about its long axis. Tentative conclusions about molecular conformational motion and {sup 14}N spin relaxation are presented for both nematic and smectic-A phases. In the smectic-A phase, the sample is rotated about an axis perpendicular to H{sub 0} and the resulting spectra are discussed. The theory of observed chemical shifts in liquid crystals is treated in an appendix. Equations are derived which relate the nmr spectra of liquid-crystals to the order parameters. A model for the smectic-C phase due to Luz and Meiboom and Doane is described and lineshapes are determined on the basis of this model for special cases. Experiments on smectic-C liquid crystals are currently underway for comparison with the theory. Also treated in an appendix is the dependence of the order parameters on the molecular potential which give rise to the various degrees of order in the different liquid crystalline phases. To a good approximation the functional dependence of the order parameters on the molecular potential is shown to be a simple one in the limit of small tilt angle in the smectic-C phase.
Date: June 1, 1975
Creator: Allison, Stuart
Partner: UNT Libraries Government Documents Department

Applications of time-differential perturbed angular correlations to the study of solids

Description: Time-differential perturbed angular correlation techniques were applied to a systematic study of insulating antiferromagnets and rare-earth intermetallic alloys doped with either /sup 111m/Cd or $sup 111$In. The internal magnetic fields and electric field gradients at the radioactive nucleus are deduced from the experimentally measured perturbation factors. The analysis of fluoride, chloride, oxide, and sulfide data shows the systematic variation of the observed supertransferred hyperfine fields with the intervening anion covalency and allows extraction of covalency parameters after the adoption of a simple model. A comparison of the transferred hyperfine field data between fluoride perovskites and the corresponding quadratic layer compounds produces a value for the zero- point spin deviation in magnetically two-dimensional antiferromagnets which is in qualitative agreement with existing theoretical estimates. Paramagnetic shifts due to transferred hyperfine field and field-induced spin-flopping have also been observed. By careful temperature regulation the temperature dependence of the sublattice magnetization can be plotted next to a diamagnetic impurity in RbMnF$sub 3$ and MnF$sub 2$. A shift in the transferred hyperfine field at Cd doped into MnS has been measured under the application of moderate pressures up to 22 kbar. Analysis of the electric field gradients at the In and Sn sites in the rare-earth series RIn$sub 3$ and RSn$sub 3$ as functions of temperature and pressure is the basis of a check for valence fluctuations in certain of these alloys. (auth)
Date: June 1, 1975
Creator: Schwartz, G.P.
Partner: UNT Libraries Government Documents Department

Structural Investigations of Surfaces and Orientation-SpecificPhenomena in Nanocrystals and Their Assemblies

Description: Studies of colloidal nanocrystals and their assemblies are presented. Two of these studies concern the atomic-level structural characterization of the surfaces, interfaces, and interiors present in II-VI semiconductor nanorods. The third study investigates the crystallographic arrangement of cobalt nanocrystals in self-assembled aggregates. Crystallographically-aligned assemblies of colloidal CdSe nanorods are examined with linearly-polarized Se-EXAFS spectroscopy, which probes bonding along different directions in the nanorod. This orientation-specific probe is used, because it is expected that the presence of specific surfaces in a nanorod might cause bond relaxations specific to different crystallographic directions. Se-Se distances are found to be contracted along the long axis of the nanorod, while Cd-Se distances display no angular dependence, which is different from the bulk. Ab-initio density functional theory calculations upon CdSe nanowires indicate that relaxations on the rod surfaces cause these changes. ZnS/CdS-CdSe core-shell nanorods are studied with Se, Zn, Cd, and S X-ray absorption spectroscopy (XAS). It is hypothesized that there are two major factors influencing the core and shell structures of the nanorods: the large surface area-to-volume ratio, and epitaxial strain. The presence of the surface may induce bond rearrangements or relaxations to minimize surface energy; epitaxial strain might cause the core and shell lattices to contract or expand to minimize strain energy. A marked contraction of Zn-S bonds is observed in the core-shell nanorods, indicating that surface relaxations may dominate the structure of the nanorod (strain might otherwise drive the Zn-S lattice to accommodate the larger CdS or CdSe lattices via bond expansion). EXAFS and X-ray diffraction (XRD) indicate that Cd-Se bond relaxations might be anisotropic, an expected phenomenon for a rod-shaped nanocrystal. Ordered self-assembled aggregates of cobalt nanocrystals are examined with transmission electron microscopy (TEM) and selected-area electron diffraction (SAED). SAED patterns from multilayered assemblies show that the nanocrystals have preferred crystallographic orientations. ...
Date: June 17, 2006
Creator: Aruguete, Deborah Michiko
Partner: UNT Libraries Government Documents Department

Properties of the eta prime meson

Description: The {eta}'(958) meson has been studied in the reaction K{sup -}p {yields} {Lambda}{eta}', with K{sup -} beam momenta ranging from 1.70 to 2.65 Gev/c. The Dalitz plots of {eta}' decay into {pi}{sup +}{pi}{sup -}{eta} and {pi}{sup +}{pi}{sup -}{gamma} have been examined, and from them we have determined that the most likely quantum numbers of the {eta}' are I{sup G}J{sup P} = 0{sup +}0{sup -}, although J{sup P} = 2{sup -} cannot be completely ruled out. They have also shown that the decay into {pi}{sup +}{sup -}{gamma} is mediated by the decay {eta}' {yields} {rho}{sup o}{gamma}. An examination of the production process has yielded further evidence for the J{sup P} = 0{sup -} assignment and suggested that the process takes place via K*(891) exchange in the t channel. Branching fractions and cross sections have been determined, and finally a search for a negatively charged {eta}' in the deuterium reaction K{sup -}d {yields} p{Lambda}{eta}' has confirmed the I = 0 assignment for the {eta}'.
Date: June 4, 1969
Creator: Rittenberg, Alan
Partner: UNT Libraries Government Documents Department


Description: The iodine species formed either by adding hypochlorite to a basic iodide solution or by adding triiodide to sodium hydroxide, was identified as hypoiodite ion. The absorption spectrum of IO{sup -} was investigated in the wavelength range from 450 m{micro} to 280 m{micro}. The kinetics of the reaction I{sup -} + ClO{sup -} = IO{sup -} + Cl{sup -} was studied spectrophotometrically in alkaline solution. The forward rate law was found to be d(IO{sup -})/dt = k(I{sup -})(ClO{sup -})/OH{sup -}. At 25 C and an ionic strength of 1.00 M, k is 61 {+-} 3 sec{sup -1}. It was found spectrophotometrically that for certain ratios of the initial iodide to hydroxide concentrations, there was evidence of the presence of I{sub 3}{sup -}, I{sub 2}OH{sup -}, and I{sub 2}O{sup 2-} along with IO{sup -}. The equilibrium constants between IO{sup -} and these three species were evaluated by a graphical method. The formal potential of the cell: Pt:H{sub 2}:1 M NaOH : 1M NaOH, KI, NaIO : Au was found to be 1.297 v at 25 C. The equilibrium constant, K{sub 2} = (I{sub 3}{sup -})(OH{sup -}){sup 2}/(IO{sup -})(I{sup -}){sup 2}, of the reaction IO{sup -} + 2I{sup -} + H{sub 2}O {l_reversible} I{sub 3}{sup -} + 2OH{sup -} calculated from emf measurements agreed well with that from spectrophotometric measurements. The ionization constant of HOI was calculated to be 2.3 x 10{sup -11} at 25 C.
Date: June 2, 1958
Creator: Chia, Yuan-tsan.
Partner: UNT Libraries Government Documents Department

Jet Production in the Central Rapidity Region in 1.8 TeV Proton and Antiproton Collisions

Description: In this thesis we study the jet production cross section in the central rapidity region in {bar p}p collisions at a center of mass energy of 1.8 TeV. The pseudo-rapidity {eta} is defined as {eta} {triple_bond} -ln(tan({theta}/2)), where {theta} is the angle between the directions of the jet momentum and the proton beam. We will call the region -0.7 < {eta} < 0.7 the 'central rapidity' region by definition. The goal of this thesis is to determine two kinds of differential cross sections for jet production: an inclusive jet Et distribution d{sigma}/dEt, and the distribution in invariant mass d{sigma}/dM{sub JJ} of two jet systems. These spectra serve to check the strong interaction theory, and thus to look for new phenomena, at the highest available energy. The strong interaction theory will be discussed.
Date: June 1, 1989
Creator: Tsai, Yeong-Dong & U., /Chicago
Partner: UNT Libraries Government Documents Department

Search for a Standard Model Higgs Boson with a Dilepton and Missing Energy Signature

Description: The subject of this thesis is the search for a standard model Higgs boson decaying to a pair of W bosons that in turn decay leptonically, H {yields} W{sup +}W{sup -} {yields} {bar {ell}}{nu}{ell}{bar {nu}}. This search is performed considering events produced in p{bar p} collisions at {radical}s = 1.96 TeV, where two oppositely charged lepton candidates (e{sup +}e{sup -}, e{sup {+-}}{mu}{sup {-+}}, or {mu}{sup +}{mu}{sup -}), and missing transverse energy, have been reconstructed. The data were collected with the D0 detector at the Fermilab Tevatron collider, and are tested against the standard model predictions computed for a Higgs boson with mass in the range 115-200 GeV. No excess of events over background is observed, and limits on Standard Model Higgs boson production are determined. An interpretation of these limits within the hypothesis of a fourth-generation extension to the standard model is also given. The overall analysis scheme is the same for the three dilepton pairs being considered (e{sup +}e{sup -}, e{sup {+-}}{mu}{sup {-+}}, or {mu}{sup +}{mu}{sup -}); this thesis, however, describes in detail the study of the dimuon final state.
Date: June 1, 2011
Creator: Gerbaudo, Davide & U., /Princeton
Partner: UNT Libraries Government Documents Department

Low Temperature Constrained Sintering of Cerium Gadolinium OxideFilms for Solid Oxide Fuel Cell Applications

Description: Cerium gadolinium oxide (CGO) has been identified as an acceptable solid oxide fuel cell (SOFC) electrolyte at temperatures (500-700 C) where cheap, rigid, stainless steel interconnect substrates can be used. Unfortunately, both the high sintering temperature of pure CGO, >1200 C, and the fact that constraint during sintering often results in cracked, low density ceramic films, have complicated development of metal supported CGO SOFCs. The aim of this work was to find new sintering aids for Ce{sub 0.9}Gd{sub 0.1}O{sub 1.95}, and to evaluate whether they could be used to produce dense, constrained Ce{sub 0.9}Gd{sub 0.1}O{sub 1.95} films at temperatures below 1000 C. To find the optimal sintering aid, Ce{sub 0.9}Gd{sub 0.1}O{sub 1.95} was doped with a variety of elements, of which lithium was found to be the most effective. Dilatometric studies indicated that by doping CGO with 3mol% lithium nitrate, it was possible to sinter pellets to a relative density of 98.5% at 800 C--a full one hundred degrees below the previous low temperature sintering record for CGO. Further, it was also found that a sintering aid's effectiveness could be explained in terms of its size, charge and high temperature mobility. A closer examination of lithium doped Ce0.9Gd0.1O1.95 indicated that lithium affects sintering by producing a Li{sub 2}O-Gd{sub 2}O{sub 3}-CeO{sub 2} liquid at the CGO grain boundaries. Due to this liquid phase sintering, it was possible to produce dense, crack-free constrained films of CGO at the record low temperature of 950 C using cheap, colloidal spray deposition processes. This is the first time dense constrained CGO films have been produced below 1000 C and could help commercialize metal supported ceria based solid oxide fuel cells.
Date: June 30, 2007
Creator: Nicholas, Jason.D.
Partner: UNT Libraries Government Documents Department