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MicroCantilever (MC) based nanomechanical sensor for detection of molecular interactions

Description: Specific aims of this study are to investigate the mechanism governing surface stress generation associated with chemical or molecular binding on functionalized microcantilevers. Formation of affinity complexes on cantilever surfaces leads to charge redistribution, configurational change and steric hindrance between neighboring molecules resulting in surface stress change and measureable cantilever deformation. A novel interferometry technique employing two adjacent micromachined cantilevers (a sensing/reference pair) was utilized to measure the cantilever deformation. The sensing principle is that binding/reaction of specific chemical or biological species on the sensing cantilever transduces to mechanical deformation. The differential bending of the sensing cantilever respect to the reference cantilever ensures that measured response is insensitive to environmental disturbances. As a proof of principle for the measurement technique, surface stress changes associated with: self-assembly of alkanethiol, hybridization of ssDNA, and the formation of cocaine-aptamer complexes were measured. Dissociation constant (K{sub d}) for each molecular reaction was utilized to estimate the surface coverage of affinity complexes. In the cases of DNA hybridization and cocaine-aptamer binding, measured surface stress was found to be dependent on the surface coverage of the affinity complexes. In order to achieve a better sensitivity for DNA hybridization, immobilization of receptor molecules was modified to enhance the deformation of underlying surface. Single-stranded DNA (ssDNA) strands with thiol-modification on both 3-foot and 5-foot ends were immobilized on the gold surface such that both ends are attached to the gold surface. Immobilization condition was controlled to obtain similar receptor density as single-thiolated DNA strands. Hybridization of double-thiolated DNA strands leads to an almost two orders of magnitude increase in cantilever deformation. In both DNA hybridization and the conventional mode for cocaine detection, the lowest detectable concentration was determined by binding activity between the ligand and receptor molecules. In order to overcome this limitation for cocaine detection, a novel ...
Date: May 11, 2011
Creator: Kang, Kyung
Partner: UNT Libraries Government Documents Department

Resonant Inelastic X-ray Scattering of Rare-Earth and CopperSystems

Description: Rare earths and copper systems were studied using X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS). The use of monochromased synchotron radiation and improved energy resolution for RIXS made possible to obtain valuable information on the electronic structure in 4f, 5f and 3d systems. Experimental results for rare-earths (Ho, Gd, Cm, U, Np, Pu) were analyzed by atomic multiplet theory based on the Hartree-Fock calculations. The inelastic scattering structures in RIXS spectra at 5d edge of actinides found to be sensitive to actinide oxidation states in different systems. Comparison of experimental and calculated Cm 5d RIXS spectra gave direct information about valency of the 248-curium isotope in oxide. Scientific understanding of processes that control chemical changes of radioactive species from spent fuel is improved by studying interactions of actinide ions (U, Np, Pu) with corroded iron surfaces. RIXS measurements at the actinide 5d edge found to be sensitive to actinide oxidation states in different systems. Comparison of experimental and calculated Cm 5d RIXS spectra gave direct information about valency of the 248 curium isotope in oxide. Scientific understanding of processes that control chemical changes of radioactive species from spent fuel is improved by studying interactions of actinide ions (U, Np, Pu) with corroded iron surfaces. RIXS measurements at the actinide 5d edge indicate the reduction of U(VI), NP(V) and Pu(VI) to U(IV), Np(IV) and Pu(IV) by presence of iron ions. This thesis is also addressed to the study of changes in the electronic structure of copper films during interaction with synthetic groundwater solutions. The surface modifications induced by chemical reactions of oxidized 100 Angstrom Cu films with CL{sup -}, SO{sub 4}{sup 2-} and HCO{sub 3}{sup -} ions in aqueous solutions with various concentrations were studied in-situ using XAS. It was shown that the pH value, the concentration of ...
Date: July 11, 2007
Creator: Kvashnina, Kristina
Partner: UNT Libraries Government Documents Department

Exclusive B Decays into Final States with Two Charmed Baryons

Description: This Thesis presents measurements of the decays B{sup -} {yields} {Xi}{sub c}{sup 0}{bar {Lambda}}{sub c}{sup -}, {bar B}{sup 0} {yields} {Xi}{sub c}{sup +}{bar {Lambda}}{sub c}{sup -}, B{sup -} {yields} {Lambda}{sub c}{sup +}{bar {Lambda}}{sub c}{sup -} K{sup -}, and {bar B}{sup 0} {yields} {Lambda}{sub c}{sup +}{bar {Lambda}}{sub c}{sup -} K{sub s}{sup 0} based on 228 million {Upsilon}(4S) {yields} B{bar B} decays collected with the BABAR detector at the SLAC PEP-II asymmetric-energy B factory.
Date: January 11, 2010
Creator: Chai, Xuedong & U., /Iowa
Partner: UNT Libraries Government Documents Department

Equilibrium Speciation of Select Lanthanides in the Presence of Acidic Ligands in Homo- and Heterogeneous Solutions

Description: This dissertation explores lanthanide speciation in liquid solution systems related to separation schemes involving the acidic ligands: bis(2-ethylhexyl) phosphoric acid (HDEHP), lactate, and 8-hydroxyquinoline. Equilibrium speciation of neodymium (Nd3+), sodium (Na+), HDEHP, water, and lactate in the TALSPEAK liquid-liquid extraction system was explored under varied Nd3+ loading of HDEHP in the organic phase and through extraction from aqueous HCl and lactate media. System speciation was probed through vapor pressure osmometry, visible and Fourier Transform Infrared (FTIR) spectroscopy, 22Na and 13C labeled lactate radiotracer distribution measurements, Karl Fischer titrations, and equilibrium pH measurements. Distribution of Nd3+, Na+, lactate, and equilibrium pH were modeled using the SXLSQI software to obtain logKNd and logKNa extraction constants under selected conditions. Results showed that high Nd3+ loading of the HDEHP led to Nd3+ speciation that departs from the ion exchange mechanism and includes formation of highly aggregated, polynuclear [NdLactate(DEHP)2]x; (with x > 1). By substituting lanthanum (La3+) for Nd3+ in this system, NMR scoping experiments using 23Na, 31P nuclei and 13C labeled lactate were performed. Results indicated that this technique is sensitive to changes in system speciation, and that further experiments are warranted. In a homogeneous system representing the TALSPEAK aqueous phase, Lactate protonation behavior at various temperatures was characterized using a combination of potentiometric titration and modeling with the Hyperquad computer program. The temperature dependent deprotonation behavior of lactate showed little change with temperature at 2.0 M NaCl ionic strength. Cloud point extraction is a non-traditional separation technique that starts with a homogeneous phase that becomes heterogeneous by the micellization of surfactants through the increase of temperature. To better understand the behavior of europium (Eu3+) and 8-hydroxyquinoline under cloud point extraction conditions, potentiometric and spectrophotometric titrations coupled with modeling with Hyperquad and SQUAD computer programs were performed to assess europium (Eu3+) and 8-hydroxyquinoline speciation. ...
Date: August 11, 2011
Creator: Robinson, Troy A.
Partner: UNT Libraries Government Documents Department

Measurement of differential cross sections and Cx and Cz for gamma photon-proton going to kaon-lambda baryon and gamma photon-proton going to kaon-sigma baryon using CLAS at Jefferson Lab

Description: This work presents several observables for the reactions γ<italic> p</italic> → <italic>K</italic><super>+</super>Λ and γ<italic> p</italic> → <italic>K</italic><super>+</super>Σ°. In addition to measuring differential cross sections, we have made first measurements of the double polarization observables <italic>C<sub>x</sub></italic> and <italic> C<sub>z</sub></italic>. <italic>C<sub>x</sub></italic> and <italic>C<sub> z</sub></italic> characterize the transfer of polarization from the incident photon to the produced hyperons. Data were obtained at Jefferson Lab using a circularly polarized photon beam at endpoint energies of 2.4, 2.9, and 3.1 GeV. Events were detected with the CLAS spectrometer. In the Λ channel, the cross sections support the recent observation of new resonant structure at <italic>W</italic> = 1900 MeV. Studies of the invariant cross section, <math> <f> <fr><nu>d<g>s</g></nu><de>dd</de></fr></f> </math> show scaling behavior suggesting that the production mechanism becomes <italic> t</italic>-channel dominated near threshold at forward kaon angles. The double polarization observables show that the recoiling Λ is almost maximally polarized along the direction of the incident photon from mid to forward kaon angles. While Σ<super>o</super> differential cross sections are of the same magnitude as the Λ differential cross sections, there is evidence of different physics dominating the production mechanism. The Σ° invariant cross sections do not show the same <italic>t</italic>-scaling behavior present in the Λ results. The double polarization observables indicate that the Σ° is not polarized as strongly as the Λ. They also fail to identify one preferred polarization axis. Complete interpretation of these results will rely on model calculations. Currently available isobar models obtain varying degrees of success while attempting to predict the double polarization observables. While the models are in better agreement with the differential cross sections, discrepancies with our cross sections indicate that they must be re-optimized in light of the new data. While the data suggest that a Regge model would provide a good description of <italic>K</italic><super>+</super>Λ over most of the ...
Date: May 11, 2005
Creator: Bradford, Robert
Partner: UNT Libraries Government Documents Department

Understanding How Femtosecond Laser Waveguide Fabrication in Glasses Works

Description: In order to understand the physical processes associated with fs-laser waveguide writing in glass, the effects of the laser repetition rate, the material composition and feature size were studied. The resulting material changes were observed by collecting Raman and fluorescence spectra with a confocal microscope. The guiding behavior of the waveguides was evaluated by measuring near field laser coupling profiles in combination with white light microscopy. Waveguides and Bragg gratings were fabricated in fused silica using pulse repetition rates from 1 kHz to 1 MHz and a wide range of scan speeds and pulse energies. Two types of fluorescence were detected in fused silica, depending on the fabrication conditions. Fluorescence from self trapped exciton (E{prime}{sub {delta}}) defects, centered at 550 nm, were dominant for conditions with low total doses, such as using a 1 kHz laser with a scan speed of 20 {micro}m/s and pulse energies less than 1 {micro}J. For higher doses a broad fluorescence band, centered at 650 nm, associated with non-bridging oxygen hole center (NBOHC) defects was observed. Far fewer NBOHC defects were formed with the 1 MHz laser than with the kHz lasers possibly due to annealing of the defects during writing. We also observed an increase in the intensity of the 605 cm{sup -1} Raman peak relative to the total Raman intensity, corresponding to an increase in the concentration of 3-membered rings for all writing conditions. The magnitude of this increase in waveguides fabricated with a 1 MHz laser was nearly twice that of waveguides fabricated with a 1 kHz laser. Additional waveguides were fabricated in soda lime silicate glasses to assess the effects of changing the glass composition. These waveguides formed around, not inside the exposed regions. This is distinctly different from fused silica in which the waveguides are inside the exposed regions. A ...
Date: May 11, 2006
Creator: Reichman, W J
Partner: UNT Libraries Government Documents Department

Time Dependent Analysis of B to rho0rho0 Decays

Description: The BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} collider is located at the Stanford Linear Accelerator Center. It has been gathering data on the {Upsilon}(4S) resonance from 2000 until 2007 with the primary objective of studying CP violation in B-meson decays. In this thesis they provide a theoretical overview of how CP violation arises in the context of the Standard Model, why B decays are relevant, and how BABAR gathers the necessary data. Specifically, they present the analysis of B{sup 0} {yields} {rho}{sup 0}{rho}{sup 0} decays in a sample of 465 x 10{sup 6} {Upsilon}(4S) {yields} B{bar B}. They measure the corresponding branching fraction {Beta} = (0.92 {+-} 0.32(stat.) {+-} 0.14(syst.)) x 10{sup -6} and the longitudinal polarization fraction f{sub L} = 0.75{sub -0.14}{sup +0.11}(stat.) {+-} 0.04(syst.). The evidence for the B{sup 0} {yields} {rho}{sup 0}{rho}{sup 0} signal has a significance of 3.1 standard deviations ({sigma}), when the systematic uncertainties are included. There is insufficient evidence for B decays into similar modes and the corresponding upper limits are determined to be {Beta}{sub {rho}{sup 0}f{sub 0}} &lt; 0.34 x 10{sup -6}, {Beta}{sub f{sub 0}f{sub 0}} &lt; 0.16 x 10{sup -6}, {Beta}{sub {rho}{sup 0}{pi}{sup +}{pi}{sup -}} &lt; 8.7 x 10{sup -6}, B{sub {pi}{sup +}{pi}{sup -}{pi}{sup +}{pi}{sup -}} &lt; 21.1 x 10{sup -6} at the 90% Confidence Level (CL). They also investigate the proper-time dependence of the longitudinal component in the decay and measure the Cp-violating coefficients S{sub L} = 0.3 {+-} 0.7(stat.) {+-} 0.2(syst.) and C{sub L} = 0.2 {+-} 0.8(stat.) {+-} 0.3(syst.). By combining these results with other measurements from the B {yields} {rho}{rho} processes and performing an Isospin Analysis, they are able to restrict the unitarity angle {alpha} as well as its uncertainty due to penguin contributions, {Delta}{alpha}. Namely, {alpha} = (92.4{sub -6.5}{sup +6.0}){sup o} with -1.8{sup o} ...
Date: December 11, 2009
Creator: Osipenkov, Ilya Leonidovich & /UC, Berkeley
Partner: UNT Libraries Government Documents Department

Finding the Higgs boson of the standard model in the channel ZH → e<sup>+</sup>e<sup>-</sup>b$\bar{b}$ with the D0 detector at the Tevatron; Recherche du boson de Higgs du nideke standard dans le canal ZH → e<sup>+</sup>e<sup>-</sup>b$\bar{b}$ avec le detecteur DØ aupres du Tevatron

Description: The organization of this thesis consists of three main ideas: the first presents the theoretical framework and experimental, as well as objects used in the analysis and the second relates to the various work tasks of service that I performed on the calorimeter, and the third is the search for the Higgs boson in the channel ZH → e<sup>+</sup>e<sup>-</sup>b$\bar{b}$. Thus, this thesis has the following structure: Chapter 1 is an introduction to the standard model of particle physics and the Higgs mechanism; Chapter 2 is an overview of the complex and the acceleration of the Tevatron at Fermilab DØ detector; Chapter 3 is an introduction to physical objects used in this thesis; Chapter 4 presents the study made on correcting the energy measured in the calorimeter; Chapter 5 describes the study of certification of electrons in the calorimeter; Chapter 6 describes the study of certification of electrons in the intercryostat region of calorimeter; Chapter 7 Detailed analysis on the search for Higgs production in the channel ZH → e<sup>+</sup>e<sup>-</sup>b$\bar{b}$; and Chapter 8 presents the final results of the calculations of upper limits to the production cross section of the Higgs boson on a range of low masses.
Date: June 11, 2010
Creator: Calpas, Betty Constante
Partner: UNT Libraries Government Documents Department

Scintillation response of lithium fluoride

Description: Thesis. Lithium fluoride crystals, with TlF added to the charge, were prepared by the Bridgman- Stockbarger method. The scintillation response to photon energies between 25 and 1250 keV for these crystals and a commercially prepared LiF (Ti) crystal was studied. The response of the LiF (Ti) crystal was compared to the response of an NE109 scintillator at 1250 keV. The dose response of the LiF (Ti) crystal was evaluated over the energy range 25 to 1250 keV. The absorption and emission spectra of the LiF (Ti) crystal are discussed. A historical review precedes the discussion. (auth)
Date: February 11, 1974
Creator: Kloepping, R.J.
Partner: UNT Libraries Government Documents Department

Leptonic Decays of the Charged B Meson

Description: The authors present a search for the decay B{sup +} {yields} {ell}{sup +}{nu}{sub {ell}} ({ell} = {tau}, {mu}, or e) in (458.9 {+-} 5.1) x 10{sup 6} {Upsilon}(4S) decays recorded with the BABAR detector at the SLAC PEP-II B-Factory. A sample of events with one reconstructed exclusive semi-leptonic B decay (B{sup -} {yields} D{sup 0}{ell}{sup -}{bar {nu}}X) is selected, and in the recoil a search for B{sup +} {yields} {ell}{sup +}{nu}{sub {ell}} signal is performed. The {tau} is identified in the following channels: {tau}{sup +} {yields} e{sup +}{nu}{sub e}{bar {nu}}{sub {tau}}, {tau}{sup +} {yields} {mu}{sup +}{nu}{sub {mu}}{bar {nu}}{sub {tau}}, {tau}{sup +} {yields} {pi}{sup +}{bar {nu}}{sub {tau}}, and {tau}{sup +} {yields} {pi}{sup +}{pi}{sup 0}{bar {nu}}{sub {tau}}. The analysis strategy and the statistical procedure is set up for branching fraction extraction or upper limit determination. They determine from the dataset a preliminary measurement of {Beta}(B{sup +} {yields} {tau}{sup +}{nu}{sub {tau}}) = (1.8 {+-} 0.8 {+-} 0.1) x 10{sup -4}, which excludes zero at 2.4{sigma}, and f{sub B} = 255 {+-} 58 MeV. Combination with the hadronically tagged measurement yields {Beta}(B{sup +} {yields} {tau}{sup +}{nu}{sub {tau}}) = (1.8 {+-} 0.6) x 10{sup -4}. They also set preliminary limits on the branching fractions at {Beta}(B{sup +} {yields} e{sup +}{nu}{sub e}) &lt; 7.7 x 10{sup -6} (90% C.L.), {Beta}(B{sup +} {yields} {mu}{sup +}{nu}{sub {mu}}) &lt; 11 x 10{sup -6} (90% C.L.), and {Beta}(B{sup +} {yields} {tau}{sup +}{nu}{sub {tau}}) &lt; 3.2 x 10{sup -4} (90% C.L.).
Date: June 11, 2010
Creator: Corwin, Luke A.; U., /Ohio State & ,
Partner: UNT Libraries Government Documents Department

Geometrical aspects of quantum spaces

Description: Various geometrical aspects of quantum spaces are presented showing the possibility of building physics on quantum spaces. In the first chapter the authors give the motivations for studying noncommutative geometry and also review the definition of a Hopf algebra and some general features of the differential geometry on quantum groups and quantum planes. In Chapter 2 and Chapter 3 the noncommutative version of differential calculus, integration and complex structure are established for the quantum sphere S{sub 1}{sup 2} and the quantum complex projective space CP{sub q}(N), on which there are quantum group symmetries that are represented nonlinearly, and are respected by all the aforementioned structures. The braiding of S{sub q}{sup 2} and CP{sub q}(N) is also described. In Chapter 4 the quantum projective geometry over the quantum projective space CP{sub q}(N) is developed. Collinearity conditions, coplanarity conditions, intersections and anharmonic ratios is described. In Chapter 5 an algebraic formulation of Reimannian geometry on quantum spaces is presented where Riemannian metric, distance, Laplacian, connection, and curvature have their quantum counterparts. This attempt is also extended to complex manifolds. Examples include the quantum sphere, the complex quantum projective space and the two-sheeted space. The quantum group of general coordinate transformations on some quantum spaces is also given.
Date: May 11, 1996
Creator: Ho, P.M.
Partner: UNT Libraries Government Documents Department

A quasi-model-independent search for new high p{_}T physics at DO

Description: We present a new quasi-model-independent strategy (''Sleuth'') for searching for physics beyond the standard model. We define final states to be studied, and construct a rule that identifies a set of relevant variables for any particular final state. A novel algorithm searches for regions of excess in those variables and quantifies the significance of any detected excess. This strategy is applied to search for new high p{_}T physics in approximately 100 pb{sup -1} of proton-anti-proton collisions at sqrt(s) = 1.8 TeV collected by the D0 experiment during 1992-1996 at the Fermilab Tevatron. We systematically analyze many exclusive final states, and demonstrate sensitivity to a variety of models predicting new phenomena at the electroweak scale. No evidence of new high p{_}T physics is observed.
Date: December 11, 2000
Creator: Knuteson, Bruce O.
Partner: UNT Libraries Government Documents Department

The interaction of intense subpicosecond laser pulses with underdense plasmas

Description: Laser-plasma interactions have been of interest for many years not only from a basic physics standpoint, but also for their relevance to numerous applications. Advances in laser technology in recent years have resulted in compact laser systems capable of generating (psec), 10{sup 16} W/cm{sup 2} laser pulses. These lasers have provided a new regime in which to study laser-plasma interactions, a regime characterized by L{sub plasma} {ge} 2L{sub Rayleigh} > c{tau}. The goal of this dissertation is to experimentally characterize the interaction of a short pulse, high intensity laser with an underdense plasma (n{sub o} {le} 0.05n{sub cr}). Specifically, the parametric instability known as stimulated Raman scatter (SRS) is investigated to determine its behavior when driven by a short, intense laser pulse. Both the forward Raman scatter instability and backscattered Raman instability are studied. The coupled partial differential equations which describe the growth of SRS are reviewed and solved for typical experimental laser and plasma parameters. This solution shows the growth of the waves (electron plasma and scattered light) generated via stimulated Raman scatter. The dispersion relation is also derived and solved for experimentally accessible parameters. The solution of the dispersion relation is used to predict where (in k-space) and at what frequency (in {omega}-space) the instability will grow. Both the nonrelativistic and relativistic regimes of the instability are considered.
Date: May 11, 1995
Creator: Coverdale, C.A.
Partner: UNT Libraries Government Documents Department