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open access

Accelerated hygrothermal stabilization of composite materials

Description: Experimentation validated a simple moisture conditioning scheme to prepare Gr/Ep composite parts for precision applications by measuring dimensional changes over 90 days. It was shown that an elevated temperature moisture conditioning scheme produced a dimensionally stable part from which precision structures could be built/machined without significant moisture induced dimensional changes after fabrication. Conversely, that unconditioned Gr/Ep composite panels exhibited unacceptably large dimen… more
Date: May 1, 1994
Creator: Gale, J. A.
open access

Adsorbate structures and catalytic reactions studied in the torrpressure range by scanning tunneling microscopy

Description: High-pressure, high-temperature scanning tunneling microscopy (HPHTSTM) was used to study adsorbate structures and reactions on single crystal model catalytic systems. Studies of the automobile catalytic converter reaction [CO + NO {yields} 1/2 N{sub 2} + CO{sub 2}] on Rh(111) and ethylene hydrogenation [C{sub 2}H{sub 4} + H{sub 2} {yields} C{sub 2}H{sub 6}] on Rh(111) and Pt(111) elucidated information on adsorbate structures in equilibrium with high-pressure gas and the relationship of atomic… more
Date: May 23, 2003
Creator: Hwang, Kevin Shao-Lin
open access

Advanced far infrared blocked impurity band detectors based on germanium liquid phase epitaxy

Description: This research has shown that epilayers with residual impurity concentrations of 5 x 10{sup 13} cm{sup {minus}3} can be grown by producing the purest Pb available in the world. These epilayers have extremely low minority acceptor concentrations, which is ideal for fabrication of IR absorbing layers. The Pb LPE growth of Ge also has the advantageous property of gettering Cu from the epilayer and the substrate. Epilayers have been grown with intentional Sb doping for IR absorption on lightly doped… more
Date: May 1, 1998
Creator: Olsen, C.S.
open access

Aerosol Property Comparison Within and Above the ABL at the ARM Program SGP Site

Description: This thesis determines what, if any, measurements of aerosol properties made at the Earth surface are representative of those within the entire air column. Data from the Atmospheric Radiation Measurement site at the Southern Great Plains, the only location in the world where ground-based and in situ airborne measurements are routinely made. Flight legs during the one-year period from March 2000 were categorized as either within or above the atmospheric boundary layer (ABL) by use of an objectiv… more
Date: May 1, 2002
Creator: Delle Monache, L
open access

An analysis of multiple particle settling for LMR backup shutdown systems

Description: Backup shutdown systems proposed for future LMRs may employ discreet absorber particles to provide the negative reactivity insertion. When actuated, these systems release a dense packing of particles from an out-of-core region to settle into an in-core region. The multiple particle settling behavior is analyzed by the method of continuity waves. This method provides predictions of the dynamic response of the system including the average particle velocity and volume fraction of particles vs. tim… more
Date: May 1, 1992
Creator: Brock, R. W.
open access

Antineutrino Oscillations in the Atmospheric Sector

Description: This thesis presents measurements of the oscillations of muon antineutrinos in the atmospheric sector, where world knowledge of antineutrino oscillations lags well behind the knowledge of neutrinos, as well as a search for {nu}{sub {mu}} {yields} {bar {nu}}{sub {mu}} transitions. Differences between neutrino and antineutrino oscillations could be a sign of physics beyond the Standard Model, including non-standard matter interactions or the violation of CPT symmetry. These measurements leverage … more
Date: May 1, 2011
Creator: Himmel, Alexander I. & /Caltech
open access

The applicability of certain Monte Carlo methods to the analysis of interacting polymers

Description: The authors consider polymers, modeled as self-avoiding walks with interactions on a hexagonal lattice, and examine the applicability of certain Monte Carlo methods for estimating their mean properties at equilibrium. Specifically, the authors use the pivoting algorithm of Madras and Sokal and Metroplis rejection to locate the phase transition, which is known to occur at {beta}{sub crit} {approx} 0.99, and to recalculate the known value of the critical exponent {nu} {approx} 0.58 of the system … more
Date: May 1, 1998
Creator: Krapp, D.M. Jr.
open access

Application of a passive electrochemical noise technique to localized corrosion of candidate radioactive waste container materials

Description: One of the key engineered barriers in the design of the proposed Yucca Mountain repository is the waste canister that encapsulates the spent fuel elements. Current candidate metals for the canisters to be emplaced at Yucca Mountain include cast iron, carbon steel, Incoloy 825 and titanium code-12. This project was designed to evaluate passive electrochemical noise techniques for measuring pitting and corrosion characteristics of candidate materials under prototypical repository conditions. Expe… more
Date: May 1, 1994
Creator: Korzan, M. A.
open access

Application of seismic tomographic techniques in the investigation of geothermal systems

Description: The utility of microearthquake data for characterizing the Northwest Geysers geothermal field and the Long Valley Caldera (LVC) was investigated. Three-dimensional (3-D) P- and S-wave seismic velocity models were estimated for the Coldwater Creek Steam Field (CCSF) in the Northwest Geysers region. Hypocenters relocated using these 3-D models appear to be associated with the steam producing zone, with a deeper cluster of hypocenters beneath an active injection well. Spatial and temporal patterns… more
Date: May 1, 1995
Creator: Romero, A. E., Jr.
open access

Applications of Flavor Symmetry to the Phenomenology of Elementary Particles

Description: Some applications of flavor symmetry are examined. Approximate flavor symmetries and their consequences in the MSSM (Minimal Supersymmetric Standard Model) are considered, and found to give natural values for the possible B- and L-violating couplings that are empirically acceptable, except for the case of proton decay. The coupling constants of SU(3) are calculated and used to parameterize the decays of the D mesons in broken flavor SU(3). The resulting couplings are used to estimate the long-d… more
Date: May 1, 1995
Creator: Kaeding, T. A.
open access

Aspherical supernovae

Description: Although we know that many supernovae are aspherical, the exact nature of their geometry is undetermined. Because all the supernovae we observe are too distant to be resolved, the ejecta structure can't be directly imaged, and asymmetry must be inferred from signatures in the spectral features and polarization of the supernova light. The empirical interpretation of this data, however, is rather limited--to learn more about the detailed supernova geometry, theoretical modeling must been undertak… more
Date: May 21, 2004
Creator: Kasen, Daniel Nathan
open access

Atom transfer and rearrangement reactions catalyzed by methyltrioxorhenium, MTO

Description: 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 … more
Date: May 10, 1999
Creator: Jacob, J.
open access

An axial approach to detection in capillary electrophoresis

Description: Our approach involves on-axis illumination of the compounds inside the capillary detection region and is applied to absorbance and fluorescence detection. Absorbance measurements were made by focussing an incident laser beam into one capillary end; by using signals collected over the entire length of analyte band, this enhances the analytical path length of conventional absorbance detection 60x. This instrument offers a 15x improvement in detection limits. Three fluorescence detection experimen… more
Date: May 1, 1993
Creator: Taylor, J. A.
open access

Big-bang nucleosynthesis with high-energy photon injection

Description: The author discusses the photodissociation of light elements due to the radiative decay of a massive particle, and he has shown how to constrain the model parameters from the observed light-element abundances. He adopted two quasar absorption system (QAS) D/H values, as well as solar system data for D/H and {sup 3}He/H. For each of these, he used two {sup 4}He values. He presents his results in terms of the confidence level at which each theoretical parameter set (i.e., the set of properties of… more
Date: May 1, 1999
Creator: Holtmann, Erich N.
open access

Bioinspired synthesis of magnetic nanoparticles

Description: The synthesis of magnetic nanoparticles has long been an area of active research. Magnetic nanoparticles can be used in a wide variety of applications such as magnetic inks, magnetic memory devices, drug delivery, magnetic resonance imaging (MRI) contrast agents, and pathogen detection in foods. In applications such as MRI, particle uniformity is particularly crucial, as is the magnetic response of the particles. Uniform magnetic particles with good magnetic properties are therefore required. O… more
Date: May 26, 2009
Creator: David, Anand
open access

Biological Applications and Transmission Electron Microscopy Investigations of Mesoporous Silica Nanoparticles

Description: The research presented and discussed within involves the development of novel biological applications of mesoporous silica nanoparticles (MSN) and an investigation of mesoporous material by transmission electron microscopy (TEM). Mesoporous silica nanoparticles organically functionalized shown to undergo endocytosis in cancer cells and drug release from the pores was controlled intracellularly and intercellularly. Transmission electron microscopy investigations demonstrated the variety of morph… more
Date: May 1, 2006
Creator: Trewyn, Brian G.
open access

Biomolecular Assembly of Gold Nanocrystals

Description: Over the past ten years, methods have been developed to construct discrete nanostructures using nanocrystals and biomolecules. While these frequently consist of gold nanocrystals and DNA, semiconductor nanocrystals as well as antibodies and enzymes have also been used. One example of discrete nanostructures is dimers of gold nanocrystals linked together with complementary DNA. This type of nanostructure is also known as a nanocrystal molecule. Discrete nanostructures of this kind have a number … more
Date: May 20, 2005
Creator: Micheel, Christine Marya
open access

The breakdown of de Gennes Scaling in TbxEr1-xNi2B2C and its mean field theory explanation

Description: The Neel temperatures, T{sub N}, of Tb{sub x}Er{sub 1-x}Ni{sub 2}B{sub 2}C samples have been determined from the temperature dependence of magnetization measurements. A breakdown of the de Gennes scaling of T{sub N} with a clear turning point around x = 0.45 has been observed. The T{sub N} values of Tb{sub x}Er{sub 1-x}Ni{sub 2}B{sub 2}C do not change much within the range of O < x < 0.45 and then, for larger x they increase almost linearly with concentration until T{sub N} = 14.9K is rea… more
Date: May 1, 2005
Creator: Gao, Chunwang
open access

Bridging the pressure gap: In situ atomic-level investigations of model platinum catalyst surfaces under reaction conditions by scanning tunneling microscopy

Description: Results of this thesis show that STM measurements can provide information about the surfaces and their adsorbates. Stability of Pt(110) under high pressures of H2, O2, and CO was studied (Chap. 4). In situ UHV and high vacuum experiments were carried out for sulfur on Pt(111) (Chap.5). STM studies of CO/S/Pt(111) in high CO pressures showed that the Pt substrate undergoes a stacking-fault-domain reconstruction involving periodic transitions from fcc to hcp stacking of top-layer atoms (Chap.6). … more
Date: May 1, 1994
Creator: McIntyre, B. J.
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