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Angle- and time-resolved two-photon photoemission (2PPE) was used to study systems of organic semiconductors on Ag(111). The 2PPE studies focused on electronic behavior specific to interfaces and ultrathin films. Electron time dynamics and band dispersions were characterized for ultrathin films of a prototypical n-type planar aromatic hydrocarbon, PTCDA, and representatives from a family of p-type oligothiophenes.In PTCDA, electronic behavior was correlated with film morphology and growth modes. Within a fewmonolayers of the interface, image potential states and a LUMO+1 state were detected. The degree to which the LUMO+1 state exhibited a band mass less than a free electron mass depended on the crystallinity of the layer. Similarly, image potential states were measured to have free electron-like effective masses on ordered surfaces, and the effective masses increased with disorder within the thin film. Electron lifetimes were correlated with film growth modes, such that the lifetimes of electrons excited into systems created by layer-by-layer, amorphous film growth increased by orders of magnitude by only a few monolayers from the surface. Conversely, the decay dynamics of electrons in Stranski-Krastanov systems were limited by interaction with the exposed wetting layer, which limited the barrier to decay back into the metal.Oligothiophenes including monothiophene, quaterthiophene, and …

This dissertation presents the results of a research agenda aimed at improving integration and stability in nanocrystal-based solar cells through advances in active materials and device architectures. The introduction of 3-dimensional nanocrystals illustrates the potential for improving transport and percolation in hybrid solar cells and enables novel fabrication methods for optimizing integration in these systems. Fabricating cells by sequential deposition allows for solution-based assembly of hybrid composites with controlled and well-characterized dispersion and electrode contact. Hyperbranched nanocrystals emerge as a nearly ideal building block for hybrid cells, allowing the controlled morphologies targeted by templated approaches to be achieved in an easily fabricated solution-cast device. In addition to offering practical benefits to device processing, these approaches offer fundamental insight into the operation of hybrid solar cells, shedding light on key phenomena such as the roles of electrode-contact and percolation behavior in these cells. Finally, all-inorganic nanocrystal solar cells are presented as a wholly new cell concept, illustrating that donor-acceptor charge transfer and directed carrier diffusion can be utilized in a system with no organic components, and that nanocrystals may act as building blocks for efficient, stable, and low-cost thin-film solar cells.

Structural Health Monitoring (SHM) promises to deliver great benefits to many industries. Primarily among them is a potential for large cost savings in maintenance of complex structures such as aircraft and civil infrastructure. However, several large obstacles remain before widespread use on structures can be accomplished. The development of three components would address many of these obstacles: a robust sensor validation procedure, a low-cost active-sensing hardware and an integrated software package for transition to field deployment. The research performed in this thesis directly addresses these three needs and facilitates the adoption of SHM on a larger scale, particularly in the realm of SHM based on piezoelectric (PZT) materials. The first obstacle addressed in this thesis is the validation of the SHM sensor network. PZT materials are used for sensor/actuators because of their unique properties, but their functionality also needs to be validated for meaningful measurements to be recorded. To allow for a robust sensor validation algorithm, the effect of temperature change on sensor diagnostics and the effect of sensor failure on SHM measurements were classified. This classification allowed for the development of a sensor diagnostic algorithm that is temperature invariant and can indicate the amount and type of sensor failure. …

The WARP code is a robust electrostatic particle-in-cell simulation package used to model charged particle beams with strong space-charge forces. A fundamental operation associated with seeding detailed simulations of a beam transport channel is to generate initial conditions where the beam distribution is matched to the structure of a periodic focusing lattice. This is done by solving for periodic, matched solutions to a coupled set of ODEs called the Kapchinskij-Vladimirskij (KV) envelope equations, which describe the evolution of low-order beam moments subject to applied lattice focusing, space-charge defocusing, and thermal defocusing forces. Recently, an iterative numerical method was developed (Lund, Chilton, and Lee, Efficient computation of matched solutions to the KV envelope equations for periodic focusing lattices, Physical Review Special Topics-Accelerators and Beams 9, 064201 2006) to generate matching conditions in a highly flexible, convergent, and fail-safe manner. This method is extended and implemented in the WARP code as a Python package to vastly ease the setup of detailed simulations. In particular, the Python package accommodates any linear applied lattice focusing functions without skew coupling, and a more general set of beam parameter specifications than its predecessor. Lattice strength iteration tools were added to facilitate the implementation of problems with …

Model heterogeneous catalysts have been synthesized and studied to better understand how the surface structure of noble metal nanoparticles affects catalytic performance. In this project, monodisperse rhodium and platinum nanoparticles of controlled size and shape have been synthesized by solution phase polyol reduction, stabilized by polyvinylpyrrolidone (PVP). Model catalysts have been developed using these nanoparticles by two methods: synthesis of mesoporous silica (SBA-15) in the presence of nanoparticles (nanoparticle encapsulation, NE) to form a composite of metal nanoparticles supported on SBA-15 and by deposition of the particles onto a silicon wafer using Langmuir-Blodgett (LB) monolayer deposition. The particle shapes were analyzed by transmission electron microscopy (TEM) and high resolution TEM (HRTEM) and the sizes were determined by TEM, X-ray diffraction (XRD), and in the case of NE samples, room temperature H2 and CO adsorption isotherms. Catalytic studies were carried out in homebuilt gas-phase reactors. For the nanoparticles supported on SBA-15, the catalysts are in powder form and were studied using the homebuilt systems as plug-flow reactors. In the case of nanoparticles deposited on silicon wafers, the same systems were operated as batch reactors. This dissertation has focused on the synthesis, characterization, and reaction studies of model noble metal heterogeneous catalysts. …

The ability of Solid Oxide Fuel Cells (SOFC) to directly and efficiently convert the chemical energy in hydrocarbon fuels to electricity places the technology in a unique and exciting position to play a significant role in the clean energy revolution. In order to make SOFC technology cost competitive with existing technologies, the operating temperatures have been decreased to the range where costly ceramic components may be substituted with inexpensive metal components within the cell and stack design. However, a number of issues have arisen due to this decrease in temperature: decreased electrolyte ionic conductivity, cathode reaction rate limitations, and a decrease in anode contaminant tolerance. While the decrease in electrolyte ionic conductivities has been countered by decreasing the electrolyte thickness, the electrode limitations have remained a more difficult problem. Nanostructuring SOFC electrodes addresses the major electrode issues. The infiltration method used in this dissertation to produce nanostructure SOFC electrodes creates a connected network of nanoparticles; since the method allows for the incorporation of the nanoparticles after electrode backbone formation, previously incompatible advanced electrocatalysts can be infiltrated providing electronic conductivity and electrocatalysis within well-formed electrolyte backbones. Furthermore, the method is used to significantly enhance the conventional electrode design by adding secondary …

This report follows the studies on the interactions of antiproton with ordinary matter.

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 …

The Department of Energy`s program for disposing of nuclear High-Level Waste (HLW) and transuranic (TRU) waste has been impeded by overwhelming political opposition fueled by public perceptions of actual risk. Analysis of these perceptions shows them to be deeply rooted in images of fear and dread that have been present since the discovery of radioactivity. The development and use of nuclear weapons linked these images to reality and the mishandling of radioactive waste from the nations military weapons facilities has contributed toward creating a state of distrust that cannot be erased quickly or easily. In addition, the analysis indicates that even the highly educated technical community is not well informed on the latest technology involved with nuclear HLW and TRU waste disposal. It is not surprising then, that the general public feels uncomfortable with DOE`s management plans for with nuclear HLW and TRU waste disposal. Postponing the permanent geologic repository and use of Monitored Retrievable Storage (MRS) would provide the time necessary for difficult social and political issues to be resolved. It would also allow time for the public to become better educated if DOE chooses to become proactive.

The Cloudy Quark Bag Model is extended from S-wave to P- and D-wave. The parameters of the model are determined by K{sup {minus}}p scattering cross section data, K{sup {minus}}p {yields}{Sigma}{pi}{pi}{pi} production data, K{sup {minus}}p threshold branching ratio data, and K{sup {minus}}p {yields}{Lambda}{pi}{pi}{pi} production data. The resonance structure of the {Lambda}(1405), {Sigma}(1385), and {Lambda}(1520) are studied in the model. The shift and width of kaonic hydrogen are calculated using the model.

Here we report structural and functional studies of Mms6, a biomineralization protein that can promote the formation in vitro of magnetic nanoparticles with sizes and morphologies similar to the magnetites synthesized by magnetotactic bacteria. We found the binding pattern of Mms6 to ferric ion to be two-phase and multivalent. We quantatively determined that Mms6 binds one Fe{sup 3+} with a very high affinity (K{sub d} = 10{sup -16} M). The second phase of iron binding is multivalent and cooperative with respect to iron with a K{sub d} in the {mu}M range and a stoichiometry of about 20 ferric ion per protein molecule. We found that Mms6 exists in large particles of two sizes, one consisting of 20-40 monomeric units and the other of 200 units. From proteolytic digestion, ultracentrifugation and liposome fusion studies, we found that Mms6 forms a large micellar quaternary structure with the N-terminal domain self-assembling into a uniformly sized micelle and the C-terminal domain on the surface. The two-phase iron-binding pattern may be relevant to iron crystal formation. We propose that the first high affinity phase may stabilize a new conformation of the C-terminal domain that allows interaction with other C-terminal domains leading to a structural change …

Stimuli-responsive end-capped MSN materials are promising drug carriers that securely deliver a large payload of drug molecules without degradation or premature release. A general review of the recent progress in this field is presented, including a summary of a series of hard and soft caps for drug encapsulation and a variety of internal and external stimuli for controlled release of different therapeutics, a discussion of the biocompatibility of MSN both in vitro and in vivo, and a description of the sophisticated stimuli-responsive systems with novel capping agents and controlled release mechanism. The unique internal and external surfaces of MSN were utilized for the development of a glucose-responsive double delivery system end-capped with insulin. This unique system consists of functionalized MSNs capable of releasing insulin when the concentration of sugar in blood exceeds healthy levels. The insulin-free nanoparticles are then up taken by pancreatic cells, and release inside of them another biomolecule that stimulates the production of more insulin. The in vivo application of this system for the treatment of diabetes requires further understanding on the biological behaviors of these nanoparticles in blood vessels. The research presented in this dissertation demonstrated the size and surface effects on the interaction of MSNs …

The field of metamaterials is driven by fascinating and far-reaching theoretical visions, such as perfect lenses, invisibility cloaking, and enhanced optical nonlinearities. However, losses have become the major obstacle towards real world applications in the optical regime. Reducing the losses of optical metamaterials becomes necessary and extremely important. In this thesis, two approaches are taken to reduce the losses. One is to construct an indefinite medium. Indefinite media are materials where not all the principal components of the permittivity and permeability tensors have the same sign. They do not need the resonances to achieve negative permittivity, {var_epsilon}. So, the losses can be comparatively small. To obtain indefinite media, three-dimensional (3D) optical metallic nanowire media with different structures are designed. They are numerically demonstrated that they are homogeneous effective indefinite anisotropic media by showing that their dispersion relations are hyperbolic. Negative group refraction and pseudo focusing are observed. Another approach is to incorporate gain into metamaterial nanostructures. The nonlinearity of gain is included by a generic four-level atomic model. A computational scheme is presented, which allows for a self-consistent treatment of a dispersive metallic photonic metamaterial coupled to a gain material incorporated into the nanostructure using the finite-difference time-domain (FDTD) method. …

Differential interference contrast (DIC) microscopy is a far-field as well as wide-field optical imaging technique. Since it is non-invasive and requires no sample staining, DIC microscopy is suitable for tracking the motion of target molecules in live cells without interfering their functions. In addition, high numerical aperture objectives and condensers can be used in DIC microscopy. The depth of focus of DIC is shallow, which gives DIC much better optical sectioning ability than those of phase contrast and dark field microscopies. In this work, DIC was utilized to study dynamic biological processes including endocytosis and intracellular transport in live cells. The suitability of DIC microscopy for single particle tracking in live cells was first demonstrated by using DIC to monitor the entire endocytosis process of one mesoporous silica nanoparticle (MSN) into a live mammalian cell. By taking advantage of the optical sectioning ability of DIC, we recorded the depth profile of the MSN during the endocytosis process. The shape change around the nanoparticle due to the formation of a vesicle was also captured. DIC microscopy was further modified that the sample can be illuminated and imaged at two wavelengths simultaneously. By using the new technique, noble metal nanoparticles with different …

The investigation of two poorly understood but technologically important physical properties of silicate glasses and related materials is described. The use of Electron Paramagnetic Resonance to investigate the nature of radiation-induced damage in glasses exposed to a variety of high-energy radiation sources is discussed first. Second, the measurement of the nonlinear index of refraction coefficient in a variety of optical materials related to the design of high-power laser systems is described. The radiation damage investigations rely heavily on the comparison of experimental results for different experimental situations. The comparison of EPR lineshapes, absolute spin densities and power saturation behavior is used to probe a variety of microscopic and macroscopic aspects of radiation damage in glasses. Comparison of radiation damage associated with exposure to gamma rays and fast neutrons (and combinations thereof) are interpreted in terms of the microscopic damage mechanisms which are expected to be associated with the specific radiations. Comparison of radiation damage behavior in different types of glasses is also interpreted in terms of the behavior expected for the specific materials. The body of data which is generated is found to be internally self-consistent and is also generally consistent with the radiation damage behavior expected for specific situations. …

Enzymatic and thermochemical catalysis are both important industrial processes. However, the thermal requirements for each process often render them mutually exclusive: thermochemical catalysis requires high temperature that denatures enzymes. One of the long-term goals of this project is to design a thermocatalytic system that could be used with enzymatic systems in situ to catalyze reaction sequences in one pot; this system would be useful for numerous applications e.g. conversion of biomass to biofuel and other commodity products. The desired thermocatalytic system would need to supply enough thermal energy to catalyze thermochemical reactions, while keeping the enzymes from high temperature denaturation. Magnetic nanoparticles are known to generate heat in an oscillating magnetic field through mechanisms including hysteresis and relaxational losses. We envisioned using these magnetic nanoparticles as the local heat source embedded in sub-micron size mesoporous support to spatially separate the particles from the enzymes. In this study, we set out to find the magnetic materials and instrumental conditions that are sufficient for this purpose. Magnetite was chosen as the first model magnetic material in this study because of its high magnetization values, synthetic control over particle size, shape, functionalization and proven biocompatibility. Our experimental designs were guided by a series …

As metallic structures and devices are being created on a dimension comparable to the length scales of the underlying dislocation microstructures, the mechanical properties of them change drastically. Since such small structures are increasingly common in modern technologies, there is an emergent need to understand the critical roles of elasticity, plasticity, and fracture in small structures. Dislocation dynamics (DD) simulations, in which the dislocations are the simulated entities, offer a way to extend length scales beyond those of atomistic simulations and the results from DD simulations can be directly compared with the micromechanical tests. The primary objective of this research is to use 3-D DD simulations to study the plastic deformation of nano- and micro-scale materials and understand the correlation between dislocation motion, interactions and the mechanical response. Specifically, to identify what critical events (i.e., dislocation multiplication, cross-slip, storage, nucleation, junction and dipole formation, pinning etc.) determine the deformation response and how these change from bulk behavior as the system decreases in size and correlate and improve our current knowledge of bulk plasticity with the knowledge gained from the direct observations of small-scale plasticity. Our simulation results on single crystal micropillars and polycrystalline thin films can march the experiment results …

The research program reported here is focused on critical issues that represent conspicuous gaps in current understanding of rapid solidification, limiting our ability to predict and control microstructural evolution (i.e. morphological dynamics and microsegregation) at high undercooling, where conditions depart significantly from local equilibrium. More specifically, through careful application of phase-field modeling, using appropriate thin-interface and anti-trapping corrections and addressing important details such as transient effects and a velocity-dependent (i.e. adaptive) numerics, the current analysis provides a reasonable simulation-based picture of non-equilibrium solute partitioning and the corresponding oscillatory dynamics associated with single-phase rapid solidification and show that this method is a suitable means for a self-consistent simulation of transient behavior and operating point selection under rapid growth conditions. Moving beyond the limitations of conventional theoretical/analytical treatments of non-equilibrium solute partitioning, these results serve to substantiate recent experimental findings and analytical treatments for single-phase rapid solidification. The departure from the equilibrium solid concentration at the solid-liquid interface was often observed during rapid solidification, and the energetic associated non-equilibrium solute partitioning has been treated in detail, providing possible ranges of interface concentrations for a given growth condition. Use of these treatments for analytical description of specific single-phase dendritic and cellular operating point …

Various methods exist for fabrication of micron and submicron sized waveguide structures. However, most of them include expensive and time consuming semiconductor fabrication techniques. An economical method for fabricating waveguide structures is introduced and demonstrated in this thesis. This method is established based on previously well-developed photonic crystal fabrication method called two-polymer microtransfer molding. The waveguide in this work functions by a coupler structure that diffracts the incident light into submicron polymer rods. The light is then guided through the rods. Characterization is done by collecting the light that has been guided through the waveguide and exits the end of these submicron polymer bars. The coupling and waveguiding capabilities are demonstrated using two light sources, a laser and white light.

This dissertation is comprised of three different angle-resolved photoemission spectroscopy (ARPES) studies on cuprate superconductors. The first study compares the band structure from two different single layer cuprates Tl{sub 2}Ba{sub 2}CuO{sub 6+{delta}} (Tl2201) T{sub c,max} {approx} 95 K and (Bi{sub 1.35}Pb{sub 0.85})(Sr{sub 1.47}La{sub 0.38})CuO{sub 6+{delta}} (Bi2201) T{sub c,max} {approx} 35 K. The aim of the study was to provide some insight into the reasons why single layer cuprate's maximum transition temperatures are so different. The study found two major differences in the band structure. First, the Fermi surface segments close to ({pi},0) are more parallel in Tl2201 than in Bi2201. Second, the shadow band usually related to crystal structure is only present in Bi2201, but absent in higher T{sub c} Tl2201. The second study looks at the different ways of doping Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} (Bi2212) in-situ by only changing the post bake-out vacuum conditions and temperature. The aim of the study is to systematically look into the generally overlooked experimental conditions that change the doping of a cleaved sample in ultra high vacuum (UHV) experiments. The study found two major experimental facts. First, in inadequate UHV conditions the carrier concentration of Bi2212 increases with time, due to the …

The Standard Model (SM) explains CP violation in terms of the CKM matrix. The BABAR experiment was designed mainly to test the CKM model in B decays. B decays that proceed through b {yields} s loop diagrams, of which B {yields} KKK decays are an example, are sensitive to new physics effects that could lead to deviations from the CKM predictions for CP violation. We present studies of CP violation in the decays B{sup +} {yields} K{sup +}K{sup -}K{sup +}, B{sup +} {yields} K{sub S}{sup 0}K{sub S}{sup 0}K{sup +}, and B{sup 0} {yields} K{sup +}K{sup -}K{sub S}{sup 0}, using a Dalitz plot amplitude analysis. These studies are based on approximately 470 million B{bar B} decays collected by BABAR at the PEP-II collider at SLAC. We perform measurements of time-dependent CP violation in B{sup 0} {yields} K{sup +}K{sup -}K{sub S}{sup 0}, including B{sup 0} {yields} {phi}K{sub S}{sup 0}. We measure a CP-violating phase {beta}{sub eff} ({phi}K{sub S}{sup 0}) = 0.36 {+-} 0.11 {+-} 0.04 rad., in agreement with the SM. This is the world's most precise measurement of this quantity. We also measure direct CP asymmetries in all three decay modes, including the direct CP asymmetry A{sub CP} ({phi}K{sup +}) = …

In Part One they formulate in a general way the problem of analyzing and evaluating the aberrations of quadrupole magnet beam systems, and of characterizing the shapes and other properties of the beam envelopes in the neighborhood of foci. They consider all aberrations, including those due to misalignments and faulty construction, through third order in small parameters, for quadrupole beam systems. One result of this study is the development of analytic and numerical techniques for treating these aberrations, yielding useful expressions for the comparison of the aberrations of different beam systems. A second result of this study is a comprehensive digital computer program that determines the magnitude and nature of the aberrations of such beam systems. The code, using linear programming techniques, will adjust the parameters of a beam system to obtain specified optical properties and to reduce the magnitude of aberrations that limit the performance of that system. They examine numerically, in detail, the aberrations of two typical beam systems. In Part Two, they examine the problem of extracting the proton beam from a synchrotron of 'H' type magnet construction. They describe the optical studies that resulted in the design of an external beam from the Bevatron that is …

The work presented in this thesis mainly focuses on the nucleation and growth of metal thin films on multimetallic surfaces. First, we have investigated the Ag film growth on a bulk metallic glass surface. Next, we have examined the coarsening and decay of bilayer Ag islands on NiAl(110) surface. Third, we have investigated the Ag film growth on NiAl(110) surface using low-energy electron diffraction (LEED). At last, we have reported our investigation on the epitaxial growth of Ni on NiAl(110) surface. Some general conclusions can be drawn as follows. First, Ag, a bulk-crystalline material, initially forms a disordered wetting layer up to 4-5 monolayers on Zr-Ni-Cu-Al metallic glass. Above this coverage, crystalline 3D clusters grow, in parallel with the flatter regions. The cluster density increases with decreasing temperature, indicating that the conditions of island nucleation are far-from-equilibrium. Within a simple model where clusters nucleate whenever two mobile Ag adatoms meet, the temperature-dependence of cluster density yields a (reasonable) upper limit for the value of the Ag diffusion barrier on top of the Ag wetting layer of 0.32 eV. Overall, this prototypical study suggests that it is possible to grow films of a bulk-crystalline metal that adopt the amorphous character of …