The family of R{sub 5}Si{sub x}Ge{sub 4-x} alloys demonstrates a variety of unique physical phenomena related to magneto-structural transitions associated with reversible breaking and reforming of specific bonds that can be controlled by numerous external parameters such as chemical composition, magnetic field, temperature, and pressure. Therefore, R{sub 5}Si{sub x}Ge{sub 4-x} systems have been extensively studied to uncover the mechanism of the extraordinary magneto-responsive properties including the giant magnetoresistance (GMR) and colossal magnetostriction, as well as giant magnetocaloric effect (GMCE). Until now, more than a half of possible R{sub 5}Si{sub x}Ge{sub 4-x} pseudobinary systems have been completely or partially investigated with respect to their crystallography and phase relationships (R = La, Pr, Nd, Gd, Tb, Dy, Er, Lu, Y). Still, there are other R{sub 5}Si{sub x}Ge{sub 4-x} systems (R = Ce, Sm, Ho, Tm, and Yb) that are not studied yet. Here, we report on phase relationships and structural, magnetic, and thermodynamic properties in the Yb{sub 5}Si{sub x}Ge{sub 4-x} and Sm{sub 5}Si{sub x}Ge{sub 4-x} pseudobinary systems, which may exhibit mixed valence states. The crystallography, phase relationships, and physical properties of Yb{sub 5}Si{sub x}Ge{sub 4-x} alloys with 0 {le} x {le} 4 have been examined by using single crystal and powder x-ray …

Undergraduate thesis exploring the effects of growing up with parental chronic illness on emerging adults. The current study utilizes self-reported questionnaire data on the psychosocial functioning of 635 students from UNT to increase understanding of how parental chronic illness affects university students' life satisfaction, psychological distress, and compulsive self-reliance. In an attempt to identify potential protective factors, the moderating effects of attachment and resiliency on the link between parental chronic illness and the psychosocial wellness variables were examined.

Thesis discussing "a technique for determining the generation times of individual yeast cells...the effect of x-radiation on the generation times of individual cells and their progeny..." and "attempts to synchronize cell division in a population of cells."

The aim of the present thesis is to investigate the local magnetic properties of homometallic Cr{sub 8} antiferromagnetic (AFM) ring and the changes occurring by replacing one Cr{sup 3+} ion with diamagnetic Cd{sup 2+} (Cr{sub 7}Cd) and with Ni{sup 2+} (Cr{sub 7}Ni). In the heterometallic ring a redistribution of the local magnetic moment is expected in the low temperature ground state. We have investigated those changes by both {sup 53}Cr-NMR and {sup 19}F-NMR. We have determined the order of magnitude of the transferred hyperfine coupling constant {sup 19}F - M{sup +} where M{sup +} = Cr{sup 3+}, Ni{sup 2+} in the different rings. This latter result gives useful information about the overlapping of the electronic wavefunctions involved in the coordinative bond.

Nanotechnology refers any technique that involves about object with nanoscale (10{sup -9} m) or even smaller. It has become more and more important in recently years and has changed our world dramatically. Most of modern electronic devices today should thanks to the miniaturizing driven by development of nanotechnology. Recent years, more and more governments are investing huge amount of money in research related to nanotechnology. There are two major reasons that nanostructure is so fascinate. The first one is the miniaturizing. It is obvious that if we can make products smaller without losing the features, we can save the cost and increase the performance dramatically. For an example, the first computer in the world, ENIAC, which occupied several rooms, is less powerful than the cheapest calculator today. Today's chips with sizes of less than half an inch contain millions of basic units. All these should thank to the development of nanotechnology. The other reason is that when we come to nanoscale, there are many new effects due to the quantum effect which can't be found in large systems. For an example, quantum dots (QDs) are systems which sizes are below 1{micro}m(10{sup -6}m) and restricted in three dimensions. There are many …

Magnetic materials exhibiting magnetic phase transitions simultaneously with structural rearrangements of their crystal lattices hold a promise for numerous applications including magnetic refrigeration, magnetomechanical devices and sensors. We undertook a detailed study of a single crystal of dysprosium metal, which is a classical example of a system where magnetic and crystallographic sublattices can be either coupled or decoupled from one another. Magnetocaloric effect, magnetization, ac magnetic susceptibility, and heat capacity of high purity single crystals of dysprosium have been investigated over broad temperature and magnetic field intervals with the magnetic field vector parallel to either the a- or c-axes of the crystal. Notable differences in the behavior of the physical properties when compared to Dy samples studied in the past have been observed between 110 K and 125 K, and between 178 K and {approx}210 K. A plausible mechanism based on the formation of antiferromagnetic clusters in the impure Dy has been suggested in order to explain the reduction of the magnetocaloric effect in the vicinity of the Neel point. Experimental and theoretical investigations of the influence of commensurability effects on the magnetic phase diagram and the value of the magnetocaloric effect have been conducted. The presence of newly found …

An experimental program has been completed which evaluated the effect of a flow obstruction in a heated channel on the onset of flow instability (OBI). The test channel was rectangular (80 {times} 3 mm), heated on one surface, and equipped with view ports. Tests were conducted in a flow controlled mode at heat fluxes of 370 kW/M{sup 2}, and 610 kW/m{sup 2}. Direct comparisons were made between the demand curve minimum for the unobstructed channel and a channel equipped with a 2.07 mm wide rib that was parallel to the flow and in contact with the heated surface. Data at OFI is presented in the nondimensional terms Of Q{sub ratio} (ratio of heat flux applied to heat flux required to achieve saturated liquid conditions at the exit), and the local Stanton number at the channel exit for each channel arrangement. The Q{sub ratio} and Stanton number values for the unobstructed channel and the rib equipped channel are then compared to produce an estimate of the rib effect.

Our lab has been working with plasma spraying of both high pressure gas atomized (HPGA) and cast and crushed quasicrystal powders. A major component of this research includes comparative studies of PAS coatings formed with starting powders prepared by both techniques. In addition, a thorough investigation of the effects of starting powder particle size on coating microstructure is included. During the course of the overall research, an interest developed in forming Al-Cu-Fe materials with finer grain sizes. Therefore, a brief study was performed to characterize the effect of adding boron to Al-Cu-Fe materials prepared by different techniques. In addition to characterizing the microstructural features of the above materials, oxidation and wear behavior was also examined.

The authors have presented the motivations in gathering doubly polarized data in the quasi-elastic, resonance and DIS domains. These data were used to calculate the extended GDH integral. The comparison of this quantity with the spin dependent forward Compton amplitude {bar S}{sub 1} is of particular importance for the unification of the two strong interaction descriptions (nucleonic/hadronic vs. partonic) because {bar S}{sub 1} is the first quantity theoretically calculable in the full Q{sup 2} domain of the strong interaction. Such a data taking was made possible because of three major technical achievements: (1) the beam of high duty cycle (100%), high current (up to 70 {micro}A) and high polarization (70%); (2) the {sup 3}He target of high density (above 10 atm) with a polarization of 35% and a length of 40 cm; and (3) the large acceptance (6 msr) and high resolution ({Delta}P/P {approx_equal} 10{sup {minus}4}) spectrometers. These features, available at Jefferson Lab, enabled them to achieve the highest luminosity in the world (about 10{sup 36} s{sup {minus}1} cm{sup {minus}2} with a current of 15 {micro}A) as far as polarized {sup 3}He targets are concerned. Consequently they were able to gather, in a rather short period of time (3 months), …

Immunoassays have been utilized for the detection of biological analytes for several decades. Many formats and detection strategies have been explored, each having unique advantages and disadvantages. More recently, surface-enhanced Raman scattering (SERS) has been introduced as a readout method for immunoassays, and has shown great potential to meet many key analytical figures of merit. This technology is in its infancy and this dissertation explores the diversity of this method as well as the mechanism responsible for surface enhancement. Approaches to reduce assay times are also investigated. Implementing the knowledge gained from these studies will lead to a more sensitive immunoassay requiring less time than its predecessors. This dissertation is organized into six sections. The first section includes a literature review of the previous work that led to this dissertation. A general overview of the different approaches to immunoassays is given, outlining the strengths and weaknesses of each. Included is a detailed review of binding kinetics, which is central for decreasing assay times. Next, the theoretical underpinnings of SERS is reviewed at its current level of understanding. Past work has argued that surface plasmon resonance (SPR) of the enhancing substrate influences the SERS signal; therefore, the SPR of the extrinsic …

We have calculated the equilibrium thermodynamic properties of Heisenberg spin systems using a quantum Monte Carlo (QMC) method. We have used some of these systems as models to describe recently synthesized magnetic molecules, and-upon comparing the results of these calculations with experimental data-have obtained accurate estimates for the basic parameters of these models. We have also performed calculations for other systems that are of more general interest, being relevant both for existing experimental data and for future experiments. Utilizing the concept of importance sampling, these calculations can be carried out in an arbitrarily large quantum Hilbert space, while still avoiding any approximations that would introduce systematic errors. The only errors are statistical in nature, and as such, their magnitudes are accurately estimated during the course of a simulation. Frustrated spin systems present a major challenge to the QMC method, nevertheless, in many instances progress can be made. In this chapter, the field of magnetic molecules is introduced, paying particular attention to the characteristics that distinguish magnetic molecules from other systems that are studied in condensed matter physics. We briefly outline the typical path by which we learn about magnetic molecules, which requires a close relationship between experiments and theoretical calculations. …

In an effort to mimic the growth of natural bone, self-assembling, micelle and gel-forming copolymers were used as a template for calcium phosphate precipitation. Because of the cationic characteristics imparted by PDEAEM end group additions to commercially available Pluronic{reg_sign} Fl27, a direct ionic attraction mechanism was utilized and a polymer-brushite nanocomposite spheres were produced. Brushite coated spherical micelles with diameters of {approx}40 nm, and agglomerates of these particles (on the order of 0.5 {mu}m) were obtained. Thickness and durability of the calcium phosphate coating, and the extent of agglomeration were studied. The coating has been shown to be robust enough to retain its integrity even below polymer critical micelle concentration and/or temperature. Calcium phosphate-polymer gel nanocomposites were also prepared. Gel samples appeared as a single phase network of agglomerated spherical micelles, and had a final calcium phosphate concentration of up to 15 wt%. Analysis with x-ray diffraction and NMR indicated a disordered brushite phase with the phosphate groups linking inorganic phase to the polymer.

Fluidized beds (FB) reactors are widely used in the polymerization industry due to their superior heat- and mass-transfer characteristics. Nevertheless, problems associated with local overheating of polymer particles and excessive agglomeration leading to FB reactors defluidization still persist and limit the range of operating temperatures that can be safely achieved in plant-scale reactors. Many people have been worked on the modeling of FB polymerization reactors, and quite a few models are available in the open literature, such as the well-mixed model developed by McAuley, Talbot, and Harris (1994), the constant bubble size model (Choi and Ray, 1985) and the heterogeneous three phase model (Fernandes and Lona, 2002). Most these research works focus on the kinetic aspects, but from industrial viewpoint, the behavior of FB reactors should be modeled by considering the particle and fluid dynamics in the reactor. Computational fluid dynamics (CFD) is a powerful tool for understanding the effect of fluid dynamics on chemical reactor performance. For single-phase flows, CFD models for turbulent reacting flows are now well understood and routinely applied to investigate complex flows with detailed chemistry. For multiphase flows, the state-of-the-art in CFD models is changing rapidly and it is now possible to predict reasonably well …

The inductively coupled plasma (ICP) is an atmospheric pressure ionization source. Traditionally, the plasma is sampled via a sampler cone. A supersonic jet develops behind the sampler, and this region is pumped down to a pressure of approximately one Torr. A skimmer cone is located inside this zone of silence to transmit ions into the mass spectrometer. The position of the sampler and skimmer cones relative to the initial radiation and normal analytical zones of the plasma is key to optimizing the useful analytical signal [1]. The ICP both atomizes and ionizes the sample. Polyatomic ions form through ion-molecule interactions either in the ICP or during ion extraction [l]. Common polyatomic ions that inhibit analysis include metal oxides (MO{sup +}), adducts with argon, the gas most commonly used to make up the plasma, and hydride species. While high resolution devices can separate many analytes from common interferences, this is done at great cost in ion transmission efficiency--a loss of 99% when using high versus low resolution on the same instrument [2]. Simple quadrupole devices, which make up the bulk of ICP-MS instruments in existence, do not present this option. Therefore, if the source of polyatomic interferences can be determined and …

Eddy current nondestructive evaluation (NDE) is usually carried out by exciting a time harmonic field using an inductive probe. However, a viable alternative is to use transient eddy current NDE in which a current pulse in a driver coil produces a transient .eld in a conductor that decays at a rate dependent on the conductivity and the permeability of the material and the coil configuration. By using transient eddy current, it is possible to estimate the properties of the conductive medium and to locate and size potential .aws from the measured probe response. The fundamental study described in this dissertation seeks to establish a theoretical understanding of the transient eddy current NDE. Compared with the Fourier transform method, the derived analytical formulations are more convenient when the transient eddy current response within a narrow time range is evaluated. The theoretical analysis provides a valuable tool to study the effect of layer thickness, location of defect, crack opening as well as the optimization of probe design. Analytical expressions have been developed to evaluate the transient response due to eddy currents in a conductive plate based on two asymptotic series. One series converges rapidly for a short time regime and the other …

Radioactive ion beams (RIBs) have been shown to be a useful tool for studying proton-rich nuclides near and beyond the proton dripline and for evaluating nuclear models. To take full advantage of RIBs, Elastic Resonance Scattering in Inverse Kinematics with Thick Targets (ERSIKTT), has proven to be a reliable experimental tool for investigations of proton unbound nuclei. Following several years of effort, Berkeley Experiments with Accelerated Radioactive Species (BEARS), a RIBs capability, has been developed at the Lawrence Berkeley National Laboratory's 88-Inch Cyclotron. The current BEARS provides two RIBs: a 11C beam of up to 2x108 pps intensity on target and an 14O beam of up to 3x104 pps intensity. While the development of the 11C beam has been relatively easy, a number of challenges had to be overcome to obtain the 14O beam. The excellent 11C beam has been used to investigate several reactions. The first was the 197Au(11C,xn)208-xnAt reaction, which was used to measure excitation functions for the 4n to 8n exit channels. The measured cross sections were generally predicted quite well using the fusion-evaporation code HIVAP. Possible errors in the branching ratios of ?? decays from At isotopes as well as the presence of incomplete fusion reactions …

The solid solution region and reaction kinetics of the Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub y} (2212) superconductor were examined as a function of temperature and oxygen partial pressure. Crystallization studies from the glassy and molten states were undertaken to determine the phase transformation and kinetics associated with the formation of 2212 and other competing phases. Crystallization of nominal 2212 glasses was found to proceed in two steps with the formation of Bi{sub 2}Sr{sub 2{minus}x}Ca{sub x}CuO{sub y} (2201) and Cu{sub 2}O followed by Bi{sub 2}Sr{sub 3{minus}x}Ca{sub x}O{sub y}, CaO, and SrO. The 2212 phase converts from the 2201 phase with increasing temperatures. However, its formation below 800 C was kinetically limited. At 800 C and above, a nearly full conversion to the 2212 phase was achieved after only one minute although considerably longer anneal times were necessary for the system to reach equilibrium. In low oxygen partial pressures, the solidus is reduced to approximately 750 C. Solidification studies revealed an eutectic structure separating the incongruently melting 2212/2201 phases at high oxygen partial pressures from the congruently melting Bi{sub 2}Sr{sub 3{minus}x}Ca{sub x}O{sub y} (23x) and Bi{sub 2}Sr{sub 2{minus}x}Ca{sub x}O{sub y} (22x) phases present at low oxygen partial pressures. During solidification in various oxygen …

In this thesis our main interest has been to investigate metallic photonic crystal and its applications. We explained how to solve a periodic photonic structure with transfer matrix method and when and how to use modal expansion method. Two different coating methods were introduced, modifying a photonic structure's intrinsic optical properties and rigorous calculation results are presented. Two applications of metallic photonic structures are introduced. For thermal emitter, we showed how to design and find optimal structure. For conversion efficiency increasing filter, we calculated its efficiency and the way to design it. We presented the relation between emitting light spectrum and absorption and showed the material and structural dependency of the absorption spectrum. By choosing a proper base material and structural parameters, we can design a selective emitter at a certain region we are interested in. We have developed a theoretical model to analyze a blackbody filament enclosed by a metallic mesh which can increase the efficiency of converting a blackbody radiation to visible light. With this model we found that a square lattice metallic mesh enclosing a filament might increase the efficiency of incandescent lighting sources. Filling fraction and thickness dependency were examined and presented. Combining these two parameters …

Currently one of the most widely used high {Tc} superconductors is the Bi-based compounds Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub z} and Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub z} (known as BSCCO 2212 and 2223 compounds) with {Tc} values of about 85 K and 110 K respectively. Lengths of high performance conductors ranging from 100 to 1000 m long are routinely fabricated and some test magnets have been wound. An additional difficulty here is that although Bi-2212 and Bi-2223 phases exist over a wide range of stoichiometries, neither has been prepared in phase-pure form. So far the most successful method of constructing reliable and robust wires or tapes is the so called powder-in-tube (PIT) technique [1, 2, 3, 4, 5, 6, 7] in which oxide powder of the appropriate stoichiometry and phase content is placed inside a metal tube, deformed into the desired geometry (round wire or flat tape), and annealed to produce the desired superconducting properties. Intermediate anneals are often incorporated between successive deformation steps. Silver is the metal used in this process because it is the most compatible with the reacting phase. In all of the commercial processes for BSCCO, Ag seems to play a special catalytic role promoting the growth …

This dissertation describes several projects to realize low-cost and high-quality three-dimensional (3D) microfabrication using non-photolithographic techniques for layer-by-layer photonic crystals. Low-cost, efficient 3D microfabrication is a demanding technique not only for 3D photonic crystals but also for all other scientific areas, since it may create new functionalities beyond the limit of planar structures. However, a novel 3D microfabrication technique for photonic crystals implies the development of a complete set of sub-techniques for basic layer-by-layer stacking, inter-layer alignment, and material conversion. One of the conventional soft lithographic techniques, called microtransfer molding ({mu}TM), was developed by the Whitesides group in 1996. Although {mu}TM technique potentially has a number of advantages to overcome the limit of conventional photolithographic techniques in building up 3D microstructures, it has not been studied intensively after its demonstration. This is mainly because of technical challenges in the nature of layer-by-layer fabrication, such as the demand of very high yield in fabrication. After two years of study on conventional {mu}TM, We have developed an advanced microtransfer molding technique, called two-polymer microtransfer molding (2P-{mu}TM) that shows an extremely high yield in layer-by-layer microfabrication sufficient to produce highly layered microstructures. The use of two different photo-curable prepolymers, a filler and an …

The purposes of our research were: (1) To develop an economical, easy to use, automated, high throughput system for large scale protein crystallization screening. (2) To develop a new protein crystallization method with high screening efficiency, low protein consumption and complete compatibility with high throughput screening system. (3) To determine the structure of lactate dehydrogenase complexed with NADH by x-ray protein crystallography to study its inherent structural properties. Firstly, we demonstrated large scale protein crystallization screening can be performed in a high throughput manner with low cost, easy operation. The overall system integrates liquid dispensing, crystallization and detection and serves as a whole solution to protein crystallization screening. The system can dispense protein and multiple different precipitants in nanoliter scale and in parallel. A new detection scheme, native fluorescence, has been developed in this system to form a two-detector system with a visible light detector for detecting protein crystallization screening results. This detection scheme has capability of eliminating common false positives by distinguishing protein crystals from inorganic crystals in a high throughput and non-destructive manner. The entire system from liquid dispensing, crystallization to crystal detection is essentially parallel, high throughput and compatible with automation. The system was successfully demonstrated by …

The study of the exocrine pancreatic acinar cell has been central to the development of models of many cellular processes, especially of protein transport and secretion. Traditional methods used to examine this system have provided a wealth of qualitative information from which mechanistic models have been inferred. However they have lacked the ability to make quantitative measurements, particularly of the distribution of protein in the cell, information critical for grounding of models in terms of magnitude and relative significance. This dissertation describes the development and application of new tools that were used to measure the protein content of the major intracellular compartments in the acinar cell, particularly the zymogen granule. Soft x-ray microscopy permits image formation with high resolution and contrast determined by the underlying protein content of tissue rather than staining avidity. A sample preparation method compatible with x-ray microscopy was developed and its properties evaluated. Automatic computerized methods were developed to acquire, calibrate, and analyze large volumes of x-ray microscopic images of exocrine pancreatic tissue sections. Statistics were compiled on the protein density of several organelles, and on the protein density, size, and spatial distribution of tens of thousands of zymogen granules. The results of these measurements, and …

This research describes Fountain, a suite of programs used to monitor the resources of a cluster. A cluster is a collection of individual computers that are connected via a high speed communication network. They are traditionally used by users who desire more resources, such as processing power and memory, than any single computer can provide. A common drawback to effectively utilizing such a large-scale system is the management infrastructure, which often does not often scale well as the system grows. Large-scale parallel systems provide new research challenges in the area of systems software, the programs or tools that manage the system from boot-up to running a parallel job. The approach presented in this thesis utilizes a collection of separate components that communicate with each other to achieve a common goal. While systems software comprises a broad array of components, this thesis focuses on the design choices for a node monitoring component. We will describe Fountain, an implementation of the Scalable Systems Software (SSS) node monitor specification. It is targeted at aggregate node monitoring for clusters, focusing on both scalability and fault tolerance as its design goals. It leverages widely used technologies such as XML and HTTP to present an interface …

A self stabilized, free standing, z-pinch plasma channel has been proposed to deliver the high intensity heavy ion beam from the end of a driver to the fuel target in a heavy ion inertial fusion power plant. The z-pinch relaxes emittance and energy spread requirements requiring a lower cost driver. A z-pinch transport would reduce the number of beam entry port holes to the target chamber from over a hundred to four as compared to neutralized ballistic focusing thus reducing the driver hardware exposure to neutron flux. Experiments where a double pulse discharge technique is used, z-pinch plasma channels with enhanced stability are achieved. Typical parameters are 7 kV pre-pulse discharge and 30 kV main bank discharge with 50 kA of channel current in a 7 torr background gas atmosphere. This work is an experimental study of these plasma channels examining the relevant physics necessary to understand and model such plasmas. Laser diagnostics measured the dynamical properties of neutrals and plasma. Schlieren and phase contrast techniques probe the pre-pulse gas dynamics and infrared interferometry and faraday effect polarimetry are used on the z-pinch to study its electron density and current distribution. Stability and repeatability of the z-pinch depend on the …