No description available.

No description available.

<p>This work examined the systematic approach to protein crystallization, exploring some of the techniques that have been developed to enhance the success rate of crystallization. The work was centered on two proteins / namely Vaccinia virus complement control protein (VCP) and glutamate dehydrogenase (GDH) from Bacteriodes fragilis. The crystal structures of the full lengthe native VCP and VCP bound to heparin had already been determined. In the same way, the structure of GDH from Bacteriodes fragilis is not known, even though structures of other GDHs from different organisms have been determined.</p>

Si,Ge,-, alloy is an emerging semiconductor material with many important potential applications in the electronic industry due to its adjustable physical, electronic and optical properties. It has been scrutinized for the fabrication of high-speed micro electronics (e.g., SiGe heterojunction bipolar transistors (HBT) and high electron mobility field effect transistors) and thermo-photovoltaics (e.g., photodetectors, solar cells, thermoelectric power generators and temperature sensor). Other applications of Si,Ge,-, include tuneable neutron and x-ray monochromators and y-ray detectors. In these applications, SixGel-, alloy is generally used in the form of epilayers that have to be deposited on a lattice-matched substrate (wafer). Therefore, SixGel-, bulk single crystals with a specific composition (x) are needed for the extraction of such wafers. LPEE (Liquid Phase Electroepitaxy) was considered as a technique of choice for the growth of single crystals. However, LPEE growth process needs a single crystal seed with the same composition as the crystal to be grown. Yet, such a seed substrate with particularly higher composition is not commercially available. In order to address this important issue in LPEE, a crystal growth technique, which is named "Liquid Phase Diffusion" (LPD), was developed and used to produce the needed seed substrate materials. This was the main motivation of the present research. This thesis presents a combined experimental and modelling study for LPD growth of compositionally graded, germanium-rich single crystals of 25 rnrn in diameter for use as lattice-matched seed substrates. The experimental part focuses on the design and development of a complete LPD grow system. The experimental set-up was tested by growing ten Si,Ge,-, single crystals. Grown crystals were characterized by macroscopic and microscopic examinations after chemical etching for delineation of the degree of . . . Abstract 111 single crystallinity and growth striations. Compositional mapping of selected crystals were performed by using Electron Probe Micro Analysis (EPMA) as well as Energy Dispersive X-ray analysis (EDX). It was shown that the LPD technique can be successfully utilized to obtain Si,Ge,-, single crystals up to 6-8 % at.Si with uniform radial composition distribution. The modeling part presents a rational continuum mixture model developed to study transport phenomena (heat and mass transfer, fluid flow) occurring during the LPD growth of Si,Ge,-, . Based on the continuum model developed, two and three-dimensional transient numerical simulations were carried out. The numerical simulation models presented account for some important physical features of the LPD growth process ofSi,Ge,-, , namely (1) a growth zone design on the thermal field, (2) the structure of the buoyancy induced convective flow and its effect on the growth and transport mechanisms, (3) the shape and evolution of the initial and progressing growth interfaces, and (4) the spatial and time variation of the crystal growth velocity. It was numerically shown that, as the name LPD implies, the growth of Si,Ge,-, by LPD is mainly a diffusion driven process except the initial stages of the growth process during which the natural convection in the solution zone is prominent and has significant effects on the composition of the grown crystal. The simulated evolution of the growth interface agrees with experimental observations. In addition, the numerical growth velocities are in good agreement with those of experiments. The numerical model developed can be used to study other crystal growth processes such as LPEE, Traveling Heater Method THM, and vertical Bridgman with slight modifications.

No description available.

Digitized by Kansas Correctional Industries

by Mok Siu Wah. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references. / Text in English; abstract also in Chinese. / by Mok Siu Wah. / Chapter Chapter I --- Introduction / Chapter 1.1 --- Solidification --- p.1-1 / Nucleation A. Homogenous nucleation --- p.1-2 / B. Heterogeneous nucleation --- p.1-3 / Crystal growth and dendrites formation --- p.1-4 / Planar growth --- p.1-5 / Dendrite formation --- p.1-5 / Growth far from equilibrium --- p.1-5 / Chapter 1.2 --- Grain refinement --- p.1 -6 / Models of grains refinement --- p.1-6 / Dynamic nucleation --- p.1-7 / Dendrite remelting --- p.1-8 / Objectives of the present project --- p.1-12 / References --- p.1-13 / Figure --- p.1-14 / Chapter Chapter II --- Experimental method / Experimental methods --- p.2-1 / Specimen preparation --- p.2-1 / Metallography --- p.2-2 / Analysis --- p.2-3 / Reference --- p.2-4 / Figures --- p.2-5 / Chapter Chapter III --- Grain refinement in a system with solubility gap / Abstract --- p.3-1 / Introduction --- p.3-2 / Experimental --- p.3-4 / Results --- p.3-5 / Discussion --- p.3-8 / Reference --- p.3-11 / Figure Caption --- p.3-12 / Figures --- p.3-13

A series of hydrophobic and hydrophilic self-assembled monolayers (SAMs) were deposited by the adsorption of 1- dodecanethiol (SAM I), 11-mercapto-1-undecanol (SAM II), 16- mercaptohexadecanoic acid (SAM III), 5-(10-mercaptodecyloxy) benzene-1,3-dioic acid (SAM IV) and 4-(10-mercaptodecyloxy)- pyridine-2,6-dicarboxylic acid (SAM V) on gold substrates. Crystallization experiments were carried out on SAMs I-V, on control surfaces (bulk gold, glass and PDMS (polydimethlysiloxane)) and in microfluidic devices to screen the polymorphs of two well known drugs, acetaminophen and barbital. Microfluidic devices consist of PDMS (polydimethlysiloxane) patterned with microchannels and then bonded to self-assembled monolayers (SAMs) of organic molecules on gold substrates. The crystallization of acetaminophen was carried out under thermodynamic conditions from solutions at room temperature and under kinetic conditions by rapid cooling. The results of crystallization experiments and the influence of self-assembled monolayers (SAMs) in controlling polymorphism by acting as nucleation sites, or templates, are discussed.

Thesis (Ph. D.)--Lehigh University, 2001. / Includes vita. Includes bibliographical references (leaves 226-234).

Thesis (Ph. D.)--Lehigh University, 2003. / Includes vita. Includes bibliographical references (leaves 118-123).