Thesis (Ph. D.)--Industrial and Systems Engineering, Georgia Institute of Technology, 2006. / Huo, Xiaoming, Committee Member ; Heil, Chris, Committee Member ; Wang, Yang, Committee Member ; Hayter, Anthony, Committee Member ; Vidakovic, Brani, Committee Chair.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2005. / Includes bibliographical references (leaves 68-77). Also available in electronic version.

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2006. / Includes bibliographical references (leaves 119-132). Also available in electronic version.

Spermiogenesis and ultrastructure of the spermatozoon of two bothriocephalidean cestodes, Oncodiscus sauridae and Senga sp., have been studied using transmission electron microscopy. The presence of a classical pattern for spermatological characters (spermiogenesis of type I with dense-material in early stages and sperm of type II with a characteristic ring of cortical microtubules in the anterior part) in Bothriocephalidea is discussed.

Mixed metal oxides are ionic compounds containing at least two metal ions within an oxide structure. The literature contains a plethora of examples of mixed metal oxides on the bulk scale, which have been well characterised, however, mixed metal oxides on the nanoscale are far less well understood. The work presented here investigates the Bi2O3-CeO2-Nb2O5 mixed oxide system and characterises the resulting nanoparticles and crystal structures. Although the parent oxides are well known and much work has previously been done in analysing their crystal structures, combinations of these oxides have not been well characterised, especially on the nanoscale. Using high resolution electron microscopy (HRTEM), powder X-ray diffraction (PXRD), electron dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) as analytical tools, the structures of the nanoparticles in this system have been explored. As each of the parent oxides possess useful properties, which have been utilised in industrial applications such as electrolyte components in solid oxide fuel cells and as catalysts in a range of chemical reactions, it was hypothesised that if all three metal ions could be contained in one particle they could show novel and interesting characteristics. It was proposed that due to the more relaxed crystal structure in nanoparticles, the solid solubility of the metal ions should be increased, and a solid solution of ions would form. This work presents results showing the synthesis of binary and ternary oxides in the nano-form within the Bi2O3-CeO2-Nb2O5 system, including quantitative analysis of these particles. Secondly, and most importantly, it presents the first successful synthesis of quaternary oxide nanoparticles containing bismuth, cerium and niobium using the low temperature resin-gel method. Finally, the work attempts to explain how and why the ions are ordered in a given arrangement, with bismuth showing a preference for surface site occupation, as shown by XPS data, and describes some preliminary computational results which corroborate the experimental data.

Yes / Understanding the effect of physical parameters (e.g., temperature) on crystallisation dynamics is of paramount importance for the synthesis of nanocrystals of well‐defined sizes and geometries. However, imaging nucleation and growth is an experimental challenge owing to the resolution required and the kinetics involved. Here, by using an aberration‐corrected transmission electron microscope, we report the fabrication of precious metal nanocrystals from nuclei and the identification of the dynamics of their nucleation at three different temperatures (20, 50, and 100 °C). A fast, and apparently linear, acceleration of the growth rate is observed against increasing temperature (78.8, 117.7, and 176.5 pm min−1, respectively). This work appears to be the first direct observation of the effect of temperature on the nucleation and growth of metal nanocrystals. / The Royal Society. Grant Number: UF150295 Leverhulme Trust. Grant Number: ECF-2013-414 The Academy of Medical Sciences. Grant Number: SBF003\1170

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Proton-Exchange Membrane Fuel Cells are an alternative source of electricity generation for automobiles and stationary power plants. With increasing concerns on environmental issues, recent research has focused on maximizing the efficiency and durability as well as minimizing the costs of fuel cells. One of the main areas of research is optimizing the structure of the cathode catalyst layer. The main driving force of this thesis was the effective visualization of nanostructure of the ionomer, which is responsible for proton conduction in the cathode catalyst layer. However, challenges regarding sample preparation and radiation damage still need to be well understood. Different sample preparation techniques of catalyst inks and catalyst coated membranes were used for Scanning and Transmission Electron Microscopy, such as freeze fracturing, ultramicrotomy and Focused Ion Beam. Comparisons of the microstructure and chemical differences of all components, especially the ionomer, prepared by ultramicrotomy and Focused Ion Beam, was done with Transmission Electron Microscopy and Scanning Transmission X-ray Microscopy applied to the same catalyst coated membrane sample. Detailed spectroscopic information regarding components in both specimens was compared with C 1s and F 1s near edge X-ray absorption spectra recorded in a Scanning Transmission X-ray Microscope. Focused Ion Beam causes extensive damage to the carbon support and ionomer but prepares thinner sections than ultramicrotomy. This work makes it possible to understand the limitations of each sample preparation and compositional analysis technique in order to later apply one of them to image the ionomer in the catalyst layer at the nanoscale, hopefully using tomography techniques. / Thesis / Master of Materials Science and Engineering (MMatSE)

Inorganic and metal-organic framework materials possessing accessible and permanent pores are receiving tremendous attention. Among them, zeolites are the most famous class due to their wide applications on petrochemistry and gas separation. Besides zeolites, the other oxide framework materials are also intensively investigated because of their diverse structures and compositions. Metal-organic frameworks are built from metal clusters and organic linkers. By rational designing the reagent, the network with desired topology and functionality can be synthesized. For all of the framework materials mentioned above, to explore novel framework structures is important for improving properties and discovering new applications. This thesis includes the synthesis of zeolites and structure characterization for various types of inorganic framework materials. The zeolite synthesis conditions was exploited. With the optimized condition, the zeolite ITQ-33 was synthesized as single crystals. From the single crystal X-ray diffraction data, the disorder in the structure is discovered and explained. Following the topic of disorder and twinning, we proposed a novel method of solving structure of pseudo-merohedric twinning crystal by using an example of a metal-organic complex crystal. Then we also showed methods for solving structures of high complexity and nano-crystal by using mainly powder X-ray diffraction and transmission electron microscopy. Four examples were shown in chapter 4 including open-framework germanates and metal-organic frameworks. / <p>At the time of the doctoral defence the following paper was unpublished and a status as follows: Paper  4: Manuscript</p>

Single-particle reconstruction technique is one of the major approaches to studying ribosome structure and membrane proteins. In this thesis, I report the use of time-resolved cryo-EM technique to study the structure of short-lived ribosome complexes and conventional cryo-EM technique to study the structure of ribosome complexes and membrane proteins. The thesis consists three parts. The first part is the development of time-resolved cryo-EM technique. I document the protocol for how to capture short-lived states of the molecules with time-resolved cryo-EM technique using microfluidic chip. Working closely with Dr. Lin’s lab at Columbia University Engineering Department, I designed and tested a well-controlled and effective microspraying-plunging method to prepare cryo-grids. I demonstrated the performance of this device by a 3-Å reconstruction from about 4000 particles collected on grids sprayed with apoferritin suspension. The second part is the application of time-resolved cryo-EM technique for studying short-lived ribosome complexes in bacteria translation processes on the time-scale of 10-1000 ms. I document three applications on bacterial translation processes. The initiation project is collaborated with Dr. Gonzalez’s lab at Chemistry Department, Columbia University. The termination and recycling projects are collaborated with Dr. Ehrenberg’s lab at Department of Cell and Molecular Biology, Uppsala University. I captured and solved short-lived ribosome intermediates complexes in these processes. The results demonstrate the power of time-resolved cryo-EM to determine how a time-ordered series of conformational changes contribute to the mechanism and regulation of one of the most fundamental processes in biology. The last part is the application of conventional cryo-EM technique to study ribosome complexes and membrane proteins. This part includes five collaboration projects. Human GABA(B) receptor project is the collaboration with Dr. Fan at Department of Pharmacology, Columbia University. Cyclic nucleotide-gated (CNG) channels project is the collaboration with Dr. Yang at Department of Biological Sciences, Columbia University. The cryo-EM study of Ybit-70S ribosome complex and Cystic fibrosis transmembrane conductance regulator (CFTR) project are the collaboration with Dr. Hunt at Department of Biological Sciences, Columbia University. The cryo-EM study of native lipid bilayer in membrane protein transporter is the collaboration with Dr. Hendrickson at Department of Biochemistry and Molecular Biophysics, Columbia University and Dr. Guo at Department of Medicinal Chemistry, Virginia Commonwealth University.