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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Characterizing cavity containing materials using electron microscopy : A study of metal oxides, mesoporous crystals and porous material containing nanosized metal-particles

Klingstedt, Miia January 2011 (has links)
This thesis concerns the characterization of novel materials by utilizing electron microscopy techniques. The examined materials contain cavities with certain attributes that enables desired properties for applications such as gas separation, catalysis and fuel cells. The specimens concerned herein belong to the following groups of materials: Metal oxides in the Sb-W-Mo-O system; ordered mesoporous silicas and carbons; hollow spheres containing Au-nanoparticles; zeolite LTA incorporated with mesopores; metal organic frameworks doped with nickel. With scanning electron microscopy (SEM) and transmission electron microscopy (TEM) you get vast possibilities within the field of characterization. This thesis utilizes conventional electron microscopy techniques such as imaging, energy-dispersive spectroscopy and electron diffraction as well as reconstruction techniques, such as exit-wave reconstruction, electron tomography and electron crystallography. Furthermore, the sample preparation technique cross-section polishing has been used in conjunction with low voltage SEM studies. The scientific approach is to gain knowledge of nano-sized cavities in materials, in particular their shape, size and content. The cavities often have irregularities that originates from the synthesis procedure. In order to refine the synthesis and to understand the properties of the material it is required to carefully examine the local variations. Therefore average characterization techniques such as crystallography needs to be combined with local examination techniques such as tomography. However, some of the materials are troublesome to investigate since they to some extent bring limitations to or gets easily damaged by the applied characterization technique. For the development of novel materials it is essential to find means of overcoming also these obstacles. / At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 6: Submitted.
2

Synthesis of electron dense labels and structural analysis of multiprotein aggregates

Yang, Heechung. January 1985 (has links)
Thesis (Ph. D.)--University of Wisconsin--Madison, 1985. / Typescript. Vita. Includes bibliographical references (leaves 268-283).
3

Theoretical aspects of scanning transmission electron microscopy /

Findlay, Scott David. January 2005 (has links)
Thesis (Ph.D.)--University of Melbourne, Dept. of Physics, 2005. / Typescript. Includes bibliographical references (leaves 205-223).
4

Visualizing the Structural Basis of Genome Silencing

Fussner, Eden Margaret 19 June 2014 (has links)
Eukaryotic genomes must be folded and compacted to fit within the restricted volume of the nucleus. This folding, and the subsequent organization of the genome, reflects both the transcription profile of the cell and of the specific cell type. A dispersed, mesh-like chromatin configuration, for example, is characteristic of a pluripotent stem cell. Here we show that the acquisition of the pluripotent state during somatic cell reprogramming is coincident with the disruption of compact heterochromatin domains. Using Electron Spectroscopic Imaging (ESI), I made the surprising observation that the heterochromatin domains of the induced pluripotent and of the parental somatic cell contained 10 nm chromatin fibres. Since ESI generates projection images, the precise three-dimensional organization of all chromatin fibres within these domains could not be elucidated. To circumvent this limitation, I developed an electron microscopy technique that combines ESI with tomography. Using this approach, I found that both heterochromatin domains and the surrounding euchromatin of murine pluripotent cells, fibroblasts, and somatic tissues are in fact organized entirely as 10 nm chromatin fibres. This challenges the current paradigm that most, if not all, of the genome exists as 30 nm and higher-order chromatin fibre assemblies. Rather than transitions between 10 nm and 30 nm fibres, I propose that the organization and thus the regulation of the genome is achieved by the bending and folding of 10 nm chromatin fibres into discrete domains in a cell type-specific manner.
5

Visualizing the Structural Basis of Genome Silencing

Fussner, Eden Margaret 19 June 2014 (has links)
Eukaryotic genomes must be folded and compacted to fit within the restricted volume of the nucleus. This folding, and the subsequent organization of the genome, reflects both the transcription profile of the cell and of the specific cell type. A dispersed, mesh-like chromatin configuration, for example, is characteristic of a pluripotent stem cell. Here we show that the acquisition of the pluripotent state during somatic cell reprogramming is coincident with the disruption of compact heterochromatin domains. Using Electron Spectroscopic Imaging (ESI), I made the surprising observation that the heterochromatin domains of the induced pluripotent and of the parental somatic cell contained 10 nm chromatin fibres. Since ESI generates projection images, the precise three-dimensional organization of all chromatin fibres within these domains could not be elucidated. To circumvent this limitation, I developed an electron microscopy technique that combines ESI with tomography. Using this approach, I found that both heterochromatin domains and the surrounding euchromatin of murine pluripotent cells, fibroblasts, and somatic tissues are in fact organized entirely as 10 nm chromatin fibres. This challenges the current paradigm that most, if not all, of the genome exists as 30 nm and higher-order chromatin fibre assemblies. Rather than transitions between 10 nm and 30 nm fibres, I propose that the organization and thus the regulation of the genome is achieved by the bending and folding of 10 nm chromatin fibres into discrete domains in a cell type-specific manner.
6

Spatial resolution in STEM EDX microanalysis

Kerr, R. T. January 1985 (has links)
No description available.
7

Microstructure studies of various oxide materials using electron microscopy

張艷蕾, Cheung, Yim-lui. January 2002 (has links)
published_or_final_version / Physics / Master / Master of Philosophy
8

Studies of dissolved species and suspended particulate matter in the freshwater systems of Signy Island, maritime Antarctic

Caulkett, Andrew Paul January 2000 (has links)
No description available.
9

Development of methods for the analysis of structure and composition of biological tissues using low temperature electron microscopy

Oates, Kenneth January 1984 (has links)
No description available.
10

An EBSD study on mapping of small orientation differences in lattice mismatched heterostructures /

Tao, Xiaodong, January 2003 (has links)
Thesis (Ph. D.)--Lehigh University, 2004. / Includes vita. Includes bibliographical references (leaves 184-195).

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