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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.
591

Contributions to Estimation and Testing Block Covariance Structures in Multivariate Normal Models

Liang, Yuli January 2015 (has links)
This thesis concerns inference problems in balanced random effects models with a so-called block circular Toeplitz covariance structure. This class of covariance structures describes the dependency of some specific multivariate two-level data when both compound symmetry and circular symmetry appear simultaneously. We derive two covariance structures under two different invariance restrictions. The obtained covariance structures reflect both circularity and exchangeability present in the data. In particular, estimation in the balanced random effects with block circular covariance matrices is considered. The spectral properties of such patterned covariance matrices are provided. Maximum likelihood estimation is performed through the spectral decomposition of the patterned covariance matrices. Existence of the explicit maximum likelihood estimators is discussed and sufficient conditions for obtaining explicit and unique estimators for the variance-covariance components are derived. Different restricted models are discussed and the corresponding maximum likelihood estimators are presented. This thesis also deals with hypothesis testing of block covariance structures, especially block circular Toeplitz covariance matrices. We consider both so-called external tests and internal tests. In the external tests, various hypotheses about testing block covariance structures, as well as mean structures, are considered, and the internal tests are concerned with testing specific covariance parameters given the block circular Toeplitz structure. Likelihood ratio tests are constructed, and the null distributions of the corresponding test statistics are derived.
592

The Prophetic Chronotope and the Sexual Revolution in Baron Ludwig von Reizenstein's The Mysteries of New Orleans

Walker, Timothy 11 August 2015 (has links)
This thesis examines the role of the prophetic chronotope as a form of alternate, circular time in Baron Ludwig von Reizenstein’s gothic romance, The Mysteries of New Orleans. As the novel’s temporal structure seemingly contains the professed slave revolution through a manipulation of a linear prophetic sequence into circular time, Reizenstein simultaneously portrays a sexual revolution within the closed temporal system; however, as he localizes the sexual revolution in the “real time” of the reader through the inclusion of extra-textual artifacts, the novel’s closed system of alternate, circular time sustains a fissure, loosing all revolutionary potential, slave and sexual, into the reader’s temporality. Reizenstein compares sexual slavery, social restrictions on sexual expression, to chattel slavery, but recognizes it as endemic form of bondage affecting every race; therefore, Reizenstein uses chattel slavery as a ubiquitous circumstance in the U.S. South to identify other covert forms of slavery. In the end, the slave and sexual revolutions become the same conflict, and the restoration of beauty becomes its primary aim.
593

The Role of Substrate Stiffness on the Dynamics of Actin Rich Structures and Cell Behavior

Zeng, Yukai 01 November 2014 (has links)
Cell-substrate interactions influence various cellular processes such as morphology, motility, proliferation and differentiation. Actin dynamics within cells have been shown to be influenced by substrate stiffness, as NIH 3T3 fibroblasts grown on stiffer substrates tend to exhibit more prominent actin stress fiber formation. Circular dorsal ruffles (CDRs) are transient actin-rich ring-like structures within cells, induced by various growth factors, such as the platelet-derived growth factor (PDGF). CDRs grow and shrink in size after cells are stimulated with PDGF, eventually disappearing ten of minutes after stimulation. As substrate stiffness affect actin structures and cell motility, and CDRs are actin structures which have been previously linked to cell motility and macropinocytosis, the role of substrate stiffness on the properties of CDRs in NIH 3T3 fibroblasts and how they proceed to affect cell behavior is investigated. Cells were seeded on Poly-dimethylsiloxane (PDMS) substrates of various stiffnesses and stimulated with PDGF to induce CDR formation. It was found that an increase in substrate stiffness increases the lifetime of CDRs, but did not affect their size. A mathematical model of the signaling pathways involved in CDR formation is developed to provide insight into this lifetime and size dependence, and is linked to substrate stiffness via Rac-Rho antagonism. CDR formation did not affect the motility of cells seeded on 10 kPa stiff substrates, but is shown to increase localized lamellipodia formation in the cell via the diffusion of actin from the CDRs to the lamellipodia. To further probe the influence of cell-substrate interactions on cell behavior and actin dynamics, a two dimensional system which introduces a dynamically changing, reversible and localized substrate stiffness environment is constructed. Cells are seeded on top of thin PDMS nano-membranes, and are capable of feeling through the thin layer, experiencing the stiffness of the polyacrylamide substrates below the nano-membrane. The membranes are carefully re-transplanted on top of other polyacrylamide substrates with differing stiffnesses. This reversible dynamic stiffness system is a novel approach which would help in the investigation of the influence of reversible dynamic stiffness environments on cell morphology, motility, proliferation and differentiation in various cells types.
594

Återbruksbyn : Grafiskt arbete som identifierar Återbruksbyn i Växjö

Lamme, Anton January 1900 (has links)
Detta projektet handlar om att ge Återbruksbyn i Växjö en grafisk identitet och profil. Återbruksbyn är ett arbete startat av Växjö kommun och kooperativet Macken som handlar om att bygga en mötesplats för oss som vill byta, köpa, sälja, skänka och återbruka begagnade saker i stället för att slänga dem. Det är en plats som kommer fokusera på cirkulär ekonomi och introducera detta system som ett alternativ till det vi har i dagsläget. Min roll och syftet med detta projekt har varit att analysera verksamheten och skapa en logotyp med tillhörande grafisk profil där de äkta värderingarna visas och representeras på ett korrekt sätt. Detta är min process. / This project is about creating a graphic identity and profile for Återbruksbyn, Växjö. Återbruksbyn is a project created by Växjö municipality and the cooperative Macken, and it is about building a central space and meeting point for people who want to buy, sell, exchange, give away and reuse old products instead of throwing them away. It is a place that focuses on circular economy and wants to introduce this alternative system to the people of Växjö. My role and purpose with this project has been to analyse Återbruksbyn and its values, and through that, create a graphic identity that reflects these values and goals. This is my process.
595

New algorithm for efficient Bloch-waves calculations of orientation-sensitive ELNES

Tatsumi, Kazuyoshi, Muto, Shunsuke, Rusz, Ján 02 1900 (has links)
No description available.
596

Parameter-free extraction of EMCD from an energy-filtered diffraction datacube using multivariate curve resolution

Rusz, J., Tatsumi, K., Muto, S. 02 1900 (has links)
No description available.
597

The spectroscopic characterization of mitochondrial porin in membrane mimetic systems

Bay, Denice Colleen 08 January 2007 (has links)
Voltage-dependent anion-selective channels (VDAC), or mitochondrial porins,regulate the flow of metabolites across the mitochondrial outer membrane. They presumably span the membrane as β-barrels, but the residues forming the individual β-strands are unknown. This information is essential for understanding the structure and function of the protein. Using Neurospora VDAC as a template, published data were reassessed to delineate a unified model for porin structure Bay and Court 2002, which was subsequently refined in collaboration with Greg Runke Runke et al. 2006. The focus of this work was the development and analysis of systems for maintaining high levels of folded porin for the acquisition of high resolution data needed for model testing. The conformation of hexahistidinyl-tagged Neurospora porin in detergent was probed by fluorescence, near-UV circular dichroism and ultraviolet absorption spectroscopy. Derivatives of tryptophan and tyrosine were also examined by fluorescence spectroscopy and UV absorbance spectroscopy to model the interactions between the detergents and the amino acid side chains in the protein. Detergent-specific levels of β-strand and tyrosine exposure were observed. In all cases, the two tryptophan residues reside in weakly asymmetric, hydrophobic environments, suggesting transient tertiary interactions. Porin solubilized in these detergents forms functional channels in liposomes and membrane insertion is accompanied by increased levels of β-strand and loss of protease sensitivity. These data were used to develop mixed detergent folding systems. A mixture of SDS and dodecyl-β-D-maltopyranoside (DDM)supports a β-strand rich conformation at high protein concentrations. The tertiary contacts and protease resistance of the SDS/DDM solubilized porin are very similar to those of the protein following reconstitution into liposomes. Finally, the role of sterols in porin folding was examined, as the addition of sterols to detergent-solubilized VDAC is required for channel formation in artificial membranes. Sterols do not alter the secondary structure of VDAC, and subtle alterations to tertiary interactions were detected, suggesting that sterols do not promote an insertion-competent structure, but rather facilitate insertion into artificial bilayers. In summary, this analysis of the folded states of detergent-solubilized porin has revealed a system that maintains high concentrations of mitochondrial porin in a state that is very promising for structural studies.
598

Experimental Evaluation of Flow-Measurement-Based Drag Estimation Methods

Neatby, Holly C. January 2014 (has links)
The accuracy of existing methods for estimating the drag based on experimental flow field measurements were assessed for two-dimensional bodies. The effects of control volume boundary placement and inherent simplifying assumptions were also investigated. Wind tunnel experiments were performed on a circular cylinder operating at a Reynolds number of 8,000 and 20,000, and on a NACA 0018 airfoil operating at a chord Reynolds number of 100,000 for three angles of attack (α), specifically, 5◦, 10◦, and 15◦. The circular cylinder experiments fall within the the shear layer transition flow regime. Airfoil investigations span both types of flow development common to low Reynolds number airfoil operation. For α = 5◦ and 10◦, a separation bubble forms on the upper surface of the airfoil, while, for α = 15◦, the flow separates without reattaching, resulting in a stalled airfoil. Wake velocity and pressure measurements were performed at several downstream locations to investigate the impact of control volume boundary placement. Wake profiles were measured between 3 and 40 diameters downstream from the circular cylinder axis and between 1 and 4.5 chord lengths from the trailing edge of the airfoil. In addition to wake profiles, the outer flow velocity variation was quantified to investigate the appropriate location to measure freestream flow characteristics in a test section with streamwise-varying outer flow conditions. The results show that drag estimates are strongly dependent on the streamwise position of the measured wake profile for all methods investigated. Drag estimates improved, and streamwise variation decreased, with increasing streamwise position of the flow measurements. For the pressure based method examined, wake measurements should be taken at least 10 times the projected model height downstream of the model. In the case of the circular cylinder, this is equivalent to 10 diameters and, for the airfoil investigated, it is approximately 1 chord length from the trailing edge. For the methods relying on velocity measurements, acceptable estimates of drag were possible when based on measurements taken at least 30 projected heights downstream, i.e., 30 diameters for the circular cylinder and 3 chord lengths for the airfoil model investigated. The findings highlight the importance of providing a detailed description of the methodology and experimental implementation for drag estimates based on flow field measurements. Finally the study offers guidelines for implementing momentum integral based drag calculations in future investigations.
599

The spectroscopic characterization of mitochondrial porin in membrane mimetic systems

Bay, Denice Colleen 08 January 2007 (has links)
Voltage-dependent anion-selective channels (VDAC), or mitochondrial porins,regulate the flow of metabolites across the mitochondrial outer membrane. They presumably span the membrane as β-barrels, but the residues forming the individual β-strands are unknown. This information is essential for understanding the structure and function of the protein. Using Neurospora VDAC as a template, published data were reassessed to delineate a unified model for porin structure Bay and Court 2002, which was subsequently refined in collaboration with Greg Runke Runke et al. 2006. The focus of this work was the development and analysis of systems for maintaining high levels of folded porin for the acquisition of high resolution data needed for model testing. The conformation of hexahistidinyl-tagged Neurospora porin in detergent was probed by fluorescence, near-UV circular dichroism and ultraviolet absorption spectroscopy. Derivatives of tryptophan and tyrosine were also examined by fluorescence spectroscopy and UV absorbance spectroscopy to model the interactions between the detergents and the amino acid side chains in the protein. Detergent-specific levels of β-strand and tyrosine exposure were observed. In all cases, the two tryptophan residues reside in weakly asymmetric, hydrophobic environments, suggesting transient tertiary interactions. Porin solubilized in these detergents forms functional channels in liposomes and membrane insertion is accompanied by increased levels of β-strand and loss of protease sensitivity. These data were used to develop mixed detergent folding systems. A mixture of SDS and dodecyl-β-D-maltopyranoside (DDM)supports a β-strand rich conformation at high protein concentrations. The tertiary contacts and protease resistance of the SDS/DDM solubilized porin are very similar to those of the protein following reconstitution into liposomes. Finally, the role of sterols in porin folding was examined, as the addition of sterols to detergent-solubilized VDAC is required for channel formation in artificial membranes. Sterols do not alter the secondary structure of VDAC, and subtle alterations to tertiary interactions were detected, suggesting that sterols do not promote an insertion-competent structure, but rather facilitate insertion into artificial bilayers. In summary, this analysis of the folded states of detergent-solubilized porin has revealed a system that maintains high concentrations of mitochondrial porin in a state that is very promising for structural studies.
600

Application of translational addition theorems to electrostatic and magnetostatic field analysis for systems of circular cylinders

Machynia, Adam 11 April 2012 (has links)
Analytic solutions to the static and stationary boundary value field problems relative to an arbitrary configuration of parallel cylinders are obtained by using translational addition theorems for scalar Laplacian polar functions, to express the field due to one cylinder in terms of the polar coordinates of the other cylinders such that the boundary conditions can be imposed at all the cylinder surfaces. The constants of integration in the field expressions of all the cylinders are obtained from a truncated infinite matrix equation. Translational addition theorems are available for scalar cylindrical and spherical wave functions but such theorems are not directly available for the general solution of the Laplace equation in polar coordinates. The purpose of deriving these addition theorems and applying them to field problems involving systems of cylinders is to obtain exact analytic solutions with controllable accuracies, thereby, yielding benchmark solutions to validate other approximate numerical methods.

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