Thesis (Ph. D.)--Washington State University, August 2009. / Title from PDF title page (viewed on Aug. 4, 2009). "Department of Civil and Environmental Engineering." Includes bibliographical references (p. 110-111).

Thesis (Ph.D.)--Virginia Commonwealth University, 2010. / Prepared for: Dept. of Biochemistry. Title from title-page of electronic thesis. Bibliography: leaves 106-117

The tyrosine kinase receptor Tie-2 is expressed on the surface of endothelial cells and is necessary for angiogenesis and vascular stability. To date, the best characterized ligands for Tie-2 are Angiopoietin-1 (Ang-1) and Angiopoietin-2 (Ang-2). Ang-1 has been identified as the main activating ligand for Tie-2 while the role of Ang-2 has been controversial since its discovery; some studies reported Ang-2 as a Tie-2 antagonist while others described Ang-2 as a Tie-2 agonist. The purpose of this thesis was to understand: (1) how the receptor Tie-2 is regulated by Ang-1 and Ang-2 in endothelial cells, (2) to compare the effects of Ang-1 and Ang-2, and (3) to determine the arrangement and distribution of Tie-2 in endothelial cells. The research presented in this thesis indicates that Tie-2 is arranged in variably sized clusters on the endothelial cell surface. Clusters of Tie-2 were expressed on all surfaces of cells: on the apical plasma membrane, on the tips of microvilli, and on the basolateral plasma membrane. When endothelial cells were stimulated with Ang-1, Tie-2 was rapidly internalized and degraded. Upon Ang-1 stimulation, Tie-2 localized to clathrin-coated pits on all surfaces of endothelial cells indicating that one pathway mediating Tie-2 internalization is through clathrin-coated pits. After activation of Tie-2, Ang-1 dissociates from the endothelial cell surface and accumulates in the surrounding medium. When experiments were repeated with Ang-2, it was discovered that Ang-2 induced all of the same effects on Tie-2 as Ang-1 but at a much reduced level and rate, indicating that Ang-2 likely functions as a partial agonist for Tie-2 in endothelial cells. / PhD

Master of Science / Department of Civil Engineering / Robert J. Peterman / Prestressed concrete is commonly used for bridges, pavement and railroad ties because of economic advantages in cost, sustainability service life, and environmental friendliness. In general concrete design standard, the ultimate moment strength in flexure design is computed by finding the equilibrium of the internal force in the section (the compressive force in concrete and tension force in the steel and reinforcement). To predict tension force in steel one generally applies the 7-wire low-relaxation prestressing strand equation from the PCI manual even though the design employed prestressing wires instead of strand. The other method is to use equations from the ACI Code which is over conservative. Considering both approaches are lack accuracy, this research will provide an accurate estimation of the stress in prestressing wires through an experimental program and analytical modeling. The real stress-strain curves are collected through experimental testing in 13 types of prestressing wire. Experimental results are then used for modeling existing equations. As a result a more precise estimation is achieved. Additionally, this research simplifies the procedure for utilizing the equations which offers convenience in practical application.

The development of a functional vascular system is impinged upon the restructuring of a primitive vasculature into a more complex and mature vessel network via a process known as angiogenesis. Of particular importance to this vascular remodeling process is the function of the Tek/Tie-2 receptor tyrosine kinase. Mouse gene-targeting studies have shown that Tie-2 deficient embryos succumb to embryonic death at embryonic day 9.5 due to insufficient sprouting and remodeling of the primary capillary plexus. Over the years, the functions and the signaling pathways downstream of Tie-2 receptor have been elucidated; however, the repertoire of genes controlled by Tie-2 signaling leading to angiogenesis had not been studied. To identify the underlying genetic mechanisms, transcriptomes from Tie-2 wild-type (WT) and knockout (KO) embryonic day 8.5 yolk sac tissues were quantitatively analyzed using a gene expression profiling technique called Serial Analysis of Gene Expression (SAGE). Tie-2 WT and KO SAGE libraries were constructed, sequenced and compared to identify genes that were differentially expressed. A list of candidate genes was selected for further validation using semi-quantitative PCR that included 4933402E13Rik, a novel transcript encoding a protein product containing the melanoma-associated antigen (MAGE) domain. Initial characterization of 4933402E13Rik suggested a murine-specific expression profile restricted to the yolk sac, embryo, placenta, testis, endothelial and embryonic stem cells. The expression of 4933402E13Rik in mouse endothelial cells was found to be regulated by Tie-2 signaling since down-regulation of Tie-2 level via siRNA knockdown resulted in decreased 4933402E13Rik mRNA expression. In contrast, stimulation of Tie-2 in mouse endothelial cells using its ligand, Angiopoietin-1, increased 4933402E13Rik mRNA levels. Additionally, 4933402E13Rik expression was found to be modulated through epigenetics especially by histone deacetylation. Mouse endothelial cells treated with Trichostatin A, a potent inhibitor of histone deacetylase, led to an increase in the expression of 4933402E13Rik. Taken together, the results of this study shed new insight on the repertoire of genes implicated in Tie-2 signaling. The identification of 4933402E13Rik as a novel gene modulated by Tie-2 provides a new avenue of research on Tie-2 signaling that may contribute further to our understanding of vascular development.

The development of a functional vascular system is impinged upon the restructuring of a primitive vasculature into a more complex and mature vessel network via a process known as angiogenesis. Of particular importance to this vascular remodeling process is the function of the Tek/Tie-2 receptor tyrosine kinase. Mouse gene-targeting studies have shown that Tie-2 deficient embryos succumb to embryonic death at embryonic day 9.5 due to insufficient sprouting and remodeling of the primary capillary plexus. Over the years, the functions and the signaling pathways downstream of Tie-2 receptor have been elucidated; however, the repertoire of genes controlled by Tie-2 signaling leading to angiogenesis had not been studied. To identify the underlying genetic mechanisms, transcriptomes from Tie-2 wild-type (WT) and knockout (KO) embryonic day 8.5 yolk sac tissues were quantitatively analyzed using a gene expression profiling technique called Serial Analysis of Gene Expression (SAGE). Tie-2 WT and KO SAGE libraries were constructed, sequenced and compared to identify genes that were differentially expressed. A list of candidate genes was selected for further validation using semi-quantitative PCR that included 4933402E13Rik, a novel transcript encoding a protein product containing the melanoma-associated antigen (MAGE) domain. Initial characterization of 4933402E13Rik suggested a murine-specific expression profile restricted to the yolk sac, embryo, placenta, testis, endothelial and embryonic stem cells. The expression of 4933402E13Rik in mouse endothelial cells was found to be regulated by Tie-2 signaling since down-regulation of Tie-2 level via siRNA knockdown resulted in decreased 4933402E13Rik mRNA expression. In contrast, stimulation of Tie-2 in mouse endothelial cells using its ligand, Angiopoietin-1, increased 4933402E13Rik mRNA levels. Additionally, 4933402E13Rik expression was found to be modulated through epigenetics especially by histone deacetylation. Mouse endothelial cells treated with Trichostatin A, a potent inhibitor of histone deacetylase, led to an increase in the expression of 4933402E13Rik. Taken together, the results of this study shed new insight on the repertoire of genes implicated in Tie-2 signaling. The identification of 4933402E13Rik as a novel gene modulated by Tie-2 provides a new avenue of research on Tie-2 signaling that may contribute further to our understanding of vascular development.

No description available.

No description available.

On open-deck railroad bridges, the crossties (sleepers) are directly supported by the bridge superstructure and anchored with deck tie fasteners such as hook bolts. These fasteners provide lateral resistance for the bridge ties. Currently there are no provisions to assist in the calculation of lateral resistance provided by railroad ties on open-deck bridges, and as a result there are no specific requirements for the spacing of deck tie fasteners. This has led to different design practices specific to each railroad, and inconsistent fastener spacing in existing railroad bridges. A research plan was conducted to experimentally quantify the lateral resistance of timber crossties on open-deck plate girder bridges using different wood species and types of fasteners. Experimental tests were conducted on five different species of timber crossties (beech, sycamore, southern pine, Douglas-fir, and oak) with three different types of fasteners (square body hooks bolt, forged hook bolts, and Quick-Set Anchors). A structural test setup simulated one half of an open-deck bridge with a smooth-top steel plate girder, and hydraulic actuators to apply both vertical and horizontal load to a railroad tie specimen. The three main contributions to lateral resistance on open-deck bridges were identified as friction resistance between tie and girder due to vertical load from a truck axle, resistance from the fastener, and resistance from dapped ties bearing against the girder flange. Initial testing isolated each component of lateral resistance to determine the friction coefficient between tie and girder as well as resistance from just the fastener itself. Additional testing combined both vertical load and fastener to determine whether or not the overall resistance is simply the sum of the friction and fastener resistance. Results indicated that friction resistance varies based on the magnitude of vertical axle load, species of wood, and creosote retention in the tie, while fastener resistance varies based on type of fastener and lateral displacement of the tie. An approximation of the lateral resistance as a function of lateral displacement was established depending on the vertical load, type of hook bolt, and coefficient of friction between tie and girder. The approximation was used in a structural analysis, which modelled a section of railroad track as a beam supported by non-linear springs spaced at discrete distance. Based on anticipated lateral loads, the analysis was used to determine a preliminary chart for a safe and economical fastener spacing for a railroad track based on type of hook bolt, creosote retention, tie species, and curvature of bridge. / Master of Science / On open-deck railroad bridges, the crossties are directly supported by the steel bridge girders and connected to the girders with fasteners as hook bolts. These fasteners provide lateral resistance for the bridge ties. Currently there are no provisions to assist in the calculation of lateral resistance provided by railroad ties on open-deck bridges, and as a result there are no specific requirements for the spacing of deck tie fasteners. This has led to different design practices specific to each railroad, and inconsistent fastener spacing in existing railroad bridges. A research plan was conducted to experimentally quantify the lateral resistance of timber crossties on open-deck plate girder bridges using different wood species and types of fasteners. Experimental tests were conducted on five different species of timber crossties (beech, sycamore, southern pine, Douglas-fir, and oak) with three different types of fasteners (square body hooks bolt, forged hook bolts, and Quick-Set Anchors). A structural test setup simulated one half of an open-deck bridge with a smooth-top steel plate girder, and hydraulic actuators to apply both vertical and horizontal load to a railroad tie specimen. The three main contributions to lateral resistance on open-deck bridges were identified as friction resistance between tie and girder due to vertical load from a truck axle, resistance from the fastener, and resistance from dapped ties bearing against the girder flange. Initial testing isolated each component of lateral resistance to determine the friction coefficient between tie and girder as well as resistance from just the fastener itself. Additional testing combined both vertical load and fastener to determine whether or not the overall resistance is simply the sum of the friction and fastener resistance. Results indicated that friction resistance varies based on the magnitude of vertical axle load, species of wood, and creosote retention in the tie, while fastener resistance varies based on type of fastener and lateral displacement of the tie. An approximation of the lateral resistance as a function of lateral displacement was established depending on the vertical load, type of hook bolt, and coefficient of friction between tie and girder. The approximation was used in a structural analysis, and the analysis was used to determine a preliminary chart for a safe and economical fastener spacing for a railroad track based on type of hook bolt, creosote retention, tie species, and curvature of bridge.

No description available.