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acase@tulane.edu / Progress towards understanding the underlying mechanisms of pelvic organ prolapse (POP) is limited, in part, due to a lack of information on the biomechanical properties and microstructural composition of the vaginal wall. Compromised vaginal wall integrity is thought to contribute to pelvic floor disorders. In particular, disruption of the elastin metabolism within the vaginal wall extracellular matrix has been highly implicated in POP pathogenesis; however, the role of elastin within the vaginal wall is not fully understood. In addition to the information produced from uniaxial testing, biaxial extension-inflation tests performed over a range of physiological values could provide additional insights into vaginal wall mechanical behavior (i.e. axial coupling and anisotropy) while preserving in vivo tissue geometry. Thus, the objective of this study is to identify the role of elastin in vaginal wall mechanics using physiologically relevant experimental and mathematical approaches. Our specific aims are thus: 1. Develop biaxial mechanical testing methods for assessing the mechanical properties of the murine vaginal wall in a physiological manner. 2. Establish a microstructurally-motivated constitutive model capable of describing the biaxial extension-inflation response of the nonpregnant murine vaginal wall. 3. Quantify the role of elastin in murine vaginal mechanical properties through enzymatic digestion of elastin with elastase.Vaginal tissue from female C57BL/6 mice underwent pressure-diameter and force-length preconditioning and testing within a pressure myograph device before and after elastase digestion. In order to mathematically interpret biaxial data, vaginal tissue was modeled using a 2D membrane approach. Several constitutive models were evaluated on their ability to describe vaginal wall mechanical behavior. Elastase digestion induced marked changes in biaxial mechanical properties, suggesting that elastin may play an important role in vaginal wall mechanical function. Constitutive model evaluation resulted in the selection of a diagonal two-fiber family strain energy function and suggests that collagen fibers within the vaginal wall extracellular matrix (ECM) may be primarily oriented diagonally with a slight preference towards the circumferential direction. Further, our results suggest that elastin-collagen interactions may be important for vaginal wall homeostasis. The present findings may help to understand the underlying mechanisms of POP and aid in the development of growth and remodeling models for improved assessment and prediction of changes in structure-function relationships with prolapse development. / 0 / Katy Robison

Thesis (Ph.D.)--McMaster University, 2005. / Supervisor: Daniel Ewing. Includes bibliographical references (p. 139-146).

Knowledge of energy deposition in biological cells at nanometer dimensions is essential to understand the biological effects of radiation. This work has resulted in the development of a practical tool to study such energy deposition experimentally, at nanometer dimensions. The main contribution of this research is the design of a cylindrical wall-less proportional counter of 1mm height by 1mm diameter. A wall-less detector (also called grid-walled detector) overcomes the so-called “wall effect”, an experimental artifact that introduces distortions in the radiation energy measurements. An important feature of this detector that distinguishes it from other detectors is its modular design. This allows the detector to be repaired or modified, when necessary, without having to completely disassemble it. Novel design techniques were adopted resulting in a functional detector that can simulate cellular sites as small as 10 nanometers, approximately the size of many molecules in the cell. The detector was tested with a 1 microcurie sealed Am-241 source, which primarily emits monoenergetic alpha particles of energy 5.57 MeV. Microdosimetric spectra analysis for alpha particles and its delta rays from Am-241 were performed for simulated site sizes ranging from 500nm to 10nm. Initial studies to validate the detector design have confirmed good detector performance. We believe this work will serve as a vital platform for bridging the experimentally measured energy spectra to the biological effects of alpha and delta radiations.

The MIDPLY shear wall has been developed to be used as a structural system for severe earthquakes. This type of construction has emerged as a viable alternative to concrete and steel for non-residential buildings. The MIDPLY shear wall utilizes a novel arrangement of sheathing and framing members with a special nailing technique. The MIDPLY joints have a different failure mode from that which is observed in standard shear walls. The study reported in this thesis focuses on the response of the MIDPLY shear wall due to monotonic and cyclic tests; the response of an increase size in the cross-section members of the MIDPLY shear wall; and also the evaluation of the design and performance of hold-down connections at the boundary end studs of the MIDPLY shear wall. Previously tested MIDPLY shear walls showed that the boundary end stud hold-down connection is a very critical component in the performance of the MIDPLY shear wall. After a simplified analysis of 2 possible hold-down connections (see Fig. 7, 8, 9 and 10), hold-down connection #2 was selected as the most viable option since it had the ability to withstand large lateral forces. For non-residential buildings we expect a larger lateral force when compared to residential buildings. Therefore the cross-section of the members in the MIDPLY shear wall was increased and the number of boundary end studs was modified. These measures resulted in an increase in the lateral force capacity with the use of hold-down connection #2. The experimental results were used to verify an analytical model representing the MIDPLY shear wall in load-displacement characteristics. Recommendations and future research will also be discussed to show the way for further performance optimization of the wall system.

Knowledge of energy deposition in biological cells at nanometer dimensions is essential to understand the biological effects of radiation. This work has resulted in the development of a practical tool to study such energy deposition experimentally, at nanometer dimensions. The main contribution of this research is the design of a cylindrical wall-less proportional counter of 1mm height by 1mm diameter. A wall-less detector (also called grid-walled detector) overcomes the so-called “wall effect”, an experimental artifact that introduces distortions in the radiation energy measurements. An important feature of this detector that distinguishes it from other detectors is its modular design. This allows the detector to be repaired or modified, when necessary, without having to completely disassemble it. Novel design techniques were adopted resulting in a functional detector that can simulate cellular sites as small as 10 nanometers, approximately the size of many molecules in the cell. The detector was tested with a 1 microcurie sealed Am-241 source, which primarily emits monoenergetic alpha particles of energy 5.57 MeV. Microdosimetric spectra analysis for alpha particles and its delta rays from Am-241 were performed for simulated site sizes ranging from 500nm to 10nm. Initial studies to validate the detector design have confirmed good detector performance. We believe this work will serve as a vital platform for bridging the experimentally measured energy spectra to the biological effects of alpha and delta radiations.

The primary objective of this thesis was to study how the behavior of flexure-dominated masonry shear-wall segments is affected by changes in the normalized axial load and the percentage of vertical reinforcement. Six reinforced masonry shear-wall segment were constructed and tested at the Ferguson Structural Engineering Laboratory of the University of Texas at Austin. Specimens were 96-in. wide and 96-in. high (aspect ratio equal to 1.0) and were tested with different combinations of axial load ratio (zero and 0.10) and vertical reinforcement ratios (0.33% and 0.16%). Specimens met the 2011 MSJC Code requirements for special reinforced masonry shear walls, and were tested under quasi-static in-plane reversed cyclic loads. The specimens exhibited predominantly flexural behavior, as expected. Specimens exhibited high displacement ductility (5.6 to 16.7), as expected for flexure-dominated specimens. Specimens constructed with "green" units behaved essentially like otherwise identical specimens constructed with conventional ("gray") units. / text

The primary objective of this thesis was to study how the behavior of flexure-dominated masonry shear-wall segments is affected by changes in the normalized axial load and the percentage of vertical reinforcement. Six reinforced masonry shear-wall segment were constructed and tested at the Ferguson Structural Engineering Laboratory of the University of Texas at Austin. Specimens were 96-in. wide and 96-in. high (aspect ratio equal to 1.0) and were tested with different combinations of axial load ratio (zero and 0.10) and vertical reinforcement ratios (0.33% and 0.16%). Specimens met the 2011 MSJC Code requirements for special reinforced masonry shear walls, and were tested under quasi-static in-plane reversed cyclic loads. The specimens exhibited predominantly flexural behavior, as expected. Specimens exhibited high displacement ductility (5.6 to 16.7), as expected for flexure-dominated specimens. Specimens constructed with “green” units behaved essentially like otherwise identical specimens constructed with conventional (“gray”) units. / text

The MIDPLY shear wall has been developed to be used as a structural system for severe earthquakes. This type of construction has emerged as a viable alternative to concrete and steel for non-residential buildings. The MIDPLY shear wall utilizes a novel arrangement of sheathing and framing members with a special nailing technique. The MIDPLY joints have a different failure mode from that which is observed in standard shear walls. The study reported in this thesis focuses on the response of the MIDPLY shear wall due to monotonic and cyclic tests; the response of an increase size in the cross-section members of the MIDPLY shear wall; and also the evaluation of the design and performance of hold-down connections at the boundary end studs of the MIDPLY shear wall. Previously tested MIDPLY shear walls showed that the boundary end stud hold-down connection is a very critical component in the performance of the MIDPLY shear wall. After a simplified analysis of 2 possible hold-down connections (see Fig. 7, 8, 9 and 10), hold-down connection #2 was selected as the most viable option since it had the ability to withstand large lateral forces. For non-residential buildings we expect a larger lateral force when compared to residential buildings. Therefore the cross-section of the members in the MIDPLY shear wall was increased and the number of boundary end studs was modified. These measures resulted in an increase in the lateral force capacity with the use of hold-down connection #2. The experimental results were used to verify an analytical model representing the MIDPLY shear wall in load-displacement characteristics. Recommendations and future research will also be discussed to show the way for further performance optimization of the wall system.