An increase in coronary disease prevalence and mortality highlights the growing need for therapies to treat atherosclerotic vessels. While current bypass procedures utilize autologous vessels for small caliber grafts, there is a big push towards the use of engineered tissues to bypass diseased portions of arteries. Cardiovascular tissue engineering is the emerging discipline that aims to create a functional substitute. Ideally, a tissue engineered blood vessel would possess the relevant cells and matrix proteins that interact in a physiologic manner and will respond to the environmental cues of the host. A particular obstacle to achieving appropriate vessel structure is the inclusion of elastin in a tissue engineered media equivalent. Rat arterial smooth muscle cells that were retrovirally mediated to overexpress versican V3 have been shown to have an enhanced expression of tropoelastin in vitro as well as in injury models. The unique tropoelastin expression by these adult cells was studied in the context of tissue engineered media equivalents. Changes to the extracellular matrix architecture and composition, stimulation with medium additives, and cyclic distension, were shown to increase tropoelastin synthesis in V3 versican overexpressing cells. This study not only expanded the characterization of V3 versican overexpressing smooth muscle cells, it also explored the novel use of these cells as a tropoelastin source in a tissue engineered media equivalent.

To be successful a tissue engineered small diameter blood vessel must be non-immunogenic, non-thrombogenic, have mechanical properties similar to native vessel and be vasoactive. The vascular media is responsible for the mechanical properties and the vasoactivity of the vessel. The collagen hydrogel approach has been long used and has many advantages, but has not yet achieved the mechanical integrity needed for implantation. No collagen-based tissue engineered vascular media has been shown to be vasoactive using culture techniques required to achieve the cell numbers needed to make a vascular graft. To study collagen synthesis, two model systems were used. Cells were seeded on top of an adsorbed collagen I or fibrin layer. Alternatively the cells were encapsulated in a collagen or fibrin hydrogel. Collagen I, decorin and biglycan synthesis was affected by both matrix type and presentation. After two weeks in culture the smooth muscle cells produce more type I collagen in the collagen based hydrogels then in the fibrin hydrogels and was used for further studies. The collagen based tissue engineered vascular media produced a consistent vasoactive response between two and eight weeks of culture. The smooth muscle cells have functional endothelin, kinin, adrenergic, serotonergic and purinergic receptors. The application of cyclic strain improves both the tissue strength and the contractile response. Use of transforming growth factor-β improved tissue strength, but reduced the contractile response. Transforming growth factor- β actually promoted a more contractile cell phenotype, but a stronger contractile force was required to overcome the thick compact collagen hydrogel and elicit a measurable contraction. This work adds to what is known about collagen-based tissue engineered vascular medias by identifying means of improving not only strength but vasoactivity. The trade-offs found between these two important characteristics are relevant to all tissue engineered medias.

Response and stability of vessel rolling motion with strongly nonlinear softening stiffness will be studied in this dissertation using the methods of stochastic dynamical systems. As one of the most classic stability failure modes of vessel dynamics, large amplitude rolling motion in random beam waves has been studied in the past decades by many different research groups. Due to the strongly nonlinear softening stiffness and the stochastic excitation, there is still no general approach to predict the large amplitude rolling response and capsizing phenomena. We studied the rolling problem respectively using the shaping filter technique, stochastic averaging of the energy envelope and the stochastic Melnikov function. The shaping filter technique introduces some additional Gaussian filter variables to transform Gaussian white noise to colored noise in order to satisfy the Markov properties. In addition, we developed an automatic cumulant neglect tool to predict the response of the high dimensional dynamical system with higher order neglect. However, if the system has any jump phenomena, the cumulant neglect method may fail to predict the true response. The stochastic averaging of the energy envelope and the Melnikov function both have been applied to the rolling problem before, it is our first attempt to apply both approaches to the same vessel and compare their efficiency and capability. The inverse of the mean first passage time based on Markov theory and rate of phase space flux based on the stochastic Melnikov function are defined as two different, but analogous capsizing criteria. The effects of linear and nonlinear damping and wave characteristic frequency are studied to compare these two criteria. Further investigation of the relationship between the Markov and Melnikov based method is needed to explain the difference and similarity between the two capsizing criteria.

The economic behavior of Hawaii's longline fishers was analyzed using a cross-sectional and time-series dataset from 1991 to 1998. Three empirical essays were written analyzing (1) the technological and economic interrelationships in the longline fishery, (2) trip choice behavior, and (3) vessel entry, stay, and exit decisions of the longline fishers. Studies on the analysis of technical-economic interrelationships among species suggest that Hawaii's longline fishery is characterized by a joint production process. Substantial economic and technical interactions existed, as many of the cross-price elasticities were significant, indicating either complementary or substitution relations in production among species. There was insufficient evidence for rejecting the null hypothesis of input-output separability. Output supplies were independent of their own prices. Output elasticities to effort and stock levels were positive and significant. Fishers' trip (or fishery) choice behavior was examined by applying the utility theoretic mixed model. Fishers exhibited utility maximizing behavior by choosing the trip type that yields best return, but they appeared to be risk-averse by choosing trip alternatives with less varying return, ceteris paribus. They exhibited "inertia" in switching to an alternative trip. Stock abundance indices of major species significantly influenced the type of trip chosen. Older and smaller vessels were more likely to choose the tuna trip rather than the swordfish or the mixed trip. Finally, the vessel entry-stay-exit decision was analyzed by applying the multinomial logit (unordered) model. The probability of a vessel to stay (or exit) in the fishery increased (or decreased) for an increase in the annual earning potential of a fisher. The fleet congestion level had a significant impact on the vessel entry-stay-exit decision. Vessels were reluctant to enter to and willing to exit from the fishery for an increase in fleet size. Entry-stay-exit decision was also based on a perceived abundance in major species stock levels. A vessel was more likely to stay in the fishery when the vessel owner was a Hawaii resident or a vessel captain. Vessel age had little impact on the entry-stay-exit decision. Simulation of probabilities for both forms of choices was carried out under different fleet structure and stock conditions.

A system for vessel characterization aimed at detecting deep vein thrombosis (DVT) in the lower limbs has been developed and evaluated using ultrasound image processing, location and force sensors measurements, blood flow information and a protocol based on the current clinical standard, compression ultrasound. The goal is to provide an objective and repeatable system to measure DVT in a rapid and standardized manner, as this has been suggested in the literature as an approach to improve overall detection of the disease. The system uses a spatial Kalman filter-based algorithm with an elliptical model in the measurement equation to detect vessel contours in transverse ultrasound images and estimate ellipse parameters, and temporal constant velocity Kalman filters for tracking vessel location in real-time. The vessel characterization also comprises building a 3-D vessel model and performing compression and blood flow assessments to calculate measures that indicate the possibility of DVT in a vessel. A user interface designed for assessing a vessel for DVT was also developed. The system and components were implemented and tested in simulations, laboratory settings, and clinical settings. Contour detection results are good, with mean and rms errors ranging from 1.47-3.64 and 3.69-9.67 pixels, respectively, in simulated and patient images, and parameter estimation errors of 5%. Experiments showed errors of 3-5 pixels for the tracking approaches. The measures for DVT were evaluated, independently and integrated in the system. The complete system was evaluated, with sensitivity of 67-100% and specificity of 50-89.5%. System learnability and memorability were evaluated in a separate user study, with good results. Contributions include a segmentation approach using a full parameter ellipse model in an extended Kalman filter, incorporating multiple measurements, an alternate sampling method for faster parameter convergence and application-specific initialization, and a tracking approach that includes a sub-sampled sum of absolutes similarity calculation and a method to detect vessel bifurcations using flow data. Further contributions include an integrated system for DVT detection that can combine ultrasound B-mode, colour flow and elastography images for vessel characterization, a system interface design focusing on usability that was evaluated with medical professionals, and system evaluations through multiple patient studies.

Thesis (doctoral)--Lund University, 1993. / Added t.p. with thesis statement inserted.

Thesis (Ph. D.)--University of Washington, 1999. / Vita. Includes bibliographical references (leaves 278-286).

Thesis (doctoral)--Lund University, 1993. / Added t.p. with thesis statement inserted.

Thesis (Ph. D.)--Chemical Engineering, Georgia Institute of Technology, 2006. / Chaikof, Elliot, Committee Chair ; Hanson, Stephen, Committee Member ; Lollar, John "Pete", Committee Member ; Sambanis, Athanassios, Committee Member ; Yoganathan, Ajit, Committee Member.

Thesis (Ph. D.)--Biomedical Engineering, Georgia Institute of Technology, 2006. / Pollman, Matthew, Committee Member ; Galis, Zorina, Committee Member ; McIntire, Larry, Committee Member ; Taylor, W Robert, Committee Member ; Jo, Hanjoong, Committee Member ; Nerem, Robert, Committee Chair.