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This research investigates materials for bone-joint failure repair using tribological and biomimicking approaches. The materials investigated represent three different repairing strategies. Refractory metals with and without treatment are candidates for total joint replacements due to their mechanical strength, high corrosion resistance and biocompatibility. A composite of biodegradable polytrimethylene carbonate, hydroxyl apatite, and nanotubes was investigated for application as a tissue engineering scaffold. Non-biodegradable polymer polyimide combined with various concentrations of nanotubes was investigated as a cartilage replacement material. A series of experimental approaches were used in this research. These include analysis of material surfaces and debris using high-resolution techniques and tribological experiments, as well as evaluation of nanomechanical properties. Specifically, the surface structure and wear mechanisms were investigated using a scanning electron microscope and an atomic force microscope. Debris morphology and structure was investigated using a transmission electron microscope. The debris composition was analyzed using an X-ray diffractometer. Nanoindentation was incorporated to investigate the surface nanomechanical properties. Polytrimythelene carbonate combined with hydroxyapatite and nanotubes exhibited a friction coefficient lower than UHMWPE. The nanoindentation response mimicked cartilage more closely than UHMWPE. A composite formed with PI and nanotubes showed a varying friction coefficient and varying nanoindentation response with variation in nanotube concentration. Low friction coefficients corresponded with low modulus values. A theory was proposed to explain this behavior based on surface interactions between nanotubes and between nanotubes and PI. A model was developed to simulate the modulus as a function of nanotube concentration. The boronized refractory metals exhibited brittleness and cracking. Higher friction coefficients were associated with the formation of amorphous debris. The friction coefficient for boronized Cr (~0.06) under simulated body fluid conditions was in the range found in natural joints.

This research investigates materials for bone-joint failure repair using tribological and biomimicking approaches. The materials investigated represent three different repairing strategies. Refractory metals with and without treatment are candidates for total joint replacements due to their mechanical strength, high corrosion resistance and biocompatibility. A composite of biodegradable polytrimethylene carbonate, hydroxyl apatite, and nanotubes was investigated for application as a tissue engineering scaffold. Non-biodegradable polymer polyimide combined with various concentrations of nanotubes was investigated as a cartilage replacement material. A series of experimental approaches were used in this research. These include analysis of material surfaces and debris using high-resolution techniques and tribological experiments, as well as evaluation of nanomechanical properties. Specifically, the surface structure and wear mechanisms were investigated using a scanning electron microscope and an atomic force microscope. Debris morphology and structure was investigated using a transmission electron microscope. The debris composition was analyzed using an X-ray diffractometer. Nanoindentation was incorporated to investigate the surface nanomechanical properties. Polytrimythelene carbonate combined with hydroxyapatite and nanotubes exhibited a friction coefficient lower than UHMWPE. The nanoindentation response mimicked cartilage more closely than UHMWPE. A composite formed with PI and nanotubes showed a varying friction coefficient and varying nanoindentation response with variation in nanotube concentration. Low friction coefficients corresponded with low modulus values. A theory was proposed to explain this behavior based on surface interactions between nanotubes and between nanotubes and PI. A model was developed to simulate the modulus as a function of nanotube concentration. The boronized refractory metals exhibited brittleness and cracking. Higher friction coefficients were associated with the formation of amorphous debris. The friction coefficient for boronized Cr (~0.06) under simulated body fluid conditions was in the range found in natural joints.

No description available.

Biology is a good source of analogies for engineering design. One approach of retrieving biological analogies is to perform keyword searches on natural-language sources such as books, journals, etc. A challenge in retrieving information from natural-language sources is the potential requirement to process a large number of search results. This thesis describes two methods on improving the relevancy of the search results. The first method is inserting metadata such as part- of-speech, word sense and lexicographical data for each word in a natural-language. The second method is categorizing the search results, using WordNet relationships and Wikipedia structures as ontologies. Although this research is still exploratory, initial qualitative observations demonstrate successful identification and separation of biological phenomena relevant to either desired functions or desired qualities. The benefits of embedding metadata are demonstrated through a case study on the redesign of a fuel cell bipolar plate. A prototype was constructed with ability to passively prevent prolonged catastrophic flooding.

Biology is a good source of analogies for engineering design. One approach of retrieving biological analogies is to perform keyword searches on natural-language sources such as books, journals, etc. A challenge in retrieving information from natural-language sources is the potential requirement to process a large number of search results. This thesis describes two methods on improving the relevancy of the search results. The first method is inserting metadata such as part- of-speech, word sense and lexicographical data for each word in a natural-language. The second method is categorizing the search results, using WordNet relationships and Wikipedia structures as ontologies. Although this research is still exploratory, initial qualitative observations demonstrate successful identification and separation of biological phenomena relevant to either desired functions or desired qualities. The benefits of embedding metadata are demonstrated through a case study on the redesign of a fuel cell bipolar plate. A prototype was constructed with ability to passively prevent prolonged catastrophic flooding.

The treble clef binding motif of the zinc finger metalloprotein utilizes N2S2 binding sites. Whereas other N2S2 metalloproteins function in catalytic roles, zinc fingers serve mostly a structural element, although there has been some evidence that the zinc finger protein can interact with exogenous metal ions in aggregate formation or ion exchange. The work presented within has been aimed at precedents for both of the latter in Zn2+. The use of zinc and cadmium dithiolate complexes as mono- and bidentate S-donor ligands to tungsten carbonyl complexes was explored and the ability of zinc and cadmium complexes to stably bind to W(CO)x (x = 4 and 5) was established. The reactivity of thiolate sulfurs within the bimetallic complexes was examined, gaining an understanding of zinc and cadmium N2S2. The characteristics of these complexes were examined via IR, UV-vis, elemental analysis, and x-ray crystallography spectroscopy. The ability of zinc to act as a scaffold for the synthesis of bisacetylbme-dach in the production and subsequent transfer of the same ligand to exogenous metal ion sources was investigated. Cu2+ and Cd2+ analogs to the Zn-1’-Ac2 were synthesized and their properties investigated with IR, elemental analysis, and UV-vis spectroscopy.

The work described in this dissertation details the development of a biomimetic materials for use in sensors and therapeutics, based on new advances in material science. The sensors developed herein target neurodegenerative diseases. Two of the diseases, the transmissible spongiform encephalopathies (TSEs) and Alzheimer’s disease (AD), are diseases associated with the abnormal folding of a protein, thus detecting the disease is dependent upon developing structure specific sensor technologies. Both sensors developed in this work take advantage of the unique optical properties associated with nanoscale metal particles, however they use different types of spectroscopies for optical detection of the presence of the disease associated abnormal protein, and different types of recognition elements that bring the disease associated proteins close to the nanoscale metal particles. In the case of TSEs, the recognition element was a commercially available antibody. In the case of AD, the recognition element was a molecular scale self-assembled surface. A therapeutic for AD was developed based on the molecular scale materials developed for the AD biosensor. Mathematical models were developed that facilitated the rational design of the biosensors described in this work that could also be used in future biosensor development.

Thesis (Ph.D)--Biomedical Engineering, Georgia Institute of Technology, 2010. / Committee Chair: Andres Garcia; Committee Member: Andrew Lyon; Committee Member: Barbara Boyan; Committee Member: Johnna Temenoff; Committee Member: Todd McDevitt. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Pas de résumé en français / Recent studies have suggested that minimal actomyosin systems have the intrinsic property to oscillate whensubjected to an elastic load. A similar situation can be found in various biological systems, leading, both in-vivoand in-vitro, to spontaneous oscillations. In particular, muscular systems as well as mechanosensitive hair-cellbundles in the inner ear have been shown to oscillate spontaneously as the result of active force production by anacto-myosin protein complex. We attempt to shed light on the mechanism behind the oscillatory activity of theacto-myosin system, in particular by determining the parameters that control the frequency and amplitude ofoscillation. The stiffness of the system, the total force developed by the motors and the type of motors have beenproposed as being influential in this respect. To investigate this effect, we make use of a modified motility assayconsisting of a motor-driven stiff polarized actin bundle subjected to an elastic load provided by opticaltweezers. During the course of this work, we also characterized auto-assembled magnetic bead columns andassessed their viability as molecular force sensors to study the oscillations. The fact that they can easily beorganized into large arrays makes them interesting as potential ‘high-throughput’ force sensors