Browsing by Author "Wendy E. Krause, Committee Co-Chair"

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    Develop a More Biodegradable/Biocompatible Hemostatic Fabric for Treatment of Bleeding Wounds
    (2009-07-20) Ina, Maria; Elizabeth G. Loboa, Committee Member; Samuel M. Hudson, Committee Chair; Wendy E. Krause, Committee Co-Chair; Xiangwu Zhang, Committee Member
    Hemostatic wound dressings help control traumatic external bleeding by enhancing or accelerating the natural clotting process through various physical reactions. Since the fatal traumatic hemorrhage remains one of the most challenging problems for both military and civilian medicine, efficient hemostatic wound dressings have been in high demand. Currently, several hemostatic dressings have been commercially available for acute hemorrhage, however, they still have some limitations in terms of cytotoxicity, biodegradability, sterilization, and cost performance. Thus, the development of effective biocompatible hemostatic dressings that overcome these limitations has been needed. The goal of this study is to investigate the potential application of Bombyx mori silk fibroin fibers as hemostatic wound dressings. First, the silk fibers were treated with two kinds of neutral salt [calcium nitrate tetra-hydrate (Ca(NO3)2 4H2O) and calcium chloride (CaCl2) ] / alcohol [methanol and ethanol] systems in order to decrystallize theirβ-sheet crystalline structure and improve the water absorbability and biodegradability. The decrystallization was carried out by controlling the solvent concentration and environment temperature. FTIR and X-ray demonstrated that most effective decrystallization of silk fibers were performed with the treatment in 50% (w/w) Ca(NO3)2 4H2O/methanol at 65℃, accompanying obvious decrease in the crystal size. Next, the blood clotting ability of the treated silk fibers was investigated by blood coagulation test. Even though any evident blood clot formation on the silk fibers was not confirmed during the test, the blood was separated into two phases and erythrocyte sedimentation was observed at different rate for each specimen. The silk fibers treated with most severe condition caused slower erythrocyte sedimentation compared with the non-treated silk fibers, suggesting less blood coagulation ability. Previously it has been reported that surface of silk fibroin fibers is hydrophobic and blood proteins interact with the silk fibroin through strong hydrophobic interaction. The obtained results suggest us that the decrease in hydrophobicity of the silk fibers surface due to decrystallization resulted in less interaction with blood proteins. Based on this result, we modified the silk fibers with sodium dodecyl sulfate (SDS) to give hydrophobic portion on the silk fiber surface. The difference in blood coagulation behavior between SDS-modified fibers and non-modified fibers was compared.
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    Platinum and Platinum Alloy-Carbon Nanofiber Composites for Use as Electrodes in Direct Methanol Fuel Cells
    (2010-04-20) Lin, Zhan; Xiangwu Zhang, Committee Chair; Wendy E. Krause, Committee Co-Chair; Saad A. Khan, Committee Member; Samuel M. Hudson, Committee Member
    In response to the energy needs of modern society and emerging ecological concerns, the pursuit of novel, low-cost, and environmentally friendly energy conversion and storage systems has raised significant interest. Among various energy conversion and storage systems, fuel cells have become a primary research focus since they convert chemical energy directly into electrical energy with high efficiency and low pollutant emissions. For example, direct methanol fuel cells (DMFCs), which supply the electrical energy by converting methanol to energy, are an ideal fuel cell system for applications in electric vehicles and electronic portable devices due to their relatively quick start-up, rapid response to catalyst loading, and low operating temperature. However, the wide commercial use of DMFCs in advanced hybrid electric vehicles and electronic portable devices is hampered by their high cost, poor durability, and relatively low energy and power densities. In order to address these problems, their research focuses on the development of highly active electrode catalysts coupled with a suitable electrode structure for the oxidation of methanol at the anode and the reduction of oxygen at the cathode to attain high efficiency of DMFCs, and subsequently lowering the cost. In this dissertation, the fabrication of novel platinum and platinum alloy nanoparticle-loaded carbon nanofibers (CNFs) for use as electrodes in DMFCs is demonstrated through electrospinning, carbonization, and deposition. The resulting CNF-based electrodes possess the properties of high electroactive surface area, good catalytic abilities towards the oxidation of methanol and the reduction of oxygen, and great long-time stability. As a result, DMFCs using these CNFs-supported platinum and platinum alloy nanoparticles as electrodes offer many advantages, such as improved electrocatalytic abilities, long-term stability, easy fabrication, low cost, and environmental benignity. Therefore, this new technology opens up new opportunities to develop high-performance electrode materials in the future for high-performance DMFCs, which are one of the promising power sources for consumer devices and electric vehicles, and play a critical role in solving the worldwide critical energy issue.