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- Creators: Arizona State University
Description
The past two decades have been monumental in the advancement of microchips designed for a diverse range of medical applications and bio-analysis. Owing to the remarkable progress in micro-fabrication technology, complex chemical and electro-mechanical features can now be integrated into chip-scale devices for use in biosensing and physiological measurements. Some of these devices have made enormous contributions in the study of complex biochemical processes occurring at the molecular and cellular levels while others overcame the challenges of replicating various functions of human organs as implant systems. This thesis presents test data and analysis of two such systems. First, an ISFET based pH sensor is characterized for its performance in a continuous pH monitoring application. Many of the basic properties of ISFETs including I-V characteristics, pH sensitivity and more importantly, its long term drift behavior have been investigated. A new theory based on frequent switching of electric field across the gate oxide to decrease the rate of current drift has been successfully implemented with the help of an automated data acquisition and switching system. The system was further tested for a range of duty cycles in order to accurately determine the minimum length of time required to fully reset the drift. Second, a microfluidic based vestibular implant system was tested for its underlying characteristics as a light sensor. A computer controlled tilt platform was then implemented to further test its sensitivity to inclinations and thus it‟s more important role as a tilt sensor. The sensor operates through means of optoelectronics and relies on the signals generated from photodiode arrays as a result of light being incident on them. ISFET results show a significant drop in the overall drift and good linear characteristics. The drift was seen to reset at less than an hour. The photodiodes show ideal I-V comparison between photoconductive and photovoltaic modes of operation with maximum responsivity at 400nm and a shunt resistance of 394 MΩ. Additionally, post-processing of the tilt sensor to incorporate the sensing fluids is outlined. Based on several test and fabrication results, a possible method of sealing the open cavity of the chip using a UV curable epoxy has been discussed.
ContributorsMamun, Samiha (Author) / Christen, Jennifer Blain (Thesis advisor) / Goryll, Michael (Committee member) / Yu, Hongyu (Committee member) / Arizona State University (Publisher)
Created2011
Description
There is a considerable amount of research stating that vegetarian diets have an alkalizing effect while the typical western diet is acid-forming. There is substantial evidence regarding the health benefits of an alkaline diet. Although vegetarian diets demonstrate the ability to foster these health benefits, many people are still not willing to adopt a completely vegetarian diet. PURPOSE: To evaluate the effect of following a vegan diet two or three days per week on acid-base balance in a healthy college student population aged 18-30. METHODS: In a one-week interventional design, 23 people were randomly assigned to follow a vegan diet 2 days per week (VEG2;n=7), 3 days per week(VEG3;n=8), or 7 days per week (VEG7;n=8). Urine pH and dietary PRAL were assessed in each group at baseline and after the one-week intervention. RESULTS: There was no significant difference in urinary pH between the three groups (p=0.12). The change in PRAL values after the dietary intervention was different between the 3 groups (p=0.03). CONCLUSION: Adherence to a vegan diet 2 or 3 days per week did not show a significant change in urinary pH or PRAL.
ContributorsCosgrove, Kelly (Author) / Johnston, Carol (Thesis advisor) / Sweazea, Karen (Committee member) / Mayol-Kreiser, Sandra (Committee member) / Arizona State University (Publisher)
Created2015