Dissertation (Ph.D.)--University of Toledo, 2005. / Typescript. "A dissertation [submitted] as partial fulfillment of the requirements of the Doctor of Philosophy degree in Engineering." Bibliography: leaves 106-120.

published_or_final_version / abstract / Electrical and Electronic Engineering / Master / Master of Philosophy

Thesis (M. Phil.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

Thesis (M. Phil.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

abstract: Neurostimulation methods currently include deep brain stimulation (DBS), optogenetic, transcranial direct-current stimulation (tDCS), and transcranial magnetic stimulation (TMS). TMS and tDCS are noninvasive techniques whereas DBS and optogenetic require surgical implantation of electrodes or light emitting devices. All approaches, except for optogenetic, have been implemented in clinical settings because they have demonstrated therapeutic utility and clinical efficacy for neurological and psychiatric disorders. When applied for therapeutic applications, these techniques suffer from limitations that hinder the progression of its intended use to treat compromised brain function. DBS requires an invasive surgical procedure that surfaces complications from infection, longevity of electrical components, and immune responses to foreign materials. Both TMS and tDCS circumvent the problems seen with DBS as they are noninvasive procedures, but they fail to produce the spatial resolution required to target specific brain structures. Realizing these restrictions, we sought out to use ultrasound as a neurostimulation modality. Ultrasound is capable of achieving greater resolution than TMS and tDCS, as we have demonstrated a ~2mm lateral resolution, which can be delivered noninvasively. These characteristics place ultrasound superior to current neurostimulation methods. For these reasons, this dissertation provides a developed protocol to use transcranial pulsed ultrasound (TPU) as a neurostimulation technique. These investigations implement electrophysiological, optophysiological, immunohistological, and behavioral methods to elucidate the effects of ultrasound on the central nervous system and raise questions about the functional consequences. Intriguingly, we showed that TPU was also capable of stimulating intact sub-cortical circuits in the anesthetized mouse. These data reveal that TPU can evoke synchronous oscillations in the hippocampus in addition to increasing expression of brain-derived neurotrophic factor (BDNF). Considering these observations, and the ability to noninvasively stimulate neuronal activity on a mesoscale resolution, reveals a potential avenue to be effective in clinical settings where current brain stimulation techniques have shown to be beneficial. Thus, the results explained by this dissertation help to pronounce the significance for these protocols to gain translational recognition. / Dissertation/Thesis / Ph.D. Biology 2011

published_or_final_version / abstract / Diagnostic Radiology / Master / Master of Philosophy

Neutron radiography is well suited to non-invasive imaging of water within metal containers. The goal of this work is to determine if neutron radiography can be used to image water freezing within a 1.6mm diameter capillary tube with the ultimate goal of observing this phenomena within fuel cells. In this work, radiography was completed at the Thermal Neutron Imaging Facility in the Nuclear Engineering Teaching Lab at The University of Texas at Austin. The source of neutrons was a TRIGA Mark II nuclear research reactor capable of 1.1 MW steady state power, which creates a neutron flux at the neutron imaging plane in beam port 5 of 5×10^6 neutrons/cm^2s. A scintillation screen and CCD camera are utilized to obtain digital radiographs, in which differences in pixel intensity are related to differences in neutron attenuation. An image processing algorithm was developed in Matlab to extract necessary data from each image, analyze water column images, and compare one to another. Also, a neutron flux model was implemented in Matlab in order to understand how a non-unidirectional neutron flux will affect final results. Raw image intensities of the water column in liquid and solid form were found to differ from expectations by at most 12.0% and 13.3%, respectively from the predictions of the Matlab flux model. A difference in pixel intensity comparing liquid water to solid water data is apparent and quantified. A ratio of pixel intensity for the ice image to the water image at full thickness of the water column is expected to be 1.038. Experimental results find a maximum ratio of 1.027, 1.1% off from expectations. / text

Near infrared (NIR) spectroscopy is being developed on living tissue models for noninvasively measuring in vivo glucose concentrations in individuals with diabetes. Multivariate calibration models have been built and the selectivity of each multivariate signature has been evaluated by several means. The primary objective of the research detailed in this dissertation is to practically apply noninvasive NIR glucose measurements on animal models for both short-term and long-term studies and preview future human subject evaluations. In the animal study, living tissue spectra were collected through a modified optical interface with hyper- and hypo-glycemia control. Selective measurements of glucose molecules are illustrated by the partial lease squares (PLS) algorithm, net analyte signal (NAS) vector, and hybrid linear analysis (HLA). Each model demonstrates the ability to predict prospective glucose concentrations in the short term. A restraint platform was developed for the long-term study on conscious animals. Conscious animal spectra were collected on multiple days. The anesthetized animal experiment follows on the final day. Principal component analysis (PCA) of spectra collected on different days demonstrates no significant difference between conscious animal spectra and anesthetized animal spectra. Moreover, an NAS vector analysis from conscious animal spectra has the ability predict glucose concentrations which follow the blood glucose transient during the anesthetized animal experiment. This procedure has great potential to be applied in future NIR glucose monitoring device. Before the application of this noninvasive NIR technology on people with diabetes, the impact of skin difference must be determined. In this human subject study, human skin color and baseline spectra were collected and analyzed to determine differences among individuals and within groups of people. To compare in vivo NIR spectra with different skin characteristics, PCA was performed to obtain principal component (PC) scores. Poor correlation between PC scores and skin characteristics concludes that noninvasive near-infrared technology is insensitive to different types of skin. In addition, glucose prediction was performed by a NAS analysis. The prediction results demonstrate that it is feasible to build a NAS glucose model for noninvasive NIR glucose predictions in human subjects.

Thesis (M. Phil.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

In a continuing effort to develop a noninvasive means of monitoring glucose levels using the aqueous humor of the eye, a dual wavelength system has been developed in order to show that varying birefringence, similar to what is seen with a moving cornea, can be compensated. In this paper a dual wavelength, closed-loop, system was designed and a model was developed to extract the glucose concentration information. The system and model were tested using various concentrations of glucose in a birefringent test cell subject to motion artifact. The results show that for a static, non-moving sample, glucose can be predicted to within 10 mg/dl for the entire physiologic range (0-600mg/dl) for either laser wavelength (523nm or 635nm). In the presence of moving birefringence, each individual wavelength produced standard errors on the order of a few thousand mg/dL. However, when the two wavelengths are combined into the developed model, this error is less than 20mg/dL. The approach shows that multiple wavelengths can be used to drastically reduce the error in the presence of a moving birefringent sample. This research also shows promising preliminary results that the error is less than 25mg/dl in presence of a motion induced cornea birefringence artifact in NZW rabbits’ eyes.