Engineering Commons^™

Lateral-Mode Vibration Of Microcantilever-Based Sensors In Viscous Fluids Using Timoshenko Beam Theory, Joshua Schultz

Dissertations (1934 -)

Dynamic-mode microcantilever-based devices are well suited to biological and chemical sensing applications. However, these applications often necessitate liquid-phase sensing, introducing significant fluid-induced dissipative forces and reducing device quality factors (Q). Recent experimental and analytical research has shown that higher in- fluidQis achieved by exciting microcantilevers in the lateral flexural mode. However, the experimental results show that, for microcantilevers having larger width-to-length (b/L) ratios, the behaviors predicted by current analytical models differ from measurements.

To more accurately model microcantilever resonant behavior in viscous fluids and to improve understanding of lateral-mode sensor performance, a new analytical model is developed, incorporating both viscous …

Functional Integration In The Cortical Neuronal Network Of Conscious And Anesthetized Animals, Jeannette A. Vizuete

Dissertations (1934 -)

General anesthesia consists of amnesia, analgesia, areflexia and unconsciousness. How anesthetics suppress consciousness has been a mystery for more than one and a half centuries.

The overall goal of my research has been to determine the neural correlates of anesthetic-induced loss of consciousness. I hypothesized that anesthetics induce unconsciousness by interfering with the functional connectivity of neuronal networks of the brain and consequently, reducing the brain's capacity for information processing. To test this hypothesis, I performed experiments in which neuronal spiking activity was measured with chronically implanted microelectrode arrays in the visual cortex of freely-moving rats during wakefulness and at …

Pedaling-Related Brain Activation In People Post-Stroke: An Fmri Study, Nutta-On Promjunyakul

Dissertations (1934 -)

This study aimed to enhance our understanding of supraspinal control of locomotion in stroke survivors and its relationship to locomotor impairment. We focused mainly on the locomotor component of walking, which involves rhythmic, reciprocal, flexion and extension movements of multiple joints in both legs. Functional magnetic resonance imaging (fMRI) was used to record human brain activity while pedaling was used as a model of locomotion. First, we examined the spatiotemporal characteristics of hemodynamic responses recorded with fMRI and found that they were different in stroke survivors and control subjects. However, these differences were not substantial enough to require altering the …

Finite-Time Control And Estimation Of Nonlinear Systems With Disturbance Attenuation, Mohammad N. Elbsat

Dissertations (1934 -)

This dissertation addresses the mixed criteria finite-time bounded controller and observer design of certain classes of nonlinear systems. Finite-time bounded controllers and observers are used to guarantee performance bounds on the transient response of the systems considered. A robust and resilient mixed criteria state-feedback controller design is developed for a class of nonlinear systems with conic-type nonlinearities lying within a hypersphere of uncertain center, additive disturbances, and controller gain perturbations in discrete and continuous-time. Furthermore, a robust and resilient mixed criteria state-dependent state-feedback controller design is developed for a class of nonlinear systems with state dependent system matrices and state-dependent …

Preservation Of Methanogenic Cultures To Enhance Anaerobic Digestion, Ujwal H. Bhattad

Dissertations (1934 -)

The use of anaerobic biotechnology is increasing as a sustainable process to treat various organic wastes. Methanogens convert organic COD into CH4 and play the key role to drive thermodynamically unfavorable biochemical fermentation reactions and keep the digestion process steady and efficient. Progressive understanding of anaerobic microbiology with digester functionality may help to develop efficient, customized methanogenic cultures to enhance anaerobic bioprocesses. Preservation of methanogenic cultures via drying would be a cost-effective option for research and practical applications. However, preservation of methanogenic cultures is challenging due to methanogen sensitivity to O2 toxicity and drying, and very limited work is reported …

Quantitative Biomechanical Evaluation Of Upper Extremity: Strain Behavior Of The Humerus Diaphysis Under Loading, Prateek Grover

Dissertations (1934 -)

While mechanical behavior of the adult human lower extremity long bones under loading has been studied extensively, the same is not true for the adult human humerus. Mechanical data reported for cadaveric humeri and anatomic humerus models are limited to stiffness and rigidity. Strain characteristics of the humerus diaphysis as a function of loading provide a valuable addition to the currently limited knowledge. The objective of this dissertation was to accomplish this goal, using numerical/finite element (FE) methods applied to a standard anatomic humerus model (Reference-Humerus) that was developed from the NIH Visible Human Project for this purpose. Four phases …

Relating Methanogen Community Structure And Function In Anaerobic Digesters, Benjamin T.W. Bocher

Dissertations (1934 -)

A deeper understanding of how microbial community structure relates to process function would help improve anaerobic digester design. This dissertation describes both qualitative and quantitative relationships between anaerobic digester function and microbial community structure. Community structure was characterized using banding pattern intensities from denaturing gradient gel electrophoresis (DGGE) for the mcrA gene of methanogenic Archaea. The first project compared a single-stage continuously mixed stirred tank reactor (CSTR) and staging with an acidogenic CSTR followed by a methanogenic CSTR. After seeding with the same biomass, these unique process configurations exhibited different function and qualitatively different methanogen communities. Compared to a single-stage …

Integration Of Eeg-Fmri In An Auditory Oddball Paradigm Using Joint Independent Component Analysis, Jain Mangalathu Arumana

Dissertations (1934 -)

The integration of event-related potential (ERP) and functional magnetic resonance imaging (fMRI) can contribute to characterizing neural networks with high temporal and spatial resolution. The overall objective of this dissertation is to determine the sensitivity and limitations of joint independent component analysis (jICA) within-subject for integration of ERP and fMRI data collected simultaneously in a parametric auditory oddball paradigm. The main experimental finding in this work is that jICA revealed significantly stronger and more extensive activity in brain regions associated with the auditory P300 ERP than a P300 linear regression analysis, both at the group level and within-subject. The results …

Anaerobic Co-Digestion For Enhanced Renewable Energy And Green House Gas Emission Reduction, Navaneethan Navaratnam

Dissertations (1934 -)

The need to develop renewable energy is important for replacing fossil fuel, which is limited in quantity and also tends to increase in price over time. The addition of high strength organic wastes in municipal anaerobic digesters is growing and tends to increase renewable energy production. In addition, conversion of wastes to energy significantly reduces uncontrolled greenhouse gas emissions. Co-digestion of municipal sludge with any combination of wastes can result in synergistic, antagonistic or neutral outcomes. The objectives of this study were to identify potential co-digestates, determine synergistic, antagonistic and neutral effects, determine economic benefits, quantify performance of bench scale …

Quantifying The Impact Of Altered Hemodynamics And Vascular Biomechanics To Changes In Structure And Function In Native And Corrected Aortic Coarctation, Arjun Menon

Dissertations (1934 -)

Coarctation of the aorta (CoA) is associated with substantial cardiovascular morbidities despite successful treatment through surgical or catheter-based intervention. Although specific mechanisms leading to these morbidities remain elusive, abnormal hemodynamics and vascular biomechanics are implicated. We used a novel animal model that facilitates quantification of CoA-induced hemodynamic and vascular biomechanics alterations and their impact on vascular structure and function, independent of genetic or confounding factors. Rabbits underwent thoracic CoA at 10 weeks of age (~9 human years) to induce a 20 mmHg blood pressure (BP) gradient using permanent or dissolvable suture thereby replicating untreated and corrected CoA. Computational fluid dynamics …