Engineering Commons^™

Linking Obesity To Colorectal Cancer: Recent Insights Into Plausible Biological Mechanisms, Catherine Guffey

Theses and Dissertations

Obesity has emerged as a leading environmental risk factor for the development of CRC. However, the mechanisms underlying this relationship have not yet been fully explained. Recent literature has focused on 1) inflammatory processes, 2) adipokines, and 3) estrogen. Obesity-enhanced inflammation is largely orchestrated by increases in adipose tissue macrophages leading to the secretion of TNF-alpha, MCP-1, and IL-6, all of which are linked to CRC. Adiponectin is decreased with obesity and has been reported to be negatively associated with CRC, while leptin, which is increased, is positively associated with the disease. Estrogen has been shown to influence CRC, although …

Resveratrol Attenuates The Development Of Trans-Aortic Constriction (Tac) Induced Heart Failure In Mice, Prakash Kumar Gupta

Theses and Dissertations

Heart failure (HF) still remains the leading cause of morbidity and mortality and imposes severe global affliction and enormous cost on the healthcare system. Although current pharmacological therapies have shown to slow down the progression of HF, but seems to have reached their limits in improving overall patient prognosis. Thus, an immediate call for novel alternate therapies are needed which act independently as well as in conjunction with current treatment modality. Studies were performed in the well-established transverse aortic constriction (TAC) model of chronic pressure overload (PO) in mice. In the first series of studies, Male C57BL6 mice (26-28 g) …

Role Of Microrna-155 In A Mouse Model Of Colon Cancer., Claire Mitchell Midyette

Theses and Dissertations

Colorectal cancer remains the third most common malignancy and the fourth most common cause of cancer mortality worldwide. Dysregulated miRNA levels are associated with several types of malignancies and may serve as important biomarkers and/or therapeutic targets in colorectal cancer. We examined the role of miRNA-155 on tumorigenesis and associated symptoms using a well-characterized mouse model of colorectal cancer. C57BL/6 wild-type mice and miRNA-155-/- mice (n=7-13 group) were given a single injection of AOM (10mg/Kg) followed by 3 cycles of DSS (2% in the water for 1 week followed by 2 weeks of plain water). A C57BL/6 wild-type group that …

High Fat Diet Induced Obesity In A Mouse Model For Colorectal Cancer, Kennerly Clinton Patrick

Theses and Dissertations

Obesity is widely correlated with the incidence of colorectal cancer (CRC). The exact mechanisms that link obesity to CRC risk have not yet been fully established, and only a limited number of animal models are available to study pathways involved in obesity-related colon carcinogenesis. The objective of this study was to determine the influence of HFD-induced obesity on AOM/DSS-mediated colorectal tumorigenesis, tumor proliferation, and symptom severity. Male C57BL/6 mice were fed a novel high fat diet, designed to mimic the standard American diet (12 % saturated fat & 28 % unsaturated fat), at 4 weeks of age until 16 weeks …

Design And Analysis Of An Electronically Steerable Microstrip Patch And A Novel Coplanar Waveguide (Cpw) Fed Slot Antenna Array, Hamad Shaban Aldossary

Theses and Dissertations

Conformal Phased Array Antennas (CPAAs) are very attractive for their high gain, low profile, and beam scanning ability while being conformal to their mounting surface. Among them are microstrip patch phased arrays and wideband slot phased arrays which are of particular significance.

In this work, first the study, design, and implementation of a conformal microstrip patch phased array is presented which consists of a high gain beam scanning array implemented using microstrip delay lines controlled using GaAs SPDT switches. Then the study and design of a wideband Coplanar Waveguide (CPW)-fed slot phased array antenna is presented. In both cases the …

Coordinated Control Of Power Electronic Converters In An Autonomous Microgrid, Gholamreza Dehnavi

Theses and Dissertations

Advances in power electronics and generation technologies have increased the viability of distributed generation systems. A microgrid is a special category of distributed generation systems that is distinguished by its size and the ability to operate independently as an islanded system. As long as a microgrid is connected to a large grid, quality of the voltage is supported by the main grid and each power source connected to the microgrid generates independently. In contrast, in the islanded operation of microgrids and in electrical islands such as shipboard distribution systems, dynamics are strongly dependent on the connected sources and on the …

Osteon-Mimetic Nanocomposite Materials For Bone Regeneration, Ozan Karaman

Theses and Dissertations

The limitations of large bone defect regeneration has brought the focus of Bone Tissue Engineering research on fabricating three-dimensional bone-mimetic grafts that could enhance osteogenesis and vascularization. Osteons composed of apatite-deposited aligned collagen nanofiber layers are the fundamental building blocks of cortical bone. In natural cortical bone, mineralization is mediated by extracellular matrix (ECM) proteins with amino acid sequences rich in glutamic acid. This dissertation is focused on the establishment of a novel biomimetic approach to engineer scaffolds for healing large bone defects.

In the first part, we investigated the effect of calcium phosphate (CaP) deposition on aligned surface-modified nanofibers …

Microencapsulation Of A Connexin-43 Mimetic Peptide As A Novel Wound Healing Agent In An Ocular Injury Model, Keith Brian Moore

Theses and Dissertations

Corneal transplantation and related surgical procedures are areas of tissue replacement which have seen promising advances. Currently, cornea transplants are one of the most common surgical procedures, with approximately 40,000 occurring each year in the United States. Still, problems exist with a 20% rejection rate, post surgical infections, and the need for a constant supply of donors. The ability to safely and quickly heal and regenerate corneal epithelia fills an area of advancement in regenerative medicine, with implications reaching beyond the scope of vision therapies toward healing of a wide range of tissues and wounds. In vivo corneal wounds were …

Effect Of Physiological Oxygen Levels On Osteogenic Differentiation Of Adipose-Derived Stem Cells, Suchit Sahai

Theses and Dissertations

Regenerative medicine presents exciting strategies for healing critical-size bone defects through the implantation of cells and biocompatible scaffolds. Most in vitro studies are performed in atmospheric oxygen conditions (~20%), which do not accurately mimic the CSD microenvironment. Due to damage to the vasculature at CSDs, oxygen levels fall into the hypoxic range (<5%), which can impact viability, proliferation and differentiation of the cells employed for bone regeneration. Understanding the cellular responses to hypoxia has grown primarily from study of individual molecular factors. The master regulator of adaptive responses to low oxygen availability is the nuclear factor, hypoxia-inducible factor-1. HIF-1 is a heterodimeric protein, stable below 6% O2 condition in the nucleus and has been shown to play a role in angiogenic-osteogenic coupling. We have developed a responsive, fluorescent, hypoxia detection system and determined whether HIF activity can be tracked in both 2-D and 3-D cultures. Adipose-derived stem cells (ASCs) were selected due to their broad utilization in tissue engineering strategies and characterized the influence of HIF signaling on its phenotype. The work done identified that of hypoxia impaired osteogenic differentiation of ASCs in both 2-D and 3-D cultures and HIF-1 did not mediate this effect. Ischemic preconditioning (IPC) strategy and varied protocols used represents a clinically feasible manipulation of cell preparation to help the survival of implanted ASCs and accelerate osteogenic differentiation at physiological oxygen levels.

Characterizing Hypoxia And Its Behavioral Effects In 3-Dimensional Cell Aggregates, Matthew Lorincz Skiles

Theses and Dissertations

Cell transplantation can be considered a regenerative therapy, an intervention which attempts to replace or restore the function of compromised tissue by harnessing innate properties of cells that cannot be replicated artificially. For such therapies to succeed, it will be necessary to understand and closely match the physiological conditions that govern cell behaviors in vivo. One important factor is low oxygen tension, termed hypoxia, which is often overlooked in vitro. Because oxygen insufficiency can lead to cell death, hypoxia has traditionally been viewed as a negative condition. However, hypoxia can also serve as a potent regulator of crucial cell behaviors …

An Analysis Of Constructive Network Formation Models, Gary Fredericks

Theses and Dissertations

We study a family of network formation models to determine how payment rules affect the final network topologies that emerge. In our model a set of nodes starts out without any edges and the nodes must pay for the creation of edges using one of several different payment mechanisms. Example payment mechanisms include one node paying for the whole edge, and the cost being shared equally between the two nodes. We show how the set of networks formed by some payment rules are subsets of those formed by other rules. We also perform extensive empirical tests on networks of up …

Modeling Of Sic Power Semiconductor Devices For Switching Converter Applications, Ruiyun Fu

Theses and Dissertations

Thanks to recent progress in SiC technology, SiC JFETs, MOSFETs and Schottky diodes are now commercially available from several manufactories such as Cree, GeneSiC and Infineon. SiC devices hold the promise of faster switching speed compared to Si devices, which can lead to superior converter performance, because the converter can operate at higher switching frequencies with acceptable switching losses, so that passive filter size is reduced. However, the ultimate achievable switching speed is determined not only by internal semiconductor device physics, but also by circuit parasitic elements. Therefore, in order to accurately predict switching losses and actual switching waveforms, including …

Passive Equalizer Topology Analysis For Signal Integrity Applications, Kuo-Lun Yen

Theses and Dissertations

In high-speed, high density PCB bus systems, high frequency signal losses and crosstalk can have great impacts on signal integrity and digital timing, which can distort transmitted signals, worsen eye diagrams, and attenuate signal amplitudes. Also, these impacts make digital signals and their energy smearing over multiple bit positions as known as jitters, and cause the phenomenon of inter-symbol interference (ISI) in digital signal transmissions.

The main objective of this thesis is to analyze and develop efficient topology circuits for compensating bus system high frequency losses by using equalization techniques. The thesis has focused on study of various practical and …

Efficient Generation Of Power In Medium Voltage Direct Current Systems: Variable Speed Operation And Rectifier Considerations, Dan Li

Theses and Dissertations

By investigating variable speed operation of an engine and different types of ac-dc rectifier topologies, this dissertation provides procedures to develop and implement efficient Medium Voltage Direct Current (MVDC) power systems. The research reported here offered solutions to the following issues:

1) Efficiency improvement of a gas turbine by running it in variable speed operation mode.

2) The advantages and disadvantages of different ac-dc rectifier topologies considering both the efficiency and rectifier performance (dc bus voltage regulation, weight/size/volume of passive components, number of semi-conductor devices, displacement power factor, complexity of control strategy, etc.)

3) Implementation of variable speed MVDC power …

Fabrication And Characterization Of Compact High Resolution Radiation Detectors Based On 4h-Sic N-Type Epilayer And Cdznte, Kelvin Juvenal Zavalla Mendoza

Theses and Dissertations

The need of room-temperature, compact, and high resolution radiation detectors has opened the path for the development of new materials with suitable properties. Silicon carbide (SiC) and CdZnTe (CZT) are semiconductor materials with wide band gap that can operate efficiently at room temperatures (RT) and above. CZT has a high average atomic number (Z) which offers a high photoelectric absorption coefficient for x-/gamma rays. SiC allows high energy heavy ion detection due to its high radiation hardness even at temperatures much higher than room temperatures (RT). This thesis focuses on the fabrication and characterization of semiconductor based radiation detectors for …

Optimal Design And Control Of Dc-Dc Resonant Converters For Wireless Power Transfer Applications, Isaac Nam

Theses and Dissertations

Wireless power transfer (WPT) technology provides galvanic isolation for improved safety and also provides reliability by eliminating the need for dedicated connectors/adapters that can get damaged due to frequent usage. For these reasons, it has become popular in medical implant charging and electric vehicle (EV) charging. Beyond these niche applications, due to aesthetic features and convenience provided by the cord-free environment, it is rapidly becoming an attractive charging solution for various portable electronics as well as household appliances. However, currently available WPT technology demonstrates several shortcomings and various challenges due to allowed receiver position variation with respect to transmitter position. …

A Method For Evaluating Power Generation Concepts Considering The Optimal Concept Of Operations, Tianlei Zhang

Theses and Dissertations

When trying to select an appropriate power generation plant for a micro-grid power distribution system like an electric ship, designers must consider both the physical characteristics (e.g., weight, volume, power ratings) and performance characteristics (e.g., fuel consumption, quality of service) of all the design alternatives. Comparing the design alternatives in terms of the physical characteristics is relatively straightforward, but in terms of performance characteristics each design alternative has to be evaluated within its own optimal performance points to make a fair comparison. However, at present no effective method or software tools exist to enable this evaluation at the earliest design …