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Characterization of a multi-heme cytochrome c from Heliobacterium modesticaldum genome

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Heliobacterium modesticaldum (H. modesticaldum) is an anaerobic photoheterotroph that can produce molecular hydrogen (H2) when it is fixing dinitrogen (N2). In addition, electrons can be injected into this organism via an electrode and redox mediator in a light-dependent fashion, as

Heliobacterium modesticaldum (H. modesticaldum) is an anaerobic photoheterotroph that can produce molecular hydrogen (H2) when it is fixing dinitrogen (N2). In addition, electrons can be injected into this organism via an electrode and redox mediator in a light-dependent fashion, as shown recently by the Redding and Jones research groups. These factors make H. modesticaldum an ideal organism for use in a microbial photoelectrosynthesis cell, in which electricity can be used to power specific metabolic processes that produce a desired compound (e.g. H2). However, the injection of electrons into this organism is not optimal, which may limit the H2 production rate. There is a gene (HM1_0653) in the genome encoding a multi-heme cytochrome c that is similar to the proteins known to be used for exit of electrons in the well- known electrode-respiring bacteria (e.g. Geobacteria). RNA-sequencing in the Redding lab has shown that the HM1_0653 gene is very poorly expressed in H. modesticaldum. Boosting expression of this cytochrome could lead to faster electron transfer into the cells and thereby more H2 production via photoelectrosynthesis. In order to gain a deeper understanding of this protein, it was expressed in E.coli by two different versions: (1) the entire gene and (2) a truncated gene with an additional hexahistidine tag (truncHM1_0653). Both cultures had a pink color, indicating the biosynthesis of cytochrome. It was discovered that the HM1_0653 protein was likely released into the medium and shows the most promise for ease of purification of HM1_0653. Furthermore, we explored protein expression in H. modesticaldum using the current transformation system in the Redding Lab, but the combination of gene toxicity and copy number of the vector resulted in cloning difficulties in E.coli. An alternative vector may prove more successful.

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2017-05

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Development of Frequency Selective Surfaces for RF Interrogator Design

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The honors thesis presented in this document describes an extension to an electrical engineering capstone project whose scope is to develop the receiver electronics for an RF interrogator. The RF interrogator functions by detecting the change in resonant frequency

The honors thesis presented in this document describes an extension to an electrical engineering capstone project whose scope is to develop the receiver electronics for an RF interrogator. The RF interrogator functions by detecting the change in resonant frequency of (i.e, frequency of maximum backscatter from) a target resulting from an environmental input. The general idea of this honors project was to design three frequency selective surfaces that would act as surrogate backscattering or reflecting targets that each contains a distinct frequency response. Using 3-D electromagnetic simulation software, three surrogate targets exhibiting bandpass frequency responses at distinct frequencies were designed and presented in this thesis.

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2021-05

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Flexible Fractal-Inspired Metamaterial for Head Imaging at 3 T MRI

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The ability of magnetic resonance imaging (MRI) to image any part of the human body without the effects of harmful radiation such as in CAT and PET scans established MRI as a clinical mainstay for a variety of different ailments

The ability of magnetic resonance imaging (MRI) to image any part of the human body without the effects of harmful radiation such as in CAT and PET scans established MRI as a clinical mainstay for a variety of different ailments and maladies. Short wavelengths accompany the high frequencies present in high-field MRI, and are on the same scale as the human body at a static magnetic field strength of 3 T (128 MHz). As a result of these shorter wavelengths, standing wave effects are produced in the MR bore where the patient is located. These standing waves generate bright and dark spots in the resulting MR image, which correspond to irregular regions of high and low clarity. Coil loading is also an inevitable byproduct of subject positioning inside the bore, which decreases the signal that the region of interest (ROI) receives for the same input power. Several remedies have been proposed in the literature to remedy the standing wave effect, including the placement of high permittivity dielectric pads (HPDPs) near the ROI. Despite the success of HPDPs at smoothing out image brightness, these pads are traditionally bulky and take up a large spatial volume inside the already small MR bore. In recent years, artificial periodic structures known as metamaterials have been designed to exhibit specific electromagnetic effects when placed inside the bore. Although typically thinner than HPDPs, many metamaterials in the literature are rigid and cannot conform to the shape of the patient, and some are still too bulky for practical use in clinical settings. The well-known antenna engineering concept of fractalization, or the introduction of self-similar patterns, may be introduced to the metamaterial to display a specific resonance curve as well as increase the metamaterial’s intrinsic capacitance. Proposed in this paper is a flexible fractal-inspired metamaterial for application in 3 T MR head imaging. To demonstrate the advantages of this flexibility, two different metamaterial configurations are compared to determine which produces a higher localized signal-to-noise ratio (SNR) and average signal measured in the image: in the first configuration, the metamaterial is kept rigid underneath a human head phantom to represent metamaterials in the literature (single-sided placement); and in the second, the metamaterial is wrapped around the phantom to utilize its flexibility (double-sided placement). The double-sided metamaterial setup was found to produce an increase in normalized SNR of over 5% increase in five of six chosen ROIs when compared to no metamaterial use and showed a 10.14% increase in the total average signal compared to the single-sided configuration.

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2022-05