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Pulsed electric field (PEF) technology applied to food processing was firstly used in the late 1960s. The currently available systems use either conventional Blumlein generators or generators similar to those found in radar power sources to produce the required high voltage pulses. The liquid to be processed is passed through a number of treatment chambers or cells which each contain a pair of electrodes in contact with the liquid. An electric field is thereby applied to the liquid, leading to the technology being termed invasive and it can be used only with liquid food. A novel and non-invasive PEF technology for use in the food processing industry is introduced and investigated in this thesis. The technology represents a novel way of performing PEF treatment. A proof of concept arrangement uses two ceramic cylinders mounted inside the non-invasive PEF cell with a gap of 3 mm between them. A displacement current of the order of mA passes through the non-invasive PEF cell during treatment, as compared with the kA of current usually produced during an invasive treatment. The low current is not only economic in electric energy but also maintains a low food temperature, which implicitly maintains food flavour. In the thesis the electro-optic Kerr effect technique is used to perform accurately the PEF measurement and convincingly prove that strong electric fields are present. Two Kerr water cells were designed and used to determine the Kerr constant for water, since the data presented in the literature is unreliable. The first Kerr water cell uses a pair of Bruce profile stainless steel electrodes and the second a pair of parallel plate stainless steel electrodes. An electro-static solver (Maxwell software) was used to determine the electric field distribution and to calculate the electric field integral to accurately determine the Kerr constant for water. Water samples containing the E-coli bacteria were prepared and filled in the non-invasive PEF cell by the Flavometrix Company. Eight PEF experiments were successfully performed during this research programme and the results show unequivocally that the novel noninvasive technique is effective in significantly reducing the initial concentration of E-coli bacteria. This opens the door for the future design of an industrial prototype.

The air-water flow reqime transitions in a horizontal pipe under the influence of a stronq electric field perpendicular to the interface are studied. The separated flow model to predict flow regime transitions has been developed. The present version of the model is a modification of Taitel and Dukler's separated flow model. This assumes that all flow reqimes are perturbations from stratified smooth flow. Expressions for the electrical force are derived and added to the conservation and constitutive equations to obtain new transition criteria. The theoretical results are compared with observations of air-water flow in a 1.27 cm. and 1.9 cm. internal diameter pipe. Good agreement was found when no electric field was applied, however, the experimentally observed effect of the electric field was not as pronounced as predicted by theory. Further experiments to refine the theoretical model are presented. / Thesis / Master of Engineering (ME)

Recent technologies in micro-devices for investigation of functional biology in a controlled microenvironment are continually growing and evolving. In particular, electric-field mediated microfluidic platforms are evolving technologies that have significant applications in drug delivery and cell migration investigations. Although drug delivery has had several successes, in some areas, it continues to be a challenge; in recent years, the positive impact of electric fields is being explored. The primary objectives of the dissertation are to design, fabricate, and employ two novel microfluidic platforms for drug delivery and cell migration in the presence of electric fields. Description of iontophoretic carboplatin delivery into the MDA-MB-231 triple-negative breast cancer cells and investigation of neutrophil electro taxis are two main aims of the dissertation. Transdermal drug delivery systems such as iontophoresis are useful tools for delivering chemotherapeutics for tumor treatment not only because of their non-invasiveness but also due to their lower systematic toxicity compared to other drug delivery systems. While iontophoresis animal models are commonly being used for the development of new cancer therapies, there are some obstacles for precise control of the tumor microenvironment's chemoresistance and scaffold in the animal models. We employed experimental and computational approaches, the iontophoresis-on-chip and the fraction of tumor killed mathematical model, for predicting the outcome of iontophoresis treatment in a controlled microenvironment. Also, precise control over the cell electromigration is a challenging investigation which we will address in the second aim of the dissertation. Here, we developed a microfluidic platform to study the consequences of DC electric fields on neutrophil electromigration (electrotaxis), which has an application of directing neutrophils away from healthy tissue by suppressing the migration of neutrophils toward pro-inflammatory chemoattractant. / Doctor of Philosophy / Recent technologies in the micro-scale medical devices for diagnosis and treatment purposes are continually growing and evolving. Microfluidic platforms are reproducible devices with the dimensions from tens to hundreds of micrometers for manipulating and controlling fluids. In particular, electric-field mediated microfluidic platforms, are developing technologies that have significant applications in drug delivery and biological cell directional movement investigations. Although drug delivery has had several successes, in some areas, it continues to be a challenge. In recent years, the positive impact of electric fields is a significant advancement in drug delivery techniques. Transdermal drug delivery systems such as iontophoresis are useful tools for delivering chemo drugs for tumor treatment not only because of their sensitivity but also to their lower systematic toxicity compared to injection or oral drug delivery. While iontophoresis animal models are conventional for the development of new cancer therapies, there are some obstacles to precise control of the tumor scaffold in the animal models. We also developed a novel microfluidic platform to study the consequences of DC electric fields on white blood cells' (WBC) directional movement, which has an application of directing WBC away from healthy tissue by suppressing the damage of WBC accumulation in healthy organs.

A counter-current two-phase flow under an applied electric field has been studied theoretically using potential flow equations. A flooding correlation has been derived taking account of applied electric field on the interface for both adiabatic and condensing system. It is found that the electric field enhances flooding phenomena in case of adiabatic system. In the case with system involving condensation the electric field enhances flooding at low liquid flow rates and at high liquid flow rates the flooding point decreases under electric field depending on the rate of subcooling. / Thesis / Master of Engineering (ME)

Determining the molecular mechanisms at the origin of protein function remains a challenge due to the complex non-covalent interactions that shape their structure. Since the non-covalent interactions arise from charge fluctuations, electric fields can be used as a tool to quantify the interactions between a target and its environment. The contribution of each component of the system is reflected in the direction and strength of the electric field exerted on the target, which can be calculated from molecular dynamics simulations. The interactions experienced by ligands in enzymatic active sites determine the catalytic activity of the enzyme. Ligands in synthetic enzymes lack interactions with the protein scaffold, which limit their efficiency. To substitute for the role of non-effective protein scaffold, we introduced a polar DNA fragment to the enzyme vicinity, inducing electrostatic interactions that will facilitate the reaction. We found that the introduction of a DNA fragment enhanced the original interactions between the residues in the active site and the ligand, without creating new interaction hot spots. Using electric fields, we calculated a reduction in activation energy of 2.0 kcal/mol when introducing the DNA fragment, indicating a promising avenue for catalytic improvement. Inspired by the success in using electric fields to understand enzyme catalysis in the context of electrostatic preorganization theory, we generalized these fundamental concepts to another type of proteins: voltage-gated ion channels. Our results indicate that electric fields also report on channel activity. We find an asymmetry in the number of active residues for channel function between the four domains and between the two gating motifs of the permeation pathway, with domain I being the major contributor in both cases. The importance of residues for channel activity is not a simple linear correlation of their distance with the functional motif, but a relationship dominated by non-covalent interactions. Finally, we investigate the effects of loop dynamics on enzyme product inhibition. We modify the chemical nature of the unstructured loops that obstruct the active site of DszB by glycosylating serine and threonine residues. We monitor the corresponding variations in loop dynamics and their effect on the interaction between the enzyme and the product. Overall, promising results were found using electric fields in the investigation of protein mechanisms that are mainly dominated by non-covalent interactions and provide insight into the role of the individual components in the system. / Doctor of Philosophy / Although weaker than covalent interactions, non-covalent interactions play a crucial role in molecular biological processes, especially in protein mechanisms. In order to modify the properties of proteins to our advantage, we need a metric with which we can map these interactions onto the protein structure. Different types of non-covalent interactions share one similarity: they originate from the change of electron distribution of interacting atoms, therefore can be captured by analyzing the protein- generated electric fields. Synthetic enzymes are designed to better adapt to varying environments and catalyze a broader reaction range. However, they are less effective than natural enzymes because the protein scaffold does not contribute to catalysis. Indeed, protein scaffolds in natural enzymes generate an electric field that lowers the reaction activation energy in the active site. Protein scaffolds in synthetic enzyme do not generate such electric fields. To address this issue, we modified the environment of synthetic enzyme KE15, introducing a polar DNA fragment to induce interactions in the active site. This modification strengthen the interactions between protein and ligand, leading to a decrease in the energy required for the reaction. While enzymes are famous for their generation of electric fields facilitating function, we demonstrated that this phenomenon also exist in voltage-gated ion channels Nav1.7. Residues were found to exert an electric field that can facilitate ion permeation. This is not simply because of their distance to the key regions, but a result of the non-covalent interactions regulating the mechanism, with different regions showing asymmetric importance in the process. Since the governing non-covalent interactions are relatively weak, proteins are flexible, especially protein loops. In enzyme DszB, this loop flexibility enables a conformational change when the ligand binds the active site. The change in loop conformation traps the product inside the active site, limiting enzymatic turnover. To prevent active site obstruction by these flexible loops, we attached glucose to a few loop residues to modify the hydrophobicity profile near the active site. The introduction of hydrophilic glucoses helps to pull the loops towards the solvent, rather than towards the active site, limiting product inhibition while preserving catalytic activity. Overall, our results show that electric field can be applied as a general method for protein studies, relating structure to function.

For many years, the use of fiber optic sensors for the measurement of strain, temperature and pressure has been widely investigated. Much less research has been directed towards the use of these sensors for measuring electric and magnetic fields. As existing field meters have conductive parts which inherently cause field distortion, a fiber optic electric field sensor would be preferable due to the immunity of the fibers to electromagnetic interference. A novel electric field sensor is proposed which utilizes the displacement measurement capabilities of the Extrinsic Fabry-Perot Interferometric sensor, and the actuation produced by a piezoelectric material when placed in an electric field. Classical electromagnetic theory is used to mathematically model the performance of the sensor within a given electric field. Experimental and theoretical results are presented which demonstrate the ability of the proposed sensor to detect electric fields. Improvements to the proposed electric field sensor and the transition of this research into magnetic field sensing is suggested for future research. / Master of Science

Electro-Optic(EO) probing techniques are advancing rapidly in recent years due to their superior performance in characterization of semiconductor devices and circuits. Although the conventional systems can only monitor the amplitude distribution of electric field, some advanced EO probing techniques are able to measure not only the electric-field amplitude, but also direction of the electric field. Because valuable information can be released in such as chamfered bending transmission lines, patch antennas and wireless devices, etc., EO probing technique becomes an important tool to the characterization of radio frequency devices. These systems often require two beams or two different EO crystals to differentiate the directions of the electric field under test because only one type of EO modulation, compressed/stretched deformation modulation, is utilized in the measurement. Therefore, the measurements are inaccurate and complicated due to the fact that the path length and EO interaction strength of the two probing beams are different. In this research, we demonstrate the EO probing technique with one beam and one EO crystal to extract 2-D electric-field vector using an additional modulation effect, i.e. rotational deformation modulation. This electric field vector measurement technique is compact, accurate and low cost. We not only prove that on-wafer 2-D electric-field-vector measurement using single-beam electro-optic probing technique is feasible theoretically and experimentally, but also combine rotational deformation modulation and compressed/stretched deformation modulation to a practical circuit measurement. Commercial software, Ansoft Maxwell 3-D Field Simulator, is employed to verify our measurements. Good agreement is obtained between experiment and simulation results. In addition to 2-D electric-field-vector measurement, we made an attempt to high-frequency real-time measurement. With the trend of low voltage operation in wireless communication, the most serious issue of high-frequency real-time EO probing technique is the improvement of signal to noise ratio. We tried to improve the stability of laser source, control the polarization of incident beam, and utilize Fabry-Perot filter in order to implement high-frequency real-time measurement. A bandwidth of 900 MHz was achieved, which is record-high to our knowledge.

abstract: The U.S. Navy is interested in evaluating the dielectric performance of SF6 at 30 kHz in order to develop optimal bushing designs and to ensure reliable operation for the Very Low Frequency/ Low Frequency (VLF/LF) transmitting stations. The breakdown experiments of compressed SF6 at 30 kHz in the pressure range of 1-5 atm were conducted in both the uniform field (plane-plane gap) and the non-uniform field (rod-plane gap). To understand the impact of pressure on the breakdown voltage of SF6 at VLF/LF, empirical models of the dielectric strength of SF6 were derived based on the experimental data and regression analysis. The pressure correction factors that present the correlation between the breakdown voltage of SF6 at VLF/LF and that of air at 50/60 Hz were calculated. These empirical models provide an effective way to use the extensively documented breakdown voltage data of air at 60 Hz to evaluate the dielectric performance of SF6 for the design of VLF/LF high voltage equipment. In addition, several breakdown experiments and similar regression analysis of air at 30 kHz were conducted as well. A ratio of the breakdown voltage of SF6 to that of air at VLF/LF was calculated, from which a significant difference between the uniform gap and the non-uniform gap was observed. All the models and values provide useful information to evaluate and predict the performance of the bushings in practice. / Dissertation/Thesis / M.S. Electrical Engineering 2010

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