A passive wireless sensor is designed, fabricated and tested for the measurement of AC electric field in the vicinity of high voltage apparatus. This sensor is applicable in remote condition monitoring of high voltage apparatus where close distance measurements raises safety hazards for operators. The sensor is designed using a coaxial cavity resonator structure (in TEM mode) capacitively coupled to varactors. The resonance frequency of the sensor shifts corresponding to the capacitance variation of the varactors which in turn is perturbed by the external electric field. The electric field surrounding the apparatus induces a bias voltage over the terminals of the varactors. Therefore, the resonance frequency changes proportional to the inducing external electric field and correspondingly to the medium/high voltage. A printed circuit board on the top of the cavity provides coupling between the cavity and varactors and also between the varactors and the external field produced by the high voltage apparatus. The sensor structure is designed to resonate in the range of 2.4 GHz to 2.5 GHz of the industrial, scientific and medical (ISM) radio frequency band. A remote interrogation system identifies the instantaneous resonance frequency of the sensor by transmitting pulses of radio frequency (RF) signal and recording the ring back of the resonator. The ring back is down converted and analyzed to determine the resonance frequency of the sensor. Two possible applications of the sensor, i.e. voltage measurement and defect detection of insulators, are demonstrated by experimental results. / February 2017

No description available.

Electro-optical properties of thin film are of great interest owing to the perpetual demand for miniaturization and higher speed devices for communication, electronic, and biomedical applications. The thickness of polymer films developed for these applications has decreased dramatically making interfacial effects significant. It is well documented that, in submicron thickness range, both film/substrate & film/air interface are critical. In this study, we probe the dynamics of electro-optical polymer thin films in the sub-micron thickness regime to understand interfacial effects. The polymer chain dynamics of Polypropylene oxide (PPO) under electric field are investigated in this study. The effects of electric field strength, frequency, and polymer molecular weight on the polymer chain dynamics under electric field are studied. Experimental results show that PPO exhibits both piezoelectric and electrorestrictive effects at significantly high frequencies (101kHz range). Conventional organic materials are responsive only at frequencies in <1kHz range. A high signal-to-noise ratio differential interferometry is designed to quantitatively study the effects of film thickness, electric field frequency and amplitude on the dynamic properties of PPO thin films ranging from 30 nm to 400 nm. The interferometer can concurrently monitor the index of refraction, thickness change of polymer films, and birefringence due to the applied electrical field. / Master of Science

No description available.

<p>Electric field mediated gene delivery (EFMGD) or electrotransfection is a popular, non-viral gene delivery method that has been used in a variety of studies and applications ranging from basic cell biology research to clinical gene therapy. Yet, the mechanism(s) by which electrotransfection facilitates DNA delivery across the cell membrane into the cell and its subsequent intracellular transport across the cytosolic space towards the nucleus have been insufficiently studied and still remain controversial. Understanding these mechanisms and characterizing the intracellular journey of pDNA is important for understanding the physiological barriers of EFMGD within the cell, which can be used to engineer better solutions to overcome these barriers with the ultimate goal of improving the transfection efficiency of this technology. </p><p>Conventional thought in the field assumes that such transport modes as diffusion, electrophoresis, and electro-osmosis, which govern the entry of small molecules into cells through electric field-generated transient membrane pores, also apply to electric field-mediated delivery of therapeutic DNA. We propose that electrically-induced gene transfer into cells is governed by an alternative, more active mode of transport that entails the involvement of cellular endocytic processes. It is our hypothesis that pulsed electric field generate these membrane pores which interact with nearby DNA molecules; but that actual DNA translocation across the membrane is driven by endocytosis, which consequently, then, also plays a role in the intracellular transport of the DNA. To this end, we first investigated the dependence of electrotransfection efficiency (eTE) on binding of plasmid DNA (pDNA) to plasma membrane. Binding concentrates DNA molecules in the vicinity of the cell membrane, which should theoretically result in a greater number of DNA-membrane interactions during pulsed electric field, more internalized DNA, and ultimately, higher eTE values. We demonstrated that supplementing the electrotransfection buffer with divalent cations (Ca2+ and Mg2+) is an effective method of promoting pDNA adsorption to the cell membrane. This cation-mediated increase in DNA adsorption to the cellular membrane resulted in a consequent increase in eTE, up to a certain threshold concentration for each cation. To determine the timeframe for completion of pDNA internalization following pulse treatment, trypsin treatment was applied to cells at different timepoints after electrotransfection to strip off any residual, membrane-bound pDNA that had not been internalized. Trypsin treatment at 10 min post electrotransfection still resulted in a significant reduction in eTE, indicating that the time period for complete cellular uptake far exceeded the lifetime (~ 10 msec) of electric field-induced transient pores. The role of endocytosis was further probed by noting the effect on eTE when cells were treated with three endocytic inhibitors (chlorpromazine, genistein, dynasore) targeting different internalization mechanisms or silenced of dynamin expression using specific, small interfering RNA (siRNA). siRNA silencing and all three pharmacological inhibitors yielded substantial and statistically significant reductions in the eTE. Taken together, these findings suggest that the mechanism of electric-field mediated DNA internalization entails: (i) binding of pDNA to cell membrane and (ii) endocytosis of membrane-bound pDNA.</p><p>The same strategies of pharmacological endocytic inhibition and siRNA silencing was used to further explore and compare electric field-induced pDNA internalization in additional cell lines that differ in terms of cell type, proliferation rates, proliferative capacity (i.e. primary versus immortalized/cancer line), etc. in order to determine whether endocytosis is a universally implicated mechanism across many cell lines. Results showed different endocytic pathways to be recruited for pDNA uptake in a cell-dependent manner and that one or multiple pathways may contribute to uptake within a cell line. </p><p>Taken together, the studies presented in this dissertation provide both indirect and direct evidence suggesting an endocytic role in the translocation of pDNA across the cell membrane and its intracellular routing towards the nucleus for EFMGD. These seminal findings could potentially lead to better understanding of the intracellular barriers encountered by EFMGD, more strategic optimization of electrotransfection parameters than the trial-and-error approach currently used, and enhanced transfection efficiencies.</p> / Dissertation

The thesis designs, constructs, and tests an electrically small dipole antenna probe for the measurement of electric field distributions induced by a transcranial magnetic stimulation (TMS) coil. Its unique features include high spatial resolution, large frequency band from 100 Hz to 300 kHz, efficient feedline isolation via a printed Dyson balun, and accurate mitigation of noise. Prior work in this area is thoroughly reviewed. The proposed probe design is realized in hardware; implementation details and design tradeoffs are described. Test data is presented for the measurement of a CW capacitor electric field, demonstrating the probe’s ability to properly measure conservative electric fields caused by a charge distribution. Test data is also presented for the measurement of a CW solenoidal electric field, demonstrating the probe’s ability to measure non-conservative solenoidal electric fields caused by Faraday’s law of induction. Those are the primary fields for the transcranial magnetic stimulation. Advantages and disadvantages of this probing system versus those of prior works are discussed. Further refinement steps necessary for the development of this probe as a valuable TMS instrument are discussed.

The aim of this research was to develop an instrument that fills a niche in geophysical instrumentation for a tool that is fast, non-contact or minimal contact, and specifically optimised for discrete, near-surface, electrically resistive targets in resistive and conductive environments. This aim was sought to be achieved through the development of a new Capacitive Array Resistivity with Inductive Source (CARIS) system. Two CARIS systems were produced and thoroughly tested. A first prototype instrument CARIS-1, operating at 100KHz, was developed for proof of concept in the laboratory and initial field testing. A second prototype CARIS-2, operating at 5kHz, was developed for further fielding testing and trial mapping experiments. Several major conclusions have been reached through the development and testing of the CARIS systems. Firstly, the CARIS system can clearly detect objects in a conductive homogeneous liquid, with high repeatability of data. This result reinforced the concept of the CARIS method, and established the stability of the instrumentation in laboratory environments. The approach was validated by close correlation between measurements and modelling. Secondly, the CARIS system is able to measure responses to near-surface conductivity variation in field conditions with high repeatability. Data collected also showed spatial consistency with GPR, Resistivity and mapped culture. It was determined that properties of the near surface, such as moisture content and soil consolidation, can significantly affect the electrical homogeneity of the medium and thus the uniformity of the background reading. The CARIS systems thus had a limitation that they proved to be quite sensitive to variations of this nature. Thirdly, foll owing from the second conclusion, although the aim of the CARIS system was to detect the presence of discrete buried objects, CARIS proved to be more responsive to the effects of the burial process rather than the objects themselves. It was concluded therefore that the method of excavation, burial, and refill material were of high significance in CARIS interpretation. This conclusion was reinforced by the results of theoretical modelling which showed that shallow boundaries of small conductivity contrast could quite easily produce more significant anomalies than target objects which are deeper and have higher contrast.

Propagation of radiation in a waveguides is theoretically described by Maxwell&amp / #8217 / s equations. The gradient of refractive index and an influence on the waveguide by a superstrate requires a numerical solution of the differential equation. Iterative methods such as the Runge-Kutta approaches are used to calculate the effective refractive index in the waveguide depending on the superstrate&amp / #8217 / s and the waveguide&amp / #8217 / s local refractive indices. In this study,the refractive indices, and the model fields of the TE00 modes are calculated. The calculated fields of the 00 TE modes give information about the propagation of the light in the waveguide. Also, the precision of the Runge-Kutta aproaches has been tested. The advantages and disadvantages of the Runge-Kutta aproaches are discussed.

By means of molecular dynamics simulation the effect of external direct current electric field on the polyethylene-like (PE-like) polymer and methyl chloride solvent system is investigated. Three systems include normal solution, dilute solution, and lower-density solution are simulated. For each system, four conditions include non-charged polymers in nonpolar solvents, non-charged polymers in polar solvents, charged polymers in nonpolar solvents, and charged polymer in polar solvents are simulated. The diffusion behavior of polymer in solvent is as functions of electric field, polarity of solvent molecules, and polarity of polymer. When an electric field is applied to the system include dielectric molecules, our calculation shows that the center of mass diffusion constant of polymer depends on the alignment of charged polymer or polar solvent molecules, the mobility of charged polymer or solvent molecules and the density of the system. The mobility of polar molecules results in the increase of the center of mass diffusion constant of polymer. The alignment of polar molecules results in the increase of fluid viscosity. This decreases the center of mass diffusion constant of polymer.

A MEMS based electrostatic field sensor is presented which uses capacitive interrogation of an electrostatic force deflected microstructure. First the deflection of the sensor’s membrane which is caused by electrostatic force in the presence of electric field is calculated both by simulation and theoretical model and it has been shown that the results of the simulations have acceptable values compared to the theoretical ones. Simulation models have also been designed to improve the vibration of the membrane for measuring the ac electric fields. It has been shown that by adding perforations to the surface of the membrane, it is possible to reduce the air drag force effect on the membrane and still have similar electrostatic force on the membrane. Therefore, it is possible to reduce the damping due to air resistance in membrane movement when measuring ac fields. After successful modeling of the sensor structure, the fabrication process for the sensor has been designed. The electroplating process as the most important fabrication step has been studied in detail prior to starting the fabrication of sensor. The process parameters for electroplating process, such as current amplitudes, duty cycle and frequency have been optimized to get the lowest surface roughness to thickness ratio for the electroplated films. A lithography molding process was developed for the electroplating. Both dc and pulse plated films have been studied to show the role of pulse plating in improving the quality of the electroplated films. It was found during the release process that the electroplated copper interacted with sulfur during plasma etching of silicon. However, the result of the releasing process was very helpful to find the best recipe of releasing and they can be used in next projects.