Doctor of Philosophy (Ph.D.), University of Dayton, 2021, Electro-Optics

Mode-locked oscillators are the building blocks to generate ultrafast pulses which can then be used for many applications, including optical communication, metrology, spectroscopy, microscopy, material processing, as well as many applications in the healthcare industry. Mode-locked fiber oscillators are especially popular for their compactness, efficiency, and beam quality compared to their solid-state counterparts such as Ti: Sapphire lasers. Apart from their practicality, the mode-locked fiber lasers are an interesting object for studies, as they represent dynamically rich nonlinear systems. For ultrafast fiber oscillators at normal dispersion, a spectral filter is the utmost important optical component that determines the behavior of these systems in terms of the spectral bandwidth, pulse duration, central wavelength of the output spectra, multipulse dynamics, pulse structure as well as pulse velocity. Recently, there is a growing interest in fiber based spectral filters as they facilitate the construction of all-fiber laser cavities. This dissertation investigates the laser performance parameters by developing an all-fiber spectral filter and exploiting its characteristics. Especially, this dissertation reports the first experimental observation of dissipative solitons of the complex Swift Hohenberg equation. This is very important as it births multiple future projects related to implementing higher order spectral filtering in mode-locked fiber lasers. Although most of the ultrafast oscillators in this dissertation are built at 1 μm, ideas to build mode-locked lasers at visible wavelengths are also presented along with primary numerical simulation and experimental results. Finally, all the upcoming research directions are discussed in detail.

PhD, University of Cincinnati, 2019, Engineering and Applied Science: Materials Science

In the fast-growing field of energy storage devices, using Carbon Nanotubes (CNTs), as part of the electrode structures brings significant advantages due to the superior electrochemical performance of devices made from them. This has been ascribed to their high surface area, electrical conductivity, charge transport capability, mesoporosity, and electrolyte accessibility. Furthermore, CNT can be assembled into sheets, ribbons, and fibers amongst other types of assemblages, which made these nanotube form materials of interest in the field of wearable electronics. In this work, we have explored new design and fabrication of CNT based fiber supercapacitors (FSC) with increased energy and power densities and have investigated the approaches by which their electrochemical performances can be improved. Increasing the surface area and tuning of the pore sizes have been identified as some of the ways to enhance the electrochemical properties of supercapacitors. By employing a dry spinning process of Chemical Vapor Deposition (CVD) synthesized CNT arrays, we created CNT fibers, which can be used as electrodes for fiber-based supercapacitors. We successfully achieved enhanced surface area and alteration of pore width in our CNT fibers by employing an atmospheric pressure oxygen plasma functionalization process (OPFCNT). The presence of functional groups on the surface of the fibers is proved by X-Ray Photoelectron Spectroscopy (XPS) and Raman Spectroscopy, while the increase of their surface area is demonstrated by Brauner-Emmett-Teller (BET) measurements, UV-Vis Spectroscopy, and Randles Sevcik method. We housed active materials (polyaniline (PANI)) in our OPFCNTs. The CNT-PANI electrodes were produced by employing chemical oxidation polymerization of PANI on oxygen plasma functionalized CNT (OPFCNT) fibers. We also investigated the use of ionic liquid electrolytes in our fiber supercapacitor devices to improve the energy and power densities of the fabricated devices. (open full item for complete abstract)

Doctor of Philosophy, The Ohio State University, 2023, Nuclear Engineering

Nuclear energy is a promising solution to growing global energy consumption. Challenges such as initial investment, siting constraints, and concerns over safety, waste, and proliferation persist. Advanced reactor designs offer solutions to many of these challenges. In Parallel, there is a growing demand for innovative sensors, especially optical fiber-based sensors, to support the developmental endeavors of nuclear technology. Optical fiber sensors, which are resistant to electromagnetic interference, have the capability to provide multi-parameter sensing and multiplexing, offer potential advantages in monitoring various operational parameters in extreme conditions. The focus of this work is on both silica and sapphire optical fibers, aimed to serve as distributed temperature sensors in high-temperature radiation environments. Silica optical fibers, which have found extensive use in telecommunications, have been researched for nuclear applications. However, their practical deployment as distributed sensors in fueled experiments has yet to be realized. Sapphire optical fibers are being developed for fabrication and sensing, including exposure to temperatures and conditions previously unexplored. This research delves into the intricacies of designing, calibrating, and deploying these fiber optic-based sensors in high-temperature and radiation environments. Silica fibers were exposed to various conditions, from transient irradiation to high fluence levels, to ascertain their efficiency and robustness. Sapphire fibers, on the other hand, were tested in temperature and irradiation experiments, revealing their potential for ultra-high temperature applications. This work sheds light on the potential of optical fiber-based sensors, especially in high temperature radiation environments. It offers a roadmap for their deployment, including design considerations, calibration methods, and practical applications. The findings suggest silica optical fibers' robustness under dive (open full item for complete abstract)

MA, Kent State University, 2018, College of the Arts / School of Art

Disease is like death. It is not worthy to be spoken of. It is eroding from the inside, taking energy and destroying minds. It is vicious and must not be glorified. But Soul eager to survive at all costs and Body as an evidence of a crime committed by disease, - they are uniting in a single burst and giving birth to the Inspiration. Revelation creates images. Images are moving, puzzling into the pictures and freezing, caught by a digital camera. They acquired a new dimension and new depth not by printing on glossy paper but by weaving into the sophisticated Cloth. Blind Fate or personal choice? Darkness in light or the light in the darkness? Fight or surrender? Faith or unbelief? Life or Death? The eternal questions that humanity as a whole and each of us as a part are asking ourselves, I am trying to answer through the artistic engagement of digital photography and jacquard weaving. I am using a woven structure as a poetic language, evoking shapes, rhythm, and space in unexpected juxtaposition. Immobilized Time turns into a texturally patterned textile that represents the space-time fabric with the imprint of the story of one soul. As the body and soul are two unbreakable parts of one, the photography and jacquard cloth are interwoven in one, reincarnating the flat graphic image into a tactile and multidimensional augmented reality of the textile body, where every part carries meaningful ideas and coded thoughts.

Master of Science (M.S.), University of Dayton, 2014, Electro-Optics

This thesis focuses on the design, fabrication, and characterization of tapered optical fibers for high sensitivity refractive index sensing. Single-mode fibers were tapered to a diameter of a few microns causing multiple cladding modes to be excited and to propagate through the taper waist. The presence of multiple modes creates an interference pattern in the output signal. Tapered regions serve as the sensing interface, such that the light propagating through/around the fiber interacts with molecules tethered to the tapered surface. The transmission spectrum is measured by scanning the wavelenght of an external cavity, tunable semiconductor laser. We observe an oscillating transmission spectrum as the wavelength is scanned due to multiple waveguide modes interfering as they are combined in the up-taper region of the fiber. The output spectrum oscillations exhibit a phase shift due to changes in the refractive indices of the solution surrounding the fiber. We introduce a Fourier analysis of the transmission data to extract the amplitude and phase of the data. The Fourier data is filtered to study the dominant oscillation frewqunecy in the data and extract the phase change in the data. The changes of the refractive index near the fiber surface can be measured as a phase shift in the output. The Fourier signal processing technique allows for accurate determination of the signal phase which is correlated with a small index change. Conservatively we can measure refractive index changes to an accuracy of 5x10-4 for our fiber. The tapered fiber sensing platform (fiber and Teflon flow cell) allows for fast and economical fabrication of fiber sensors.

MS, University of Cincinnati, 2005, Engineering : Electrical Engineering

A large portion of the cost and turnaround time of most commercial optoelectronic devices is fiber packaging. Reducing the packaging time, elimination of superfluous components and facilitating automation of packaging processes greatly aid in reducing the overall cost of an optoelectronic device. Many new methods are being developed to achieve these varied goals, and this work aims at presenting a new technique to achieve these goals. A new technique for bonding optic fiber directly to silicon or glass submounts for auto-aligned direct fiber attachment, based on field-assisted bonding has been demonstrated. The process is based on the principle of oxide bond formation between metal and glass at high temperatures under the influence of an electric field. Two methods, namely attaching an optic fiber to metallized silicon v-grooves and attaching metal coated fibers to Pyrex v-grooves, have been achieved and bond strengths of over 300g have been demonstrated for both cases. Fibers attached by this method also exhibited a high degree of thermal stability of coupling over a range of 25-80°C. This novel combination of field assisted bonding with appropriately coated fiber on precision fabricated v-grooves eliminates lenses and packaging time, will lead to lower-cost packages, and will facilitate multi-component optical submounts and other novel optoelectronic technology.

Doctor of Philosophy (PhD), Wright State University, 2023, Engineering PhD

Blood flow dynamics plays a critical role in maintaining tissue health, as it delivers nutrients and oxygen while removing waste products. It is especially important when there is a disruption in cerebral autoregulation due to trauma, which can induce ischemia or hyperemia and can lead to secondary brain injury. Thus, there is a need for noninvasive techniques that can allow continuous monitoring of blood flow during intervention. Optical techniques have become increasingly practical for measuring blood flow due to their non-invasive, continuous, and relatively lower-cost nature. This research focused on developing a low-cost, scalable optical technique for measuring blood flow by implementing speckle contrast optical spectroscopy using a fiber-camera-based approach. This technique is particularly well-suited for measuring blood flow in deep tissues, such as the brain, which is challenging to access using traditional optical methods. A two-channel continuous wave speckle contrast optical spectroscopy device was developed, and the device was rigorously tested using phantoms. Then, it is applied to monitor blood flow changes in the brain following traumatic brain injury (TBI) in mice. The results indicate that trauma-induced significant blood flow decreases consistent with the recent literature. Overall, this approach provides noninvasive continuous measurements of blood flow in preclinical models such as traumatic brain injury.

MS, Kent State University, 2022, College of Arts and Sciences / Department of Chemistry and Biochemistry

Liquid crystals (LCs) are at the forefront of technology today. From LC displays in smartphones and televisions to “smart glass” windows, LCs are found in technology all around us. LCs offer a variety of uses due to their birefringent properties that act at room temperature. These properties show an optical change at room temperature with a small change from external stimuli. These stimuli can include temperature, electric field, and the presence of volatile organic compounds (VOCs). This work looks at projects which focus on how to best package LCs to work as sensors to their external stimuli, as well as new ways to record their detection. The first project covered in this work looks at electrospun fibers with a nematic LC core and polymer sheath as VOC sensors. It has been shown in the past that these electrospun fiber mats show an optical response to VOC exposure, but there was little quantitative work one to show the true sensing abilities of these fiber mats. This work uses the change in the LC core's electrical properties to measure the change in resistivity of the fiber mat as it was exposed to acetone. The results of these experiments are promising as the fiber mat detector had a comparable sensing ability to that of commercial VOC sensors. While the fiber mats had a good sensing ability, they are thin and likely not durable enough to be made into clothing. Putting cholesteric LC on the outside of thread, though, has shown promising results to be woven and retain temperature sensing capabilities. This project builds off of a previous project done in the group to coat thread in LC and a polymer. This LC clad fiber would then be woven into a textile. The purpose was to evenly coat the fiber and LC with no beading. Then, a polymer coating was needed to contain the LC so that it would not wash or be rubbed off. This project is still ongoing in the group. These projects aim to use LCs as sensors in a new way. By containing the LC within a fiber or within (open full item for complete abstract)

Doctor of Philosophy, University of Akron, 0, Chemical Engineering

Filter media are generally used in various filtration applications. Few of the applications of the filter media are to separate dispersed water droplets from the diesel fuel or to separate the solid aerosols from the gas stream. Filter membranes currently available in the market show a filtration efficiency of >95% but higher efficiencies usually correspond to higher pressure drops. High-pressure drop is undesired as they result in a higher cost of operating the filter membranes. Electret filters have known to attract particles from the fluid stream thus achieving high filtration efficiency but at a lesser pressure drop. The main objective of this work was to prepare a charged fibrous structure that can be used in filtration applications with high filtration efficiencies and reduced flow resistance. The charged fibrous structures evaluated in this research were flat fibrous membranes and fiber yarns. To analyze the effects of charges on these fibrous structures, both the membrane and yarn samples were polarized using a custom fabricated polarization device. Samples were polarized by simultaneously stretching, heating, and electrifying to orient the dipoles. For this, a piezoelectric polyvinylidene fluoride (PVDF) polymer was selected as the fiber material of the samples. Nonpolarized and polarized samples in the fibrous structures of membranes and yarns were evaluated for charge and filtration performances. The charge measurements showed the fiber yarn samples had nearly twice the charge per sample mass as the fiber membrane structures. The characterization study showed that the mechanical stretching during electrospinning of the yarns resulted in more dipole orientation which resulted in higher charges on the fiber yarn samples compared to the randomly oriented membrane structures where lower mechanical stretching was observed during electrospinning. An FTIR analysis determined the fraction of  phase in yarn samples was nearly twice that of the membrane struct (open full item for complete abstract)

MS, University of Cincinnati, 2022, Engineering and Applied Science: Chemical Engineering

Additive manufacturing (AM) or 3D printing is a quick growing field allowing the creation of complex structures through raw materials and a computer made design. There are many types of 3D printing, however many of the most common are not environmentally friendly. Wood fiber could be a substitute for the plastics or metals that are commonly used in 3D printing today. Wood fiber is both environmentally friendly and economical. Some research has been done in the field of 3D printing with wood-based materials, most of which utilizes wood powder or fiber reinforcement of plastics. Wood powder is unable to create a strong structure due to the small particle size. The utilization of whole wood fibers would create a stronger structure at the expense of viscosity and extrusion capabilities. This work was done to explore the viability of 3D printing using whole fibers. This included looking into optimal fiber type, beating time, and fiber to starch ratio. It was found that extrusion of pure non-beaten fibers is difficult. The addition of starch as well as beating improved both extrusion and stability of the dried product. The wood fiber to starch ratio was able to be increased to just over seventy percent wood fiber by weight. Structural integrity, drying time and extrusion could be improved upon in future work. This work shows that the potential for large scale 3D printing using wood fibers as an environment and economical solution for specific uses is there.

Master of Science, The Ohio State University, 2021, Mechanical Engineering

Spectroscopy is one of the more common scientific practices in the realm of astronomy because it allows astronomers to deduce properties of stars, galaxies, and other celestial objects, such as mass, temperature, chemical composition, redshift, presence of orbiting bodies, and more. Specifically, multi-object spectroscopy has become popular in ground-based astronomy for accumulating large quantities of data. This data is collected with optical fibers located at a telescope's focal plane that then send the collected light to instruments called spectrographs for analysis. Up until recently, these fibers were always fixed in stationary configurations. Now, the astronomy community has begun working with fiber positioning robots that can dynamically and automatically reconfigure the fibers. This functionality allows for more observing time, and thus more data collected, each night that previously would have been spent manually reconfiguring fibers. One such project employing this new strategy is the Sloan Digital Sky Survey (SDSS-V). A lot of work goes into preparing instruments with robotic fiber positioners, and a great deal of effort is put in to retire as much risk as possible before delivery to observatories. This thesis discusses the development and implementation of an optical measurement system that serves to measure the positional accuracy performance of the fiber robots and that is used to develop and exercise the software package to be used with the Focal Plane System instruments of SDSS-V prior to arrival on-site. Specifically, the fixed fiber-illuminated fiducial metrology, opto-mechanical design of the measurement system, and the development of the optical transform to be used to evaluate robot positional accuracy is detailed herein. This lab-based pre-commissioning strategy is unique to the subset of these instruments with connectorized fibers since they can operate without being interfaced with a telescope and spectrograph(s). From a software (open full item for complete abstract)

Doctor of Philosophy, Case Western Reserve University, 2020, Physics

MRI is one of the most commonly used medical imaging techniques and the quest for higher image quality and reduced scan time has been driving various developments in this modality. In the thesis, three advances in MRI hardware and software are presented. Magnetic resonance fingerprinting (MRF) is a new imaging technique that allows quantification of intrinsic tissue parameters. Two deep learning models are built to achieve fast and accurate reconstruction for spatial-temporal MRF signals. The first model performs image de-aliasing before the traditional MRF reconstruction. The second model provides an end-to-end MRF reconstruction without any additional processing. The end-to-end model returns the highest reconstruction accuracy while showing a great advantage in time efficiency in both signal acquisition time and reconstruction time. A shim coil is designed to cancel the susceptibility-induced field inhomogeneities at the back of the knee. The current density of the shim coil is inversely calculated using a target-field approach. The resulting field inhomogeneities can be reduced by more than 50% in the region of interest with a finite-length cylindrical coil and a current consumption of only 242 mA. As an attempt to replace the coaxial cabling in the MRI interconnect, a digital fiber-optic transmission system using delta-sigma modulation (DSM) is presented. Initial bench tests are conducted with a commercial DSM. System linearity is measured and a dynamic range of approximately 70 dB is observed, which is only about 10 dB away from the requirement of full-bandwidth (±500 kHz) MR signal transmission. The system is expected to provide sufficient dynamic range for practical MR signal transmission using a custom DSM chip currently being developed in our collaboration.

Master of Science in Biomedical Engineering (MSBME), Wright State University, 2019, Biomedical Engineering

Neurovascular coupling is an important concept that indicates the direct link between neuronal electrical firing with the vascular hemodynamic changes. Functional Near Infrared Spectroscopy (fNIRS) can measure changes in cerebral vascular parameters of oxy-hemoglobin and deoxyhemoglobin concentrations and thus can provide neuronal activity through neurovascular coupling. Currently many commercial fNIRS devices are available, but they are limited by the number of channels (usually having only 8 detectors), which can limit the sensitivity, contrast, and resolution of imaging. High-density imaging can improve sensitivity, contrast, and resolution by providing many measurements and averaging the signals originating from the target cerebral focus area compared to background tissue. Here a multi-channel, low-cost, high-density imaging system based on scientific CMOS (Complementary Metal-Oxide-Semiconductor) detector will be presented. The CMOS camera is fiber-coupled such that on one end fibers are focused on the pixels on the CMOS camera, which allows individual pixels (or binned sub-pixels) to act as detectors, while the other end of the fibers can be positioned on a wearable optical probe. After the device details, I will show the device validation using a series of the dynamic flow phantom experiments mimicking the brain activation and finally human motor cortex experiments (finger tapping experiments). The results demonstrate that this system can obtain high-density data sets with higher contrast and resolution. This wearable, high-density optical neuroimaging technology is expected to find many applications including pediatric neuroimaging at clinics and assessing human cognitive performance.

Master of Science, University of Toledo, 2018, Civil Engineering

Carbon fiber reinforced polymer (CFRP) reinforcement has been studied as an alternative to steel reinforcement due to steel's high susceptibility to corrosion in bridge girders. The use of deicing salts on roads during extreme cold is the primary cause of the corrosive environment due to salt percolation through cracks. This research manifests the flexural behavior of carbon fiber polymer reinforced beams in prestressed and non-prestressed conditions as well as the variation of the behavior from conventional steel reinforced beams including the design procedure of a prestressed CFRP box section beam through a case study. Unlike steel, CFRP has different stress versus strain relationship - linear without a definite yield point. A review of literature is done regarding the history, properties, applications, and researches in this field. A comparative study is done between the behavior of CFRP reinforced beams using previously tested rectangular and decked bulb T-beams. The study also focuses on the field of application, guidelines, and provisions in different parts of the world, design procedure, characteristics and weaknesses of the material, handling of CFRP in the field, and its design. The application of CFRP as the main reinforcement is scarce because of its brittleness and limited research. However, the strength and lightness make this material ideal for use in the construction industry. It is important that these beams have adequate ductility to prevent sudden failure. Ductility of similar types of beams with conventional and CFRP materials are studied and compared through deformability index. Several methods of calculating ductility are discussed and an ACI method is selected to find the ductility of each beam and a comparative study is done. The behavior of prestressed CFRP tendon is examined when it is used as an alternative to the conventional steel tendon through a case study relating different provisions of code through the design of a prestressed (open full item for complete abstract)

Doctor of Philosophy, University of Akron, 0, Chemical Engineering

The motions of droplets on fibers are important to many industrial applications. In particular, the movements of drops control the performance of fibrous filters. Fibrous filters are widely used in the petrochemical industries to separate aerosol droplets from air to protect the environment and worker health. The performance of a filter medium depends on factors like fiber size, droplet, face velocity, liquid properties and gas conditions. In the operation of a fibrous filter, the droplets carried by a flowing gas are captured by the filter medium due to collisions with the fibers of the medium. Liquid droplets can deform when forces are applied and, when captured on fibers, the droplets can spread over the fiber surface, coalesce into larger drops, and can migrate within the filter as drops or as a flowing film. The movements of the drops on the fibers after they are captured require study to develop theory, correlations, and data to validate models. The overall goal of this dissertation work is to develop new generalized theory for design and manufacture of gas-liquid separation media by developing correlations for gas flow conditions and movements of liquid drops in fibrous media. These relationships will enable the design and development of the next generation of fibrous filtration/separation media with superior performance. There are four experimental tasks to achieve this goal. Experiments on droplet interactions with single fibers, crossing fibers, thin and thick mats. These experiments were conducted to study the shape and migration of drops on fibers and provide fundamental understanding and insight as to how drops attach to, move on and detach from fibers. Different liquids with different drop sizes were tested that give a range of contact angles on the fibers. Different fiber materials with different fiber diameters were evaluated that give a range of surface properties. The liquids, fibers materials and sizes, and droplet sizes were selected as those (open full item for complete abstract)

Doctor of Philosophy (Ph.D.), University of Dayton, 2017, Electro-Optics

We describe the fabrication bi-tapered optical fiber sensors designed for shorter wavelength operation and we study their optical properties. The new sensing system designed and built for the project is a specialty optical fiber that is single-mode in the visible/near infrared wavelength region of interest. In fabricating the tapered fiber we control the taper parameters, such as the down-taper and up-taper rate, shape and length, and the fiber waist diameter and length. The sensing is mode is via the electromagnetic field, which is evanescent outside the optical fiber and is confined close to the fiber's surface (within a couple hundred nanometers). The fiber sensor system has multiple advantages as a compact, simple device with an ability to detected tiny changes in the refractive index. We developed a supercontinuum light source to provide a wide spectral wavelength range from visible to near IR. The source design was based on coupling light from a femtosecond laser in a photonic crystal fiber designed for high nonlinearity. The output light was efficiently coupled into the bi-tapered fiber sensor and good signal to noise was achieved across the wavelength region. The bi-tapered fiber starts and ends with a single mode fiber in the waist region there are many modes with different propagation constants that couple to the environment outside the fiber. The signals have a strong periodic component as the wavelength is scanned; we exploit the periodicity in the signal using a discrete Fourier transform analysis to correlate signal phase changes with the refractive index changes in the local environment. For small index changes we also measure a strong correlation with the dominant Fourier amplitude component. Our experiments show that our phase-based signal processing technique works well at shorter wavelengths and we extract a new feature, the Fourier amplitude, to measure the refractive index difference. We conducted experiments using aqueous med (open full item for complete abstract)

Master of Science, The Ohio State University, 2017, Mechanical Engineering

Fiber Bragg Grating (FBG) sensorsare optical fibers that detect in-situ strain through deviation of a reflected wavelength of light to detect in-situ strain. These sensors are immune to electromagnetic interference, and the inclusion of multiple FBGs on the same fiber allows for a seamlessly integrated sensing network. FBGs are attractive for embedded sensing in aerospace applications due to their small noninvasive size and prospect of constant, real-time nondestructive evaluation. FBGs are typically used in composite laminate type applications due to difficulties in building them into metallic structures. Additive manufacturing, also referred to as 3D printing, can allow for the inclusion of sensors inside of structural entities by the building of material around the sensor to be embedded. In this study, FBG sensors are embedded into aluminum 6061 via ultrasonic additive manufacturing (UAM), a rapid prototyping process that uses high power ultrasonic vibrations to weld similar and dissimilar metal foils together. UAM was chosen due to the desire to embed FBG sensors at low temperatures, a requirement that excludes other additive processes such as selective laser sintering or fusion deposition modeling. This study demonstrated the feasibility of embedding FBGs in aluminum 6061 via UAM. Further, the sensors were characterized in terms of birefringence losses, post embedding strain shifts, consolidation quality, and strain sensing performance. Sensors embedded into an ASTM test piece were compared against an exterior surface mounted foil strain gage at both room and elevated temperatures using cyclic tensile tests. The effects of metal embedment at temperatures above the melting point of the protective coating (160 degrees Celsius) of the FBG sensors were explored, and the hermetic sealing of the fiber within the metal matrix was used to eplain the coating survival. In-situ FBG sensors were also used to monitor the UAM process itself. Lastly, an example app (open full item for complete abstract)

Doctor of Philosophy, Miami University, 2016, Biology

The ocular lens is an excellent model to study cell signaling, cell survival and cell differentiation. The lens is comprised of only two cell types: proliferative lens epithelial cells and terminally differentiated lens fiber cells. The lens fiber differentiation process involves specific changes in gene expression between the two cell types. However, a comprehensive understanding of gene expression changes during lens fiber differentiation remains incomplete. Furthermore, despite the wealth of knowledge of transcription factors involved in lens cell proliferation, survival and lens fiber differentiation, little information exists about the role of DNA methylation and miRNAs in these processes. This study presents the first application of RNA-seq to provide a comprehensive view of both the relative abundance and differential expression of mRNAs and long intergenic non-coding RNAs from lens epithelial cells and lens fiber cells. We also investigated the role of DNA methylation in lens development. We found that while Dnmt1 inactivation at the lens placode stage led to lens DNA hypomethylation and severe lens epithelial apoptosis, lens fiber cell differentiation remained largely unaffected. The simultaneous deletion of phosphatase and tensin homolog (Pten) elevated the level of phosphorylated AKT and rescued many of the morphological defects and cell death in DNMT1- deficient lenses. With a different Cre driver (MLR10) we demonstrated that a small number of lens epithelial cells escaped Dnmt1-deletion and over-proliferated to compensate for the loss of Dnmt1-deleted cells, suggesting that lens epithelium possess a substantial capacity for self- renewal. Inactivation of both Dnmt3a and Dnmt3b by either the Le-Cre or MLR10-Cre transgene did not result in any obvious lens phenotype prior to 10 months of age, indicating that de novo DNA methylation, at least as mediated by both DNMT3A and DNMT3B, is dispensable for normal lens development. Our comparative miRNA-Seq data a (open full item for complete abstract)

Master of Science in Materials Science and Engineering (MSMSE), Wright State University, 2016, Materials Science and Engineering

SiC/SiC ceramic matrix composites (CMCs) with potential applications at =2700°F (1482°C) are of significant interest to the Air Force. The high temperature performance of SiC fibers used within these composites is greatly affected by the presence of amorphous SiOC and free carbon in the fibers. Therefore quantification of this non SiC material in commercially available SiC fibers is extremely important. In this work Hi Nicalon, Hi-Nicalon Type-S, Tyranno-SA3, Cef-NITE, and Sylramic SiC fibers were studied. Changes in mass, grain size, and amorphous content were measured as a function of processing temperature and time. The amorphous material in each fiber was quantified using the Spike-In method in conjunction with Rietveld refinement. Trends in amorphous content were observed, as well as trends in grain size and crystallized fraction. Transmission electron microscopy (TEM) was used to confirm changes in fiber microstructure.

Master of Science (M.S.), University of Dayton, 2016, Mechanical Engineering

3D textile polymer matrix composites (PMC) exhibit geometric and material state variances due to differences in manufacturing processes and a variety of other factors. Developing a more thorough understanding of these strength and damage variations is a vital aspect of generating an accurate predictive model for the material response of a 3D textile PMC. This work entails both experimental and modeling efforts in order to gain a more thorough understanding of how tow level geometric variations relate to damage evolution in a 3D textile PMC. A 3D orthogonal weave textile is imaged utilizing an X-Ray micro-CT to examine the fiber volume fraction and fiber path distributions within the composite. Additionally, damage evolution is observed at different load steps and CT images are utilized for Digital Volume Correlation analysis. Modeling efforts are primarily focused on tow morphology simulations within the software package- Virtual Textile Morphology Suite (VTMS). Damage evolution analysis on the VTMS models are performed using an advanced Regularized eXtended Finite Element Method (RX-FEM) within the Air Force Research Laboratory developed B-Spline Analysis Method (BSAM) program. Local fiber volume fraction variation in the specimens is examined through serially sectioned images obtained using Robo-Met 3D. Fiber volume fraction distributions are compared to VTMS predictions and VTMS predictions are modified to reflect experimental values. The effect of these local fiber volume fraction distributions on damage evolution in the composite are examined through experimentation and modeling efforts.