Doctor of Philosophy, The Ohio State University, 2021, Chemistry

Mass spectrometry (MS) has evolved into one of the most important methods for the characterization and detection of biological and chemical molecules. The development of soft ionization methods such as electrospray ionization (ESI) and matrix-assisted laser desorption ionization (MALDI) have made these applications possible. However, the requirement for extensive sample preparation has limited analyses that require complex sampling. These limitations in the analysis process have led to the expansion of ambient ionization mass spectrometry. This dissertation describes the development and optimization of novel ambient ionization methods that rely on porous/cellulose-based substrates such as thread and paper. Chapter 2 depicts a thread spray ionization method with forensic serology applications. Thread spray ionization enables direct analysis of trace levels of blood on textiles without extensive sample preparation reducing backlog seen in many criminal laboratories. This dissertation describes the successful implementation of thread spray as a rapid presumptive method of blood-stained textiles through the identification of heme in whole blood. Thread spray ionization is also a suitable confirmatory method through the direct differentiation of human, canine, and horse blood by determining the species' specific phospholipid lipid profiles. Chapter 3 outlines thread spray ionization as a rapid in situ method for detection of agrochemicals in complex matrices such as surface water and foodstuff. Determination of pesticide residues in a wide variety of matrices is an ongoing challenge due to small quantities of analytes and substantial amounts of interfering substances that can be coextracted with the analytes. In this chapter, we detail the use of a nano-thread spray mass spectrometry approach that utilizes a nano spray like emitter, as opposed to the traditional thread spray ionization apparatus, to enhance on-thread separation of agrochemicals and environmental matrice (open full item for complete abstract)

Committee: Abraham Badu-Tawiah (Advisor) Subjects: Chemistry

Doctor of Philosophy, The Ohio State University, 2019, Chemistry

Accuracy and rapid analysis of complex microsamples are significant and challenging tasks in translational research. Traditionally, nano-electrospray ionization (nESI) is a widely used method of choice to analyze complex mixtures with small volumes by mass spectrometry (MS). However, this technique performs well only for polar analytes, unable to analyze gas phase molecules and have some other substantial obstacles, including matrix effect and Joule heating of samples. This thesis is mainly focused on designing and developing new contained ion sources to overcome the limitations of conventional electrospray ionization (ESI) by combination/containing several components to create hybrid ionization devices capable of on-line sample preparation, separation and in-situ analyte modification via gas-phase reactions involving the derived ions. In Chapter 2, a new quantitative Contained ESI method is described that employs a movable ESI emitter to control the reactivity of charged micro-droplets by varying their time of exposure with inorganic acid vapor. The technique allows elimination of ion suppression effects due to the presence of different surface active compounds that co-elute with the analyte. For mixtures, Contained ESI mass spectrometric analysis produces relative ion intensities that reflect the actual concentrations of analytes in solution. The mechanism for this effect has been elucidated and ascribed to the generation of fine initial droplets in the presence of high abundance of protons. Together these two factors eliminate competition for charge and space during an ion formation. Instances of analytes tested include steroids, phospholipids, phosphopeptides and sialylated glycans. At least one order of magnitude improvement in detection limits, sensitivity, and accuracy of detection was achieved when compared to conventional electrospray. In Chapter 3, we have described a new and versatile dual non-contact nESI / nano-atmospheric pressure chemical ionizatio (open full item for complete abstract)

Committee: Abraham Badu-Tawiah (Advisor); Vicki Wysocki (Committee Member); Anne Co (Committee Member) Subjects: Analytical Chemistry; Biochemistry; Chemistry; Pharmaceuticals

Doctor of Philosophy, The Ohio State University, 2016, Mechanical Engineering

The focus of this scholarly research is on the nonlinear stiffness and interfacial friction characterization of coned disk springs which belong to a family of diaphragm springs. Prior researchers had analytically developed the coned disk spring's load-deflection relationship under over simplified assumptions with minimal experimental validation while ignoring the nonlinear stiffness characteristics. To overcome such deficiencies, this dissertation proposes new quasi-static and dynamic experiments to measure the disk spring's load-deflection relationship in the presence of edge friction. The scope is, however, limited to the square-edged coned disk spring element and its primary parallel stack configuration and two primary series stack configurations. For these example cases, refined nonlinear stiffness and damping models are proposed over the full range of displacements under several interfacial edge friction conditions, and distinct regimes are defined. First, a quasi-static experiment is developed to measure the midrange nonlinear load-deflection characteristics under four principal interfacial edge configurations — two symmetric and two asymmetric. The experiment allows direct quantification of the friction contribution at each edge. Accordingly, a refined analytical single disk spring load-deflection model, which allows the natural elasto-kinematic behavior of the disk spring to assert itself by relaxing prior limiting geometric assumptions, is developed to clarify the effect of edge friction on the load-deflection relationship including hysteresis. Next, full-range displacement-dependent stiffness characteristics are determined via measured parameters for all example configurations; nine distinct physically motivated regimes are then defined. Measured hysteretic force difference characteristics are clarified as well. A continuously nonlinear stiffness expression is analytically derived and then used as a basis for the development of a novel semi-analytical p (open full item for complete abstract)

Committee: Rajendra Singh PhD (Advisor); Brian Harper PhD (Committee Member); Shaurya Prakash PhD (Committee Member); Jason T. Dreyer PhD (Committee Member) Subjects: Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2012, Mechanical Engineering

This study examines a low frequency, friction induced brake vibration problem (often known as the judder phenomenon in automobiles) that is excited by the surface distortions in the rotor. A nonlinear brake system is analyzed using experimental, analytical, and numerical approaches, though the main goal is to find new or improved analytical solutions for the speed-dependent characteristics of the governing system. Initially, a two degree of freedom torsional model of the brake system with clearance nonlinearity is proposed, where the main excitation is the multiple order frictional torque, as related to the rotor profile imperfections. The nonlinear model is first simplified as a quasi-linear model by ignoring the clearance, and closed form solutions (for a decelerating system) are obtained with and without the viscous damping element. New solutions match well with the numerical integration and numerical convolution results. The nonlinear model is then numerically solved using two different methods to calculate the speed-dependent friction induced torques. The discontinuous curves are first approximated with smoothening functions, and then event detection and location algorithms are utilized. Both approaches compare well unless the discontinuous functions are poorly smoothed. Second, quasi-linear and nonlinear models are utilized to calculate the envelopes of the response amplitudes over a range of applicable speeds. The envelope functions are first derived from the closed form analytical solutions of the quasi-linear model. In addition, a Hilbert transform based envelope curve prediction method is proposed and applied to both quasi-linear and nonlinear models. Envelope curves are calculated for single and multiple order rotor surface excitations, and the estimations match well with analytical and numerical solutions. Furthermore, the multi-term harmonic balance method is successfully adapted to construct the order domain solutions for the nonlinear model. The arc-l (open full item for complete abstract)

Committee: Rajendra Singh PhD (Advisor); Ahmet Selamet PhD (Committee Member); Ahmet Kahraman PhD (Committee Member); Manoj Srinivasan PhD (Committee Member); Jason Dreyer PhD (Committee Member) Subjects: Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2005, Textiles and Clothing

The research goals reported in this dissertation were twofold: to develop a protocol using non-destructive or minimally destructive methods to classify the colorants that were used prehistorically as inorganic/organic and pigment/dye, and to apply the protocol to selected textiles from Seip archaeological site, Ohio. The principle guiding the research was to adapt and sequence the analytical methods permitting the use of the smallest possible sample size which could still yield the most information. Through non-destructive forensic photography prior to any other analysis evidence for the chemical differences on the archaeological textiles resulting from the prehistoric colorant applications were revealed, which facilitated selective and purposive micro-sampling that maximized critical data acquisition while minimizing potential destruction of the artifact. Pretests on replicated materials were conducted first to assess feasibility and efficacy of selected analytical methods: photography in different lighting conditions (simulated daylight, infrared and ultraviolet), optical and scanning electron microscopy with energy dispersive X-ray analysis (EDS), and inductively coupled mass spectrometry (ICP-MS) for elemental analysis. Differences in chemical signatures on painted replicas, otherwise invisible, were confirmed by forensic photography. While working with replicas, limitations of the analytical methods were discovered and addressed to adapt the methods for the use on archaeological materials. A specific sequence of modified methods, constituting the ideal protocol, was then applied to selected prehistoric textiles. Based on the visual examination, eleven textiles from the Hopewellian Seip Mound group were selected and divided into main colored groups: (1) yellow/brown, (2) turquoise/white, and (3) charred. Each of these groups was sampled based on the results of the photography; the turquoise/white group showed patterns otherwise invisible. Optical microscopy illu (open full item for complete abstract)

Committee: Kathryn Jakes (Advisor) Subjects:

Master of Science (MS), Ohio University, 1990, Mechanical Engineering (Engineering)

This work deals with the plastic deformation and temperature analysis of the coextrusion process known as canned extrusion. Analytical techniques such as the upperbound method, slab method, lumped parameter method, and the finite element program, ALPID, were used to analyze the coextrusion of IN100 in a 304 stainless steel can. The effects of can thickness, can flow stress, core flow stress, and heat transfer parameters on load, material flow, states of stress, strain, and strain rate were investigated and correlated with experimental extrusions. The experimental extrusions demonstrated the effect of average effective strain on the microstructure of cast IN100 and the effect of canning on surface defects. The occurence of the fir tree surface defect correlates very well with the transition from compressive to tensile axial stress. This defect can be avoided in brittle materials, such as cast IN100, by placing the brittle material in a can of ductile material with an approximately equal flow stress. The addition of an insulating material at the can/core interface would be more effective than glass lubricants at the die/billet interface in reducing heat loss. An average effective strain of 1.8 transformed the as-cast IN100 grain structure to a fine recrystallized grain structure while a strain of 1.2 did not. Finally, this investigation has combined analytical modeling with experimentation to provide a quantitative understanding of the state of stress, strain, strain rate, and temperature during the coextrusion of canned billets.

Committee: Kenneth Halliday (Advisor) Subjects: Engineering, Mechanical