Epitaxial growth, or the oriented growth of a crystalline monolayer on an ordered substrate, appears in a wide range of systems and applications, from novel device fabrication to freshwater remediation. Despite this, methodical studies of the phenomenon are rare, and the mechanisms governing epitaxial growth are poorly understood. This investigation employs AFM techniques to monitor the epitaxial growth of ion crystal systems at the initial stages of growth. By using systems with well-known physical properties, we are able to relate growth modes to two key parameters, crystal lattice mismatch, Δr/r₀, and affinity between the overgrowth and the substrate ions, ξ. We found wetting growth occurs for systems in which Δr/r₀ is expansive (overgrowth lattice must expand to accommodate substrate) or mildly compressive (overgrowth compresses to accommodate substrate). Additionally, a strong affinity between the substrate and overgrowth ions, in combination with an expansive system, allows for epitaxial growth from undersaturated solutions. We also have observed several instances where the lateral force contrast on the growing film exhibits a strong dependence on the time of exposure to the growth solution and on the driving force for growth (solute concentration). We present results for three epitaxial growth systems in aqueous solutions: CaSO₃ on CaCO₃, PbSO₄ on BaSO₄, and BaSO₃ on BaSO₄. Chemically and topographically identical regions grown at higher concentrations exhibit higher friction than regions grown at lower concentrations. These observations suggest that epitaxial growth occurs by a fast condensation step incorporating a high defect density.

This paper investigates the development, design and modeling of a human spine-inspired seismic lateral force resisting system. The overall goal is to create a design for a lateral force resisting system that reflects human spine behavior that is both practical and effective. The first phase of this project involved a literature review of the human spine and rocking structural systems. The goal of this phase was to identify concepts from the spine that could be transferred to a lateral force resisting system. The second phase involved creating a 3-dimensional model of the lumbar region of the spine in SAP2000 and using it to examine concepts that could be transferred to a lateral force resisting system. The third phase consisted of creating possible system designs using concepts and principles identified through phases one and two and identifying a final system design. The last phase involved modeling the final lateral force resisting system design in SAP2000, validating the model and testing the design's effectiveness. This paper shows that this system is a viable option to prevent permanent structural damage in buildings during a seismic event. / Master of Science

Plasmonic nanostructures provide unique opportunities to improve the detection limits of chiroptical spectroscopies by enhancing chiral light-matter interactions. The most significant of such interaction occur in ultraviolet (UV) range of the electromagnetic spectrum that remains challenging to access by conventional localized plasmon resonance based sensors. Although Surface Plasmon Polaritons (SPPs) on noble metal films can sustain resonances in the desired spectral range, their transverse magnetic nature has been an obstacle for enhancing chiroptical effects. We demonstrate, both analytically and numerically, that SPPs excited by near-field sources can exhibit rich and non-trivial chiral characteristics. In particular, we show that the excitation of SPPs by a chiral source not only results in a locally enhanced optical chirality but also achieves manifold enhancement of net optical chirality. Our finding that SPPs facilitate a plasmonic enhancement of optical chirality in the UV part of the spectrum is of great interest in chiral bio-sensing. Next we focus on the new concepts of transverse spin angular momentum and Belinfante spin momentum of evanescent waves, which have recently drawn considerable attention. We investigate these novel physical properties of electromagnetic fields in the context of chiral surface plasmon polaritons. We demonstrate, both analytically and numerically, that locally excited surface plasmon polaritons possess transverse Spin angular momentum and Belinfante momentum with rich and non-trivial characteristics. We also show that the transverse spin angular momentum of locally excited surface plasmon polaritons leads to the emergence of transverse chiral forces in opposite directions for chiral objects of different handedness. The magnitude of such a transverse force is comparable to the optical gradient force and scattering forces. This finding may pave the way for realization of optical separation of chiral biomolecules

This thesis reflects two advances in atomic force microscopy. The first half is a new lateral force calibration procedure, which, in contrast to existing procedures, is independent of sample and cantilever shape, simple, direct, and quick. The second half is a high-throughput method for processing, fitting, and analyzing force curves taken on Pseudomonas aeruginosa bacteria in an effort to inspire better care for statistics and increase measurement precision.

Equivalent Lateral Force Method (ELF) and Response Spectrum Analysis (RSA) are the two most popular methods of seismic design of structures. This study aims to present a comparative study of the two methods using hand-calculated approach as well as computer analysis according to ASCE 7-10 Standards. The two methods have been compared in terms of base shear and story forces by analyzing various models for different number of stories and different support conditions. It was found that ELF gives conservative results in comparison to RSA. This result was more obvious in case of four-story frames. Hence, for structures of increased elevation, the analysis from ELF may not be sufficient.

Friction between nanoscale objects has been a subject of great interest and intense research effort for the last two decades. However, the vast majority of the work done in this area has focused upon the sliding friction between two rigid, atomically smooth surfaces. Thus the parameter most explored has been the corrugation in the atomic potentials and how this affects the force required to slide one object across another. In truth, many nanoscale objects whose translation force is of practical interest are more spherical in nature. We hypothesize that the factors that determine the translation force will be related, not only to the interfacial adhesion, but also to the mechanical properties of the translating object and its underlying surface. The dependence on these quantities of the friction is not known. In this dissertation we have utilized Atomic Force Microscopy and Force Spectroscopy to study the tribological properties of submicron scale polymeric particles to explore how the friction between these submicron spherical objects translating over planar substrates is related to interfacial energy and the mechanical properties for these particles. A technique for modifying the mechanical properties was developed and used to provide a set of samples over which we had control of the elastic modulus without corresponding changes in the chemical bonds. The modified mechanical properties were tested against the Flory-Rehner theory. Lateral force microscopy was used to measure the force required to translate asymmetric, nanoscale particles of controlled size, surface chemistry and moduli. Silicon wafers were used as the substrate. The effects of work of adhesion, elastic modulus of polystyrene microspheres, and contact radius between particle and substrate have been studied for the different modes of particle translation under an external force.

Metal buildings account for over 40% of low-rise construction in the US. Despite this, predictive fundamental period equations that were obtained empirically for mid-rise construction are used in seismic design. Analytical modeling of metal building frames implied that these equations significantly underpredict the period, which led to the development of a new predictive equation. However, experimental tests showed that these models may overestimate the measured period. In this work, further tests were carried out in order to single out possible causes. Buildings were tested during different stages of construction to evaluate how non-structural elements could affect the behavior. Both planar and three-dimensional models were developed to determine if design assumptions are accurate for the purpose of estimating the period. The results from tests showed that, unlike other single-story buildings, non-structural components seem to have negligible effect on the structural behavior. However, several buildings seemed to exhibit signs of fixed conditions at the column base. This assertion was corroborated by updating the analytical models. The two modeling approaches showed good agreement with each other as well, validating the use of planar models to predict the period. Finally, new predictive equations are proposed that take into account the type of cladding, as it was found to be an important variable not previously considered. However, low mass participation ratios coupled with the stiffness provided by the secondary framing put the use of the equivalent lateral force procedure into question. / Master of Science / When designing buildings for earthquake loads it is necessary to know their dynamic properties in order to define the equivalent forces that must be applied. Building codes provide predictive equations that were obtained empirically for typical mid-rise construction. Metal buildings do not fall within the range of buildings tested for their development, and so a new equation was proposed for them based on a database of planar models. However, previous tests implied that this equation was predicting larger periods than those obtained experimentally. In this work, further tests were carried out during different stages of construction to evaluate how non-structural elements could affect the behavior. Models were also created for each building in order to determine if the approach used to develop the metal building database was adequate for estimating the period. The results from tests showed that, unlike other single-story buildings, non-structural components seem to have negligible effect on the structural behavior, and the modeling assumptions within the database were validated. Further analysis showed that the type of cladding (concrete or metal sheeting) had a large influence on the properties of metal buildings. In consequence, a new set of predictive equations is proposed that takes this into account.

In the first part of this study, frictional and normal forces in aqueous solutions were measured between a glass particle and oligopeptide films grafted from a glass plate. Homopeptide molecules consisting of 11 monomers of different amino acids were each "grafted from" an oxidized silicon wafer using microwave-assisted solid phase peptide synthesis. Oligopeptides increased the magnitude of friction compared to a bare hydrophilic silicon wafer. Friction was a strong function of the nature of the monomer unit and was lower for hydrophilic films. There was a strong adhesion and therefore friction between surfaces of opposite charges. Changes in adhesion and friction depended on the hydrophobicity and electrostatic forces: hydrophobic films and oppositely charged films produced high friction, whereas hydrophilic and like-charges produced low friction. Friction was lower in phosphate buffered saline than in pure water due to the screening of the double layer attraction for oppositely charged surfaces and additional lubrication by hydrated salt ions. We also investigated antimicrobial action of poly (allyl amine) (PA) when covalently bonded to glass. Glass surfaces were prepared by a two-step procedure where the glass was first functionalized with epoxide groups using 3-glycidoxypropyltrimethoxy silane (GOPTS) and then exposed to PA to bind via reaction of a fraction of its amine groups. Antibacterial properties of these coatings were evaluated by spraying aqueous suspensions of bacteria on the functionalized glass slides, incubating them under agar, and counting the number of surviving cell colonies. The PA film displayed strong anti-microbial activity against both Gram-positive and Gram-negative bacteria. Films that were prepared by allowing the PA to self assemble onto the solid via electrostatic interactions were ineffective antimicrobials. Such films had an insufficient positive charge and did not extend far from the solid. Thus we found that antimicrobial activity was correlated with a combination of the ability of the polymer chain to extend into solution and a positive surface potential. / Ph. D.

Master of Science / Department of Architectural Engineering / Kimberly Waggle Kramer / Braced frames are a common seismic lateral force resisting system used in steel structures. Ordinary concentric braced frames (OCBFs) and special concentric braced frames (SCBFs) are two major types of frames. Brace layouts vary for both OCBFs and SCBFs. This report examines the inverted-V brace layout which is one common arrangement. OCBFs are designed to remain in the elastic range during the design extreme seismic event. As a result, OCBFs have relatively few special requirements for design. SCBFs are designed to enter the inelastic range during the design extreme seismic event while remaining elastic during minor earthquakes and in resisting wind loads. To achieve this, SCBFs must meet a variety of stringent design and detailing requirements to ensure robust seismic performance characterized by high levels of ductility. The design of steel seismic force resisting systems must comply with the requirements of the American Institute of Steel Construction’s (AISC) Seismic Provisions for Structural Steel Buildings. Seismic loads are determined in accordance with the American Society of Engineers Minimum Design Loads for Buildings and Other Structures. Seismic loads are very difficult to predict as is the behavior of structures during a large seismic event. However, a properly designed and detailed steel structure can safely withstand the effects of an earthquake. This report examines a two-story office building in a region of moderately high seismic activity. The building is designed using OCBFs and SCBFs. This report presents the designs of both systems including the calculation of loads, the design of frame members, and the design and detailing of the connections. The purpose of this report is to examine the differences in design and detailing for the two braced frame systems.

Master of Science / Department of Architectural Engineering / Kimberly Waggle Kramer / Braced frames are a common seismic lateral force resisting system used in steel structure. Eccentrically braced frames (EBFs) are a relatively new lateral force resisting system developed to resist seismic events in a predictable manner. Properly designed and detailed EBFs behave in a ductile manner through shear or flexural yielding of a link element. The link is created through brace eccentricity with either the column centerlines or the beam midpoint. The ductile yielding produces wide, balanced hysteresis loops, indicating excellent energy dissipation, which is required for high seismic events. This report explains the underlying research of the behavior of EBFs and details the seismic specification used in design. The design process of an EBF is described in detail with design calculations for a 2- and 5-story structure. The design process is from the AISC 341-10 Seismic Provisions for Structural Steel Buildings with the gravity and lateral loads calculated according to ASCE 7-10 Minimum Design Loads for Buildings and Other Structures. Seismic loads are calculated using the Equivalent Lateral Force Procedure. The final member sizes of the 2-story EBF are compared to the results of a study by Eric Grusenmeyer (2012). The results of the parametric study are discussed in detail.