Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
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Item Characterization of host-pathogen interactions during early Staphylococcus aureus biofilm formation on surfaces(Montana State University - Bozeman, College of Agriculture, 2022) Pettygrove, Brian Alexander; Chairperson, Graduate Committee: Philip S. Stewart; This is a manuscript style paper that includes co-authored chapters.Implanted biomaterials such as orthopedic screws, prosthetic joints, pacemakers, and catheters are essential components of modern medicine. Unfortunately, implanted foreign bodies are susceptible to biofilm infection, leading to a persistent and difficult to treat disease state. Biofilm infections readily tolerate clearance from the immune system, however much of our understanding of the mechanisms governing persistence are formulated around the biofilm state during advanced infection. By comparison we have a poor understanding of the early stages of infection. Specifically, how contaminating organisms initially evade host immune defenses and establish a robust infection remains ill-defined. In this work, we interrogated interactions between Staphylococcus aureus (S. aureus), a frequent culprit in biomaterial infections, and early contributors to host immunity. Using in vitro time-lapse microscopy, we observed that human neutrophils readily phagocytose and kill single cells or small clusters of S. aureus cells that are attached to a surface. S. aureus cells that go undiscovered during the initial stages of neutrophil surveillance form biofilm aggregates that rapidly gain tolerance to neutrophil killing. In vivo models of implant infection demonstrated that surface adherent bacteria can evade discovery due to delayed or heterogeneous neutrophil recruitment to the surface. Biofilm aggregate formation was impaired in a strain deficient in the two-component gene regulatory system SaeR/S and the resulting cells were highly susceptible to neutrophil killing. Inhibition of aggregation was dependent on serum complement proteins C3 and factor B, suggesting that SaeR/S regulated factors actively inhibit host complement to facilitate aggregation. Taken together, these data suggest that the formation of immune-tolerant biofilm aggregates may contribute to chronic device related infections by protecting bacteria from phagocyte killing. These studies provide vital insight into the host pathogen interactions on contaminated biomaterial surfaces and highlight early events that may determine infection outcome.Item Immersions of surfaces(Montana State University - Bozeman, College of Letters & Science, 2022) Howard, Adam Jacob; Co-chairs, Graduate Committee: David Ayala and Ryan GradyTo determine the existence of a regular homotopy between two immersions, f, g : M --> N, is equivalent to showing that they lie in the same path component of the space Imm(M, N). We identify the connected components, pi 0 Imm(W g, M), of the space of immersions from a closed, orientable, genus-g surface W g into a parallelizable manifold M. We also identify the higher homotopy groups of Imm(W g, M) in terms of the homotopy groups of M and the Stiefel space V 2 (n). We then use this work to characterize immersions from tori into hyperbolic manifolds as self covers of a tubular neighborhood of a closed geodesic up to regular homotopy. Finally, we identify the homotopy-type of the space of framed immersions from the torus to itself.Item The role of adsorbed phase volume on the thermodynamics of supercritical methane adsorption on microporous carbon(Montana State University - Bozeman, College of Engineering, 2019) Remington, Emily Lynn; Chairperson, Graduate Committee: Sarah L. Codd; Nicholas P. Stadie (co-chair)Experimental determination of the isosteric heat of adsorption at the fluidsolid interface is an important undertaking in the chemical sciences since this fundamental thermodynamic quantity is closely related to the binding energy of the adsorbate on the adsorbent surface. The usual methods employed to calculate the isosteric heat from measured gas adsorption equilibria, however, are unsuited to the treatment of adsorption under a high-pressure adsorptive fluid (where the difference in molar volume between the two phases becomes small and depends significantly on that of the adsorbed phase). Herein we employ a methodological approach to the thermodynamic analysis of adsorption up to high pressures in the supercritical regime, with a specific focus on methane adsorption on microporous carbonaceous materials at T/T c between 1.25-2.75 and P/P c up to 2. The aim is to achieve a meritorious description of the thermodynamics of the adsorbed phase with as few independent parameters as possible. We compare several simple approaches to estimating the molar volume of the adsorbed phase, and demonstrate that among the several well-known sources of error involved in the isosteric approach, that attributed to molar volume estimations is not itself prohibitive to achieving meritorious results. We contrast the isosteric approach with that of the so-called 'isoexcess' methodology, and thereby shed new insights into the key role of the finite adsorbed phase volume in assessments of adsorption thermodynamics.Item Designing pattern formation through anisotropy(Montana State University - Bozeman, College of Letters & Science, 2019) Gaussoin, Anthony Danwayne; Chairperson, Graduate Committee: Scott McCallaWhen governed by appropriate potentials, systems of particles interacting pairwise in three dimensions self assemble into diverse patterns near the surface of a sphere. The resulting structure of these minimal energy states can be altered through anisotropic effects. This leads to the inverse problem of finding anisotropic potentials that produce specific targeted equilibrium structures. To study this problem, continuous versions of the discrete particle interaction equations are employed so that a leading order approximation can be obtained. Linear stability is then determined through a Fourier type analysis in terms of spherical harmonics. This allows us to solve the linearized inverse problem: for a targeted equilibrium structure, where the particles congregate along a finite set of spherical harmonics, construct an anisotropic potential that induces the same finite set of linear instabilities. Several examples of anisotropic potentials that cause known linear instabilities are presented. The resulting minimal energy configurations are approximated through a gradient descent of the discrete particle energy. These numerical experiments corroborate that the linear instabilities can be used to predict the minimal energy structure in the full nonlinear dynamics. Solving the linearized inverse problem yields a clear path to designing pattern formation through anisotropic effects.Item The synthesis of N-acetyllactosamine functionalized dendrimers, and the functionalization of silica surfaces using tunable dendrons and beta-cyclodextrins(Montana State University - Bozeman, College of Letters & Science, 2017) Ennist, Jessica Helen; Chairperson, Graduate Committee: Mary J. Cloninger; Mary J. Cloninger was a co-author of the article, 'The synthesis of N-acetyllactosamine functionalized dendrimers and their role in galectin-3 mediated cancer cellular aggregation studies' which is contained within this thesis.; Eric A. Gobrogge, Kristian H. Schlick, Robert A. Walker and Mary J. Cloninger were co-authors of the article, 'Cyclodextrin-functionalized chromatographic materials tailored for reversible adsorbtion' in the journal 'ACS applied materials and interfaces' which is contained within this thesis.Galectin-3 is beta-galactoside binding protein which is found in many healthy cells. In cancer, the galectin-3/tumor-associated Thomsen-Friedenreich antigen (TF antigen) interaction has been implicated in heterotypic and homotypic cellular adhesion and apoptotic signaling pathways. However, a stronger mechanistic understanding of the role of galectin-3 in these processes is needed. N-acetyllactosamine (LacNAc) is a non-native ligand for galectin-3 which binds with comparable affinity to the TF antigen and therefore an important ligand to study galectin-3 mediated processes. To study galectin-3 mediated homotypic cellular aggregation, four generations of polyamidoamine (PAMAM) dendrimers were functionalized with N-acetyllactosamine using a four-step chemoenzymatic route. The enzymatic step controlled the regiochemistry of the galactose addition to N-acetylglucosamine functionalized dendrimers using a recombinant beta-1,4-Galactosyltransferase-/UDP-4'-Gal Epimerase Fusion Protein (lgtB-galE). Homotypic cellular aggregation, which is promoted by the presence of galectin-3 as it binds to glycosides at the cell surface, was studied using HT-1080 fibrosarcoma, A549 lung, and DU-145 prostate cancer cell lines. In the presence of small LacNAc functionalized PAMAM dendrimers, galectin-3 induced cancer cellular aggregation was inhibited. However, the larger glycodendrimers induced homotypic cellular aggregation. Additionally, novel poly(aryl ether) dendronized silica surfaces designed for reversible adsorbtion of targeted analytes were synthesized, and characterization using X-ray Photoelectron Spectroscopy (XPS) was performed. Using a Cu(I) mediated cycloaddition 'click' reaction, beta-cyclodextrin was appended to dendronized surfaces via triazole formation and also to a non-dendronized surface for comparison purposes. First generation G(1) dendrons have more than 6 times greater capacity to adsorb targeted analytes than slides functionalized with monomeric beta-cyclodextrin and are 2 times greater than slides functionalized with larger generation dendrons. This study reported beta-cyclodextrin functionalized surfaces can undergo a triggered release of the adsorbent, but otherwise retained the targeted analyte through multiple aqueous washes. Therefore, a new generation of G(1) dendronized surfaces capable of reversible adsorption were developed by heterogeneously appending sulfonic acid/pyridine end-groups. Auger Electron Spectroscopy (AES) was used to quantify the ratio of groups installed. Furthermore, G(1) dendronized surfaces were functionalized homogenously with sulfonic acid and pyridine for comparison and with chiral amino acids for chiral recognition studies.Item The influence of solar radiation in snow on near surface energy balance in complex topography(Montana State University - Bozeman, College of Engineering, 2015) Curley, Patricia Glatz; Chairperson, Graduate Committee: Edward E. AdamsOnce snow reaches the ground it begins to metamorphose. It may thermodynamically metamorphose into a weak layer, which could lead to slab avalanches. The effect of local weather, topography and snow depth on this process can be estimated with a first principle one-dimensional energy balance equation in conjunction with a mesh topographic model. To do this, the commercially available software RadThermRT (RTRT) was used. This work focused on the effect of solar radiation on surface and near surface temperatures as well as the effect of varying the resolution of the topographic model. Three main components were completed. A solar radiation attenuation coefficient was developed based on wavelength, snow grain size, and snow density from published literature. Then this code was used to calculate results from twelve hour radiation recrystallization experiments carried out in a cold lab with homogenous snow. Finally, conditions for metamorphic events were calculated and qualitatively affirmed in the field at the Yellowstone Club ski area. This work demonstrates that solar radiation has a significant effect on the surface temperature as well as temperature at depth, and weak layer metamorphic events can be modeled. Based on RTRT calculations with 100 kg/m 3 density snow, shortwave radiation increased the temperature at the surface by approximately 5°C and at 2.5 centimeters below the surface by 9°C. During the 2013/14 and 2014/15 seasons, diurnal weather data was collected at the Yellowstone Club ski area, and events around the mountain were recorded with the help of the Yellowstone Club ski patrol and thermal imaging. For radiation recrystallization events, strong positive-knee-shaped gradients were successfully modeled on congruous slopes. RTRT and measured results agreed within 2°C. Spring events were also calculated and measured but there were some false positives. In the winter, spatial variation over the mountain was greater than in the spring where snow temperatures were ubiquitously high. Overall, this work is useful for modeling snow surface and depth temperatures to project the occurrence of weak layer metamorphic events. Going forward from this work, projecting longevity of weak layers and including a layer history of the snow would further improve the model.Item Surface(Montana State University - Bozeman, College of Arts & Architecture, 2001) Maki, SarahMy work is about revealing beauty in the hidden, subtle, and inauspicious details found around us. I want to call attention to beauty found in the quiet, temporal familiarities of the physical world where there exists a transition between material and nonexistence. The main vehicle for this disclosure is casting process in which translucent materials are used to lift impressions from surfaces such as the studio floor or sheets of plastic. This process reveals countless natural occurrences, varying form cracks and wrinkles to dirt and chipped paint. The combination of these subtle incidents is the focal point of my work My attention to surface draws the viewer into the interior of each piece, dissolving the outer membrane and revealing layers of hidden irregularities. Each work is a record of used and misuse - a temporal expression of beauty created by the collective effects of time, human treatment, and my own hand.Item 3 walls(Montana State University - Bozeman, College of Arts & Architecture, 2002) Howe, MirandaDesigns and patterns are elemental components in my work. They are not only visual end results, but are very important aspects in my own creative process. In making thousands upon thousands of tiles, stacking, arranging, and grouping them in different stages all around me, I become immersed in the process. The repetition of doing one things over and over again until it becomes a navigational memory for the muscles, allows freedom for the mind to traverse different terrain. Like portions of frescoes crumbing, or paint peeling to reveal what is underneath, I only give fragments of information before one surface stops and another begins. Compelled to cut my tiles into smaller and smaller units, I weave together a tighter, more complex networks of layered information. Organic and invented pattern coincide. Burnt earth, quilting fabric, dried riverbeds, brick streets, ancient ruins, fissures and intrusions are all used to celebrate pattern.Item Structural and chemisorption properties of metallic surfaces and metallic overlayers(Montana State University - Bozeman, College of Letters & Science, 1990) Xu, Mingde