Scholarship & Research
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Item A thermodynamic and optical assessment of soluble carbon particulate effects on lipid film structure and organization(Montana State University - Bozeman, College of Letters & Science, 2022) Shaikh, Nida; Chairperson, Graduate Committee: Robert Walker; This is a manuscript style paper that includes co-authored chapters.Research described in this thesis investigates the effects of carbonaceous particulate matter on model biological membrane structure, organization, and function. Although the harmful impacts of black carbon are well-documented, researchers lack the chemically-specific, mechanistic information necessary for understanding how black carbon aerosols affect lung surfactant spreading and compression. Surface specific optical spectroscopy methods together with complementary thermodynamic methods are used to measure how carbon nanoparticles, a model for black carbon aerosols that are a component of particulate matter (PM 2.5 ), change average lipid conformation, orientation, thickness, and compressibility in monolayers, and how these changes affect overall membrane organization. Addressing these questions requires a suite of independent, but complementary, experimental techniques including Langmuir trough and surface tension measurements, surface specific nonlinear optical spectroscopy measurements including both second harmonic generation and sum frequency generation, and spectroscopic ellipsometry measurements. Work presented in this thesis discusses cooperative adsorption as a possible mechanism to explain the interactions between DPPC monolayers and PHFs at biologically-relevant aqueous - air interfaces. The experiments forthcoming represent a detailed investigation of 1) the mechanism(s) responsible for accumulation of carbon particulates at the aqueous/monolayer/air interface present in the lungs, and 2) how specific thermodynamic behavior and optical properties (i.e. structure, composition, membrane integrity, orientation, thickness, and organization) at the aqueous/monolayer/air interface change with the inclusion of non-biological, nano-sized materials. Motivating this work is a need to develop a predictive understanding of black carbon - lung surfactant interactions and how non-biological, nano-sized materials impact membrane structure and function.Item Aerosol stability of severe acute respiratory syndrome Coronavirus 2 (SARS-CoV-2)(Montana State University - Bozeman, College of Agriculture, 2022) Bushmaker, Trenton John; Chairperson, Graduate Committee: Raina K. Plowright and Vincent J. Munster (co-chair); Neeltje van Doremalen and Dylan H. Morris were authors and Myndi G. Holbrook, Amandine Gamble, Brandi N. Williamson, Azaibi Tamin, Jennifer L. Harcourt, Natalie J. Thornburg, Susan I. Gerber, James O. Lloyd-Smith, Emmie de Wit and Vincent J. Munster were co-authors of the article, 'Aerosol and surface stability of SARS-CoV-2 as compared with SARS-CoV-1' in the journal 'New England journal of medicine' which is contained within this thesis.; Claude Kwe Yinda and Dylan H. Morris were authors and Myndi G. Holbrook, Amandine Gamble, Danielle Adney, Cara Bushmaker, Neeltje van Doremalen, Raina K. Plowright, James O. Lloyd-Smith and Vincent J. Munster were co-authors of the article, 'Comparative aerosol stability of SARS-CoV-2 variants of concern' submitted to the journal 'Emerging infectious diseases - CDC' which is contained within this thesis.The routes of transmission of the zoonotic pathogen severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) have been extensively studied to understand the spread at individual and population levels. Aerosol particles produced by infected individuals and the deposition patterns inhaled are known to affect the virulence of bioaerosol pathogens. Droplet nuclei particles (< 5 microns) aerosols typically deposit within the alveolar spaces of the lungs, whereas droplet (>5 microns) aerosols typically deposit within the nasopharyngeal and tracheobronchial regions of the respiratory tract. A few studies have evaluated pulmonary disease following droplet nuclei size particles of SARS-CoV-2 aerosol inhalation in African green monkeys and golden hamsters, concluding that both models have mild respiratory disease representative of human disease. More importantly, human participants with SARS-CoV-2 infections have been studied to look at the generation of particles during breathing, talking, and singing; the study concluded droplet nuclei particles accounted for 85% of the copies of virus produced and play a significant role in transmission. However, the environmental persistence of the aerosolized droplet nuclei particles, and the likely role of environmental persistence in driving transmission, is unknown for SARS-CoV-2. In these studies, we show the changing aerosol stability of SARS-CoV-2 during the supplanting waves of Variants of Concern (VOC). With the determination of viable viral particles characterized over time, we can make inferences about the role VOC and aerosol transmission have in driving population-level pathogen transmission. A secondary objective of these studies was to characterize the role those evolving mutations have had on viral entry and aerosol durability. Our work suggests that aerosol stability may be important in driving some population-level phenomena (e.g., indoor transmission, including superspreader events) but given the short infected-to-naive transmission transit time, the variation in the duration of aerosol stability among VOCs may not explain the difference in transmission rates of VOCs. This data will be useful for assessing the future evolution of aerosol transmission of SARS-CoV-2.Item Diode-laser-based high spectral resolution LIDAR(Montana State University - Bozeman, College of Engineering, 2021) Colberg, Luke Stewart; Chairperson, Graduate Committee: Kevin S. RepaskyThis thesis describes the design, construction, and testing of a high spectral resolution lidar (HSRL) as a part of a combined HSRL and differential absorption lidar (DIAL) system. The combined HSRL and DIAL instrument is constructed using the MicroPulse DIAL (MPD) architecture and uses distributed Bragg reflector lasers. The MPD architecture is unique because it is eye-safe and cost-effective; therefore, it is ideal for creating a network of ground-based lidars. This instrument is designed for thermodynamic profiling of the lower troposphere. A network of these instruments would be helpful for wide-scale atmospheric monitoring for weather forecasting and climate science. The purpose of the HSRL is to retrieve the optical properties of aerosols in the lower troposphere. The HSRL uses the DIAL offline laser, which has a wavelength of 770.1085 nm, and a potassium vapor cell as the spectral filter. The data retrieved from the HSRL provides the aerosol backscatter coefficient and the backscatter ratio up to an altitude of 7 km during nighttime operation and 5 km during daytime operation. The time resolution for these measurements is 5 minutes, and the range resolution is 150 m. These aerosol optical properties are valuable for aerosol studies and climate modeling; aerosols introduce the most significant degree of uncertainty in modeling the heat flux of the atmosphere. Additionally, these aerosol optical properties can be used to find the planetary boundary layer height (PBLH). The planetary boundary layer controls the exchange of heat, water vapor, aerosols, and momentum between the surface and the atmosphere. It has been demonstrated that the PBLH strongly affects turbulent mixing, convective transport, and cloud entrainment, which makes the PBLH an important parameter for weather forecasting and climate modeling. Despite its significance in atmospheric science, there is no standard method for defining the PBLH. A retrieval method for finding the daytime PBLH using HSRL data is proposed, and data comparisons to radiosonde PBLH retrievals are provided. The algorithm shows a good agreement with the radiosonde retrievals for conditions with a well-behaved boundary layer.Item Organic enrichment at aqueous interfaces studied with non-linear spectroscopy: cooperative adsorption of soluble saccharides to lipid monolayers(Montana State University - Bozeman, College of Letters & Science, 2019) Link, Katie Ann; Chairperson, Graduate Committee: Robert Walker; Chia-Yun Hsieh, Aashish Tuladhar, Zizwe Chase, Zheming Wang, Hongfei Wang and Robert A. Walker were co-authors of the article, 'Vibrational studies of saccharide-induced lipid film reorganization at aqueous/vapor interfaces' in the journal 'Chemical physics' which is contained within this thesis.; Gabrielle N. Spurzem, Aashish Tuladhar, Zizwe Chase, Zheming Wang, Hongfei Wang and Robert A. Walker were co-authors of the article, 'Organic enrichment at aqueous interfaces: cooperative adsorption of glucuronic acid to DPPC monolayers studied with vibrational sum frequency generation' submitted to the journal 'Journal of physical chemistry B' which is contained within this thesis.; Gabrielle N. Spurzem, Aashish Tuladhar, Zizwe Chase, Zheming Wang, Hongfei Wang, and Robert A. Walker were co-authors of the article, 'Cooperative adsorption of trehalose to DPPC studied with vibrational sum frequency generation' which is contained within this thesis.Field measurements of sea spray aerosols have reported high concentrations of soluble organic material that are in excess of the concentration of soluble organics in the ocean. The studies described in this dissertation investigated a possible mechanism for this increase deemed cooperative adsorption. The cooperative adsorption mechanism describes an interaction between an insoluble Langmuir monolayer at the aqueous/vapor interface and soluble organic molecules that would not normally be enriched at the surface. In this model, the soluble organics are drawn to the surface through non-covalent interactions with the lipid surfactant. This mechanism was investigated with the surface specific nonlinear optical technique, vibrational sum frequency generation spectroscopy. These optical measurements were coupled with surface tension measurements and differential scanning calorimetry measurements. To study cooperative adsorption, model systems were used; these were composed of a phosphatidylcholine lipid surfactant, DPPC, and soluble saccharides including glucosamine, glucuronic acid, and trehalose. Glucosamine, in both a positive and neutral state, induced ordering in both expanded and condensed DPPC monolayers, supporting cooperative adsorption as a mechanism. Glucuronic acid, an anion, ordered lipid monolayers in the limits that the lipid DPPC was moderately packed and there were no competing ions in solution. Trehalose, a larger, uncharged saccharide showed, through ordering the DPPC monolayer, indications of cooperative adsorption in moderately packed DPPC when the trehalose concentration was sufficiently high. These results support cooperative adsorption as a mechanism for the accumulation of soluble organics in sea spray aerosols with some limitations.Item Use of a two color LIDAR system to study atmospheric aerosols(Montana State University - Bozeman, College of Letters & Science, 2010) Todt, Benjamin David; Chairperson, Graduate Committee: Kevin S. RepaskyThis thesis demonstrates the use of a two color lidar (light detection and ranging) instrument for the purpose of studying atmospheric aerosols. The instrument and the analysis techniques are explained and discussed to provide the necessary back-ground. The calibration is discussed and demonstrated followed by an example of the data analysis. The lidar's combination with a digital camera used to image cloud formations is then discussed and preliminary results are displayed.Item Two wavelength Lidar instrument for atmospheric aerosol study(Montana State University - Bozeman, College of Engineering, 2008) Hoffman, David Swick; Chairperson, Graduate Committee: Kevin S. RepaskyA two-color lidar instrument and inversion algorithms have been developed for the study of atmospheric aerosols. The two-color lidar laser transmitter is based on the collinear fundamental 1064 nm and second harmonic 532 nm output of a Nd:YAG laser. Scattered light is collected by the two-color lidar receiver using a Schmidt-Cassegrain telescope with the 532 nm channel monitored using a gated photomultiplier tube (PMT) and the 1064 nm channel monitored using an avalanche photodiode (APD). Data is collected from the PMT and APD using a 14 bit 200 MHz data acquisition card. The lidar inversion algorithm developed to analyze the data collected by the two-color lidar is based on a constant lidar ratio assumption at both the 1064 nm and 532 nm wavelengths with the constrained ratio aerosol model (CRAM) providing the initial lidar ratios at the two wavelengths to complete the lidar inversion. Data from the CALIOP lidar on board the CALIPSO satellite are presented to verify software algorithm performance. Data from the two-color lidar are then presented demonstrating the two-color lidar instrument's capabilities. The analysis of these data identifies smoke and industrial aerosols in the atmosphere above Bozeman. Finally an error analysis of the lidar instrument and accompanying analysis software is presented. The findings of this analysis are that error introduced by the APD and PMT is dominant; the error introduced by the optical detectors is much larger than the error from other sources examined such as quantization error, and the error associated the use of numerical integration in the data analysis algorithm.