Engineering Commons^™

Characterization Of Radiotolerance In Potato And Development Of A Gamma Radiation Phytosensor., Robert Graham Sears

Doctoral Dissertations

As humans pursue space travel and nuclear energy, the risk of harm from ionizing radiation increases. On Earth or in space, plants are essential to our personal and environmental health. Plants serve as sentinels, bioremediators and food sources in areas of high ionizing radiation, therefore it is essential to understand how ionizing radiation affects plant biology. This work aimed to understand plant responses to ionizing radiation in the potato chassis and apply that knowledge to generate novel phenotypes for nuclear energy and space applications. The first gamma radiation phytosensor was developed for monitoring at standoff distances greater than three meters. …

Characterization Of Lignin Structural Variability And The Associated Application In Genome Wide Association Studies, Nathan D. Bryant

Doctoral Dissertations

Poplar (Populus sp.) is a promising biofuel feedstock due to advantageous features such as fast growth, the ability to grow on marginal land, and relatively low lignin content. However, there is tremendous variability associated with the composition of biomass. Understanding this variability, especially in lignin, is crucial to developing and implementing financially viable, integrated biorefineries. Although lignin is typically described as being comprised of three primary monolignols (syringyl, guaiacyl, p-hydroxyphenyl), it is a highly irregular biopolymer that can incorporate non-canonical monolignols. It is also connected by a variety of interunit linkages, adding to its complexity. Secondary cell wall …

Examining The Relationship Between Lignocellulosic Biomass Structural Constituents And Its Flow Behavior, Ekramul Haque Ehite

Doctoral Dissertations

Lignocellulosic biomass material sourced from plants and herbaceous sources is a promising substrate of inexpensive, abundant, and potentially carbon-neutral energy. One of the leading limitations of using lignocellulosic biomass as a feedstock for bioenergy products is the flow issues encountered during biomass conveyance in biorefineries. In the biorefining process, the biomass feedstock undergoes flow through a variety of conveyance systems. The inherent variability of the feedstock materials, as evidenced by their complex microstructural composition and non-uniform morphology, coupled with the varying flow conditions in the conveyance systems, gives rise to flow issues such as bridging, ratholing, and clogging. These issues …

Understanding Lignin’S Fast Pyrolysis Through Examination Of The Thermolysis Mechanisms Of Model Oligomers, Ross Wesley Houston

Doctoral Dissertations

The lignocellulosic biorefinery is a visionary concept that endeavors to provide an alternative to fossil-based refineries by producing biobased fungible fuels and specialty chemicals almost exclusively derived currently from petroleum refineries. This vision of the lignocellulosic biorefinery can only be realized if all fractions of lignocellulosic biomass are efficiently deconstructed and valorized to generate a diverse portfolio of products to sustain it against market vicissitudes. Of the three main structural constituents of lignocellulosic biomass (i.e., cellulose, hemicellulose, and lignin), lignin is underutilized despite being the most abundant renewable source of aromatic platform chemicals, representing a growing 250 billion dollar market. …

Analysis Of Physicochemical Properties And Terrestrial Dynamics Of Mechanically Formed Micro-Nano Scaled Particles From Agricultural Plastic Mulches, Anton Friedrich Astner

Doctoral Dissertations

Release of microplastics (MPs) and nanoplastics (NPs) into agricultural fields is of great concern due to their reported ecotoxicity to organisms that provide beneficial service to the soil such as earthworms, and the potential ability of MPs and NPs to enter the food chain. Most fundamental studies of the fate and transport of plastic particulates in terrestrial environments employ idealized MP materials as models, such as monodisperse polystyrene spheres. In contrast, plastics that reside in agricultural soils consist of polydisperse fragments resulting from degraded films employed in agriculture. There exists a need for more representative materials in fundamental studies of …

Biomass Conversion To Bio-Derived Materials And Their Applications, Luna Liang

Doctoral Dissertations

Nowadays, fossil fuels still serve as the primary global energy resource. Replacing fossil fuels with renewable sources of energy and developing efficient energy storage technology is an urgent problem to solve. Lignocellulosic biomass has been investigated as a promising alternative for the production of biofuels, chemicals, and materials. In this dissertation, we studied the thermochemical biomass conversion strategies via different pretreatments strategies (e.g. dilute acid, ethanol, tetrahydrofuran, gamma-valerolactone) and genetic modification to overcome the biomass recalcitrance and achieve efficient conversion process. The biomass component structure of lignin and cellulose after thermal treatments were characterized and analyzed.

To further explore the …

Approaches To Studying Bacterial Biofilms In The Bioeconomy With Nanofabrication Techniques And Engineered Platforms., Michelle Caroline Halsted

Doctoral Dissertations

Studies that estimate more than 90% of bacteria subsist in a biofilm state to survive environmental stressors. These biofilms persist on man-made and natural surfaces, and examples of the rich biofilm diversity extends from the roots of bioenergy crops to electroactive biofilms in bioelectrochemical reactors. Efforts to optimize microbial systems in the bioeconomy will benefit from an improved fundamental understanding of bacterial biofilms. An understanding of these microbial systems shows promise to increase crop yields with precision agriculture (e.g. biosynthetic fertilizer, microbial pesticides, and soil remediation) and increase commodity production yields in bioreactors. Yet conventional laboratory methods investigate these micron-scale …

Phylogenetics And Association Analyses Illustrate Substantial Cryptic Diversity Of A Newly Isolated Collection Of Cenococcum Geophilum, Jessica Velez

Doctoral Dissertations

The ectomycorrhizal fungus Cenococcum geophilum is distributed worldwide across multiple climates and soil types and is known to positively associate with a multitude of plant genera, possibly contributing to plant ability to tolerate inorganic contaminants in a soil environment. New C. geophilum isolates are easily cultured from soils in a laboratory setting, making this an ideal candidate for a model species with which to study multiple plant-fungal effects across a collection of novel isolates. However, C. geophilum is also genetically complex and, at 178Mbp, features one of the largest fungal genomes, necessitating the use of the novel restriction-associated DNA sequencing …

An Investigation Of Surface Water Sediment Source Tracking Using Bacterial Metagenomics And Elemental Fingerprinting, Yanchong Huangfu

Doctoral Dissertations

Excess suspended sediment in river systems commonly degrades surface water quality. A sediment source tracking approach is necessary to target management practices that will reduce significant sources of sediment in rainfall runoff and restore water quality. Sediment source tracking utilizes the biogeochemical characteristics of sediment, often paired with a mathematical model, to link eroding source materials and in-stream suspended sediment. However, there are still many questions left unanswered in using this approach, including simultaneously identifying fecal contamination sources, quantifying the reliability of sediment tracers, and methods to assess the accuracy of sediment source identification. The research herein utilized the microbial …

Natural Ventilation Models And Production Management In An Experimental High Tunnel, Muzi Zheng

Doctoral Dissertations

High tunnels (HTs) help producers to be more profitable through crop protection and extension of growing season. Proper ventilation and heat managements inside HTs are crucial for adjusting inner microclimates and future obtaining marketable crop production. This study first analyzed daytime ventilation rates that responds to the changes of external weather conditions in a Gothic-type HT located in eastern Tennessee. A mathematical energy balance model and instrumental measurement serve as validation data were developed with a good agreement for ventilation rates (R²>0.70). The coupling of energy balance model and air-flux calculation based on external weather parameters can be …

The Impacts Of Biopolymer-Ionic Liquid Interactions On The Utilization Of Lignocellulosic Biomass, Jing Wang

Doctoral Dissertations

In the bioenergy field, the recalcitrance of lignocellulosic biomass has been mainly attributed to lignin. Many ionic liquid (IL) pretreatments were performed to maximize the removal of lignin. However, those methods seriously degraded lignin and hemicellulose, and could generate lignin or hemicellulose for developing an integrated biorefinery that utilizes efficiently the whole biomass. To fulfill the requirements of the integrated biorefineries, this dissertation explored the interactions between biopolymers and IL for a better utilization of lignocellulosic biomass as feedstock. By removing a large portion of hemicellulose, through an autohydrolysis, this physical and chemical barrier for IL diffusion was dismantled and …

Biodegradation And Photodegradation Of Polylactic Acid And Polylactic Acid/ Polyhydroxyalkanoate Blends Nonwoven Agricultural Mulches In Ambient Soil Conditions, Sathiskumar Dharmalingam

Doctoral Dissertations

Agricultural mulch films, typically made of petroleum-based polyethylene, improve crop productivity by controlling weeds and providing microclimate. Extreme fragmentation of films imposes labor and disposal costs, not to mention environmental problems during and after service life. Although mulches made of biodegradable polymers such as cellulose, (nonbiobased) poly (butylene adipate-co-terephthalate) and polybutylene succinate are employed in the field, the fate of biodegradation of additives in mulches is still questionable in addition to service life until the harvesting. Nonwovens, made of biobased polymers such as poly (lactic acid) (PLA) and PLA-polyhydroxy alkanoate (PHA) blends, have been developed using nonwovens textile technology to …