Browsing by Subject "Organic"
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Item Agricultural Preservation Precedent Studies(Minneapolis: Center for Urban and Regional Affairs, 2009) Schweser, GregItem Alternative practices in organic dairy and broiler production and their effects on animal behavior, health, and welfare(2021-08) Phillips, HannahThe animal welfare of organic livestock is a major interest among producers, the public, researchers, and veterinarians. This dissertation presents the results from 5 experiments conducted between 2016 and 2020 on a research farm at the University of Minnesota West Central Research and Outreach Center in Morris. The experiments were designed to investigate novel practices in organic livestock production and their potential efficacy on improving animal welfare. These results include information on the efficacy of herbal pain management therapies for disbudded dairy calves, methods to prevent distress and mastitis in transitioning dairy heifers, efficacy of broilers to control face fly larva, and effects of outdoor stocking density on behaviors of free-range broilers. To summarize the results of ineffective practices, the tested herbal tincture did not reduce pain in disbudded calves, white willow bark did not reduce inflammatory biomarkers in calves, and broiler chickens did not reduce the survival of face fly larva in cow manure. To summarize the results of effective practices, teat dipping and acclimating heifers to the milking parlor 3 weeks prior to calving improved milking behaviors and reduced Staphylococcus aureus intramammary infections in heifers over the first 3 days after calving. Furthermore, additional outdoor space for free-broiler chickens reduced aggressive attacks and reduced some rarely observed behaviors that are akin to discomfort. To conclude, experiments on the novel topics discussed in this dissertation serve as a foundation for future comprehensive investigations related to practices that affect the animal welfare of organic livestock.Item Comparison Of Two Different Grazing Systems Incorporating Cool And Warm Season Forages For Organic Dairy Cattle(2017-01) Ruh, KathrynTwo pasture systems with enhanced in-field and landscape level species diversity were analyzed for yield, forage quality, and mineral characteristics across the grazing season at the West Central Outreach and Research Center organic dairy in Morris, MN from 2013 to 2015. System 1 was a diverse-mixture of cool season grasses and legumes. System 2 was the same combination of perennial grasses and included warm season annual grasses (BMR sorghum-sudangrass (Sorghum × drummondii; BMRSS) and teff (Eragrostis tef) grass). Organic dairy cows (n = 90) of Holstein and crossbred genetics were used to evaluate the effect of the two pasture systems on milk production, milk components (fat, protein, MUN, SCS), body weight, body condition score (BCS), and activity and rumination (min/d). The rumen fermentation of BMRSS, teff, cool season perennial pastures, and alfalfa were also studied using a dual flow continuous culture rumen fermentation system.Item The effect of organic price premia and equivalence agreements on select organic imports into the United States(2014-05) Kristiansen, Devon MaryThis thesis estimates a gravity trade model using new USDA organic trade data and domestic organic and conventional prices for wheat, corn, and soy. The study empirically analyzes the effect of equivalence agreements on imports of these commodities into the US. Further, the price premium of organic goods is used to proxy for restrictiveness of domestic organic supply. The Poisson model estimation results are generally consistent with theory. Organic imports into the United States are positively associated with exporter income and exporter population, and negatively associated with distance. The coefficient estimate for the price ratio indicates that as domestic prices for organic corn, soy, or wheat rise relative to the conventional substitute, the US increases imports. The effect of equivalence agreements cannot be directly measured using the data available.Item Light-matter interactions in optical nanostructures based on organic semiconductors(2012-12) Lodden, Grant H.The confinement of a semiconductor material to an optical microcavity leads to an inherent coupling between light and matter. Depending on the lifetime of the excited state of the semiconductor (the exciton) and the cavity photon, two distinct regimes of interaction are possible. The system is said to be weakly coupled if either the exciton or the cavity photon decay before the two species interact. Weak exciton-photon coupling results in a modification of the exciton lifetime, the spectral shape, and the angular dispersion of emission from the microcavity. Conversely, when the lifetimes of the exciton and cavity photon are long enough so that an interaction occurs prior to either state decaying, the regime of strong exciton-photon coupling is realized. The timescale for coupling is the Rabi period, which depends on exciton and cavity parameters including the exciton oscillator strength and transition linewidths. The eigenstates of the strongly coupled system are known as microcavity polaritons. Microcavity polaritons have unique properties arising from their mixed exciton-photon character, permitting the realization of novel optoelectronic devices. Organic semiconductors are attractive for application in strongly coupled systems due to their large exciton binding energy (~1 eV), which permits a robust coupled state that is stable at room temperature and under electrical excitation. In addition, organic semiconductors exhibit large exciton oscillator strengths (~1015 cm-2) resulting in a strong interaction between the cavity photon and the exciton. We aim to better the understanding of polaritons in organic semiconductor microcavities to push the field towards novel optoelectronic devices.Item Modeling of electronic properties in organic semiconductor device structures.(2012-05) Chang, Hsiu-ChuangOrganic semiconductors (OSCs) have recently become viable for a wide range of electronic devices, some of which have already been commercialized. With the mechanical flexibility of organic materials and promising performance of organic field effect transistors (OFETs) and organic bulk heterojunction devices, OSCs have been demonstrated in applications such as radio frequency identification tags, flexible displays, and photovoltaic cells. Transient phenomena play decisive roles in the performance of electronic devices and OFETs in particular. The dynamics of the establishment and depletion of the conducting channel in OFETs are investigated theoretically. The device structures explored resemble typical organic thin-film transistors with one of the channel contacts removed. By calculating the displacement current associated with charging and discharging of the channel in these capacitors, transient effects on the carrier transport in OSCs may be studied. In terms of the relevant models it is shown that the non-linearity of the process plays a key role. The non-linearity arises in the simplest case from the fact that channel resistance varies during the charging and discharging phases. Traps can be introduced into the models and their effects examined in some detail. When carriers are injected into the device, a conducting channel is established with traps that are initially empty. Gradual filling of the traps then modifies the transport characteristics of the injected charge carriers. In contrast, dc measurements as they are typically performed to characterize the transport properties of organic semiconductor channels investigate a steady state with traps partially filled. Numerical and approximate analytical models of the formation of the conducting channel and the resulting displacement currents are presented. For the process of transient carrier extraction, it is shown that if the channel capacitance is partially or completely discharged through the channel resistance, qualitatively different time dependences of the displacement current may be obtained. Depending on the final state of the capacitor, either fully discharged or remaining partially charged, the displacement current in the long time limit shows power law or exponential dependence on time. The salient effect of including fast traps in this model is to change the apparent exponent in the resulting approximate power law for the case of full depletion. The exponent of the power law decreases in magnitude as the ratio of the emission to capture rates decreases. In contrast, the effects of slow traps are quite different. If significant, slow traps can give rise to a slowly decaying displacement current. In organic bulk heterojunction photovoltaic cells, large interfacial areas that impact the efficiency of photo-generation of charge carriers are of critical importance. Carrier recombination at the interface is studied on the basis of two bilayer structures with interfaces perpendicular and parallel to the current direction, which idealize the island-like morphology of mixed materials. Overall recombination currents at the interface are found to depend strongly on the interface orientation and on parameters that control the time scales of interfacial recombination and carrier transport.Item On the properties and design of organic light-emitting devices(2014-01) Erickson, Nicholas CarterOrganic light-emitting devices (OLEDs) are attractive for use in next-generation display and lighting technologies. In display applications, OLEDs offer a wide emission color gamut, compatibility with flexible substrates, and high power efficiencies. In lighting applications, OLEDs offer attractive features such as broadband emission, high-performance, and potential compatibility with low-cost manufacturing methods. Despite recent demonstrations of near unity internal quantum efficiencies (photons out per electron in), OLED adoption lags conventional technologies, particularly in large-area displays and general lighting applications. This thesis seeks to understand the optical and electronic properties of OLED materials and device architectures which lead to not only high peak efficiency, but also reduced device complexity, high efficiency under high excitation, and optimal white-light emission. This is accomplished through the careful manipulation of organic thin film compositions fabricated via vacuum thermal evaporation, and the introduction of a novel device architecture, the graded-emissive layer (G-EML). This device architecture offers a unique platform to study the electronic properties of varying compositions of organic semiconductors and the resulting device performance. This thesis also introduces an experimental technique to measure the spatial overlap of electrons and holes within an OLED's emissive layer. This overlap is an important parameter which is affected by the choice of materials and device design, and greatly impacts the operation of the OLED at high excitation densities. Using the G-EML device architecture, OLEDs with improved efficiency characteristics are demonstrated, achieving simultaneously high brightness and high efficiency.Item Organic High Tunnel Raspberry Production(University of Minnesota Extension, 2021) Klodd, Annie; Worth, LeahItem Spotted-wing Drosophila: Investigating the Efficacy of Innovative and Alternative Management Techniques(2020-01) Gullickson, MatthewSpotted-wing drosophila (Drosophila suzukii; SWD) established recently in North America as an invasive insect pest of small and soft skinned fruit, responsible for significant economic losses nationwide and locally in Minnesota. Female SWD use a heavily sclerotized and serrated ovipositor to deposit eggs in ripening and ripe fruit. Larvae then emerge and develop within the flesh which results in unmarketable fruit at harvest. Consequently, there is a zero-tolerance threshold for larvae in fresh fruit. Current management strategies are often limited to regular applications of broad- spectrum insecticides, primarily organophosphates, spinosads, and pyrethroids. Weekly sprays may have deleterious ecological impacts to beneficial, non-target species including pollinators. Additionally, frequent spraying can contribute to insecticide resistance and may even fail to adequately protect fruit from infestation. Organic pesticide application for SWD management is particularly difficult for growers due to fewer chemical options and increased cost compared to conventional products. Since the arrival of SWD and the subsequent increase of insecticidal sprays, it has been a significant challenge for producers to balance economics as well as pest and pollinator management goals. Weekly conventional insecticide rotations in primocane raspberries can still result in widespread infestation likely due to high SWD populations, immigration by new individuals, and/or inadequate spray penetration in the dense plant canopy. Frequent applications of broad spectrum insecticides continues to be the most prevalent management strategy, but pesticide resistance is a concern. Resistance has already been reported for one of the only effective insecticides labeled for organic production systems, underscoring the need to diversify management strategies. Responding to the critical need for additional management tools and chemical alternatives, the goal of this research was to investigate the efficacy of novel chemical controls and physical exclusion on SWD in primocane raspberry fruit. For our first set of experiments, we conducted a series of laboratory bioassays to test twenty-five potential pesticide treatments. We measured the effects of these treatments on SWD adult mortality, oviposition, larval and pupal development, and adult emergence. This information was used to guide a follow up study testing thirteen of the most promising treatments on SWD mortality and infestation in the field. Results showed that the broad spectrum conventional and organic controls provided the best SWD control, however botanical products provided some protection against infestation. Additionally, there is increasing interest in using physical exclusion and high tunnel production as a pest management tool, particularly since many growers already use high tunnels for season extension and improved fruit quality. Our second set of experiments investigated how plastic-covered, enclosed tunnels affected fruit yield and quality, as well as SWD infestation. We collected data on yield, proportion of marketable and unmarketable fruit, berry size, total soluble solids (°Brix), proportion of infested fruit, and the microclimate characteristics inside of the plots. The objective of these experiments was to improve integrated pest management strategies for SWD and provide recommendations for both organic and conventional growers for sustainable management of this invasive pest.Item Synthetic Control and Characterization of NU-1000(2019-12) Webber, TomThe production and release of greenhouse gasses has become a major issue in today’s society. Methane is a powerful greenhouse gas and is the main component of natural gas. Natural gas is often collected and transported to be used as a fuel, but leaks result in release of some of that methane into the atmosphere. Work is underway to develop an efficient catalyst capable of selective oxidation of methane to methanol. Metal-organic frameworks have become popular candidates for catalysts and catalyst scaffolds. The Zr-based metal-organic framework NU-1000 is a robust, mesoporous material that can be used in a variety of applications, including catalysis, sensing, gas separation and storage, and scaffolds. It can be synthesized by combining a solution of hexazirconium nodes ([Zr6O16H16]8+) and organic acid modulator in N,N-dimethylformamide with a solution of linker (1,3,6,8-tetrakis(p-benzoic acid)pyrene) and aging at elevated temperature. The typical product is 1-3 μm crystals that are primarily composed of NU-1000 but that contain domains of an impurity phase called NU-901 that is a polymorph of NU-1000. The ideal NU-1000 synthesis will yield phase-pure particles and enable control over crystal size. The structural differences between NU-1000 and NU-901 lead to a hypothesis that changing the organic acid modulator from benzoic acid to a larger and more rigid carboxylic acid might lead to steric interactions between the modulator coordinating on the node and linkers bound to nodes, inhibiting growth of the more dense NU-901-like material and resulting in phase-pure NU-1000. Side-by-side reactions comparing the products of synthesis using benzoic acid or biphenyl-4-carboxylic acid as organic acid modulator produce structurally heterogeneous crystals and phase-pure NU-1000 crystals, respectively. NU-1000 particles synthesized in the range of 1-3 μm, while useful for many applications, are not large enough for single-crystal X-ray diffraction and are not small enough for nanomaterial applications like drug delivery. The synthesis of NU-1000 provides a variety of experimental handles that can be tuned to produce a wide range of particle sizes. For example, the rate of nucleation and growth is closely tied to the concentration of modulator. This is because NU-1000 is formed via a competitive reaction between modulator and linker molecules for the binding sites on the hexa-Zr nodes. By changing the concentration of the linker, modulator, and any additives, the nucleation and growth rates can be altered to produce the desired particle size. The choice of Zr precursor between ZrOCl2 • 8 H2O and ZrCl4 also plays a significant role in determining the resulting particle size. People acquire a wide range of data like crystal size and morphology, crystallographic information, and elemental quantification and distribution using techniques like transmission electron microscopy and energy-dispersive X-ray spectroscopy. The characterization of size, size distribution, crystallinity, and chemical composition are critical to studying the catalytic properties of product materials. However, due to the delicate nature of MOFs, gathering this data can be very challenging. MOFs commonly undergo radiation damage under a focused electron beam causing a loss of crystallinity. While various techniques can circumvent this damage like cryogenic transmission electron microscopy and low-dose electron microscopy, this dissertation focuses on analyzing the damage and ensuring the data collected remains reliable.Item Synthetic efforts toward a total synthesis of (+)-Pelorusdie A.(2009-06) Kopel, Lucas C.This thesis has been divided into six chapters that describe synthetic efforts toward the cytotoxic marine macrolide (+)-peloruside A, isolated by Northcote and coworkers from the New Zealand marine sponge Mycale hentscheli. Chapter 1 discusses the background of peloruside A and published literature studies relating to its biological activity. Chapter 2 conveys a detailed report of the synthetic efforts by others that have resulted in three total syntheses and multiple efforts toward the total synthesis of peloruside A. Chapter 3 describes the previous synthetic efforts by Hoye group members toward peloruside A. Two different strategies for synthesizing the C13-C20 fragment of (+)-peloruside A have been established using ring-closing metathesis. Synthesis of the C1-C9 fragment of (+)-peloruside A was accomplished using a kinetic lactonization strategy. Chapter 4 reports on my efforts at scaling-up and optimizing the synthesis of the C1-C9 fragment of (+)-peloruside A and modifications to the previous route. Chapter 5 describes the new progress toward synthesizing (+)-peloruside A that was achieved. These efforts culminated in the synthesis of a C1-C11 fragment of (+)-peloruside A along with studies investigating the coupling of late stage segments via a 1,5-anti boron-mediated aldol. Chapter 6 highlights the key features of my synthetic efforts toward (+)-peloruside A.Item Use of metagenomics and metatranscriptomics to determine the influence of organic sulfur compounds on the sulfur cycle in the sediment of a low-sulfate freshwater system(2020-08) Hyde, EmilyThe sulfur cycle is an important and complex biogeochemical cycle involving both inorganic and organic species in both oxic and anoxic environments. However, due to the lack of research regarding the sulfur cycle in freshwater systems, the contributions of organic sulfur compounds to the sulfur cycle are underappreciated. Recent studies have suggested organic sulfur compounds likely fuels sulfate reduction, especially in low-sulfate oligotrophic freshwater systems, through a possible cryptic sulfur cycle. To determine the contributions that organic sulfur compounds may have in this environment, we used Lake Superior sediment to analyze for the presence of and expression of sulfur cycling genes. In these metagenomes, we found genes for sulfur reduction, oxidation and organic sulfur compound degradation. Metabolic pathway analysis showed presence of not only organic sulfur compounds contributing to the sulfur cycle, but tetrathionate, thiosulfate, and polysulfides playing a role as well. Using Lake Superior sediments, we also conducted sediment incubations to measure the biotransformation capability of sulfur-containing amino acids, sulfonates, and an analog for a common sulfolipid. Taurine and sodium dodecyl sulfate produced higher sulfate values in incubations, suggesting that microbes prefer sulfonates over sulfur-containing amino acids, in addition to a possible partiality towards oxidized organic sulfur compounds over reduced forms regarding sulfate production. The preference of sulfonates is supported by the commonality of taurine genes present as well as the low, but present transcription values of sulfoacetaldehyde degradation. While sulfur-containing amino acids do not produce sulfate values near that of sulfonates or sulfolipids, there are still present and transcriptionally active genes that can contribute to sulfate reduction in the system. Regarding methyl-sulfurs, metatranscriptomic data shows that methyl-mercaptan (intermediate within dimethyl sulfide and methionine degradation) degradation is transcriptionally active across genomes. By combining biotransformation incubation data, metagenomics, and metatranscriptomics, we analyzed how methylated sulfurs, sulfur-containing amino acids and sulfonates can fuel a sulfur cycle in a low-sulfate environment, informing us on how pathways may have operated in our Earth’s geologic past.