79717 research outputs found
Sort by
Malicious-proof and fair credit-based resource allocation techniques for DSA systems
Get PDFIn this paper, we propose a credit-based resource allocation technique for dynamic spectrum access (DSA) systems that is robust against malicious and selfi sh behaviors and ensures good overall system fairness performance while also allowing spectrum users to achieve high amounts of service. We also propose a new objective function that, when combined with the proposed credit-based technique, leads to further improvements of the system fairness performance. Our proposed techniques overcome user misbehavior by masking the impact of the users' pursued private objectives on the overall system performance. They also improve fairness among users by allocating service to users adaptively by accounting for how much service each user has received in the past. Our simulation results show that our proposed techniques maintain high system performance by allowing users to achieve high amounts of service and by ensuring fair allocation of spectrum resources among users even in the presence of misbehaved users. Using simulations, we also show that these high performances are also achievable under various di fferent network scenarios.Keywords: dynamic spectrum access, resource allocation, wireless networks, fairness, distributed technique
Photophysics of organic semiconductors at the nanoscale
Get PDFOrganic semiconductors are used in a wide variety of applications including transistors,solar cells, and light emitting diodes. These materials are solution-processable,low cost, and tunable. Many successful organic optoelectronic materials utilizeblends of several types of molecules (such as donors and acceptors) in order topromote charge generation. As blends are an inherently heterogeneous system,nanoscale morphology plays a critical role to determine the optoelectronic propertiesof the blend. The work presented in this dissertation aims to develop novelmethods of probing the local nanoenvironment in organic semiconductors as wellas establish the relations between the nanoscale environment of the molecules andtheir photophysics.First, several experiments were performed via single molecule fluorescence microscopyto study energy transfer (FRET) and photo-oxidation in blends containingdonor and acceptor molecules. Donor molecules were imaged with increasingacceptor molecule concentration to determine the change in their photophysicalproperties due to acceptor-modified morphology and donor-acceptor energy transfer.As the concentration of acceptor molecules reaches a critical concentration suchthat the average donor-acceptor distance is below the FRET radius, fluorescenceof donor molecules is quenched. This enables single-molecule-level microscopy atrelatively high donor concentrations, thus creating a new super-resolution tool toimage donor molecules in a modified local environment. As the concentration of acceptorsincreased, the number of photons a donor emits over its lifetime decreased,and fluorescence intermittency increased. These observations were quantified usingstatistical analysis and complementary cumulative distribution functions. Thefindings were attributed to the acceptor-modified morphology which reduced thedonor molecule protection from photo-oxidation reactions; however, the presenceof the acceptors also enhanced the reversibility of the photo-oxidation process byquenching the highly reactive singlet oxygen. Such reversibility is important fororganic semiconductors as their photodegradation is one of the key drawbacks forapplications.Next, molecular packing and photostability changes are presented as a functionof different host matrices and different molecular side groups, again via singlemolecule fluorescence spectroscopy. Molecules embedded in a crystalline organicsemiconductor host matrix exhibited higher photostability than a polymer matrix.In addition, larger side groups lead to higher photostability, indicating thelarger side groups provide better protection from reactions with oxygen. Orientationalconstraints for guest molecules in a crystalline host were also observed andquantified.Lastly, a novel method to study photoinduced charge transfer between organicsemiconductors utilizing optical tweezers is presented. A silica microsphereis coated with an organic semiconductor (e.g. donor) film and suspended in aliquid with varying dielectric permittivity and containing other organic semiconductormolecules (e.g. acceptors). The time-resolved surface charge of this sphereis measured by trapping the sphere using optical tweezers and applying a sinusoidalelectric field across the sphere. (Dis)charging dynamics are measurable byphotoexciting the coating of the sphere and observing the dynamics of excitonsby monitoring the photoluminescence of the trapped sphere while simultaneouslymeasuring surface charge with optical tweezers.Keywords: effective charge, organic semiconductors, optical tweezers, FRET, charge transfer, single molecule fluorescence spectroscopy, photobleaching, fluorescence intermittenc
Knowing your customers : ontological gathering and analysis techniques
Get PDFThis research presents a methodology to analyze customer needs and direct the gathering of customer needs that both span the need space and are independent. An ontological categorization, the fundamental research contribution of this work, is created to support both aims of the overall methodology. Providing designers with a customer need ontology that allows the categorization and further analysis of their customer needs set for a product gives insight on the types of needs that may be missing, how to go about collecting those needs, as well as when to gain further insight on needs in certain categories. This ontology can also be used to assess customer need gathering and analysis techniques, providing a map to the types of needs that techniques are geared to produce. This work begins by examining the state of the art in customer need analysis and categorization, highlighting the opportunities that currently exist to formalize customer needs activities in the early phase of design. The ontology constructed for this research is introduced as a method to guide designers as they examine and categorize customer needs. The creation, iteration, and inter-rater reliability of this ontology is presented. The validation of the ontology is presented in two separate studies. The first study examines differences between customer needs lists at two distinct points in a design effort. The differences found in this study correspond with the expected differences between the groups, providing validation of the ontology’s ability to span the need space. The second study presents the analysis of three need gathering techniques which provides further validation around the concept of guiding designers to needs independence. The research in this dissertation constructs a customer need ontology, validates the ontology, and presents a methodology with three approaches using the ontology to guide designers to new insight into customer needs.Keywords: engineering design, customer needs, ontolog
Consider the community : developing predictive linkages between community structure and performance in microbial fuel cells
Get PDFThe complex, dynamic nature of microbial communities in both natural and engineered environments complicates the work of scientists and engineers who wish to channel microbial interactions for societal good. The successful management of these communities towards engineering goals is dependent on developing predictive linkages between community structure and functional outputs. The performance of microbial fuel cells (MFCs), an emerging environmental biotechnology, is driven by a diverse microbial community capable of converting the chemical potential energy contained in waste streams to electrical energy. This technology stands to benefit greatly from an increased understanding of the microorganisms contained within as it transitions from the laboratory to practical application. MFCs also offer a controlled environment in which new approaches to developing predictive understandings of microbial communities can be developed.Revolutions in molecular science over the past decade paved the way for the rapid increase in genomic data available for microbial communities from a wide range of environments. Increases in computing power and accessibility over the same period provide a means in which the amassed community data can be mined for potential interactions and linked to functional outcomes. One of the methods through which this can be done is the use of artificial neural networks (ANNs). ANN-based models can be used to generate accurate microbial assemblage predictions across a variety of environments, but have never been applied to the microbial communities of environmental biotechnologies.In the present dissertation, MFC biofilms are analyzed over time, across reactor designs, under varying environmental conditions, and following pH disruption to identify core community membership. Results demonstrated that deterministic interactions shaped consistent community structures characterized by the formation of highly conductive anodic biofilms. The core MFC community is defined by a high abundance of anode-respiring Geobacter sulfurreducens. and biomass fermenting Aminiphilus circumscriptus along with other syntrophic bacteria. Community structure shifted into repeatable formations following the introduction of various substrates and wastewaters. Under changing conditions reactor performance in terms of power generation, treatment rates, and coulombic efficiencies was repeatable and linked to community composition using ANN models. ANN models that incorporated community predictions performed significantly better than those solely based on environmental parameters and predicted all performance metrics within 6% providing the first evidence for the value of including community data into ANN-based MFC models. Community composition could also be linked to biofilm stability following exposure to low pH solutions. Through the first quantitative evaluations of biofilmresilience in MFCs a correlation between the relative abundance of Geobacteraceae and process stability was observed, however, ANN models that considered relative abundance of other bacteria predicted stability more accurately. Further development of these models can be used in practical settings to determine and avoid risk of deactivation during operation.This dissertation characterizes a single MFC community over a variety of conditions and represents the first attempt to use machine-learning based approaches to connect community structure to performance in environmental biotechnology applications. The further development of these and other similar artificial intelligence data-mining tools will improve the management of microbial communities that drive environmental biotechnologies like MFCs and spur them towards practical application. Strengthening linkages between community, structure, interactions, and function in these technologies may be applied across industries, inspiring new applications and innovations involving microbial communities.Keywords: environmental biotechnology, microbial fuel cells, artificial neural networks, biofilms, microbial communit
Fine scale foraging behavior of gray whales in relation to prey fields and vessel disturbance along the Oregon Coast
Get PDFThe desire to understand the spatial and temporal drivers of animal behavior and distribution relative to scale is central to movement ecology. Optimal foraging theory states that a predator should continue exploiting a patch until it is no longer profitable to do so. As human developments increasingly encroach on the marine environment, understanding how anthropogenic interactions affect predator searching and foraging behaviors is key to minimizing disturbance. In 2015 and 2016, two studies were conducted to assess how gray whale behavior state changes (1) relative to static and dynamic environmental cues, and (2) relative to vessel interactions. The first study was addressed through the non-invasive documentation of gray whale movements (n = 76 tracks) using shore-based theodolites for eight weeks from July-August 2016, in Port Orford, Oregon, USA. When conditions allowed, a research kayak was concurrently navigated to 18 sampling stations in two comparative study sites (Mill Rocks and Tichenor Cove) within the study area. Go-Pro cameras were used to record zooplankton relative density in the water column (n=198 casts), and zooplankton net tows (n=107) were used to assess community structure. Video stills were scored for quality and relative density of zooplankton, and averaged through the water column to provide a daily density estimate of zooplankton density for each station. Whale behaviors were categorized into search, forage, and transit using the Residence in Space and Time (RST) method; behavior state was then assessed relative to static and dynamic variables at multiple scales. Despite being only one kilometer apart, there were significant spatio-temporal differences in the community assemblages of zooplankton between the two study areas, and whales demonstrated scale-dependent habitat selection relative to predictable static features (kelp) and dynamic prey availability. In Tichenor Cove, mysids (Holmesimysis sculpta), a known regional gray whale prey item, dominated the community, yet whales spent little time foraging here. Whales preferentially foraged in Mill Rocks where a combination of mysids and gammarid amphipods, previously undocumented as gray whale prey in Oregon, were prevalent. The second study occurred in the summer of 2015, and tracked whales and vessels using non-invasive, shore based theodolite and photo ID techniques. Two sites with differing levels of vessel traffic, Boiler Bay and Port Orford, were monitored for 4 weeks each. Whale focal follows were again analyzed with RST to assess behavior state changes relative to location, individual, and vessel presence, type, and distance to whale. There were significant differences in population level gray whale activity budgets between control and impact conditions, and between study sites. No significant difference in individual response to vessels disturbance was found. Taken together, the results of these two studies show that gray whales maximize energy gain through predictable, successful foraging. In the absence of vessels, foraging gray whales use information from a static feature and prey availability at a fine scale (<0.5 km) and larger regional scale (1-2 km), but searching behavior may be influenced by these features in a scale-dependent manner. When a vessel is present, disturbance appears to be tolerated as long as the foraging is profitable. Multi-faceted studies such as these advance the knowledge of which factors inform fine scale predator decision making in an increasingly anthropogenically impacted environment and have the potential to inform local management and conservation efforts.Keywords: Eschrichtius robustus, vessel interactions, Oregon, gray whales, foraging ecology, ecotouris
Flavin-containing monooxygenase : metabolism and toxicity of anti-tuberculosis drug ethionamide in lung
Get PDFMultiple drug resistance (MDR) Tuberculosis (TB), leads to increased use of “second-line” drugs; one of the most effective is ethionamide (ETA). ETA is a prodrug metabolized by a mycobacterial flavin-containing monooxygenase (EtaA) as well human flavin-containing monooxygenases (FMOs). Of the five functional FMOs of humans, FMOs 1, 2, and 3 are the most important in metabolism of xenobiotics. FMO2 is a major isoform in the lung expressed in most mammals. In humans a polymorphism encoding inactive FMO2 is the common allele, while the wild type allele encoding active FMO2.1 has been documented only in individuals of African and Hispanic origin, at an incidence of up to 50% and 7%, respectively. Human FMO2.1 is more efficient than EtaA in the first S-oxygenation of ETA to ETA S-oxide (ETASO). ETASO is a sulfenic acid and capable of redox-cycling with glutathione (GSH) producing oxidative stress and toxicity. We hypothesized that the FMO2 polymorphism will result in differences in the concentration and spectrum of ETA prodrug and metabolites. TB-infected individuals expressing active FMO2.1 will have reduced ETA efficacy in inhibition and killing of M. tuberculosis and enhanced oxidative stress, pulmonary toxicity and cell death in the host. To test this hypothesis, Fmo1/2/4 knockout mice modeling the FMO2*2 genotype were utilized to study ETA metabolism and toxicity compared to wild type mice in order to model humans expressing the FMO2*1 allele.
All mice were capable of metabolizing ETA to ETASO. Wild type mice had significantly higher plasma and epithelial lining fluid (ELF) levels of ETASO than ETA. In contrast, Fmo 1/2/4 knockout mice had higher plasma and ELF levels of ETA than ETASO. ETASO, a sulfenic acid, was significantly higher in wild type mice than knockout mice in both plasma and ELF. Investigation of the effects of higher levels of ETASO in wild type mice was warranted. Long-term ETA dosing was utilized to examine oxidative stress and toxicity. Compare to Fmo 1/2/4 knockout mice, wild type male and female mice showed more differentially expressed genes in lung related to oxidative stress and antioxidant defense pathways. Altered Fmo1, 2 and 4 expression was also found in lung and liver of long-term ETA-treated wild type mice in comparison to vehicle controls. To examine ETA therapeutic efficacy in the presence and absence of FMO, wild type and knockout mice were infected with M. avium and dosed with 50 mg/kg of ETA for 28-days and compared with vehicle-dosed mice for bactericidal effects. An ETA dose of 50 mg/kg did not significantly reduce the mycobacterium infection, leaving the fundamentally question of the role of FMO2 polymorphism on ETA efficacy unresolved. Though interestingly, significant higher bacterial load was observed in the ETA treated wildtype compared to ETA treated knockout mice which suggest that the presence of FMO in wildtype is making these mice more susceptible to bacterial infection when ETA is dosed.
Collectively these studies suggest that humans expressing active FMO2.1 may be at higher risk of ETA toxicity than individuals with inactive FMO2.2 that are undergoing long-term ETA treatment for MDR-TB. This work highlights the potential of the FMO2 human genetic on TB drug selection to maximize treatment efficacy and minimize toxicity. Another study of M. tuberculosis infected mice with 125 mg/kg dose of ETA is required to understand ETA therapeutic efficacy in the presence and absence of FMOs.Keywords: ethionamide, ET
Economic Analysis of the Potential for Nuclear Energy Investment in Eastern Europe
Get PDFThis paper contributes to the ongoing discussion on the impacts of nuclear energy on the economy and energy security of select European countries. While previous literature has identified a connection between nuclear energy and economic growth, this study focuses on assessing the comparative effects of nuclear energy, measured by operable nuclear power capacity (MWe), on energy self-sufficiency across a range of European countries. By employing a two-way fixed effects model, this study analyzes the potential relationship between nuclear energy capacity and energy self-sufficiency while accounting for various factors that influence both variables. To ensure the robustness of findings, collinearity was examined using the variance inflation factor (VIF), which gauges the presence of multicollinearity among independent variables. Additionally, stationarity was investigated through unit root tests (ADF test) to assess the long-term behavior of the variables under inspection. This analysis reveals compelling results, suggesting that investment in nuclear energy has the potential to enhance energy self-sufficiency for multiple European countries, with a particular emphasis on certain Eastern European nations. By exploring the specific effects of nuclear energy capacity on energy self-sufficiency, this study provides valuable insights for policymakers, private nuclear companies, and researchers interested in the sustainable development of advanced nuclear energy systems in Europe.Keywords: Nuclear Energy, Econometrics, Economic Analysis, Energy Economic
The role of manganese peroxidase in biomass conversion technologies
Get PDFCurrently, the technologies used to separate lignocellulosic biomass into its component parts (cellulose, hemicellulose, and lignin) and enzymatically hydrolyze the cellulose to glucose for conversion to ethanol could be improved economically and in terms of efficiency. A major impediment to utilizing the biomass is the presence of residual lignin. The residual lignin "poisons" the cellulase enzymes and as a result, a lower glucose yield is obtained. A higher titer of cellulases could be used to increase the yield of glucose, but cellulases are expensive. A possibility to reduce the cost of cellulase enzymes and improve the efficiency, economics, extent and/or rate of hydrolysis is to use lignin-degrading fungal heme peroxidase such as manganese peroxidases. An efficient and economical glucose assay was developed to monitor the rate and extent of enzymatic hydrolysis of cellulose. The glucose assay is based on the glucose oxidase horseradish peroxidase enzymatic method, but uses bulk enzymes making it more economical than commercial kits. The glucose assay also has a higher throughput rate and is more economical than HPLC. In order to evaluate possible synergistic effects between cellulases and manganese peroxidase (MnP), rMnP was produced in high cell density fed-batch cultivations by the genetically engineered yeast, P. pastoris. In addition, a mathematic model was developed to describe the temperature dependant growth of P. pastoris and consumption of glucose and the production and temperature dependent degradation of rMnP in the bioreactor broth. The model successfully predicted the cell growth, substrate consumption, and rMnP production for the base case and also for cultivations with varying fed-batch air flow rates (k[subscript L]a) and temperatures. The production of rMnP requires cultures amended with exogenous heme and there are several sources of heme. Through shake flask experiments and bioreactor cultivations it was determined that 0.1 g/L of heme was necessary for producing high titers of rMnP (4,500 U/L). It was also determined that not all types of heme will yield the same rMnP titer. The water soluble fraction post pretreatment of lignocellulosic biomass contains inhibitors to fermentation such as 5-hydroxymethyl furfural (HMF) and furfural. rMnP was shown to degrade HMF (1 g/L) and furfural (1 g/L) and detoxify medium containing these inhibitors. The rMnP reduced furfural and HMF, measured by absorbance at 276 and 286 nm respectively and the degree of absorbance decrease was dependent on rMnP concentration. Furfural was more readily degraded by rMnP than HMF. Growth assays using S. cerevisiae indicated rMnP treatment detoxified medium containing furfural and HMF. The optimal conditions (temperature, pH, and buffer) for enzyme activity were determined for both AccelleraseTM 1000 (commercially available combination of cellulases) and rMnP using filter paper as a substrate. Woody biomass and corn stover were pretreated and then exposed to simultaneous or sequential treatment with rMnP and AccelleraseTM 1000. The results for the sequential treatment of Ponderosa pine and corn stover with rMnP and AccelleraseTM 1000 was inconclusive as to whether or not rMnP effected the production of glucose due to the high variability between replicates. Finally, part of my doctoral program was significant mentoring and facilitation of undergraduate research. A significant portion of my time was dedicated toward senior laboratory teaching assistance, serving as a mentor for high school students, and participating in research mentoring with 24 undergraduate students over five years, 19 of whom were women
Properties of hydrogels for immobilization of bacteria in a commercial microfluidic bioreactor
No full textCurrent technological shortcomings limit the economic viability of capturing and utilizing small sources of methane. The development of a reactor to overcome these limitations would unlock economic opportunity and incentivize reduced methane emissions. A microfluidic bioreactor containing immobilized methanotrophs has the potential to overcome these limitations by profitably converting small quantities of methane to more valuable liquid products.The material used for immobilizing bacteria in a microfluidic bioreactor must meet four criteria: biocompatibility, mechanical stability, reactor adhesion, and economic viability. This paper describes the development of a novel blend of agar and cross-linked polyvinyl alcohol (PVA) that meets these requirements. The properties of agar PVA blend hydrogels strongly depend on the ratio and absolute concentration of the constituent polymers, and the processes by which the polymers are cross-linked. The microscopic morphology of these blend hydrogels is theorized to be two interacting and competing phases formed by agar and PVA molecules mutually interfering with cross-linking via hydrogen bonding, and separating due to spinodal decomposition. Evidence for the proposed morphology is discussed.Blend hydrogels of 2 5% agar PVA are particularly promising, combining the desirable properties of both agar (low swelling) and PVA (strength and adhesion). The 2 5% agar PVA gels exhibited little swelling in water and nitrate mineral salts-based media. They also adhered to polycarbonate and stainless steel surfaces treated with ozone or oxygen plasma. Cultures of Methylomicrobium buryatense 5GB1 (5GB1) immobilized in these gels showed a reduction of metabolic activity rates, partly due to exposure to high concentrations of sulfate and phosphate during cross-linking. Shortening cross-linker exposure time from 2 hours to 30 minutes greatly improved activity rates, and immobilized cells exhibited increased activity rates over time as fresh methane was added. Based on these results, the 2 5% agar PVA blend hydrogels are suitable for the immobilization of 5GB1 in a microfluidic bioreactor. Further improvement of activity rates may be possible.Preservation of 5GB1 by lyophilization was unsuccessful. Cultures preserved in solutions of 5% bovine serum albumin and 10% sucrose or trehalose maintained metabolic activity rates after freezing at -80°C, but showed no activity after lyophilization.Keywords: PVA, Lyophilization, Agar, Hydrogel, Immobilization, Microfluidic, Methanotroph, Bioreacto
Optimization of interactive live free viewpoint multiview video streaming bandwidth
No full textThere are generally two types of multiview video:(1) 3D Multiview Video (“3D MVV” also called “2D plus delta” or “stereo” multi-view video): 3D MVV is widely deployed in cinemas and in the TV industry. 3D MVV typically entails capturing video of an object using two cameras with differing view angles to allow for depth perception.(2) Free Viewpoint Multiview Video TV (“FTV”): Free Viewpoint Multiview Video allows the user to freely pan horizontally based on an array of cameras.While advances have occurred for 3D MVV, and to a lesser extent, stored FTV [Cheung2011], the commercialization and advancement of live Free Viewpoint Multiview Video has stalled. The failure of FTV is attributed to the lack of standardization and the high bandwidth requirements of the FTV content.This thesis provides a solution to obtain a significant reduction in FTV broadcast and P2P bandwidth utilization as compared to current proposed methods, while maximizing the user experience for the given bandwidth