Decentralized control with input saturation: a first step toward design

This article summarizes important observations about control of decentralized systems with input saturation and provides a few examples that give insight into the structure of such systems

A Geophysical Delineation of A Normal Fault Within the Gulf Coastal Plain, Montgomery County, Texas

The Gulf Coast of Texas has been a known hydrocarbon basin for many years with various structural trapping mechanisms such as anticlines, faults and salt domes. While most large salt domes have been extensively studied in the Gulf Coastal Plain, many smaller normal faults have not been studied in detail. This research study employs an integrated geophysical approach to mapping the Big Barn fault in Montgomery County, Texas. This fault is located on the Gulf Coastal Plain and is approximately 20 miles north of Houston, Texas. Most normal faults in the Gulf Coastal Plain formed as a result of the Gulf of Mexico basin which started during the Jurassic Period as a result of the breakup of Pangea and the rifting of North and South America. The Big Barn fault formed during the Jurassic but there is evidence that the fault plane has been recently reactivated. Within the past 20 years, extensive deformation and fractures within the vicinity of the fault have formed on Interstate Highway 45 (IH 45) and caused damage to nearby businesses and residences. In this study gravity, electrical resistivity surveys and traditional mapping techniques were conducted to determine the cause of deformation and the extent of faulting. Two-dimensional inverted resistivity models were made to determine the structures and stratigraphy of the area

The Biological Control of Spotted Knapweed in the Southeastern United States

Spotted knapweed is an invasive, short-term-perennial plant that is native to Eurasia. It was accidentally introduced into North America in the early 1890\u27s and has since spread across The United States and Canada. Spotted knapweed degrades rangelands and pastures by negatively impacting native plants, increasing soil surface runoff and stream sediment yields, and reducing soil infiltration. A biological control program for spotted knapweed using Larinus minutus (Coleoptera: Curculionidae), was initiated in Arkansas in 2008. In this dissertation I described the releases of L. minutus and investigated the adult activity in the southeastern United States (Chapter 1), investigated the effects of timed mowings on spotted knapweed and the effect of these mowings on L. minutus (Chapter 2), investigated the efficacy of L. minutus in reducing spotted knapweed infestations (Chapter 3), determined if there were any interactions between L. minutus and Urophora quadrifasciata (Chapter 4), and determined if it was feasible to use multispectral remote sensing to detect and monitor spotted knapweed populations. Releases of L. minutus were made at 39 sites in 7 different counties between 2008 and 2012. Thorough monitoring of the sites indicated establishment of the weevil. In Arkansas, L. minutus emerges earlier in the year than in the Pacific Northwest, but is still univoltine. It was determined that the most effective time for mowing spotted knapweed when L. minutus is not present is May, but if weevils are present in high numbers the most opportune time is in July. L. minutus reduced spotted knapweed seed production and rosette densities, but monitoring of the release sites needs to continue for several more years to document the impact of the release program on spotted knapweed in the region. The occurrences of Larinus minutus and Urophora quadrifasciata in the capitula of spotted knapweed are not independent of each other, although, this interaction had no effect on the number of seeds found in a capitulum. Finally it was determined that it is feasible to detect spotted knapweed with multispectral remote sensing throughout the growing season and it is feasible to monitor the change in spotted knapweed populations due to control efforts

Characterizing efficiency of multi-Enzyme cascade-based biofuel cells by product analysis

pre-printThe performance of biofuel cells with enzyme cascades have normally been characterized with open circuit potential, power density, and current density measurements. In this work, we demonstrate that with the method of quantitative product analysis by mass spectrometry, we can obtain other valuable information about the biofuel cell efficiency. Faradaic efficiency, coulombic efficiency and product efficiency were calculated for a six-enzyme glucose biofuel cell system. Oxidation pathway bottlenecks were determined with quantitative mass spectrometry measurements via direct infusion. These measurements and calculations give an in-depth understanding of the bioelectrocatalytic bottlenecks in the enzyme cascade for the target fuel (glucose)

Nickel cysteine complexes as anodic electrocatalysts for fuel cells

pre-printCompared to platinum, nickel is an inexpensive catalyst that can oxidize methanol in alkaline media. There is a desire to increase nickel loading during electrodeposition for improved performance. In this paper, a nickel cysteine complex (NiCys) is used as the precursor for electrodeposition on glassy carbon electrode surfaces. After optimization of cysteine concentration, the surface concentration of NiOOH on NiCys electrodes characterized by cyclic voltammetry in 0.1 M NaOH can reach 1.28 (± 0.32) × 10−7 mol/cm2. The large amount of NiOOH on NiCys electrodes provide 5 times the methanol oxidation current compared to Ni electrodes prepared without cysteine as demonstrated by chronoamperometry at 0.7 V vs. Hg/HgO. Atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy have been applied to examine surface morphologies and structures of NiCys and Ni electrodes. The analysis reveals that cysteine adjusts the solubility of Ni(OH)2 in 0.1 M NaOH, so more uniform and smaller size nanoparticles are electrodeposited on electrode surfaces compared to Ni electrodes

High performance glucose/O2 biofuel cell: effect of utilizing purified laccase with anthracene-modified multi-walled carbon nanotubes

pre-printLaccase, a blue multicopper oxidoreductase enzyme, is a robust enzyme that catalyzes the reduction of oxygen to water and has been shown previously to perform improved direct electron transfer in a biocathode when mixed with anthracene-modified multi-walled carbon nanotubes. Previous cathode construction used crude laccase enzyme isolated as a brown cell extract powder containing both active and inactive proteins. Purification of this enzyme, yielding a blue solution, resulted in greatly improved enzyme activity and removed insulating protein that competed for docking space in this cathodic system. Cyclic voltammetry of the purified biocathodes showed a background subtracted limiting current density of 1.84 (±0.05) mA/cm2 in a stationary air-saturated system. Galvanostatic and potentiostatic stability experiments show that the biocathode maintains up to 75% and 80% of the original voltage and current respectively over 24 hours of constant operation. Inclusion of the biocathode in a glucose/O2 biofuel cell using a mediated glucose oxidase (GOx) anode produced maximum current and power densities of 1.28 (±0.18) mA/cm2 and 281 (±50) μW/cm2 at 25◦C and 1.80 (±0.06) mA/cm2 and 381 (±33) μW/cm2 at 37◦C, respectively. Enzymatic efficiency of this glucose/O2 enzymatic fuel cell is among the highest reported for a glucose/O2 enzymatic fuel cell

Utilizing DNA for electrocatalysis: DNA-Nickel aggregates as anodic electrocatalysts for methanol, ethanol, glycerol, and glucose

pre-printDNA-nickel aggregates were electrodeposited onto glassy carbon electrode surfaces and have shown electrocatalytic activity for oxidation of methanol, ethanol, glycerol, and glucose at room temperature in alkaline solutions. Bulk electrolysis oxidation products identified by 13C NMR include carbonate as methanol, glycerol, and glucose's oxidation products suggesting these three fuels can be deeply oxidized by DNA-nickel aggregates and carbon-carbon bonds can be broken during the oxidation of glycerol and glucose. However, ethanol was only oxidized to acetate. The capability of deep oxidation of methanol, ethanol, glycerol and glucose under relatively moderate conditions makes DNA-nickel a candidate for fuel cell applications

Self-Powered Biosensors

Self-powered electrochemical biosensors utilize biofuel cells as a simultaneous power source and biosensor, which simplifies the biosensor system, because it no longer requires a potentiostat, power for the potentiostat, and/or power for the signaling device. This review article is focused on detailing the advances in the field of self-powered biosensors and discussing their advantages and limitations compared to other types of electrochemical biosensors. The review will discuss self-powered biosensors formed from enzymatic biofuel cells, organelle-based biofuel cells, and microbial fuel cells. It also discusses the different mechanisms of sensing, including utilizing the analyte being the substrate/fuel for the biocatalyst, the analyte binding the biocatalyst to the electrode surface, the analyte being an inhibitor of the biocatalyst, the analyte resulting in the blocking of the bioelectrocatalytic response, the analyte reactivating the biocatalyst, Boolean logic gates, and combining affinity-based biorecognition elements with bioelectrocatalytic power generation. The final section of this review details areas of future investigation that are needed in the field, as well as problems that still need to be addressed by the field

Improved performance of a thylakoid bio-solar cell by incorporation of carbon quantum dots

pre-printCarbon quantum dots (CQDs) were incorporated into thylakoid bioanodes capable of direct photobioelectrocatalysis in order to increase the photocurrent generation. More thylakoids are in contact with the increased surface area which allows for greater direct electron transfer (DET). Additionally, the fluorescent quantum dots redshift the light which allows for the thylakoid/CQD electrodes to use more of the solar spectrum, increasing the photocurrent. The current density was more than twice as large when CQDs were included in a thylakoid bio-solar cell