Fredericksburg folio, Virginia-Maryland
Folio 13, published 1894
Author: Darton, Nelson Horatio, 1865-1948.
Gov't Doc number: I19.5/1:13
Published by: Geological Survey (United States)
In collection: Geologic Atlas of the United States
Permanent URI: http://hdl.handle.net/1969.1/3013
Showing items related by title, author, creator and subject.
An empirical examination of the role of characteristics of the format, standard setting alliance and alliance partners in the market acceptance of formatsDan, Sujan Mathew (August 2008)[more][less]
Abstract: New product introductions rely on technologies that are often subject to strongly contested standards wars. In an attempt to ensure that the technical formats that their products are built upon, are the ones that gain widespread market acceptance and thereby emerge as industry standards, firms often engage in alliances to develop and/or market these technical formats. This research examines the relationships between the characteristics of standard setting alliances, those of the alliance partners, the technical formats and the market acceptance of the formats. In doing so, I seek to complement prior research by developing and empirically testing a theoretical framework of these relationships. While a few studies (Axelrod et al. 1995; Chiao, Lerner and Tirole 2007) have examined how firms form and organize standard setting alliances, the relationship between the characteristics of such alliances and their success (i.e., the market’s acceptance of the technical format supported by the alliance) is an under-researched subject. A format that is widely accepted by the market (adopted in more products and adopted by more firms) is in turn more likely to emerge as a standard. Using a unique data set of formats and standard setting alliances in the consumer electronics industry, assembled from multiple sources, I examine this link between standard setting alliances and format characteristics, and the market’s acceptance of the format. Results indicate that the relationship between the size of a standard setting alliance (number of partners in alliance) and the market acceptance of a format is inverted U-shaped. This suggests that a larger membership in the development alliance does not always imply that the alliance activities will lead to market acceptance of the format. I find that alliances with a greater proportion of generalists are shown to be capable of developing formats that find greater acceptance in the market. Marketing intensity in the years prior to forming the alliance is found to be important. The results also suggest that the broader the applicability of a technical format across industries, the greater its market acceptance. Interestingly though, the hypothesis that formalized alliances lead to greater market acceptance of the format was not supported by the data. I conclude with a discussion of the potential contributions and implications of the findings for marketing practice and future research.
Files in this item: 1DAN-DISSERTATION.pdf (371.5Kb)
Hong, Seok Hoon (December 2011)[more][less]
Abstract: Biofilms are formed in aquatic environments by the attachment of bacteria to submerged surfaces, to the air/liquid interface, and to each other. Although biofilms are associated with disease and biofouling, the robust nature of biofilms; for example, their ability to tolerate chemical and physical stresses, makes them attractive for beneficial biotechnology applications such as bioremediation and biofuels. Based on an understanding of diverse signals and regulatory networks during biofilm development, biofilms can be engineered for these applications by manipulating extracellular/intercellular signals and regulators. Here, we rewired the global regulator H-NS of Escherichia coli to control biofilm formation using random protein engineering. H-NS variant K57N was obtained that reduces biofilm formation 10-fold compared with wild-type H-NS (wild-type H-NS increases biofilm formation whereas H-NS K57N reduces it) via its interaction with the nucleoid-associated proteins Cnu and StpA. H-NS K57N leads to enhanced excision of the defective prophage Rac and results in cell lysis through the activation of a host killing toxin HokD. We also engineered another global regulator, Hha, which interacts with H-NS, to disperse biofilms. Hha variant Hha13D6 was obtained that causes nearly complete biofilm dispersal by increasing cell death by the activation of proteases. Bacterial quorum sensing (QS) systems are important components of a wide variety of engineered biological devices, since autoinducers are useful as input signals because they are small, diffuse freely in aqueous media, and are easily taken up by cells. To demonstrate that biofilms may be controlled for biotechnological applications such as biorefineries, we constructed a synthetic biofilm engineering circuit to manipulate biofilm formation. By using a population-driven QS switch based on the LasI/LasR system and biofilm dispersal proteins Hha13D6 and BdcAE50Q (disperses biofilms by titrating cyclic diguanylate), we displaced an existing biofilm and then removed the second biofilm. Persisters are a subpopulation of metabolically-dormant cells in biofilms that are resistant to antibiotics; hence, understanding persister cell formation is important for controlling bacterial infections. Here, we engineered toxin MqsR with greater toxicity and demonstrated that the more toxic MqsR increases persistence by decreasing the ability of the cell to respond to antibiotic stress through its RpoS-based regulation of acid resistance, multidrug resistance, and osmotic resistance systems.
Files in this item: 1HONG-DISSERTATION.pdf (5.501Mb)
Removing of Formation Damage and Enhancement of Formation Productivity Using Environmentally Friendly ChemicalsMahmoud, Mohamed Ahmed Nasr Eldin (May 2011)[more][less]
Abstract: Matrix acidizing is used in carbonate formations to create wormholes that connect the formation to the wellbore. Hydrochloric acid, organic acids, or mixtures of these acids are typically used in matrix acidizing treatments of carbonate reservoirs. However, the use of these acids in deep wells has some major drawbacks including high and uncontrolled reaction rate and corrosion to well tubulars, especially those made of chrome-based tubulars (Cr-13 and duplex steel), and these problems become severe at high temperatures. Hydrochloric acid (HCl) and its based fluids have a major drawback in stimulating shallow (low fracture gradient) formations as they may cause face dissolution (formation surface washout) if injected at low rates. The objective of stimulation of sandstone reservoirs is to remove the damage caused to the production zone during drilling or completion operations. Many problems may occur during sandstone acidizing with Hydrochloric/Hydrofluoric acids (HCl/HF) mud acid. Among those problems: decomposition of clays in HCl acids, precipitation of fluosilicates, the presence of carbonate can cause the precipitation of calcium fluorides, silica-gel filming, colloidal silica-gel precipitation, and mixing between various stages of the treatment. To overcome problems associated with strong acids, chelating agents were introduced and used in the field. However, major concerns with most of these chemicals are their limited dissolving power and negative environmental impact. Glutamic acid diacetic acid (GLDA) a newly developed environmentally friendly chelate was examined as stand-alone stimulation fluid in deep oil and gas wells. In this study we used GLDA to stimulate carbonate cores (calcite and dolomite). GLDA was also used to stimulate and remove the damage from different sandstone cores containing different compositions of clay minerals. Carbonate cores (calcite and dolomite) of 6 and 20 in. length and 1.5 in. diameter were used in the coreflood experiments. Coreflood experiments were run at temperatures ranging from 180 to 300oF. Ethylene diamine tetra acetic acid (EDTA), hydroxyl ethylethylene diaminetriacetic acid (HEDTA), and GLDA were used to stimulate and remove the damage from different sandstone cores at high temperatures. X-ray Computed Topography (CT) scans were used to determine the effectiveness of these fluids in stimulation calcite and dolomite cores and removing the damage from sandstone cores. The sandstone cores used in this study contain from 1 to 18 wt percent illite (swellable and migratable clay mineral). GLDA was found to be highly effective in creating wormholes over a wide range of pH (1.7-13) in calcite cores. Increasing temperature enhanced the reaction rate, more calcite was dissolved, and larger wormholes were formed for different pH with smaller volumes of GLDA solutions. GLDA has a prolonged activity and leads to a decreased surface spending resulting in face dissolution and therefore acts deeper in the formation. In addition, GLDA was very effective in creating wormholes in the dolomite core as it is a good chelate for magnesium. Coreflood experiments showed that at high pH values (pH =11) GLDA, HEDTA, and EDTA were almost the same in increasing the permeability of both Berea and Bandera sandstone cores. GLDA, HEDTA, and EDTA were compatible with Bandera sandstone cores which contains 10 wt percent Illite. The weight loss from the core was highest in case of HEDTA and lowest in case of GLDA at pH 11. At low pH values (pH =4) 0.6M GLDA performed better than 0.6M HEDTA in the coreflood experiments. The permeability ratio (final/initial) for Bandera sandstone cores was 2 in the case of GLDA and 1.2 in the case of HEDTA at pH of 4 and 300oF. At high pH HEDTA was the best chelating agent to stimulate different sandstone cores, and at low pH GLDA was the best one. For Berea sandstone cores EDTA at high pH of 11 was the best in increasing the permeability of the core at 300oF. The low pH GLDA based fluid has been especially designed for high temperature oil well stimulation in carbonate and sandstone rock. Extensive studies have proved that GLDA effectively created wormholes in carbonate cores, is gentle to most types of casing including Cr-based tubular, has a high thermal stability and gives no unwanted interactions with carbonate or sandstone formations. These unique properties ensure that it can be safely used under extreme conditions for which the current technologies do not give optimal results. Furthermore, this stimulation fluid contributes to a sustainable future as it based on readily biodegradable GLDA that is made from natural and renewable raw material.
Files in this item: 1MAHMOUD-DISSERTATION.pdf (9.774Mb)