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Structure, Function and Reconstitution of Antenna Complexes of Green Photosynthetic Bacteria

Description: Most chlorophyll-type pigments in a photosynthetic organism function as an antenna, absorbing light and transferring excitations to a photochemical reaction center where energy storage takes place by a series of chemical reactions. The green photosynthetic bacteria are characterized by large antenna complexes known as chlorosomes, in which pigment-pigment interactions are of dominant importance. The overall objective of this project is to determine the mechanisms of excitation transfer and regulation of this unique antenna system, including how it is integrated into the rest of the photosynthetic energy transduction apparatus. Techniques that are being used in this research include biochemical analysis, spectroscopy, microscopy, X-ray structural studies, and reconstitution from purified components. Our recent results indicate that the chlorosome baseplate structure, which is the membrane attachment site for the chlorosome to the membrane, is a unique pigment-protein that contains large amounts of carotenoids and small amounts of bacteriochlorophyll a. Reconstitution of directed energy transfer in chlorosomes will be carried out using purified baseplates and oligomeric pigments. The integral membrane B808-866 antenna complex from Chloroflexus aurantiacus and the Fenna-Matthews-Olson protein-reaction center complex from green sulfur bacteria will be characterized by spectroscopic and structural techniques.
Date: June 10, 2005
Creator: Blankenship, Robert E.
Partner: UNT Libraries Government Documents Department

Dual Phase Membrane for High temperature CO2 Separation

Description: Research in the previous years in this project found that stainless steel supports are oxidized during high temperature, dual phase membrane separation of carbon dioxide (with oxygen). Consequently, a new material has been sought to alleviate the problems with oxidation. Lanthanum cobaltite oxide is a suitable candidate for the support material in the dual phase membrane due to its oxidation resistance and electronic conductivity. Porous lanthanum cobaltite membranes were prepared via the citrate method, using nitrate metal precursors as the source of La, Sr, Co and Fe. The material was prepared and ground into a powder, which was subsequently pressed into disks for sintering at 900 C. Conductivity measurements were evaluated using the four-probe DC method. Support pore size was determined by helium permeation. Conductivity of the lanthanum cobaltite material was found to be at a maximum of 0.1856 S/cm at 550 C. The helium permeance of the lanthanum cobaltite membranes for this research was on the order of 10{sup -6} moles/m{sup 2} {center_dot} Pa {center_dot} s, proving that the membranes are porous after sintering at 900 C. The average pore size based on steady state helium permeance measurements was found to be between 0.37 and 0.57 {micro}m. The lanthanum cobaltite membranes have shown to have desired porosity, pore size and electric conductivity as the support for the dual-phase membranes. Molten carbonate was infiltrated to the pores of lanthanum cobaltite membranes support. After infiltration with molten carbonate, the helium permeance of the membranes decreased by three orders of magnitude to 10{sup -9} moles/m{sup 2} {center_dot} Pa {center_dot} s. This number, however, is one order of magnitude larger than the room temperate permeance of the stainless steel supports after infiltration with molten carbonate. Optimization of the dip coating process with molten carbonate will be evaluated to determine if lower permeance values ...
Date: December 1, 2005
Creator: Lin, Jerry Y.S. & Anderson, Matthew
Partner: UNT Libraries Government Documents Department

A NOVEL APPROACH TO MINERAL CARBONATION: ENHANCING CARBONATION WHILE AVOIDING MINERAL PRETREATMENT PROCESS COST

Description: Known fossil fuel reserves, especially coal, can support global energy demands for centuries to come, if the environmental problems associated with CO{sub 2} emissions can be overcome. Unlike other CO{sub 2} sequestration candidate technologies that propose long-term storage, mineral sequestration provides permanent disposal by forming geologically stable mineral carbonates. Carbonation of the widely occurring mineral olivine (e.g., forsterite, Mg{sub 2}SiO{sub 4}) is a large-scale sequestration process candidate for regional implementation, which converts CO{sub 2} into the environmentally benign mineral magnesite (MgCO{sub 3}). The primary goal is cost-competitive process development. As the process is exothermic, it inherently offers low-cost potential. Enhancing carbonation reactivity is key to economic viability. Recent studies at the U.S. DOE Albany Research Center have established that aqueous-solution carbonation using supercritical CO{sub 2} is a promising process; even without olivine activation, 30-50% carbonation has been achieved in an hour. Mechanical activation (e.g., attrition) has accelerated the carbonation process to an industrial timescale (i.e., near completion in less than an hour), at reduced pressure and temperature. However, the activation cost is too high to be economical and lower cost pretreatment options are needed. Herein, we report our first year progress in exploring a novel approach that offers the potential to substantially enhance carbonation reactivity while bypassing pretreatment activation. We have discovered that robust silica-rich passivating layers form on the olivine surface during carbonation. As carbonation proceeds, these passivating layers thicken, fracture and eventually exfoliate, exposing fresh olivine surfaces during rapidly-stirred/circulating carbonation. We are exploring the mechanisms that govern carbonation reactivity and the impact that (1) modeling/controlling the slurry fluid-flow conditions, (2) varying the aqueous ion species/size and concentration (e.g., Li{sup +}, Na{sup +}, K{sup +}, Rb{sup +}, Cl{sup -}, HCO{sub 3}{sup -}), and (3) incorporating select sonication offer to enhance exfoliation and carbonation. Thus far, we have succeeded in ...
Date: October 1, 2005
Creator: McKelvy, Michael J.; Chizmeshya, Andrew V.G.; Squires, Kyle; Carpenter, Ray W. & Bearat, Hamadallah
Partner: UNT Libraries Government Documents Department

Structure, Function and Reconstitution of Antenna Complexes from Green Photosynthetic Bacteria

Description: This project is concerned with the structure and function of the chlorosome antennas found in green photosynthetic bacteria. Chlorosomes are ellipsoidal structures attached to the cytoplasmic side of the inner cell membrane. These antenna complexes provide a very large absorption cross section for light capture. Evidence is overwhelming that the chlorosome represents a very different type of antenna from that found in any other photosynthetic system yet studied. It is now clear that chlorosomes do not contain traditional pigment-proteins, in which the pigments bind to specific sites on proteins. Instead, the chlorosome pigments are organized in vivo into pigment oligomers in which direct pigment-pigment interactions are of dominant importance. Our group has used a multidisciplinary approach to investigate this unique system, as well as the complexes that they directly interact with. Our work has included using model systems, numerous types of both steady-state and ultrafast spectroscopy, molecular biology, protein chemistry and X-ray crystallography. Details of our recent results using these approaches are given below and in the references. Numbers cited in the sections refer to DOE-sponsored publications that are listed below. Only publications dated 2001-2004 or later are included in this report. In addition to the primary literature reports, a comprehensive review of this area of research has been written as well as a commentary.
Date: August 10, 2005
Creator: Blankenship, Robert E.
Partner: UNT Libraries Government Documents Department

Caustic Waste-Soil Weathering Reactions and Their Impacts on Trace Contaminant Migration & Separation - Final Report

Description: Studies of the reactivity of radionuclides (Cs, Sr, I) in STWL with model clays and natural sediments were conducted by coupling macroscopic sorption-desorption experiments with spectroscopic and microscopic investigations over a wide range of reaction times. Three experimental systems were studied: (1) model clay minerals, (2) products of homogeneous precipitation from STWL, and (3) representative Hanford sediments, with (1) and (3) reacted with STWL from 1 h to 369 d. The clay minerals included illite, vermiculite, smectite and kaolinite, which constitute a sequence of micaceous weathering products with variable reactivity toward Cs+, Sr2+ and I-. Coarse and fine sediments collected from the Hanford formation (HC and HF, respectively) and Ringold Silt (RS) were studied in batch experiments and Warden silt loam was used in batch and column experiments. Solutions were analyzed by inductively coupled plasma-mass spectrometry (ICP-MS). Solid products (referred to here as ''secondary phases'' relative to the initial reactant minerals) were analyzed for time-dependent changes in mineralogy and modes of contaminant bonding by a variety of methods, including X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM) with energy dispersive spectrometry (EDS), thermogravimetric analysis (TGA), nuclear magnetic resonance (NMR), X-ray absorption spectroscopy (XAS), including extended X-ray absorption fine structure (EXAFS) and X-ray absorption near-edge structure (XANES) analysis, and Fourier-transform infrared spectroscopy (FTIR).
Date: September 15, 2005
Creator: Tyburczy, James A. : Chorover, John & O'Day, Peggy
Partner: UNT Libraries Government Documents Department

Technical Report -- Essentials of which will be published as a journal paper

Description: Vertical Transport and Mixing in Complex Terrain Airsheds: Implementation of a Stable PBL Turbulence Parameterization for the Mesoscale Model MM5 The difficulties associated with parameterization of turbulence in the stable nocturnal atmospheric boundary layer have been a great challenge for the night-time predictions of mesoscale meteorological models such as MM5. As such, there is a general consensus on the need for better stable boundary-layer parameterizations. To this end, two new turbulence parameterizations based on the measurements of the Vertical Transport and Mixing (VTMX) field campaign were implemented and evaluated in MM5. A unique aspect of this parameterization is the use of a stability dependent turbulent Prandtl number that allows momentum to be transported by the internal waves, while heat diffusion is impeded by the stratification. This improvement alleviates the problem of over-prediction of heat diffusion under stable conditions, which is a characteristic of conventional PBL schemes, such as MRF and Blackadar schemes employed in MM5. The predictions made with the new PBL scheme for the complex terrain airshed of Salt Lake City were compared with those made with a default scheme of MM5 and with observations made during the VTMX campaign. The new schemes showed an improvement in predictions, particularly for the nocturnal near surface temperature. Surface wind predictions also improved slightly, but not to the extent of temperature predictions. The default MRF scheme showed a significantly warmer surface temperature than observed, which could be attributed to the enhanced vertical heat exchange brought about by its turbulence parameterization. The modified parameterizations reduced the surface sensible heat flux, thus enhancing the strength of the near surface inversion and lowering the temperature toward the observed values.
Date: October 25, 2005
Creator: Fernando, Harindra J. S.; Anderson, James & Boyer, Don
Partner: UNT Libraries Government Documents Department

High resolution interface nanochemistry and structure

Description: A summary is given of results on nanospectroscopy etc. during the previous three years, divided into the following subsections: development of methods and instrumentation for interface/boundary chemical analysis, interface and boundary structure in ceramic matrix composites, quantitative composition measurements of thin films and inclusions, theoretical calculations for electron energy loss near edge fine structure and grain boundary structure, and small probe radiation effects in ceramics. Materials studied include SiC whisker-reinforced Si3N4, SiC, Si oxides, Si, Si oxynitride, other ceramics. Methods mentioned include field emission, EELS (electron energy loss spectroscopy), nanospectroscopy, electron nanoprobe, etc.
Date: January 1, 1993
Partner: UNT Libraries Government Documents Department

An integrative approach to energy, carbon, and redox metabolism in the cyanobacterium Synechocystis sp. PCC 6803

Description: The broader goal of this project was to merge knowledge from genomic, metabolic, ultrastructural and other perspectives to understand how cyanobacteria live, adapt and are regulated. This understanding aids in metabolic engineering and synthetic biology efforts using this group of organisms that contribute greatly to global photosynthetic CO2 fixation and that are closely related to the ancestors of chloroplasts. This project focused on photosynthesis and respiration in the cyanobacterium Synechocystis sp. PCC 6803, which is spontaneously transformable and has a known genome sequence. Modification of these fundamental processes in this organism can lead to improved carbon sequestration and hydrogen production, as well as to generation of high-quality biomass. In our GTL-supported studies at Arizona State University we focus on cell structure and cell physiology in Synechocystis, with particular emphasis on thylakoid membrane formation and on metabolism related to photosynthesis and respiration. Results on (a) thylakoid membrane biogenesis, (b) fluxes through central carbon utilization pathways, and (c) distribution mechanisms between carbon storage compounds are presented. Together, these results help pave the way for metabolic engineering efforts that are likely to result in improved solar-powered carbon sequestration and bioenergy conversion. Fueled by the very encouraging results obtained in this project, we already have attracted interest from major companies in the use of cyanobacteria for biofuel production.
Date: March 14, 2006
Creator: Vermaas, Willem F. J.
Partner: UNT Libraries Government Documents Department

Development of an Experimental Database and Theories for Prediction of Thermodynamic Properties of Aqueous Electrolytes and Nonelectrolytes of Geochemical Significance at Supercritical Temperatures and Pressures

Description: The reactions that cause transformations in organic compounds in the Earth’s crust remain mysterious despite decades of research into how fossil fuel resources form. A major reason for this persistent mysteriousness is the failure of many researchers to realize the intimate involvement of water in those transformations. Our goal was to overcome this staggering ignorance by developing the means to calculate the consequences of reactions involving organic compounds and water. We pursued this research from 1989 through 2006, and this report focuses on progress between 2002 and 2006. There were two major obstacles that we overcame in the course of this research. On the one hand, we developed new theoretical equations that allow researchers to make these calculations. On the other hand, we critiqued available data and provided sound means to make estimates in the absence of experimental data for hundreds of organic compounds dissolved in water. Finally, we merged these two lines of research into an interactive web site that allows users to do the calculations with the equations and data. We call the web site ORCHYD for: “ORganic Compounds HYDration properties database,” but it is far more than a database since it allows users to make extremely accurate predictions of data that may never have been measured. Our progress greatly exceeded our anticipations, and has permitted many new research investigations that were previously impossible. Despite the abrupt termination of funding for this project by the Department of Energy, we are maintaining the web site for the international scientific community. Major research results were published in eleven scientific papers, so they are all in the public domain. Benefits to the public include a new, rigorous, quantitative approach to testing ideas about the fate of organic compounds dissolved in water. These tests can be applied to geochemistry or to industrial ...
Date: February 2, 2007
Creator: Shock, Everett L.
Partner: UNT Libraries Government Documents Department

Determination of Basic Structure-Property Relations for Processing and Modeling in Advanced Nuclear Fuel: Microstructure Evolution and Mechanical Properties

Description: The project objective is to study structure-property relations in solid solutions of nitrides and oxides with surrogate elements to simulate the behavior of fuels of inert matrix fuels of interest to the Advanced Fuel Cycle Initiative (AFCI), with emphasis in zirconium-based materials. Work with actual fuels will be carried out in parallel in collaboration with Los Alamos National Laboratory (LANL). Three key aspects will be explored: microstructure characterization through measurement of global texture evolution and local crystallographic variations using Electron Backscattering Diffraction (EBSD); determination of mechanical properties, including fracture toughness, quasi-static compression strength, and hardness, as functions of load and temperature, and, finally, development of structure-property relations to describe mechanical behavior of the fuels based on experimental data. Materials tested will be characterized to identify the mechanisms of deformation and fracture and their relationship to microstructure and its evolution. New aspects of this research are the inclusion of crystallographic information into the evaluation of fuel performance and the incorporation of statistical variations of microstructural variables into simplified models of mechanical behavior of fuels that account explicitly for these variations. The work is expected to provide insight into processing conditions leading to better fuel performance and structural reliability during manufacturing and service, as well as providing a simplified testing model for future fuel production.
Date: March 1, 2009
Creator: Wheeler, Kirk; Parra, Manuel & Peralta, Pedro
Partner: UNT Libraries Government Documents Department

Metal-Air Electric Vehicle Battery: Sustainable, High-Energy Density, Low-Cost Electrochemical Energy Storage – Metal-Air Ionic Liquid (MAIL) Batteries

Description: Broad Funding Opportunity Announcement Project: ASU is developing a new class of metal-air batteries. Metal-air batteries are promising for future generations of EVs because they use oxygen from the air as one of the battery’s main reactants, reducing the weight of the battery and freeing up more space to devote to energy storage than Li-Ion batteries. ASU technology uses Zinc as the active metal in the battery because it is more abundant and affordable than imported lithium. Metal-air batteries have long been considered impractical for EV applications because the water-based electrolytes inside would decompose the battery interior after just a few uses. Overcoming this traditional limitation, ASU’s new battery system could be both cheaper and safer than today’s Li-Ion batteries, store from 4-5 times more energy, and be recharged over 2,500 times.
Date: December 21, 2009
Partner: UNT Libraries Government Documents Department

Turning Bacteria into Fuel: Cyanobacteria Designed for Solar-Powered Highly Efficient Production of Biofuels

Description: Broad Funding Opportunity Announcement Project: ASU is engineering a type of photosynthetic bacteria that efficiently produce fatty acids—a fuel precursor for biofuels. This type of bacteria, called Synechocystis, is already good at converting solar energy and carbon dioxide (CO2) into a type of fatty acid called lauric acid. ASU has modified the organism so it continuously converts sunlight and CO2 into fatty acids—overriding its natural tendency to use solar energy solely for cell growth and maximizing the solar-to-fuel conversion process. ASU’s approach is different because most biofuels research focuses on increasing cellular biomass and not on excreting fatty acids. The project has also identified a unique way to convert the harvested lauric acid into a fuel that can be easily blended with existing transportation fuels.
Date: January 1, 2010
Partner: UNT Libraries Government Documents Department

Final Scientific/Technical Report for Award No. DE-FC36-02GO12096

Description: This project consisted primarily of conducting energy efficiency, productivity improvement, and waste reduction assessments of small- and medium-sized industrial facilities. These assessments were carried out by groups of engineering students, mostly from Mechanical & Aerospace Engineering and Industrial Engineering, led by faculty members at Arizona State University. The assessed industries were generally energy-intensive manufacturers located throughout Arizona, as well as some facilities in the Las Vegas, Nevada area. During the first four years of the project period, on average our recommended annual savings per plant were $224,717, of which $71,135 were energy savings. Of these recommended savings, on average $49,659 were implemented, of which $31,679 were implemented annual energy savings. These implemented savings greatly exceeded our budgeted cost to DOE, which was approximately $8,000/assessment. In addition, a number of undergraduate and graduate students were employed and trained at the IAC, and have gone on to graduate studies and engineering careers.
Date: April 17, 2007
Creator: Phelan, P.E.
Partner: UNT Libraries Government Documents Department

In situ characterization of nanoscale catalysts during anodic redox processes

Description: Controlling the structure and composition of the anode is critical to achieving high efficiency and good long-term performance. In addition to being a mixed electronic and ionic conductor, the ideal anode material should act as an efficient catalyst for oxidizing hydrogen, carbon monoxide and dry hydrocarbons without de-activating through either sintering or coking. It is also important to develop novel anode materials that can operate at lower temperatures to reduce costs and minimized materials failure associated with high temperature cycling. We proposed to synthesize and characterize novel anode cermets materials based on ceria doped with Pr and/or Gd together with either a Ni or Cu metallic components. Ceria is a good oxidation catalyst and is an ionic conductor at room temperature. Doping it with trivalent rare earths such as Pr or Gd retards sintering and makes it a mixed ion conductor (ionic and electronic). We have developed a fundamental scientific understanding of the behavior of the cermet material under reaction conditions by following the catalytic oxidation process at the atomic scale using a powerful Environmental Scanning Transmission Electron Microscope (ESTEM). The ESTEM allowed in situ monitoring of structural, chemical and morphological changes occurring at the cermet under conditions approximating that of typical fuel-cell operation. Density functional calculations were employed to determine the underlying mechanisms and reaction pathways during anode oxidation reactions. The dynamic behavior of nanoscale catalytic oxidation of hydrogen and methane were used to determine: ? Fundamental processes during anodic reactions in hydrogen and carbonaceous atmospheres ? Interfacial effects between metal particles and doped ceria ? Kinetics of redox reaction in the anode material
Date: September 19, 2013
Creator: Sharma, Renu; Crozier, Peter & Adams, James
Partner: UNT Libraries Government Documents Department

Final Report

Description: The project addressed the need for improved multijunction solar cells as identified within the Solar America Initiative program. The basic Ge/InGaAs/InGaP triple-junction structure that has led to record commercial efficiencies remains unoptimized due to excess current in the germanium component. Furthermore, its deployment cannot be scaled up to terawatt-level applications due to bottlenecks related to germanium’s cost and abundance. The purpose of the program was to explore new strategies developed at Arizona State University to deposit germanium films on much cheaper silicon substrates, largely eliminating the germanium bottleneck, and at the same time to develop new materials that should lead to an improvement in multijunction efficiencies. This included the ternary alloy SiGeSn, which can be inserted as a fourth junction in a Ge/SiGeSn/InGaAs/InGaP structure to compensate for the excess current in the bottom cell. Moreover, the possibility of depositing materials containing Sn on Si substrates created an opportunity for replacing the bottom Ge cell with a GeSn alloy, which, combined with new III-V alloys for the top cells, should enable 4-junction structures with perfectly optimized band gaps. The successes of the program, to be described below, has led to the developments of new strategies for the growth of high-quality germanium films on Si substrates and to a widespread recognition that SiGeSn is likely to play a significant role in future generations of high-efficiency devices, as demonstrated by new research and intellectual property efforts by major US industrial players.
Date: January 3, 2013
Creator: Kouvetakis, John
Partner: UNT Libraries Government Documents Department

A Novel Approach To Mineral Carbonation: Enhancing Carbonation While Avoiding Mineral Pretreatment Process Cost

Description: Known fossil fuel reserves, especially coal, can support global energy demands for centuries to come, if the environmental problems associated with CO{sub 2} emissions can be overcome. Unlike other CO{sub 2} sequestration candidate technologies that propose long-term storage, mineral sequestration provides permanent disposal by forming geologically stable mineral carbonates. Carbonation of the widely occurring mineral olivine (e.g., forsterite, Mg{sub 2}SiO{sub 4}) is a large-scale sequestration process candidate for regional implementation, which converts CO{sub 2} into the environmentally benign mineral magnesite (MgCO{sub 3}). The primary goal is cost-competitive process development. As the process is exothermic, it inherently offers low-cost potential. Enhancing carbonation reactivity is key to economic viability. Recent studies at the U.S. DOE Albany Research Center have established that aqueous-solution carbonation using supercritical CO{sub 2} is a promising process; even without olivine activation, 30-50% carbonation has been achieved in an hour. Mechanical activation (e.g., attrition) has accelerated the carbonation process to an industrial timescale (i.e., near completion in less than an hour), at reduced pressure and temperature. However, the activation cost is too high to be economical and lower cost pretreatment options are needed. Herein, we report our second year progress in exploring a novel approach that offers the potential to substantially enhance carbonation reactivity while bypassing pretreatment activation. As our second year progress is intimately related to our earlier work, the report is presented in that context to provide better overall understanding of the progress made. We have discovered that robust silica-rich passivating layers form on the olivine surface during carbonation. As carbonation proceeds, these passivating layers thicken, fracture and eventually exfoliate, exposing fresh olivine surfaces during rapidly-stirred/circulating carbonation. We are exploring the mechanisms that govern carbonation reactivity and the impact that (i) modeling/controlling the slurry fluid-flow conditions, (ii) varying the aqueous ion species/size and concentration (e.g., Li{sup +}, ...
Date: June 21, 2006
Creator: McKelvy, Michael J.; Chizmeshya, Andrew V. G.; Squires, Kyle; Carpenter, Ray W. & Bearat, Hamdallah
Partner: UNT Libraries Government Documents Department

A Novel Approach to Mineral Carbonation: Enhancing Carbonation While Avoiding Mineral Pretreatment Process Cost

Description: Known fossil fuel reserves, especially coal, can support global energy demands for centuries to come, if the environmental problems associated with CO{sub 2} emissions can be overcome. Unlike other CO{sub 2} sequestration candidate technologies that propose long-term storage, mineral sequestration provides permanent disposal by forming geologically stable mineral carbonates. Carbonation of the widely occurring mineral olivine (e.g., forsterite, Mg{sub 2}SiO{sub 4}) is a large-scale sequestration process candidate for regional implementation, which converts CO{sub 2} into the environmentally benign mineral magnesite (MgCO{sub 3}). The primary goal is cost-competitive process development. As the process is exothermic, it inherently offers low-cost potential. Enhancing carbonation reactivity is key to economic viability. Recent studies at the U.S. DOE Albany Research Center have established that aqueous-solution carbonation using supercritical CO{sub 2} is a promising process; even without olivine activation, 30-50% carbonation has been achieved in an hour. Mechanical activation (e.g., attrition) has accelerated the carbonation process to an industrial timescale (i.e., near completion in less than an hour), at reduced pressure and temperature. However, the activation cost is too high to be economical and lower cost pretreatment options are needed. We have discovered that robust silica-rich passivating layers form on the olivine surface during carbonation. As carbonation proceeds, these passivating layers thicken, fracture and eventually exfoliate, exposing fresh olivine surfaces during rapidly-stirred/circulating carbonation. We are exploring the mechanisms that govern carbonation reactivity and the impact that (1) modeling/controlling the slurry fluid-flow conditions, (2) varying the aqueous ion species/size and concentration (e.g., Li+, Na+, K+, Rb+, Cl-, HCO{sub 3}{sup -}), and (3) incorporating select sonication offer to enhance exfoliation and carbonation. Thus far, we have succeeded in nearly doubling the extent of carbonation observed compared with the optimum procedure previously developed by the Albany Research Center. Aqueous carbonation reactivity was found to be a strong function of ...
Date: June 21, 2007
Creator: Chizmeshya, Andrew V. G.; McKelvy, Michael J.; Squires, Kyle; Carpenter, Ray W. & Bearat, Hamdallah
Partner: UNT Libraries Government Documents Department

Dual Phase Membrane for High Temperature CO2 Separation

Description: Dual-phase membranes consisting of stainless steel supports infiltrated with molten carbonate have been shown to be selective to CO{sub 2} at high temperatures (400-650 C). However, over time at high temperatures, the formation of iron oxides on the surface of the stainless steel supports render the membranes ineffective. This report details synthesis and characteristics of dual-phase carbonate membrane with an oxidation resistant perovskite type ceramic (lanthanum-strontium-cobaltite-iron; LSCF) support. Porous LSCF supports were prepared from its powder synthesized by the citrate method. Both steady state permeation and mercury porosimetry confirmed that the LSCF membrane sintered at 900 C has pores large enough to absorb molten carbonate, yet small enough to retain the molten carbonate under high pressure conditions. Results of XRD analysis have shown that LSCF and the molten carbonate mixture do not react with each other at temperatures below 700 C. Four-point method conductivity tests indicate that the support material has sufficiently high electronic conductivity for this application. Li-Na-K carbonate was coated to the porous LSCF support by a liquid infiltration method. Helium permeance of the support before and after infiltration of molten carbonate are on the order of 10{sup -6} and 10{sup -10} moles/m{sup 2} {center_dot} Pa {center_dot} s respectively, indicating that the molten carbonate is able to sufficiently infiltrate the membrane. Preliminary high temperature permeation experiments indicate that the membrane does separate CO{sub 2} in the presence of O{sub 2}, with a maximum flux of 0.623 ml/cm{sup 2} {center_dot} min obtained at 850 C.
Date: September 29, 2006
Creator: Lin, Jerry Y.S. & Anderson, Matthew
Partner: UNT Libraries Government Documents Department

Dual Phase Membrane for High Temperature CO2 Separation

Description: This project aimed at synthesis of a new inorganic dual-phase carbonate membrane for high temperature CO{sub 2} separation. Metal-carbonate dual-phase membranes were prepared by the direct infiltration method and the synthesis conditions were optimized. Permeation tests for CO{sub 2} and N{sub 2} from 450-750 C showed very low permeances of those two gases through the dual-phase membrane, which was expected due to the lack of ionization of those two particular gases. Permeance of the CO{sub 2} and O{sub 2} mixture was much higher, indicating that the gases do form an ionic species, CO{sub 3}{sup 2-}, enhancing transport through the membrane. However, at temperatures in excess of 650 C, the permeance of CO{sub 3}{sup 2-} decreased rapidly, while predictions showed that permeance should have continued to increase with temperature. XRD data obtained from used membrane indicated that lithium iron oxides formed on the support surface. This lithium iron oxide layer has a very low conductivity, which drastically reduces the flow of electrons to the CO{sub 2}/O{sub 2} gas mixture; thus limiting the formation of the ionic species required for transport through the membrane. These results indicated that the use of stainless steel supports in a high temperature oxidative environment can lead to decreased performance of the membranes. This revelation created the need for an oxidation resistant support, which could be gained by the use of a ceramic-type membrane. Work was extended to synthesize a new inorganic dual-phase carbonate membrane for high temperature CO{sub 2} separation. Helium permeance of the support before and after infiltration of molten carbonate are on the order of 10{sup -6} and 10{sup -10} moles/m{sup 2} {center_dot} Pa {center_dot} s respectively, indicating that the molten carbonate is able to sufficiently infiltrate the membrane. It was found that La{sub 0.6}Sr{sub 0.4}Co{sub 0.8}Fe{sub 0.2}O{sub 3-{delta}} (LSCF) was a suitable candidate ...
Date: June 30, 2007
Creator: Lin, Jerry
Partner: UNT Libraries Government Documents Department

ENHANCING THE ATOMIC-LEVEL UNDERSTANDING OF CO2 MINERAL SEQUESTRATION MECHANISMS VIA ADVANCED COMPUTATIONAL MODELING

Description: Fossil fuels currently provide 85% of the world's energy needs, with the majority coming from coal, due to its low cost, wide availability, and high energy content. The extensive use of coal-fired power assumes that the resulting CO2 emissions can be vented to the atmosphere. However, exponentially increasing atmospheric CO2 levels have brought this assumption under critical review. Over the last decade, this discussion has evolved from whether exponentially increasing anthropogenic CO2 emissions will adversely affect the global environment, to the timing and magnitude of their impact. A variety of sequestration technologies are being explored to mitigate CO2 emissions. These technologies must be both environmentally benign and economically viable. Mineral carbonation is an attractive candidate technology as it disposes of CO2 as geologically stable, environmentally benign mineral carbonates, clearly satisfying the first criteria. The primary challenge for mineral carbonation is cost-competitive process development. CO2 mineral sequestration--the conversion of stationary-source CO2 emissions into mineral carbonates (e.g., magnesium and calcium carbonate, MgCO3 and CaCO3)--has recently emerged as one of the most promising sequestration options, providing permanent CO2 disposal, rather than storage. In this approach a magnesium-bearing feedstock mineral (typically serpentine or olivine; available in vast quantities globally) is specially processed and allowed to react with CO2 under controlled conditions. This produces a mineral carbonate which (1) is environmentally benign, (2) already exists in nature in quantities far exceeding those that could result from carbonating the world's known fossil fuel reserves, and (3) is stable on a geological time scale. Minimizing the process cost via optimization of the reaction rate and degree of completion is the remaining challenge. As members of the DOE/NETL managed National Mineral Sequestration Working Group we have already significantly improved our understanding of mineral carbonation. Group members at the Albany Research Center have recently shown that carbonation of olivine ...
Date: March 1, 2006
Creator: Chizmeshya, A.V.G.; McKelvy, M.J.; Wolf, G.H.; Carpenter, R.W.; Gormley, D.A.; Diefenbacher, J.R. et al.
Partner: UNT Libraries Government Documents Department

Topic 5: Power System Operation and Planning for Enhanced Wind Generation Penetration

Description: This project dealt with the development of a range of educational resources dealing with wind energy and wind energy integration in the electric grid. These resources were developed for a variety of audiences including; a) high school student, b) undergraduate electrical engineering students, c) graduate electrical engineering students, and d) practicing engineers in industry. All the developed material is available publicly and the courses developed are being taught at the two participating universities, Arizona State University and Iowa State University.
Date: August 31, 2012
Creator: Vittal, Vijay; Heydt, Gerald T; Ayyanar, Raja; McCalley, James D; Ajjarapu, V & Aliprantis, Dionysios
Partner: UNT Libraries Government Documents Department

PS2004 Light-harvesting Systems Workshop

Description: This special issue of the international scientific research journal Photosynthesis Research consists of 25 original peer-reviewed contributions from participants in the PS 2004 Lisht-Harvesting Systems Workshop. This workshop was held from 26-29, 2004 at Hotel Le Chantecler, Sainte-Adele, Quebec, Canada. The workshop was a satellite meeting of the XIII International Congress on Photosynthesis held August 29-September 3, 2004 in Montreal, Canada. The workshope dealt with all types of photosynthetic antenna systems and types of organisms, including anoxygenic photosynthetic bacteria, cyanobacteria, algae and higher plants, as well as in vitro studies of isolated pigments. This collection of papers is a good representation of the highly interdisciplinary nature of modern research on photosynthetic antenna complexes, utilizing techniques of advanced spectroscopy, biochemistry, molecular biology, synthetic chemistry and structural determination to understand these diverse and elegant molecular complexes.
Date: November 1, 2005
Creator: Blankenship, Robert E.
Partner: UNT Libraries Government Documents Department

A Combined Genetic, Biochemical, and Biophysical Analysis of the A1 Phylloquinone Binding Site of Photosystem I from Green Algae

Description: This project has resulted in the increase in our understanding of how proteins interact with and influence the properties of bound cofactors. This information is important for several reasons, including providing essential information for the re-engineering of biological molecules, such as proteins, for either improved function or entirely new ones. In particular, we have found that a molecule, such as the phylloquinone used in Photosystem I (PS1), can be made a stronger electron donor by placing it in a hydrophobic environment surrounded by negative charges. In addition, the protein is constrained in its interactions with the phylloqinone, in that it must bind the cofactor tightly, but not in such a way that would stabilize the reduced (negatively-charged) version of the molecule. We have used a combination of molecular genetics, in order to make specific mutations in the region of the phylloquinone, and an advanced form of spectroscopy capable of monitoring the transfer of electrons within PS1 using living cells as the material. This approach turned out to produce a significant savings in time and supplies, as it allowed us to focus quickly on the mutants that produced interesting effects, without having to go through laborious purification of the affected proteins. We followed up selected mutants using other spectroscopic techniques in order to gain more specialized information. In addition to the main project funded by this work, this grant supported several related side-projects that also increased our understanding about related issues.
Date: December 17, 2011
Creator: Redding, Kevin E.
Partner: UNT Libraries Government Documents Department