191 Matching Results

Search Results

Advanced search parameters have been applied.

Joining of Ion Transport Membranes Using a Novel Transient Liquid Phase Process

Description: The feasibility of a novel transient liquid phase (TLP) joining method has been demonstrated in joining La{sub 0.9}Ca{sub 0.1}FeO{sub 3} materials. Metal oxide powders were processed to form the TLP compositions which were used in the joining process. The method has been successful in producing joint interfaces that effectively disappear, as they are the same material and have the same properties as the joined parts. The feasibility of the method has been demonstrated for a single system, but many systems where the method can potentially be applied have been identified.
Date: August 30, 2006
Creator: Butt, Darryl P.
Partner: UNT Libraries Government Documents Department

Identifying Calcium Channels and Porters in Plant Membranes

Description: The overall objectives of the proposal submitted in 6/90 was to understand how Ca was transported across plant membranes, and how these transport pathways were regulated. Ca participates in many cellular processes, including the transduction of hormonal and environmental signals, secretion, and protein folding. These processes depend on the coordination of passive Ca fluxes via channels and active Ca pumps; however these transport pathways are poorly understood in plants. We had, therefore, proposed to identify and characterize Ca transport proteins, such as the inositol-1 ,4,5-trisphosphate (IP3)-sensitive Ca channels and Ca pumps. We have had difficulties characterizing and cloning the IP3-sensitive Ca channel, but have made considerable progress on the biochemical characterization, and partial purification of a 120 kD Ca-pumping ATPase. We have begun to determine the structure of Ca pumps by molecular cloning and have already obtained a partial cDNA with features characteristic of Ca pumps.
Date: April 1, 1998
Creator: Sze, Heven
Partner: UNT Libraries Government Documents Department


Description: Under the commonly employed experimental conditions of a significant upstream concentration of H and c{sub H} {approx} 0 downstream, expressions are given for obtaining the concentration-independent D*{sub H} from the concentration dependent D{sub H} employing the known non-ideality. A procedure is given for determining the concentration profile for a given upstream concentration for an alloy where the non-ideality is known as a function of H concentration. For the Pd{sub 0.81}Ag{sub 0.19} alloy (423 K) the nonideality, f(r)<1 decreases the flux but for alloys where the non-ideality is in the opposite direction, f(r)>1, the flux will be greater which would be an advantage for the experimental purification of H{sub 2}.
Date: July 13, 2006
Creator: Shanahan, K; Ted B. Flanagan, T & D. Wang, D
Partner: UNT Libraries Government Documents Department

Subtask 1.15-Passive Diffusion Sample Bags Made from Expanded Polytetrafluorethylene (ePTFE) to Measure VOC Concentrations in Groundwater

Description: With laboratory testing of expanded polytetrafluoroethylene (ePTFE) membranes complete, collected data support that volatile organic compound (VOC) molecules will readily diffuse across ePTFE membranes. Membrane samples, supplied by BHA Technologies (GE Osmonics), were tested to determine diffusion rates for VOCs in groundwater. Tests were conducted using membranes with two different pore sizes, with and without thermally laminated spun bond backing, and multiple concentrations of contaminated groundwater. Results suggest that typical residence times associated with traditional samplers constructed of polyethylene (2 weeks) can be reduced by 1 week using ePTFE membranes (reducing project costs) and that VOCs will diffuse more readily at lower temperatures (2.2-3.3 C) across ePTFE materials.
Date: August 1, 2006
Creator: Botnen, Barry W.
Partner: UNT Libraries Government Documents Department


Description: H diffusion constants, D{sub H}, have been obtained from steady-state fluxes across Pd membranes with the downstream side maintained at p{sub H2} {approx} 0. Good linearity of plots of H flux versus (1/d), where d is the thickness, attests to the H permeation being bulk diffusion controlled in this temperature (423 to 523K) and p{sub H2} range ({le} 0.2 MPa). D{sub H} values have been determined at constant p{sub up} and also at constant (H/Pd)=r conditions. H fluxes through Pd membranes with three different surface treatments have been investigated (polished (un-oxidized), oxidized, and palladized) in order to determine the effects of these pretreatments. The palladized and oxidized membranes give similar D{sub H} values but the polished membranes give values about 12% lower. For diffusion in a concentration gradient D{sub H}*(c{sub H}/RT)(d{mu}{sub H}/dx) is the more proper description, where c{sub H} is the H concentration, rather than D{sub H}(dc{sub H}/dx) where D{sub H} and D{sub H}* are the concentration-dependent and independent diffusion constants. D{sub H}* can be obtained from D{sub H} using the thermodynamic factor, D{sub H}(r) = D{sub H}*({partial_derivative}lnp{sub H2}{sup 1/2}/{partial_derivative}lnr){sub T} = D{sub H}*f(r). In the commonly employed situation where there is a large difference in concentrations between the upstream and downstream sides of a membrane, the thermodynamic factor varies with distance through the membrane and this should be allowed for in obtaining D{sub H}*. Procedures are given and utilized for using D{sub H}(c{sub H}) to determine D{sub H}* values when there is a large concentration gradient through the membrane. Activation energies for diffusion, E{sub D}(c{sub H}), have been determined. E{sub D} is found to increase with c{sub H} which can be attributed to the thermodynamic factor. D{sub H}* values have been found to increase with H content.
Date: March 9, 2007
Creator: Shanahan, K
Partner: UNT Libraries Government Documents Department

A bio-synthetic interface for discovery of viral entry mechanisms.

Description: Understanding and defending against pathogenic viruses is an important public health and biodefense challenge. The focus of our LDRD project has been to uncover the mechanisms enveloped viruses use to identify and invade host cells. We have constructed interfaces between viral particles and synthetic lipid bilayers. This approach provides a minimal setting for investigating the initial events of host-virus interaction - (i) recognition of, and (ii) entry into the host via membrane fusion. This understanding could enable rational design of therapeutics that block viral entry as well as future construction of synthetic, non-proliferating sensors that detect live virus in the environment. We have observed fusion between synthetic lipid vesicles and Vesicular Stomatitis virus particles, and we have observed interactions between Nipah virus-like particles and supported lipid bilayers and giant unilamellar vesicles.
Date: September 1, 2010
Creator: Gutzler, Mike; Maar, Dianna; Negrete, Oscar; Hayden, Carl C.; Sasaki, Darryl Yoshio; Stachowiak, Jeanne C. et al.
Partner: UNT Libraries Government Documents Department

Access in nanoporous solids. Final Report for June 30, 1997 - May 31, 2000

Description: This is an application of techniques of molecular theory to the study of nanostructures build on planar substrates and the face of membranes, with the ultimate goal of modifying their equilibrium and transport behavior. The work is focused on the mechanism for adsorption or deposition and how various regimes can be achieved by changing the rate of adsorption relative to characteristic diffusion and reaction time scales.
Date: July 18, 2003
Creator: Glandt, Eduardo D.
Partner: UNT Libraries Government Documents Department

Transport properties of dense fluid mixtures using nonequilibrium molecular dynamics. Final report, September 15, 1987--March 14, 1997

Description: Computer Simulation Studies were carried out using the method of equilibrium and nonequilibrium molecular dynamics (NEMD) to examine a wide range of transport processes in both fluids and fluid mixtures. This included testing a wide range of mixing rules for thermal conductivity and viscosity. In addition a method was developed to calculate the internal rotational contributions to thermal conductivity and the accuracy of current methods for predicting these contributions were examined. These comparisons were then used to suggest possible ways of improving these theories. The method of NEMD was also used to examine the critical enhancements of thermal conductivity. Finally, molecular simulations were carried out to study the various transport coefficients of fluids confined by membranes, as well as important transport processes such as osmosis, and reverse osmosis.
Date: May 1, 1997
Creator: Murad, S.
Partner: UNT Libraries Government Documents Department

Mathematical modeling of liquid/liquid hollow fiber membrane contactor accounting for interfacial transport phenomena: Extraction of lanthanides as a surrogate for actinides

Description: This report is divided into two parts. The second part is divided into the following sections: experimental protocol; modeling the hollow fiber extractor using film theory; Graetz model of the hollow fiber membrane process; fundamental diffusive-kinetic model; and diffusive liquid membrane device-a rigorous model. The first part is divided into: membrane and membrane process-a concept; metal extraction; kinetics of metal extraction; modeling the membrane contactor; and interfacial phenomenon-boundary conditions-applied to membrane transport.
Date: August 4, 1994
Creator: Rogers, J. D.
Partner: UNT Libraries Government Documents Department

Testing of a benchscale Reverse Osmosis/Coupled Transport system for treating contaminated groundwater

Description: The Reverse Osmosis/Coupled Transport process is a innovative means of removing radionuclides from contaminated groundwater at the Hanford Site. Specifically, groundwater in the 200 West Area of the Hanford Site has been contaminated with uranium, technetium, and nitrate. Investigations are proceeding to determine the most cost effective method to remove these contaminants. The process described in this paper combines three different membrane technologies (reverse osmosis, coupled transport, and nanofiltration to purify the groundwater while extracting and concentrating uranium, technetium, and nitrate into separate solutions. This separation allows for the future use of the radionuclides, if needed, and reduces the amount of waste that will need to be disposed of. This process has the potential to concentrate the contaminants into solutions with volumes in a ratio of 1/10,000 of the feed volume. This compares to traditional volume reductions of 10 to 100 for ion exchange and stand-alone reverse osmosis. The successful demonstration of this technology could result in significant savings in the overall cost of decontaminating the groundwater.
Date: January 1, 1994
Creator: Hodgson, K.M.; Lunsford, T.R. & Panjabi, G.
Partner: UNT Libraries Government Documents Department

Protein kinesis: The dynamics of protein trafficking and stability

Description: The purpose of this conference is to provide a multidisciplinary forum for exchange of state-of-the-art information on protein kinesis. This volume contains abstracts of papers in the following areas: protein folding and modification in the endoplasmic reticulum; protein trafficking; protein translocation and folding; protein degradation; polarity; nuclear trafficking; membrane dynamics; and protein import into organelles.
Date: December 31, 1995
Partner: UNT Libraries Government Documents Department

Plant, cell, and molecular mechanisms of abscisic-acid regulation of stomatal apertures. In vivo phosphorylation of phosphoenolpyruvate carboxylase in guard cells of Vicia faba L. is enhanced by fusicoccin and suppressed by abscisic acid

Description: Plants regulate water loss and CO{sub 2} gain by modulating the aperture sizes of stomata that penetrate the epidermis. Aperture size itself is increased by osmolyte accumulation and consequent turgor increase in the pair of guard cells that flank each stoma. Guard-cell phosphoenolpyruvate carboxylase, which catalyzes the regulated step leading to malate synthesis, is crucial for charge and pH maintenance during osmolyte accumulation. Regulation of this cytosolic enzyme by effectors is well documented, but additional regulation by posttranslational modification is predicted by the alteration of PEPC kinetics during stomatal opening. In this study, the authors have investigated whether this alteration is associated with the phosphorylation status of this enzyme. Using sonicated epidermal peels (isolated guard cells) pre-loaded with {sub 32}PO{sub 4}, the authors induced stomatal opening and guard-cell malate accumulation by incubation with 5 {micro}M fusicoccin (FC). In corroboratory experiments, guard cells were incubated with 5 {micro}M fusicoccin (FC). In corroboratory experiments, guard cells were incubated with the FC antagonist, 10 {micro}M abscisic acid (ABA). The phosphorylation status of PEPC was assessed by immunoprecipitation, electrophoresis, immunoblotting, and autoradiography. PEPC was phosphorylated when stomata were stimulated to open, and phosphorylation was lessened by incubation with ABA.
Date: December 31, 1996
Creator: Du, Z.; Aghoram, K. & Outlaw, W.H. Jr.
Partner: UNT Libraries Government Documents Department

Plant, cell, and molecular mechanisms of abscisic-acid regulation of stomatal apertures. A new mechanism for the regulation of stomatal-aperture size in intact leaves: Accumulation of mesophyll-derived sucrose in the guard-cell wall of Vicia faba L.

Description: At various times after pulse labeling Vicia faba L. leaflets with {sup 14}CO{sub 2}, whole-leaf pieces and rinsed epidermal peels were harvested and subsequently processed for histochemical analysis. Cells dissected from whole leaf retained apoplastic contents whereas those from rinsed peels contained only cytoplastic contents. Sucrose specific radioactivity peaked in palisade cells, 111 GBq{center_dot}mol{sup {minus}1}, at 20 min. In contrast, the {sup 14}C content and sucrose specific radioactivity were very low in guard cells for 20 min, implying little CO{sub 2} incorporation; both then peaked at 40 min. The guard-cell apoplast had a high maximum sucrose specific radioactivity and a high sucrose influx rate. These and other comparisons implied the presence of (a) multiple sucrose pools in mesophyll cells, (b) a localized mesophyll-apoplast region that exchanges with phloem and stomata, and (c) mesophyll-derived sucrose in guard-cell walls sufficient to diminish stomatal opening by {approximately} 4 {micro}m. Factors expected to enhance sucrose accumulation in guard-cell walls are (a) high transpiration rate, which closes stomata, and (b) high apoplastic sucrose concentration, which is elevated when mesophyll-sucrose efflux exceeds translocation. Therefore, multiple physiological factors are integrated in the attenuation of stomatal-aperture size by this previously unrecognized mechanism.
Date: December 31, 1996
Creator: Lu, P.; Outlaw, W.H. Jr.; Smith, B.G. & Freed, G.A.
Partner: UNT Libraries Government Documents Department

Unique applications of solvent removal in inductively coupled plasma mass spectrometry

Description: Inductively coupled plasma mass spectrometry (ICP-MS) is the technique of choice for rapid, high precision, semiquantitative elemental and isotopic analysis for over 70 elements. Less than 20 years after the first mass spectrum was obtained by ICP-MS, this technique has applications in clinical chemistry, geochemistry, the semiconductor industry, the nuclear industry, environmental chemistry, and forensic chemistry. The determination of many elements, though, by ICP-MS is complicated by spectral interferences from background species, interelement spectral overlaps, and polyatomic ions of matrix elements. The emphasis of this thesis is the unique applications of solvent removal using cryogenic and membrane desolvation. Chapter 1 is a general introduction providing background information concerning the need for these methods and some information about the methods themselves. Chapter 5 discusses general conclusions and general observations pertaining to this work. Chapters 2, 3, and 4 have been processed separately for inclusion on the database. Chapter 2 describes a method to screen urine samples for vanadium using cryogenic desolvation. Chapter 3 compares solvent removal by cryogenic and membrane desolvation. Chapter 4 describes the use of cool plasma conditions for the determination of potassium in the presence of excess sodium by ICP-MS.
Date: January 10, 1997
Creator: Minnich, M.
Partner: UNT Libraries Government Documents Department

Low-quality natural gas sulfur removal/recovery

Description: A significant fraction of U.S. natural gas reserves are subquality due to the presence of acid gases and nitrogen; 13% of existing reserves (19 trillion cubic feed) may be contaminated with hydrogen sulfide. For natural gas to be useful as fuel and feedstock, this hydrogen sulfide has to be removed to the pipeline specification of 4 ppm. The technology used to achieve these specifications has been amine, or similar chemical or physical solvent, absorption. Although mature and widely used in the gas industry, absorption processes are capital and energy-intensive and require constant supervision for proper operation. This makes these processes unsuitable for treating gas at low throughput, in remote locations, or with a high concentration of acid gases. The U.S. Department of Energy, recognizes that exploitation of smaller, more sub-quality resources will be necessary to meet demand as the large gas fields in the U.S. are depleted. In response to this need, Membrane Technology and Research, Inc. (MTR) has developed membranes and a membrane process for removing hydrogen sulfide from natural gas. During this project, high-performance polymeric thin-film composite membranes were brought from the research stage to field testing. The membranes have hydrogen sulfide/methane selectivities in the range 35 to 60, depending on the feed conditions, and have been scaled up to commercial-scale production. A large number of spiral-wound modules were manufactured, tested and optimized during this project, which culminated in a field test at a Shell facility in East Texas. The short field test showed that membrane module performance on an actual natural gas stream was close to that observed in the laboratory tests with cleaner streams. An extensive technical and economic analysis was performed to determine the best applications for the membrane process. Two areas were identified: the low-flow-rate, high-hydrogen-sulfide-content region and the high-flow-rate, high-hydrogen-sulfide-content region. In both ...
Date: January 29, 1998
Creator: Amo, K.; Baker, R.W.; Helm, V.D.; Hofmann, T.; Lokhandwala, K.A.; Pinnau, I. et al.
Partner: UNT Libraries Government Documents Department


Description: Increased environmental regulations will require utility boilers to reduce NO{sub x} emissions to less than 0.15lb/MMBtu in the near term. Conventional technologies such as Selective Catalytic Reduction (SCR) and Selective Non-Catalytic Reduction (SNCR) are unable to achieve these lowered emission levels without substantially higher costs and major operating problems. Oxygen enhanced combustion is a novel technology that allows utilities to meet the NO{sub x} emission requirements without the operational problems that occur with SCR and SNCR. Furthermore, oxygen enhanced combustion can achieve these NO{sub x} limits at costs lower than conventional technologies. The objective of this program is to demonstrate the use of oxygen enhanced combustion as a technical and economical method of meeting the EPA State Implementation Plan for NO{sub x} reduction to less than 0.15lb/MMBtu for a wide range of boilers and coal. The oxygen enhanced coal combustion program (Task 1) focused this quarter on the specific objective of exploration of the impact of oxygen enrichment on NO{sub x} formation utilizing small-scale combustors for parametric testing. Research efforts toward understanding any limitations to the applicability of the technology to different burners and fuels such as different types of coal are underway. The objective of the oxygen transport membrane (OTM) materials development program (Task 2.1) is to ascertain a suitable material composition that can be fabricated into dense tubes capable of producing the target oxygen flux under the operating conditions. This requires that the material have sufficient oxygen permeation resulting from high oxygen ion conductivity, high electronic conductivity and high oxygen surface exchange rate. The OTM element development program (Task 2.2) objective is to develop, fabricate and characterize OTM elements for laboratory and pilot reactors utilizing quality control parameters to ensure reproducibility and superior performance. A specific goal is to achieve a material that will sinter to desired density ...
Date: July 1, 2000
Creator: Bool, Lawrence E.; Chen, Jack C. & Thompson, David R.
Partner: UNT Libraries Government Documents Department

Experimental Support for a Predictive Osmotic Model of Clay Membranes

Description: Osmosis has been cited as a mechanism for explaining anomalously high fluid pressures in the subsurface. Clays and shales act as membranes, and osmotic flux across these units may result in pressures sufficiently high to explain these anomalies. The theoretical osmotic pressures as calculated solely from solution properties can be quite large; however, it is not yet resolved whether these geologic membranes are sufficiently ideal to generate such pressures.
Date: August 29, 2001
Creator: Fritz, S.J.
Partner: UNT Libraries Government Documents Department


Description: This quarterly technical progress report will summarize work accomplished for the Program through the second quarter July--September 2000 in the following task areas: Task 1-Oxygen Enhanced Combustion, Task 2-Oxygen Transport Membranes and Task 4-Program Management. The program is proceeding in accordance with the objectives for the first year. OTM tube characterization is well underway, the design and assembly of the high pressure permeation test facility is complete and the facility will be in full operation during the next quarter. Combustion testing has been initiated at both the University of Arizona and Praxair. Testing at the University of Arizona has experienced some delays; steps have been take to get the test work back on schedule. Completion of the first phase of the testing is expected in next quarter. Combustion modeling has been started at both REI and Praxair, preliminary results are expected in the next quarter.
Date: October 1, 2000
Creator: Bool, Lawrence E.; Chen, Jack C. & Thompson, David R.
Partner: UNT Libraries Government Documents Department


Description: The various processes of DNA uptake by cells can be categorized as: viral DNA entry, conjugation, or transformation. Within each category, a variety of mechanisms have been found. However, considerable similarities occur among the different mechanisms of conjugation and, especially, transformation. All of these natural mechanisms of DNA transfer are quite elaborate and involve multiple protein components, as the case may be, of the virus, the donor cell, and the recipient cell. The mechanisms of viral infection and conjugation will be discussed mainly with respect to their relevance to transformation.
Date: September 7, 1999
Creator: LACKS,S.A.
Partner: UNT Libraries Government Documents Department

Molecular dissection of the cellular mechanisms involved in nickel hyperaccumulation. 1997 annual progress report

Description: 'Phytoremediation, the use of plants for environmental cleanup of pollutants, including toxic metals, holds the potential to allow the economic restoration of heavy metal and radionuclide contaminated sites. A number of terrestrial plants are known to naturally accumulate high levels of metals in their shoots (1--2% dry weight), and these plants have been termed metal-hyperaccumulators. Clearly, the genetic traits that determine metal-hyperaccumulation offers the potential for the development of practical phytoremediation processes. The long-term objective is to rationally design and generate plants ideally suited for phytoremediation using this unique genetic material. Initially, the strategy will focus on isolating and characterizing the key genetic information needed for expression of the metal-hyperaccumulation phenotype. Recently, histidine has been shown to play a major role in Ni hyperaccumulation. Based on this information the authors propose to investigate, at the molecular level, the role of histidine biosynthesis in Ni hyperaccumuIation in Thlaspi goesingense, a Ni hyperaccumulator species.'
Date: October 28, 1997
Creator: Salt, D. E.
Partner: UNT Libraries Government Documents Department

Molecular characterization of a novel heavy metal uptake transporter from higher plants and its potential for use in phytoremediation. 1998 annual progress report

Description: 'Soils and waters contaminated with high levels of heavy metals such as Cadmium, Lead and Copper are detrimental to human and environmental health. Many human disorders have been attributed to environmental contamination by heavy metals. Removal of heavy metals from highly contaminated sites is therefore a very costly but necessary process that is currently being pursued. Recent research in several laboratories indicates that uptake of heavy metals into plants via the root system may provide a cost-effective approach for decontamination of certain heavy metal-laden soils and waters. Several mechanisms have been identified, which allow detoxification in the cytosol and vacuoles of plants. However, the molecular biological mechanisms by which heavy metals are transported from soils across the plasma membrane into roots have remained largely unknown. In recent research, the laboratory has cloned a cation uptake transporter cDNA from plants. Yeast cells expressing this cDNA show enhanced uptake of calcium and cadmium. The proposed research is testing the transport of toxic and nutrient metals by the encoded protein.'
Date: June 1, 1998
Creator: Schroeder, J.I.
Partner: UNT Libraries Government Documents Department