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ZIRCONIUM HAZARDS RESEARCH. Summary Report No. 3655 for September 1, 1956 to August 31, 1957

Description: The sensitivity characteristics of a variety of Zr samples such as sponge, scrap, powder and process materials were studicd. Of particular interest was the determination of the relative seasitivity of these materials to such stimuli as impact, friction, electrostatic discharge, and heat. A study of the zirconium--water reaction at relatively low temperature was initiated. In general, scrap and sponge were relatively insensitive to impact. Only one proeess material, the distillation residue, exhibited any pyrophoric tendencies in this test. As anticipated, the majority of the samples tested were somewhat sensitive to friction. The dry distillation residues and Ca-reduced Zr powders, which had frequency rates of 100% in most cases, were the most sensitive of all the samples tested. Sponge was moderately sensitive, but the variation in sensitivity could not be correlated with either particle size or chemical impurities. Neither the Zr or Zircaloy scraps in the form of chips and turnings were very sensitive. The maierial which proved to be most insensitive to friction was the vapor phase residue. A frequency rate of zero was noted for all the samples tested. Using a condenser discharge to heat wire samples rapidly in aa inert atmosphere to a temperature well above the melting point, an attempt was made to determine the effect of stress on the pyrophoricity of Zr. It was found that the minimum energy requirements for fragmentation of a pure Zr wire are reduced by the application of mechanically induced stresses and bv the addition of chemical impurities such as C and/or H/sub 2/, Although the experimental phase of the study of the zirconium--water reaction has been barely- initiated, there is some evidence to indicate thai pre-treatment of a sample with N, at elevated temperatures does promote the oxidation reaction with steam. (auth)
Date: August 31, 1957
Creator: Herickes, J.A.; Richardson, P.A.; Weiss, M. & Gelernter, G.
Partner: UNT Libraries Government Documents Department

Controlling incipient oxidation of pyrite for improved rejection. Technical progress report for the ninth quarter, October 1--December 31, 1994

Description: The major objectives of this work are (1) to determine the Eh-pH conditions under which pyrite is stable, (2) to determine the mechanism of the initial stages of pyrite oxidation, and (3) to determine if the semi-conducting properties of pyrite effects its oxidation behavior. It is known that moderate oxidation of pyrite produces a hydrophobic surface product. This hydrophobic product makes it extremely difficult to depress pyrite in coal flotation circuits. The eventual objective of this work is to prevent pyrite oxidation in order to better depress pyrite in coal flotation circuits. It has been shown that by holding the potential of pyrite at its stable potential during fracture, pyrite undergoes neither oxidation nor reduction. It has also been found that fresh pyrite surfaces created by fracture in an electrochemical begin to oxidize at potentials that are about 200 mV more negative than the potentials reported in the literature for pyrite oxidation. This report period, electrochemical impedance spectroscopy (EIS) studies were continued. As discussed in the seventh quarterly progress report, the impedance of pyrite does not show the characteristics expected for either semi-conducting or metallic electrodes. Additional studies were conducted to confirm the anomalous impedance behavior. For this purpose, freshly fractured surfaces were progressively polished on 600 and 1,200 grit silicon carbide paper, and with 0.3 {micro} {alpha}-alumina and 0.05 {micro} {gamma}-alumina micropolish. Polishing is known to introduce defects in the lattice structure of semi-conducting electrodes and it was anticipated that the defects would effect the interfacial capacitance.
Date: July 1, 1995
Creator: Yoon, R.H. & Richardson, P.E.
Partner: UNT Libraries Government Documents Department

Controlling incipient oxidation of pyrite for improved rejection. Eighth quarterly technical progress report, July 1, 1994--September 30, 1994

Description: The major objectives of this work are (1) to determine the Eh-pH conditions under which pyrite is stable, (2) to determine the mechanism of the initial stages of pyrite oxidation and (3) to determine if the semi-conducting properties of pyrite effects its oxidation behavior. It is known that moderate oxidation of pyrite produces a hydrophobic surface product. This hydrophobic product makes it extremely difficult to depress pyrite in coal flotation circuits. The eventual objective of this work is to prevent pyrite oxidation in order to better depress pyrite in coal flotation circuits. In this work clean, unoxidized pyrite surfaces are being produced by fracturing pyrite electrodes in an electrochemical cell. It has been shown that pyrite assumes a unique potential referred to as the ``stable potential`` at the instance it is fractured and that this potential is several hundred millivolts more negative than the steady state mixed potential of pyrite. It has also been shown that by holding the potential of pyrite at its stable potential during fracture, pyrite undergoes neither oxidation nor reduction. It has also been found that fresh pyrite surfaces created by fracture in an electrochemical begin to oxidize at potentials that are about 200 mV more negative than the potentials reported in the literature for pyrite oxidation. This is attributed to the fact that most work on pyrite has employed polished electrodes that have pre-existing oxidation products on the surface. The existence of a pH dependent stable potential for freshly fractured pyrite electrodes was based on studies conducted mainly on pyrite from Peru.
Date: December 31, 1994
Creator: Yoon, R.H. & Richardson, P.E.
Partner: UNT Libraries Government Documents Department

Control of pyrite surface chemistry in physical coal cleaning

Description: One of the most difficult separations in minerals processing involves the differential flotation of pyrite and coal. Under practical flotation conditions, they are both hydrophobic and no cost-effective method has been developed to efficiently reject the pyrite. The problem arises from inherent floatability of coal and pyrite. Coal is naturally hydrophobic and remains so under practical flotation. Although pyrite is believed to be naturally hydrophilic under practical flotation conditions it undergoes a relatively rapid incipient oxidation reaction that causes self-induced'' flotation. The oxidation product responsible for self-induced'' flotation is believed to be a metal polysulfide, excess sulfur in the lattice, or in some cases elemental sulfur. It is believed that if incipient oxidation of pyrite could be prevented, good pyrite rejection could be obtained. In order to gain a better understanding of how pyrite oxidizes, a new method of preparing fresh, unoxidized pyrite surfaces and a new method of studying pyrite oxidation have been developed this reporting period.
Date: June 24, 1992
Creator: Yoon, R.H. & Richardson, P.R.
Partner: UNT Libraries Government Documents Department

Control of pyrite surface chemistry in physical coal cleaning

Description: Over the past 10 years, much research has provided convincing evidence that one major difficulty in using froth flotation to separate pyrite from coal is the self-induced'' flotation of pyrite. Numerous studies have attempted to identify reactions that occur under moderate oxidizing conditions, which lead to self-induced flotation, and to identify the oxidization products. During the past two report periods, it was established that: (1) freshly fractured pyrite surfaces immediately assume, at fracture, an electrode potential several hundred millivolts more negative than the usual steady state mixed potentials. Within minutes after fracture, the electrodes oxidize and reach higher steady state potentials. It was also shown, by photocurrent measurements, that a negative surface charge (upward band bending) already exists on freshly fractured pyrite, and (2) particle bed electrodes can be used to control the oxidation of pyrite and to precisely determine the electrochemical conditions where flotation occurs, or is depressed. By circulating the solution phase to an ultraviolet spectrometer, soluble products produced on pyrite by oxidation and reduction can be determined, e.g., HS[sup [minus]] was identified as a soluble cathodic reduction product. These and other studies have provided considerable information concerning the anodic oxidation of pyrite. Much less is known about the mechanism and kinetics of oxygen reduction, the other half of the mixed potential reaction. To better understand pyrite oxidation kinetics and determine if oxygen reduction is rate determining, studies have been conducted during this report period on the oxygen reduction reaction with pyrite. In addition, to provide further support that the potential of particle bed electrodes can be controlled, the electro-adsorption and desorption of an organic surfactant was studied.
Date: January 1, 1992
Creator: Yoon, R.H. & Richardson, P.R.
Partner: UNT Libraries Government Documents Department

Studies of incipient oxidation of coal-pyrite for improved pyrite rejection

Description: In order to foster the development of advanced coal cleaning technologies fundamental studies.of the initial stages of pyrite oxidation have been.initiated. This work is being done on pyrite surfaces that are freshly fractured in an electrolyte solution. This procedure produces surfaces that are initially unoxidized, allowing the subsequent oxidation processes to be studied in detail. It is shown that freshly fractured pyrite electrodes instantaneously (at fracture) assume a rest potential several hundred millivolts more negative than the usual open-circuit potential. A finite, anodic photocurrent, is also observed on the fractured electrodes. Following cleavage, the rest potential increases, indicating an oxidation reaction occurring on the electrodes. The photocurrent is relatively insensitive to this oxidation process, and to moderate anodic and cathodic polarization. However, strong cathodic polarization to about -0.76 V (SHE) at pH 9.2 causes the photocurrent to decrease to zero. No reversal in the sign of the photocurrent is observed and it is believed that the flat band potential occurs near -0.76 V, i.e., where the photocurrent goes to zero. Voltammetry indicates that pyrite also undergoes cathodic decomposition at -0.76 V. This establishes that pyrite must be cathodically decomposed to reach the flat band potential.
Date: January 1, 1992
Creator: Yoon, R.H. & Richardson, P.E.
Partner: UNT Libraries Government Documents Department

Development of enhanced sulfur rejection processes

Description: Research at Virginia Tech led to the development of two complementary concepts for improving the removal of inorganic sulfur from many eastern U.S. coals. These concepts are referred to as Electrochemically Enhanced Sulfur Rejection (EESR) and Polymer Enhanced Sulfur Rejection (PESR) processes. The EESR process uses electrochemical techniques to suppress the formation of hydrophobic oxidation products believed to be responsible for the floatability of coal pyrite. The PESR process uses polymeric reagents that react with pyrite and convert floatable middlings, i.e., composite particles composed of pyrite with coal inclusions, into hydrophilic particles. These new pyritic-sulfur rejection processes do not require significant modifications to existing coal preparation facilities, thereby enhancing their adoptability by the coal industry. It is believed that these processes can be used simultaneously to maximize the rejection of both well-liberated pyrite and composite coal-pyrite particles. The project was initiated on October 1, 1992 and all technical work has been completed. This report is based on the research carried out under Tasks 2-7 described in the project proposal. These tasks include Characterization, Electrochemical Studies, In Situ Monitoring of Reagent Adsorption on Pyrite, Bench Scale Testing of the EESR Process, Bench Scale Testing of the PESR Process, and Modeling and Simulation.
Date: March 1, 1996
Creator: Yoon, R.H.; Luttrell, G.H.; Adel, G.T. & Richardson, P.E.
Partner: UNT Libraries Government Documents Department

Controlling incipient oxidation of pyrite for improved rejection. Final report

Description: It is well known that superficial oxidation of pyrite produces a hydrophobic sulfur-rich surface and creates problems in separating the mineral from coal using surface-based processes such as flotation and agglomeration. Numerous studies of pyrite oxidation have been conducted but most of them were concerned with the advanced stages of oxidation, and as a result it was not possible to establish a relationship between oxidation and flotation behavior. A better understanding of the mechanisms and kinetics of the incipient oxidation reactions, which may vary with the origin, morphology, texture, and solid state properties of pyrite, can lead to the development of new processes that can improve pyrite rejection from coal. This project is aimed at better understanding of the mechanisms involved during the initial stages of pyrite oxidation to foster the development of advanced coal cleaning technologies. Studies were conducted by fracturing pyrite electrodes in-situ in an electrochemical cell to create virgin surfaces. Electrochemical and photoelectrochemical techniques were employed to characterize the incipient oxidation of pyrite in aqueous solutions. Microflotation tests were conducted to obtain information on the hydrophobicity of pyrite under controlled E{sub h} and pH conditions, and the results were correlated with electrochemical studies.
Date: April 1, 1996
Creator: Yoon, R.H.; Richardson, P.E. & Tao, D.P.
Partner: UNT Libraries Government Documents Department

Development of enhanced sulfur rejection processes

Description: Research at Virginia Tech led to two complementary concepts for improving the removal of inorganic sulfur from much of the Eastern US coals. One controls the surface properties of coal pyrite (FeS[sub 2]) by electrochemical-.potential control, referred to as the Electrochemically Enhanced Sulfur Rejection (EESR) Process: The second controls the flotation of middlings, i.e., particles composed of pyrite with coal inclusions by using polymeric reagents to react with pyrite and convert the middlings to hydrophilic particles, and is termed the Polymer Enhanced Sulfur Rejection (PESR) Process. These new concepts are based on recent research establishing the two main reasons why flotation fails to remove more than about 50% of the pyritic sulfur from coal: superficial oxidization of liberated pyrite to form polysulfide oxidation products so that a part of the liberated pyrite floats with the coal; and hydrophobic coal inclusions in the middlings dominating their flotation so that the middlings also float with the coal. These new pyritic-sulfur rejection processes do not require significant modifications of existing coal preparation facilities, enhancing their adoptability by the coal industry. It is believed that they can be used simultaneously to achieve both free pyrite and locked pyrite rejection.
Date: March 23, 1993
Creator: Yoon, R.H.; Luttrell, G.; Adel, G. & Richardson, P.E.
Partner: UNT Libraries Government Documents Department

Control of pyrite surface chemistry in physical coal cleaning. Twelfth quarterly technical progress report, June 1, 1992--August 31, 1992

Description: Over the past 10 years, much research has provided convincing evidence that one major difficulty in using froth flotation to separate pyrite from coal is the ``self-induced`` flotation of pyrite. Numerous studies have attempted to identify reactions that occur under moderate oxidizing conditions, which lead to self-induced flotation, and to identify the oxidization products. During the past two report periods, it was established that: (1) freshly fractured pyrite surfaces immediately assume, at fracture, an electrode potential several hundred millivolts more negative than the usual steady state mixed potentials. Within minutes after fracture, the electrodes oxidize and reach higher steady state potentials. It was also shown, by photocurrent measurements, that a negative surface charge (upward band bending) already exists on freshly fractured pyrite, and (2) particle bed electrodes can be used to control the oxidation of pyrite and to precisely determine the electrochemical conditions where flotation occurs, or is depressed. By circulating the solution phase to an ultraviolet spectrometer, soluble products produced on pyrite by oxidation and reduction can be determined, e.g., HS{sup {minus}} was identified as a soluble cathodic reduction product. These and other studies have provided considerable information concerning the anodic oxidation of pyrite. Much less is known about the mechanism and kinetics of oxygen reduction, the other half of the mixed potential reaction. To better understand pyrite oxidation kinetics and determine if oxygen reduction is rate determining, studies have been conducted during this report period on the oxygen reduction reaction with pyrite. In addition, to provide further support that the potential of particle bed electrodes can be controlled, the electro-adsorption and desorption of an organic surfactant was studied.
Date: December 31, 1992
Creator: Yoon, R. H. & Richardson, P. R.
Partner: UNT Libraries Government Documents Department

Genome of Methylobacillus flagellatus, Molecular Basis for Obligate Methylotrophy, and Polyphyletic Origin of Methylotrophy

Description: Along with methane, methanol and methylated amines represent important biogenic atmospheric constituents; thus, not only methanotrophs but also nonmethanotrophic methylotrophs play a significant role in global carbon cycling. The complete genome of a model obligate methanol and methylamine utilizer, Methylobacillus flagellatus (strain KT) was sequenced. The genome is represented by a single circular chromosome of approximately 3 Mbp, potentially encoding a total of 2,766 proteins. Based on genome analysis as well as the results from previous genetic and mutational analyses, methylotrophy is enabled by methanol and methylamine dehydrogenases and their specific electron transport chain components, the tetrahydromethanopterin-linked formaldehyde oxidation pathway and the assimilatory and dissimilatory ribulose monophosphate cycles, and by a formate dehydrogenase. Some of the methylotrophy genes are present in more than one (identical or nonidentical) copy. The obligate dependence on single-carbon compounds appears to be due to the incomplete tricarboxylic acid cycle, as no genes potentially encoding alpha-ketoglutarate, malate, or succinate dehydrogenases are identifiable. The genome of M. flagellatus was compared in terms of methylotrophy functions to the previously sequenced genomes of three methylotrophs, Methylobacterium extorquens (an alphaproteobacterium, 7 Mbp), Methylibium petroleiphilum (a betaproteobacterium, 4 Mbp), and Methylococcus capsulatus (a gammaproteobacterium, 3.3 Mbp). Strikingly, metabolically and/or phylogenetically, the methylotrophy functions in M. flagellatus were more similar to those in M. capsulatus and M. extorquens than to the ones in the more closely related M. petroleiphilum species, providing the first genomic evidence for the polyphyletic origin of methylotrophy in Betaproteobacteria.
Date: July 24, 2007
Creator: Chistoserdova, L; Lapidus, A; Han, C; Godwin, L; Saunders, L; Brettin, T et al.
Partner: UNT Libraries Government Documents Department

A Les Houches Interface for BSM Generators

Description: We propose to combine and slightly extend two existing 'Les Houches Accords' to provide a simple generic interface between beyond-the-standard-model parton-level and event-level generators. All relevant information--particle content, quantum numbers of new states, masses, cross sections, parton-level events, etc.--is collected in one single file, which adheres to the Les Houches Event File (LHEF) standard.
Date: December 1, 2007
Creator: Alwall, J.; Boos, E.; Dudko, L.; Gigg, M.; Herquet, M.; Pukhov, A. et al.
Partner: UNT Libraries Government Documents Department

A Les Houches Interface for BSM Generators

Description: We propose to combine and slightly extend two existing 'Les Houches Accords' to provide a simple generic interface between beyond-the-standard-model parton-level and event-level generators. All relevant information--particle content, quantum numbers of new states, masses, cross sections, parton-level events, etc.--is collected in one single file, which adheres to the Les Houches Event File (LHEF) standard.
Date: January 23, 2008
Creator: Alwall, J.; Boos, E.; Dudko, L.; Gigg, M.; Herquet, M.; Pukhov, A. et al.
Partner: UNT Libraries Government Documents Department

Development of enhanced sulfur rejection processes. Final technical progress report, third quarter (8. quarterly report), July 1--September 30, 1994

Description: Pyrite becomes hydrophobic upon superficial oxidation and floats without a collector. The flotation begins to occur at potentials above the stable potentials identified by the chronoamperometry experiments conducted with freshly fractured pyrite. This finding suggests that iron polysulfide, formed during the initial stages of oxidation, is responsible for the flotation. The collectorless flotation is suppressed above the potential where the mineral is aggressively oxidized, forming iron hydroxide and soluble sulfoxy species. The collectorless flotation is less significant at pH 9.2 than at pH 4.6, possibly due to the formation of iron hydroxide. At pH 9.2, the collectorless flotation increases in the presence of EDTA and hydrocarbon oil. The collectorless flotation of pyrite can be suppressed by galvanically coupling the mineral with reactive metals such as aluminum, manganese, and zinc. This effectively prevents the mineral from oxidation. The microflotation tests conducted with mono-sized pyrite samples show that the collectorless flotation can be suppressed effectively in the presence of metal powders. Bench-scale flotation experiments conducted using Denver laboratory flotation cell and a 2-inch diameter Microcel flotation column, also demonstrates that the collectorless flotation can be suppressed in the presence of the reactive metals. It has been established that the most important parameters determining the effectiveness of suppressing pyrite flotation by the galvanic coupling technique are the surface area of the galvanic contractors and the solids concentration of the slurry during conditioning.
Date: March 20, 1996
Creator: Yoon, R.H.; Luttrell, G.H.; Tao, D.P.; Lu, M.X. & Richardson, P.E.
Partner: UNT Libraries Government Documents Department

Unusual Gene Order and Organization of the Sea Urchin Hox Cluster

Description: The highly consistent gene order and axial colinear expression patterns found in vertebrate hox gene clusters are less well conserved across the rest of bilaterians. We report the first deuterostome instance of an intact hox cluster with a unique gene order where the paralog groups are not expressed in a sequential manner. The finished sequence from BAC clones from the genome of the sea urchin, Strongylocentrotus purpuratus, reveals a gene order wherein the anterior genes (Hox1, Hox2 and Hox3) lie nearest the posterior genes in the cluster such that the most 3 gene is Hox5. (The gene order is : 5-Hox1, 2, 3, 11/13c, 11/13b, 11/13a, 9/10, 8, 7, 6, 5 - 3). The finished sequence result is corroborated by restriction mapping evidence and BAC-end scaffold analyses. Comparisons with a putative ancestral deuterostome Hox gene cluster suggest that the rearrangements leading to the sea urchin gene order were many and complex.
Date: October 11, 2005
Creator: Cameron, R A; Rowen, L; Nesbitt, R; Bloom, S; Rast, J P; Berney, K et al.
Partner: UNT Libraries Government Documents Department

The Calyptogena magnifica chemoautotrophic symbiont genome

Description: Chemoautotrophic endosymbionts are the metabolic cornerstone of hydrothermal vent communities, providing invertebrate hosts with nearly all of their nutrition. The Calyptogena magnifica (Bivalvia: Vesicomyidae) symbiont, Candidatus Ruthia magnifica, is the first intracellular sulfur-oxidizing endosymbiont to have its genome sequenced, revealing a suite of metabolic capabilities. The genome encodes major chemoautotrophic pathways as well as pathways for biosynthesis of vitamins, cofactors, and all 20 amino acids required by the clam.
Date: March 1, 2007
Creator: Newton, I.L.; Woyke, T.; Auchtung, T.A.; Dilly, G.F.; Dutton,R.J.; Fisher, M.C. et al.
Partner: UNT Libraries Government Documents Department

A Repository for Beyond-the-Standard-Model Tools

Description: To aid phenomenological studies of Beyond-the-Standard-Model (BSM) physics scenarios, a web repository for BSM calculational tools has been created. We here present brief overviews of the relevant codes, ordered by topic as well as by alphabet.
Date: May 1, 2005
Creator: Skands, P.; /Fermilab; Richardson, P.; Allanach, B.C.; Baer, H.; Belanger, G. et al.
Partner: UNT Libraries Government Documents Department

Comparison of the complete genome sequences of Pseudomonas syringae pv. syringae B728a and pv. tomato DC3000

Description: The complete genomic sequence of Pseudomonas syringae pathovar syringae B728a (Pss B728a), has been determined and is compared with that of Pseudomonas syringae pv. tomato DC3000 (Pst DC3000). The two pathovars of this economically important species of plant pathogenic bacteria differ in host range and other interactions with plants, with Pss having a more pronounced epiphytic stage of growth and higher abiotic stress tolerance and Pst DC3000 having a more pronounced apoplastic growth habitat. The Pss B728a genome (6.1 megabases) contains a circular chromosome and no plasmid, whereas the Pst DC3000 genome is 6.5 mbp in size, composed of a circular chromosome and two plasmids. While a high degree of similarity exists between the two sequenced Pseudomonads, 976 protein-encoding genes are unique to Pss B728a when compared to Pst DC3000, including large genomic islands likely to contribute to virulence and host specificity. Over 375 repetitive extragenic palindromic sequences (REPs) unique to Pss B728a when compared to Pst DC3000 are widely distributed throughout the chromosome except in 14 genomic islands, which generally had lower GC content than the genome as a whole. Content of the genomic islands vary, with one containing a prophage and another the plasmid pKLC102 of P. aeruginosa PAO1. Among the 976 genes of Pss B728a with no counterpart in Pst DC3000 are those encoding for syringopeptin (SP), syringomycin (SR), indole acetic acid biosynthesis, arginine degradation, and production of ice nuclei. The genomic comparison suggests that several unique genes for Pss B728a such as ectoine synthase, DNA repair, and antibiotic production may contribute to epiphytic fitness and stress tolerance of this organism.
Date: July 14, 2005
Creator: Feil, H; Feil, W S; Chain, P; Larimer, F; DiBartolo, G; Copeland, A et al.
Partner: UNT Libraries Government Documents Department

Comparison of multiple ecogenomics methods for determining ecosystem function in uranium-contaminated environments

Description: Background: Bioremediation may offer the only feasiblestrategy for the nearly intractable problem of metal and radionuclidecontamination of soil and groundwater. To understand bioremediation incontaminated environments, it is critical to determine the organismspresent in these environments, analyze their responses to stressconditions, and elucidate functional position in the environment.Methods: We used multiple molecular techniques on both sediment andgroundwater to develop a better understanding of the functionalcapability and stress level within the microbial community inrelationship to over one hundred geochemical parameters. Due to the lowpH (3.5-4.5) and high contaminant levels (e.g., uranium) microbialdensities and activities were low. We used a phage polymeraseamplification system to construct large and small insert DNA libraries,performed metagenome sequencing, constructed clonal libraries of selectfunctional genes (SSU rRNA gene, nirK, nirS, amoA, pmoA, and dsrAB), useda SSU rDNA Phylochip microarray (9,000 taxa), and a functional gene array(23K genes). A complete comparison for community differences andsimilarities between the different techniques was assessed using severalbioinformatics techniques. Results: SSU rDNA analysis revealed thepresence of distinct bacterial phyla, including proteobacteria,acidobacteria, and planctomycetes along the contaminant gradient.Metagenome analysis identified many of the same organisms, and diversitywas lower in water than sediment. Analysis with functional gene arrays,phylochip, and specific probes for genes and organisms involved inbiogeochemical cycling of C, N, and S, metal resistance, stress response,and contaminant degradation suggested that the dominant species could bebiostimulated during in situ uranium reduction. Several other findings ofdifference and similarities between methods are presented. Conclusion:These systems biology field studies could be enabling for strategies toattenuate nletal and radionuclide contamination.
Date: January 10, 2007
Creator: Hazen, T.C.; Dehal, P.; Arkin, A.P.; Fields, M.W.; Keller, M.; Zhou, J. et al.
Partner: UNT Libraries Government Documents Department

Large microchannel array fabrication and results for DNA sequencing

Description: We have developed a process for the production of microchannel arrays on bonded glass substrates up to I4 x 58 cm, for DNA sequencing. Arrays of 96 and 384 microchannels, each 46 cm long have been built. This technology offers significant advantages over discrete capillaries or conventional slab-gel approaches. High throughput DNA sequencing with over 550 base pairs resolution has been achieved. With custom fabrication apparatus, microchannels are etched in a borosilicate substrate, and then fusion bonded to a top substrate 1.1 mm thick that has access holes formed in it. SEM examination shows a typical microchannel to be 40 x 180 micrometers by 46 cm Iong; the etch is approximately isotropic, leaving a key undercut, for forming a rounded channel. The surface roughness at the bottom of the 40 micrometer deep channel has been profilometer measured to be as low as 20 nm; the roughness at the top surface was 2 nm. Etch uniformity of about 5% has been obtained using a 22% vol. HF / 78% Acetic acid solution. The simple lithography, etching, and bonding of these substrates enables efficient production of these arrays and extremely precise replication From master masks and precision machining with a mandrel. Keywords: microchannels, microchannel plates, DNA sequencing, electrophoresis, borosilicate glass
Date: January 7, 1999
Creator: Pastrone, R L; Balch, J W; Brewer, L R; Copeland, A C; Davidson , J C; Fitch, J P et al.
Partner: UNT Libraries Government Documents Department

Searching for R-parity violation at run-II of the tevatron.

Description: The authors present an outlook for possible discovery of supersymmetry with broken R-parity at Run II of the Tevatron. They first present a review of the literature and an update of the experimental bounds. In turn they then discuss the following processes: (1) resonant slepton production followed by R{sub P} decay, (a) via LQD{sup c} and (b) via LLE{sup c}; (2) how to distinguish resonant slepton production from Z{prime} or W{prime} production; (3) resonant slepton production followed by the decay to neutralino LSP, which decays via LQD{sup c}; (4) resonant stop production followed by the decay to a chargino, which cascades to the neutralino LSP; (5) gluino pair production followed by the cascade decay to charm squarks which decay directly via L{sub 1}Q{sub 2}D{sub 1}{sup c}; (6) squark pair production followed by the cascade decay to the neutralino LSP which decays via L{sub 1}Q{sub 2}D{sub 1}{sup c}; (7) MSSM pair production followed by the cascade decay to the LSP which decays (a) via LLE{sup c}, (b) via LQD{sup c}, and (c) via U{sup c}D{sup c}D{sup c}, respectively; and (8) top quark and top squark decays in spontaneous R{sub P}.
Date: June 22, 1999
Creator: Allanach, B.; Banerjee, S.; Berger, E. L.; Chertok, M.; Diaz, M. A.; Dreiner, H. et al.
Partner: UNT Libraries Government Documents Department