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Sample records for acid-deficient uranyl nitrate

  1. EXTRACTION OF URANYL NITRATE FROM AQUEOUS SOLUTIONS

    DOEpatents

    Furman, N.H.; Mundy, R.J.

    1957-12-10

    An improvement in the process is described for extracting aqueous uranyl nitrate solutions with an organic solvent such as ether. It has been found that the organic phase will extract a larger quantity of uranyl nitrate if the aqueous phase contains in addition to the uranyl nitrate, a quantity of some other soluble nitrate to act as a salting out agent. Mentioned as suitable are the nitrates of lithium, calcium, zinc, bivalent copper, and trivalent iron.

  2. Photochemical reduction of uranyl nitrate

    SciTech Connect

    Duerksen, W.K.

    1993-10-20

    The photochemical reduction of uranyl nitrate solutions to tetravalent uranium was investigated as a means of producing uranium dioxide feed for the saltless direct oxide reduction (SDOR) process. At high uranium concentrations, reoxidation of U{sup +4} occurs rapidly. The kinetics of the nitric oxidation of tetravalent uranium depend on the concentrations of hydrogen ion, nitrate ion, nitrous acid, and tetravalent uranium in the same manner as was reported elsewhere for the nitrate oxidation of PU{sup +3}. Reaction rate data were successfully correlated with a mechanism in which nitrogen dioxide is the reactive intermediate. Addition of a nitrous acid scavenger suppresses the reoxidation reaction. An immersion reactor employing a mercury vapor lamp gave reduction times fast enough for routine production usage. Precipitation techniques for conversion of aqueous U(NO{sub 3}){sub 4} to hydrous UO{sub 2} were evaluated. Prolonged dewatering times tended to make the process time consuming. Use of 3- to 4-M aqueous NaOH gave the best dewatering times observed. Reoxidation of the UO{sub 2} by water of hydration was encountered, which required the drying process to be carried out under a reducing atmosphere.

  3. GRAPHITE PRODUCTION UTILIZING URANYL NITRATE HEXAHYDRATE CATALYST

    DOEpatents

    Sheinberg, H.; Armstrong, J.R.; Schell, D.H.

    1964-03-10

    ABS>The graphitizing of a mixture composed of furfuryl alcohol binder and uranyl nitrate hexahydrate hardener and the subsequent curing, baking, and graphitizing with pressure being initially applied prior to curing are described. The pressure step may be carried out by extrusion, methyl cellulose being added to the mixture before the completion of extrusion. Uranium oxide may be added to the graphitizable mixture prior to the heating and pressure steps. The graphitizable mixture may consist of discrete layers of different compositions. (AEC)

  4. SEPARATION OF URANYL NITRATE BY EXTRACTION

    DOEpatents

    Stoughton, R.W.; Steahly, F.L.

    1958-08-26

    A process is presented for obtaining U/sup 233/ from solutions containing Pa/sup 233/. A carrier precipitate, such as MnO/sub 2/, is formed in such solutions and carries with it the Pa/sup 233/ present. This precipitate is then dissolved in nitric acid and the solution is aged to allow decay of the Pa/ sup 233/ into U/sup 233/. After a sufficient length of time the U/sup 233/ bearing solution is made 2.5 to 4.5 Molar in manganese nitrate by addition thereof, and the solution is then treated with ether to obtain uranyl nitrate by solvent extraction techniques.

  5. The effect of uranyl nitrate on intestinal transfer of hexoses

    PubMed Central

    Newey, H.; Sanford, P. A.; Smyth, D. H.

    1966-01-01

    1. Uranyl nitrate in a concentration of 3 × 10-4 M caused reduction in mucosal transfer of glucose but not of galactose nor 3-O-methyl-glucose by sacs of rat everted intestine. At this concentration uranyl nitrate had little effect on glucose metabolism (measured by glucose disappearance). 2. Uranyl nitrate in a concentration of 3 × 10-3 M caused reduction in transfer of glucose, galactose, 3-O-methyl-glucose and fluid, and inhibited glucose metabolism. 3. Uranyl nitrate did not inhibit entry of glucose into the intestine under anaerobic conditions. 4. Glucose was found to inhibit or stimulate galactose transfer depending on the conditions. The inhibitory action is presumably by competition for a common carrier, whereas stimulation indicates that glucose metabolism can supply energy for galactose transfer. 5. It is suggested that there are two different routes for glucose in the cell, one of which is uranyl sensitive and not used by galactose, and the other is uranyl insensitive and shared by both hexoses. The implications of this are discussed in relation to transport and metabolism. PMID:5972151

  6. Optimization of a uranyl nitrate passive neutron counter

    SciTech Connect

    Rauch, Eric Benton; Bracken, David; West, James; Freeman, Corey; Newell, Matthew R; Bourret, Steven C; Rothrock, Richard B; Ladd - Lively, Jennifer L; Schuh, Denise

    2010-01-01

    Safeguarding natural uranium as it enters the fuel cycle has become a priority for the safeguards community in recent years. Uranyl nitrate is a material of interest in this endeavor because it is normally a step in the process from converting uranium ores to more concentrated forms like UO{sub 2} and U{sub 3}O{sub 8}. This paper will detail the improvements and design optimizations made for a uranyl nitrate neutron detector. The original design of the detector was based on standard neutron counter designs and featured 2 rings of He-3 tubes fully moderated and shielded from background. Several areas for enhancement were identified after months of testing in three different locations. An operating uranyl nitrate facility was included as one of the test locations. Three significant upgrades to the counter addressed in the redesign were: real time background detection, counter reliability improvements, and optimization of the detector design for the detection of neutrons emitted by the uranyl nitrate flowing through the monitored process pipe. The optimized detector design includes significant electronics upgrades, the ability to detect neutrons (background and signal) with 36 degree spatial resolution around the process pipe for signal and 45 degree spatial resolution for background, inner and outer rings of He-3 tubes for real time background corrections, and notably more reliable cabling. Monte Carlo N-Particle (MCNP) modeling was used to optimize the signal (neutrons from uranyl nitrate in the monitored process pipe) to noise (background neutrons from all sources) ratio of the inner ring of He-3 tubes. Additionally, MCNP modeling maximized noise to signal on the outer ring of He-3 tubes. Details of the detector optimization as well as all the additional detector enhancements will be discussed. The neutron counter will be field tested on the Uranyl Nitrate Calibration Loop Equipment (UNCLE) facility at Oak Ridge National Laboratory (ORNL).

  7. SEPARATION OF BARIUM VALUES FROM URANYL NITRATE SOLUTIONS

    DOEpatents

    Tompkins, E.R.

    1959-02-24

    The separation of radioactive barium values from a uranyl nitrate solution of neutron-irradiated uranium is described. The 10 to 20% uranyl nitrate solution is passed through a flrst column of a cation exchange resin under conditions favoring the adsorption of barium and certain other cations. The loaded resin is first washed with dilute sulfuric acid to remove a portion of the other cations, and then wash with a citric acid solution at pH of 5 to 7 to recover the barium along with a lesser amount of the other cations. The PH of the resulting eluate is adjusted to about 2.3 to 3.5 and diluted prior to passing through a smaller second column of exchange resin. The loaded resin is first washed with a citric acid solution at a pH of 3 to elute undesired cations and then with citric acid solution at a pH of 6 to eluts the barium, which is substantially free of undesired cations.

  8. Influence of Acidity on Uranyl Nitrate Association in Aqueous Solutions: A Molecular Dynamics Simulation Study

    SciTech Connect

    de Almeida, Valmor F; Cui, Shengting; Khomami, Bamin; Ye, Xianggui; Smith, Rodney Bryan

    2010-01-01

    Uranyl ion complexation with water and nitrate is a key aspect of the uranium/plutonium extraction process. We have carried out a molecular dynamics simulation study to investigate this complexation process, including the molecular composition of the various complex species, the corresponding structure, and the equilibrium distribution of the complexes. The observed structures of the complexes suggest that in aqueous solution, uranyls are generally hydrated by 5 water molecules in the equatorial plane. When associating with nitrate ions, a water molecule is replaced by a nitrate ion, preserving the five-fold coordination and planar symmetry. Analysis of the pair correlation function between uranyl and nitrate suggests that nitrates bind to uranyl in aqueous solution mainly in a monodentate mode, although a small portion of bidentates occur. Dynamic association and dissociation between uranyls and nitrates take place in aqueous solution with a substantial amount of fluctuation in the number of various uranyl nitrate species. The average number of the uranyl mononitrate complexes shows a dependence on acid concentration consistent with equilibrium-constant analysis, namely, the concentration of [UO2NO3]+ increases with nitric acid concentration.

  9. Analysis of Enriched Uranyl Nitrate in Nested Annular Tank Array

    SciTech Connect

    John D. Bess; James D. Cleaver

    2009-06-01

    Two series of experiments were performed at the Rocky Flats Critical Mass Laboratory during the 1980s using highly enriched (93%) uranyl nitrate solution in annular tanks. [1, 2] Tanks were of typical sizes found in nuclear production plants. Experiments looked at tanks of varying radii in a co-located set of nested tanks, a 1 by 2 array, and a 1 by 3 array. The co-located set of tanks had been analyzed previously [3] as a benchmark for inclusion within the International Handbook of Evaluated Criticality Safety Benchmark Experiments. [4] The current study represents the benchmark analysis of the 1 by 3 array of a series of nested annular tanks. Of the seventeen configurations performed in this set of experiments, twelve were evaluated and nine were judged as acceptable benchmarks.

  10. Extraction of nitric acid, uranyl nitrate, and bismuth nitrate from aqueous nitric acid solutions with CMPO

    SciTech Connect

    Spencer, B.B.

    1995-08-01

    DOE sponsored development of the transuranium extraction (TRUEX) process for removing actinides from radioactive wastes. The solvent is a mixture of CMPO and TBP. Since the extraction characteristics of CMPO are not as well understood as those of TBP, the extraction of nitric acid, uranyl nitrate, and bismuth nitrate with CMPO (dissolved in n-dodecane) were studied. Results indicate that CMPO extracts nitric acid with a 1:1 stoichiometry; equilibrium constant is 2. 660{plus_minus}0.092 at 25 C, and extraction enthalpy is -5. 46{plus_minus}0.46 kcal/mol. Slope analysis indicates that uranyl nitrate extracts with a mixed equilibria of 1:1 and 2:1 stoichiometries in nearly equal proportion. Equil. constant of the 2: 1 extraction was 1.213 {times} 10{sup 6}{plus_minus}3.56 {times} 10{sup 4} at 25 C; reaction enthalpy was -9.610{plus_minus}0.594 kcal/mol. Nitration complexation constant is 8.412{plus_minus}0.579, with an enthalpy of -10.72{plus_minus}1.87 kcal/mol. Bismuth nitrate also extracts with a mixed equilibria of (perhaps) 1:1 and 2:1 stoichiometries. A 2:1 extraction equilibrium and a nitrate complexation adequately model the data. Kinetics and enthalpies were also measured.

  11. Status Update: Uranyl Nitrate Calibration Loop Equipment (UNCLE) at ORNL

    SciTech Connect

    Ladd-Lively, Jennifer L

    2009-01-01

    The successful completion of a field trial of safeguards monitoring equipment at a natural uranium conversion plant (NUCP) demonstrated the need for a facility in which to perform full-scale equipment testing under controlled conditions prior to field deployment of safeguards systems at additional plants. Oak Ridge National Laboratory has developed a Uranyl Nitrate Calibration Loop Equipment (UNCLE) facility to simulate the full-scale operating conditions for a purified uranium-bearing aqueous stream exiting the solvent extraction process conducted in an NUCP. In addition to calibrating instruments such as the neutron detector developed at Los Alamos National Laboratory, UNCLE will be used to test other in-line instruments (mass and volumetric flowmeters, spectrophotometers, etc.). UNCLE will be able to test commercially available equipment, such as the Endress+Hauser Promass 83F Coriolis meter that was used in the field test and other equipment that is presently under development. UNCLE is designed to accommodate different pipe sizes, flow rates, solution concentrations, and other variables of interest. Construction is expected to be completed by the end of September 2008 with initial testing beginning later that year. The design and current status of UNCLE will be presented, along with the capabilities of the facility and the proposed test plans.

  12. Renal Toxicogenomic Response to Chronic Uranyl Nitrate Insult in Mice

    PubMed Central

    Taulan, Magali; Paquet, François; Maubert, Christophe; Delissen, Olivia; Demaille, Jacques; Romey, Marie-Catherine

    2004-01-01

    Although the nephrotoxicity of uranium has been established through numerous animal studies, relatively little is known about the effects of long-term environmental uranium exposure. Using a combination of conventional biochemical studies and serial analysis of gene expression (SAGE), we examined the renal responses to uranyl nitrate (UN) chronic exposure. Renal uranium levels were significantly increased 4 months after ingestion of uranium in drinking water. Creatinine levels in serum were slightly but significantly increased compared with those in controls. Although no further significant differences in other parameters were noted, substantial molecular changes were observed in toxicogenomic profiles. UN induced dramatic alterations in expression levels of more than 200 genes, mainly up-regulated, including oxidative-response–related genes, genes encoding for cellular metabolism, ribosomal proteins, signal transduction, and solute transporters. Seven differentially expressed transcripts were confirmed by real-time quantitative polymerase chain reaction. In addition, significantly increased peroxide levels support the implication of oxidative stress in UN toxicant response. This report highlights the potential of SAGE for the discovery of novel toxicant-induced gene expression alterations. Here, we present, for the first time, a comprehensive view of renal molecular events after uranium long-term exposure. PMID:15598614

  13. PROCESS FOR EXTRACTING NEPTUNIUM AND PLUTONIUM FROM NITRIC ACID SOLUTIONS OF SAME CONTAINING URANYL NITRATE WITH A TERTIARY AMINE

    DOEpatents

    Sheppard, J.C.

    1962-07-31

    A process of selectively extracting plutonium nitrate and neptunium nitrate with an organic solution of a tertiary amine, away from uranyl nitrate present in an aqueous solution in a maximum concentration of 1M is described. The nitric acid concentration is adjusted to about 4M and nitrous acid is added prior to extraction. (AEC)

  14. CONTINUOUS PRECIPITATION METHOD FOR CONVERSION OF URANYL NITRATE TO URANIUM HEXAFLUORIDE

    DOEpatents

    Reinhart, G.M.; Collopy, T.J.

    1962-11-13

    A continuous precipitation process is given for converting a uranyl nitrate solution to uranium tetrafluoride. A stream of the uranyl nitrate solution and a stream of an aqueous ammonium hydroxide solution are continuously introduced into an agitated reaction zone maintained at a pH of 5.0 to 6.5. Flow rates are adjusted to provide a mean residence time of the resulting slurry in the reaction zone of at least 30 minutes. After a startup period of two hours the precipitate is recovered from the effluent stream by filtration and is converted to uranium tetrafluoride by reduction to uranium dioxide with hydrogen and reaction of the uranium dioxide with anhydrous hydrogen fluoride. (AEC)

  15. Luminescence spectra of the uranyl ion in two geometrically similar coordination environments. Uranyl nitrate hexahydrate and di-.mu.-aquo-bis[dioxobis(nitrato)uranium(VI)] diimidazole

    SciTech Connect

    Brittain, Harry G.; Perry, Dale L.

    1980-10-01

    The luminescence spectra of the uranyl ion have been obtained at room and liquid nitrogen temperatures in the crystal hosts of uranyl nitrate hexahydrate (UNH) and di~~-aquo-bis(dioxodinitratouranium(VI)) di-imidazole (UNI). In both coordination spheres, the uranyl ion lies at the center of similar, distorted coordination hexagons consisting of two bidentate nitrate groups and two water molecules; the only difference in the coordination geometries is that the water molecules are terminal in the UNH complex and bridging in the UNI complex. The uranium-uranium "bond" distance in the UNI complex is 3.93 A. At room temperature, the emission spectra of the two compounds are essentially identical, but significant differences appear upon cooling to 77°K. Vibronic structure is observed in the crystal of the UNI complex b4t not in the crystal of uranyl nitrate hexahydrate; this implies that the geom~try of the uranyl ion in the two excited states is somewhat different. An energy level sequence is presented in which the various emission lines arise from a slightly split excited state (splitting approximately 80-85 cm-1) to several vibrational levels of the ground electronic manifold. The energy spacing of the ground vibrational levels (approximately 860 cm-1) was found to vary when changing crystal systems.

  16. Dehydration of Uranyl Nitrate Hexahydrate to Uranyl Nitrate Trihydrate under Ambient Conditions as Observed via Dynamic Infrared Reflectance Spectroscopy

    SciTech Connect

    Johnson, Timothy J.; Sweet, Lucas E.; Meier, David E.; Mausolf, Edward J.; Kim, Eunja; Weck, Philippe F.; Buck, Edgar C.; McNamara, Bruce K.

    2015-05-22

    the hexahydrate [UO2(NO3)2(H2O)6] (UNH) and the trihydrate [UO2(NO3)2(H2O)3] (UNT) forms. Their stabilities depend on both relative humidity and temperature. Both phases have previously been studied by infrared transmission spectroscopy, but the data were limited by both instrumental resolution and the ability to prepare the samples as pellets without desiccating them. We report time-resolved infrared (IR) measurements using an integrating sphere that allow us to observe the transformation from the hexahydrate to the trihydrate simply by flowing dry nitrogen gas over the sample. Hexahydrate samples were prepared and confirmed via known XRD patterns, then measured in reflectance mode. The hexahydrate has a distinct uranyl asymmetric stretch band at 949.0 cm-1 that shifts to shorter wavelengths and broadens as the sample dehydrates and recrystallizes to the trihydrate, first as a blue edge shoulder but ultimately resulting in a doublet band with reflectance peaks at 966 and 957 cm-1. The data are consistent with transformation from UNH to UNT since UNT has two non-equivalent UO22+ sites. The dehydration of UO2(NO3)2(H2O)6 to UO2(NO3)2(H2O)3 is both a morphological and structural change that has the lustrous lime green crystals changing to the dull greenish yellow of the trihydrate. Crystal structures and phase transformation were confirmed theoretically using DFT calculations and experimentally via microscopy methods. Both methods showed a transformation with two distinct sites for the uranyl cation in the trihydrate, as opposed to a single crystallographic site in the hexahydrate.

  17. Water-Reflected 233U Uranyl Nitrate Solutions in Simple Geometry

    SciTech Connect

    Elam, K.R.

    2001-08-15

    A number of critical experiments involving {sup 233}U were performed in the Oak Ridge National Laboratory Building 9213 Critical Experiments Facility during the years 1952 and 1953. These experiments, reported in Reference 1, were directed toward determining bounding values for the minimum critical mass, minimum critical volume, and maximum safe pipe size of water-moderated solutions of {sup 233}U. Additional information on the critical experiments was found in the experimental logbooks. Two experiments utilizing uranyl nitrate (UO{sub 2}(NO{sub 3}){sub 2}) solutions in simple geometry are evaluated in this report. Experiment 37 is in a 10.4-inch diameter sphere, and Experiment 39 is in a 10-inch diameter cylinder. The {sup 233}U concentration ranges from 49 to 62 g {sup 233}U/l. Both experiments were reflected by at least 6 inches of water in all directions. Paraffin-reflected uranyl nitrate experiments, also reported in Reference 1, are evaluated elsewhere. Experiments with smaller paraffin reflected 5-, 6-, and 7.5-inch diameter cylinders are evaluated in U233-SOL-THERM-004. Experiments with paraffin reflected 8-, 8.5-, 9-, 10-, and 12-inch diameter cylinders are evaluated in U233-SOL-THERM-002. Later experiments with highly-enriched {sup 235}U uranyl fluoride solution in the same 10.4-inch diameter sphere are reported in HEU-SOL-THERM-010. Both experiments were judged acceptable for use as criticality-safety benchmark experiments.

  18. Studies on the reverse osmosis treatment of uranyl nitrate solution

    SciTech Connect

    Prabhakar, S.; Panicker, S.T.; Misra, B.M.; Ramani, P.S. )

    1992-03-01

    The aqueous effluent generated in uranium processing, particularly in the nuclear fuel fabrication step, contains mainly uranium nitrate. This requires treatment before discharge into the environment to meet stringent standards. This paper presents the performance of cellulose acetate membranes with regard to rejection of uranium under reverse osmotic conditions for feed concentrations up to 200 mg/l of uranium, which corresponds to the levels normally prevalent in the effluents. The use of additives like the disodium salt of ethylenediaminetetraacetic acid and sodium sulfate for the improvement of reverse osmosis performance of the above membranes was also investigated. In the light of the experimental results, the suitability of reverse osmosis for the decontamination of uranium effluents is discussed.

  19. Uranyl nitrate inhibits lactate gluconeogenesis in isolated human and mouse renal proximal tubules: A {sup 13}C-NMR study

    SciTech Connect

    Renault, Sophie; Faiz, Hassan; Gadet, Rudy; Ferrier, Bernard; Martin, Guy; Baverel, Gabriel; Conjard-Duplany, Agnes

    2010-01-01

    As part of a study on uranium nephrotoxicity, we investigated the effect of uranyl nitrate in isolated human and mouse kidney cortex tubules metabolizing the physiological substrate lactate. In the millimolar range, uranyl nitrate reduced lactate removal and gluconeogenesis and the cellular ATP level in a dose-dependent fashion. After incubation in phosphate-free Krebs-Henseleit medium with 5 mM L-[1-{sup 13}C]-, or L-[2-{sup 13}C]-, or L-[3-{sup 13}C]lactate, substrate utilization and product formation were measured by enzymatic and NMR spectroscopic methods. In the presence of 3 mM uranyl nitrate, glucose production and the intracellular ATP content were significantly reduced in both human and mouse tubules. Combination of enzymatic and NMR measurements with a mathematical model of lactate metabolism revealed an inhibition of fluxes through lactate dehydrogenase and the gluconeogenic enzymes in the presence of 3 mM uranyl nitrate; in human and mouse tubules, fluxes were lowered by 20% and 14% (lactate dehydrogenase), 27% and 32% (pyruvate carboxylase), 35% and 36% (phosphoenolpyruvate carboxykinase), and 39% and 45% (glucose-6-phosphatase), respectively. These results indicate that natural uranium is an inhibitor of renal lactate gluconeogenesis in both humans and mice.

  20. Uranyl nitrate-exposed rat alveolar macrophages cell death: Influence of superoxide anion and TNF α mediators

    SciTech Connect

    Orona, N.S.; Tasat, D.R.

    2012-06-15

    Uranium compounds are widely used in the nuclear fuel cycle, military and many other diverse industrial processes. Health risks associated with uranium exposure include nephrotoxicity, cancer, respiratory, and immune disorders. Macrophages present in body tissues are the main cell type involved in the internalization of uranium particles. To better understand the pathological effects associated with depleted uranium (DU) inhalation, we examined the metabolic activity, phagocytosis, genotoxicity and inflammation on DU-exposed rat alveolar macrophages (12.5–200 μM). Stability and dissolution of DU could differ depending on the dissolvent and in turn alter its biological action. We dissolved DU in sodium bicarbonate (NaHCO{sub 3} 100 mM) and in what we consider a more physiological vehicle resembling human internal media: sodium chloride (NaCl 0.9%). We demonstrate that uranyl nitrate in NaCl solubilizes, enters the cell, and elicits its cytotoxic effect similarly to when it is diluted in NaHCO{sub 3}. We show that irrespective of the dissolvent employed, uranyl nitrate impairs cell metabolism, and at low doses induces both phagocytosis and generation of superoxide anion (O{sub 2}{sup −}). At high doses it provokes the secretion of TNFα and through all the range of doses tested, apoptosis. We herein suggest that at DU low doses O{sub 2}{sup −} may act as the principal mediator of DNA damage while at higher doses the signaling pathway mediated by O{sub 2}{sup −} may be blocked, prevailing damage to DNA by the TNFα route. The study of macrophage functions after uranyl nitrate treatment could provide insights into the pathophysiology of uranium‐related diseases. -- Highlights: ► Uranyl nitrate effect on cultured macrophages is linked to the doses and independent of its solubility. ► At low doses uranyl nitrate induces generation of superoxide anion. ► At high doses uranyl nitrate provokes secretion of TNFα. ► Uranyl nitrate induces apoptosis through

  1. Processing of uranyl nitrate hexahydrate (UNH) at DOE`s Fernald Site: Success and pitfalls

    SciTech Connect

    Luken, D.W.; Brettschneider, D.J.; Heck, R.P. III; White, C.A.

    1996-02-01

    After 36 years of operation, uranium production at the Department of Energy Fernald Environmental Management Project (FEMP) was halted in 1989. Uranyl Nitrate Hexahydrate (UNH) had been produced during the uranium refining. In June 1991, DOE determined the UNH to be a mixed hazardous waste under the Resource Conservation and Recovery Act. A UNH Neutralization Project began processing UNH stored in stainless steel tanks located in various areas within the Fernald Plant 2/3 Complex. It was discovered that the valves, flanges, and other fittings of the UNH storage tanks were leaking. This made processing the UNH a high priority and Comprehensive, Environmental, Response, Compensation, and Liability Act Removal Action No. 20, Stabilization of UNH Inventories, was initiated. This report presents the successes and pitfalls of the cleanup of UNH.

  2. Uranyl nitrate pouring solution for producing nuclear fuel particles and a method for its preparation

    SciTech Connect

    Hein, K.

    1983-05-24

    Sorbitol, or another polyalcohol such as erythritol, dulcitol or xylitol, is added to a solution containing uranyl nitrate which may also contain another heavy metal, such as thorium or plutonium, prior to preneutralization with ammonia in order to provide a highly viscous solution that can be preneutralized to a great extent without premature precipitation of uranium. The high viscosity makes possible the formation of favorably large drops when the solution is dripped into an ammonia containing bath for external gelification of the drops. According to the pouring apparatus used, the particles after washing, drying and sintering have a diameter between 0.6 and 1.5 mm. The polyalcohol is added to a hydrosol containing from 1.5 to 2 moles per liter of heavy metal, the polyalcohol being added until concentration of onethird mole of polyalcohol per mole of heavy metal is reached. In certain cases up to four moles of ammonium nitrate per liter are added. The solution so produced can be preneutralized with up to 90% of the amount of ammonia stoichiometrically necessary for T separation of uranium without the formation of any precipitate, preferably by first adding ammonia gas under strong stirring and then adding ammonium bicarbonate in excess, which decomposes to liberate ammonia to an extent determined by the temperature, which is to be precisely controlled. It is possible to obtain this way a solution of predetermined viscosity from which the excess ammonium bicarbonate can readily be separated.

  3. Critical Parameters of Complex Geometries of Intersecting Cylinders Containing Uranyl Nitrate Solution

    SciTech Connect

    J. B. Briggs; R. E. Rothe

    1999-06-14

    About three dozen previously unreported critical configurations are presented for very complex geometries filled with high concentration enriched uranyl nitrate solution. These geometries resemble a tall, thin Central Column (or trunk of a ''tree'') having long, thin arms (or ''branches'') extending up to four directions off the column. Arms are equally spaced from one another in vertical planes, and that spacing ranges from arms in contact to quite wide spacings. Both the Central Column and the many different arms are critically safe by themselves with each, alone, is filled with fissile solution; but, in combination, criticality occurs due to the interactions between arms and the column. Such neutronic interactions formed the principal focus of this study. While these results are fresh to the nuclear criticality safety industry and to those seeking novel experiments against which to validate computer codes, the experiments, themselves, are not recent. Over 100 experiments were performed at the Rocky Flats Critical Mass Laboratory between September, 1967, and February of the following year.

  4. Critical Parameters of Complex Geometry Intersecting Cylinders Containing Uranyl Nitrate Solution

    SciTech Connect

    Rothe, Robert Emil; Briggs, Joseph Blair

    1999-06-01

    About three dozen previously unreported critical configurations are presented for very complex geometries filled with high concentration enriched uranyl nitrate solution. These geometries resemble a tall, thin Central Column (or trunk of a "tree") having long, thin arms (or "branches") extending up to four directions off the column. Arms are equally spaced from one another in vertical planes; and that spacing ranges from arms in contact to quite wide spacings. Both the Central Column and the many different arms are critically safe by themselves when each, alone, is filled with fissile solution; but, in combination, criticality occurs due to the interactions between arms and the column. Such neutronic interactions formed the principal focus of this study. While these results are fresh to the nuclear criticality safety industry and to those seeking novel experiments against which to validate computer codes, the experiments, themselves, are not recent. Over 100 experiments were performed at the Rocky Flats Critical Mass Laboratory between September, 1967, and February of the following year.

  5. Highly Enriched Uranyl Nitrate in Annular Tanks with Concrete Reflection: 1 x 3 Line Array of Nested Pairs of Tanks

    SciTech Connect

    James Cleaver; John D. Bess; Nathan Devine; Fitz Trumble

    2009-09-01

    A series of seven experiments were performed at the Rocky Flats Critical Mass Laboratory beginning in August, 1980 (References 1 and 2). Highly enriched uranyl nitrate solution was introduced into a 1-3 linear array of nested stainless steel annular tanks. The tanks were inside a concrete enclosure, with various moderator and absorber materials placed inside and/or between the tanks. These moderators and absorbers included boron-free concrete, borated concrete, borated plaster, and cadmium. Two configurations included placing bottles of highly enriched uranyl nitrate between tanks externally. Another experiment involved nested hemispheres of highly enriched uranium placed between tanks externally. These three configurations are not evaluated in this report. The experiments evaluated here are part of a series of experiments, one set of which is evaluated in HEU-SOL-THERM-033. The experiments in this and HEU-SOL-THERM-033 were performed similarly. They took place in the same room and used the same tanks, some of the same moderators and absorbers, some of the same reflector panels, and uranyl nitrate solution from the same location. There are probably additional similarities that existed that are not identified here. Thus, many of the descriptions in this report are either the same or similar to those in the HEU-SOL-THERM-033 report. Seventeen configurations (sixteen of which were critical) were performed during seven experiments; six of those experiments are evaluated here with thirteen configurations. Two configurations were identical, except for solution height, and were conducted to test repeatability. The solution heights were averaged and the two were evaluated as one configuration, which gives a total of twelve evaluated configurations. One of the seventeen configurations was subcritical. Of the twelve critical configurations evaluated, nine were judged as acceptable as benchmarks.

  6. Uranyl(VI) nitrate salts: modeling thermodynamic properties using the binding mean spherical approximation theory and determination of "fictive" binary data.

    PubMed

    Ruas, Alexandre; Bernard, Olivier; Caniffi, Barbara; Simonin, Jean-Pierre; Turq, Pierre; Blum, Lesser; Moisy, Philippe

    2006-02-23

    This work is aimed at a description of the thermodynamic properties of highly concentrated aqueous solutions of uranyl nitrate at 25 degrees C. A new resolution of the binding mean spherical approximation (BIMSA) theory, taking into account 1-1 and also 1-2 complex formation, is developed and used to reproduce, from a simple procedure, experimental uranyl nitrate osmotic coefficient variation with concentration. For better consistency of the theory, binary uranyl perchlorate and chloride osmotic coefficients are also calculated. Comparison of calculated and experimental values is made. The possibility of regarding the ternary system UO(2)(NO(3))(2)/HNO(3)/H(2)O as a "simple" solution (in the sense of Zdanovskii, Stokes, and Robinson) is examined from water activity and density measurements. Also, an analysis of existing uranyl nitrate binary data is proposed and compared with our obtained data. On the basis of the concept of "simple" solution, values for density and water activity for the binary system UO(2)(NO(3))(2)/H(2)O are proposed in a concentration range on which uranyl nitrate precipitates from measurements on concentrated solutions of the ternary system UO(2)(NO(3))(2)/HNO(3)/H(2)O. This new set of binary data is "fictive" in the sense that the real binary system is not stable chemically. Finally, a new, interesting predictive capability of the BIMSA theory is shown.

  7. Acute exposure of uranyl nitrate causes lipid peroxidation and histopathological damage in brain and bone of Wistar rat.

    PubMed

    Ghosh, Somnath; Kumar, Amit; Pandey, Badri Narain; Mishra, Kaushala Prasad

    2007-01-01

    Although the kidneys are the main target organs for uranium (U) toxicity, recent studies have shown that U can cross the blood-brain barrier to accumulate in the brain. Uranyl nitrate (U-238)induced oxidative damage was investigated in brain and bone of Wistar rats after intraperitoneal injection of uranyl nitrate at acute doses either nephrotoxic (576 microg of U/kg body weight) or subnephrotoxic (144 microg U/kg body weight). The health effects of U administration at 576 microg of U/kg body weight were seen in terms of decrease in food intake and no gain in body weight compared to respective controls. These alterations were correlated with increased lipid peroxidation as measured by thiobarbituric acid reactive substances in rat brain and bone. However, at lower dosage of U (144 microg U/kg body weight), no significant lipid peroxidation was observed in brain and bone. Histological examination of U-treated (576 microg of U/kg body weight) rat brain tissues showed marked and diffuse cystic degeneration and a similar pattern in histological alterations was observed in kidneys in treated animals; whereas no significant histological change was observed in rat brains and kidney treated with a lower dose of U (144 microg U/kg body weight). It is concluded that administration of U at an acute nephrotoxic dose caused oxidative stress in brain and bone manifested as lipid peroxidation and histopathological damage.

  8. Dehydration of uranyl nitrate hexahydrate to the trihydrate under ambient conditions as observed via dynamic infrared reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Johnson, Timothy J.; Sweet, Lucas E.; Meier, David E.; Mausolf, Edward J.; Kim, Eunja; Weck, Philippe F.; Buck, Edgar C.; McNamara, Bruce K.

    2015-05-01

    Uranyl nitrate is a key species in the nuclear fuel cycle, but is known to exist in different states of hydration, including the hexahydrate [UO2(NO3)2(H2O)6] (UNH) and the trihydrate [UO2(NO3)2(H2O)3] (UNT) forms. Their stabilities depend on both relative humidity and temperature. Both phases have previously been studied by infrared transmission spectroscopy, but the data were limited by both instrumental resolution and the ability to prepare the samples as pellets without desiccating it. We report time-resolved infrared (IR) measurements using an integrating sphere that allow us to observe the transformation from the hexahydrate to the trihydrate simply by flowing dry nitrogen gas over the sample. Hexahydrate samples were prepared and confirmed via known XRD patterns, then measured in reflectance mode. The hexahydrate has a distinct uranyl asymmetric stretch band at 949.0 cm-1 that shifts to shorter wavelengths and broadens as the sample dehydrates and recrystallizes to the trihydrate, first as a blue edge shoulder but ultimately resulting in a doublet band with reflectance peaks at 966 and 957 cm-1. The data are consistent with transformation from UNH to UNT since UNT has two non-equivalent UO22+ sites. The dehydration of UO2(NO3)2(H2O)6 to UO2(NO3)2(H2O)3 is both a morphological and structural change that has the lustrous lime green crystals changing to the dull greenish yellow of the trihydrate. Crystal structures and phase transformation were confirmed theoretically using DFT calculations and experimentally via microscopy methods. Both methods showed a transformation with two distinct sites for the uranyl cation in the trihydrate, as opposed to a single crystallographic site in the hexahydrate.

  9. Conversion and Blending Facility highly enriched uranium to low enriched uranium as uranyl nitrate hexahydrate. Revision 1

    SciTech Connect

    1995-07-05

    This Conversion and Blending Facility (CBF) will have two missions: (1) convert HEU materials to pure HEU uranyl nitrate (UNH) and (2) blend pure HEU UNH with depleted and natural UNH to produce HEU UNH crystals. The primary emphasis of this blending operation will be to destroy the weapons capability of large, surplus stockpiles of HEU. The blended LEU product can only be made weapons capable again by the uranium enrichment process. To the extent practical, the chemical and isotopic concentrations of blended LEU product will be held within the specifications required for LWR fuel. Such blended LEU product will be offered to the United States Enrichment Corporation (USEC) to be sold as feed material to the commercial nuclear industry. Otherwise, blended LEU Will be produced as a waste suitable for storage or disposal.

  10. Time-Resolved Infrared Reflectance Studies of the Dehydration-Induced Transformation of Uranyl Nitrate Hexahydrate to the Trihydrate Form

    SciTech Connect

    Johnson, Timothy J.; Sweet, Lucas E.; Meier, David E.; Mausolf, Edward J.; Kim, Eunja; Weck, Philippe F.; Buck, Edgar C.; McNamara, Bruce K.

    2015-10-01

    Uranyl nitrate is a key species in the nuclear fuel cycle. However, this species is known to exist in different states of hydration, including the hexahydrate ([UO2(NO3)2(H2O)6] often called UNH), the trihydrate [UO2(NO3)2(H2O)3 or UNT], and in very dry environments the dihydrate form [UO2(NO3)2(H2O)2]. Their relative stabilities depend on both water vapor pressure and temperature. In the 1950s and 1960s the different phases were studied by infrared transmission spectroscopy, but were limited both by instrumental resolution and by the ability to prepare the samples for transmission. We have revisited this problem using time-resolved reflectance spectroscopy, which requires no sample preparation and allows dynamic analysis while the sample is exposed to a flow of N2 gas. Samples of known hydration state were prepared and confirmed via X-ray diffraction patterns of known species. In reflectance mode the hexahydrate UO2(NO3)2(H2O)6 has a distinct uranyl asymmetric stretch band at 949.0 cm-1 that shifts to shorter wavelengths and broadens as the sample desiccates and recrystallizes to the trihydrate, first as a shoulder growing in on the blue edge but ultimately results in a doublet band with reflectance peaks at 966 and 957 cm-1. The data are consistent with transformation from UNH to UNT as UNT has two inequivalent UO22+ sites. The dehydration of UO2(NO3)2(H2O)6 to UO2(NO3)2(H2O)3 is both a structural and morphological change that has the lustrous lime green UO2(NO3)2(H2O)6 crystals changing to the matte greenish yellow of the trihydrate solid. The phase transformation and crystal structures were confirmed by density functional theory calculations and optical microscopy methods, both of which showed a transformation with two distinct sites for the uranyl cation in the trihydrate, with but one in the hexahydrate.

  11. Time-resolved infrared reflectance studies of the dehydration-induced transformation of uranyl nitrate hexahydrate to the trihydrate form

    DOE PAGES

    Johnson, Timothy J.; Sweet, Lucas E.; Meier, David E.; Edward J. Mausolf; Kim, Eunja; Weck, Philippe F.; Buck, Edgar C.; Bruce K. McNamara

    2015-09-08

    Uranyl nitrate is a key species in the nuclear fuel cycle. However, this species is known to exist in different states of hydration, including the hexahydrate ([UO2(NO3)2(H2O)6] often called UNH), the trihydrate [UO2(NO3)2(H2O)3 or UNT], and in very dry environments the dihydrate form [UO2(NO3)2(H2O)2]. Their relative stabilities depend on both water vapor pressure and temperature. In the 1950s and 1960s, the different phases were studied by infrared transmission spectroscopy but were limited both by instrumental resolution and by the ability to prepare the samples for transmission. We have revisited this problem using time-resolved reflectance spectroscopy, which requires no sample preparationmore » and allows dynamic analysis while the sample is exposed to a flow of N2 gas. Samples of known hydration state were prepared and confirmed via X-ray diffraction patterns of known species. In reflectance mode the hexahydrate UO2(NO3)2(H2O)6 has a distinct uranyl asymmetric stretch band at 949.0 cm–1 that shifts to shorter wavelengths and broadens as the sample desiccates and recrystallizes to the trihydrate, first as a shoulder growing in on the blue edge but ultimately results in a doublet band with reflectance peaks at 966 and 957 cm–1. The data are consistent with transformation from UNH to UNT as UNT has two inequivalent UO22+ sites. The dehydration of UO2(NO3)2(H2O)6 to UO2(NO3)2(H2O)3 is both a structural and morphological change that has the lustrous lime green UO2(NO3)2(H2O)6 crystals changing to the matte greenish yellow of the trihydrate solid. As a result, the phase transformation and crystal structures were confirmed by density functional theory calculations and optical microscopy methods, both of which showed a transformation with two distinct sites for the uranyl cation in the trihydrate, with only one in the hexahydrate.« less

  12. Time-resolved infrared reflectance studies of the dehydration-induced transformation of uranyl nitrate hexahydrate to the trihydrate form

    SciTech Connect

    Johnson, Timothy J.; Sweet, Lucas E.; Meier, David E.; Edward J. Mausolf; Kim, Eunja; Weck, Philippe F.; Buck, Edgar C.; Bruce K. McNamara

    2015-09-08

    Uranyl nitrate is a key species in the nuclear fuel cycle. However, this species is known to exist in different states of hydration, including the hexahydrate ([UO2(NO3)2(H2O)6] often called UNH), the trihydrate [UO2(NO3)2(H2O)3 or UNT], and in very dry environments the dihydrate form [UO2(NO3)2(H2O)2]. Their relative stabilities depend on both water vapor pressure and temperature. In the 1950s and 1960s, the different phases were studied by infrared transmission spectroscopy but were limited both by instrumental resolution and by the ability to prepare the samples for transmission. We have revisited this problem using time-resolved reflectance spectroscopy, which requires no sample preparation and allows dynamic analysis while the sample is exposed to a flow of N2 gas. Samples of known hydration state were prepared and confirmed via X-ray diffraction patterns of known species. In reflectance mode the hexahydrate UO2(NO3)2(H2O)6 has a distinct uranyl asymmetric stretch band at 949.0 cm–1 that shifts to shorter wavelengths and broadens as the sample desiccates and recrystallizes to the trihydrate, first as a shoulder growing in on the blue edge but ultimately results in a doublet band with reflectance peaks at 966 and 957 cm–1. The data are consistent with transformation from UNH to UNT as UNT has two inequivalent UO22+ sites. The dehydration of UO2(NO3)2(H2O)6 to UO2(NO3)2(H2O)3 is both a structural and morphological change that has the lustrous lime green UO2(NO3)2(H2O)6 crystals changing to the matte greenish yellow of the

  13. Uranyl Nitrate Flow Loop

    SciTech Connect

    Ladd-Lively, Jennifer L

    2008-10-01

    The objectives of the work discussed in this report were to: (1) develop a flow loop that would simulate the purified uranium-bearing aqueous stream exiting the solvent extraction process in a natural uranium conversion plant (NUCP); (2) develop a test plan that would simulate normal operation and disturbances that could be anticipated in an NUCP; (3) use the flow loop to test commercially available flowmeters for use as safeguards monitors; and (4) recommend a flowmeter for production-scale testing at an NUCP. There has been interest in safeguarding conversion plants because the intermediate products [uranium dioxide (UO{sub 2}), uranium tetrafluoride (UF{sub 4}), and uranium hexafluoride (UF{sub 6})] are all suitable uranium feedstocks for producing special nuclear materials. Furthermore, if safeguards are not applied virtually any nuclear weapons program can obtain these feedstocks without detection by the International Atomic Energy Agency (IAEA). Historically, IAEA had not implemented safeguards until the purified UF{sub 6} product was declared as feedstock for enrichment plants. H. A. Elayat et al. provide a basic definition of a safeguards system: 'The function of a safeguards system on a chemical conversion plant is in general terms to verify that no useful nuclear material is being diverted to use in a nuclear weapons program'. The IAEA now considers all highly purified uranium compounds as candidates for safeguarding. DOE is currently interested in 'developing instruments, tools, strategies, and methods that could be of use to the IAEA in the application of safeguards' for materials found in the front end of the nuclear fuel cycle-prior to the production of the uranium hexafluoride or oxides that have been the traditional starting point for IAEA safeguards. Several national laboratories, including Oak Ridge, Los Alamos, Lawrence Livermore, and Brookhaven, have been involved in developing tools or techniques for safeguarding conversion plants. This study was sponsored by the U.S. Department of Energy (DOE) NA-241, Office of Dismantlement and Transparency.

  14. Behaviors of acrylamide/itaconic acid hydrogels in uptake of uranyl ions from aqueous solutions

    SciTech Connect

    Karadag, E.; Saraydin, D.; Gueven, O.

    1995-12-01

    In this study, adsorptions of uranyl ions from two different aqueous uranyl solutions by acrylamide-itaconic acid hydrogels were investigated by a spectroscopic method. The hydrogels were prepared by irradiating with {gamma}-radiation. In the experiment of uranyl ions adsorption, Type II adsorption was found. One gram of acrylamide-itaconic acid hydrogels sorbed 178-219 mg uranyl ions from the solutions of uranyl acetate, 42-76 mg uranyl ions from the aqueous solutions of uranyl nitrate, while acrylamide hydrogel did not sorb any uranyl ion. For the hydrogel containing 40 mg of itaconic acid and irradiated to 3.73 kGy, swelling of the hydrogels was observed in water (1660%), in the aqueous solution of uranyl acetate (730%), and in the aqueous solution of uranyl nitrate (580%). Diffusions of water onto hydrogels were a non-Fickian type of diffusion, whereas diffusions of uranyl ions were a Fickian type of diffusion.

  15. Mechanistic Features of the TiO2 Heterogeneous Photocatalysis of Arsenic and Uranyl Nitrate in Aqueous Suspensions Studied by the Stopped-Flow Technique.

    PubMed

    Meichtry, Jorge M; Levy, Ivana K; Mohamed, Hanan H; Dillert, Ralf; Bahnemann, Detlef W; Litter, Marta I

    2016-03-16

    The dynamics of the transfer of electrons stored in TiO2 nanoparticles to As(III) , As(V) , and uranyl nitrate in water was investigated by using the stopped-flow technique. Suspensions of TiO2 nanoparticles with stored trapped electrons (etrap (-) ) were mixed with solutions of acceptor species to evaluate the reactivity by following the temporal evolution of etrap (-) by the decrease in the absorbance at λ=600 nm. The results indicate that As(V) and As(III) cannot be reduced by etrap (-) under the reaction conditions. In addition, it was observed that the presence of As(V) and As(III) strongly modified the reaction rate between O2 and etrap (-) : an increase in the rate was observed if As(V) was present and a decrease in the rate was observed in the presence of As(III) . In contrast with the As system, U(VI) was observed to react easily with etrap (-) and U(IV) formation was observed spectroscopically at λ=650 nm. The possible competence of U(VI) and NO3 (-) for their reduction by etrap (-) was analyzed. The inhibition of the U(VI) photocatalytic reduction by O2 could be attributed to the fast oxidation of U(V) and/or U(IV) .

  16. Method for photochemical reduction of uranyl nitrate by tri-N-butyl phosphate and application of this method to nuclear fuel reprocessing

    DOEpatents

    De Poorter, Gerald L.; Rofer-De Poorter, Cheryl K.

    1978-01-01

    Uranyl ion in solution in tri-n-butyl phosphate is readily photochemically reduced to U(IV). The product U(IV) may effectively be used in the Purex process for treating spent nuclear fuels to reduce Pu(IV) to Pu(III). The Pu(III) is readily separated from uranium in solution in the tri-n-butyl phosphate by an aqueous strip.

  17. Nitrate

    Integrated Risk Information System (IRIS)

    Nitrate ; CASRN 14797 - 55 - 8 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic Effects

  18. Uranyl ion coordination

    USGS Publications Warehouse

    Evans, H.T.

    1963-01-01

    A review of the known crystal structures containing the uranyl ion shows that plane-pentagon coordination is equally as prevalent as plane-square or plane-hexagon. It is suggested that puckered-hexagon configurations of OH - or H2O about the uranyl group will tend to revert to plane-pentagon coordination. The concept of pentagonal coordination is invoked for possible explanations of the complex crystallography of the natural uranyl hydroxides and the unusual behavior of polynuclear ions in hydrolyzed uranyl solutions.

  19. Composition for detecting uranyl

    DOEpatents

    Baylor, Lewis C.; Stephens, Susan M.

    1995-01-01

    A composition for detecting the presence and concentration of a substance such as uranyl, comprising an organohalide covalently bonded to an indicator for said substance. The composition has at least one active OH site for forming a complex with the substance to be detected. The composition is made by reacting equimolar amounts of the indicator and the organohalide in a polar organic solvent. The absorbance spectrum of the composition-uranyl complex is shifted with respect to the absorbance spectrum of the indicator-uranyl complex, to provide better spectral resolution for detecting uranyl.

  20. FLAME DENITRATION AND REDUCTION OF URANIUM NITRATE TO URANIUM DIOXIDE

    DOEpatents

    Hedley, W.H.; Roehrs, R.J.; Henderson, C.M.

    1962-06-26

    A process is given for converting uranyl nitrate solution to uranium dioxide. The process comprises spraying fine droplets of aqueous uranyl nitrate solution into a hightemperature hydrocarbon flame, said flame being deficient in oxygen approximately 30%, retaining the feed in the flame for a sufficient length of time to reduce the nitrate to the dioxide, and recovering uranium dioxide. (AEC)

  1. Essential fatty acid deficiency in malnourished children.

    PubMed

    Holman, R T; Johnson, S B; Mercuri, O; Itarte, H J; Rodrigo, M A; De Tomas, M E

    1981-08-01

    Fatty acid patterns of major classes of lipids of serum were measured in forty Argentine children ages 2 to 24 months admitted to the hospital with chronic malnutrition. A normal control group of 48 children from the same population was also examined. Serum lipids were extracted and separated into phospholipids, cholesteryl esters, triglycerides, and free fatty acids. These were converted to methyl esters which were analyzed by gas chromatography. In chronic malnutrition, the fatty acid patterns of phospholipids and cholesteryl esters indicated changes characteristic of essential fatty acid deficiency of moderate degree. The total omega 6 acids were found to be highly significantly diminished from normal, and the ratio of 20:3 omega 9/20:4 omega 6 was highly significantly increased. Decreased proportions of omega 6 metabolites suggested impaired desaturase activity, and elevated ratios of 22:4 omega 6/20:4 omega 6 and 20:2 omega 6/18:2 omega 6 suggested increased chain elongation in chronic malnutrition.

  2. Faster clearance of omeprazole in rats with acute renal failure induced by uranyl nitrate: contribution of increased expression of hepatic cytochrome P450 (CYP) 3A1 and intestinal CYP1A and 3A subfamilies.

    PubMed

    Lee, Dae Y; Jung, Young S; Shin, Hyun S; Lee, Inchul; Kim, Young C; Lee, Myung G

    2008-07-01

    It has been reported that omeprazole is mainly metabolized via hepatic cytochrome P450 (CYP) 1A1/2, CYP2D1 and CYP3A1/2 in male Sprague-Dawley rats, and the expression of hepatic CYP3A1 is increased in male Sprague-Dawley rats with acute renal failure induced by uranyl nitrate (U-ARF rats). Thus, the metabolism of omeprazole would be expected to increase in U-ARF rats. After intravenous administration of omeprazole (20 mgkg(-1)) to U-ARF rats, the area under the plasma concentration-time curve from time zero to infinity (AUC) was significantly reduced (371 vs 494 microg min mL(-1)), possibly due to the significantly faster non-renal clearance (56.6 vs 41.2 mL min(-1) kg(-1)) compared with control rats. This could have been due to increased expression of hepatic CYP3A1 in U-ARF rats. After oral administration of omeprazole (40 mgkg(-1)) to U-ARF rats, the AUC was also significantly reduced (89.3 vs 235 microg min mL(-1)) compared with control rats. The AUC difference after oral administration (62.0% decrease) was greater than that after intravenous administration (24.9% decrease). This may have been primarily due to increased intestinal metabolism of omeprazole caused by increased expression of intestinal CYP1A and 3A subfamilies in U-ARF rats, in addition to increased hepatic metabolism.

  3. Photocatalytic oxidation by uranyl

    SciTech Connect

    McCleskey, T.M.; Tumas, W.; Burns, C.J.

    1995-12-01

    The excited state of uranyl (UO{sub 2}{sup 2+}*) is a potent oxidant (E{sup 0}(UO{sub 2}{sup 2+}*/UO{sub 2}{sup +}) {approx} 2.5 V) which can be quenched by either electron transfer (ET) or H atom abstraction. We have investigated both types of quenching with a variety of organic substrates in water and acetone/water media. Excited-state reactions with alkenes proceed by ET to form cation radicals, while reactions with tertiary alkanes follow an H-atom abstraction pathway. In aqueous media uranyl photocatalytically decomposes tert-butyl peroxide in a manner analogous to Fenton-type chemistry.

  4. Uranyl Precipitation by Pseudomonas aeruginosa via Controlled Polyphosphate Metabolism

    PubMed Central

    Renninger, Neil; Knopp, Roger; Nitsche, Heino; Clark, Douglas S.; Keasling, Jay D.

    2004-01-01

    The polyphosphate kinase gene from Pseudomonas aeruginosa was overexpressed in its native host, resulting in the accumulation of 100 times the polyphosphate seen with control strains. Degradation of this polyphosphate was induced by carbon starvation conditions, resulting in phosphate release into the medium. The mechanism of polyphosphate degradation is not clearly understood, but it appears to be associated with glycogen degradation. Upon suspension of the cells in 1 mM uranyl nitrate, nearly all polyphosphate that had accumulated was degraded within 48 h, resulting in the removal of nearly 80% of the uranyl ion and >95% of lesser-concentrated solutions. Electron microscopy, energy-dispersive X-ray spectroscopy, and time-resolved laser-induced fluorescence spectroscopy (TRLFS) suggest that this removal was due to the precipitation of uranyl phosphate at the cell membrane. TRLFS also indicated that uranyl was initially sorbed to the cell as uranyl hydroxide and was then precipitated as uranyl phosphate as phosphate was released from the cell. Lethal doses of radiation did not halt phosphate secretion from polyphosphate-filled cells under carbon starvation conditions. PMID:15574942

  5. Rapid Self-Assembly of Uranyl Polyhedra into Crown Clusters

    SciTech Connect

    Sigmon, Ginger E.; Burns, Peter C.

    2011-06-22

    Clusters built from 32 uranyl peroxide polyhedra self-assemble and crystallize within 15 min after combining uranyl nitrate, ammonium hydroxide, and hydrogen peroxide in aqueous solution under ambient conditions. These novel crown-shaped clusters are remarkable in that they form so quickly, have extraordinarily low aqueous solubility, form with at least two distinct peroxide to hydroxyl ratios, and form in very high yield. The clusters, which have outer diameters of 23 Å, topologically consist of eight pentagons and four hexagons. Their rapid formation and low solubility in aqueous systems may be useful properties at various stages in an advanced nuclear energy system.

  6. Extraction of local coordination structure in a low-concentration uranyl system by XANES.

    PubMed

    Zhang, Linjuan; Zhou, Jing; Zhang, Jianyong; Su, Jing; Zhang, Shuo; Chen, Ning; Jia, Yunpeng; Li, Jiong; Wang, Yu; Wang, Jian Qiang

    2016-05-01

    Obtaining structural information of uranyl species at an atomic/molecular scale is a critical step to control and predict their physical and chemical properties. To obtain such information, experimental and theoretical L3-edge X-ray absorption near-edge structure (XANES) spectra of uranium were studied systematically for uranyl complexes. It was demonstrated that the bond lengths (R) in the uranyl species and relative energy positions (ΔE) of the XANES were determined as follows: ΔE1 = 168.3/R(U-Oax)(2) - 38.5 (for the axial plane) and ΔE2 = 428.4/R(U-Oeq)(2) - 37.1 (for the equatorial plane). These formulae could be used to directly extract the distances between the uranium absorber and oxygen ligand atoms in the axial and equatorial planes of uranyl ions based on the U L3-edge XANES experimental data. In addition, the relative weights were estimated for each configuration derived from the water molecule and nitrate ligand based on the obtained average equatorial coordination bond lengths in a series of uranyl nitrate complexes with progressively varied nitrate concentrations. Results obtained from XANES analysis were identical to that from extended X-ray absorption fine-structure (EXAFS) analysis. XANES analysis is applicable to ubiquitous uranyl-ligand complexes, such as the uranyl-carbonate complex. Most importantly, the XANES research method could be extended to low-concentration uranyl systems, as indicated by the results of the uranyl-amidoximate complex (∼40 p.p.m. uranium). Quantitative XANES analysis, a reliable and straightforward method, provides a simplified approach applied to the structural chemistry of actinides. PMID:27140156

  7. Pillared and open-framework uranyl diphosphonates

    SciTech Connect

    Adelani, Pius O.; Albrecht-Schmitt, Thomas E.

    2011-09-15

    The hydrothermal reactions of uranium trioxide, uranyl acetate, or uranyl nitrate with 1,4-benzenebisphosphonic acid in the presence of very small amount of HF at 200 deg. C results in the formation of three different uranyl diphosphonate compounds, [H{sub 3}O]{sub 2}{l_brace}(UO{sub 2}){sub 6}[C{sub 6}H{sub 4}(PO{sub 3})(PO{sub 2}OH)]{sub 2}[C{sub 6}H{sub 4}(PO{sub 2}OH){sub 2}]{sub 2}[C{sub 6}H{sub 4}(PO{sub 3}){sub 2}]{r_brace}(H{sub 2}O){sub 2} (Ubbp-1), [H{sub 3}O]{sub 4}{l_brace}(UO{sub 2}){sub 4}[C{sub 6}H{sub 4}(PO{sub 3}){sub 2}]{sub 2}F{sub 4}{r_brace}.H{sub 2}O (Ubbp-2), and {l_brace}(UO{sub 2})[C{sub 6}H{sub 2}F{sub 2}(PO{sub 2}OH){sub 2}(H{sub 2}O){r_brace}{sub 2}.H{sub 2}O (Ubbp-3). The crystal structures of these compounds were determined by single crystal X-ray diffraction experiments. Ubbp-1 consists of UO{sub 7} pentagonal bipyramids that are bridged by the phosphonate moieties to form a three-dimensional pillared structure. Ubbp-2 is composed of UO{sub 5}F{sub 2} pentagonal bipyramids that are bridged through the phosphonate oxygen atoms into one-dimensional chains that are cross-linked by the phenyl spacers into a pillared structure. The structure of Ubbp-3 is a three-dimensional open-framework with large channels containing water molecules with internal dimensions of approximately 10.9x10.9 A. Ubbp-1 and Ubbp-2 fluoresce at room temperature. - Graphical Abstract: Illustration of the three-dimensional open-framework structure of {l_brace}(UO{sub 2})[C{sub 6}H{sub 2}F{sub 2}(PO{sub 2}OH){sub 2}(H{sub 2}O){r_brace}{sub 2}.H{sub 2}O viewed along the c-axis. The structure is constructed from UO{sub 7} units, pentagonal bipyramids=green, oxygen=red, phosphorus=magenta, carbon=black, hydrogen=white. Highlights: > The influence of the uranyl salt anions and pH were critically examined in relation to structural variation. > The acetate and nitrate counter ions of uranyl may be acting as structure directing agents. > The use of rigid phenyl spacer yield

  8. Barium uranyl diphosphonates

    SciTech Connect

    Nelson, Anna-Gay D.; Alekseev, Evgeny V.; Ewing, Rodney C.; Albrecht-Schmitt, Thomas E.

    2012-08-15

    Three Ba{sup 2+}/UO{sub 2}{sup 2+} methylenediphosphonates have been prepared from mild hydrothermal treatment of uranium trioxide, methylendiphosphonic acid (C1P2) with barium hydroxide octahydrate, barium iodate monohydrate, and small aliquots of HF at 200 Degree-Sign C. These compounds, Ba[UO{sub 2}[CH{sub 2}(PO{sub 3}){sub 2}]{center_dot}1.4H{sub 2}O (Ba-1), Ba{sub 3}[(UO{sub 2}){sub 4}(CH{sub 2}(PO{sub 3}){sub 2}){sub 2}F{sub 6}]{center_dot}6H{sub 2}O (Ba-2), and Ba{sub 2}[(UO{sub 2}){sub 2}(CH{sub 2}(PO{sub 3}){sub 2})F{sub 4}]{center_dot}5.75H{sub 2}O (Ba-3) all adopt layered structures based upon linear uranyl groups and disphosphonate molecules. Ba-2 and Ba-3 are similar in that they both have UO{sub 5}F{sub 2} pentagonal bipyramids that are bridged and chelated by the diphosphonate moiety into a two-dimensional zigzag anionic sheet (Ba-2) and a one-dimensional ribbon anionic chain (Ba-3). Ba-1, has a single crystallographically unique uranium metal center where the C1P2 ligand solely bridges to form [UO{sub 2}[CH{sub 2}(PO{sub 3}){sub 2}]{sup 2-} sheets. The interlayer space of the structures is occupied by Ba{sup 2+}, which, along with the fluoride ion, mediates the structure formed and maintains overall charge balance. - Graphical abstract: Illustration of the stacking of the layers in Ba{sub 3}[(UO{sub 2}){sub 4}(CH{sub 2}(PO{sub 3}){sub 2}){sub 2})F{sub 6}]{center_dot}6H{sub 2}O viewed along the c-axis. The structure is constructed from UO{sub 7} pentagonal bipyramidal units, U(1)O{sub 7}=gray, U(2)O{sub 7}=yellow, barium=blue, phosphorus=magenta, fluorine=green, oxygen=red, carbon=black, and hydrogen=light peach. Highlights: Black-Right-Pointing-Pointer The polymerization of the UO{sub 2}{sup 2+} sites to form uranyl dimers leads to structural variations in compounds. Black-Right-Pointing-Pointer Barium cations stitch uranyl diphosphonate anionic layers together, and help mediate structure formation. Black-Right-Pointing-Pointer HF acts as both a

  9. Composition for detecting uranyl

    DOEpatents

    Baylor, L.C.; Stephens, S.M.

    1994-01-01

    The present invention relates to an indicator composition for use in spectrophotometric detection of a substance in a solution, and a method for making the composition. Useful indicators are sensitive to the particular substance being measured, but are unaffected by the fluid and other chemical species that may be present in the fluid. Optical indicators are used to measure the uranium concentration of process solutions in facilities for extracting uranium from ores, production of nuclear fuels, and reprocessing of irradiated fuels. The composition comprises an organohalide covalently bonded to an indicator for the substance, in such a manner that the product is itself an indicator that provides increased spectral resolution for detecting the substance. The indicator is preferably arsenazo III and the organohalide is preferably cyanuric chloride. These form a composition that is ideally suited for detecting uranyl.

  10. Physical fatty acid deficiency signs in children with ADHD symptoms.

    PubMed

    Sinn, N

    2007-08-01

    Fatty acid deficiency symptoms (FADS) of dry hair and skin, frequent thirst and urination have been observed to be higher in children with attention deficit hyperactivity disorder (ADHD). Two studies investigated FADS in 7-12-year-old children; Study 1 in a general population (N=347) and Study 2 in children with ADHD symptoms (N=104). Correlations between FADS and ADHD-related symptoms were found at baseline in Study 1 but not Study 2. FADS did not improve after supplementation with omega-3 and omega-6 polyunsaturated fatty acids (PUFA) versus placebo after 15 weeks in Study 2, and were not related to improvements in ADHD symptoms in the PUFA groups. However, FADS did improve in all groups, possibly attributable to the linoleic acid present in both the PUFA and placebo (palm oil) supplements. FADS are not a reliable selection criterion for children with ADHD who might benefit from omega-3 PUFA supplementation.

  11. Uranyl ion uptake capacity of poly (N-isopropylacrylamide/maleic acid) copolymeric hydrogels prepared by gamma rays

    NASA Astrophysics Data System (ADS)

    Kam, Erol; Taşdelen, Betul; Osmanlioglu, A. Erdal

    2012-06-01

    The effect of gel composition, absorbed dose and pH of the solution on the uranyl ion uptake capacity of N-isopropylacrylamide/maleic acid copolymeric hydrogels containing 0-3 mol% of maleic acid at 48 kGy have been investigated. Uranyl uptake capacity of hydrogels are found to increase from 18.5 to 94.8 mg [UO22+]/g dry gel as the mole % of maleic acid content in the gel structure increased from 0 to 3. The percent swelling, equilibrium swelling and diffusion coefficient values have been evaluated for poly(N-isopropylacrylamide/maleic acid) hydrogels at 500 ppm of uranyl nitrate solution.

  12. Engineering short peptide sequences for uranyl binding.

    PubMed

    Lebrun, Colette; Starck, Matthieu; Gathu, Vicky; Chenavier, Yves; Delangle, Pascale

    2014-12-01

    Peptides are interesting tools to rationalize uranyl-protein interactions, which are relevant to uranium toxicity in vivo. Structured cyclic peptide scaffolds were chosen as promising candidates to coordinate uranyl thanks to four amino acid side chains pre-oriented towards the dioxo cation equatorial plane. The binding of uranyl by a series of decapeptides has been investigated with complementary analytical and spectroscopic methods to determine the key parameters for the formation of stable uranyl-peptide complexes. The molar ellipticity of the uranyl complex at 195 nm is directly correlated to its stability, which demonstrates that the β-sheet structure is optimal for high stability in the peptide series. Cyclodecapeptides with four glutamate residues exhibit the highest affinities for uranyl with log KC =8.0-8.4 and, therefore, appear as good starting points for the design of high-affinity uranyl-chelating peptides. PMID:25324194

  13. [Pathology of placenta of rats induced by fatty acid deficiency].

    PubMed

    Glocker, T M

    2000-01-01

    Lipids are important cell components, both from the structural and the functional point of view. Besides, they intervene in transporting functions, cell recognition and immunity. Essential Fatty Acids (EFA) are important for the functional and structural maintenance of animal organisms. In our laboratory, it was demonstrated that one group of pregnant rats fed on an EFA deficient diet, and other group of rats fed on the same diet but with 5% of corn oil (rich in linoleic acid) showed alterations on the development of the metrial gland. In the present work, 57 female rats of a Wistar strain were fed since weaning with one of the following diets: EFAD: deficient in essential fatty acids, COD: EFAD + 5% corn oil (linoleic acid sufficient but alpha-linoleic acid deficient); SAD: EFAD + 5% soy oil (both EFA sufficient) and CD: commercial diet. After 3 months the animals were sacrificed on the 13 th. day of gestation. Uteru's horns were dissected and the implantation sities were fixed on formol and embebbed in parafin. The observations were carried out with H/E coloured cross-sections and the corialantoidea placenta, the cities of implantations and the sitios of reabsortions were studied. The metrial gland of DAGE and DAM rats presented structural modifications compared to DC rats. The most relevant findings were: indifferentiation of the granulated metrial gland cells and an increase in the amount of connective tissue. In DAS rats, on the contrary, the aspect of the metrial gland was similar to the observed in the DC group. In the DAGE and the DAM groups Labyrinthium was enlarged with vascular septum group. Mean while DAS was similar to group DC (thin and vascular). Differences in the cities of implantations and reabsortions were not detected. The present results suggest that alpha-linolenico acid is essential for the rat placenta to reach normal development.

  14. Uptake of uranyl ions from uranium ores and sludges by means of Spirulina platensis, Porphyridium cruentum and Nostok linckia alga.

    PubMed

    Cecal, Alexandru; Humelnicu, Doina; Rudic, Valeriu; Cepoi, Liliana; Ganju, Dumitru; Cojocari, Angela

    2012-08-01

    In this paper was studied the uranyl ions biosorption on three types of alga: Nostok linckia, Porphyridium cruentum and Spirulina platensis. These ions were supplied either from a pure solution of uranyl nitrate, or after leaching process of uranium ore, or from the sludge resulting in the output of pure UO(2) technology. It was investigated the retention degree versus contact time and afterwards the Langmuir and Freundlich biosorption isotherms of uranyl ions on the three alga types. The retention of UO(2)(2+) ions on alga was proved through FTIR spectra plotted before and after biosorption processes. From the experimental data it was found that regardless of origin of uranyl ions, the retention degree on alga decreased in the series. Spirulina platensis > Porphyridium cruentum ≥ Nostok linckia.

  15. On the Formation of "Hypercoordinated" Uranyl Complexes

    SciTech Connect

    Schoendorff, George E.; De Jong, Wibe A.; van Stipdonk, Michael J.; Gibson, John K.; Rios, Daniel; Gordon, Mark S.; Windus, Theresa L.

    2011-09-05

    Recent gas phase experimental studies suggest the presence of hypercoordinated uranyl complexes. Coordination of acetone (Ace) to uranyl to form hypercoordinated species is examined using density functional theory (DFT) with a range of functionals and second order perturbation theory (MP2). Complexes with up to eight acetones were studied. It is shown that no more than six acetones can bind directly to uranium and that the observed uranyl complexes are not hypercoordinated.

  16. A Solution-Based Approach for Mo-99 Production: Considerations for Nitrate versus Sulfate Media

    DOE PAGES

    Youker, Amanda J.; Chemerisov, Sergey D.; Kalensky, Michael; Tkac, Peter; Bowers, Delbert L.; Vandegrift, George F.

    2013-01-01

    Molybdenum-99 is the parent of Technetium-99m, which is used in nearly 80% of all nuclear medicine procedures. The medical community has been plagued by Mo-99 shortages due to aging reactors, such as the NRU (National Research Universal) reactor in Canada. There are currently no US producers of Mo-99, and NRU is scheduled for shutdown in 2016, which means that another Mo-99 shortage is imminent unless a potential domestic Mo-99 producer fills the void. Argonne National Laboratory is assisting two potential domestic suppliers of Mo-99 by examining the effects of a uranyl nitrate versus a uranyl sulfate target solution configuration onmore » Mo-99 production. Uranyl nitrate solutions are easier to prepare and do not generate detectable amounts of peroxide upon irradiation, but a high radiation field can lead to a large increase in pH, which can lead to the precipitation of fission products and uranyl hydroxides. Uranyl sulfate solutions are more difficult to prepare, and enough peroxide is generated during irradiation to cause precipitation of uranyl peroxide, but this can be prevented by adding a catalyst to the solution. A titania sorbent can be used to recover Mo-99 from a highly concentrated uranyl nitrate or uranyl sulfate solution; however, different approaches must be taken to prevent precipitation during Mo-99 production.« less

  17. Optical apparatus and method for sensing uranyl

    DOEpatents

    Baylor, L.C.; Buchanan, B.R.

    1994-01-01

    An optical sensing device for uranyl and other substances, a method for making an optical sensing device and a method for chemically binding uranyl and other indicators to glass, quartz, cellulose and similar substrates. The indicator, such as arsenazo III, is immobilized on the substrate using a chemical binding process. The immobilized arsenazo III causes uranyl from a fluid sample to bind irreversibly to the substrate at its active sites, thus causing absorption of a portion of light transmitted through the substrate. Determination of the amount of light absorbed, using conventional means, yields the concentration of uranyl present in the sample fluid. The binding of uranyl on the substrate can be reversed by subsequent exposure of the substrate to a solution of 2,6-pyridinedicarboxylic acid. The chemical binding process is suitable for similarly binding other indicators, such as bromocresol green.

  18. The Uranyl Cation as a Visible-Light Photocatalyst for C(sp(3) )-H Fluorination.

    PubMed

    West, Julian G; Bedell, T Aaron; Sorensen, Erik J

    2016-07-25

    The fluorination of unactivated C(sp(3) )-H bonds remains a desirable and challenging transformation for pharmaceutical, agricultural, and materials scientists. Previous methods for this transformation have used bench-stable fluorine atom sources; however, many still rely on the use of UV-active photocatalysts for the requisite high-energy hydrogen atom abstraction event. Uranyl nitrate hexahydrate is described as a convenient, hydrogen atom abstraction catalyst that can mediate fluorinations of certain alkanes upon activation with visible light. PMID:27320442

  19. Crystal Chemistry of the Potassium and Rubidium Uranyl Borate Families Derived from Boric Acid Fluxes

    SciTech Connect

    Wang, Shuao; Alekseev, Evgeny V.; Stritzinger, Jared T.; Depmeier, Wulf; Albrecht-Schmitt, Thomas E.

    2010-07-19

    The reaction of uranyl nitrate with a large excess of molten boric acid in the presence of potassium or rubidium nitrate results in the formation of three new potassium uranyl borates, K{sub 2}[(UO{sub 2}){sub 2}B{sub 12}O{sub 19}(OH){sub 4}]·0.3H{sub 2}O (KUBO-1), K[(UO{sub 2}){sub 2}B{sub 10}O{sub 15}(OH){sub 5}] (KUBO-2), and K[(UO{sub 2}){sub 2}B{sub 10}O{sub 16}(OH){sub 3}]·0.7H{sub 2}O (KUBO-3) and two new rubidium uranyl borates Rb{sub 2}[(UO{sub 2}){sub 2}B{sub 13}O{sub 20}(OH){sub 5}] (RbUBO-1) and Rb[(UO{sub 2}){sub 2}B{sub 10}O{sub 16}(OH){sub 3}]·0.7H{sub 2}O (RbUBO-2). The latter is isotypic with KUBO-3. These compounds share a common structural motif consisting of a linear uranyl, UO{sub 2}{sup 2+}, cation surrounded by BO{sub 3} triangles and BO{sub 4} tetrahedra to create an UO{sub 8} hexagonal bipyramidal environment around uranium. The borate anions bridge between uranyl units to create sheets. Additional BO{sub 3} triangles extend from the polyborate layers and are directed approximately perpendicular to the sheets. All of these compounds adopt layered structures. With the exception of KUBO-1, the structures are all centrosymmetric. All of these compounds fluoresce when irradiated with long-wavelength UV light. The fluorescence spectrum yields well-defined vibronically coupled charge-transfer features.

  20. Studies of the effects of essential fatty acid deficiency in the rat.

    PubMed

    Cox, J W; Rutecki, G W; Francisco, L L; Ferris, T F

    1982-12-01

    We report a model of prostaglandin depletion induced in rats by fasting for 11 days, followed by institution of an essential fatty acid-deficient diet. Urinary prostaglandin E, 2 weeks after this diet had been implemented, was 22 +/- 2 ng/24 hours compared to 113 +/- 8.5 ng/24 hours in controls (P less than 0.01). There was no difference in 24-hour urine volume or solute excretion in controls and essential fatty acid-deficient rats. Five hours after administration of NaCl, 10 mM/kg, essential fatty acid-deficient diet rats excreted 1.85 +/- 0.78 ml urine compared to 6.42 +/- 2.26 ml in control (p less than 0.01) with Na+ excretion 447 +/- 273 muEq in essential fatty acid-deficient rats vs 1483 +/- 366 muEq in control (P less than 0.01). Intravenous isotonic NaCl, 1.5% body weight, resulted in increased urine flow rate in control rats from 8.3 +/- 2 microliter/min to 28.7 +/- 8.8 microliter/min with sodium excretion increasing from 0.19 +/- 0.2 to 3.3 +/- 0.9 muEq/min. In the essential fatty acid-deficient diet animals, there was no significant change in flow rate, 6.07 +/- 2.43 to 9.85 +/- 4.29 microliter/min, or sodium excretion, 0.09 +/- 0.03 to 0.40 +/- 0.24 muEq, after saline infusion. There was no difference in the glomerular filtration rate of plasma aldosterone in the two groups after the salt load. When given a water load, 3 ml/100 g body weight, essential fatty acid-deficient diet rats excreted 2.5 +/- 0.7 ml in 5 hours compared to 6.3 +/- 1.4 ml in controls (P less than 0.01). The defect in water excretion was not due to increased sensitivity to antidiuretic hormone, since similar sensitivity to this hormone was demonstrated in the essential fatty acid-deficient diet and control rats during a water diuresis. When isotonic saline was substituted for drinking water, there was an increase in systolic blood pressure in essential fatty acid-deficient diet rats from 124 +/- 2 to 142 +/- 3 mm Hg over 9 days (P less than 0.01) compared to 122 +/- 2 before and 122

  1. Histopathology of kidney of albino rat poisoned with uranyl nitrate

    SciTech Connect

    Goel, K.A.; Garg, V.K.; Garg, V.

    1980-01-01

    Heavy metals input into the media either terrestrial or aquatic is an important aspect of environmental pollution. Heavy metals are known to produce toxic effects on the different tissues of various terrestrial and aquatic animals. Some of these are highly toxic at even very low concentrations and they alter the cellular architecture of many organs including the kidney. Little has been done on the effect of rare earth metals, particularly that of uranium on the kidney of animals. In the present paper histopathological changes produced by uranium on the kidney of albino rats are discussed.

  2. Synthesis, structure, and spectroscopic characterization of three uranyl phosphates with unique structural units

    SciTech Connect

    Wylie, Ernest M.; Dawes, Colleen M.; Burns, Peter C.

    2012-12-15

    Single crystals of Zn{sub 4}(OH){sub 2}[(UO{sub 2})(PO{sub 4}){sub 2}(OH){sub 2}(H{sub 2}O)] (UZnP), Cs[(UO{sub 2})(HPO{sub 4})NO{sub 3}] (UCsP), and In{sub 3}[(UO{sub 2}){sub 2}(PO{sub 4}){sub 4}OH(H{sub 2}O){sub 6}].2H{sub 2}O (UInP) were obtained from hydrothermal reactions and have been structurally and chemically characterized. UZnP crystallizes in space group Pbcn, a=8.8817(7), b=6.6109(5), c=19.569(1) A; UCsP crystallizes in P-1, a=7.015(2), b=7.441(1), c=9.393(2) A, {alpha}=72.974(2), {beta}=74.261(2), {gamma}=79.498(2); and UInP crystallizes in P-1, a=7.9856(5), b=9.159(1), c=9.2398(6) A {alpha}=101.289(1), {beta}=114.642(1), {gamma}=99.203(2). The U{sup 6+} cations are present as (UO{sub 2}){sup 2+} uranyl ions coordinated by five O atoms to give pentagonal bipyramids. The structural unit in UZnP is a finite cluster containing a uranyl pentagonal bipyramid that shares corners with two phosphate tetrahedra. The structural unit in UCsP is composed of uranyl pentagonal bipyramids with one chelating nitrate group that are linked into chains by three bridging hydrogen phosphate tetrahedra. In UInP, the structural unit contains pairs of edge-sharing uranyl pentagonal bipyramids with two chelating phosphate tetrahedra that are linked into chains through two bridging phosphate tetrahedra. Indium octahedra link these uranyl phosphate chains into a 3-dimensional framework. All three compounds exhibit unique structural units that deviate from the typical layered structures observed in uranyl phosphate solid-state chemistry. - Graphical abstract: Three new uranyl phosphates with unique structural units are reported. Black-Small-Square Highlights: Black-Right-Pointing-Pointer Three new uranyl phosphates have been synthesized hydrothermally. Black-Right-Pointing-Pointer Single crystal analyses reveal unique structural units. Black-Right-Pointing-Pointer The dimensionality of these compounds deviate from typical U{sup 6+} layered structures.

  3. FY-15 Progress Report on Cleanup of irradiated SHINE Target Solutions Containing 140g-U/L Uranyl Sulfate

    SciTech Connect

    Bennett, Megan E.; Bowers, Delbert L.; Vandegrift, George F.

    2015-09-01

    During FY 2012 and 2013, a process was developed to convert the SHINE Target Solution (STS) of irradiated uranyl sulfate (140 g U/L) to uranyl nitrate. This process is necessary so that the uranium solution can be processed by the UREX (Uranium Extraction) separation process, which will remove impurities from the uranium so that it can be recycled. The uranyl sulfate solution must contain <0.02 M SO42- so that the uranium will be extractable into the UREXsolvent. In addition, it is desired that the barium content be below 0.0007 M, as this is the limit in the Resource Conservation and Recovery Act (RCRA).

  4. Uranyl sensitization of samarium (III) luminescence in a two-dimensional coordination polymer

    SciTech Connect

    Knope, Karah E.; de Lill, Daniel T.; Rowland, Clare E.; Cantos, Paula M.; de Bettencourt-Dias, Ana; Cahill, Christopher L.

    2012-01-02

    Heterometallic carboxyphosphonates UO₂2+/Ln3+ have been prepared from the hydrothermal reaction of uranyl nitrate, lanthanide nitrate (Ln = Sm, Tb, Er, Yb), and phosphonoacetic acid (H₃PPA). Compound 1, (UO₂)₂(PPA)(HPPA)₂Sm(H₂O)·2H₂O (1) adopts a two-dimensional structure in which the UO₂2+ metal ions bind exclusively to the phosphonate moiety, whereas the Ln3+ ions are coordinated by both phosphonate and carboxylate functionalities. Luminescence studies of 1 show very bright visible and near-IR samarium(III)-centered emission upon direct excitation of the uranyl moiety. The Sm3+ emissive state exhibits a double-exponential decay with lifetimes of 67.2 ± 6.5 and 9.0 ± 1.3 μs as measured at 594 nm, after excitation at both 365 and 420 nm. No emission is observed in the region typical of the uranyl cation, indicating that all energy is either transferred to the Sm3+ center or lost to nonradiative processes. Herein we report the synthesis, crystal structure, and luminescent behavior of 1, as well as those of the isostructural terbium, erbium, and ytterbium analogues.

  5. Thermal stability of uranyl complexes with neutral oxygen-containing organic bases

    SciTech Connect

    Kobets, L.V.

    1987-03-01

    The thermal stability of uranyl chloride, nitrate, and oxalate with a series of neutral oxygen-containing organic ligands is discussed. It was found that the temperatures of removal of chlorine are higher than the stripping of the first molecule of the base in complexes UO/sub 2/Cl/sub 2/ x 2L. This is an indication of greater strength of the bonds of the Cl/sup -/ ions to the uranyl group in comparison with the investigated bases. It was shown that the temperatures of removal of a mole of neutral ligands depend little on the nature of the anions and exhibit a correlation with the donor capacity of the bases: Ac < TBP < DMFA similarly ordered DMSO < TBPO similarly ordered PyO. The chemistry of the decomposition of the complexes and the strength of the binding of the acido- and neutral ligands in them are discussed.

  6. Molecular Dynamics Simulations of Uranyl and Uranyl Carbonate Adsorption at Alumino-silicate Surfaces

    SciTech Connect

    Kerisit, Sebastien N.; Liu, Chongxuan

    2014-03-03

    Adsorption at mineral surfaces is a critical factor controlling the mobility of uranium(VI) in aqueous environments. Therefore, molecular dynamics (MD) simulations were performed to investigate uranyl(VI) adsorption onto two neutral alumino-silicate surfaces, namely the orthoclase (001) surface and the octahedral aluminum sheet of the kaolinite (001) surface. Although uranyl preferentially adsorbed as a bi-dentate innersphere complex on both surfaces, the free energy of adsorption at the orthoclase surface (-15 kcal mol-1) was significantly more favorable than that at the kaolinite surface (-3 kcal mol-1), which was attributed to differences in surface functional groups and to the ability of the orthoclase surface to dissolve a surface potassium ion upon uranyl adsorption. The structures of the adsorbed complexes compared favorably with X-ray absorption spectroscopy results. Simulations of the adsorption of uranyl complexes with up to three carbonate ligands revealed that uranyl complexes coordinated to up to 2 carbonate ions are stable on the orthoclase surface whereas uranyl carbonate surface complexes are unfavored at the kaolinite surface. Combining the MD-derived equilibrium adsorption constants for orthoclase with aqueous equilibrium constants for uranyl carbonate species indicates the presence of adsorbed uranium complexes with one or two carbonates in alkaline conditions, in support of current uranium(VI) surface complexation models.

  7. Engineering a uranyl specific binding protein from NikR.

    SciTech Connect

    Wegner, S. V.; Boyaci, H.; Chen, H.; Jensen, M. P.; He, C.

    2009-03-16

    The first uranyl-selective DNA-binding protein is designed using the E. coli nickel(II)-responsive protein NikR as the template. The resulting NikR? protein binds uranyl (see picture) with a dissociation constant Kd=53?nM and selectively binds to DNA in the presence of uranyl.

  8. Mechanisms of lipid malabsorption in Cystic Fibrosis: the impact of essential fatty acids deficiency

    PubMed Central

    Peretti, N; Marcil, V; Drouin, E; Levy, E

    2005-01-01

    Transport mechanisms, whereby alimentary lipids are digested and packaged into small emulsion particles that enter intestinal cells to be translocated to the plasma in the form of chylomicrons, are impaired in cystic fibrosis. The purpose of this paper is to focus on defects that are related to intraluminal and intracellular events in this life-limiting genetic disorder. Specific evidence is presented to highlight the relationship between fat malabsorption and essential fatty acid deficiency commonly found in patients with cystic fibrosis that are often related to the genotype. Given the interdependency of pulmonary disease, pancreatic insufficiency and nutritional status, greater attention should be paid to the optimal correction of fat malabsorption and essential fatty acid deficiency in order to improve the quality of life and extend the life span of patients with cystic fibrosis. PMID:15869703

  9. Essential fatty acid deficiency while a patient receiving fat regimen total parenteral nutrition

    PubMed Central

    Roongpisuthipong, Wanjarus; Phanachet, Pariya; Roongpisuthipong, Chulaporn; Rajatanavin, Natta

    2012-01-01

    A 32-year-old man was diagnosed with lymphoma and underwent Billroth’s II operation because of upper gastrointestinal haemorrhage. Although the patient received fat regimen total parenteral nutrition (TPN), the patient developed typical skin rash of essential fatty acid deficiency after 2 weeks of starting TPN. The diagnosis was confirmed by biochemical and histological analyses. After increasing the lipid infusion, the rash was gradually improved with complete resolution after 19 days. PMID:22707694

  10. Uranyl Sequestration: Synthesis and Structural Characterization of Uranyl Complexes with a Tetradentate Methylterephthalamide Ligand

    SciTech Connect

    Ni, Chengbao; Shuh, David; Raymond, Kenneth

    2011-03-07

    Uranyl complexes of a bis(methylterephthalamide) ligand (LH{sub 4}) have been synthesized and characterized by X-ray crystallography. The structure is an unexpected [Me{sub 4}N]{sub 8}[L(UO{sub 2})]{sub 4} tetramer, formed via coordination of the two MeTAM units of L to two uranyl moieties. Addition of KOH to the tetramer gave the corresponding monomeric uranyl methoxide species [Me{sub 4}N]K{sub 2}[LUO{sub 2}(OMe)].

  11. DOCOSAHEXAENOIC ACID AND ARACHIDONIC ACID PREVENT ESSENTIAL FATTY ACID DEFICIENCY AND HEPATIC STEATOSIS

    PubMed Central

    Le, Hau D.; Meisel, Jonathan A.; de Meijer, Vincent E.; Fallon, Erica M.; Gura, Kathleen M.; Nose, Vania; Bistrian, Bruce R.; Puder, Mark

    2012-01-01

    Objectives Essential fatty acids are important for growth, development, and physiologic function. Alpha-linolenic acid and linoleic acid are the precursors of docosahexaenoic and arachidonic acid, respectively, and have traditionally been considered the essential fatty acids. However, we hypothesized that docosahexaenoic acid and arachidonic acid can function as the essential fatty acids. Methods Using a murine model of essential fatty acid deficiency and consequent hepatic steatosis, we provided mice with varying amounts of docosahexaenoic and arachidonic acids to determine whether exclusive supplementation of docosahexaenoic and arachidonic acids could prevent essential fatty acid deficiency and inhibit or attenuate hepatic steatosis. Results Mice supplemented with docosahexaenoic and arachidonic acids at 2.1% or 4.2% of their calories for 19 days had normal liver histology and no biochemical evidence of essential fatty acid deficiency, which persisted when observed after 9 weeks. Conclusion Supplementation of sufficient amounts of docosahexaenoic and arachidonic acids alone without alpha-linolenic and linoleic acids meets essential fatty acid requirements and prevents hepatic steatosis in a murine model. PMID:22038210

  12. Uranyl peroxide closed clusters containing topological squares

    SciTech Connect

    Unruh, Daniel K.; Burtner, Alicia; Pressprich, Laura; Sigmon, Ginger E.; Burns, Peter C

    2010-01-01

    Four self-assembling clusters of uranyl peroxide polyhedra have been formed in alkaline aqueous solutions and structurally characterized. These clusters consist of 28, 30, 36 and 44 uranyl polyhedra and exhibit complex new topologies. Each has a structure that contains topological squares, pentagons and hexagons. Analysis of possible topologies within boundary constraints indicates a tendency for adoption of higher symmetry topologies in these cases. Small angle X-ray scattering data demonstrated that crystals of one of these clusters can be dissolved in ultrapure water and that the clusters remain intact for at least several days.

  13. New Structural Arrangements in Three Ca Uranyl Carbonate Compounds with Multiple Anionic Species

    NASA Astrophysics Data System (ADS)

    Li, Yaping; Burns, Peter C.

    2002-06-01

    Three new Ca uranyl carbonates containing nitrate or chlorine have been synthesized by room temperature evaporation of solutions. The structures of each were determined and refined on the basis of F2 for all unique data collected using an APEX CCD-based detector and MoKα radiation. The structures of each contain uranyl tricarbonate clusters of composition [UO2(CO3)3]4- that involve a uranyl hexagonal bipyramid that shares three equatorial edges with CO3 groups. The structure of Ca5[(UO2)(CO3)3]2(NO3)2(H2O)10 (UND-1) consists of a sheet of uranyl tricarbonate clusters that share edges and vertices with Caφn polyhedra (Ca:U=5:2 in the sheet). An (NO3)- group is attached to the sheet by sharing an edge with a Caφn polyhedron. Adjacent sheets are linked by H bonding only. The structure of Ca6[(UO2)(CO3)3]2Cl4(H2O)19 (UND-2) has a sheet of uranyl tricarbonate clusters and Caφn polyhedra that is similar to that found in UND-1, but adjacent sheets are linked by bonds to Ca cations and Cl anions located between the sheets. The structure of Ca12[(UO2)(CO3)3]4Cl8(H2O)47 (UND-3) involves uranyl tricarbonate clusters that share vertices and edges with clusters containing six-member rings of Caφ8 polyhedra, resulting in a heteropolyhedral framework, with Cl anions and H2O groups located in channels through the framework. Crystallographic data: UND-1, R1=0.0467, wR2=0.1022, monoclinic, space group P21/n, a=6.5729(9), b=16.517(2), c=15.195(2) Å, β=90.494(3)°, Z=2; UND-2, R1=0.0362, wR2=0.1115, tetragonal, space group P4/mbm, a=16.744(2), c=8.136(1) Å, Z=2; UND-3, R1=0.0367, wR2=0.1110, cubic, space group Fdoverline3, a=27.489(3) Å, Z=8.

  14. Syntheses and structures of uranyl ethylenediphosphonates: from layers to elliptical nanochannels.

    PubMed

    Tian, Tao; Yang, Weiting; Wang, Hao; Dang, Song; Pan, Qing-Jiang; Sun, Zhong-Ming

    2013-06-17

    A family of uranium diphosphonates have been hydrothermally synthesized through the reaction of ethylenediphosphonic acid (EDP, H4L) and uranyl nitrate/zinc uranyl acetate in the presence of organic templates, such as tetraethyl ammonium (NEt4(+)), 4,4'-bipyridine (bipy), and 1,10-phenanthroline (phen). The UO2(2+) in UO2(H2O)(H2L)(EDP-U1) is equatorially five-coordinated by four phosphonate groups and one aqua ligand, forming a pentagonal bipyramid. Each EDP ligand is doubly protonated and chelates three UO2(2+), resulting in a layered structure. Compounds (NEt4)2(UO2)3(HL)2(H2L)·4H2O (EDP-U2) and (H2bipy)UO2L (EDP-U3) have the same layered structure in which NEt4(+) and protonated bipy fill in the uranyl-phosphonate interlayers, respectively, and play a role to balance the negative charges. Different from that in EDP-U1, the UO2(2+) exists in the form of a UO6 tetragonal bipyramid and is surrounded by four different EDP ligands in EDP-U2 and EDP-U3. (Hphen)2(UO2)2(H2L)3 (EDP-U4) features a three-dimensional framework structure with large elliptical channels along the c axis (1.3 × 1.1 nm(2)). Monoprotonated phen molecules fill in these channels and hold together through strong π···π interactions. All of the four compounds have been characterized by IR and photoluminescent spectroscopy. Their characteristic emissions have been attributed as transition properties of uranyl cations. The ion-exchange study indicates that [Co(en)3](3+) could partially replace the protonated phen molecules.

  15. Syntheses and structures of uranyl ethylenediphosphonates: from layers to elliptical nanochannels.

    PubMed

    Tian, Tao; Yang, Weiting; Wang, Hao; Dang, Song; Pan, Qing-Jiang; Sun, Zhong-Ming

    2013-06-17

    A family of uranium diphosphonates have been hydrothermally synthesized through the reaction of ethylenediphosphonic acid (EDP, H4L) and uranyl nitrate/zinc uranyl acetate in the presence of organic templates, such as tetraethyl ammonium (NEt4(+)), 4,4'-bipyridine (bipy), and 1,10-phenanthroline (phen). The UO2(2+) in UO2(H2O)(H2L)(EDP-U1) is equatorially five-coordinated by four phosphonate groups and one aqua ligand, forming a pentagonal bipyramid. Each EDP ligand is doubly protonated and chelates three UO2(2+), resulting in a layered structure. Compounds (NEt4)2(UO2)3(HL)2(H2L)·4H2O (EDP-U2) and (H2bipy)UO2L (EDP-U3) have the same layered structure in which NEt4(+) and protonated bipy fill in the uranyl-phosphonate interlayers, respectively, and play a role to balance the negative charges. Different from that in EDP-U1, the UO2(2+) exists in the form of a UO6 tetragonal bipyramid and is surrounded by four different EDP ligands in EDP-U2 and EDP-U3. (Hphen)2(UO2)2(H2L)3 (EDP-U4) features a three-dimensional framework structure with large elliptical channels along the c axis (1.3 × 1.1 nm(2)). Monoprotonated phen molecules fill in these channels and hold together through strong π···π interactions. All of the four compounds have been characterized by IR and photoluminescent spectroscopy. Their characteristic emissions have been attributed as transition properties of uranyl cations. The ion-exchange study indicates that [Co(en)3](3+) could partially replace the protonated phen molecules. PMID:23701415

  16. Nitrate reduction

    DOEpatents

    Dziewinski, Jacek J.; Marczak, Stanislaw

    2000-01-01

    Nitrates are reduced to nitrogen gas by contacting the nitrates with a metal to reduce the nitrates to nitrites which are then contacted with an amide to produce nitrogen and carbon dioxide or acid anions which can be released to the atmosphere. Minor amounts of metal catalysts can be useful in the reduction of the nitrates to nitrites. Metal salts which are formed can be treated electrochemically to recover the metals.

  17. Cyanex based uranyl sensitive polymeric membrane electrodes.

    PubMed

    Badr, Ibrahim H A; Zidan, W I; Akl, Z F

    2014-01-01

    Novel uranyl selective polymeric membrane electrodes were prepared using three different low-cost and commercially available Cyanex extractants namely, bis(2,4,4-trimethylpentyl) phosphinic acid [L1], bis(2,4,4-trimethylpentyl) monothiophosphinic acid [L2] and bis(2,4,4-trimethylpentyl) dithiophosphinic acid [L3]. Optimization and performance characteristics of the developed Cyanex based polymer membrane electrodes were determined. The influence of membrane composition (e.g., amount and type of ionic sites, as well as type of plasticizer) on potentiometric responses of the prepared membrane electrodes was studied. Optimized Cyanex-based membrane electrodes exhibited Nernstian responses for UO₂(2+) ion over wide concentration ranges with fast response times. The optimized membrane electrodes based on L1, L2 and L3 exhibited Nernstian responses towards uranyl ion with slopes of 29.4, 28.0 and 29.3 mV decade(-1), respectively. The optimized membrane electrodes based on L1-L3 showed detection limits of 8.3 × 10(-5), 3.0 × 10(-5) and 3.3 × 10(-6) mol L(-1), respectively. The selectivity studies showed that the optimized membrane electrodes exhibited high selectivity towards UO₂(2+) ion over large number of other cations. Membrane electrodes based on L3 exhibited superior potentiometric response characteristics compared to those based on L1 and L2 (e.g., widest linear range and lowest detection limit). The analytical utility of uranyl membrane electrodes formulated with Cyanex extractant L3 was demonstrated by the analysis of uranyl ion in different real samples for nuclear safeguards verification purposes. The results obtained using direct potentiometry and flow-injection methods were compared with those measured using the standard UV-visible and inductively coupled plasma spectroscopic methods. PMID:24274282

  18. Cyanex based uranyl sensitive polymeric membrane electrodes.

    PubMed

    Badr, Ibrahim H A; Zidan, W I; Akl, Z F

    2014-01-01

    Novel uranyl selective polymeric membrane electrodes were prepared using three different low-cost and commercially available Cyanex extractants namely, bis(2,4,4-trimethylpentyl) phosphinic acid [L1], bis(2,4,4-trimethylpentyl) monothiophosphinic acid [L2] and bis(2,4,4-trimethylpentyl) dithiophosphinic acid [L3]. Optimization and performance characteristics of the developed Cyanex based polymer membrane electrodes were determined. The influence of membrane composition (e.g., amount and type of ionic sites, as well as type of plasticizer) on potentiometric responses of the prepared membrane electrodes was studied. Optimized Cyanex-based membrane electrodes exhibited Nernstian responses for UO₂(2+) ion over wide concentration ranges with fast response times. The optimized membrane electrodes based on L1, L2 and L3 exhibited Nernstian responses towards uranyl ion with slopes of 29.4, 28.0 and 29.3 mV decade(-1), respectively. The optimized membrane electrodes based on L1-L3 showed detection limits of 8.3 × 10(-5), 3.0 × 10(-5) and 3.3 × 10(-6) mol L(-1), respectively. The selectivity studies showed that the optimized membrane electrodes exhibited high selectivity towards UO₂(2+) ion over large number of other cations. Membrane electrodes based on L3 exhibited superior potentiometric response characteristics compared to those based on L1 and L2 (e.g., widest linear range and lowest detection limit). The analytical utility of uranyl membrane electrodes formulated with Cyanex extractant L3 was demonstrated by the analysis of uranyl ion in different real samples for nuclear safeguards verification purposes. The results obtained using direct potentiometry and flow-injection methods were compared with those measured using the standard UV-visible and inductively coupled plasma spectroscopic methods.

  19. Nitrate and periplasmic nitrate reductases

    PubMed Central

    Sparacino-Watkins, Courtney; Stolz, John F.; Basu, Partha

    2014-01-01

    The nitrate anion is a simple, abundant and relatively stable species, yet plays a significant role in global cycling of nitrogen, global climate change, and human health. Although it has been known for quite some time that nitrate is an important species environmentally, recent studies have identified potential medical applications. In this respect the nitrate anion remains an enigmatic species that promises to offer exciting science in years to come. Many bacteria readily reduce nitrate to nitrite via nitrate reductases. Classified into three distinct types – periplasmic nitrate reductase (Nap), respiratory nitrate reductase (Nar) and assimilatory nitrate reductase (Nas), they are defined by their cellular location, operon organization and active site structure. Of these, Nap proteins are the focus of this review. Despite similarities in the catalytic and spectroscopic properties Nap from different Proteobacteria are phylogenetically distinct. This review has two major sections: in the first section, nitrate in the nitrogen cycle and human health, taxonomy of nitrate reductases, assimilatory and dissimilatory nitrate reduction, cellular locations of nitrate reductases, structural and redox chemistry are discussed. The second section focuses on the features of periplasmic nitrate reductase where the catalytic subunit of the Nap and its kinetic properties, auxiliary Nap proteins, operon structure and phylogenetic relationships are discussed. PMID:24141308

  20. Adaptational modification of serine and threonine metabolism in the liver to essential amino acid deficiency in rats.

    PubMed

    Nagao, Kenji; Bannai, Makoto; Seki, Shinobu; Mori, Masato; Takahashi, Michio

    2009-03-01

    It is known that plasma serine and threonine concentrations are elevated in rats chronically fed an essential amino acid deficient diet, but the underlying mechanisms including related gene expressions or serine and threonine concentrations in liver remained to be elucidated. We fed rats lysine or valine deficient diet for 4 weeks and examined the mRNA expressions of serine synthesising (3-phosphoglycerate dehydrogenase, PHGDH) and serine/threonine degrading enzymes (serine dehydratase, SDS) in the liver. Dietary deficiency induced marked elevation of hepatic serine and threonine levels associated with enhancement of PHGDH mRNA expression and repression of SDS mRNA expression. Increases in plasma serine and threonine levels due to essential amino acid deficiency in diet were caused by marked increases in hepatic serine and threonine levels. Proteolytic responses to the amino acid deficiency may be lessened by storing amino radicals as serine and inducing anorexia through elevation of threonine. PMID:18584286

  1. A Study of the Prevalence of Serum Vitamin B12 and Folic Acid Deficiency in Western Maharashtra

    PubMed Central

    Mahajan, Sanket K.; Aundhakar, Swati C.

    2015-01-01

    Context: This study summarizes the prevalence of vitamin B12 and folic acid deficiency in the population coming to tertiary care center in Western Maharashtra along with the main presenting symptom routinely misinterpreted in daily practice. Aims and Objectives: 1. To study the prevalence of vitamin B12 and folic acid deficiency in the population of western Maharashtra. 2. To correlate the symptoms with serum vitamin B12 and folic acid levels. Materials and Methods: The present study is a cross-sectional observation study carried out on patients from western Maharashtra seeking medical attention on outpatient and inpatient basis in the medicine department of a teaching institute in Karad. One-hundred patients were selected on basis of below mentioned symptoms viz. tingling and numbness in extremities, dizziness, unsteady gait, early tiredness, forgetfulness, proximal weakness, distal weakness, chronic headache, less interest in work, chronic loose stools, strict vegetarians, alcoholics, intake of medications like anti-tubercular treatment, surgery involving terminal ileum. Serum vitamin B12 and folic acid levels of these patients were observed. Deficiency of vitamin B12 and folic acid was studied in 4 groups: (a) Absolute vitamin B12 deficiency; (b) Absolute folic acid deficiency; (c) Borderline vitamin B12 deficiency; (d) Combined vitamin B12 and folic acid deficiency. Results: Of the 100 cases, 33% patients were vegetarian. Folic acid deficiency formed the major chunk of deficiency group. Six percent patients had neuropsychiatric manifestations. Depressive illness in 1% patients, dementia in 0% patients, forgetfulness in 1% patients, mania/hallucination in 0% patients each, and chronic headache in 1% patients. Neuropathy in form of loss of reflexes, decreased touch sensation was present in 9% patients. Posterior column involvement viz. Loss of joint position, vibration, positive Romberg's sign were present in 34% patients of vitamin B12 and folic acid deficiency

  2. Specific capture of uranyl protein targets by metal affinity chromatography.

    PubMed

    Basset, Christian; Dedieu, Alain; Guérin, Philippe; Quéméneur, Eric; Meyer, Daniel; Vidaud, Claude

    2008-03-28

    To improve general understanding of biochemical mechanisms in the field of uranium toxicology, the identification of protein targets needs to be intensified. Immobilized metal affinity chromatography (IMAC) has been widely developed as a powerful tool for capturing metal binding proteins from biological extracts. However uranyl cations (UO2(2+)) have particular physico-chemical characteristics which prevent them from being immobilized on classical metal chelating supports. We report here on the first development of an immobilized uranyl affinity chromatography method, based on the cation-exchange properties of aminophosphonate groups for uranyl binding. The cation distribution coefficient and loading capacity on the support were determined. Then the stability of the uranyl-bonded phase under our chromatographic conditions was optimized to promote affinity mechanisms. The successful enrichment of uranyl binding proteins from human serum was then proven using proteomic and mass spectral analysis. PMID:18308325

  3. Pro-oxidative, genotoxic and cytotoxic properties of uranyl ions.

    PubMed

    Garmash, S A; Smirnova, V S; Karp, O E; Usacheva, A M; Berezhnov, A V; Ivanov, V E; Chernikov, A V; Bruskov, V I; Gudkov, S V

    2014-01-01

    It is demonstrated that hydroxyl radicals and hydrogen peroxide are formed under the action of uranyl ions in aqueous solutions containing no reducing agents. In the presence of uranyl ions, formation of 8-oxoguanine in DNA and long-lived protein radicals are observed in vitro. It is shown that the pro-oxidant properties of uranyl at micromolar concentrations mostly result from the physico-chemical nature of the compound rather than its radioactive decay. Uranyl ions lead to damage in DNA and proteins causing death of HEp-2 cells by necrotic pathway. It is revealed that the uranyl ions enhance radiation-induced oxidative stress and significantly increase a death rate of mice exposed to sublethal doses of X-rays.

  4. Structure-Property Relationships in Lithium, Silver, and Cesium Uranyl Borates

    SciTech Connect

    Wang, Shuao; Alekseev, Evgeny V.; Stritzinger, Jared T.; Liu, Guokui; Depmeier, Wulf; Albrecht-Schmitt, Thomas E.

    2010-11-09

    Four new uranyl borates, Li[UO{sub 2}B{sub 5}O{sub 9}]·H{sub 2}O (LiUBO-1), Ag[(UO{sub 2})B{sub 5}O{sub 8}(OH){sub 2}] (AgUBO-1), α-Cs[(UO{sub 2}){sub 2}B{sub 11}O{sub 16}(OH){sub 6}] (CsUBO-1), and β-Cs[(UO{sub 2}){sub 2}B{sub 11}O{sub 16}(OH){sub 6}] (CsUBO-2) were synthesized via the reaction of uranyl nitrate with a large excess of molten boric acid in the presence of lithium, silver, or cesium nitrate. These compounds share a common structural motif consisting of a linear uranyl, UO{sub 2}{sup 2+}, cation surrounded by BO{sub 3} triangles and BO{sub 4} tetrahedra to create an UO{sub 8} hexagonal bipyramidal environment around uranium. The borate anions bridge between uranyl units to create sheets. Additional BO{sub 3} triangles extend from the polyborate layers, and are directed approximately perpendicular to the sheets. In Li[(UO{sub 2})B{sub 5}O{sub 9}]·H{sub 2}O, the additional BO{sub 3} triangles connect these sheets together to form a three-dimensional framework structure. Li[UO{sub 2})B{sub 5}O{sub 9}]·H{sub 2}O and β-Cs[(UO{sub 2}){sub 2}B{sub 11}O{sub 16}(OH){sub 6}] adopt noncentrosymmetric structures, while Ag[(UO{sub 2})B{sub 5}O{sub 8}(OH){sub 2}] and α-Cs[(UO{sub 2}){sub 2}B{sub 11}O{sub 16}(OH){sub 6}] are centrosymmetric. Li[(UO{sub 2})B{sub 5}O{sub 9}]·H{sub 2}O, which can be obtained as pure phase, displays second-harmonic generation of 532 nm light from 1064 nm light. Topological relationships of all actinyl borates are developed.

  5. 2,6-Diiminopiperidin-1-ol: an overlooked motif relevant to uranyl and transition metal binding on poly(amidoxime) adsorbents.

    PubMed

    Kennedy, Zachary C; Cardenas, Allan Jay P; Corbey, Jordan F; Warner, Marvin G

    2016-07-01

    Glutardiamidoxime, a structural motif on sorbents used in uranium extraction from seawater, was discovered to cyclize in situ at room temperature to 2,6-diimino-piperidin-1-ol in the presence of uranyl nitrate. The new diimino motif was also generated when exposed to competing transition metals Cu(ii) and Ni(ii). Multinuclear μ-O bridged U(vi), Cu(ii), and Ni(ii) complexes featuring bound diimino ligands were isolated. PMID:27292161

  6. Charge transfer vibronic transitions in uranyl tetrachloride compounds;

    SciTech Connect

    Liu, G. K.; Deifel, N. P.; Cahill, C. L.

    2012-01-01

    The electronic and vibronic interactions of uranyl (UO{sub 2}){sup 2+} in three tetrachloride crystals have been investigated with spectroscopic experiments and theoretical modeling. Analysis and simulation of the absorption and photoluminescence spectra have resulted in a quantitative understanding of the charge transfer vibronic transitions of uranyl in the crystals. The spectra obtained at liquid helium temperature consist of extremely narrow zero-phonon lines (ZPL) and vibronic bands. The observed ZPLs are assigned to the first group of the excited states formed by electronic excitation from the 3{sigma} ground state into the f{sub {delta}{phi}}, orbitals of uranyl. The Huang-Rhys theory of vibronic coupling is modified successfully for simulating both the absorption and luminescence spectra. It is shown that only vibronic coupling to the axially symmetric stretching mode is Franck-Condon allowed, whereas other modes are involved through coupling with the symmetric stretching mode. The energies of electronic transitions, vibration frequencies of various local modes, and changes in the O=U=O bond length of uranyl in different electronic states and in different coordination geometries are evaluated in empirical simulations of the optical spectra. Multiple uranyl sites derived from the resolution of a superlattice at low temperature are resolved by crystallographic characterization and time- and energy-resolved spectroscopic studies. The present empirical simulation provides insights into fundamental understanding of uranyl electronic interactions and is useful for quantitative characterization of uranyl coordination.

  7. Charge transfer vibronic transitions in uranyl tetrachloride compounds

    SciTech Connect

    Liu, Guokui; Deifel, Nicholas P.; Cahill, Christopher L.; Zhurov, Vladimir V.; Pinkerton, A. Alan

    2012-01-01

    The electronic and vibronic interactions of uranyl (UO₂)2+ in three tetrachloride crystals have been investigated with spectroscopic experiments and theoretical modeling. Analysis and simulation of the absorption and photoluminescence spectra have resulted in a quantitative understanding of the charge transfer vibronic transitions of uranyl in the crystals. The spectra obtained at liquid helium temperature consist of extremely narrow zero-phonon lines (ZPL) and vibronic bands. The observed ZPLs are assigned to the first group of the excited states formed by electronic excitation from the 3σ ground state into the fδ,Φ orbitals of uranyl. The Huang–Rhys theory of vibronic coupling is modified successfully for simulating both the absorption and luminescence spectra. It is shown that only vibronic coupling to the axially symmetric stretching mode is Franck–Condon allowed, whereas other modes are involved through coupling with the symmetric stretching mode. The energies of electronic transitions, vibration frequencies of various local modes, and changes in the O=U=O bond length of uranyl in different electronic states and in different coordination geometries are evaluated in empirical simulations of the optical spectra. Multiple uranyl sites derived from the resolution of a superlattice at low temperature are resolved by crystallographic characterization and time- and energy-resolved spectroscopic studies. The present empirical simulation provides insights into fundamental understanding of uranyl electronic interactions and is useful for quantitative characterization of uranyl coordination.

  8. Nutritional stress effects under different nitrogen sources on the genes in microalga Isochrysis zhangjiangensis and the assistance of Alteromonas macleodii in releasing the stress of amino acid deficiency.

    PubMed

    Wu, Shuang; Zhou, Jiannan; Xin, Yanjuan; Xue, Song

    2015-10-01

    The expressions of nine nitrogen assimilation-associated genes, NRT2, NAR1, NIA2, NIR, GLN2, GLSF, GSN1, GDH, and AAT2, in the microalga Isochrysis zhangjiangensis were investigated to unveil the effects of limitations of various nitrogen sources (NaNO3 , NH4 Cl, NaNO2 , and an amino acid mixture) on the microalgae. The results demonstrated that the NRT2, NAR1, GLN2, GSN1, and AAT2 genes were highly expressed in lipid-rich microalgae under inorganic nitrogen-deficient conditions and they decreased after nitrogen resupply. Significant increases in the expressions of NAR1, GLN2, and GLSF were found in nitrate-depleted microalgae, whereas significant increases in the expressions of NRT2, NAR1, GLN2, and GSN1 were found in nitrite-depleted microalgae. Significant increases in the expressions of only NRT2 and GSN1 were found in ammonium-depleted microalgae (P < 0.05). Except for the NRT2, other genes were expressed at lower levels under amino acid-deficient conditions compared with amino acid-sufficient controls. The expression of the NIA2 gene decreased in nitrogen-depleted microalgae regardless of the initial nitrogen source. However, the results of fatty acid analyses showed that the features of fatty acid profiles followed a similar mode, in which the percentage compositions of C16:0 and C18:1Δ(9) increased in nitrogen-depleted cells and that of C16:1Δ(9) , C18:3Δ(9,12,15) , C18:4Δ(6,9,12,15) , and C18:5Δ(3,6,9,12,15) decreased, regardless of the type of nitrogen source applied. It was also found that the epiphytic bacterium Alteromonas macleodii played a particularly important role in releasing microalgae from the stress of amino acid deficiency. These findings also provide a foundation for regulating microalgal lipid production through manipulation of the nitrogen assimilation-associated genes.

  9. METHOD OF INHIBITING CORROSION IN URANYL SULFATE SOLUTIONS

    DOEpatents

    Bohlmann, E.G.; Griess, J.C. Jr.

    1960-08-23

    A method is given for treating a uranyl sulfate solution to inhibit the corrosiveness of the solution and elevate the phase separation temperature of the solution. Lithium sulfate is added to the solution in an amount ranging from 0.25 to 1.3 times the uranyl sulfate concentration. The corrosiveness of the solution with respect to stainless steel is substantially decreased by this means. This treatment also serves to raise the phase separation temperature of the solution (above 250 deg C), at which time the uranyl sulfate solution separates into two liquid phases of unequal uranium concentration and thus becomes unsuitable as nuclear reactor fuel.

  10. Incorporation of neptunium(VI) into a uranyl selenite.

    PubMed

    Meredith, Nathan A; Polinski, Matthew J; Lin, Jian; Simonetti, Antonio; Albrecht-Schmitt, Thomas E

    2012-10-15

    The incorporation of neptunium(VI) into the layered uranyl selenite Cs[(UO(2))(HSeO(3))(SeO(3))] has yielded the highest level of neptunium uptake in a uranyl compound to date with an average of 12(±3)% substitution of Np(VI) for U(VI). Furthermore, this is the first case in nearly 2 decades of dedicated incorporation studies in which the oxidation state of neptunium has been determined spectroscopically in a doped uranyl compound and also the first time in which neptunium incorporation has resulted in a structural transformation.

  11. Effect of folic acid deficiency on pregnant rats and their offspring.

    PubMed

    Tagbo, I F; Hill, D C

    1977-06-01

    Two groups of 63-day-old female Wistar rats were fed a folic acid deficient diet, based on 20% of vitamin-free casein and containing 1% of succinylsulfathiazole, for 5 weeks (group A) and 9 weeks (group B) before being bred, and the same diet was continued through pregnancy and lactation. Three out of eleven (21.3%) and three out of seven (42.9%) rats in groups A and B, respectively, resorbed completely, while no control rat resorbed. No pups from group B survived to weaning. Both groups (A and B) showed depressed feed consumption (although the effect in group A rats was small) and weight gains and increased formiminoglutamic acid excretion in the urine during gestation, and low serum folic acid by the end of lactation. A study of blood components in group A rats revealed leucopenia, granulocytopenia, and increased reticulocyte count. While no congenital deformities were observed in pups from deficient dams, group A and group B dams in contrast to controls produced smaller sized litters with lower birth weights and poor survival rate. Surviving pups from group A dams had decreased weaning weights with significantly lower brain weights and brain DNA per gram of tissue. PMID:884600

  12. Long-chain omega-3 fatty acid deficiency in mood disorders: rationale for treatment and prevention.

    PubMed

    McNamara, Robert K

    2013-09-01

    Major recurrent mood disorders including major depressive disorder (MDD) and bipolar disorder (BD) are associated with significant psychosocial morbidity and excess premature mortality primarily attributable to suicide and coronary heart disease. Limited efficacy and adverse side-effects associated with psychotropic medications used in the treatment of MDD and BD highlight the urgent need to develop safe and efficacious treatments or treatment adjuncts. A body of evidence now indicates that long-chain omega-3 (LCn-3) fatty acid deficiency is a feature associated with MDD and BD. The etiology of LCn-3 deficits in MDD and BD patients may be attributable to both genetic and environmental factors. Dietary LCn-3 supplementation is safe and well-tolerated with chronic administration and corrects LCn-3 deficiency in MDD and BD patients. LCn-3 supplementation has been found to augment the therapeutic efficacy of psychotropic medications in the treatment of mood symptoms and to reduce suicidality. Preliminary studies also suggest that LCn-3 supplementation is efficacious as monotherapy in the treatment and prevention of psychopathology in children and adolescents. LCn-3 supplementation is also associated with reduced risk for developing coronary heart disease. The overall cost-benefit ratio associated with LCn-3 supplementation provides a strong rationale to diagnose and treat LCn-3 deficiency in MDD and BD patients, and to prevent LCn-3 deficiency in subjects at high risk for developing these disorders.

  13. Effect of undernutrition and amino acid deficiency on the timing of puberty in rats.

    PubMed

    Glass, A R; Harrison, R; Swerdloff, R S

    1976-11-01

    Sexual maturation was examined in underfed or amino acid-deficient rats. We have demonstrated a highly significant negative linear relationship (r = -0.80, P less than 0.001) between the age at puberty and the growth rate in rats under conditions of food restriction. The weight at puberty in animals growing at different rates because of undernutrition was not constant but behaved as a quadratic function of growth rate, as predicted from the assumption that growth rate was an independent variable. Growth rate is therefore more important than arrival at a particular fixed weight in determining the timing of puberty. Feeding of low valine diets resulted in delayed sexual maturation. Both the weight at vaginal opening (182 +/- 5.9 g) and the weight at first estrus (187 +/- 6.1 g) were significantly greater in the valine-deficient group when compared with growth-matched control (139 +/- 10.7 g and 161 +/- 9.3 g, respectively, P less than 0.05). The valine-deficient group also had significantly later vaginal opening (98.8+/- 4.7 days) than growth-matched controls (76.6 +/- 6.6 days, P less than 0.02). Valine deficiency seemed to have a specific effect on the hypothalamic-pituitary-gonadal axis since puberty in valine-deficient animals was delayed more than could be accounted for by impairment of growth.

  14. Effect of marginal ascorbic acid deficiency on saliva level of cortisol in the guinea pig.

    PubMed

    Enwonwu, C O; Sawiris, P; Chanaud, N

    1995-08-01

    Male guinea pigs subjected to prolonged marginal ascorbic acid deficiency developed moon facies and oedema, features of functional adrenal hypercorticism. Compared with age- and sex-matched controls fed an adequate diet for a similar period, ascorbate deficiency had no effect on submandibular gland weight but elicited a significant (p < 0.005) reduction in stimulated whole-saliva flow rate. Plasma cortisol concentration (nmol/L) was significantly increased (p < 0.005) in the deficient animals (998.21 +/- 57.19 compared to 254.66 +/- 15.62 for the controls). Associated with marked hypercortisolaemia in the deficient animals was a significant (p < 0.01) but less prominent increase in the whole-saliva cortisol level, resulting in a mean saliva/plasma cortisol ratio of 46% for this group compared to 72% for the controls. Increased corticosteroid levels suppress immunological and inflammatory responses, particularly neutrophil function, impair production of some cytokines, inhibit collagen synthesis, and impair wound healing and bone matrix formation. Numerous conditions such as ageing, stress, smoking, ionizing radiation, ingestion of drugs, protein malnutrition, diabetes, and several other pathological states, which are among the risk factors for xerostomia and periodontal/oral mucosal lesions, promote tissue depletion of ascorbate. This study suggests that increased salivary and blood levels of glucocorticoids in these conditions may be important in reducing the ability of the host to mount an effective immune response to oral pathogens. PMID:7487575

  15. Evidence that folic acid deficiency is a major determinant of hyperhomocysteinemia in Parkinson's disease.

    PubMed

    dos Santos, Eliseu Felippe; Busanello, Estela Natacha Brandt; Miglioranza, Anelise; Zanatta, Angela; Barchak, Alethea Gatto; Vargas, Carmen Regla; Saute, Jonas; Rosa, Charles; Carrion, Maria Júlia; Camargo, Daiane; Dalbem, André; da Costa, Jaderson Costa; de Sousa Miguel, Sandro René Pinto; de Mello Rieder, Carlos Roberto; Wajner, Moacir

    2009-06-01

    In the present work we measured blood levels of total homocysteine ((t)Hcy), vitamin B(12) and folic acid in patients with Parkinson s disease (PD) and in age-matched controls and searched for possible associations between these levels with smoking, alcohol consumption, L-DOPA treatment and disease duration in PD patients. We initially observed that plasma (t)Hcy levels were increased by around 30 % in patients affected by PD compared to controls. Linear correlation, multiple regression and comparative analyses revealed that the major determinant of the increased plasma concentrations of (t)Hcy in PD patients was folic acid deficiency, whereas in controls (t)Hcy levels were mainly determined by plasma vitamin B(12) concentrations. We also observed that alcohol consumption, gender and L-DOPA treatment did not significantly alter plasma (t)Hcy, folic acid and vitamin B(12) levels in parkinsonians. Furthermore, disease duration was positively associated with (t)Hcy levels and smoking was linked with a deficit of folic acid in PD patients. Considering the potential synergistic deleterious effects of Hcy increase and folate deficiency on the central nervous system, we postulate that folic acid should be supplemented to patients affected by PD in order to normalize blood Hcy and folate levels, therefore potentially avoiding these risk factors for neurologic deterioration in this disorder.

  16. Thermodynamic properties of autunite, uranyl hydrogen phosphate, and uranyl orthophosphate from solubility and calorimetric measurements

    SciTech Connect

    Gorman-Lewis, Drew; Shareva, Tatiana; kubatko, Karrie-Ann; burns, Peter; Wellman, Dawn M.; McNamara, Bruce K.; szymanowski, jennifer; Navrotsky, Alexandra; Fein, Jeremy B.

    2009-10-01

    In this study, we use solubility and oxide melt solution calorimetry measurements to determine the thermodynamic properties of the uranyl phosphate phases autunite (abbreviated: CaUP), uranyl hydrogen phosphate (HUP), and uranyl orthophosphate (UP). Solubility measurements from both supersaturated and undersaturated conditions, as well as under different pH conditions, rigorously demonstrate attainment of equilibrium and yield well-constrained solubility product values of -48.36 (-0.03 /+ 0.03), -13.17 (-0.11 / +0.07), and -49.36 (-0.04 / +0.02) for CaUP, HUP, and UP, respectively. We use the solubility data to calculate standard state Gibbs free energies of formation for all phases (-7630.61 ± 9.69, -3072.27 ± 4.76, and -6138.95 ± 12.24 kJ mol-1 for CaUP, HUP, and UP, respectively), and calorimetry data to calculate standard state enthalpies of formation of -3223.22 ± 4.00 and -7001.01 ± 15.10 kJ mol-1 for HUP and UP, respectively. Combining these results allows us also to calculate the standard state entropies of formation of -506.54 ± 10.48 and -2893.12 ± 19.44 kJ mol-1 K-1 for HUP and UP phases, respectively. The results from this study are part of a combined effort to develop reliable and internally consistent thermodynamic data for environmentally relevant uranyl minerals. Data such as these are required in order to optimize and quantitatively assess the effect of phosphate amendment remediation technologies for uranium contaminated systems.

  17. Gas Phase Uranyl Activation: Formation of a Uranium Nitrosyl Complex from Uranyl Azide

    SciTech Connect

    Gong, Yu; De Jong, Wibe A.; Gibson, John K.

    2015-05-13

    Activation of the oxo bond of uranyl, UO22+, was achieved by collision induced dissociation (CID) of UO2(N3)Cl2– in a quadrupole ion trap mass spectrometer. The gas phase complex UO2(N3)Cl2– was produced by electrospray ionization of solutions of UO2Cl2 and NaN3. CID of UO2(N3)Cl2– resulted in the loss of N2 to form UO(NO)Cl2–, in which the “inert” uranyl oxo bond has been activated. Formation of UO2Cl2– via N3 loss was also observed. Density functional theory computations predict that the UO(NO)Cl2– complex has nonplanar Cs symmetry and a singlet ground state. Analysis of the bonding of the UO(NO)Cl2– complex shows that the side-on bonded NO moiety can be considered as NO3–, suggesting a formal oxidation state of U(VI). Activation of the uranyl oxo bond in UO2(N3)Cl2– to form UO(NO)Cl2– and N2 was computed to be endothermic by 169 kJ/mol, which is energetically more favorable than formation of NUOCl2– and UO2Cl2–. The observation of UO2Cl2– during CID is most likely due to the absence of an energy barrier for neutral ligand loss.

  18. Uranyl phthalocyanines show promise in the treatment of brain tumors

    NASA Technical Reports Server (NTRS)

    Frigerio, N. A.

    1967-01-01

    Processes synthesize sulfonated and nonsulfonated uranyl phthalocyanines for application in neutron therapy of brain tumors. Tests indicate that the compounds are advantageous over the previously used boron and lithium compounds.

  19. Dynamic interplay between uranyl phosphate precipitation, sorption, and phase evolution

    SciTech Connect

    Munasinghe, P. Sumudu; Elwood Madden, Megan E.; Brooks, Scott C.; Elwood Madden, Andrew S.

    2015-04-17

    We report that natural examples demonstrate uranyl-phosphate minerals can maintain extremely low levels of aqueous uranium in groundwaters due to their low solubility. Thus, greater understanding of the geochemical factors leading to uranyl phosphate precipitation may lead to successful application of phosphate-based remediation methods. However, the solubility of uranyl phosphate phases varies over >3 orders of magnitude, with the most soluble phases typically observed in lab experiments. To understand the role of common soil/sediment mineral surfaces in the nucleation and transformation of uranyl phosphate minerals under environmentally relevant conditions, we carried out batch experiments with goethite and mica at pH 6 in mixed electrolyte solutions ranging from 1–800 μM U and 1–800 μM P. All experiments ended with uranium concentrations below the USEPA MCL for U, but with 2–3 orders of magnitude difference in uranium concentrations.

  20. Dynamic interplay between uranyl phosphate precipitation, sorption, and phase evolution

    DOE PAGES

    Munasinghe, P. Sumudu; Elwood Madden, Megan E.; Brooks, Scott C.; Elwood Madden, Andrew S.

    2015-04-17

    We report that natural examples demonstrate uranyl-phosphate minerals can maintain extremely low levels of aqueous uranium in groundwaters due to their low solubility. Thus, greater understanding of the geochemical factors leading to uranyl phosphate precipitation may lead to successful application of phosphate-based remediation methods. However, the solubility of uranyl phosphate phases varies over >3 orders of magnitude, with the most soluble phases typically observed in lab experiments. To understand the role of common soil/sediment mineral surfaces in the nucleation and transformation of uranyl phosphate minerals under environmentally relevant conditions, we carried out batch experiments with goethite and mica at pHmore » 6 in mixed electrolyte solutions ranging from 1–800 μM U and 1–800 μM P. All experiments ended with uranium concentrations below the USEPA MCL for U, but with 2–3 orders of magnitude difference in uranium concentrations.« less

  1. COGEMA Experience in Uranous Nitrate Preparation

    SciTech Connect

    Tison, E.; Bretault, Ph.

    2006-07-01

    Separation and purification of plutonium by PUREX process is based on a sequence of extraction and back extraction which requires reducing plutonium Pu IV (extractable form) into Pu III (inextractable form) Different reducers can be used to reduce Pu IV into Pu III. Early plants such as that for Magnox fuel at Sellafield used ferrous sulfamate while UP 1 at Marcoule used uranous sulfamate. These reducers are efficient and easy to prepare but generates ferric and/or sulphate ions and so complicates management of the wastes from the plutonium purification cycle. Recent plants such as UP3 and UP2 800 at La Hague, THORP at Sellafield, and RRP at Rokkasho Mura (currently under tests) use uranous nitrate (U IV) stabilized by hydrazinium nitrate (N{sub 2}H{sub 5}NO{sub 3}) and hydroxyl ammonium nitrate (HAN). In the French plants, uranous nitrate is used in U-Pu separation and alpha barrier and HAN is used in Pu purification. Compared to sulfamate, U IV does not generate extraneous chemical species and uranyl nitrate (U VI) generated by reducing Pu IV follows the main uranium stream. More over uranous nitrate is prepared from reprocessed purified uranyl nitrate taken at the outlet of the reprocessing plant. Hydrazine and HAN offer the advantage to be salt-free reagents. Uranous nitrate can be generated either by electrolysis or by catalytic hydrogenation process. Electrolytic process has been implemented in early plant UP 1 at Marcoule (when changing reducer from uranous sulfamate to uranous nitrate) and was used again in UP2 plant at La Hague. However, the electrolytic process presented several disadvantages such as a low conversion rate and problems associated with the use of mercury. Electrolysis cells with no mercury were developed for the Eurochemic plant in Belgium and then implemented in the first Japanese reprocessing plant in Tokai-Mura. But finally, in 1975, the electrolytic process was abandoned in favor of the catalytic hydrogenation process developed at La

  2. EXAFS Study of Uranyl Complexation at Pseudomonas fluorescens Cell Surfaces

    NASA Astrophysics Data System (ADS)

    Bencheikh, R.; Bargar, J. R.; Tebo, B. M.

    2002-12-01

    Little is known about the roles of microbial biomass as a sink and source for uranium in contaminated aquifers, nor of the impact of bacterial biochemistry on uranium speciation in the subsurface. A significant role is implied by the high affinities of both Gram positive and Gram negative cells for binding uranyl (UO2{ 2+}). In the present study, Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy was used to identify membrane functional groups involved in uranyl binding to the Gram negative bacterium Pseudomonas fluorescens from pH 3 to pH 8. Throughout this pH-range, EXAFS spectra can be described primarily in terms of coordination of carboxylic groups to uranyl. U-C distances characteristic of 4-, 5- and 8- membered rings were observed, as well as the possibility of phosphato groups. Both shell-by-shell fits and principle component analyses indicate that the functional groups involved in binding of uranyl to the cell surface do not vary systematically across the pH range investigated. This result contrasts with EXAFS results of uranyl sorbed to Gram positive bacteria, and suggests an important role for long-chain carboxylate-terminated membrane functional groups in binding uranyl.

  3. Detection and treatment of omega-3 fatty acid deficiency in psychiatric practice: Rationale and implementation.

    PubMed

    Messamore, Erik; McNamara, Robert K

    2016-02-10

    A body of translational evidence has implicated dietary deficiency in long-chain omega-3 (LCn-3) fatty acids, including eicosapenaenoic acid (EPA) and docosahexaenoic acid (DHA), in the pathophysiology and potentially etiology of different psychiatric disorders. Case-control studies have consistently observed low erythrocyte (red blood cell) EPA and/or DHA levels in patients with major depressive disorder, bipolar disorder, schizophrenia, and attention deficit hyperactivity disorder. Low erythrocyte EPA + DHA biostatus can be treated with fish oil-based formulations containing preformed EPA + DHA, and extant evidence suggests that fish oil supplementation is safe and well-tolerated and may have therapeutic benefits. These and other data provide a rationale for screening for and treating LCn-3 fatty acid deficiency in patients with psychiatric illness. To this end, we have implemented a pilot program that routinely measures blood fatty acid levels in psychiatric patients entering a residential inpatient clinic. To date over 130 blood samples, primarily from patients with treatment-refractory mood or anxiety disorders, have been collected and analyzed. Our initial results indicate that the majority (75 %) of patients exhibit whole blood EPA + DHA levels at ≤ 4 percent of total fatty acid composition, a rate that is significantly higher than general population norms (25 %). In a sub-set of cases, corrective treatment with fish oil-based products has resulted in improvements in psychiatric symptoms without notable side effects. In view of the urgent need for improvements in conventional treatment algorithms, these preliminary findings provide important support for expanding this approach in routine psychiatric practice.

  4. Detection and treatment of omega-3 fatty acid deficiency in psychiatric practice: Rationale and implementation.

    PubMed

    Messamore, Erik; McNamara, Robert K

    2016-01-01

    A body of translational evidence has implicated dietary deficiency in long-chain omega-3 (LCn-3) fatty acids, including eicosapenaenoic acid (EPA) and docosahexaenoic acid (DHA), in the pathophysiology and potentially etiology of different psychiatric disorders. Case-control studies have consistently observed low erythrocyte (red blood cell) EPA and/or DHA levels in patients with major depressive disorder, bipolar disorder, schizophrenia, and attention deficit hyperactivity disorder. Low erythrocyte EPA + DHA biostatus can be treated with fish oil-based formulations containing preformed EPA + DHA, and extant evidence suggests that fish oil supplementation is safe and well-tolerated and may have therapeutic benefits. These and other data provide a rationale for screening for and treating LCn-3 fatty acid deficiency in patients with psychiatric illness. To this end, we have implemented a pilot program that routinely measures blood fatty acid levels in psychiatric patients entering a residential inpatient clinic. To date over 130 blood samples, primarily from patients with treatment-refractory mood or anxiety disorders, have been collected and analyzed. Our initial results indicate that the majority (75 %) of patients exhibit whole blood EPA + DHA levels at ≤ 4 percent of total fatty acid composition, a rate that is significantly higher than general population norms (25 %). In a sub-set of cases, corrective treatment with fish oil-based products has resulted in improvements in psychiatric symptoms without notable side effects. In view of the urgent need for improvements in conventional treatment algorithms, these preliminary findings provide important support for expanding this approach in routine psychiatric practice. PMID:26860589

  5. Parenteral safflower oil emulsion (Liposyn 10%): safety and effectiveness in treating or preventing essential fatty acid deficiency in surgical patients.

    PubMed Central

    Bivins, B A; Rapp, R P; Record, K; Meng, H C; Griffen, W O

    1980-01-01

    The safety and effectiveness of a 10% safflower oil emulsion in treating or preventing essential fatty acid deficiency was tested in a prospective study of 15 surgical patients requiring total parenteral nutrition for two to four weeks. Three dosage regimens were evaluated including: Group I: 4% of calories as linoleate daily (five patients), Group II: 4% of calories as linoleate every other day (two patients), and Group III: 8% of calories every other day (eight patients). Patients were monitored for laboratory changes from baseline specifically in those areas where previous fat emulsions have caused serious deviations. No significant changes were noted in hematologic parameters, coagulation studies, cholesterol and triglyceride serum levels. Although there were sporadic mild deviations in liver function changes in several patients, no clinically significant adverse effects could be directly attributed to infusion of the fat emulsion. Three patients had baseline triene/tetraene ratios of 0.4 or greater, indicative of essential fatty/acid deficiency, and these ratios dropped to less than 0.4 within eight days of beginning therapy with the parenteral fat emulsion. The remaining 12 patients maintained a normal triene/tetraene ratio of less than 0.4 throughout the 28 day study period. All three dosage regimens were considered effective for treatment and prevention of essential fatty acid deficiency. Images Fig. 1. Fig. 2. Fig. 3. PMID:6767452

  6. Ligand sensitized luminescence of uranyl by benzoic acid in acetonitrile medium: A new luminescent uranyl benzoate specie

    NASA Astrophysics Data System (ADS)

    Kumar, Satendra; Maji, S.; Joseph, M.; Sankaran, K.

    2015-03-01

    Benzoic acid (BA) is shown to sensitize and enhance the luminescence of uranyl ion in acetonitrile medium. Luminescence spectra and especially UV-Vis spectroscopy studies reveal the formation of tri benzoate complex of uranyl i.e. [UO2(C6H5COO)3]- which is highly luminescent. In particular, three sharp bands at 431, 443, 461 nm of absorption spectra provides evidence for tri benzoate specie of uranyl in acetonitrile medium. The luminescence lifetime of uranyl in this complex is 68 μs which is much more compared to the lifetime of uncomplexed uranyl (20 μs) in acetonitrile medium. In contrary to aqueous medium where uranyl benzoate forms 1:1 and 1:2 species, spectroscopic data reveal formation of 1:3 complex in acetonitrile medium. Addition of water to acetonitrile results in decrease of luminescence intensity of this specie and the luminescence features implode at 20% (v/v) of water content. For the first time, to the best of our knowledge, the existence of [UO2(C6H5COO)3]- specie in acetonitrile is reported. Mechanism of luminescence enhancement is discussed.

  7. Surface complexation model of uranyl sorption on Georgia kaolinite

    USGS Publications Warehouse

    Payne, T.E.; Davis, J.A.; Lumpkin, G.R.; Chisari, R.; Waite, T.D.

    2004-01-01

    The adsorption of uranyl on standard Georgia kaolinites (KGa-1 and KGa-1B) was studied as a function of pH (3-10), total U (1 and 10 ??mol/l), and mass loading of clay (4 and 40 g/l). The uptake of uranyl in air-equilibrated systems increased with pH and reached a maximum in the near-neutral pH range. At higher pH values, the sorption decreased due to the presence of aqueous uranyl carbonate complexes. One kaolinite sample was examined after the uranyl uptake experiments by transmission electron microscopy (TEM), using energy dispersive X-ray spectroscopy (EDS) to determine the U content. It was found that uranium was preferentially adsorbed by Ti-rich impurity phases (predominantly anatase), which are present in the kaolinite samples. Uranyl sorption on the Georgia kaolinites was simulated with U sorption reactions on both titanol and aluminol sites, using a simple non-electrostatic surface complexation model (SCM). The relative amounts of U-binding >TiOH and >AlOH sites were estimated from the TEM/EDS results. A ternary uranyl carbonate complex on the titanol site improved the fit to the experimental data in the higher pH range. The final model contained only three optimised log K values, and was able to simulate adsorption data across a wide range of experimental conditions. The >TiOH (anatase) sites appear to play an important role in retaining U at low uranyl concentrations. As kaolinite often contains trace TiO2, its presence may need to be taken into account when modelling the results of sorption experiments with radionuclides or trace metals on kaolinite. ?? 2004 Elsevier B.V. All rights reserved.

  8. Folic acid deficiency enhances abeta accumulation in APP/PS1 mice brain and decreases amyloid-associated miRNAs expression.

    PubMed

    Liu, Huan; Tian, Tian; Qin, Shanchun; Li, Wen; Zhang, Xumei; Wang, Xuan; Gao, Yuxia; Huang, Guowei

    2015-12-01

    Recent efforts have revealed the microRNA (miRNA) pathways in the pathogenesis of Alzheimer's disease (AD). Epidemiological studies have revealed an association between folic acid deficiency and AD risk. However, the effects of folic acid deficiency on miRNA expression in AD animals have not been observed. We aimed to find if folic acid deficiency may enhance amyloid-β (Aβ) peptide deposition and regulate amyloid-associated miRNAs and their target genes expression in APP/PS1 mice. APP/PS1 mice and N2a cells were treated with folic acid-deficient diet or medium. Cognitive function of mice was assessed using the Morris water maze. miRNA profile was tested by polymerase chain reaction (PCR) array. Different expressional miRNAs were validated by real-time PCR. The deposition of Aβ plaques was evaluated by immunohistochemistry and enzyme-linked immunosorbent assay. APP and BACE1 proteins in mice brain and N2a cells were determined by Western blot. Folic acid deficiency aggravated amyloid pathology in AD mice. The AD+FD group showed shorter time spent in the target zone during the probe test. Analysis of miRNAs predicted to target these genes revealed several miRNA candidates that were differentially modulated by folic acid deficiency. In APP/PS1 mice brains and N2a cells with folic acid-deficient treatment, miR-106a-5p, miR-200b-3p and miR-339-5p were down-regulated, and their target genes APP and BACE1 were up-regulated. In conclusion, folic acid deficiency can enhance Aβ accumulation in APP/PS1 mice brain and decrease amyloid-associated miRNAs expression.

  9. Resistance of essential fatty acid-deficient rats to endotoxin-induced increases in vascular permeability

    SciTech Connect

    Li, E.J.; Cook, J.A.; Spicer, K.M.; Wise, W.C.; Rokach, J.; Halushka, P.V. )

    1990-06-01

    Resistance to endotoxin in essential fatty acid-deficient (EFAD) rats is associated with reduced synthesis of certain arachidonic acid metabolites. It was hypothesized that EFAD rats would manifest decreased vascular permeability changes during endotoxemia as a consequence of reduced arachidonic acid metabolism. To test this hypothesis, changes in hematocrit (HCT) and mesenteric localization rate of technetium-labeled human serum albumin (99mTc-HSA) and red blood cells (99mTc-RBC) were assessed in EFAD and normal rats using gamma-camera imaging. Thirty minutes after Salmonella enteritidis endotoxin, EFAD rats exhibited less hemoconcentration as determined by % HCT than normal rats. Endotoxin caused a less severe change in permeability index in the splanchnic region in EFAD rats than in normal rats (1.2 +/- 0.6 x 10(-3)min-1 vs. 4.9 +/- 1.7 x 10(-3)min-1 respectively, P less than 0.05). In contrast to 99mTc-HSA, mesenteric localization of 99mTc-RBC was not changed by endotoxin in control or EFAD rats. Supplementation with ethyl-arachidonic acid did not enhance susceptibility of EFAD rats to endotoxin-induced splanchnic permeability to 99mTc-HSA. Leukotrienes have been implicated as mediators of increased vascular permeability in endotoxin shock. Since LTC3 formation has been reported to be increased in EFA deficiency, we hypothesized that LTC3 may be less potent than LTC4. Thus the effect of LTC3 on mean arterial pressure and permeability was compared to LTC4 in normal rats. LTC3-induced increases in peak mean arterial pressure were less than LTC4 at 10 micrograms/kg (39 +/- 5 mm Hg vs. 58 +/- 4 mm Hg respectively, P less than 0.05) and at 20 micrograms/kg (56 +/- 4 mm Hg vs. 75 +/- 2 mm Hg respectively, P less than 0.05). LY171883 (30 mg/kg), an LTD4/E4 receptor antagonist, attenuated the pressor effect of LTC4, LTD4, and LTC3.

  10. Dimeric uranyl complexes with bridging perrhenates.

    PubMed

    John, Gordon H; May, Iain; Sarsfield, Mark J; Collison, David; Helliwell, Madeleine

    2007-04-28

    The reaction between [UO2(ReO4)2.H(2)O] and two equivalents of either tri-n-butyl phosphine oxide (TBPO) or tri-iso-butyl phosphate (TiBP) results in the formation of [UO2(mu2-ReO4)(ReO4)(TBPO)2]2 (1) and [UO2(mu2-ReO4)(ReO4)(TiBP)2]2 (2) respectively. Both complexes crystallise as two structurally similar centrosymmetric dimers, the cores containing two uranyl moieties linked by bridging perrhenates. Two P=O donor ligands and one monodenatate perrhenate complete the pentagonal bipyramidal coordination sphere at each metal centre. Both complexes have also been characterised in the solid state by vibrational and absorption spectroscopy. Solution spectroscopic characterisation indicates that both perrhenate and phosphine oxide (1) or phosphate (2) remain coordinated, although it is not possible to state conclusively that the dimeric species remain intact. A low resolution structural study of a minor product from the reaction that yielded revealed a monomeric complex with only monodentate perrhenate coordination, [UO2(ReO4)2(H2O)(TiBP)2] (2'). These results represent the first structural evidence for the bridging coordination mode of perrhenate on coordination to an actinide and yields further insight into the possible solvent phase pertechnetate complexes that may exist in PUREX process phosphate rich solvent.

  11. Solid state and aqueous behavior of uranyl peroxide cage clusters

    NASA Astrophysics Data System (ADS)

    Pellegrini, Kristi Lynn

    Uranyl peroxide cage clusters include a large family of more than 50 published clusters of a variety of sizes, which can incorporate various ligands including pyrophosphate and oxalate. Previous studies have reported that uranyl clusters can be used as a method to separate uranium from a solid matrix, with potential applications in reprocessing of irradiated nuclear fuel. Because of the potential applications of these novel structures in an advanced nuclear fuel cycle and their likely presence in areas of contamination, it is important to understand their behavior in both solid state and aqueous systems, including complex environments where other ions are present. In this thesis, I examine the aqueous behavior of U24Pp 12, as well as aqueous cluster systems with added mono-, di-, and trivalent cations. The resulting solutions were analyzed using dynamic light scattering and ultra-small angle X-ray scattering to evaluate the species in solution. Precipitates of these systems were analyzed using powder X-ray diffraction, X-ray fluorescence spectrometry, and Raman spectroscopy. The results of these analyses demonstrate the importance of cation size, charge, and concentration of added cations on the aqueous behavior of uranium macroions. Specifically, aggregates of various sizes and shapes form rapidly upon addition of cations, and in some cases these aggregates appear to precipitate into an X-ray amorphous material that still contains U24Pp12 clusters. In addition, I probe aggregation of U24Pp12 and U60, another uranyl peroxide cage cluster, in mixed solvent water-alcohol systems. The aggregation of uranyl clusters in water-alcohol systems is a result of hydrogen bonding with polar organic molecules and the reduction of the dielectric constant of the system. Studies of aggregation of uranyl clusters also allow for comparison between the newer uranyl polyoxometalate family and century-old transition metal polyoxometalates. To complement the solution studies of uranyl

  12. The catalytic role of uranyl in formation of polycatechol complexes

    PubMed Central

    2011-01-01

    To better understand the association of contaminant uranium with natural organic matter (NOM) and the fate of uranium in ground water, spectroscopic studies of uranium complexation with catechol were conducted. Catechol provides a model for ubiquitous functional groups present in NOM. Liquid samples were analyzed using Raman, FTIR, and UV-Vis spectroscopy. Catechol was found to polymerize in presence of uranyl ions. Polymerization in presence of uranyl was compared to reactions in the presence of molybdate, another oxyion, and self polymerization of catechol at high pH. The effect of time and dissolved oxygen were also studied. It was found that oxygen was required for self-polymerization at elevated pH. The potential formation of phenoxy radicals as well as quinones was monitored. The benzene ring was found to be intact after polymerization. No evidence for formation of ether bonds was found, suggesting polymerization was due to formation of C-C bonds between catechol ligands. Uranyl was found to form outer sphere complexes with catechol at initial stages but over time (six months) polycatechol complexes were formed and precipitated from solution (forming humic-like material) while uranyl ions remained in solution. Our studies show that uranyl acts as a catalyst in catechol-polymerization. PMID:21396112

  13. Hydrothermal Phase Relations Among Uranyl Minerals at the Nopal I Analog Site

    SciTech Connect

    Murphy, William M.

    2007-07-01

    Uranyl mineral paragenesis at Nopal I is an analog of spent fuel alteration at Yucca Mountain. Petrographic studies suggest a variety of possible hydrothermal conditions for uranium mineralization at Nopal I. Calculated equilibrium phase relations among uranyl minerals show uranophane stability over a broad range of realistic conditions and indicate that uranyl mineral variety reflects persistent chemical potential heterogeneity. (author)

  14. Passage of TBP-uranyl complexes from aqueous-organic interface to the organic phase: insights from molecular dynamics simulation.

    PubMed

    Sahu, Pooja; Ali, Sk Musharaf; Shenoy, Kalasanka Trivikram

    2016-08-24

    The present study reports molecular dynamics simulations for biphasic systems comprising tributyl phosphate (TBP) in dodecane and uranyl nitrate in the aqueous phase, which are key chemical species in the well-known Pu-U extraction (PUREX) process. An attempt has been made to understand the nature of interface and mechanism of 'TBP associated uranyl' crossing under neutral and acidic conditions. Results show that the solvent density undergoes large fluctuation near the interface depending on the nature of the aqueous-organic phase. The study provides compelling evidence of experimentally observed reorganization of interfacial complexes at the interface and their structural reformation during extraction. It has been observed that the surface active nature of TBP and their interfacial coverage is modulated by the nature of incorporated solute species and their location with respect to the interface. Also, the TBP structuring near the interface is destroyed when an acidic interface is considered rather than a neutral one which favors the uranyl extraction. With an acidic interface, the water humidity of organic phase was observed to be increased in the experiments. Furthermore, the acid/water solubility in the organic phase was observed to be influenced by selection of acid models and their concentration. Simulations with high acid concentration show water pocket formation in the organic phase. However, in the case of dissociated ions or a mixture of both, no such water pool is observed and the extracted water remains dispersed in the organic phase, having the tendency to be replaced by HNO3 because of preferred TBP·HNO3 complexation over TBP·H2O. Most remarkably, the present study makes evident the TBP-induced charge redistribution of uranyl complexes during migration from the interface to the bulk organic phase, which contributes to drive uranyl complexes such as UO2·NO3·4TBP, UO2·5TBP and UO2·NO3·3TBP·HNO3 in the organic phase, and this was reestablished by

  15. Uranyl peroxide enhanced nuclear fuel corrosion in seawater

    PubMed Central

    Armstrong, Christopher R.; Nyman, May; Shvareva, Tatiana; Sigmon, Ginger E.; Burns, Peter C.; Navrotsky, Alexandra

    2012-01-01

    The Fukushima-Daiichi nuclear accident brought together compromised irradiated fuel and large amounts of seawater in a high radiation field. Based on newly acquired thermochemical data for a series of uranyl peroxide compounds containing charge-balancing alkali cations, here we show that nanoscale cage clusters containing as many as 60 uranyl ions, bonded through peroxide and hydroxide bridges, are likely to form in solution or as precipitates under such conditions. These species will enhance the corrosion of the damaged fuel and, being thermodynamically stable and kinetically persistent in the absence of peroxide, they can potentially transport uranium over long distances. PMID:22308442

  16. Binding of oxime group to uranyl ion.

    PubMed

    Tsantis, Sokratis T; Zagoraiou, Eirini; Savvidou, Aikaterini; Raptopoulou, Catherine P; Psycharis, Vassilis; Szyrwiel, Lukasz; Hołyńska, Małgorzata; Perlepes, Spyros P

    2016-05-31

    Currently, the leading approach for extraction of uranium from seawater is selective sorption of UO2(2+) ions onto a poly(acrylamidoxime) fiber. Amidoxime functional groups are the most studied extractant moieties for this application, but are not perfectly selective, and understanding how these groups (and more generally the oxime groups) interact with UO2(2+) and competing ions in seawater is an important step in designing better extractants. We have started a new research programme aiming at in-depth studies of the uranyl-oxime/amidoxime interactions and we report here our first results which cover aspects of the coordination chemistry of 2-pyridyl ketoximes towards UO2(2+). Detailed synthetic investigations of various UO2(2+)/mepaoH and UO2(2+)/phpaoH reaction systems (mepaoH is methyl 2-pyridyl ketoxime and phpaoH is phenyl 2-pyridyl ketoxime) have provided access to the complexes [UO2(mepao)2(MeOH)2]{[UO2(NO3)(mepao)(MeOH)2]}2 (), [UO2(mepao)2(MeOH)2] (), [(UO2)2(O2)(O2CMe)2(mepaoH)2] () and [UO2(phpao)2(MeOH)2] (). The peroxido group in , which was isolated without the addition of external peroxide sources, probably arises from a bis(aquo)- and/or bis(hydroxido)-bridged diuranyl precursor in solution followed by photochemical oxidation of the bridging groups. The U(VI) atom in the [UO2(NO3)(mepao)(MeOH)2] molecules of () is surrounded by one nitrogen and seven oxygen atoms in a very distorted hexagonal bipyramidal geometry; two oxygen atoms from the terminal MeOH ligands, two oxygen atoms from the bidentate chelating nitrato group, and the oxygen and nitrogen atoms from the η(2) oximate group of the 1.110 (Harris notation) mepao(-) ligand define the equatorial plane. This plane consists of two terminal MeOH ligands and two η(2) oximate groups in the [UO2(mepao)2(MeOH)2] molecule () of . The structure of the [UO2(mepao)2(MeOH)2] molecule that is present in is very similar to the structure of the corresponding molecule in . The structure of the dinuclear

  17. Effects of essential fatty acid deficiency on epidermal O-acylsphingolipids and transepidermal water loss in young pigs.

    PubMed

    Melton, J L; Wertz, P W; Swartzendruber, D C; Downing, D T

    1987-09-25

    Linoleate-rich O-acylglucosylceramides and acylceramides are thought to be of major significance for the physical structure and function of the epidermal permeability barrier. In the present investigation, the effects of a linoleate-free diet on O-acylsphingolipids and their associated functions were investigated. Starting at 5 days of age, male pigs were fed diets containing 12% of either lard or hydrogenated coconut oil. Transepidermal water loss was measured with an electrolytic water analyzer at weekly intervals. Pigs were killed at intervals, and epidermal lipids were isolated and analyzed. Fatty acid compositions were determined by gas-liquid chromatography (GLC). Within 2-3 weeks, pigs on the diet containing coconut oil began to display biochemical and physiological symptoms of essential fatty acid deficiency. Within 2 months, this group had extremely scaly skin and transepidermal water loss was elevated to five times that of controls. The progressive increase in transepidermal water loss correlated with replacement of linoleate by oleate in both acylceramide and acylglucosylceramide. The formation of lamellar granules and intercellular lipid sheets in the stratum corneum was not impaired in essential fatty acid deficiency as judged by electron microscopy. These results suggest that the linoleic acid normally found in the O-acylsphingolipids is not essential for formation of the epidermal membrane system. Rather, it appears that the nature of the ester-linked fatty acid in the O-acylsphingolipids regulates the permeability of this membrane system.

  18. SERUM VITAMIN B12, IRON AND FOLIC ACID DEFICIENCIES IN OBESE INDIVIDUALS SUBMITTED TO DIFFERENT BARIATRIC TECHNIQUES

    PubMed Central

    SILVA, Rafaella de Andrade; MALTA, Flávia Monteiro França; CORREIA, Maria Flora Ferreira Sampaio Carvalho; BURGOS, Maria Goretti Pessoa de Araújo

    2016-01-01

    ABSTRACT Background: Different surgical techniques to combat obesity combine malabsorption with restrictive procedures and can lead to metabolic problems, such as micronutrient deficiencies. Aim: Assess vitamin B12, iron and folic acid deficiencies associated with the lifestyle of obese individuals having been submitted to different bariatric techniques. Methods: A retrospective analysis was performed using the electronic charts of patients submitted to bariatric surgery involving adjustable gastric banding and Roux-en-Y gastric bypass at the São João Hospital Center in the city of Porto, Portugal, between 2005 and 2010. The following data were collected: surgical technique, sex, age, marital status, serum concentrations of vitamin B12, iron and folic acid and postoperative lifestyle. A 5% significance level was used for the statistical analysis (p<0.05). Results: Among 286 individuals evaluated, females accounted for 90.9% of the overall sample (both techniques). Gastric banding was performed more (68.9%), but greater nutrient deficiencies were found following gastric bypass. Iron was the most prevalent deficiency (21.3%), followed by vitamin B12 (16.9%) and folic acid (4.5%). Mild to moderate alcohol intake, adherence to the diet and the use of multivitamins reduced the frequency, but did not avoid micronutrient deficiency. Conclusion: Vitamin B12, iron and folic acid deficiencies were found in the first and second year following the two bariatric techniques analyzed and were more frequent among individuals submitted to gastric bypass. PMID:27683779

  19. Thermodynamics of Uranyl Minerals: Enthalpies of Formation of Uranyl Oxide Hydrates

    SciTech Connect

    K. Kubatko; K. Helean; A. Navrotsky; P.C. Burns

    2005-05-11

    The enthalpies of formation of seven uranyl oxide hydrate phases and one uranate have been determined using high-temperature oxide melt solution calorimetry: [(UO{sub 2}){sub 4}O(OH){sub 6}](H{sub 2}O){sub 5}, metaschoepite; {beta}-UO{sub 2}(OH){sub 2}; CaUO{sub 4}; Ca(UO{sub 2}){sub 6}O{sub 4}(OH){sub 6}(H{sub 2}O){sub 8}, becquerelite; Ca(UO{sub 2}){sub 4}O{sub 3}(OH){sub 4}(H{sub 2}O){sub 2}; Na(UO{sub 2})O(OH), clarkeite; Na{sub 2}(UO{sub 2}){sub 6}O{sub 4}(OH){sub 6}(H{sub 2}O){sub 7}, the sodium analogue of compreignacite and Pb{sub 3}(UO{sub 2}){sub 8}O{sub 8}(OH){sub 6}(H{sub 2}O){sub 2}, curite. The enthalpy of formation from the binary oxides, {Delta}H{sub f-ox}, at 298 K was calculated for each compound from the respective drop solution enthalpy, {Delta}H{sub ds}. The standard enthalpies of formation from the elements, {Delta}H{sub f}{sup o}, at 298 K are -1791.0 {+-} 3.2, -1536.2 {+-} 2.8, -2002.0 {+-} 3.2, -11389.2 {+-} 13.5, -6653.1 {+-} 13.8, -1724.7 {+-} 5.1, -10936.4 {+-} 14.5 and -13163.2 {+-} 34.4 kJ mol{sup -1}, respectively. These values are useful in exploring the stability of uranyl oxide hydrates in auxiliary chemical systems, such as those expected in U-contaminated environments.

  20. Multi-scale modelling of uranyl chloride solutions

    SciTech Connect

    Nguyen, Thanh-Nghi; Duvail, Magali Villard, Arnaud; Dufrêche, Jean-François; Molina, John Jairo; Guilbaud, Philippe

    2015-01-14

    Classical molecular dynamics simulations with explicit polarization have been successfully used to determine the structural and thermodynamic properties of binary aqueous solutions of uranyl chloride (UO{sub 2}Cl{sub 2}). Concentrated aqueous solutions of uranyl chloride have been studied to determine the hydration properties and the ion-ion interactions. The bond distances and the coordination number of the hydrated uranyl are in good agreement with available experimental data. Two stable positions of chloride in the second hydration shell of uranyl have been identified. The UO{sub 2}{sup 2+}-Cl{sup −} association constants have also been calculated using a multi-scale approach. First, the ion-ion potential averaged over the solvent configurations at infinite dilution (McMillan-Mayer potential) was calculated to establish the dissociation/association processes of UO{sub 2}{sup 2+}-Cl{sup −} ion pairs in aqueous solution. Then, the association constant was calculated from this potential. The value we obtained for the association constant is in good agreement with the experimental result (K{sub UO{sub 2Cl{sup +}}} = 1.48 l mol{sup −1}), but the resulting activity coefficient appears to be too low at molar concentration.

  1. First principles NEXAFS simulations of N-donor Uranyl complexes

    NASA Astrophysics Data System (ADS)

    Pemmaraju, C. D.; Duan, R.; Copping, R.; Jeon, B.; Teat, S. J.; Janousch, M.; Tyliszczak, T.; Canning, A.; Grønbech-Jensen, N.; Shuh, D. K.; Prendergast, D.

    2013-03-01

    The synthesis and study of soft-donor uranyl complexes can provide new insights into the coordination chemistry of non-aqueous [UO]2+ Recently, the tunable N-donor ligand 2,6-Bis(2-benzimidazyl)pyridine (BBP) was employed to produce novel uranyl complexes in which the [UO]2+ cation is ligated by anionic and covalent groups with discrete chemical differences. In this work we investigate the electronic structure of the three such uranyl-BBP complexes via near-edge X-ray absorption fine structure (NEXAFS) experiments and simulations using the eXcited electron and Core-Hole (XCH) approach. The evolution of the structural as well as electronic properties across the three complexes is studied systematically. Computed N K-edge and O K-edge NEXAFS spectra are compared with experiment and spectral features assigned to specific electronic transitions in these complexes. Studying the variations in spectral features arising from N K-edge absorption provides a clear picture of ligand-uranyl bonding in these systems.

  2. Uranyl ion extraction with conventional PUREX/TRUEX ligands assessed by electroanalytical chemistry at micro liquid/liquid interfaces.

    PubMed

    Stockmann, Tom J; Ding, Zhifeng

    2011-10-01

    The facilitated ion transfer (FIT) of uranyl or dioxouranium (UO(2)(2+)) was studied electrochemically using a micro interface between two immiscible electrolytic solutions (micro-ITIES) in order to evaluate the complexation stoichiometry and complexation constants (β) of two widely used ligands in spent fuel reprocessing: tributylphosphate (TBP) and octyl(phenyl)-N,N-diisobutylcarbamoylmethyl-phosphine oxide (CMPO). For the first time, discrete interfacial complexation reaction steps of varying uranyl to the two ligands ratios were resolved using the micro-ITIES hosted at the tip of a 25 μm diameter glass capillary. Two stoichiometries for UO(2)NO(3)TBP(n)(+) were determined including n = 3 and 4 with β values of 3.2 × 10(11) and 3.9 × 10(13), respectively. Subsequently, three distinct complexation reactions of CMPO with UO(2)(2+) were discovered corresponding to UO(2)NO(3)CMPO(2)(+), UO(2)NO(3)CMPO(3)(+), and UO(2)CMPO(5)(2+) whose respective complexation constants were determined to be 8.0 × 10(11), 8.8 × 10(14), and 6.5 × 10(32). The participation of nitrate anions in these complexation reactions is also discussed.

  3. Uranyl ion extraction with conventional PUREX/TRUEX ligands assessed by electroanalytical chemistry at micro liquid/liquid interfaces.

    PubMed

    Stockmann, Tom J; Ding, Zhifeng

    2011-10-01

    The facilitated ion transfer (FIT) of uranyl or dioxouranium (UO(2)(2+)) was studied electrochemically using a micro interface between two immiscible electrolytic solutions (micro-ITIES) in order to evaluate the complexation stoichiometry and complexation constants (β) of two widely used ligands in spent fuel reprocessing: tributylphosphate (TBP) and octyl(phenyl)-N,N-diisobutylcarbamoylmethyl-phosphine oxide (CMPO). For the first time, discrete interfacial complexation reaction steps of varying uranyl to the two ligands ratios were resolved using the micro-ITIES hosted at the tip of a 25 μm diameter glass capillary. Two stoichiometries for UO(2)NO(3)TBP(n)(+) were determined including n = 3 and 4 with β values of 3.2 × 10(11) and 3.9 × 10(13), respectively. Subsequently, three distinct complexation reactions of CMPO with UO(2)(2+) were discovered corresponding to UO(2)NO(3)CMPO(2)(+), UO(2)NO(3)CMPO(3)(+), and UO(2)CMPO(5)(2+) whose respective complexation constants were determined to be 8.0 × 10(11), 8.8 × 10(14), and 6.5 × 10(32). The participation of nitrate anions in these complexation reactions is also discussed. PMID:21848323

  4. Influence of a dietary n-3 fatty acid deficiency on the cerebral catecholamine contents, EEG and learning ability in rat.

    PubMed

    Takeuchi, Takashi; Fukumoto, Yutaka; Harada, Etsumori

    2002-04-01

    Female rats were fed on a diet deficient in (n-3) fatty acid or enriched in docosahexaenoic acid (DHA) diet from mating and throughout pregnancy and lactation. Pups fed on the same diet as their dams were used for experiments. The effects of dietary (n-3) fatty acid deficiency on cerebral catecholamine contents and electroencephalogram (EEG) in rat pups during the postnatal development were investigated. The (n-3) deficient rat pups showed significantly lower levels of noradrenaline (NA) in cerebral cortex, hippocampus and striatum, compared with those in the DHA adequate rats. Dopamine (DA) contents were significantly lower in the (n-3) deficient rats until the 7th day of age. These results were consistent with observations in the EEG analysis, relative powers of fast activities in the EEG recorded from the (n-3) deficient rats were significantly lower than those in the DHA adequate rats. The effect of supplementation with DHA in (n-3) deficient rats on learning ability was also studied in a model of learning, active avoidance test and three-panel run way test, after weaning. Although the percentages of avoidance in the (n-3) deficient rats (saline group) were constantly 20% or less until the 3rd session, the percentage of avoidance in the DHA supplemented rats rapidly increased to 53% following the first administration. While in the three-panel runway test, there were no significant differences between two groups. These results suggest that chronic consumption of a (n-3) fatty acid deficient diet could modify the biosynthesis of catecholamine in the brain, and might induce the behavioral disturbances. Furthermore, the decreased learning ability induced by (n-3) deficiency in the active avoidance test is a reversible following a supplementing DHA after the weaning.

  5. Membrane omega-3 Fatty Acid deficiency as a preventable risk factor for comorbid coronary heart disease in major depressive disorder.

    PubMed

    McNamara, Robert K

    2009-01-01

    Major depression disorder (MDD) significantly increases the risk for coronary heart disease (CHD) which is a leading cause of mortality in patients with MDD. Moreover, depression is frequently observed in a subset of patients following acute coronary syndrome (ACS) and increases risk for mortality. Here evidence implicating omega-3 (n-3) fatty acid deficiency in the pathoaetiology of CHD and MDD is reviewed, and the hypothesis that n-3 fatty acid deficiency is a preventable risk factor for CHD comorbidity in MDD patients is evaluated. This hypothesis is supported by cross-national and cross-sectional epidemiological surveys finding an inverse correlation between n-3 fatty acid status and prevalence rates of both CHD and MDD, prospective studies finding that lower dietary or membrane EPA+DHA levels increase risk for both MDD and CHD, case-control studies finding that the n-3 fatty acid status of MDD patients places them at high risk for emergent CHD morbidity and mortality, meta-analyses of controlled n-3 fatty acid intervention studies finding significant advantage over placebo for reducing depression symptom severity in MDD patients, and for secondary prevention of cardiac events in CHD patients, findings that n-3 fatty acid status is inversely correlated with other documented CHD risk factors, and patients diagnosed with MDD after ACS exhibit significantly lower n-3 fatty acid status compared with nondepressed ACS patients. This body of evidence provides strong support for future studies to evaluate the effects of increasing dietary n-3 fatty acid status on CHD comorbidity and mortality in MDD patients.

  6. Potential of essential fatty acid deficiency with extremely low fat diet in lipoprotein lipase deficiency during pregnancy: A case report

    PubMed Central

    Tsai, Elaine C; Brown, Judy A; Veldee, Megan Y; Anderson, Gregory J; Chait, Alan; Brunzell, John D

    2004-01-01

    Background Pregnancy in patients with lipoprotein lipase deficiency is associated with high risk of maternal pancreatitis and fetal death. A very low fat diet (< 10% of calories) is the primary treatment modality for the prevention of acute pancreatitis, a rare but potentially serious complication of severe hypertriglyceridemia. Since pregnancy can exacerbate hypertriglyceridemia in the genetic absence of lipoprotein lipase, a further reduction of dietary fat intake to < 1–2% of total caloric intake may be required during the pregnancy, along with the administration of a fibrate. It is uncertain if essential fatty acid deficiency will develop in the mother and fetus with this extremely low fat diet, or whether fibrates will cross the placenta and concentrate in the fetus. Case presentation A 23 year-old gravida 1 woman with primary lipoprotein lipase deficiency was seen at 7 weeks of gestation in the Lipid Clinic for management of severe hypertriglyceridemia that had worsened with pregnancy. While on her habitual fat intake of 10% of total calories, her pregnancy resulted in an exacerbation of the hypertriglyceridemia, which prompted further restriction of fat intake to < 2% of total calories, as well as administration of gemfibrozil at a lower than average dose. The level of gemfibrozil, as the active metabolite, in the venous and arterial fetal cord blood was within the expected therapeutic range for adults. The clinical signs and a biomarker of essential fatty acid deficiency, namely the ratio of 20:3 [n-9] to 20:4 [n-6] fatty acids, were closely monitored throughout her pregnancy. Despite her extremely low fat diet, the levels of essential fatty acids measured in the mother and in the fetal blood immediately postpartum were normal. Normal essential fatty acid levels may have been achieved by the topical application of sunflower oil. Conclusions An extremely low fat diet in combination with topical sunflower oil and gemfibrozil administration was safely

  7. Self-assembly of Alkali-uranyl-peroxide Clusters

    SciTech Connect

    Nyman, May; Rodriquez, Mark A.; Campana, Charles F.

    2010-08-11

    The hexavalent uranium specie, uranyl triperoxide, UO2(O2)34-, has been shown recently to behave like high oxidation-state d0 transition-metals, self-assembling into polyoxometalate-like clusters that contain up to 60 uranyl cations bridged by peroxide ligands. There has been much less focus on synthesis and structural characterization of salts of the monomeric UO2(O2)34- building block of these clusters. However, these could serve as water-soluble uranyl precursors for both clusters and materials, and also be used as simple models to study aqueous behavior by experiment and modeling. The countercation is of utmost importance to the assembly of these clusters, and Li+ has proven useful for the crystallization of many of the known cluster geometries to date. We present in this paper synthesis and structural characterization of two monomeric lithium uranyl-peroxide salts, Li4[UO2(O2)3]·10H2O (1) and [UO2(O2)3]12[(UO2(OH)4)Li16(H2O)28]3·Li6[H2O]26 (2). They were obtained from aqueous-alcohol solutions rather than the analogous aqueous solutions from which lithium uranyl-peroxide clusters are crystallized. Rapid introduction of the alcohol gives the structure of (1) whereas slow diffusion of alcohol results in crystallization of (2). (2) is an unusual structure featuring uranyl-centered alkali clusters that are linked into ring and spherical arrangements via [UO2(O2)3] anions. Furthermore, partial substitution of Rb or Cs into the synthesis results in formation of (2) with substitution of these larger alkalis into the uranyl-centered clusters. We surmise that the slow crystallization allows for direct bonding of alkali metals to the

  8. Influence of Contact Time on the Extraction of 233Uranyl Spike and Contaminant Uranium From Hanford Sediment

    SciTech Connect

    Smith, Steven C.; Szecsody, James E.

    2011-11-01

    In this study 233Uranyl nitrate was added to uranium (U) contaminated Hanford 300 Area sediment and incubated under moist conditions for 1 year. It hypothesized that geochemical transformations and/or physical processes will result in decreased extractability of 233U as the incubation period increases, and eventually the extraction behavior of the 233U spike will be congruent to contaminant U that has been associated with sediment for decades. Following 1 week, 1 month, and 1 year incubation periods, sediment extractions were performed using either batch or dynamic (sediment column flow) chemical extraction techniques. Overall, extraction of U from sediment using batch extraction was less complicated to conduct compared to dynamic extraction, but dynamic extraction could distinguish the range of U forms associated with sediment which are eluted at different times.

  9. Biochemical characterization of a uranyl ion-specific DNAzyme.

    PubMed

    Brown, Andrea K; Liu, Juewen; He, Ying; Lu, Yi

    2009-02-13

    Uranyl ion-specific DNAzyme: A DNAzyme (lower strand) cleaves the substrate (upper strand) in the presence of the uranyl ion. The enzyme folds into a bulged three-way-junction structure with catalytically important nucleotides residing in the bulge. A highly conserved GA mismatch is also crucial for the enzyme's activity.The biochemical characterization of a DNAzyme that is highly specific for uranyl (UO(2) (2+)) ions is described. Sequence alignment, enzyme truncation, and mutation studies have resulted in a conserved sequence that folds into a bulged stem-loop structure. Interestingly, a GA pair next to the scissile site is important for the uranyl ion-specific DNAzyme; this is reminiscent of the GT wobble base pair adjacent to the cleavage site that is crucial for the Pb(II)-specific 8-17 DNAzyme activity. Therefore wobble pairs might be important for formation of metal-specific metal-binding sites in DNAzymes. The DNAzyme binds the uranyl ion with a dissociation constant of 469 nM, which is among the strongest metal-binding affinities in nucleic acid enzymes reported to date. This explains why a catalytic beacon fluorescent sensor based on this enzyme has a detection limit (45 pM) that rivals the most-sensitive analytical instrument. It also has over 1 000 000-fold specificity for the uranyl ion over other metal ions. The DNAzyme can carry out multiple turnover reactions that follow the Michaelis-Menten equation, with a k(cat) of 1.46 min(-1) and a K(M) of 463 nM, similar to that of the 8-17 DNAzyme. The pH profile shows a bell-shaped curve that reaches a maximum at pH 5.5, at which the in vitro selection was carried out; this suggests that in vitro selection can be performed to obtain DNAzymes with optimal performance under specific conditions under which practical applications are required. These findings enrich our fundamental understanding of metal-binding sites in nucleic acids and allow the design of sensors with better performance.

  10. Np Incorporation into Uranyl Alteration Phases: A Quantum Mechanical Approach

    SciTech Connect

    Shuller, Lindsay; Ewing, Rodney C. |; Becker, Udo

    2007-07-01

    Neptunium is a major contributor to the long-term radioactivity in a geologic repository for spent nuclear fuel (SNF) due to its long half-life (2.1 million years). The mobility of Np may be decreased by its incorporation into the U{sup 6+} phases that form during the corrosion of SNF. The ionic radii of Np{sup 5+} (0.089 nm) and U{sup 6+} (0.087 nm) are similar, as is their chemistry. Experimental studies have shown that Np can be incorporated into uranyl phases up to concentrations on the order of 100 ppm. The low concentration of Np in the uranyl phases complicates experimental detection and presents a significant challenge for determining the incorporation mechanism. Therefore, we have used quantum mechanical calculations to investigate incorporation mechanisms and evaluate the energetics of Np substituting for U. CASTEP, a density functional theory based code that uses plane waves to model the behavior of the valence electrons and pseudo-potentials to model the behavior of the core and inner valence electrons, was used to calculate optimal H positions, relaxed geometry, and the energy of different uranyl phases. The incorporation energy for Np into uranyl alteration phases was calculated for studtite, [(UO{sub 2})O{sub 2}(H{sub 2}O){sub 2}](H{sub 2}O){sub 2}, and boltwoodite, HK(UO{sub 2})(SiO{sub 4}) 1.5(H{sub 2}O). Studtite is the rare case of a stable, naturally-occurring peroxide mineral, in this case a uranyl hydroxyl peroxide that forms in the presence of H{sub 2}O{sub 2} from the radiolysis of H{sub 2}O. For studtite, two incorporation mechanisms were evaluated: (1) charge-balanced substitution of Np{sup 5+} and H{sup +} for one U{sup 6+}, and (2) direct substitution of Np{sup 6+} for U{sup 6+}. For boltwoodite, the H atomic positions prior to Np incorporation were determined, as well as the Np incorporation mechanisms and the corresponding substitution energies. The preferential incorporation of Np into different structure types of U{sup 6+} minerals

  11. Complex nanoscale cage clusters built from uranyl polyhedra and phosphate tetrahedra

    SciTech Connect

    Unruh, Daniel K.; Ling, Jie; Qiu, Jie; Pressprich, Laura; Baranay, Melissa; Ward, Matthew; Burns, Peter C.

    2011-06-20

    Five cage clusters that self-assemble in alkaline aqueous solution have been isolated and characterized. Each is built from uranyl hexagonal bipyramids with two or three equatorial edges occupied by peroxide, and three also contain phosphate tetrahedra. These clusters contain 30 uranyl polyhedra; 30 uranyl polyhedra and six pyrophosphate groups; 30 uranyl polyhedra, 12 pyrophosphate groups, and one phosphate tetrahedron; 42 uranyl polyhedra; and 40 uranyl polyhedra and three pyrophosphate groups. These clusters present complex topologies as well as a range of compositions, sizes, and charges. Two adopt fullerene topologies, and the others contain combinations of topological squares, pentagons, and hexagons. An analysis of possible topologies further indicates that higher-symmetry topologies are favored.

  12. Association between very long chain fatty acids in the meibomian gland and dry eye resulting from n-3 fatty acid deficiency.

    PubMed

    Tanaka, Hideko; Harauma, Akiko; Takimoto, Mao; Moriguchi, Toru

    2015-06-01

    In our previously study, we reported lower tear volume in with an n-3 fatty acid deficient mice and that the docosahexaenoic acid and total n-3 fatty acid levels in these mice are significantly reduced in the meibomian gland, which secretes an oily tear product. Furthermore, we noted very long chain fatty acids (≥25 carbons) in the meibomian gland. To verify the detailed mechanism of the low tear volume in the n-3 fatty acid-deficient mice, we identified the very long chain fatty acids in the meibomian gland, measured the fatty acid composition in the tear product. Very long chain fatty acids were found to exist as monoesters. In particular, very long chain fatty acids with 25-29 carbons existed for the most part as iso or anteiso branched-chain fatty acids. n-3 fatty acid deficiency was decreased the amount of meibum secretion from meibomian gland without change of fatty acid composition. These results suggest that the n-3 fatty acid deficiency causes the enhancement of evaporation of tear film by reducing oily tear secretion along with the decrease of meibomian gland function.

  13. Simulation of Uranyl Nitrate Crystallization Process in Linear Crystallizer Using Simsar Software

    NASA Astrophysics Data System (ADS)

    Ochoa Bique, A.; Gozhimov, A.; Chursin, Yu; Schmidt, O.

    2016-08-01

    The paper deals with simulation of linear crystallizer work process for the research of technic operating modes and searching the most effective for material's nano-purity achievement. The model is realized by using SimSar software. Importance of device's geometry and process variables are marked. The model was included in the complex's composition of closed nuclear fuel cycle.

  14. Tetracycline in uranyl nitrate intoxication: Its action on renal damage and U retention in bone

    SciTech Connect

    Guglielmotti, M.B.; Ubios, A.M.; Larumbe, J.; Cabrini, R.L. )

    1989-09-01

    In acute intoxication, uranium (U) not only inhibits bone formation but its excretion in urine also causes renal damage. The former effect is ameliorated by tetracycline (TC), probably due to its chelation property, which might also prevent U deposition in bone. Chemical determination of U incorporated in bone and a histological study of the kidneys were performed on animals injected with U and then treated with TC. The results showed that TC was unable to prevent the binding of U to bone while it exacerbated U-induced renal damage.

  15. Radiolysis of hexavalent plutonium in solutions of uranyl nitrate containing fission product simulants

    NASA Astrophysics Data System (ADS)

    Rance, Peter J. W.; Zilberman, B. Ya.; Akopov, G. A.

    2000-07-01

    The effect of the inherent radioactivity on the chemical state of plutonium ions in solution was recognized very shortly after the first macroscopic amounts of plutonium became available and early studies were conducted as part of the Manhattan Project. However, the behavior of plutonium ions, in nitric acid especially, has been found to be somewhat complex, so much so that a relatively modern summary paper included the comment that, "The vast amount of work carried out in nitric acid solutions can not be adequately summarized. Suffice it to say results in these solutions are plagued with irreproducibility and induction periods…" Needless to say, the presence of other ions in solution, as occurs when irradiated nuclear fuel is dissolved, further complicates matters. The purpose of the work described below was to add to the rather small amount of qualitative data available relating to the radiolytic behavior of plutonium in solutions of irradiated nuclear fuel.

  16. Electrochemical uranyl cation biosensor with DNA oligonucleotides as receptor layer.

    PubMed

    Jarczewska, Marta; Ziółkowski, Robert; Górski, Łukasz; Malinowska, Elżbieta

    2014-04-01

    The present study aims at the further development of the uranyl oligonucleotide-based voltammetric biosensor, which takes advantage of strong interaction between UO2(2+) and phosphate DNA backbone. Herein we report the optimization of working parameters of previously elaborated electrochemical DNA biosensor. It is shown that the sensor sensitivity is highly dependent on the oligonucleotide probe length and the incubation time of sensor in a sample solution. Consequently, the highest sensitivity was obtained for 10-nucleotide sequence and 60 min incubation time. The lower detection limit towards uranyl cation for developed biosensor was 30 nM. The influence of mixed monolayers and the possibility of developing a non-calibration device were also investigated. The selectivity of the proposed biosensor was significantly improved via elimination of adenine nucleobases from the DNA probe. Moreover, the regeneration procedure was elaborated and tested to prolong the use of the same biosensor for 4 subsequent determinations of UO2(2+).

  17. Application of time-resolved luminescence spectroscopy to a remote uranyl sensor

    NASA Astrophysics Data System (ADS)

    Varineau, Pierre T.; Duesing, Richard W., Jr.; Wangen, Larry E.

    1992-03-01

    Time-resolved luminescence spectroscopy is an effective method for the determination of a wide range of uranyl concentrations in aqueous samples. We have applied this technique to the development of a remote-sensing device using fiber optic cables coupled with a microflow cell to probe for uranyl in aqueous samples. This sensor incorporates a Nafion membrane through which UO22+ can diffuse into a reaction/analysis chamber containing phosphoric acid, a reagent that enhances the uranyl luminescence intensity and lifetime. With this device, anionic and fluorescing organic interferences could be eliminated, allowing for the determination of uranyl over a concentration range of 10-4 to 10-9 M.

  18. Aggregation-induced emission active tetraphenylethene-based sensor for uranyl ion detection.

    PubMed

    Wen, Jun; Huang, Zeng; Hu, Sheng; Li, Shuo; Li, Weiyi; Wang, Xiaolin

    2016-11-15

    A novel tetraphenylethene-based fluorescent sensor, TPE-T, was developed for the detection of uranyl ions. The selective binding of TPE-T to uranyl ions resulted in a detectable signal owing to the quenching of its aggregation-induced emission. The developed sensor could be used to visually distinguish UO2(2+) from lanthanides, transition metals, and alkali metals under UV light; the presence of other metal ions did not interfere with the detection of uranyl ions. In addition, TPE-T was successfully used for the detection of uranyl ions in river water, illustrating its potential applications in environmental systems. PMID:27439180

  19. Structural Phase Transitions and Water Dynamics in Uranyl Fluoride Hydrates

    SciTech Connect

    Miskowiec, Andrew J.; Kirkegaard, Marie C.; Huq, Ashfia; Mamontov, Eugene; Herwig, Kenneth W.; Trowbridge, Lee D.; Rondinone, Adam Justin; Anderson, Brian B.

    2015-11-17

    We report a novel production method for uranium oxy uoride [(UO2)7F14(H2O)7] 4H2O, referred to as structure D. Structure D is produced as a product of hydrating anhydrous uranyl uoride, UO2F2, through the gas phase at ambient temperatures fol- lowed by desiccation by equilibration with a dry environment. We follow the structure of [(UO2)7F14(H2O)7] 4H2O through an intermediate, liquid-like phase, wherein the coordination number of the uranyl ion is reduced to 5 (from 6 in the anhydrous struc- ture), and a water molecule binds as an equatorial ligand to the uranyl ion. Quasielas- tic neutron scattering results compare well with previous measurements of mineral hydrates. The two groups of structurally distinct water molecules in D perform re- stricted motion on a length scale commensurate with the O{H bond (r = 0.92 A). The more tightly bound equatorial ligand waters rotate slower (Dr = 2.2 ps-1) than their hydrogen-bonded partners (Dr = 28.7 ps-1).

  20. Structure and bonding in crystalline cesium uranyl tetrachloride under pressure.

    PubMed

    Osman, Hussien H; Pertierra, Pilar; Salvadó, Miguel A; Izquierdo-Ruiz, F; Recio, J M

    2016-07-21

    A thorough investigation of pressure effects on the structural properties of crystalline cesium uranyl chloride was performed by means of first-principles calculations within the density functional theory framework. Total energies, equilibrium geometries and vibrational frequencies were computed at selected pressures up to 50 GPa. Zero pressure results present good agreement with available experimental and theoretical data. Our calculated equation of state parameters reveal that Cs2UO2Cl4 is a high compressible material, similar to other ionic compounds with cesium cations, and displays a structural anisotropic behavior guided by the uranyl moiety. An unexpected variation of the U-O bond length, dUO, is detected as pressure is applied. It leads to a dUO-stretching frequency relationship that cannot be described by the traditional Badger's rule. Interestingly enough, it can be explained in terms of a change in the main factor controlling dUO. At low pressure, the charge transferred to the uranyl cation induces an increase of the bond length and a red shift of the stretching frequencies, whereas it is the mechanical effect of the applied pressure above 10 GPa that is the dominant factor that leads to a shortening of dUO and a blue shift of the stretching frequencies. PMID:27340008

  1. Electron transfer dissociation of dipositive uranyl and plutonyl coordination complexes.

    PubMed

    Rios, Daniel; Rutkowski, Philip X; Shuh, David K; Bray, Travis H; Gibson, John K; Van Stipdonk, Michael J

    2011-12-01

    Reported here is a comparison of electron transfer dissociation (ETD) and collision-induced dissociation (CID) of solvent-coordinated dipositive uranyl and plutonyl ions generated by electrospray ionization. Fundamental differences between the ETD and CID processes are apparent, as are differences between the intrinsic chemistries of uranyl and plutonyl. Reduction of both charge and oxidation state, which is inherent in ETD activation of [An(VI) O(2) (CH(3) COCH(3) )(4) ](2+) , [An(VI) O(2) (CH(3) CN)(4) ](2) , [U(VI) O(2) (CH(3) COCH(3) )(5) ](2+) and [U(VI) O(2) (CH(3) CN)(5) ](2+) (An = U or Pu), is accompanied by ligand loss. Resulting low-coordinate uranyl(V) complexes add O(2) , whereas plutonyl(V) complexes do not. In contrast, CID of the same complexes generates predominantly doubly-charged products through loss of coordinating ligands. Singly-charged CID products of [U(VI) O(2) (CH(3) COCH(3) )(4,5) ](2+) , [U(VI) O(2) (CH(3) CN)(4,5) ](2+) and [Pu(VI) O(2) (CH(3) CN)(4) ](2+) retain the hexavalent metal oxidation state with the addition of hydroxide or acetone enolate anion ligands. However, CID of [Pu(VI) O(2) (CH(3) COCH(3) )(4) ](2+) generates monopositive plutonyl(V) complexes, reflecting relatively more facile reduction of Pu(VI) to Pu(V). PMID:22223415

  2. Structure and bonding in crystalline cesium uranyl tetrachloride under pressure.

    PubMed

    Osman, Hussien H; Pertierra, Pilar; Salvadó, Miguel A; Izquierdo-Ruiz, F; Recio, J M

    2016-07-21

    A thorough investigation of pressure effects on the structural properties of crystalline cesium uranyl chloride was performed by means of first-principles calculations within the density functional theory framework. Total energies, equilibrium geometries and vibrational frequencies were computed at selected pressures up to 50 GPa. Zero pressure results present good agreement with available experimental and theoretical data. Our calculated equation of state parameters reveal that Cs2UO2Cl4 is a high compressible material, similar to other ionic compounds with cesium cations, and displays a structural anisotropic behavior guided by the uranyl moiety. An unexpected variation of the U-O bond length, dUO, is detected as pressure is applied. It leads to a dUO-stretching frequency relationship that cannot be described by the traditional Badger's rule. Interestingly enough, it can be explained in terms of a change in the main factor controlling dUO. At low pressure, the charge transferred to the uranyl cation induces an increase of the bond length and a red shift of the stretching frequencies, whereas it is the mechanical effect of the applied pressure above 10 GPa that is the dominant factor that leads to a shortening of dUO and a blue shift of the stretching frequencies.

  3. Predicting Stability Constants for Uranyl Complexes Using Density Functional Theory

    DOE PAGES

    Vukovic, Sinisa; Hay, Benjamin P.; Bryantsev, Vyacheslav S.

    2015-04-02

    The ability to predict the equilibrium constants for the formation of 1:1 uranyl:ligand complexes (log K1 values) provides the essential foundation for the rational design of ligands with enhanced uranyl affinity and selectivity. We also use density functional theory (B3LYP) and the IEFPCM continuum solvation model to compute aqueous stability constants for UO22+ complexes with 18 donor ligands. Theoretical calculations permit reasonably good estimates of relative binding strengths, while the absolute log K1 values are significantly overestimated. Accurate predictions of the absolute log K1 values (root mean square deviation from experiment < 1.0 for log K1 values ranging from 0more » to 16.8) can be obtained by fitting the experimental data for two groups of mono and divalent negative oxygen donor ligands. The utility of correlations is demonstrated for amidoxime and imide dioxime ligands, providing a useful means of screening for new ligands with strong chelate capability to uranyl.« less

  4. Structural Phase Transitions and Water Dynamics in Uranyl Fluoride Hydrates.

    PubMed

    Miskowiec, Andrew; Kirkegaard, Marie C; Huq, Ashfia; Mamontov, Eugene; Herwig, Kenneth W; Trowbridge, Lee; Rondinone, Adam; Anderson, Brian

    2015-12-10

    We report a novel production method for uranium oxyfluoride [(UO2)7F14(H2O)7]·4H2O, referred to as structure D. Structure D is produced as a product of hydrating anhydrous uranyl fluoride, UO2F2, through the gas phase at ambient temperatures followed by desiccation by equilibration with a dry environment. We follow the structure of [(UO2)7F14(H2O)7]·4H2O through an intermediate, liquid-like phase, wherein the coordination number of the uranyl ion is reduced to 5 (from 6 in the anhydrous structure), and a water molecule binds as an equatorial ligand to the uranyl ion. Quasielastic neutron scattering results compare well with previous measurements of mineral hydrates. The two groups of structurally distinct water molecules in D perform restricted motion on a length scale commensurate with the O-H bond (r = 0.92 Å). The more tightly bound equatorial ligand waters rotate slower (Dr = 2.2 ps(-1)) than their hydrogen-bonded partners (Dr = 28.7 ps(-1)). PMID:26575434

  5. Structural Phase Transitions and Water Dynamics in Uranyl Fluoride Hydrates

    DOE PAGES

    Miskowiec, Andrew J.; Kirkegaard, Marie C.; Huq, Ashfia; Mamontov, Eugene; Herwig, Kenneth W.; Trowbridge, Lee D.; Rondinone, Adam Justin; Anderson, Brian B.

    2015-11-17

    We report a novel production method for uranium oxy uoride [(UO2)7F14(H2O)7] 4H2O, referred to as structure D. Structure D is produced as a product of hydrating anhydrous uranyl uoride, UO2F2, through the gas phase at ambient temperatures fol- lowed by desiccation by equilibration with a dry environment. We follow the structure of [(UO2)7F14(H2O)7] 4H2O through an intermediate, liquid-like phase, wherein the coordination number of the uranyl ion is reduced to 5 (from 6 in the anhydrous struc- ture), and a water molecule binds as an equatorial ligand to the uranyl ion. Quasielas- tic neutron scattering results compare well with previousmore » measurements of mineral hydrates. The two groups of structurally distinct water molecules in D perform re- stricted motion on a length scale commensurate with the O{H bond (r = 0.92 A). The more tightly bound equatorial ligand waters rotate slower (Dr = 2.2 ps-1) than their hydrogen-bonded partners (Dr = 28.7 ps-1).« less

  6. Predicting Stability Constants for Uranyl Complexes Using Density Functional Theory

    SciTech Connect

    Vukovic, Sinisa; Hay, Benjamin P.; Bryantsev, Vyacheslav S.

    2015-04-02

    The ability to predict the equilibrium constants for the formation of 1:1 uranyl:ligand complexes (log K1 values) provides the essential foundation for the rational design of ligands with enhanced uranyl affinity and selectivity. We also use density functional theory (B3LYP) and the IEFPCM continuum solvation model to compute aqueous stability constants for UO22+ complexes with 18 donor ligands. Theoretical calculations permit reasonably good estimates of relative binding strengths, while the absolute log K1 values are significantly overestimated. Accurate predictions of the absolute log K1 values (root mean square deviation from experiment < 1.0 for log K1 values ranging from 0 to 16.8) can be obtained by fitting the experimental data for two groups of mono and divalent negative oxygen donor ligands. The utility of correlations is demonstrated for amidoxime and imide dioxime ligands, providing a useful means of screening for new ligands with strong chelate capability to uranyl.

  7. How are Centrosymmetric and Noncentrosymmetric Structures Achieved in Uranyl Borates?

    SciTech Connect

    Wang, Shuao; Alekseev, Evgeny V.; Stritzinger, Jared T.; Depmeier, Wulf; Albrecht-Schmitt, Thomas E.

    2010-03-15

    Four uranyl borates, UO{sub 2}B{sub 2}O{sub 4} (UBO-1), α-(UO{sub 2}){sub 2}[B{sub 9}O{sub 14}(OH){sub 4}] (UBO-2), β-(UO{sub 2}){sub 2}[B{sub 9}O{sub 14}(OH){sub 4}] (UBO-3), and (UO{sub 2}){sub 2}[B{sub 13}O{sub 20}(OH){sub 3}]·1.25H{sub 2}O (UBO-4), have been prepared from boric acid fluxes at 190 °C. UBO-3 and UBO-4 are centrosymmetric, whereas UBO-1 and UBO-2 are noncentrosymmetric (chiral and polar). These uranyl borates possess layered structures constructed from UO{sub 8} hexagonal bipyramids, BO{sub 3} triangles, and BO{sub 4} tetrahedra. In the case of UBO-4, clusters of BO{sub 3} triangles link the layers together to form open slabs with a thickness of almost 2 nm. The ability of uranyl borates to use very similar layers to yield both centrosymmetric and noncentrosymmetric layers is detailed in this work.

  8. Enhanced environmental detection of uranyl compounds based on luminescence characterization

    NASA Astrophysics Data System (ADS)

    Nelson, Jean Dennis

    Uranium (U) contamination can be introduced to the environment as a result of mining and manufacturing activities related to nuclear power, detonation of U-containing munitions (DoD), or nuclear weapons production/processing (DOE facilities). In oxidizing environments such as surface soils, U predominantly exists as U(VI), which is highly water soluble and very mobile in soils. U(VI) compounds typically contain the UO22+ group (uranyl compounds). The uniquely structured and long-lived green luminescence (fluorescence) of the uranyl ion (under UV radiation) has been studied and remained a strong topic of interest for two centuries. The presented research is distinct in its objective of improving capabilities for remotely sensing U contamination by understanding what environmental conditions are ideal for detection and need to be taken into consideration. Specific focuses include: (1) the accumulation and fluorescence enhancement of uranyl compounds at soil surfaces using distributed silica gel, and (2) environmental factors capable of influencing the luminescence response, directly or indirectly. In a complex environmental system, matrix effects co-exist from key soil parameters including moisture content (affected by evaporation, temperature and humidity), soil texture, pH, CEC, organic matter and iron content. Chapter 1 is a review of pertinent background information and provides justification for the selected key environmental parameters. Chapter 2 presents empirical investigations related to the fluorescence detection and characterization of uranyl compounds in soil and aqueous samples. An integrative experimental design was employed, testing different soils, generating steady-state fluorescence spectra, and building a comprehensive dataset which was then utilized to simultaneously test three hypotheses: The fluorescence detection of uranyl compounds is dependent upon (1) the key soil parameters, (2) the concentration of U contamination, and (3) time of analysis

  9. Early development of essential fatty acid deficiency in rats: Fat-free vs. hydrogenated coconut oil diet

    PubMed Central

    Ling, Pei-Ra; De Leon, Charlotte E.; Le, Hau; Puder, Mark; Bistrian, Bruce R.

    2011-01-01

    This study examined the effects of feeding an essential fatty acid deficient (EFAD) diet either without fat or with added hydrogenated coconut oil (HCO) on fatty acid profiles in rats. Both diets induced equivalent biochemical evidence of EFAD reflected by the triene/tetraene ratio in plasma phospholipids within 2 weeks. However, the HCO diet led to larger increases of 16:1n7 and 18:1n9 in muscle but smaller increases in fat tissue and plasma triglycerides than the fat-free diet, suggesting greater increases in hepatic de novo lipogenesis with the latter. In addition, the HCO diet led to larger decreases of some 18:3n3 metabolites, particularly 22:6n3, in muscle, fat and brain tissues than the fat-free diet, presumably related to lesser stimulation of elongation and desaturation. Thus, these secondary effects of an EFAD diet on fatty acid metabolism can be modified by the saturated fat in the diet while the primary impact of both diets on development of EFAD is unaffected. PMID:20675109

  10. Alkali metal nitrate purification

    DOEpatents

    Fiorucci, Louis C.; Morgan, Michael J.

    1986-02-04

    A process is disclosed for removing contaminants from impure alkali metal nitrates containing them. The process comprises heating the impure alkali metal nitrates in solution form or molten form at a temperature and for a time sufficient to effect precipitation of solid impurities and separating the solid impurities from the resulting purified alkali metal nitrates. The resulting purified alkali metal nitrates in solution form may be heated to evaporate water therefrom to produce purified molten alkali metal nitrates suitable for use as a heat transfer medium. If desired, the purified molten form may be granulated and cooled to form discrete solid particles of purified alkali metal nitrates.

  11. Uranyl Ion Complexes with 1,1'-Biphenyl-2,2',6,6'-tetracarboxylic Acid: Structural and Spectroscopic Studies of One- to Three-Dimensional Assemblies.

    PubMed

    Thuéry, Pierre; Harrowfield, Jack

    2015-07-01

    1,1'-Biphenyl-2,2',6,6'-tetracarboxylic acid (H4L) was reacted with uranyl nitrate, either alone or in the presence of additional metal cations (Ni(2+), Cu(2+), Dy(3+)) under (solvo)-hydrothermal conditions, giving six complexes which were characterized by their crystal structure and, in all but one case, their emission spectrum in the solid state. [Ni(bipy)3][UO2(H2L)(H2O)]2(NO3)2·3H2O (1) crystallizes as a one-dimensional (1D), ribbon-like coordination polymer, while the homometallic complex [(UO2)2(L)(H2O)3]·H2O·CH3CN (2) and the heterometallic complexes [UO2Cu(L)(H2O)2]·H2O (3), [UO2Cu(L)(H2O)]·H2O (4), and [(UO2)5Cu4(HL)6(bipy)4]·2H2O (5) display two-dimensional (2D) arrangements. Lastly, the uranyl-lanthanide heterometallic complex [(UO2)8Dy(HL)6(H2O)8](I)·8H2O (6) crystallizes as a three-dimensional (3D) framework. Although these assemblies adopt different topologies, the {4(2).6} linear motif found in 1 is discernible in the structures of 2, 5, and 6, in which the higher dimensionality arises from further bridging of these subunits by uranyl (2), copper (5), or both uranyl and dysprosium (6) cations. The tetracarboxylic/ate ligands have their two aromatic rings nearly perpendicular to one another. No two of them adopt the same coordination mode in this series (except in the similar complexes 3 and 4), but chelation involving one carboxylate group from each ring is nearly ubiquitous, and the ensuing position of the cation favors the formation of planar architectures. The emission spectra of complexes 2-5 measured in the solid state show the usual uranyl vibronic fine structure, although with significant differences in the emission intensity, while complete quenching of the luminescence is observed in 1. PMID:26102315

  12. SERS detection of uranyl using functionalized gold nanostars promoted by nanoparticle shape and size.

    PubMed

    Lu, Grace; Forbes, Tori Z; Haes, Amanda J

    2016-08-15

    The radius of curvature of gold (Au) nanostar tips but not the overall particle dimensions can be used for understanding the large and quantitative surface-enhanced Raman scattering (SERS) signal of the uranyl (UO2)(2+) moiety. The engineered roughness of the Au nanostar architecture and the distance between the gold surface and uranyl cations are promoted using carboxylic acid terminated alkanethiols containing 2, 5, and 10 methylene groups. By systematically varying the self-assembled monolayer (SAM) thickness with these molecules, the localized surface plasmon resonance (LSPR) spectral properties are used to quantify the SAM layer thickness and to promote uranyl coordination to the Au nanostars in neutral aqueous solutions. Successful uranyl detection is demonstrated for all three functionalized Au nanostar samples as indicated by enhanced signals and red-shifts in the symmetric U(vi)-O stretch. Quantitative uranyl detection is achieved by evaluating the integrated area of these bands in the uranyl fingerprint window. By varying the concentration of uranyl, similar free energies of adsorption are observed for the three carboxylic acid terminated functionalized Au nanostar samples indicating similar coordination to uranyl, but the SERS signals scale inversely with the alkanethiol layer thickness. This distance dependence follows previously established models assuming that roughness features associated with the radius of curvature of the tips are considered. These results indicate that SERS signals using functionalized Au nanostar substrates can provide quantitative detection of small molecules and that the tip architecture plays an important role in understanding the resulting SERS intensities. PMID:27326897

  13. Silver Ion-Mediated Heterometallic Three-Fold Interpenetrating Uranyl-Organic Framework.

    PubMed

    Mei, Lei; Wu, Qun-yan; An, Shu-wen; Gao, Zeng-qiang; Chai, Zhi-fang; Shi, Wei-qun

    2015-11-16

    A unique case of a uranyl-silver heterometallic 3-fold interpenetrating network (U-Ag-2,6-DCPCA) from a multifunctionalized organic ligand, 2,6-dichloroisonicotinic acid, in the presence of uranyl and silver ions is reported. It is the first report of a heterometallic uranyl-organic interpenetrating network or framework. Notably, a (4,4)-connected uranyl building unit in U-Ag-2,6-DCPCA, which is available through combined influences of structural halogenation and silver ion additive on uranyl coordination, plays a vital role in the formation of a 3-fold interpenetrating network. Halogen substitution effectively changes structural features and coordination behaviors of isonicotinate ligand and contributes to the control of uranyl coordination. Meanwhile, it exerts influence on the stabilization of 3-fold interpenetrating networks by halogen-halogen interactions. Theoretical calculation suggests that the silver ion should mainly serve as an inductive factor of uranyl species through strong Ag-N binding affinity, directly leading to the formation of a (4,4)-connected uranyl building unit and finally a heterometallic 3-fold interpenetrating network. Related experimental results, especially an interesting postsynthetic metalation, afford further evidence of this induction effect.

  14. A protein engineered to bind uranyl selectively and with femtomolar affinity

    NASA Astrophysics Data System (ADS)

    Zhou, Lu; Bosscher, Mike; Zhang, Changsheng; Özçubukçu, Salih; Zhang, Liang; Zhang, Wen; Li, Charles J.; Liu, Jianzhao; Jensen, Mark P.; Lai, Luhua; He, Chuan

    2014-03-01

    Uranyl (UO22+), the predominant aerobic form of uranium, is present in the ocean at a concentration of ~3.2 parts per 109 (13.7 nM) however, the successful enrichment of uranyl from this vast resource has been limited by the high concentrations of metal ions of similar size and charge, which makes it difficult to design a binding motif that is selective for uranyl. Here we report the design and rational development of a uranyl-binding protein using a computational screening process in the initial search for potential uranyl-binding sites. The engineered protein is thermally stable and offers very high affinity and selectivity for uranyl with a Kd of 7.4 femtomolar (fM) and >10,000-fold selectivity over other metal ions. We also demonstrated that the uranyl-binding protein can repeatedly sequester 30-60% of the uranyl in synthetic sea water. The chemical strategy employed here may be applied to engineer other selective metal-binding proteins for biotechnology and remediation applications.

  15. Catalytic one-electron reduction of uranyl(VI) to Group 1 uranyl(V) complexes via Al(III) coordination.

    PubMed

    Zegke, Markus; Nichol, Gary S; Arnold, Polly L; Love, Jason B

    2015-04-01

    Reactions between the uranyl(VI) Pacman complex [(UO2)(py)(H2L)] of the Schiff-base polypyrrolic macrocycle L and Tebbe's reagent or DIBAL result in the first selective reductive functionalisation of the uranyl oxo by Al to form [(py)(R2AlOUO)(py)(H2L)] (R = Me or (i)Bu). The clean displacement of the oxo-coordinated Al(III) by Group 1 cations has enabled the development of a one-pot, DIBAL-catalysed reduction of the U(VI) uranyl complexes to a series of new, mono-oxo alkali-metal-functionalised uranyl(V) complexes [(py)3(MOUO)(py)(H2L)] (M = Li, Na, K).

  16. Effects of aqueous uranyl speciation on the kinetics of microbial uranium reduction

    NASA Astrophysics Data System (ADS)

    Belli, Keaton M.; DiChristina, Thomas J.; Van Cappellen, Philippe; Taillefert, Martial

    2015-05-01

    The ability to predict the success of the microbial reduction of soluble U(VI) to highly insoluble U(IV) as an in situ bioremediation strategy is complicated by the wide range of geochemical conditions at contaminated sites and the strong influence of aqueous uranyl speciation on the bioavailability and toxicity of U(VI) to metal-reducing bacteria. To determine the effects of aqueous uranyl speciation on uranium bioreduction kinetics, incubations and viability assays with Shewanella putrefaciens strain 200 were conducted over a range of pH and dissolved inorganic carbon (DIC), Ca2+, and Mg2+ concentrations. A speciation-dependent kinetic model was developed to reproduce the observed time series of total dissolved uranium concentration over the range of geochemical conditions tested. The kinetic model yielded the highest rate constant for the reduction of uranyl non-carbonate species (i.e., the 'free' hydrated uranyl ion, uranyl hydroxides, and other minor uranyl complexes), indicating that they represent the most readily reducible fraction of U(VI) despite being the least abundant uranyl species in solution. The presence of DIC, Ca2+, and Mg2+ suppressed the formation of more bioavailable uranyl non-carbonate species and resulted in slower bioreduction rates. At high concentrations of bioavailable U(VI), however, uranium toxicity to S. putrefaciens inhibited bioreduction, and viability assays confirmed that the concentration of non-carbonate uranyl species best predicts the degree of toxicity. The effect of uranium toxicity was accounted for by incorporating the free ion activity model of metal toxicity into the bioreduction rate law. Overall, these results demonstrate that, in the absence of competing terminal electron acceptors, uranium bioreduction kinetics can be predicted over a wide range of geochemical conditions based on the bioavailability and toxicity imparted on U(VI) by solution composition. These findings also imply that the concentration of uranyl non

  17. Folic acid deficiency increases delayed neuronal death, DNA damage, platelet endothelial cell adhesion molecule-1 immunoreactivity, and gliosis in the hippocampus after transient cerebral ischemia.

    PubMed

    Hwang, In Koo; Yoo, Ki-Yeon; Suh, Hong-Won; Kim, Young Sup; Kwon, Dae Young; Kwon, Young-Guen; Yoo, Jun-Hyun; Won, Moo-Ho

    2008-07-01

    Folic acid deficiency increases stroke risk. In the present study, we examined whether folic acid deficiency enhances neuronal damage and gliosis via oxidative stress in the gerbil hippocampus after transient forebrain ischemia. Animals were exposed to a folic acid-deficient diet (FAD) for 3 months and then subjected to occlusion of both common carotid arteries for 5 min. Exposure to an FAD increased plasma homocysteine levels by five- to eightfold compared with those of animals fed with a control diet (CD). In CD-treated animals, most neurons were dead in the hippocampal CA1 region 4 days after ischemia/reperfusion, whereas, in FAD-treated animals, this occurred 3 days after ischemia/reperfusion. Immunostaining for 8-hydroxy-2'-deoxyguanosine (8-OHdG) was performed to examine DNA damage in CA1 neurons in both groups after ischemia, and it was found that 8-OHdG immunoreactivity in both FAD and CD groups peaked at 12 hr after reperfusion, although the immunoreactivity in the FAD group was much greater than that in the CD group. Platelet endothelial cell adhesion molecule-1 (PECAM-1; a final mediator of neutrophil transendothelial migration) immunoreactivity in both groups increased with time after ischemia/reperfusion: Its immunoreactivity in the FAD group was much higher than that in the CD group 3 days after ischemia/reperfusion. In addition, reactive gliosis in the ischemic CA1 region increased with time after ischemia in both groups, but astrocytosis and microgliosis in the FAD group were more severe than in the CD group at all times after ischemia. Our results suggest that folic acid deficiency enhances neuronal damage induced by ischemia.

  18. Long-term effects of perinatal essential fatty acid deficiency on anxiety-related behavior in mice.

    PubMed

    Palsdottir, Vilborg; Månsson, Jan-Eric; Blomqvist, Maria; Egecioglu, Emil; Olsson, Bob

    2012-04-01

    Dietary essential fatty acids have been shown to regulate behavioral and cognitive functions in rodents. However, the long-term effect on behavior, besides memory and learning, of essential fatty acid deficiency (EFAD), i.e., lack of n-3 and n-6 fatty acids, during the perinatal period has not been investigated. Therefore, pregnant C57Bl/6 mice were given either an EFAD or an isoenergetic control diet from gestational day 16 and throughout lactation. The female offspring were given standard chow from 3 weeks of age, and at 12 to 14 weeks of age, open-field, object recognition, light-dark transition, elevated plus maze, and social interaction tests were performed. The brain glycerophospholipid fatty acid composition was investigated in 3-week-old and adult offspring by gas chromatography. The differences observed in behavior were indicative of lower anxiety in the EFAD mice compared to controls illustrated by more time spent in the open arms of the elevated plus maze (+ 41%, p < .05) and in the light compartment in the light-dark transition test (+ 63%, p < .05). The proportion of total n-3 fatty acids, especially 22:6n-3 in the brain, was lower with a compensatory increase in the proportion of total n-6 fatty acids, foremost 22:5n-6, in the EFAD mice compared to controls at 3 weeks of age. In the adult brains the fatty acid composition was normalized. In conclusion, our data show that EFAD during the perinatal period results in short-term alterations of fatty acid composition in brain and decreased anxiety in adult life. PMID:22352789

  19. 21 CFR 181.33 - Sodium nitrate and potassium nitrate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Sodium nitrate and potassium nitrate. 181.33...-Sanctioned Food Ingredients § 181.33 Sodium nitrate and potassium nitrate. Sodium nitrate and potassium nitrate are subject to prior sanctions issued by the U.S. Department of Agriculture for use as sources...

  20. 21 CFR 181.33 - Sodium nitrate and potassium nitrate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Sodium nitrate and potassium nitrate. 181.33 Section 181.33 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... nitrate and potassium nitrate. Sodium nitrate and potassium nitrate are subject to prior sanctions...

  1. 21 CFR 181.33 - Sodium nitrate and potassium nitrate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Sodium nitrate and potassium nitrate. 181.33...-Sanctioned Food Ingredients § 181.33 Sodium nitrate and potassium nitrate. Sodium nitrate and potassium nitrate are subject to prior sanctions issued by the U.S. Department of Agriculture for use as sources...

  2. 21 CFR 181.33 - Sodium nitrate and potassium nitrate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Sodium nitrate and potassium nitrate. 181.33...-Sanctioned Food Ingredients § 181.33 Sodium nitrate and potassium nitrate. Sodium nitrate and potassium nitrate are subject to prior sanctions issued by the U.S. Department of Agriculture for use as sources...

  3. Construction of Uranyl Selective Electrode Based on Complex of Uranyl Ion with New Ligand Carboxybenzotriazole in PVC Matrix Membrane

    NASA Astrophysics Data System (ADS)

    Abu-Dalo, M. A.; Al-Rawashdeh, N. A. F.; Al-Mheidat, I. R.; Nassory, N. S.

    2015-10-01

    In the present study uranyl selective electrodes in polyvinyl chloride (PVC) matrix membrane were prepared based on a complex of uranyl ion (UO2) with carboxybenzotriazole (CBT) as ligand. The effect of the nature of plasticizer in PVC matrix were evaluated using three different plasticizers, these are dibutyl phthalate (DBP), dioctyl phthalate (DOP) and bis(2-ethylhexyl) sebacate (BHS). The results of this study indicated that the best plasticizer could be used is the DBP, which may be attributed to its lowest viscosity value compared to DOP and BHS. The electrodes with DBP as plasticizer exhibits a Nernstian response with a slope of 28.0 mV/ decade, over a wide range of concentration from 3.0×10-5-6.0×10-2 M and a detection limit of 4.0×10-6 M. It can be used in the pH range of 4.0-10.0 with a response time of less than 10 s for DBP and 25 s for both DOP and BHS. The effects of ions interferences on the electrode response were evaluated. The di- and tri-valent cations were found to interfere less than univalent cations, which was attributed to the high diffusion and the exchange rate between the univalent ions and the uranyl ion solution. The electrodes were characterized by Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron microscopy (SEM). The results of the standard addition method were satisfactory with errors less than 7%. The developed electrode was found to be fast, sensitive and reliable indicated its potential use in measuring the uranly ion concentration in the field.

  4. Time-dependent water dynamics in hydrated uranyl fluoride

    SciTech Connect

    Miskowiec, Andrew J.; Anderson, Brian B.; Herwig, Kenneth W.; Huq, Ashfia; Mamontov, Eugene; Rondinone, Adam; Trowbridge, Lee D.

    2015-09-15

    In this study, uranyl fluoride is a three-layer, hexagonal structure with significant stacking disorder in the c-direction. It supports a range of unsolved ‘thermodynamic’ hydrates with 0–2.5 water molecules per uranium atom, and perhaps more. However, the relationship between water, hydrate crystal structures, and thermodynamic results, collectively representing the chemical pathway through these hydrate structures, has not been sufficiently elucidated. We used high-resolution quasielastic neutron scattering to study the dynamics of water in partially hydrated uranyl fluoride powder over the course of 4 weeks under closed conditions. The spectra are composed of two quasielastic components: one is associated with translational diffusive motion of water that is approximately five to six times slower than bulk water, and the other is a slow (on the order of 2–300 ps), spatially bounded water motion. The translational component represents water diffusing between the weakly bonded layers in the crystal, while the bounded component may represent water trapped in subnanometre ‘pockets’ formed by the space between uranium-centred polymerisation units. Complementary neutron diffraction measurements do not show any significant structural changes, suggesting that a chemical conversion of the material does not occur in the thermodynamically isolated system on this timescale.

  5. Time-dependent water dynamics in hydrated uranyl fluoride

    DOE PAGES

    Miskowiec, Andrew J.; Anderson, Brian B.; Herwig, Kenneth W.; Huq, Ashfia; Mamontov, Eugene; Rondinone, Adam; Trowbridge, Lee D.

    2015-09-15

    In this study, uranyl fluoride is a three-layer, hexagonal structure with significant stacking disorder in the c-direction. It supports a range of unsolved ‘thermodynamic’ hydrates with 0–2.5 water molecules per uranium atom, and perhaps more. However, the relationship between water, hydrate crystal structures, and thermodynamic results, collectively representing the chemical pathway through these hydrate structures, has not been sufficiently elucidated. We used high-resolution quasielastic neutron scattering to study the dynamics of water in partially hydrated uranyl fluoride powder over the course of 4 weeks under closed conditions. The spectra are composed of two quasielastic components: one is associated with translationalmore » diffusive motion of water that is approximately five to six times slower than bulk water, and the other is a slow (on the order of 2–300 ps), spatially bounded water motion. The translational component represents water diffusing between the weakly bonded layers in the crystal, while the bounded component may represent water trapped in subnanometre ‘pockets’ formed by the space between uranium-centred polymerisation units. Complementary neutron diffraction measurements do not show any significant structural changes, suggesting that a chemical conversion of the material does not occur in the thermodynamically isolated system on this timescale.« less

  6. Surface complexation modeling of uranyl adsorption on corrensite from the Waste Isolation Pilot Plant Site

    SciTech Connect

    Park, Sang-Won; Leckie, J.O.; Siegel, M.D.

    1995-09-01

    Corrensite is the dominant clay mineral in the Culebra Dolomite at the Waste Isolation Pilot Plant. The surface characteristics of corrensite, a mixed chlorite/smectite clay mineral, have been studied. Zeta potential measurements and titration experiments suggest that the corrensite surface contains a mixture of permanent charge sites on the basal plane and SiOH and AlOH sites with a net pH-dependent charge at the edge of the clay platelets. Triple-layer model parameters were determined by the double extrapolation technique for use in chemical speciation calculations of adsorption reactions using the computer program HYDRAQL. Batch adsorption studies showed that corrensite is an effective adsorbent for uranyl. The pH-dependent adsorption behavior indicates that adsorption occurs at the edge sites. Adsorption studies were also conducted in the presence of competing cations and complexing ligands. The cations did not affect uranyl adsorption in the range studied. This observation lends support to the hypothesis that uranyl adsorption occurs at the edge sites. Uranyl adsorption was significantly hindered by carbonate. It is proposed that the formation of carbonate uranyl complexes inhibits uranyl adsorption and that only the carbonate-free species adsorb to the corrensite surface. The presence of the organic complexing agents EDTA and oxine also inhibits uranyl sorption.

  7. Understanding the bonding nature of uranyl ion and functionalized graphene: a theoretical study.

    PubMed

    Wu, Qun-Yan; Lan, Jian-Hui; Wang, Cong-Zhi; Xiao, Cheng-Liang; Zhao, Yu-Liang; Wei, Yue-Zhou; Chai, Zhi-Fang; Shi, Wei-Qun

    2014-03-20

    Studying the bonding nature of uranyl ion and graphene oxide (GO) is very important for understanding the mechanism of the removal of uranium from radioactive wastewater with GO-based materials. We have optimized 22 complexes between uranyl ion and GO applying density functional theory (DFT) combined with quasi-relativistic small-core pseudopotentials. The studied oxygen-containing functional groups include hydroxyl, carboxyl, amido, and dimethylformamide. It is observed that the distances between uranium atoms and oxygen atoms of GO (U-OG) are shorter in the anionic GO complexes (uranyl/GO(-/2-)) compared to the neutral GO ones (uranyl/GO). The formation of hydrogen bonds in the uranyl/GO(-/2-) complexes can enhance the binding ability of anionic GO toward uranyl ions. Furthermore, the thermodynamic calculations show that the changes of the Gibbs free energies in solution are relatively more negative for complexation reactions concerning the hydroxyl and carboxyl functionalized anionic GO complexes. Therefore, both the geometries and thermodynamic energies indicate that the binding abilities of uranyl ions toward GO modified by hydroxyl and carboxyl groups are much stronger compared to those by amido and dimethylformamide groups. This study can provide insights for designing new nanomaterials that can efficiently remove radionuclides from radioactive wastewater.

  8. Enhanced adsorption and recovery of uranyl ions by NikR mutant-displaying yeast.

    PubMed

    Kuroda, Kouichi; Ebisutani, Kazuki; Iida, Katsuya; Nishitani, Takashi; Ueda, Mitsuyoshi

    2014-04-11

    Uranium is one of the most important metal resources, and the technology for the recovery of uranyl ions (UO22+) from aqueous solutions is required to ensure a semi-permanent supply of uranium. The NikR protein is a Ni2+-dependent transcriptional repressor of the nickel-ion uptake system in Escherichia coli, but its mutant protein (NikRm) is able to selectively bind uranyl ions in the interface of the two monomers. In this study, NikRm protein with ability to adsorb uranyl ions was displayed on the cell surface of Saccharomyces cerevisiae. To perform the binding of metal ions in the interface of the two monomers, two metal-binding domains (MBDs) of NikRm were tandemly fused via linker peptides and displayed on the yeast cell surface by fusion with the cell wall-anchoring domain of yeast α-agglutinin. The NikRm-MBD-displaying yeast cells with particular linker lengths showed the enhanced adsorption of uranyl ions in comparison to the control strain. By treating cells with citrate buffer (pH 4.3), the uranyl ions adsorbed on the cell surface were recovered. Our results indicate that the adsorption system by yeast cells displaying tandemly fused MBDs of NikRm is effective for simple and concentrated recovery of uranyl ions, as well as adsorption of uranyl ions.

  9. Escherichia coli Response to Uranyl Exposure at Low pH and Associated Protein Regulations

    PubMed Central

    Khemiri, Arbia; Carrière, Marie; Bremond, Nicolas; Ben Mlouka, Mohamed Amine; Coquet, Laurent; Llorens, Isabelle; Chapon, Virginie; Jouenne, Thierry; Cosette, Pascal; Berthomieu, Catherine

    2014-01-01

    Better understanding of uranyl toxicity in bacteria is necessary to optimize strains for bioremediation purposes or for using bacteria as biodetectors for bioavailable uranyl. In this study, after different steps of optimization, Escherichia colicells were exposed to uranyl at low pH to minimize uranyl precipitation and to increase its bioavailability. Bacteria were adapted to mid acidic pH before exposure to 50 or 80 µM uranyl acetate for two hours at pH≈3. To evaluate the impact of uranium, growth in these conditions were compared and the same rates of cells survival were observed in control and uranyl exposed cultures. Additionally, this impact was analyzedby two-dimensional differential gel electrophoresis proteomics to discover protein actors specifically present or accumulated in contact with uranium.Exposure to uranium resulted in differential accumulation of proteins associated with oxidative stress and in the accumulation of the NADH/quinone oxidoreductase WrbA. This FMN dependent protein performs obligate two-electron reduction of quinones, and may be involved in cells response to oxidative stress. Interestingly, this WrbA protein presents similarities with the chromate reductase from E. coli, which was shown to reduce uranyl in vitro. PMID:24587082

  10. Uranyl-Promoted Peroxide Generation: Synthesis and Characterization of Three Uranyl Peroxo [(UO2)2(O2)] Complexes.

    PubMed

    Thangavelu, Sonia G; Cahill, Christopher L

    2015-05-01

    Three novel uranyl(VI) peroxide complexes, [(UO2)2(CH3COO)2(O2)(C10H8N2)] (1), [(UO2)2(CH3COO)2(O2)(C12H12N2)] (2), and [(UO2)3(CH3COO)4(O2)(C15H11N3)2] (3), have been synthesized and characterized by single-crystal X-ray diffraction, powder X-ray diffraction, and luminescence spectroscopy. Each of these structures feature a [(UO2)2(O2)] dimer with additional coordination by acetate, 2,2'-bipyridine (BPY), 5,5'-dimethyl-2,2'-bipyridine (MeBPY), or 2,2':6,2″-terpyridine (TPY). Compound 3 consists of an additional uranyl unit functionalized with a TPY donor ligand. The presence of the peroxo ligand in 1-3 is due to in situ generation of peroxide when preparative solutions of 1-3 were exposed to ambient light and/or sunlight.

  11. Density Functional Studies on the Complexation and Spectroscopy of Uranyl Ligated with Acetonitrile and Acetone Derivatives

    SciTech Connect

    Schoendorff, George E.; Windus, Theresa L.; De Jong, Wibe A.

    2009-12-12

    The coordination of nitrile (acetonitrile, propionitrile, and benzonitrile) and carbonyl (formaldehyde, ethanal, and acetone) ligands to the uranyl dication (UO22+) has been examined using density functional theory (DFT) utilizing relativistic effective core potentials (RECPs). Complexes containing up to six ligands have been modeled for all ligands except formaldehyde, for which no minimum could be found. A comparison of relative binding energies indicates that five coordinate complexes are predominant while a six coordinate complex involving propionitrile ligands might be possible. Additionally, the relative binding energy and the weakening of the uranyl bond is related to the size of the ligand and, in general, nitriles bind more strongly to uranyl than carbonyls.

  12. Removal of uranyl ions from residual waters using some algae types

    NASA Astrophysics Data System (ADS)

    Cecal, Al; Palamaru, I.; Humelnicu, D.; Popa, K.; Salaru, V. V.; Rudic, V.; Gulea, A.

    1999-01-01

    This paper deals with a study on the bioaccumulation of uranyl ions resulted from residual effluents by means of some microbiological collectors: Scenedesmus quadricauda, Anabaena karakumica, Calothrix brevissima, Penicillinium sp, as well as the Glucide extract of Porphyridium cruentum, under various experimental conditions. The retaining degree of the bioaccumulated uranyl ions, as well as the leaching degree, in HCl and H2O media, of the same ions previously retained on algae were established. The retaining degree decreases in the serie: Scenedesmus quadricauda >Anabaena karakumica >Penicillinium sp>Calothrix brevissima. The leaching effect of bioaccumulated uranyl ions is higher in hydrochloric acid than in water.

  13. The development of essential fatty acid deficiency in healthy men fed fat-free diets intravenously and orally.

    PubMed

    Wene, J D; Connor, W E; DenBesten, L

    1975-07-01

    The hypothesis that clinical and biochemical essential fatty acid deficiency (EFA) might occur from the feeding of eucaloric, fat-free diets was tested in two experiments in healthy men. In Study I, eight men were given fat-free, eucaloric diets containing 80% of calories as glucose and 20% as amino acid hydrolysates by a constant drip over a 24-h period. The diets were fed in succession for periods of 2 wk each, either through a superior vena cava catheter or via a nasogastric tube. EFA deficiency was detected by decreases in linoleic acid and by the appearance of 5, 8, 11-eicosatrienoic acid in lipid fractions of plasma. Linoleic acid decreased significantly during 2 wk of the fat-free diet given intravenously from 48.8 to 9.8% (percent of total fatty acids) in cholesterol esters, from 21.2 to 3.2% in phospholipids, from 9.6 to 2.0% in free fatty acids, and from 14.1 to 2.6% in triglycerides. Eicosatrienoic acid, normally undetectable, appeared 0.6% in cholesterol esters, 2.5% in phospholipids, 0.2% in free fatty acids, and 2.3% in triglycerides. EFA deficiency occurred similarly during the nasogastric feeding. In Study II a subject received the same diet continuously by the nasogastric route for 10 days followed by a 24-h fast. He was then given the fat-free diet intermittently in three meals per day for 3 days. Finally, he was repleted with a diet containing 2.6% linoleic acid. By the 3rd day of the continuous nasogastric feeding, linoleic acid had fallen significantly and eicosatrienoic acid had appeared in plasma lipid fractions as in Study I. These findings were accentuated by day 10. Adipose tissue fatty acid composition did not change. Free fatty acid outflow from adipose tissue was presumably suppressed during the 10 days of continuous feeding. With increased free fatty acid outflow during fasting and intermittent feeding, linoleic acid rose and eicosatrienoic acid decreased. After 13 days of repletion with dietary linoleic acid, the EFA deficiency

  14. Cylodextrin Polymer Nitrate

    NASA Technical Reports Server (NTRS)

    Kosowski, Bernard; Ruebner, Anja; Statton, Gary; Robitelle, Danielle; Meyers, Curtis

    2000-01-01

    The development of the use of cyclodextrin nitrates as possible components of insensitive, high-energy energetics is outlined over a time period of 12 years. Four different types of cyclodextrin polymers were synthesized, nitrated, and evaluated regarding their potential use for the military and aerospace community. The synthesis of these novel cyclodextrin polymers and different nitration techniques are shown and the potential of these new materials is discussed.

  15. 21 CFR 181.33 - Sodium nitrate and potassium nitrate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Sodium nitrate and potassium nitrate. 181.33...-Sanctioned Food Ingredients § 181.33 Sodium nitrate and potassium nitrate. Sodium nitrate and potassium... nitrite, with or without sodium or potassium nitrite, in the production of cured red meat products...

  16. New three-dimensional inorganic frameworks based on the uranophane-type sheet in monoamine templated uranyl-vanadates

    SciTech Connect

    Jouffret, Laurent; Shao Zhenmian

    2010-10-15

    Seven new uranyl vanadates with mono-protonated amine or tetramethylammonium used as structure directing cations, (C{sub 2}NH{sub 8}){sub 2{l_brace}}[(UO{sub 2})(H{sub 2}O)][(UO{sub 2})(VO{sub 4})]{sub 4{r_brace}}.H{sub 2}O (DMetU5V4) (C{sub 2}NH{sub 8}){l_brace}[(UO{sub 2})(H{sub 2}O){sub 2}][(UO{sub 2})(VO{sub 4})]{sub 3{r_brace}}.H{sub 2}O (DMetU4V3), (C{sub 5}NH{sub 6}){sub 2{l_brace}}[(UO{sub 2})(H{sub 2}O)][(UO{sub 2})(VO{sub 4})]{sub 4{r_brace}}.H{sub 2}O (PyrU5V4), (C{sub 3}NH{sub 10}){l_brace}[(UO{sub 2})(H{sub 2}O){sub 2}][(UO{sub 2})(VO{sub 4})]{sub 3{r_brace}}.H{sub 2}O (isoPrU4V3), (N(CH{sub 3}){sub 4}){l_brace}[(UO{sub 2})(H{sub 2}O){sub 2}][(UO{sub 2})(VO{sub 4})]{sub 3{r_brace}}.H{sub 2}O (TMetU4V3), (C{sub 6}NH{sub 14}){l_brace}[(UO{sub 2})(H{sub 2}O){sub 2}][(UO{sub 2})(VO{sub 4})]{sub 3{r_brace}}.H{sub 2}O (CHexU4V3), and (C{sub 4}NH{sub 12}){l_brace}[(UO{sub 2})(H{sub 2}O)][(UO{sub 2})(VO{sub 4})]{sub 3{r_brace}} (TButU4V3) were prepared from mild-hydrothermal reactions using dimethylamine, pyridine, isopropylamine, tetramethylammonium hydroxide, cyclohexylamine and tertiobutylamine, respectively, with uranyl nitrate and vanadium oxide in acidic medium. The structures were solved using single-crystal X-ray diffraction data. The compounds exhibit three-dimensional uranyl-vanadate inorganic frameworks built from uranophane-type uranyl-vanadate layers pillared by uranyl polyhedra with cavities in between occupied by protonated organic moieties. In the uranyl-vanadate layers the orientations of the vanadate tetrahedra give new geometrical isomers leading to unprecedented pillared systems and new inorganic frameworks with U/V=4/3. Crystallographic data: (DMetU5V4) orthorhombic, Cmc2{sub 1} space group, a=15.6276(4), b=14.1341(4), c=13.6040(4) A; (DMetU4V3) monoclinic, P2{sub 1}/n space group, a=10.2312(4), b=13.5661(7), c=17.5291(7) A, {beta}=96.966(2); (PyrU5V4), triclinic, P1 space group, a=9.6981(3), b=9.9966(2), c=10.5523(2) A, {alpha}=117

  17. Thermochemical nitrate destruction

    DOEpatents

    Cox, John L.; Hallen, Richard T.; Lilga, Michael A.

    1992-01-01

    A method is disclosed for denitrification of nitrates and nitrates present in aqueous waste streams. The method comprises the steps of (1) identifying the concentration nitrates and nitrites present in a waste stream, (2) causing formate to be present in the waste stream, (3) heating the mixture to a predetermined reaction temperature from about 200.degree. C. to about 600.degree. C., and (4) holding the mixture and accumulating products at heated and pressurized conditions for a residence time, thereby resulting in nitrogen and carbon dioxide gas, and hydroxides, and reducing the level of nitrates and nitrites to below drinking water standards.

  18. Gallium nitrate revisited.

    PubMed

    Chitambar, Christopher R

    2003-04-01

    Gallium nitrate, the nitrate salt of the "near-metal" element gallium, is highly effective in the treatment of cancer-related hypercalcemia. Unlike bisphosphonates, gallium nitrate is effective in both parathyroid hormone-related protein-mediated and non-parathyroid hormone-related protein-mediated hypercalcemia. Gallium nitrate's effects on bone are clearly different from those of bisphosphonates. Gallium nitrate enhances calcium and phosphate content of bone and has direct, noncytotoxic effects on osteoclasts at markedly lower doses than those used for the treatment of cancer-related hypercalcemia. The drug may have clinical application in a variety of disorders associated with accelerated bone loss, including multiple myeloma. Gallium nitrate was originally evaluated as an antitumor agent. Its antitumor activity occurs at somewhat higher doses than those used in the treatment of cancer-related hypercalcemia. Gallium nitrate has substantial single-agent activity in the treatment of advanced lymphoma, particularly diffuse large cell lymphoma, small lymphocytic lymphoma, and follicular lymphoma. Because of its profile, including a different mechanism of action and minimal myelosuppression, the drug merits further evaluation in the treatment of advanced lymphoma. Gallium nitrate also has activity in advanced bladder cancer and may be useful in patients with metastatic or unresectable disease failing first-line chemotherapy regimens. Gallium nitrate exhibits a range of dose-dependent pharmacologic actions that provide a basis for its therapeutic potential in a variety of diseases and warrants further investigational evaluation as an antiresorptive and antitumor agent. PMID:12776253

  19. Evaluation of lanthanide salts as alternative stains to uranyl acetate.

    PubMed

    Hosogi, Naoki; Nishioka, Hideo; Nakakoshi, Masamichi

    2015-12-01

    Uranyl acetate (UAc) has been generally used not only as a superb staining reagent for ultrathin sections of plastic-embedded biological materials, but also as high-contrast negative stains for biological macromolecules such as particles of protein or virus. However, the use and purchase of radioactive UAc have been restricted. In this study, we determine the performance of ytterbium triacetate, lutetium triacetate, samarium triacetate and gadolinium triacetate as new staining reagents for biological electron microscopy. We observed chemically fixed spinach (Spinacia oleracea) leaves stained with these reagents. Ultrathin sections were stained with these reagents. Some of them were counterstained with lead citrate. The transmission electron microscopy contrast of spinach organelles was evaluated in sections exposed to the conventional stain and new stains. We show acetate salts of samarium, gadolinium, ytterbium and lutetium could be excellent substitutes for UAc for thin section staining and for negative staining. In addition, each reagent showed appreciable negative-staining effects. PMID:26374081

  20. Evaluation of lanthanide salts as alternative stains to uranyl acetate.

    PubMed

    Hosogi, Naoki; Nishioka, Hideo; Nakakoshi, Masamichi

    2015-12-01

    Uranyl acetate (UAc) has been generally used not only as a superb staining reagent for ultrathin sections of plastic-embedded biological materials, but also as high-contrast negative stains for biological macromolecules such as particles of protein or virus. However, the use and purchase of radioactive UAc have been restricted. In this study, we determine the performance of ytterbium triacetate, lutetium triacetate, samarium triacetate and gadolinium triacetate as new staining reagents for biological electron microscopy. We observed chemically fixed spinach (Spinacia oleracea) leaves stained with these reagents. Ultrathin sections were stained with these reagents. Some of them were counterstained with lead citrate. The transmission electron microscopy contrast of spinach organelles was evaluated in sections exposed to the conventional stain and new stains. We show acetate salts of samarium, gadolinium, ytterbium and lutetium could be excellent substitutes for UAc for thin section staining and for negative staining. In addition, each reagent showed appreciable negative-staining effects.

  1. Adsorption of uranyl species on hydroxylated titanium carbide nanosheet: A first-principles study.

    PubMed

    Zhang, Yu-Juan; Lan, Jian-Hui; Wang, Lin; Wu, Qun-Yan; Wang, Cong-Zhi; Bo, Tao; Chai, Zhi-Fang; Shi, Wei-Qun

    2016-05-01

    In this work, hydroxylated titanium carbide Ti3C2(OH)2, a representative of the two-dimensional transition metal carbides, has been predicted to be an effective adsorbent for uranyl ions in aqueous environments for the first time using density functional theory simulations. The calculations revealed that the uranyl ion can strongly bind with Ti3C2(OH)2 nanosheet in aqueous solution regardless of the presence of anionic ligands such as OH(-), Cl(-) and NO3(-). The bidentate coordination of uranyl to the surface is energetically more favorable than other adsorption configurations, and the uranyl ion prefers to bind with the deprotonated O adsorption site rather than the protonated one on the hydroxylated surface. During the adsorption process, the chemical adsorption as well as the formation of hydrogen bonds is the dominant factor.

  2. Preorganized Peptide Scaffolds as Mimics of Phosphorylated Proteins Binding Sites with a High Affinity for Uranyl.

    PubMed

    Starck, Matthieu; Sisommay, Nathalie; Laporte, Fanny A; Oros, Stéphane; Lebrun, Colette; Delangle, Pascale

    2015-12-01

    Cyclic peptides with two phosphoserines and two glutamic acids were developed to mimic high-affinity binding sites for uranyl found in proteins such as osteopontin, which is believed to be a privileged target of this ion in vivo. These peptides adopt a β-sheet structure that allows the coordination of the latter amino acid side chains in the equatorial plane of the dioxo uranyl cation. Complementary spectroscopic and analytical methods revealed that these cyclic peptides are efficient uranyl chelating peptides with a large contribution from the phosphorylated residues. The conditional affinity constants were measured by following fluorescence tryptophan quenching and are larger than 10(10) at physiological pH. These compounds are therefore promising models for understanding uranyl chelation by proteins, which is relevant to this actinide ion toxicity. PMID:26583259

  3. ARRAYS OF BOTTLES OF PLUTONIUM NITRATE SOLUTION

    SciTech Connect

    Margaret A. Marshall

    2012-09-01

    In October and November of 1981 thirteen approaches-to-critical were performed on a remote split table machine (RSTM) in the Critical Mass Laboratory of Pacific Northwest Laboratory (PNL) in Richland, Washington using planar arrays of polyethylene bottles filled with plutonium (Pu) nitrate solution. Arrays of up to sixteen bottles were used to measure the critical number of bottles and critical array spacing with a tight fitting Plexiglas® reflector on all sides of the arrays except the top. Some experiments used Plexiglas shells fitted around each bottles to determine the effect of moderation on criticality. Each bottle contained approximately 2.4 L of Pu(NO3)4 solution with a Pu content of 105 g Pu/L and a free acid molarity H+ of 5.1. The plutonium was of low 240Pu (2.9 wt.%) content. These experiments were sponsored by Rockwell Hanford Operations because of the lack of experimental data on the criticality of arrays of bottles of Pu solution such as might be found in storage and handling at the Purex Facility at Hanford. The results of these experiments were used “to provide benchmark data to validate calculational codes used in criticality safety assessments of [the] plant configurations” (Ref. 1). Data for this evaluation were collected from the published report (Ref. 1), the approach to critical logbook, the experimenter’s logbook, and communication with the primary experimenter, B. Michael Durst. Of the 13 experiments preformed 10 were evaluated. One of the experiments was not evaluated because it had been thrown out by the experimenter, one was not evaluated because it was a repeat of another experiment and the third was not evaluated because it reported the critical number of bottles as being greater than 25. Seven of the thirteen evaluated experiments were determined to be acceptable benchmark experiments. A similar experiment using uranyl nitrate was benchmarked as U233-SOL-THERM-014.

  4. Polarized x-ray-absorption spectroscopy of the uranyl ion: Comparison of experiment and theory

    SciTech Connect

    Hudson, E.A.; Allen, P.G.; Terminello, L.J.; Denecke, M.A.; Reich, T.

    1996-07-01

    The x-ray linear dichroism of the uranyl ion (UO{sub 2}{sup 2+}) in uranium {ital L}{sub 3}-edge extended x-ray-absorption fine structure (EXAFS), and {ital L}{sub 1}- and {ital L}{sub 3}-edge x-ray-absorption near-edge structure (XANES), has been investigated both by experiment and theory. A striking polarization dependence is observed in the experimental XANES and EXAFS for an oriented single crystal of uranyl acetate dihydrate [UO{sub 2}(CH{sub 3}CO{sub 2}){sub 2}{center_dot}2H{sub 2}O], with the x-ray polarization vector aligned either parallel or perpendicular to the bond axis of the linear uranyl cation (O-U-O). Single-crystal results are compared to experimental spectra for a polycrystalline uranyl acetate sample and to calculations using the {ital ab} {ital initio} multiple-scattering (MS) code FEFF 6. Theoretical XANES spectra for uranyl fluoride (UO{sub 2}F{sub 2}) reproduce all the features of the measured uranyl acetate spectra. By identifying scattering paths which contribute to individual features in the calculated spectrum, a detailed understanding of the {ital L}{sub 1}-edge XANES is obtained. MS paths within the uranyl cation have a notable influence upon the XANES. The measured {ital L}{sub 3}-edge EXAFS is also influenced by MS, especially when the x-ray polarization is parallel to the uranyl species. These MS contributions are extracted from the total EXAFS and compared to calculations. The best agreement with the isolated MS signal is obtained by using nonoverlapped muffin-tin spheres in the FEFF 6 calculation. This contrasts the {ital L}{sub 1}-edge XANES calculations, in which overlapping was required for the best agreement with experiment. {copyright} {ital 1996 The American Physical Society.}

  5. Influence of sex and gonadal hormones on rat-liver and carcass lipids during the development of an essential fatty acid deficiency

    PubMed Central

    Ostwald, Rosemarie; Bouchard, Pauline; Miljanich, P.; Lyman, R. L.

    1965-01-01

    1. Groups of intact male and female rats and castrated rats injected with oestradiol or testosterone were given a diet containing hydrogenated coconut oil for 9 weeks, and at intervals the amounts and fatty acid compositions of the carcass and liver lipids were determined. 2. Male rats grew faster and larger, and exhibited typical external essential fatty acid deficiency symptoms sooner than did females. Testosterone-treated castrated male rats were similar to males, and oestradiol-injected castrated male rats resembled females. 3. Intact females maintained a higher linoleic acid concentration in their carcass than did males. Total amounts of carcass linoleic acid remained similar for all groups, only 200mg. being removed in 9 weeks regardless of body size. 4. The amounts of total cholesteryl esters were independent of liver size. They were higher in males and testosterone-treated castrated male rats than in females and oestrogen-treated castrated male rats. 5. Phospholipids represented about 80% of the liver lipids. The total amounts of the phospholipid linoleic acid and arachidonic acid were similar for all groups regardless of liver size, and were not affected appreciably by the deficiency. Females and oestrogen-treated castrated male rats maintained a higher proportion of phospholipid arachidonic acid for longer periods than did their male counterparts. Both the total amounts and the proportions of eicosatrienoic acid and palmitic acid were higher in males than in females. 6. Supplementation of the essential fatty acid-deficient diet with linoleic acid caused a rapid loss of eicosatrienoic acid and palmitic acid with a concomitant increase in stearic acid and arachidonic acid. 7. There were no obvious differences in the way that the essential fatty acids were metabolized or mobilized from adipose tissue of male or female rats during essential fatty acid deficiency. 8. The results indicated that the greater growth rate of the male rats caused them to require and

  6. Control of oxo-group functionalization and reduction of the uranyl ion.

    PubMed

    Arnold, Polly L; Pécharman, Anne-Frédérique; Lord, Rianne M; Jones, Guy M; Hollis, Emmalina; Nichol, Gary S; Maron, Laurent; Fang, Jian; Davin, Thomas; Love, Jason B

    2015-04-01

    Uranyl complexes of a large, compartmental N8-macrocycle adopt a rigid, "Pacman" geometry that stabilizes the U(V) oxidation state and promotes chemistry at a single uranyl oxo-group. We present here new and straightforward routes to singly reduced and oxo-silylated uranyl Pacman complexes and propose mechanisms that account for the product formation, and the byproduct distributions that are formed using alternative reagents. Uranyl(VI) Pacman complexes in which one oxo-group is functionalized by a single metal cation are activated toward single-electron reduction. As such, the addition of a second equivalent of a Lewis acidic metal complex such as MgN″2 (N″ = N(SiMe3)2) forms a uranyl(V) complex in which both oxo-groups are Mg functionalized as a result of Mg-N bond homolysis. In contrast, reactions with the less Lewis acidic complex [Zn(N″)Cl] favor the formation of weaker U-O-Zn dative interactions, leading to reductive silylation of the uranyl oxo-group in preference to metalation. Spectroscopic, crystallographic, and computational analysis of these reactions and of oxo-metalated products isolated by other routes have allowed us to propose mechanisms that account for pathways to metalation or silylation of the exo-oxo-group.

  7. Assessment of CE-ICP/MS hyphenation for the study of uranyl/protein interactions.

    PubMed

    Huynh, Thi-Ngoc Suong; Bourgeois, Damien; Basset, Christian; Vidaud, Claude; Hagège, Agnès

    2015-06-01

    Identification of uranyl transport proteins is key to develop efficient detoxification approaches. Therefore, analytical approaches have to be developed to cope with the complexity of biological media and allow the analysis of metal speciation. CE-ICP/MS was used to combine the less-intrusive character and high separation efficiency of CE with the sensitive detection of ICP/MS. The method was based on the incubation of samples with uranyl prior to the separation. Electrophoretic buffers were compared to select a 10 mM Tris to 15 mM NaCl buffer, which enabled analyses at pH 7.4 and limited dissociation. This method was applied to the analysis of a serum. Two main fractions were observed. By comparison with synthetic mixtures of proteins, the first one was attributed to fetuin and in a lesser extent to HSA, and the second one to uranyl unbound to proteins. The analysis showed that fetuin was likely to be the main target of uranyl. CE-ICP/MS was also used to investigate the behavior of the fetuin-uranyl complex, in the presence of carbonate, an abundant complexing agent of uranyl in blood. This method enabled association constants determination, suggesting the occurrence of both FETUA(UO2(2+)) and FETUA(UO2(2+))(CO3(2-)) complexes, depending on the carbonate concentration. PMID:25630637

  8. Hydrothermal Crystallization of Uranyl Coordination Polymers Involving an Imidazolium Dicarboxylate Ligand: Effect of pH on the Nuclearity of Uranyl-Centered Subunits.

    PubMed

    Martin, Nicolas P; Falaise, Clément; Volkringer, Christophe; Henry, Natacha; Farger, Pierre; Falk, Camille; Delahaye, Emilie; Rabu, Pierre; Loiseau, Thierry

    2016-09-01

    Four uranyl-bearing coordination polymers (1-4) have been hydrothermally synthesized in the presence of the zwitterionic 1,3-bis(carboxymethyl)imidazolium (= imdc) anion as organic linkers after reaction at 150 °C. At low pH (0.8-3.1), the form 1 ((UO2)2(imdc)2(ox)·3H2O; ox stands for oxalate group) has been identified. Its crystal structure (XRD analysis) consists of the 8-fold-coordinated uranyl centers linked to each other through the imdc ligand together with oxalate species coming from the partial decomposition of the imdc molecule. The resulting structure is based on one-dimensional infinite ribbons intercalated by free water molecules. By adding NaOH solution, a second form 2 is observed for pH 1.9-3.9 but in a mixture with phase 1. The pure phase of 2 is obtained after a hydrothermal treatment at 120 °C. It corresponds to a double-layered network (UO2(imdc)2) composed of 7-fold-coordinated uranyl cations linked via the imdc ligands. In the same pH range, a third phase ((UO2)3O2(H2O)(imdc)·H2O, 3) is formed: it is composed of hexanuclear units of 7-fold- and 8-fold-coordinated uranyl cations, connected via the imdc molecules in a layered assembly. At higher pH, the chain-like solid (UO2)3O(OH)3(imdc)·2H2O (4) is observed and composed of the infinite edge-sharing uranyl-centered pentagonal bipyramidal polyhedra. As a function of pH, uranyl nuclearity increases from discrete 8- or 7-fold uranyl centers (1, 2) to hexanuclear bricks (3) and then infinite chains in 4 (built up from the hexameric fragments found in 3). This observation emphasized the influence of the hydrolysis reaction occurring between uranyl centers. The compounds have been further characterized by thermogravimetric analysis, infrared, and luminescence spectroscopy. PMID:27509393

  9. Modulation of the Structure and Properties of Uranyl Ion Coordination Polymers Derived from 1,3,5-Benzenetriacetate by Incorporation of Ag(I) or Pb(II).

    PubMed

    Thuéry, Pierre; Harrowfield, Jack

    2016-07-01

    Reaction of uranyl nitrate with 1,3,5-benzenetriacetic acid (H3BTA) in the presence of additional species, either organic bases or their conjugate acids or metal cations, has provided 12 new crystalline complexes, all but one obtained under solvo-hydrothermal conditions. The complexes [C(NH2)3][UO2(BTA)]·H2O (1) and [H2NMe2][UO2(BTA)] (2) crystallize as one- or two-dimensional (1D or 2D) assemblies, respectively, both with uranyl tris-chelation by carboxylate groups and hydrogen-bonded counterions but different ligand conformations. One of the bound carboxylate units is replaced by chelating 1,10-phenanthroline (phen) or 3,4,7,8-tetramethyl-1,10-phenanthroline (Me4phen) in the complexes [(UO2)3(BTA)2(phen)3]·4H2O (3) and [(UO2)3(BTA)2(Me4phen)3]·NMP·3H2O (4) (NMP = N-methyl-2-pyrrolidone), which are a 2D network with honeycomb topology and a 1D polymer, respectively. With silver(I) cations, [UO2Ag(BTA)] (5), a three-dimensional (3D) framework in which the ligand assumes various chelating/bridging coordination modes, and the aromatic ring is involved in Ag(I) bonding, is obtained. A series of seven heterometallic complexes results when lead(II) cations and N-chelating molecules are both present. The complexes [UO2Pb(BTA)(NO3)(bipy)] (6) and [UO2Pb2(BTA)2(bipy)2]·3H2O (7), where bipy is 2,2'-bipyridine, crystallize from the one solution, as 1D and 2D assemblies, respectively. The two 1D coordination polymers [UO2Pb(BTA)(HCOO)(phen)] (8 and 9), again obtained from the one synthesis, provide an example of coordination isomerism, with the formate anion bound either to lead(II) or to uranyl cations. Another 2D architecture is found in [(UO2)2Pb2(BTA)2(HBTA)(H2O)2(phen)2]·2H2O (10), which provides a possible example of a Pb-oxo(uranyl) "cation-cation" interaction. While [UO2Pb(BTA)(HCOO)0.5(NO3)0.5(Me2phen)] (11), where Me2phen is 5,6-dimethyl-1,10-phenanthroline, is a 1D assembly close to those in 6 and 8, [UO2Pb2(BTA)2(Me4phen)2] (12), obtained together with

  10. Modulation of the Structure and Properties of Uranyl Ion Coordination Polymers Derived from 1,3,5-Benzenetriacetate by Incorporation of Ag(I) or Pb(II).

    PubMed

    Thuéry, Pierre; Harrowfield, Jack

    2016-07-01

    Reaction of uranyl nitrate with 1,3,5-benzenetriacetic acid (H3BTA) in the presence of additional species, either organic bases or their conjugate acids or metal cations, has provided 12 new crystalline complexes, all but one obtained under solvo-hydrothermal conditions. The complexes [C(NH2)3][UO2(BTA)]·H2O (1) and [H2NMe2][UO2(BTA)] (2) crystallize as one- or two-dimensional (1D or 2D) assemblies, respectively, both with uranyl tris-chelation by carboxylate groups and hydrogen-bonded counterions but different ligand conformations. One of the bound carboxylate units is replaced by chelating 1,10-phenanthroline (phen) or 3,4,7,8-tetramethyl-1,10-phenanthroline (Me4phen) in the complexes [(UO2)3(BTA)2(phen)3]·4H2O (3) and [(UO2)3(BTA)2(Me4phen)3]·NMP·3H2O (4) (NMP = N-methyl-2-pyrrolidone), which are a 2D network with honeycomb topology and a 1D polymer, respectively. With silver(I) cations, [UO2Ag(BTA)] (5), a three-dimensional (3D) framework in which the ligand assumes various chelating/bridging coordination modes, and the aromatic ring is involved in Ag(I) bonding, is obtained. A series of seven heterometallic complexes results when lead(II) cations and N-chelating molecules are both present. The complexes [UO2Pb(BTA)(NO3)(bipy)] (6) and [UO2Pb2(BTA)2(bipy)2]·3H2O (7), where bipy is 2,2'-bipyridine, crystallize from the one solution, as 1D and 2D assemblies, respectively. The two 1D coordination polymers [UO2Pb(BTA)(HCOO)(phen)] (8 and 9), again obtained from the one synthesis, provide an example of coordination isomerism, with the formate anion bound either to lead(II) or to uranyl cations. Another 2D architecture is found in [(UO2)2Pb2(BTA)2(HBTA)(H2O)2(phen)2]·2H2O (10), which provides a possible example of a Pb-oxo(uranyl) "cation-cation" interaction. While [UO2Pb(BTA)(HCOO)0.5(NO3)0.5(Me2phen)] (11), where Me2phen is 5,6-dimethyl-1,10-phenanthroline, is a 1D assembly close to those in 6 and 8, [UO2Pb2(BTA)2(Me4phen)2] (12), obtained together with

  11. Folic acid deficiency impairs the gill health status associated with the NF-κB, MLCK and Nrf2 signaling pathways in the gills of young grass carp (Ctenopharyngodon idella).

    PubMed

    Shi, Lei; Feng, Lin; Jiang, Wei-Dan; Liu, Yang; Jiang, Jun; Wu, Pei; Zhao, Juan; Kuang, Sheng-Yao; Tang, Ling; Tang, Wu-Neng; Zhang, Yong-An; Zhou, Xiao-Qiu

    2015-11-01

    The aim of this study was to investigate the effect of dietary folic acid on fish growth, the immune and barrier functions of fish gills, and the potential mechanisms of these effects. Young grass carp (Ctenopharyngodon idella) were fed diets containing graded levels of folic acid at 0.10 (basal diet), 0.47, 1.03, 1.48, 1.88 and 3.12 mg kg(-1) diet for 8 weeks. The results showed that acid phosphatase and lysozyme activities and the complement component 3 content in fish gills decreased with folic acid deficiency (P < 0.05). Folic acid deficiency up-regulated liver-expressed antimicrobial peptide 1, interleukin 1β, interleukin 8, tumor necrosis factor α, nuclear factor κB p65, IκB kinase α (IKK-α), IKK-β and IKK-γ gene expression. Folic acid deficiency down-regulated interleukin 10, transforming growth factor β, IκB and target of rapamycin gene expression in fish gills (P < 0.05). These results showed that limited folic acid decreased fish gill immune status. Furthermore, folic acid deficiency down-regulated claudin-b, claudin-c, claudin-3, occludin and zonula occludens 1 gene expression, whereas folic acid deficiency up-regulated claudin-12, claudin-15, myosin light chain kinase and p38 mitogen activated protein kinase gene expression in fish gills (P < 0.05). These results suggested that folic acid deficiency disrupted tight junction-mediated fish gill barrier function. Additionally, folic acid deficiency increased the content of reactive oxygen species, protein carbonyl and malondialdehyde (MDA); Mn superoxide dismutase activity and gene expression; and Kelch-like-ECH-associated protein 1a (Keap1a) and Keap1b gene expression (P < 0.05). Conversely, folic acid deficiency decreased Cu/Zn superoxide dismutase, catalase, glutathione peroxidase, glutathione s-transferases and glutathione reductase activities and gene expression as well as NF-E2-related factor 2 gene expression in fish gills (P < 0.05). All of these results indicated that folic acid

  12. A spectroscopic study of uranyl-cytochrome b5/cytochrome c interactions

    NASA Astrophysics Data System (ADS)

    Sun, Mei-Hui; Liu, Shuang-Quan; Du, Ke-Jie; Nie, Chang-Ming; Lin, Ying-Wu

    2014-01-01

    Uranium is harmful to human health due to its radiation damage and the ability of uranyl ion (UO22+) to interact with various proteins and disturb their biological functions. Cytochrome b5 (cyt b5) is a highly negatively charged heme protein and plays a key role in mediating cytochrome c (cyt c) signaling in apoptosis by forming a dynamic cyt b5-cyt c complex. In previous molecular modeling study in combination with UV-Vis studies, we found that UO22+ is capable of binding to cyt b5 at surface residues, Glu37 and Glu43. In this study, we further investigated the structural consequences of cyt b5 and cyt c, as well as cyt b5-cyt c complex, upon uranyl binding, by fluorescence spectroscopic and circular dichroism techniques. Moreover, we proposed a uranyl binding site for cyt c at surface residues, Glu66 and Glu69, by performing a molecular modeling study. It was shown that uranyl binds to cyt b5 (KD = 10 μM), cyt c (KD = 87 μM), and cyt b5-cyt c complex (KD = 30 μM) with a different affinity, which slightly alters the protein conformation and disturbs the interaction of cyt b5-cyt c complex. Additionally, we investigated the functional consequences of uranyl binding to the protein surface, which decreases the inherent peroxidase activity of cyt c. The information of uranyl-cyt b5/cyt c interactions gained in this study likely provides a clue for the mechanism of uranyl toxicity.

  13. Uranyl photoprobing of a four-way DNA junction: evidence for specific metal ion binding.

    PubMed Central

    Møllegaard, N E; Murchie, A I; Lilley, D M; Nielsen, P E

    1994-01-01

    Metal ions are very important in mediating the folding of nucleic acids, as exemplified by the folding of the four-way DNA junction into the stacked X-conformation. Uranyl ion-mediated photocleavage provides a method for the localization of high-affinity ion binding sites in nucleic acids, and we have applied this to the four-way DNA junction. We have made the following observations. (i) Uranyl ions (UO2(2+)) suppressed the reactivity of junction thymine bases against attack by osmium tetroxide, indicating that the uranyl ion induces folding of the junction into a stacked conformation. (ii) DNA located immediately at the point of strand exchange on the two exchanging strands was hypersensitive to uranyl photocleavage. The relative hypersensitivity was considerably accentuated when the photocleavage was carried out in the presence of citrate ions. This suggests the presence of a tight binding site for the uranyl ion in the junction. (iii) The same positions were significantly protected from uranyl cleavage by the presence of hexamminecobalt (III) or spermidine. These ions are known to induce the folded conformation of the four-way junction with high efficiency, suggesting a direct competition between the ions. By contrast, magnesium ions failed to generate a similar protection against photocleavage. These results suggest that the uranyl, hexamminecobalt (III) and spermidine ions compete for the same high affinity binding site on the junction. This site is located at the centre of the junction, at the point where the exchanging strands pass between the stacked helices. We believe that we have observed the first known example of a metal ion 'footprint' on a folded nucleic acid structure. Images PMID:8156988

  14. Thermochemical nitrate destruction

    DOEpatents

    Cox, J.L.; Hallen, R.T.; Lilga, M.A.

    1992-06-02

    A method is disclosed for denitrification of nitrates and nitrites present in aqueous waste streams. The method comprises the steps of (1) identifying the concentration nitrates and nitrites present in a waste stream, (2) causing formate to be present in the waste stream, (3) heating the mixture to a predetermined reaction temperature from about 200 C to about 600 C, and (4) holding the mixture and accumulating products at heated and pressurized conditions for a residence time, thereby resulting in nitrogen and carbon dioxide gas, and hydroxides, and reducing the level of nitrates and nitrites to below drinking water standards.

  15. Determination of intracellular nitrate.

    PubMed Central

    Romero, J M; Lara, C; Guerrero, M G

    1989-01-01

    A sensitive procedure has been developed for the determination of intracellular nitrate. The method includes: (i) preparation of cell lysates in 2 M-H3PO4 after separation of cells from the outer medium by rapid centrifugation through a layer of silicone oil, and (ii) subsequent nitrate analysis by ion-exchange h.p.l.c. with, as mobile phase, a solution containing 50 mM-H3PO4 and 2% (v/v) tetrahydrofuran, adjusted to pH 1.9 with NaOH. The determination of nitrate is subjected to interference by chloride and sulphate when present in the samples at high concentrations. Nitrite also interferes, but it is easily eliminated by treatment of the samples with sulphamic acid. The method has been successfully applied to the study of nitrate transport in the unicellular cyanobacterium Anacystis nidulans. PMID:2497740

  16. Oxygen exchange in uranyl hydroxide via two "nonclassical" ions.

    PubMed

    Bühl, Michael; Schreckenbach, Georg

    2010-04-19

    A recently proposed pathway for the scrambling of axial (uranyl) and equatorial O atoms in [UO(2)(OH)(4)](2-) (1) is refined using Car-Parrinello molecular dynamics (CPMD) simulations in an explicit solvent (water) and with model counterions (NH(4)(+)). According to constrained CPMD/BLYP simulations and thermodynamic integration, 1 can be deprotonated to [UO(3)(OH)(3)](3-) with a T-shaped UO(3) group (DeltaA = 7.1 kcal/mol), which in turn can undergo a solvent-assisted proton transfer via a cis-[UO(2)(OH)(4)](2-).OH(-) complex and a total overall barrier of DeltaA(double dagger) = 12.5 kcal/mol. According to computed relative energies of trans- and cis-[UO(2)(OH)(4)](2-) in the gas phase and in a polarizable continuum, "pure" functionals such as BLYP underestimate this overall barrier somewhat, and estimates of DeltaA(double dagger) approximately 16 and 17 kcal/mol are obtained at the B3LYP and CCSD(T) levels, respectively, in excellent agreement with the experiment. PMID:20334349

  17. Protein tyrosine nitration

    PubMed Central

    Chaki, Mounira; Leterrier, Marina; Barroso, Juan B

    2009-01-01

    Nitric oxide metabolism in plant cells has a relative short history. Nitration is a chemical process which consists of introducing a nitro group (-NO2) into a chemical compound. in biological systems, this process has been found in different molecules such as proteins, lipids and nucleic acids that can affect its function. This mini-review offers an overview of this process with special emphasis on protein tyrosine nitration in plants and its involvement in the process of nitrosative stress. PMID:19826215

  18. A Mixed-Method Study to Determine the Benefits of Periconceptional Folic Acid Supplementation and Effects of Folic Acid Deficiency in Mothers on Birth Outcomes

    PubMed Central

    Murthy, Gudlavalleti Venkata S; Kolli, Sunanda Reddy; Neogi, Sutapa B; Singh, Samiksha; John, Neena; N., Srinivas; Ramani, Sudha; Shamanna, BR; Doyle, Pat; Kinra, Sanjay; Ness, Andy; Pallepogula, Dinesh Raj; Pant, Hira B; Babbar, Smiksha; Reddy, Raghunath; Singh, Rachna

    2016-01-01

    Background Evidence from high income countries shows mothers who are supplemented with folic acid in their periconceptional period and early pregnancy have significantly reduced adverse outcomes like birth defects. However, in India there is a paucity of data on association of birth defects and folic acid supplementation. We identified a few important questions to be answered using separate scientific methods and then planned to triangulate the information. Objective In this paper, we describe the protocol of our study that aims to determine the association of folic acid and pregnancy outcomes like neural tube defects (NTDs) and orofacial clefts (OFCs). We decided to fill the gaps in knowledge from India to determine public health consequences of folic acid deficiency and factors influencing dietary and periconceptional consumption of folic acid. Methods The proposed study will be carried out in five stages and will examine the questions related to folic acid deficiency across selected locations in South and North India. The study will be carried out over a period of 4 years through the hierarchical evidence-based approach. At first a systematic review was conducted to pool the current birth prevalence of NTDs and orofacial clefts OFCs in India. To investigate the population prevalence, we plan to use the key informant method to determine prevalence of NTDs and OFCs. To determine the normal serum estimates of folic acid, iron, and vitamin B12 among Indian women (15-35 years), we will conduct a population-based, cross-sectional study. We will further strengthen the evidence of association between OFCs and folic acid by conducting a hospital-based, case-control study across three locations of India. Lastly, using qualitative methods we will understand community and health workers perspective on factors that decide the intake of folic acid supplements. Results This study will provide evidence on the community prevalence of birth defects and prevalence folic acid and

  19. Thermochemical nitrate reduction

    SciTech Connect

    Cox, J.L.; Lilga, M.A.; Hallen, R.T.

    1992-09-01

    A series of preliminary experiments was conducted directed at thermochemically converting nitrate to nitrogen and water. Nitrates are a major constituent of the waste stored in the underground tanks on the Hanford Site, and the characteristics and effects of nitrate compounds on stabilization techniques must be considered before permanent disposal operations begin. For the thermochemical reduction experiments, six reducing agents (ammonia, formate, urea, glucose, methane, and hydrogen) were mixed separately with {approximately}3 wt% NO{sub 3}{sup {minus}} solutions in a buffered aqueous solution at high pH (13); ammonia and formate were also mixed at low pH (4). Reactions were conducted in an aqueous solution in a batch reactor at temperatures of 200{degrees}C to 350{degrees}C and pressures of 600 to 2800 psig. Both gas and liquid samples were analyzed. The specific components analyzed were nitrate, nitrite, nitrous oxide, nitrogen, and ammonia. Results of experimental runs showed the following order of nitrate reduction of the six reducing agents in basic solution: formate > glucose > urea > hydrogen > ammonia {approx} methane. Airnmonia was more effective under acidic conditions than basic conditions. Formate was also effective under acidic conditions. A more thorough, fundamental study appears warranted to provide additional data on the mechanism of nitrate reduction. Furthermore, an expanded data base and engineering feasibility study could be used to evaluate conversion conditions for promising reducing agents in more detail and identify new reducing agents with improved performance characteristics.

  20. Determination of trace uranyl ion by thermoresponsive porphyrin-terminated polymeric sensor.

    PubMed

    Shu, Xiaowen; Wang, Yingjie; Zhang, Shuang; Huang, Li; Wang, Shuao; Hua, Daoben

    2015-01-01

    Uranyl ion exists at trace levels in the environment and can cause severe adverse effects to human health. Therefore, it is desirable to develop analytical methods that can determine the trace uranyl ion in aqueous medium. We report here a new method using a thermo-responsive polymeric fluorescent sensor. Specifically, 5,10,15,20-tetrakis(4-carboxyphenyl)-porphyrin terminated poly(N-isopropylacrylamide) (TCPP-PNIPAM) was synthesized by controlled free radical polymerization for the detection of uranyl ion. The maximum fluorescence intensity at ~ 658 nm of TCPP-PNIPAM increases with molecular weights and is also closely related to the temperature. The polymeric sensor is sensitive to pH (1.0 ~ 5.0) with a fast responsive time (~ 3 min). Under optimized experimental conditions, the sensor exhibits a stable response for uranyl ion with high selectivity over a concentration range from 1.0 × 10(-3) to 1.0 × 10(-7)mol/L. For the trace uranyl ion (such as 1.0 × 10(-8) or 10(-9)mol/L), the determination could be successfully achieved after concentrating 100 times by centrifugation above 32°C. The properties enable the polymeric sensor to have great potential for environmental application. PMID:25281093

  1. Binding constant determination of uranyl-citrate complex by ACE using a multi-injection method.

    PubMed

    Zhang, Yiding; Li, Linnan; Huang, Hexiang; Xu, Linnan; Li, Ze; Bai, Yu; Liu, Huwei

    2015-04-01

    The binding constant determination of uranyl with small-molecule ligands such as citric acid could provide fundamental knowledge for a better understanding of the study of uranyl complexation, which is of considerable importance for multiple purposes. In this work, the binding constant of uranyl-citrate complex was determined by ACE. Besides the common single-injection method, a multi-injection method to measure the electrophoretic mobility was also applied. The BGEs used contained HClO4 and NaClO4 , with a pH of 1.98 ± 0.02 and ionic strength of 0.050 mol/L, then citric acid was added to reach different concentrations. The electrophoretic mobilities of the uranyl-citrate complex measured by both of the two methods were consistent, and then the binding constant was calculated by nonlinear fitting assuming that the reaction had a 1:1 stoichiometry and the complex was [(UO2 )(Cit)](-) . The binding constant obtained by the multi-injection method was log K = 9.68 ± 0.07, and that obtained by the single-injection method was log K = 9.73 ± 0.02. The results provided additional knowledge of the uranyl-citrate system, and they demonstrated that compared with other methods, ACE using the multi-injection method could be an efficient, fast, and simple way to determine electrophoretic mobilities and to calculate binding constants. PMID:25598434

  2. Uranyl adsorption and surface speciation at the imogolite-water interface: Self-consistent spectroscopic and surface complexation models

    USGS Publications Warehouse

    Arai, Y.; McBeath, M.; Bargar, J.R.; Joye, J.; Davis, J.A.

    2006-01-01

    Macro- and molecular-scale knowledge of uranyl (U(VI)) partitioning reactions with soil/sediment mineral components is important in predicting U(VI) transport processes in the vadose zone and aquifers. In this study, U(VI) reactivity and surface speciation on a poorly crystalline aluminosilicate mineral, synthetic imogolite, were investigated using batch adsorption experiments, X-ray absorption spectroscopy (XAS), and surface complexation modeling. U(VI) uptake on imogolite surfaces was greatest at pH ???7-8 (I = 0.1 M NaNO3 solution, suspension density = 0.4 g/L [U(VI)]i = 0.01-30 ??M, equilibration with air). Uranyl uptake decreased with increasing sodium nitrate concentration in the range from 0.02 to 0.5 M. XAS analyses show that two U(VI) inner-sphere (bidentate mononuclear coordination on outer-wall aluminol groups) and one outer-sphere surface species are present on the imogolite surface, and the distribution of the surface species is pH dependent. At pH 8.8, bis-carbonato inner-sphere and tris-carbonato outer-sphere surface species are present. At pH 7, bis- and non-carbonato inner-sphere surface species co-exist, and the fraction of bis-carbonato species increases slightly with increasing I (0.1-0.5 M). At pH 5.3, U(VI) non-carbonato bidentate mononuclear surface species predominate (69%). A triple layer surface complexation model was developed with surface species that are consistent with the XAS analyses and macroscopic adsorption data. The proton stoichiometry of surface reactions was determined from both the pH dependence of U(VI) adsorption data in pH regions of surface species predominance and from bond-valence calculations. The bis-carbonato species required a distribution of surface charge between the surface and ?? charge planes in order to be consistent with both the spectroscopic and macroscopic adsorption data. This research indicates that U(VI)-carbonato ternary species on poorly crystalline aluminosilicate mineral surfaces may be important in

  3. Intestinal absorption, liver uptake, and excretion of /sup 3/H-folic acid in folic acid-deficient, alcohol-consuming nonhuman primates

    SciTech Connect

    Blocker, D.E.; Thenen, S.W.

    1987-09-01

    Nonhuman primates fed folic acid-deficient diets +/- 30% kcal ethanol were used to determine alcohol effects on megaloblastic anemia development and folate bioavailability. Lower hemoglobin (Hb) and red blood cell (RBC) counts and higher mean corpuscular volume (MCV) occurred after 13 wk in alcohol-fed monkeys, later in controls. Plasma, RBC, and liver folate declined and urinary formiminoglutamic acid (FIGLU) was elevated in both groups with FIGLU increasing more among alcohol-fed monkeys at 38 wk. After 40 wk, the bioavailability of oral /sup 3/H-folic acid was investigated and showed increased fecal and reduced urinary tritium excretion in alcohol-fed monkeys compared with controls while plasma uptake and liver and whole body tritium retention were similar in both groups. These observations demonstrate that chronic alcohol consumption impairs folate coenzymes, accelerates appearance of hematologic indices of megaloblastic anemia, and causes possible malabsorption of enterohepatically circulated folates in folate deficiency even when other essential nutrients are provided.

  4. In-Depth Dissection of the P133R Mutation in Steroid 5β-Reductase (AKR1D1): A Molecular Basis of Bile Acid Deficiency.

    PubMed

    Chen, Mo; Jin, Yi; Penning, Trevor M

    2015-10-20

    Human steroid-5β-reductase (aldo-keto reductase 1D1, AKR1D1) stereospecifically reduces Δ(4)-3-ketosteroids to 5β-dihydrosteroids and is essential for steroid hormone metabolism and bile acid biosynthesis. Genetic defects in AKR1D1 cause bile acid deficiency that leads to life threatening neonatal hepatitis and cholestasis. The disease-associated P133R mutation caused significant decreases in catalytic efficiency with both the representative steroid (cortisone) and the bile acid precursor (7α-hydroxycholest-4-en-3-one) substrates. Pro133 is a second shell residue to the steroid binding channel and is distal to both the cofactor binding site and the catalytic center. Strikingly, the P133R mutation caused over a 40-fold increase in Kd values for the NADP(H) cofactors and increased the rate of release of NADP(+) from the enzyme by 2 orders of magnitude when compared to the wild type enzyme. By contrast the effect of the mutation on Kd values for steroids were 10-fold or less. The reduced affinity for the cofactor suggests that the mutant exists largely in the less stable cofactor-free form in the cell. Using stopped-flow spectroscopy, a significant reduction in the rate of the chemical step was observed in multiple turnover reactions catalyzed by the P133R mutant, possibly due to the altered position of NADPH. Thus, impaired NADPH binding and hydride transfer is the molecular basis for bile acid deficiency in patients with the P133R mutation. Results revealed that optimal cofactor binding is vulnerable to distant structural perturbation, which may apply to other disease-associated mutations in AKR1D1, all of which occur at conserved residues and are unstable.

  5. Perinatal n-3 fatty acid deficiency selectively reduces myo-inositol levels in the adult rat PFC: an in vivo 1H-MRS study*s⃞

    PubMed Central

    McNamara, Robert K.; Able, Jessica; Jandacek, Ronald; Rider, Therese; Tso, Patrick; Lindquist, Diana M.

    2009-01-01

    To investigate the effects of omega-3 fatty acid deficiency on phosphatidylinositol signaling in brain, myo-inositol (mI) concentrations were determined in the prefrontal cortex (PFC) of omega-3 fatty acid deficient rats by in vivo proton magnetic resonance spectroscopy (1H-MRS). To generate graded deficits in PFC docosahexaenoic acid (22:6n-3) (DHA) composition, perinatal and postweaning α-linolenic acid (18:3n-3) (ALA) deficiency models were used. Adult male rats were scanned in a 7T Bruker Biospec system and a 1H-MRS spectrum acquired from the bilateral medial PFC. Rats were then challenged with SKF83959, a selective agonist at phosphoinositide (PI)-coupled dopamine D1 receptors. Postmortem PFC fatty acid composition was determined by gas chromatography. Relative to controls, PFC DHA composition was significantly reduced in adult postweaning (−27%) and perinatal (−65%) ALA-deficiency groups. Basal PFC mI concentrations were significantly reduced in the perinatal deficiency group (−21%, P = 0.001), but not in the postweaning deficiency group (−1%, P = 0.86). Among all rats, DHA composition was positively correlated with mI concentrations and the mI/creatine (Cr) ratio. SKF83959 challenge significantly increased mI concentrations only in the perinatal deficiency group (+16%, P = 0.02). These data demonstrate that perinatal deficits in cortical DHA accrual significantly and selectively reduce mI concentrations and augment receptor-generated mI synthesis. PMID:18802197

  6. Designing novel materials through functionalization of carbon nanotubes for application in nuclear waste management: speciation of uranyl.

    PubMed

    Sundararajan, Mahesh; Ghosh, Swapan K

    2011-06-23

    Understanding the behavior of radioactive nuclide elements in different environmental conditions is an active area of research. In this work, we have investigated the possible interaction mechanism between carbon nanotubes and uranyl using density functional theory. It is shown that functionalized carbon nanotubes can be used to bind uranyl ions much more efficiently as compared to their unfunctionalized counterpart. The uranyl binding energies are sensitive to the nature of the functional groups rather than the carbon nanotube itself. The binding takes place preferably at the functionalized sites, although pH could determine the strength of uranyl binding. Our predicted results correlate well with the recent experimental uranyl sorption studies on carbon nanotubes. These finding are new and can open up a new era for actinide speciation and separation chemistry using carbon nanotubes.

  7. Car-Parrinello molecular dynamics study of the uranyl behaviour at the gibbsite/water interface

    NASA Astrophysics Data System (ADS)

    Lectez, Sébastien; Roques, Jérôme; Salanne, Mathieu; Simoni, Eric

    2012-10-01

    The uranyl cation UO22+ adsorption on the basal face of gibbsite is studied via Car-Parrinello molecular dynamics. In a first step, we study the water sorption on a gibbsite surface. Three different sorption modes are observed and their hydrogen bond patterns are, respectively, characterized. Then we investigate the sorption properties of an uranyl cation, in the presence of water. In order to take into account the protonation state of the (001) gibbsite face, both a neutral (001) face and a locally deprotonated (001) face are modeled. In the first case, three adsorbed uranyl complexes (1 outer sphere and 2 inner spheres) with similar stabilities are identified. In the second case, when the gibbsite face is locally deprotonated, two adsorbed complexes (1 inner sphere and 1 outer one) are characterized. The inner sphere complex appears to be the most strongly linked to the gibbsite face.

  8. Molecular simulation of the diffusion of uranyl carbonate species in aqueous solution

    NASA Astrophysics Data System (ADS)

    Kerisit, Sebastien; Liu, Chongxuan

    2010-09-01

    Potential-based molecular dynamics simulations of aqueous uranyl carbonate species (M xUO 2(CO 3) y2+2x-2y with M = Mg, Ca, or Sr) were carried out to gain molecular-level insight into the hydration properties of these species. The simulation results were used to estimate the self-diffusion coefficients of these uranyl carbonate species, which often dominate uranyl speciation in groundwater systems. The diffusion coefficients obtained for the monoatomic alkaline-earth cations and polyatomic ions (uranyl, carbonate, and uranyl tri-carbonate) were compared with those calculated from the Stokes-Einstein (SE) equation and its variant formulation by Impey et al. (1983). Our results show that the equation of Impey et al. (1983), originally formulated for monovalent monoatomic ions, can be extended to divalent monoatomic ions, with some success in reproducing the absolute values and the overall trend determined from the molecular dynamics simulations, but not to polyatomic ions, for which the hydration shell is not spherically symmetrical. Despite the quantitative failure of both SE formulations, a plot of the diffusion coefficients of the uranyl carbonate complexes as a function of the inverse of the equivalent spherical radius showed that a general linear dependence is observed for these complexes as expected from the SE equation. The nature of the alkaline-earth cation in the uranyl carbonate complexes was not found to have a significant effect on the ion's diffusion coefficient, which suggests that the use of a single diffusion coefficient for different alkaline-earth uranyl carbonate complexes in microscopic diffusion models is appropriate. The potential model reproduced well published quantum mechanical and experimental data of UO(CO)32x-4 and of the individual constituent ions, and therefore is expected to offer reliable predictions of the structure of magnesium and strontium uranyl carbonate aqueous species, for which there is no structural data available to date

  9. Iron (II) sorption to mineral surfaces in uranyl and silicate rich media

    SciTech Connect

    Tyler A. Sullens; Cynthia-May S. Gong; Kenneth R. Czerwinski

    2006-01-01

    Abstract - The unique composition of the Yucca Mountain repository site, which contains large concentrations of silicate in an oxidative environment, has required extensive research into compound formation involving uranium and iron(II) under such conditions. The possibility of uranium leakage from within the containment vessels into the near-field ground water, as well as iron leaching from the vessel itself, necessitates study of the individual contributions of these elements for compound formation. By mimicking the known silicate concentration found in surrounding ground water and varying concentrations of both uranyl and iron(II), subsequent precipitation of uranyl silicate phases has shown evidence of iron(II) sorption to the available sites on the mineral surface. The mineralization seems to be driven by the formation of uranyl silicate, in contrast to iron(III)-control of precipitation in the oxidated system. We present characterization of this system using ICP-AES/MS, EDAX, XRD, and single-crystal X-ray diffraction.

  10. Selectivity in ligand binding to uranyl compounds: A synthetic, structural, thermodynamic and computational study

    SciTech Connect

    Arnold, John

    2015-01-21

    The uranyl cation (UO₂²⁺) is the most abundant form of uranium on the planet. It is estimated that 4.5 billion tons of uranium in this form exist in sea water. The ability to bind and extract the uranyl cation from aqueous solution while separating it from other elements would provide a limitless source of nuclear fuel. A large body of research concerns the selective recognition and extraction of uranyl. A stable molecule, the cation has a linear O=U=O geometry. The short U-O bonds (1.78 Å) arise from the combination of uranium 5f/6d and oxygen 2p orbitals. Due to the oxygen moieties being multiply bonded, these sites were not thought to be basic enough for Lewis acidic coordination to be a viable approach to sequestration. The goal of this research is thus to broaden the coordination chemistry of the uranyl ion by studying new ligand systems via synthetic, structural, thermodynamic and computational methods. It is anticipated that this fundamental science will find use beyond actinide separation technologies in areas such as nuclear waste remediation and nuclear materials. The focus of this study is to synthesize uranyl complexes incorporating amidinate and guanidinate ligands. Both synthetic and computational methods are used to investigate novel equatorial ligand coordination and how this affects the basicity of the oxo ligands. Such an understanding will later apply to designing ligands incorporating functionalities that can bind uranyl both equatorially and axially for highly selective sequestration. Efficient and durable chromatography supports for lanthanide separation will be generated by (1) identifying robust peptoid-based ligands capable of binding different lanthanides with variable affinities, and (2) developing practical synthetic methods for the attachment of these ligands to Dowex ion exchange resins.

  11. Uranyl-copper(II) heterometallic oxalate complexes: coordination polymers and frameworks.

    PubMed

    Thuéry, Pierre; Rivière, Eric

    2013-08-01

    Five oxalate complexes containing both uranyl and copper(II) ions and 2,2′-bipyridine (bipy), 2,2′-bipyrimidine (bipym) or 1,10-phenanthroline (phen) as co-ligands have been synthesized under hydrothermal conditions and their crystal structures were determined. [UO2Cu(C2O4)(NO3)2(bipy)(H2O)] (1) is a molecular complex in which the two cations are connected by the bis-chelating oxalate. A one-dimensional uranyl oxalate ribbon is formed in [UO2Cu(C2O4)2(bipym)(H2O)] (2), with uranyl ions bound to two chelating anions and to a third, monodentate oxalate which holds the decorating [Cu(bipym)(H2O)]2+ groups. Complex [(UO2)2Cu2(C2O4)2(bipym)3(OH)2]·2NO3 (3) is a two-dimensional assembly in which uranyl oxalate chains are linked to one another by [Cu2(bipym)3]4+ dinuclear units through bridging hydroxide ions. Finally, [UO2Cu(C2O4)2(bipy)] (4) and [UO2Cu(C2O4)2(phen)] (5) display identical three-dimensional arrangements containing uranyl oxalate sheets connected to one another by copper oxalate dinuclear units. The magnetic properties of compounds 2 and 4 have been investigated. Weak inter-chain antiferromagnetic interactions between copper(II) atoms are present in 2, while 4 displays strong oxalate-mediated antiferromagnetic exchange (J = -335 cm(-1)). These complexes are the first uranyl-d block metal oxalate complexes to be reported. PMID:23760346

  12. Bonding and charge transfer in nitrogen-donor uranyl complexes: insights from NEXAFS spectra.

    PubMed

    Pemmaraju, C D; Copping, Roy; Wang, Shuao; Janousch, Markus; Teat, Simon J; Tyliszcak, Tolek; Canning, Andrew; Shuh, David K; Prendergast, David

    2014-11-01

    We investigate the electronic structure of three newly synthesized nitrogen-donor uranyl complexes [(UO2)(H2bbp)Cl2], [(UO)2(Hbbp)(Py)Cl], and [(UO2)(bbp)(Py)2] using a combination of near-edge X-ray absorption fine structure (NEXAFS) spectroscopy experiments and simulations. The complexes studied feature derivatives of the tunable tridentate N-donor ligand 2,6-bis(2-benzimidazyl)pyridine (bbp) and exhibit discrete chemical differences in uranyl coordination. The sensitivity of the N K-edge X-ray absorption spectrum to local bonding and charge transfer is exploited to systematically investigate the evolution of structural as well as electronic properties across the three complexes. A thorough interpretation of the measured experimental spectra is achieved via ab initio NEXAFS simulations based on the eXcited electron and Core-Hole (XCH) approach and enables the assignment of spectral features to electronic transitions on specific absorbing sites. We find that ligand-uranyl bonding leads to a signature blue shift in the N K-edge absorption onset, resulting from charge displacement toward the uranyl, while changes in the equatorial coordination shell of the uranyl lead to more subtle modulations in the spectral features. Theoretical simulations show that the flexible local chemistry at the nonbinding imidazole-N sites of the bbp ligand is also reflected in the NEXAFS spectra and highlights potential synthesis strategies to improve selectivity. In particular, we find that interactions of the bbp ligand with solvent molecules can lead to changes in ligand-uranyl binding geometry while also modulating the K-edge absorption. Our results suggest that NEXAFS spectroscopy combined with first-principles interpretation can offer insights into the coordination chemistry of analogous functionalized conjugated ligands. PMID:25330350

  13. Multispecies diffusion models: A study of uranyl species diffusion

    SciTech Connect

    Liu, Chongxuan; Shang, Jianying; Zachara, John M.

    2011-12-14

    Rigorous numerical description of multi-species diffusion requires coupling of species, charge, and aqueous and surface complexation reactions that collectively affect diffusive fluxes. The applicability of a fully coupled diffusion model is, however, often constrained by the availability of species self-diffusion coefficients, as well as by computational complication for imposing charge conservation. In this study, several diffusion models with variable complexity in charge and species coupling were formulated and compared to describe reactive multi-species diffusion in groundwater. Diffusion of uranyl [U(VI)] species was used as an example in demonstrating the effectiveness of the models in describing multi-species diffusion. Numerical simulations found that a diffusion model with a single, common diffusion coefficient for all species was sufficient to describe multi-species U(VI) diffusion under steady-state condition of major chemical composition, but not under transient chemical conditions. Simulations revealed that a fully coupled diffusion model can be well approximated by a component-based diffusion model, which considers difference in diffusion coefficients between chemical components, but not between the species within each chemical component. This treatment significantly enhanced computational efficiency at the expense of minor charge conservation. The charge balance in the component-based diffusion model can be rigorously enforced, if necessary, by adding an artificial kinetic reaction term induced by the charge separation. The diffusion models were applied to describe U(VI) diffusive mass transfer in intragranular domains in two sediments collected from US Department of Energy's Hanford 300A where intragrain diffusion is a rate-limiting process controlling U(VI) adsorption and desorption. The grain-scale reactive diffusion model was able to describe U(VI) adsorption/desorption kinetics that has been described using a semi-empirical, multi-rate model

  14. Raman spectroscopic study of the uranyl tricarbonate mineral liebigite

    NASA Astrophysics Data System (ADS)

    Frost, Ray L.; Erickson, Kristy L.; Weier, Matt L.; Carmody, Onuma; Čejka, Jiří

    2005-03-01

    Raman spectroscopy at 298 and 77 K has been employed to study the structure of the uranyl tricarbonates liebigite {Ca 2[UO 2(CO 3) 3]11H 2O}. The spectra of the samples are sample dependent and significant differences in the Raman spectra are obtained upon cooling to 77 K. It is proposed that the mineral undergoes a phase change upon cooling. Significant changes in the Raman spectra are observed in the hydroxyl stretching region and in the low wavenumber region. Two Raman bands are observed at 3468 and 3528 cm -1 showing the non-equivalence of the water units in the structure. Obtaining spectra at 77 K enables well resolved bands at 3530, 3501, 3482, 3463, 3443, 3405 and 3364 cm -1. Two well resolved bands at 1087 and 1073 cm -1 in the 298 K spectra become bands at 1093, 1076 and 1008 cm -1 in the 77 K spectrum proving the non-equivalence of the carbonate units. This non-equivalence is reflected in the observation of multiple bands in the carbonate bending regions. The (UO 2) 2+ units are characterised by the antisymmetric stretching vibrations at 902, 885 and 873 cm -1 and by the ν2 bending modes at 248 cm -1. Two bands near 820 cm -1 may be assigned to the ν1 (UO 2) 2+ symmetric stretching vibrations, however, a coincidence of these vibrations with the ν2 (CO 3) 2- out-of plane bending vibrations cannot be excluded. The use of Raman spectroscopy enables a better definition of the vibrational modes of liebigite and shows changes in the molecular structure upon reaching 77 K.

  15. Surface reactions kinetics between nanocrystalline magnetite and uranyl.

    PubMed

    Missana, Tiziana; Maffiotte, César; García-Gutiérrez, Miguel

    2003-05-01

    Magnetite is the most important end member of iron corrosion products under reducing environment, which is the condition expected in a deep geological high level radioactive waste disposal. Nanocrystalline magnetite was synthesized in the laboratory and its physicochemical properties were analyzed in detail. The kinetics of the adsorption of U(VI) and the kinetics of the actinide reduction to a lower oxidation state, in presence of the oxide, were studied by means of batch sorption techniques and X-ray photoelectron spectroscopy (XPS) analysis. The results showed that the uranium sorption and reduction processes on the magnetite surface have very fast kinetics (hours), the reduction process being triggered by sorption. XPS measurements showed that the speciation of uranium at the surface does not show significant changes with time (from 1 day to 3 months), as well as the quantity of uranium detected at the surface. The surface speciation depended on the initial pH of the contact solution. Considering that the Eh of equilibrium between magnetite and the solution, under our experimental conditions, is slightly positive (50-100 mV), the uranium reduction would also be thermodynamically possible within the liquid phase. However, the kinetics of reduction in the liquid occur at a much slower rate which, in turn, has to depend on the attainment of the magnetite/solution equilibrium. The decrease of uranium in solution, observed after the uranyl adsorption stage, and particularly at acidic pH, is most probably due to the precipitation of U(IV) formed in the solution.

  16. Removal of uranyl ions by p-hexasulfonated calyx[6]arene acid

    NASA Astrophysics Data System (ADS)

    Popescu (Hoştuc), Ioana-Carmen; Petru, Filip; Humelnicu, Ionel; Mateescu, Marina; Militaru, Ecaterina; Humelnicu, Doina

    2014-10-01

    Radioactive pollution is a significant threat for the people’s health. Therefore highly effective radioactive decontamination methods are required. Ion exchange, biotechnologies and phytoremediation in constructed wetlands have been used as radioactive decontamination technologies for uranium contaminated soil and water remediation. Recently, beside those classical methods the calix[n]arenic derivatives’ utilization as radioactive decontaminators has jogged attention. The present work aims to present the preliminary research results of uranyl ion sorption studies on the p-hexasulfonated calyx[6]arenic acid. The effect of temperature, contact time, sorbent amount and uranyl concentration variation on sorption efficiency was investigated. Isotherm models revealed that the sorption process fit better Langmuir isotherm.

  17. Molecular Simulation of the Diffusion of Uranyl Carbonate Species in Aqueous Solution

    SciTech Connect

    Kerisit, Sebastien N.; Liu, Chongxuan

    2010-09-01

    Molecular dynamics simulations of aqueous uranyl carbonate species were carried out with two different potential models to gain molecular-level insight into the hydration properties of these species and evaluate the ability of the two models to reproduce published ab initio and experimental data. The simulation results were used to estimate the self-diffusion coefficients of uranyl carbonate species that often dominate uranyl speciation in groundwater systems. The first potential model was based on a series of shell models developed by Parker and co-workers (including (DE LEEUW and PARKER, 1998; KERISIT and PARKER, 2004; PAVESE et al., 1996). The second potential model was a rigid-ion model based on the flexible SPC water model (TELEMAN et al., 1987), the uranyl model of Guilbaud and Wipff (GUILBAUD and WIPFF, 1996), and the parameters for the carbonate ion given by Greathouse and co-workers (GREATHOUSE and CYGAN, 2005; GREATHOUSE et al., 2002). Analysis of structural (mean interatomic distances and coordination numbers) and dynamical (water residence times in hydration shell and self-diffusion coefficients) properties showed that, overall, the first potential model performed best when compared to published data, although the only major discrepancy with the second model was a misrepresentation of the configuration adopted by the alkaline-earth uranyl carbonate ions. The diffusion coefficients obtained for the alkaline-earth cations and the uranyl ion were compared with three variants of the Stokes-Einstein (SE) equation and it was found that none of the three SE models were able to reproduce both the absolute values and the overall trend determined from the molecular dynamics simulations. However, as would be expected based on the SE equation, a plot of the diffusion coefficients of the uranyl carbonate complexes as a function of the inverse of the equivalent spherical radius showed a general linear dependence with the two models yielding almost identical gradients

  18. Ascorbic acid deficiency decreases hepatic cytochrome P-450, especially CYP2B1/2B2, and simultaneously induces heme oxygenase-1 gene expression in scurvy-prone ODS rats.

    PubMed

    Kobayashi, Misato; Hoshinaga, Yukiko; Miura, Natsuko; Tokuda, Yuki; Shigeoka, Shigeru; Murai, Atsushi; Horio, Fumihiko

    2014-01-01

    The mechanisms underlying the decrease in hepatic cytochrome P-450 (CYP) content in ascorbic acid deficiency was investigated in scurvy-prone ODS rats. First, male ODS rats were fed a diet containing sufficient ascorbic acid (control) or a diet without ascorbic acid (deficient) for 18 days, with or without the intraperitoneal injection of phenobarbital. Ascorbic acid deficiency decreased hepatic microsomal total CYP content, CYP2B1/2B2 protein, and mitochondrial cytochrome oxidase (COX) complex IV subunit I protein, and simultaneously increased heme oxygenase-1 protein in microsomes and mitochondria. Next, heme oxygenase-1 inducers, that is lipopolysaccharide and hemin, were administered to phenobaribital-treated ODS rats fed sufficient ascorbic acid. The administration of these inducers decreased hepatic microsomal total CYP content, CYP2B1/2B2 protein, and mitochondrial COX complex IV subunit I protein. These results suggested that the stimulation of hepatic heme oxygenase-1 expression by ascorbic acid deficiency caused the decrease in CYP content in liver. PMID:25036135

  19. Ascorbic acid deficiency decreases hepatic cytochrome P-450, especially CYP2B1/2B2, and simultaneously induces heme oxygenase-1 gene expression in scurvy-prone ODS rats.

    PubMed

    Kobayashi, Misato; Hoshinaga, Yukiko; Miura, Natsuko; Tokuda, Yuki; Shigeoka, Shigeru; Murai, Atsushi; Horio, Fumihiko

    2014-01-01

    The mechanisms underlying the decrease in hepatic cytochrome P-450 (CYP) content in ascorbic acid deficiency was investigated in scurvy-prone ODS rats. First, male ODS rats were fed a diet containing sufficient ascorbic acid (control) or a diet without ascorbic acid (deficient) for 18 days, with or without the intraperitoneal injection of phenobarbital. Ascorbic acid deficiency decreased hepatic microsomal total CYP content, CYP2B1/2B2 protein, and mitochondrial cytochrome oxidase (COX) complex IV subunit I protein, and simultaneously increased heme oxygenase-1 protein in microsomes and mitochondria. Next, heme oxygenase-1 inducers, that is lipopolysaccharide and hemin, were administered to phenobaribital-treated ODS rats fed sufficient ascorbic acid. The administration of these inducers decreased hepatic microsomal total CYP content, CYP2B1/2B2 protein, and mitochondrial COX complex IV subunit I protein. These results suggested that the stimulation of hepatic heme oxygenase-1 expression by ascorbic acid deficiency caused the decrease in CYP content in liver.

  20. Multispecies diffusion models: A study of uranyl species diffusion

    NASA Astrophysics Data System (ADS)

    Liu, Chongxuan; Shang, Jianying; Zachara, John M.

    2011-12-01

    Rigorous numerical description of multispecies diffusion requires coupling of species, charge, and aqueous and surface complexation reactions that collectively affect diffusive fluxes. The applicability of a fully coupled diffusion model is, however, often constrained by the availability of species self-diffusion coefficients, as well as by computational complication in imposing charge conservation. In this study, several diffusion models with variable complexity in charge and species coupling were formulated and compared to describe reactive multispecies diffusion in groundwater. Diffusion of uranyl [U(VI)] species was used as an example in demonstrating the effectiveness of the models in describing multispecies diffusion. Numerical simulations found that a diffusion model with a single, common diffusion coefficient for all species was sufficient to describe multispecies U(VI) diffusion under a steady state condition of major chemical composition, but not under transient chemical conditions. Simulations revealed that for multispecies U(VI) diffusion under transient chemical conditions, a fully coupled diffusion model could be well approximated by a component-based diffusion model when the diffusion coefficient for each chemical component was properly selected. The component-based diffusion model considers the difference in diffusion coefficients between chemical components, but not between the species within each chemical component. This treatment significantly enhanced computational efficiency at the expense of minor charge conservation. The charge balance in the component-based diffusion model can be enforced, if necessary, by adding a secondary migration term resulting from model simplification. The effect of ion activity coefficient gradients on multispecies diffusion is also discussed. The diffusion models were applied to describe U(VI) diffusive mass transfer in intragranular domains in two sediments collected from U.S. Department of Energy's Hanford 300A

  1. SEPARATION OF URANYL AND RUTHENIUM VALUES BY THE TRIBUTYL PHOSPHATE EXTRACTION PROCESS

    DOEpatents

    Wilson, A.S.

    1961-05-01

    A process is given for separating uranyl values from ruthenium values contained in an aqueous 3 to 4 M nitric acid solution. After the addition of hydrogen peroxide to obtain a concentration of 0.3 M, the uranium is selectively extracted with kerosene-diluted tributyl phosphate.

  2. Synthesis, structures, and luminescent properties of uranyl terpyridine aromatic carboxylate coordination polymers.

    PubMed

    Thangavelu, Sonia G; Andrews, Michael B; Pope, Simon J A; Cahill, Christopher L

    2013-02-18

    Six novel uranyl terpyridine aromatic carboxylate coordination polymers, [UO(2)(C(6)H(2)O(4)S)(C(15)H(11)N(3))] (1), [UO(2)(C(6)H(2)O(4)S)(C(15)H(10)N(3)Cl)]·H(2)O (2), [UO(2)(C(8)H(4)O(4))(C(15)H(11)N(3))] (3), [UO(2)(C(8)H(4)O(4))(C(15)H(10)N(3)Cl)] (4), [UO(2)(C(12)H(6)O(4))(C(15)H(11)N(3))] (5), and [UO(2)(C(12)H(6)O(4))(C(15)H(10)N(3)Cl)] (6), were synthesized under solvothermal conditions and characterized by single-crystal and powder X-ray diffraction and luminescence and UV-vis spectroscopy. Compounds 1, 2, and 5 crystallize as molecular uranyl dimers, whereas compounds 3, 4, and 6 contain ladder motifs of uranyl centers. Fluorescence spectra of 1-4 show characteristic UO(2)(2+) emission, wherein bathochromic and hypsochromic shifts are noted as a function of organic species. In contrast, uranyl emission from 5 and 6 is quenched by the naphthalene dicarboxylic acid linker molecules.

  3. Molecular dynamics simulations of uranyl adsorption and structure on the basal surface of muscovite

    DOE PAGES

    Teich-McGoldrick, Stephanie L.; Greathouse, Jeffery A.; Cygan, Randall T.

    2014-02-05

    Anthropogenic activities have led to an increased concentration of uranium on the Earth’s surface and potentially in the subsurface with the development of nuclear waste repositories. Uranium is soluble in groundwater, and its mobility is strongly affected by the presence of clay minerals in soils and in subsurface sediments. We use molecular dynamics simulations to probe the adsorption of aqueous uranyl (UO22+) ions onto the basal surface of muscovite, a suitable proxy for typically ultrafine-grained clay phases. Model systems include the competitive adsorption between potassium counterions and aqueous ions (0.1 M and 1.0 M UO2Cl2 , 0.1 M NaCl). Wemore » find that for systems with potassium and uranyl ions present, potassium ions dominate the adsorption phenomenon. Potassium ions adsorb entirely as inner-sphere complexes associated with the ditrigonal cavity of the basal surface. Uranyl ions adsorb in two configurations when it is the only ion species present, and in a single configuration in the presence of potassium. Finally, the majority of adsorbed uranyl ions are tilted less than 45° relative to the muscovite surface, and are associated with the Si4Al2 rings near aluminum substitution sites.« less

  4. Immobilization of selenate by iron in aqueous solution under anoxic conditions and the influence of uranyl

    NASA Astrophysics Data System (ADS)

    Puranen, Anders; Jonsson, Mats; Dähn, Rainer; Cui, Daqing

    2009-08-01

    In proposed high level radioactive waste repositories a large part of the spent nuclear fuel (SNF) canisters are commonly composed of iron. Selenium is present in spent nuclear fuel as a long lived fission product. This study investigates the influence of iron on the uptake of dissolved selenium in the form of selenate and the effect of the presence of dissolved uranyl on the above interaction of selenate. The iron oxide, and selenium speciation on the surfaces was investigated by Raman spectroscopy. X-ray Absorption Spectroscopy was used to determine the oxidation state of the selenium and uranium on the surfaces. Under the simulated groundwater conditions (10 mM NaCl, 2 mM NaHCO 3, <0.1 ppm O 2) the immobilized selenate was found to be reduced to oxidation states close to zero or lower and uranyl was found to be largely reduced to U(IV). The near simultaneous reduction of uranyl was found to greatly enhance the rate of selenate reduction. These findings suggest that the presence of uranyl being reduced by an iron surface could substantially enhance the rate of reduction of selenate under anoxic conditions relevant for a repository.

  5. Molecular dynamics simulations of uranyl adsorption and structure on the basal surface of muscovite

    SciTech Connect

    Teich-McGoldrick, Stephanie L.; Greathouse, Jeffery A.; Cygan, Randall T.

    2014-02-05

    Anthropogenic activities have led to an increased concentration of uranium on the Earth’s surface and potentially in the subsurface with the development of nuclear waste repositories. Uranium is soluble in groundwater, and its mobility is strongly affected by the presence of clay minerals in soils and in subsurface sediments. We use molecular dynamics simulations to probe the adsorption of aqueous uranyl (UO22+) ions onto the basal surface of muscovite, a suitable proxy for typically ultrafine-grained clay phases. Model systems include the competitive adsorption between potassium counterions and aqueous ions (0.1 M and 1.0 M UO2Cl2 , 0.1 M NaCl). We find that for systems with potassium and uranyl ions present, potassium ions dominate the adsorption phenomenon. Potassium ions adsorb entirely as inner-sphere complexes associated with the ditrigonal cavity of the basal surface. Uranyl ions adsorb in two configurations when it is the only ion species present, and in a single configuration in the presence of potassium. Finally, the majority of adsorbed uranyl ions are tilted less than 45° relative to the muscovite surface, and are associated with the Si4Al2 rings near aluminum substitution sites.

  6. Potential New Ligand Systems for Binding Uranyl Ions in Seawater Environments

    SciTech Connect

    Arnold, John

    2014-12-13

    Work began this quarter on a new project involving a combined computational and biosynthetic approach to selective recognition of uranyl ion in aqueous solution. This project exploits the results of computational studies to discover new ligand classes. Synthetic studies will follow to generate target systems for uranyl binding and determination of binding constants. The process will be iterative, with results from computation informing synthesis, and vice versa. The theme of the ligand classes to be examined initially will be biologically based. New phosphonate-containing α-amino acid N-carboxyanhydride (NCA) monomers were used recently to prepare well-defined phosphonate-containing poly-peptides and block copolypeptides. Our first approach is to utilize these phosphate- and phosphonate-containing NCAs for the coordination of uranyl. The work includes the laboratory-scale preparation of a series of NCAs and the full thermodynamic and spectroscopic characterization of the resulting uranyl complexes. We are also evaluating the sequestering activity in different physiological and environmental conditions of these copolymers as well as their biodegradability.

  7. Re-evaluating neptunium in uranyl phases derived from corroded spent fuel.

    SciTech Connect

    Fortner, J. A.; Finch, R. J.; Kropf, A. J.; Cunnane, J. C.; Chemical Engineering

    2004-11-01

    Interest in mechanisms that may control radioelement release from corroded commercial spent nuclear fuel (CSNF) has been heightened by the selection of the Yucca Mountain site in Nevada as the repository for high-level nuclear waste in the United States. Neptunium is an important radionuclide in repository models owing to its relatively long half-life and its high aqueous mobility as neptunyl [Np(V)O+2]. The possibility of neptunium sequestration into uranyl alteration phases produced by corroding CSNF would suggest-a process for lowering neptunium concentration and subsequent migration from a geologic repository. However, there remains little experimental evidence that uranyl compounds will, in fact, serve as long-term host phases for the retention of neptunium under conditions expected in a deep geologic repository. To directly explore this possibility, we examined specimens of uranyl alteration phases derived from humid-air-corroded CSNF by X-ray absorption spectroscopy to better determine neptunium uptake in these phases. Although neptunium fluorescence was readily observed from as-received CSNF, it was not observed from the uranyl alteration rind. We establish upper limits for neptunium incorporation into CSNF alteration phases that are significantly below previously reported concentrations obtained by using electron energy loss spectroscopy (EELS). We attribute the discrepancy to a plural-scattering event that creates a spurious EELS peak at the neptunium-MV energy.

  8. Re-Evaluating Neptunium in Uranyl Phases Derived from Corroded Spent Fuel

    SciTech Connect

    Fortner, Jeffrey A.; Finch, Robert J.; Kropf, A. Jeremy; Cunnane, James C.

    2004-11-15

    Interest in mechanisms that may control radioelement release from corroded commercial spent nuclear fuel (CSNF) has been heightened by the selection of the Yucca Mountain site in Nevada as the repository for high-level nuclear waste in the United States. Neptunium is an important radionuclide in repository models owing to its relatively long half-life and its high aqueous mobility as neptunyl [Np(V)O{sub 2}{sup +}]. The possibility of neptunium sequestration into uranyl alteration phases produced by corroding CSNF would suggest a process for lowering neptunium concentration and subsequent migration from a geologic repository. However, there remains little experimental evidence that uranyl compounds will, in fact, serve as long-term host phases for the retention of neptunium under conditions expected in a deep geologic repository. To directly explore this possibility, we examined specimens of uranyl alteration phases derived from humid-air-corroded CSNF by X-ray absorption spectroscopy to better determine neptunium uptake in these phases. Although neptunium fluorescence was readily observed from as-received CSNF, it was not observed from the uranyl alteration rind. We establish upper limits for neptunium incorporation into CSNF alteration phases that are significantly below previously reported concentrations obtained by using electron energy loss spectroscopy (EELS). We attribute the discrepancy to a plural-scattering event that creates a spurious EELS peak at the neptunium-M{sub V} energy.

  9. Adsorption of uranyl on hydroxylated α-SiO₂(001): a first-principle study.

    PubMed

    Wang, Hui; Chai, Zhifang; Wang, Dongqi

    2015-01-28

    The adsorption of [UO2(H2O)5](2+) on a hydroxylated α-SiO2(001) surface was studied by periodic density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulation. The effects of pH, CO2, aqua solution and anionic ligands (OH(-), NO3(-) and Cl(-)) on the adsorption geometry and stability were investigated. The results show that the adsorption of uranyl on a hydroxylated α-SiO2(001) surface leads to the formation of inner-sphere complexes, in which the bidentate complex at the double deprotonated site is most favored. The binding strengths of bidentate and monodentate complexes at the same site are similar, and they become weaker as the number of protons increases at the adsorption site, indicating an enhancement of the adsorption strength at higher pH values within a certain range. Strong chemical interaction plays an important role in all inner-sphere complexes. The hydrogen bonds are formed between uranyl and the hydroxylated surface in all inner- and outer-sphere complexes. The presence of CO2 weakens the adsorption of uranyl on the surface by forming uranyl carbonate (CO3(2-), HCO3(-)) complexes. The effect of the anion ligands depends on their charged state and their concentration in solutions. The explicit treatment of water environment in the models has a slight effect on the adsorption configuration. These results are consistent with the experimental observations. PMID:25437449

  10. Effects of folic acid deficiency and MTHFR C677T polymorphism on spontaneous and radiation-induced micronuclei in human lymphocytes.

    PubMed

    Leopardi, Paola; Marcon, Francesca; Caiola, Stefania; Cafolla, Arturo; Siniscalchi, Ester; Zijno, Andrea; Crebelli, Riccardo

    2006-09-01

    Folic acid plays a key role in the maintenance of genomic stability, providing methyl groups for the conversion of uracil to thymine and for DNA methylation. Besides dietary habits, folic acid metabolism is influenced by genetic polymorphism. The C677T polymorphism of the methylene-tetrahydrofolate reductase (MTHFR) gene is associated with a reduction of catalytic activity and is suggested to modify cancer risk differently depending on folate status. In this work the effect of folic acid deficiency on genome stability and radiosensitivity has been investigated in cultured lymphocytes of 12 subjects with different MTHFR genotype (four for each genotype). Cells were grown for 9 days with 12, 24 and 120 nM folic acid and analyzed in a comprehensive micronucleus test coupled with centromere characterization by CREST immunostaining. In other experiments, cells were grown with various folic acid concentrations, irradiated with 0.5 Gy of gamma rays and analyzed in the micronucleus test. The results obtained indicate that folic acid deficiency induces to a comparable extent chromosome loss and breakage, irrespective of the MTHFR genotype. The effect of folic acid was highly significant (P < 0.001) and explained >50% of variance of both types of micronuclei. Also nucleoplasmic bridges and buds were significantly increased under low folate supply; the increase in bridges was mainly observed in TT cells, highlighting a significant effect of the MTHFR genotype (P = 0.006) on this biomarker. Folic acid concentration significantly affected radiation-induced micronuclei (P < 0.001): the increased incidence of radiation-induced micronuclei with low folic acid was mainly accounted for by carriers of the variant MTHFR allele (both homozygotes and heterozygotes), but the overall effect of genotype did not attain statistical significance. Treatment with ionizing radiations also increased the frequency of nucleoplasmic bridges. The effect of folic acid level on this end-point was

  11. Observation of Radiolytic Field Alteration of the Uranyl Cation in Bicarbonate Solution

    SciTech Connect

    Snow, Lanee A.; McNamara, Bruce K.; Sinkov, Sergey I.; Cho, Herman M.; Friese, Judah I.

    2006-12-01

    In previous work we demonstrated that radiolysis of uranyl tris carbonate in near neutral pH to alkaline carbonate solutions, could be followed by 13C NMR. Radiolysis of the complex produced novel uranyl peroxo carbonate solution state species, whose structures depended on the pH and radiolytic dose rate. In this work, we investigate speciation of the uranyl carbonate trimer which is predominant in bicarbonate solution near pH 5.9. We observe radiolytically derived speciation to different mixed peroxy carbonate species than seen in the higher pH solutions. Auto radiolysis of uranium (VI) carbonate solutions between pH 5.9 and 7.2 is shown to alter the uranium speciation over relatively short periods of time and was followed by 13C NMR and visible spectrophotometry, using dissolved 233(UO2)3(CO3)6 6- both as the radiolysis source (D= 14.9 Gy/hr) and as a trap for the newly formed hydrogen peroxide. Direct addition of hydrogen peroxide to solutions of the uranyl-carbonate trimer is shown to reproduce the 13 C NMR signatures of the complexe(s) formed by radiolysis, but additionally a variety of new complexes are revealed. Ratios of H2O2/trimer < 1.5 produced a uranyl peroxo carbonate adduct, that is shown to be common to the radiolytically produced species. Ratios of H2O2/ trimer >1 resulted in formation of stable higher order peroxo carbonate complexes. The 13C NMR signatures and visible spectra of these complexes are described here. Rigorous characterization of the species is an ongoing effort.

  12. Role of citrate as a complexing ligand which permits enzymically-mediated uranyl ion bioaccumulation

    SciTech Connect

    Yong, P.; Macaskie, L.E.

    1995-06-01

    Microorganisms can be used to remove toxic heavy metals from liquid industrial wastes. One potentially useful system utilizes the enzymically-mediated biomineralization of heavy metals at the surface of bacterial cells. This well-documented system harnesses a metal-resistant phosphatase enzyme overproduced by a Citrobacter sp.; metal uptake is mediated by the activity of this enzyme, which persists in non-growing cells, to liberate HPO{sub 4}{sup 2-} from glycerol 2-phosphate with stoichiometric deposition of heavy metals(M) as cell-bound MHPO{sub 4}. Recent attention has focused on the treatment of wastes from nuclear power and nuclear fuel reprocessing activities, together with discharges of native uranium in mining wastes. Previous investigations using the Citrobacter sp. demonstrated removal of uranium and the transuranic elements, plutonium and americium. Although uranium is inhibitory to the growth of the Citrobacter strain, and the activity of the cellular phosphatase, uranyl phosphate accumulates as polycrystalline HUO{sub 2}PO{sub 4} at the cell surface. The rate of uranyl removal into the growing crystal is primarily dependent on the rate of phosphate release by the enzyme catalysed reaction. This is inconsistent with the reported toxicity of uranyl ion to the mediating phosphatase; however, in the presence of an excess of substrate, the rapid rate of phosphate release facilitated metal precipitation without toxic effect. Under substrate-limiting conditions uranyl toxicity was seen. The present investigation shows the inhibition of Citrobacter sp. phosphatase is related to the concentration of uranyl ion, and that citrate buffer can protect against this toxicity, and permit metal bioaccumulation. The toxicity pattern is dependent upon the substrate used; possible reasons for these effects, and environmental implications are discussed. 18 refs., 5 figs.

  13. Immunity decreases, antioxidant system damages and tight junction changes in the intestine of grass carp (Ctenopharyngodon idella) during folic acid deficiency: Regulation of NF-κB, Nrf2 and MLCK mRNA levels.

    PubMed

    Shi, Lei; Feng, Lin; Jiang, Wei-Dan; Liu, Yang; Jiang, Jun; Wu, Pei; Kuang, Sheng-Yao; Tang, Ling; Tang, Wu-Neng; Zhang, Yong-An; Zhou, Xiao-Qiu

    2016-04-01

    This investigation used the same growth trial as the previous study, which showed that folic acid deficiency retarded growth in young grass carp (the percent weight gain of Groups 1-6 were 102.32 ± 3.41%, 137.25 ± 10.48%, 179.78 ± 3.95%, 164.33 ± 3.21%, 143.35 ± 8.12% and 115.28 ± 2.66%) [1]. In the present study, we investigated the effects of dietary folic acid on the immune response, antioxidant status and tight junctions in the intestine of young grass carp (Ctenopharyngodon idella). A total of 540 young grass carp were fed diets containing graded levels of folic acid at 0.10, 0.47, 1.03, 1.48, 1.88 and 3.12 mg kg(-1) diet for 8 weeks. The results indicated that acid phosphatase and lysozyme activities, and the complement component 3 content in the proximal intestine (PI), mid intestine (MI) and distal intestine (DI) were decreased with folic acid deficiency (0.1 mg kg(-1)) (P < 0.05). Folic acid deficiency (0.1 mg kg(-1)) up-regulated interleukin 1β, interleukin 8, tumor necrosis factor α, nuclear factor κB p65 (NF-κB p65), IκB kinase α (IKK-α), IKK-β and IKK-γ gene expression, meanwhile down-regulated interleukin 10, transforming growth factor β, IκB and target of rapamycin gene expression in the PI, MI and DI (P < 0.05). These data suggested that folic acid deficiency decreased fish intestinal innate immune function may be partly contributed to the regulation of NF-κB p65 pathway. Moreover, the activities and corresponding gene expression of glutathione content, Cu/Zn superoxide dismutase, catalase, glutathione peroxidase, glutathione s-transferases and glutathione reductase in fish intestine were depressed by deficient folic acid diet (0.1 mg kg(-1)) (P < 0.05). Furthermore, folic acid deficiency (0.1 mg kg(-1)) down-regulated NF-E2-related factor 2 (Nrf2) gene expression, up-regulated Kelch-like-ECH-associated protein 1a (Keap1a) and Keap1b gene expression in fish intestine (P < 0.05). These data indicated

  14. Absorption and metabolism of ( sup 3 H)arachidonic and ( sup 14 C)linoleic acid in essential fatty acid-deficient rats

    SciTech Connect

    Hjelte, L.; Melin, T.; Nilsson, A.; Strandvik, B. )

    1990-07-01

    ({sup 3}H)arachidonic acid (20:4) and ({sup 14}C)linoleic acid (18:2) were fed in a triolein emulsion to essential fatty acid-deficient (EFAD) rats and to age-matched controls. Tissues were analyzed for radioactivity of different lipid classes after 1, 2, and 4 h. As in earlier studies, control rats retained more ({sup 3}H)20:4 than ({sup 14}C)18:2 in all organs except adipose tissue. In EFAD rats, recovery of ({sup 14}C)18:2 was increased in small intestine, liver, heart, and kidneys. In comparison to controls, EFAD rats retained much more ({sup 14}C)18:2 in phospholipids of these organs. The increase in the incorporation of both {sup 3}H and {sup 14}C into phosphatidylethanolamine was particularly pronounced. Another striking feature was the drastic increase in the retention after 4 h of {sup 14}C in cardiolipin, which is specifically located in the inner mitochondrial membrane. In contrast, incorporation of both {sup 3}H and {sup 14}C into phosphatidylinositol was decreased or unchanged in EFAD rats. Although fecal fat excretion was increased there was no evidence for a malabsorption or an increased retention in intestinal triacyglycerol of the radioactive fatty acids in EFAD rats. The proportion of ({sup 14}C)18:2 that had been converted to ({sup 14}C)20:4 was generally low but increased significantly with time in the liver and intestine of EFAD rats.

  15. Dietary omega-3 fatty acid deficiency and high fructose intake in the development of metabolic syndrome, brain metabolic abnormalities, and non-alcoholic fatty liver disease.

    PubMed

    Simopoulos, Artemis P

    2013-08-01

    Western diets are characterized by both dietary omega-3 fatty acid deficiency and increased fructose intake. The latter found in high amounts in added sugars such as sucrose and high fructose corn syrup (HFCS). Both a low intake of omega-3 fatty acids or a high fructose intake contribute to metabolic syndrome, liver steatosis or non-alcoholic fatty liver disease (NAFLD), promote brain insulin resistance, and increase the vulnerability to cognitive dysfunction. Insulin resistance is the core perturbation of metabolic syndrome. Multiple cognitive domains are affected by metabolic syndrome in adults and in obese adolescents, with volume losses in the hippocampus and frontal lobe, affecting executive function. Fish oil supplementation maintains proper insulin signaling in the brain, ameliorates NAFLD and decreases the risk to metabolic syndrome suggesting that adequate levels of omega-3 fatty acids in the diet can cope with the metabolic challenges imposed by high fructose intake in Western diets which is of major public health importance. This review presents the current status of the mechanisms involved in the development of the metabolic syndrome, brain insulin resistance, and NAFLD a most promising area of research in Nutrition for the prevention of these conditions, chronic diseases, and improvement of Public Health. PMID:23896654

  16. Mitochondrial and Oxidative Stress Aspects in Hippocampus of Rats Submitted to Dietary n-3 Polyunsaturated Fatty Acid Deficiency After Exposure to Early Stress.

    PubMed

    Ferreira, Charles Francisco; Bernardi, Juliana Rombaldi; da Silva, Diego Carrilho; de Sá Couto-Pereira, Natividade; de Souza Mota, Carina; Krolow, Rachel; Weis, Simone Nardin; Pettenuzzo, Letícia; Kapczinski, Flávio; Silveira, Patrícia Pelufo; Dalmaz, Carla

    2015-09-01

    Chronic dietary long-chain polyunsaturated fatty acids (PUFAs) deficiency may lead to changes in cortex and hippocampus neuronal membrane phospholipids, and may be linked to impaired central nervous system function. Particularly docosahexaenoic acid deficiency appears to be involved in neuropsychiatric disorders. On the other hand, adverse events early in life may also profoundly affect brain development, leading to long-lasting effects on neurophysiology, neurobiology and behavior. This research assessed if neonatal stress and a dietary n-3 PUFAs deficiency could interact to produce hippocampal alterations related to mitochondrial functions in adult rats. There were no effects of diet, neonatal intervention or interactions on superoxide dismutase or catalase enzymatic activities, mitochondrial membrane potential and respiratory chain complexes. Rats fed n-3 PUFAs deficient diet displayed higher levels of glutathione peroxidase and catalase activity, higher free radicals production and higher thiol content compared to rats fed n-3 PUFAs adequate diet. There were interactions among diets and neonatal stress, since glutathione peroxidase, free radicals production and thiol content were increased in groups that were subjected to neonatal interventions fed n-3 PUFAs deficient diet. Additionally, reduced mitochondrial potential was observed in handled animals. Total thiol revealed a neonatal stress effect, since animals subjected to neonatal interventions displayed lower thiol content. In conclusion, we observed that a chronic treatment with deficient n-3 PUFAs diet, from the puberty period on, increased free radicals production and imbalanced antioxidant enzymes activities, and these increases were higher in animals subjected to neonatal interventions.

  17. Purification of alkali metal nitrates

    DOEpatents

    Fiorucci, Louis C.; Gregory, Kevin M.

    1985-05-14

    A process is disclosed for removing heavy metal contaminants from impure alkali metal nitrates containing them. The process comprises mixing the impure nitrates with sufficient water to form a concentrated aqueous solution of the impure nitrates, adjusting the pH of the resulting solution to within the range of between about 2 and about 7, adding sufficient reducing agent to react with heavy metal contaminants within said solution, adjusting the pH of the solution containing reducing agent to effect precipitation of heavy metal impurities and separating the solid impurities from the resulting purified aqueous solution of alkali metal nitrates. The resulting purified solution of alkali metal nitrates may be heated to evaporate water therefrom to produce purified molten alkali metal nitrate suitable for use as a heat transfer medium. If desired, the purified molten form may be granulated and cooled to form discrete solid particles of alkali metal nitrates.

  18. Ammonium nitrate explosive systems

    DOEpatents

    Stinecipher, Mary M.; Coburn, Michael D.

    1981-01-01

    Novel explosives which comprise mixtures of ammonium nitrate and an ammonium salt of a nitroazole in desired ratios are disclosed. A preferred nitroazole is 3,5-dinitro-1,2,4-triazole. The explosive and physical properties of these explosives may readily be varied by the addition of other explosives and oxidizers. Certain of these mixtures have been found to act as ideal explosives.

  19. Nitrate Storage and Dissimilatory Nitrate Reduction by Eukaryotic Microbes.

    PubMed

    Kamp, Anja; Høgslund, Signe; Risgaard-Petersen, Nils; Stief, Peter

    2015-01-01

    The microbial nitrogen cycle is one of the most complex and environmentally important element cycles on Earth and has long been thought to be mediated exclusively by prokaryotic microbes. Rather recently, it was discovered that certain eukaryotic microbes are able to store nitrate intracellularly and use it for dissimilatory nitrate reduction in the absence of oxygen. The paradigm shift that this entailed is ecologically significant because the eukaryotes in question comprise global players like diatoms, foraminifers, and fungi. This review article provides an unprecedented overview of nitrate storage and dissimilatory nitrate reduction by diverse marine eukaryotes placed into an eco-physiological context. The advantage of intracellular nitrate storage for anaerobic energy conservation in oxygen-depleted habitats is explained and the life style enabled by this metabolic trait is described. A first compilation of intracellular nitrate inventories in various marine sediments is presented, indicating that intracellular nitrate pools vastly exceed porewater nitrate pools. The relative contribution by foraminifers to total sedimentary denitrification is estimated for different marine settings, suggesting that eukaryotes may rival prokaryotes in terms of dissimilatory nitrate reduction. Finally, this review article sketches some evolutionary perspectives of eukaryotic nitrate metabolism and identifies open questions that need to be addressed in future investigations. PMID:26734001

  20. Nitrate Storage and Dissimilatory Nitrate Reduction by Eukaryotic Microbes.

    PubMed

    Kamp, Anja; Høgslund, Signe; Risgaard-Petersen, Nils; Stief, Peter

    2015-01-01

    The microbial nitrogen cycle is one of the most complex and environmentally important element cycles on Earth and has long been thought to be mediated exclusively by prokaryotic microbes. Rather recently, it was discovered that certain eukaryotic microbes are able to store nitrate intracellularly and use it for dissimilatory nitrate reduction in the absence of oxygen. The paradigm shift that this entailed is ecologically significant because the eukaryotes in question comprise global players like diatoms, foraminifers, and fungi. This review article provides an unprecedented overview of nitrate storage and dissimilatory nitrate reduction by diverse marine eukaryotes placed into an eco-physiological context. The advantage of intracellular nitrate storage for anaerobic energy conservation in oxygen-depleted habitats is explained and the life style enabled by this metabolic trait is described. A first compilation of intracellular nitrate inventories in various marine sediments is presented, indicating that intracellular nitrate pools vastly exceed porewater nitrate pools. The relative contribution by foraminifers to total sedimentary denitrification is estimated for different marine settings, suggesting that eukaryotes may rival prokaryotes in terms of dissimilatory nitrate reduction. Finally, this review article sketches some evolutionary perspectives of eukaryotic nitrate metabolism and identifies open questions that need to be addressed in future investigations.

  1. Nitrate Storage and Dissimilatory Nitrate Reduction by Eukaryotic Microbes

    PubMed Central

    Kamp, Anja; Høgslund, Signe; Risgaard-Petersen, Nils; Stief, Peter

    2015-01-01

    The microbial nitrogen cycle is one of the most complex and environmentally important element cycles on Earth and has long been thought to be mediated exclusively by prokaryotic microbes. Rather recently, it was discovered that certain eukaryotic microbes are able to store nitrate intracellularly and use it for dissimilatory nitrate reduction in the absence of oxygen. The paradigm shift that this entailed is ecologically significant because the eukaryotes in question comprise global players like diatoms, foraminifers, and fungi. This review article provides an unprecedented overview of nitrate storage and dissimilatory nitrate reduction by diverse marine eukaryotes placed into an eco-physiological context. The advantage of intracellular nitrate storage for anaerobic energy conservation in oxygen-depleted habitats is explained and the life style enabled by this metabolic trait is described. A first compilation of intracellular nitrate inventories in various marine sediments is presented, indicating that intracellular nitrate pools vastly exceed porewater nitrate pools. The relative contribution by foraminifers to total sedimentary denitrification is estimated for different marine settings, suggesting that eukaryotes may rival prokaryotes in terms of dissimilatory nitrate reduction. Finally, this review article sketches some evolutionary perspectives of eukaryotic nitrate metabolism and identifies open questions that need to be addressed in future investigations. PMID:26734001

  2. Treatment tests for ex situ removal of chromate, nitrate, and uranium (VI) from Hanford (100-HR-3) groundwater. Final report

    SciTech Connect

    Beck, M.A.; Duncan, J.B.

    1993-11-15

    This report describes batch and anion exchange column laboratory-scale studies investigating ex situ methods to remove chromate (chromium [VI]), nitrate (NO{sub 3}), and uranium (present as uranyl (uranium [VI]) carbonato anionic species) from contaminated Hanford Site groundwaters. The technologies investigated include chemical precipitation or coprecipitation to remove chromate and uranium, and anion exchange to remove chromate, uranium, and nitrate. The technologies investigated were specified in the 100-HR-3 Groundwater Treatability Test Plan (DOE-RL 1993). The goal of these tests was to determine the best method to remove selected contaminants to below the concentration of the project performance goals. The raw data and observations made during these tests can be found in the Westinghouse Hanford Company (WHC) laboratory notebooks (Beck 1992, Herting 1993). The method recommended for future study is anion exchange with Dowex 21K resin.

  3. INCORPORATION OF PENTAVALENT NEPTUNIUM INTO URANYL PHASES THAT MAY FORM AS ALTERATION PRODUCTS OF SPENT NUCLEAR FUEL

    SciTech Connect

    NA

    2005-06-21

    Laboratory-scale simulations and studies of natural analogues have shown that alteration of spent nuclear fuel in a moist, oxidizing environment results in the formation of a variety of uranyl phases. Neptunium-237 has a half-life of 2.14 million years, and the pentavalent oxidation state is soluble in groundwater. Release of Np-237 from spent nuclear fuel in a geological repository may significantly impact the long-term performance of such a repository. Incorporation of Np, in the pentavalent oxidation state, into uranyl phases by substitution for hexavalent U is likely because of the similarity of the coordination environments of these two cations, but a charge-balance mechanism is required for substitution. A preliminary study has shown incorporation of pentavalent Np into powders of the uranyl silicate uranophane, and Na-compreignacite, a uranyl oxyhydrate [1]. Using synthesis experiments under mild hydrothermal conditions, we are examining the incorporation of pentavalent Np into selected uranyl oxyhydrates and silicates as a function of temperature and the pH of the mother solution. Analyses of powders of these uranyl phases has demonstrated both temperature and pH dependences for incorporation. Experiments are underway directed at the synthesis of single crystals of uranyl phases in the presence of 500-750 ppm pentavalent Np. The intent is to develop a basic understanding of the crystallographic and crystal chemical factors that impact incorporation of pentavalent Np into uranyl phases. Following synthesis, crystals are analyzed for Np using laser ablation ICP-MS. Preliminary results for Na-substituted metaschoepite indicate significant Np has been incorporated into the crystals. Additional phases under study include compreignacite, becquerelite, soddyite, zippeite, and (UO{sub 2}){sub 3}(PO{sub 4}){sub 2}(H{sub 2}O){sub 4}.

  4. Uranyl adsorption at solvated edge surfaces of 2 : 1 smectites. A density functional study.

    PubMed

    Kremleva, Alena; Krüger, Sven; Rösch, Notker

    2015-05-28

    We systematically studied the adsorption of uranyl(vi) on two common edge surfaces, (010) and (110), of 2 : 1 smectite clay minerals, using standard periodic DFT models. To describe various types of permanently charged clay minerals, we introduced charged defects into the initially neutral layer of pyrophyllite, cation substitutions in tetrahedral (beidellitic) and octahedral (montmorillonitic) sheets. Comparing uranyl(vi) species at various sites of these two types of surfaces, we found that structural parameters of such adsorption complexes are essentially determined by the surface chemical groups forming the adsorption site, not by the type of the clay mineral. Even for sites involving a substituted cation we noticed only a weak effect of the substitution on the geometric parameters. Geometry optimization resulted in adsorbed uranyl or uranyl hydroxide, with coordination numbers of 4 or 5. However, in most cases the same species was determined on the same type of site, independent of the substitutions. Optimization of adsorbed uranyl leads to hydrolysis at sites close to a AlOH(-1/2) surface group, resulting in uranyl monohydroxide as adsorbate and protonation of the AlOH(-1/2) group. While most species are equatorially five-coordinated, coordination 4 is preferred when uranyl adsorbs on mixed AlO(H)-SiO(H) sites. Calculated formation energies of surface complexes do not single out a preferred species or site, but point to an equilibrium of several species. Comparison to experiment and consideration of pH conditions suggests AlOHOH and AlOH-SiO sites of (010) surfaces and AlOmOH, SiOOm, and AlOH-SiO sites of (110) surfaces as most probable for uranyl adsorption. PMID:25941904

  5. [The genotoxic action of uranyl ions on DNA in vitro caused by the generation of reactive oxygen species].

    PubMed

    Smirnova, V S; Gudkov, S V; Shtarkman, I N; Chernikov, A V; Bruskov, V I

    2005-01-01

    8-Oxoguanine (8-OG) is an important biomarker of oxidative DNA damage induced by reactive oxygen species (ROS). By using ELISA with monoclonal antibodies against 8-OG, the formation of 8-OG in DNA by the action of uranyl ions, gamma-irradiation, and heating at 37 degrees C and their combined action was investigated in view of environmental pollution by uranium oxides as a result of the use of armor piercing shells with depleted uranium. The content of 8-OG in DNA induced by the action of gamma-irradiation, 5 microM uranyl ions and heating changes with time in a complicated manner. These results suggest that, by the action of uranyl ions, an additional generation of ROS occurs, which leads both to the formation of 8-OG in DNA and its further oxidation. Uranyl ions at a conceptration of 5 microM increase the thermal deamination of cytosine in DNA several times but do not influence DNA thermal depurination. It is shown that uranyl ions essentially increase the production of hydrogen peroxide and hydroxyl radicals by the action of heat on water. The results indicate a high chemical genotoxicity of uranyl ions and their enhancing effect on DNA base damage by the action of heat and gamma-irradiation.

  6. An improved extraction chromatographic resin for the separation of uranium from acidic nitrate media.

    PubMed

    Dietz, M L; Horwitz, E P; Sajdak, L R; Chiarizia, R

    2001-07-01

    The preparation and characterization of a new extraction chromatographic resin exhibiting extraordinarily strong retention of hexavalent uranyl ion over a wide range of nitric acid concentrations and very high selectivity for U(VI) over Fe(III) and numerous other cations is described. This new material (designated U/TEVA-2) comprises a novel liquid stationary phase consisting of an equimolar mixture of diamyl amylphosphonate (DA[AP]) and Cyanex 923((R)) (a commercially available trialkyl-phosphine oxide, TRPO) sorbed on silanized silica or Amberchrom CG-71. Cyanex 923 is shown to be preferable to a related TRPO, Cyanex 925((R)), due to its lower viscosity and higher selectivity for U(VI) over Fe(III). The retention of uranyl nitrate by the U/TEVA-2 resin, as measured by the k' values (number of free column values to peak maximum) is >5000 from approximately 0.1 to 8 M HNO(3). The ability of the new resin to strongly and selectively retain U(VI) from such a wide range of acid concentrations, along with its favorable physical properties, make it a good candidate for application in the separation and preconcentration of U(VI) from complex environmental, biological, and nuclear waste samples for subsequent determination.

  7. Diluent and extractant effects on the enthalpy of extraction of uranium(VI) and americium(III) nitrates by trialkyl phosphates

    SciTech Connect

    Srinivasan, T.G.; Vasudeva Rao, P.R.; Sood, D.D.

    1998-11-01

    The effect of various diluents such as n-hexane, n-heptane n-octane, isooctane, n-decane, n-undecane, n-dodecane, n-tetradecane, n-hexadecane, cyclohexane, benzene, toluene, p-xylene, mesitylene and o-dichlorobenzene on the enthalpy of extraction of uranyl nitrate by tri-n-amyl phosphate (TAP) over the temperature range 283 K--333 K has been studied. The results indicate that the enthalpy of extraction does not vary significantly with the diluents studied. Also enthalpies of extraction of uranyl nitrate and americium(III) nitrate by neutral organo phosphorous extractants such as tri-n-butyl phosphate (TBP), tri-n-amyl phosphate (TAP), tri-sec-butyl phosphate (TsBP), tri-isoamyl phosphate (TiAP) and tri-n-hexyl phosphate (THP) have been studied. An attempt has been made to explain the trends, on the basis of the nature of the solvate formed and the different terms which contribute to the overall enthalpy change.

  8. Glycine lithium nitrate crystals

    NASA Astrophysics Data System (ADS)

    González-Valenzuela, R.; Hernández-Paredes, J.; Medrano-Pesqueira, T.; Esparza-Ponce, H. E.; Jesús-Castillo, S.; Rodriguez-Mijangos, R.; Terpugov, V. S.; Alvarez-Ramos, M. E.; Duarte-Möller, A.

    Crystals of glycine lithium nitrate with non-linear optical properties have been grown in a solution by slow evaporation at room temperature. The crystal shows a good thermal stability from room temperature to 175 °C where the crystal begins to degrade. This property is desirable for future technological applications. Also, a good performance on the second harmonic generation was found, characterizing the emitted dominant wavelength by a customized indirect procedure using luminance and chromaticity measured data based on the CIE-1931 standard. Additionally, the 532 nm signal was detected by using a variant to the Kurtz and Perry method.

  9. Biosensing for the Environment and Defence: Aqueous Uranyl Detection Using Bacterial Surface Layer Proteins

    PubMed Central

    Conroy, David J.R.; Millner, Paul A.; Stewart, Douglas I.; Pollmann, Katrin

    2010-01-01

    The fabrication of novel uranyl (UO22+) binding protein based sensors is reported. The new biosensor responds to picomolar levels of aqueous uranyl ions within minutes using Lysinibacillus sphaericus JG-A12 S-layer protein tethered to gold electrodes. In comparison to traditional self assembled monolayer based biosensors the porous bioconjugated layer gave greater stability, longer electrode life span and a denser protein layer. Biosensors responded specifically to UO22+ ions and showed minor interference from Ni2+, Cs+, Cd2+ and Co2+. Chemical modification of JG-A12 protein phosphate and carboxyl groups prevented UO22+ binding, showing that both moieties are involved in the recognition to UO22+. PMID:22399904

  10. Nutritional modulation of guinea pig skin hyperproliferation by essential fatty acid deficiency is associated with selective down regulation of protein kinase C-beta.

    PubMed

    Cho, Y; Ziboh, V A

    1995-11-01

    In a previous study we demonstrated that 13-hydroxyoctadecadienoic acid (13-HODE), a 15-lipoxygenase metabolite of linoleic acid is incorporated into epidermal phosphatidyl 4,5-bisphosphate (PtdIns 4,5-P2) and released as 13-HODE-containing-diacylglycerol (13-HODE-DAG). In vitro, 13-HODE-DAG was shown to selectively inhibit epidermal total protein kinase C (PKC-beta) activity. To determine whether these observations are relevant in vivo, guinea pigs were made essential fatty acid deficient (EFAD) by feeding them a basal diet supplemented with 4% hydrogenated coconut oil for 8 wk. Tissue levels of putative 13-HODE-DAG, protein kinase C (PKC) isozymes and tissue hyperproliferation were determined in the epidermal preparations from skin of control safflower oil-fed guinea pigs, those fed EFAD diet and those fed EFAD diet followed by the control diet for 2 wk. Our data revealed that cutaneous 13-HODE and 13-HODE-DAG were significantly lower in EFAD animals than in safflower-fed controls. These reductions were associated with both elevated epidermal hyperproliferation and elevated expressions and activities of PKC-alpha and beta-isozymes. Refeeding the animals with safflower oil for 2 wk replenished tissue levels of 13-HODE-DAG, which inversely correlated with the selective down regulation of PKC-beta expression and activity and the reversal of hyperproliferation. In contrast, although, the expression and activity of PKC-alpha was elevated in the epidermis of the EFAD guinea pigs, this elevated PKC-alpha expression was not down regulated after refeeding the safflower oil diet to the animals.(ABSTRACT TRUNCATED AT 250 WORDS)

  11. Evaluation of docosahexaenoic acid deficiency as a preventable risk factor for recurrent affective disorders: current status, future directions, and dietary recommendations.

    PubMed

    McNamara, Robert K

    2009-01-01

    Major recurrent affective disorders, including major depressive disorder (MDD) and bipolar disorder, represent a growing public health crisis in the United States. Evidence from cross-national and cross-sectional epidemiological surveys, comparative peripheral and central composition studies, and placebo-controlled intervention trials suggest that n-3 fatty acid deficiency may contribute to the pathoaetiology of affective disorders. These data are reviewed with the objective of estimating a daily docosahexaenoic acid (DHA, 22:6n-3) intake value that is projected to be efficacious in mitigating vulnerability. It is proposed that daily DHA intake sufficient to increase erythrocyte DHA composition to a level found in healthy subjects from Japan (7%), where the lifetime prevalence rates of MDD and bipolar disorder are several fold lower than the US, represents an appropriate target. To achieve this target, preliminary DHA intervention trials indicate that a daily dose of 400-700 mg/d in children and 700-1000 mg/d in adults would be required. Based on the results of placebo-controlled intervention trials, a higher daily DHA dose in the order of 1000-1500 mg/d in a 2:1 eicosapentaenoic acid (EPA, 20:5n-3):DHA ratio may be optimal for the treatment of established affective disorders. These recommendations are intended to guide future dose-ranging placebo-controlled DHA intervention trials in patients with established affective disorders, as well as in asymptomatic subjects at elevated risk for developing affective disorders. Such early intervention studies are currently feasible and will ultimately be required to definitively evaluate whether DHA is a required nutrient for the prevention of affective disorders.

  12. The Effect of varying ratios of docosahexaenoic Acid and arachidonic acid in the prevention and reversal of biochemical essential fatty acid deficiency in a murine model

    PubMed Central

    Le, Hau D.; Fallon, Erica M.; Kalish, Brian T.; de Meijer, Vincent E.; Meisel, Jonathan A.; Gura, Kathleen M.; Nose, Vania; Pan, Amy H.; Bistrian, Bruce R.; Puder, Mark

    2012-01-01

    Objective Essential fatty acids (EFA) are necessary for growth, development, and biological function, and must be acquired through the diet. While linoleic acid (LA) and alpha-linolenic acid (ALA) have been considered the true EFAs, we previously demonstrated that docosahexaenoic acid (DHA) and arachidonic acid (AA) taken together as the sole source of dietary fatty acids can prevent biochemical essential fatty acid deficiency (EFAD). This study evaluates the effect of varying dietary ratios of DHA:AA in the prevention and reversal of biochemical EFAD in a murine model. Methods Using a murine model of EFAD, we provided mice with 2.1% of daily caloric intake in varying DHA:AA ratios (1:1, 5:1, 10:1, 20:1, 200:1, 100:0) for 19 days in association with a liquid high-carbohydrate fat-free diet to evaluate the effect on fatty acid profiles. In a second experiment, we evaluated the provision of varying DHA:AA ratios (20:1, 200:1, 100:0) on the reversal of biochemical EFAD. Results Mice provided with DHA and AA had no evidence of biochemical EFAD, regardless of the ratio (1:1, 5:1, 10:1, 20:1, 200:1, 100:0) administered. Biochemical EFAD was reversed with DHA:AA ratios of 20:1, 200:1, and 100:0 following 3 and 5 weeks of dietary provision, although the 20:1 ratio was most effective in the reversal and stabilization of the triene:tetraene ratio. Conclusion Provision of DHA and AA, at 2.1% of daily caloric intake in varying ratios can prevent biochemical evidence of EFAD and hepatic steatosis over the short-term, with a ratio of 20:1 DHA:AA most effectively reversing EFAD. PMID:23151438

  13. Stimulation of proliferation of an essential fatty acid-deficient fish cell line by C20 and C22 polyunsaturated fatty acids and effects on fatty acid composition.

    PubMed

    Tocher, D R; Dick, J R; Sargent, J R

    1996-11-01

    Recently we reported the development of a fish cell line, EPC-EFAD, derived from the carp (Cyprinus carpio) epithelial papilloma line, EPC, that could survive and proliferate in essential fatty acid-deficient (EFAD) medium. The EPC-EFAD cell line may be a useful model system in which to study the cellular biochemical effects of EFA deficiency and has advantages in studies of polyunsaturated fatty acid (PUFA) and eicosanoid metabolism in fish in that the complications introduced by culture in relatively n-6 PUFA-rich mammalian sera are removed. In the present study, the effects on cell proliferation rate of supplementing EPC-EFAD cells with various n-3 and n-6 PUFA were investigated to determine the possible role(s) of PUFA in cell growth and division. The selectivity of incorporation of specific PUFA into individual glycerophospholipid classes and the feasibility of reproducing in vivo fatty acid compositions in vitro were also investigated. Proliferation of the EPC-EFAD cell line was stimulated by arachidonic (20:4 n-6), eicosapentaenoic (20:5 n-3) and docosahexaenoic (22:6 n-3) fatty acids but not by 18:2 n-6 or 18:3 n-3. The differential effects of PUFA on cellular proliferation may be related to the lack of significant delta 5 desaturase activity in the cells at 22 degrees C and may implicate a role for eicosanoids in the mechanism of stimulation of proliferation. PUFA supplementation increased the cytotoxic effects of longer term culture, an effect that was partly alleviated by inclusion of vitamin E in the culture medium. The cells could generally be supplemented with PUFA to produce cellular fatty acid compositions in vitro that were similar to in vivo compositions. PMID:8981632

  14. Effects of essential amino acid deficiency: down-regulation of KCC2 and the GABAA receptor; disinhibition in the anterior piriform cortex.

    PubMed

    Sharp, James W; Ross-Inta, Catherine M; Baccelli, Irène; Payne, John A; Rudell, John B; Gietzen, Dorothy W

    2013-11-01

    The anterior piriform cortex (APC) is activated by, and is the brain area most sensitive to, essential (indispensable) amino acid (IAA) deficiency. The APC is required for the rapid (20 min) behavioral rejection of IAA deficient diets and increased foraging, both crucial adaptive functions supporting IAA homeostasis in omnivores. The biochemical mechanisms signaling IAA deficiency in the APC block initiation of translation in protein synthesis via uncharged tRNA and the general amino acid control kinase, general control nonderepressing kinase 2. Yet, how inhibition of protein synthesis activates the APC is unknown. The neuronal K(+) Cl(-) cotransporter, neural potassium chloride co-transporter (KCC2), and GABAA receptors are essential inhibitory elements in the APC with short plasmalemmal half-lives that maintain control in this highly excitable circuitry. After a single IAA deficient meal both proteins were reduced (vs. basal diet controls) in western blots of APC (but not neocortex or cerebellum) and in immunohistochemistry of APC. Furthermore, electrophysiological analyses support loss of inhibitory elements such as the GABAA receptor in this model. As the crucial inhibitory function of the GABAA receptor depends on KCC2 and the Cl(-) transmembrane gradient it establishes, these results suggest that loss of such inhibitory elements contributes to disinhibition of the APC in IAA deficiency. The circuitry of the anterior piriform cortex (APC) is finely balanced between excitatory (glutamate, +) and inhibitory (GABA, -) transmission. GABAA receptors use Cl(-), requiring the neural potassium chloride co-transporter (KCC2). Both are rapidly turning-over proteins, dependent on protein synthesis for repletion. In IAA (indispensable amino acid) deficiency, within 20 min, blockade of protein synthesis prevents restoration of these inhibitors; they are diminished; disinhibition ensues. GCN2 = general control non-derepressing kinase 2, eIF2α = α-subunit of the eukaryotic

  15. Identification of genes and pathways involved in the synthesis of Mead acid (20:3n-9), an indicator of essential fatty acid deficiency.

    PubMed

    Ichi, Ikuyo; Kono, Nozomu; Arita, Yuka; Haga, Shizuka; Arisawa, Kotoko; Yamano, Misato; Nagase, Mana; Fujiwara, Yoko; Arai, Hiroyuki

    2014-01-01

    In mammals, 5,8,11-eicosatrienoic acid (Mead acid, 20:3n-9) is synthesized from oleic acid during a state of essential fatty acid deficiency (EFAD). Mead acid is thought to be produced by the same enzymes that synthesize arachidonic acid and eicosapentaenoic acid, but the genes and the pathways involved in the conversion of oleic acid to Mead acid have not been fully elucidated. The levels of polyunsaturated fatty acids in cultured cells are generally very low compared to those in mammalian tissues. In this study, we found that cultured cells, such as NIH3T3 and Hepa1-6 cells, have significant levels of Mead acid, indicating that cells in culture are in an EFAD state under normal culture conditions. We then examined the effect of siRNA-mediated knockdown of fatty acid desaturases and elongases on the level of Mead acid, and found that knockdown of Elovl5, Fads1, or Fads2 decreased the level of Mead acid. This and the measured levels of possible intermediate products for the synthesis of Mead acid such as 18:2n-9, 20:1n-9 and 20:2n-9 in the knocked down cells indicate two pathways for the synthesis of Mead acid: pathway 1) 18:1n-9→(Fads2)→18:2n-9→(Elovl5)→20:2n-9→(Fads1)→20:3n-9 and pathway 2) 18:1n-9→(Elovl5)→20:1n-9→(Fads2)→20:2n-9→(Fads1)→20:3n-9.

  16. Water versus acetonitrile coordination to uranyl. Density functional study of cooperative polarization effects in solution.

    PubMed

    Bühl, Michael; Sieffert, Nicolas; Chaumont, Alain; Wipff, Georges

    2011-01-01

    Optimizations at the BLYP and B3LYP levels are reported for mixed uranyl-water/acetonitrile complexes [UO(2)(H(2)O)(5-n)(MeCN)(n)](2+) (n = 0-5), in both the gas phase and a polarizable continuum modeling acetonitrile. Car-Parrinello molecular dynamics (CPMD) simulations have been performed for these complexes in the gas phase, and for selected species (n = 0, 1, 3, 5) in a periodic box of liquid acetonitrile. According to structural and energetic data, uranyl has a higher affinity for acetonitrile than for water in the gas phase, in keeping with the higher dipole moment and polarizability of acetonitrile. In acetonitrile solution, however, water is the better ligand because of specific solvation effects. Analysis of the dipole moment of the coordinated water molecule in [UO(2)(H(2)O)(MeCN)(4)](2+) reveals that the interaction with the second-shell solvent molecules (through fairly strong and persistent O-H···N hydrogen bonds) causes a significant increase of this dipole moment (by more than 1 D). This cooperative polarization of water reinforces the uranyl-water bond as well as the water solvation via strengthened (UO(2))OH(2)···NCMe hydrogen bonds. Such cooperativity is essentially absent in the acetonitrile ligands that make much weaker (UO(2))NCMe···NCMe hydrogen bonds. Beyond the uranyl case, this study points to the importance of cooperative polarization effects to enhance the M(n+) ion affinity for water in condensed phases involving M(n+)-OH(2)···A fragments, where A is a H-bond proton acceptor and M(n+) is a hard cation. PMID:21126026

  17. Recuperation of uranyl ions from effluents by means of microbiological collectors

    SciTech Connect

    Cecal, A.; Palamaru, I.; Humelnicu, D.; Goanta, M.; Rudic, V.; Salaru, V.V.; Gulea, A.

    1997-12-31

    This paper deals with the study of bioaccumulation of uranyl ions (UO{sub 2}{sup 2+}) from industrial effluents, using microbiological collectors: Nostoc linkia sp., Tolipotrix sp., Spirulina sp., Porphyridium cruentum and also the glucide extract of P. cruentum. The values of retaining degree of UO{sub 2}{sup 2+} on the biomass, for several experimental conditions, were established between 14.22 and 91.99%.

  18. Removal of toxic uranium from synthetic nuclear power reactor effluents using uranyl ion imprinted polymer particles.

    PubMed

    Preetha, Chandrika Ravindran; Gladis, Joseph Mary; Rao, Talasila Prasada; Venkateswaran, Gopala

    2006-05-01

    Major quantities of uranium find use as nuclear fuel in nuclear power reactors. In view of the extreme toxicity of uranium and consequent stringent limits fixed by WHO and various national governments, it is essential to remove uranium from nuclear power reactor effluents before discharge into environment. Ion imprinted polymer (IIP) materials have traditionally been used for the recovery of uranium from dilute aqueous solutions prior to detection or from seawater. We now describe the use of IIP materials for selective removal of uranium from a typical synthetic nuclear power reactor effluent. The IIP materials were prepared for uranyl ion (imprint ion) by forming binary salicylaldoxime (SALO) or 4-vinylpyridine (VP) or ternary SALO-VP complexes in 2-methoxyethanol (porogen) and copolymerizing in the presence of styrene (monomer), divinylbenzene (cross-linking monomer), and 2,2'-azobisisobutyronitrile (initiator). The resulting materials were then ground and sieved to obtain unleached polymer particles. Leached IIP particles were obtained by leaching the imprint ions with 6.0 M HCl. Control polymer particles were also prepared analogously without the imprint ion. The IIP particles obtained with ternary complex alone gave quantitative removal of uranyl ion in the pH range 3.5-5.0 with as low as 0.08 g. The retention capacity of uranyl IIP particles was found to be 98.50 mg/g of polymer. The present study successfully demonstrates the feasibility of removing uranyl ions selectively in the range 5 microg - 300 mg present in 500 mL of synthetic nuclear power reactor effluent containing a host of other inorganic species.

  19. Uranyl Solvation by a Three-Dimensional Reference Interaction Site Model.

    PubMed

    Matveev, Alexei; Li, Bo; Rösch, Notker

    2015-08-13

    We report an implementation of the three-dimensional reference interaction site model (3D RISM) that in particular addresses the treatment of the long-range Coulomb field of charged species, represented by point charges and/or a distributed charge density. A comparison of 1D and 3D results for atomic ions demonstrates a reasonable accuracy, even for a moderate size of the unit cell and a moderate grid resolution. In an application to uranyl complexes with 4-6 explicit aqua ligands and an implicit bulk solvent modeled by RISM, we show that the 3D technique is not susceptible to the deficiencies of the 1D technique exposed in our previous work [Li, Matveev, Krüger, Rösch, Comp. Theor. Chem. 2015, 1051, 151]. The 3D method eliminates the artificial superposition of explicit aqua ligands and the RISM medium and predicts essentially the same values for uranyl and uranyl-water bond lengths as a state-of-the-art polarizable continuum model. With the first solvation shell treated explicitly, the observables are nearly independent of the order of the closure relationship used when solving the set of integral equations for the various distribution functions. Furthermore, we calculated the activation barrier of water exchange with a hybrid approach that combines the 3D RISM model for the bulk aqueous solvent and a quantum mechanical description (at the level of electronic density functional theory) of uranyl interacting with explicitly represented water molecules. The calculated result agrees very well with experiment and the best theoretical estimates. PMID:26167741

  20. Preparation of low-temperature sintered UO2 nanomaterials by radiolytic reduction of ammonium uranyl tricarbonate

    NASA Astrophysics Data System (ADS)

    Wang, Yongming; Chen, Qingde; Shen, Xinghai

    2016-10-01

    UO2 nanoparticles were successfully obtained from ammonium uranyl tricarbonate with high efficiency by γ-irradiation. More importantly, the as-prepared nanoparticles were stable in the irradiated mother solution exposed to air atmosphere. The purified UO2 powders could be sintered at 450-600 °C, much lower than the reported values (above 1700 °C) of bulk UO2. These advantages made this method promising in the production of UO2 nuclear fuels.

  1. Sub-Grid Reactive Diffusion and Apparent Uranyl Adsorption/Desorption Rates

    NASA Astrophysics Data System (ADS)

    Liu, C.; Kerisit, S.; Ma, R.; Zheng, C.; Zachara, J. M.

    2011-12-01

    Adsorption/desorption is an important process affecting contaminant fate and transport in subsurface sediments. This presentation will discuss the importance of sub-grid reactive diffusion in both intragranular and inter-grain domains that affect the apparent rates of uranyl adsorption/desorption at the macroscopic scale. Uranyl[U(VI)]-contaminated site at Hanford 300A where U(VI) resides in intragranular domains as surface-complexed species is used as an example in this presentation. Molecular dynamics calculations revealed that uranyl surface complexation reactions are a fast process with a first-order rate constant of 100 per second. Consequently U(VI) adsorption/desorption is treated as an equilibrium process. An equilibrium, Kd-based model, however, significantly over-predicted the historical migration of the uranyl plume at the site. Sub-grain pore-scale simulations and stirred-flow cell experiments indicated that the coupling of intragranular diffusion with surface complexation reactions decreased the apparent rate of U(VI) adsorption/desorption over 4 order of magnitude. The apparent rate of U(VI) adsorption/desorption decreased further over 1 order of magnitude due to the sub-grid pore-scale coupling of diffusive mass transfer and grain-scale U(VI) adsorption/desorption as revealed by column experiments and pore-scale simulations. Field-scale reactive transport models that incorporate the complexity of sub-grid reactive diffusion in the apparent rate of U(VI) adsorption/desorption were consistent with the slow migration of the U(VI) plume at the site.

  2. Criticality experiments and analysis of molybdenum reflected cylindrical uranyl fluoride water solution reactors

    NASA Technical Reports Server (NTRS)

    Fieno, D.; Fox, T.; Mueller, R.

    1972-01-01

    Clean criticality data were obtained from molybdenum-reflected cylindrical uranyl-fluoride-water solution reactors. Using ENDF/B molybdenum cross sections, a nine energy group two-dimensional transport calculation of a reflected reactor configuration predicted criticality to within 7 cents of the experimental value. For these reactors, it was necessary to compute the reflector resonance integral by a detailed transport calculation at the core-reflector interface volume in the energy region of the two dominant resonances of natural molybdenum.

  3. Analysis of Tank 43H Samples at the Conclusion of Uranyl Carbonate Addition

    SciTech Connect

    Oji, L.N.

    2002-10-15

    Tank 43H serves as the feed Tank to the 2H evaporator. In the months of July and August 2001, about 21,000 gallons of a depleted uranyl carbonate solution were added to Tank 43H and agitated with two Flygt mixers. The depleted uranium addition served to decrease the U-235 enrichment in the Tank 43H supernate so that the supernate could be evaporated with no risk of accumulating enriched uranium.

  4. Characterization of the Aqueous Uranyl-Silicate Complex Using X-Ray Absorption Spectroscopy and Ab Initio Modeling

    NASA Astrophysics Data System (ADS)

    Vu, M.; Massey, M.; Huang, P.

    2015-12-01

    The speciation of aqueous uranium ions is an important factor in predicting its mobility and fate in the environment. Two major controls on speciation are pH and the presence of complexing ligands. For the case of aqueous uranyl, UO22+(aq), some common complexes include uranyl-hydroxy, uranyl-carbonato, and uranyl-calcium-carbonato complexes, all of which differ in chemical reactivity and mobility. Uranyl-silicate complexes are also known but remain poorly characterized. In this work, we studied uranyl speciation in a series of aqueous solutions of 0.1 mM uranyl and 2 mM silicate with pH ranging from 4 to 7. Extended X-Ray Absorption Fine Structure (EXAFS) spectra of these samples were recorded at the Stanford Synchrotron Radiation Lightsource (SLAC National Accelerator Laboratory). Of particular note are the uranyl and silicate concentrations employed in our experiments, which are lower than conditions in previously reported EXAFS studies and approach conditions in natural groundwater systems. Preliminary analyses of EXAFS data indicate that uranyl speciation changes across the pH range, consistent with published thermodynamic data that suggest uranyl-silicate complexes may be important for pH ~ 5 and below, while uranyl-carbonato complexes become dominant at circumneutral pH. To guide the interpretation of the EXAFS data, molecular-scale simulations were carried out using density functional theory. We considered two classes of models: (i) hydrated clusters, and (ii) ab initio molecular dynamics simulations of 3D-periodic models involving uranyl and silicate in water. These calculations reveal that at pH ~ 5, the uranyl speciation is the [UO2(H2O)4H3SiO4]+ complex formed by the substitution of an equatorial uranyl water with a monodentate silicate ligand. The evidence from experiments and simulations provide a consistent picture for the uranyl-silicate complex, which may be important in the transport of uranyl in acidic, silicate-rich waters.

  5. Selective colorimetric and fluorescent quenching determination of uranyl ion via its complexation with curcumin

    NASA Astrophysics Data System (ADS)

    Zhu, Jing-Hui; Zhao, Xin; Yang, Jidong; Tan, Yu-Ting; Zhang, Lei; Liu, Shao-Pu; Liu, Zhong-Fang; Hu, Xiao-Li

    2016-04-01

    Under pH 4.0 HAc-NaAc buffer medium, curcumin alone possesses extraordinary weak fluorescence emission. Nevertheless, the introduction of Triton X-100 micelles can largely enhance the fluorescence intensity of curcumin. Uranyl ions can complex with micelles-capped curcumin, along with the slight red shift of curcumin fluorescence (about 1-7 nm), a clear decrement of absorbance (424 nm) and fluorescence (507 nm) intensities, and a distinct color change from bright yellow to orange. The fluorescence decrements (ΔF, 507 nm) are positively correlated to the amount of uranyl ions in the concentration range of 3.7 × 10- 6-1.4 × 10- 5 mol L- 1. The detection limit of this fluorescence quenching methods is 3.7 × 10- 6 mol L- 1, which is nearly 9000 times lower than the maximum allowable level in drinking water proposed by World Health Organization. Good selectivity is achieved because of a majority of co-existing substances (such as Ce4 +, La3 +, and Th4 +) do not affect the detection. The content of uranyl ions in tap water samples was determined by the proposed method with satisfactory results.

  6. Synthesis and X-ray diffraction study of new uranyl malonate and oxalate complexes with carbamide

    NASA Astrophysics Data System (ADS)

    Medvedkov, Ya. A.; Serezhkina, L. B.; Grigor'ev, M. S.; Serezhkin, V. N.

    2016-05-01

    Two new malonate-containing uranyl complexes with carbamide of the formulas [UO2(C3H2O4)( Urea)2] ( I) and [UO2(C3H2O4)( Urea)3] ( II), where Urea is carbamide, and one uranyl oxalate complex of the formula [UO2(C2O4)( Urea)3] ( III) were synthesized, and their crystals were studied by X-ray diffraction. The main structural units in crystals I are the electroneutral chains [UO2(C3H2O4)( Urea)2]∞ belonging to the crystal-chemical group AT 11 M 2 1 ( A = UO 2 2+ , T 11 = C3H2O 4 2- , M 1 = Urea) of uranyl complexes. Crystals II and III are composed of the molecular complexes [UO2( L)( Urea)3], where L = C3H2O 4 2- or C2O 4 2- , belonging to the crystal-chemical group AB 01 M 3 1 ( A = UO 2 2+ , B 01 = C3H2O 4 2- or C2O 4 2- , M 1 = Urea). The characteristic features of the packing of the uranium-containing complexes are discussed in terms of molecular Voronoi-Dirichlet polyhedra. The effect of the Urea: U ratio on the structure of uranium-containing structural units is considered.

  7. Determination of uranyl incorporation into biogenic manganese oxides using X-ray absorption spectroscopy and scattering

    USGS Publications Warehouse

    Webb, S.M.; Fuller, C.C.; Tebo, B.M.; Bargar, J.R.

    2006-01-01

    Biogenic manganese oxides are common and an important source of reactive mineral surfaces in the environment that may be potentially enhanced in bioremediation cases to improve natural attenuation. Experiments were performed in which the uranyl ion, UO22+ (U(VI)), at various concentrations was present during manganese oxide biogenesis. At all concentrations, there was strong uptake of U onto the oxides. Synchrotron-based extended X-ray absorption fine structure (EXAFS) spectroscopy and X-ray diffraction (XRD) studies were carried out to determine the molecular-scale mechanism by which uranyl is incorporated into the oxide and how this incorporation affects the resulting manganese oxide structure and mineralogy. The EXAFS experiments show that at low concentrations (2 mol % U, >4 ??M U(VI) in solution), the presence of U(VI) affects the stability and structure of the Mn oxide to form poorly ordered Mn oxide tunnel structures, similar to todorokite. EXAFS modeling shows that uranyl is present in these oxides predominantly in the tunnels of the Mn oxide structure in a tridentate complex. Observations by XRD corroborate these results. Structural incorporation may lead to more stable U(VI) sequestration that may be suitable for remediation uses. These observations, combined with the very high uptake capacity of the Mn oxides, imply that Mn-oxidizing bacteria may significantly influence dissolved U(VI) concentrations in impacted waters via sorption and incorporation into Mn oxide biominerals. ?? 2006 American Chemical Society.

  8. A cryogenic fluorescence spectroscopic study of uranyl carbonate, phosphate, and oxyhydroxide minerals

    SciTech Connect

    Wang, Zheming; Zachara, John M.; Liu, Chongxuan; Gassman, Paul L.; Felmy, Andrew R.; Clark, Sue B.

    2008-11-03

    In this work we have applied liquid-helium temperature (LHeT) time-resolved laser-induced fluorescence spectroscopy (TRLIF) to characterize a series of natural and synthetic minerals of uranium carbonate, phosphate and oxyhydroxides including rutherfordine, zellerite, liebigite, phosphuranylite, meta-autunite, meta-torbernite, uranyl phosphate, sodium-uranyl-phosphate, bequerelite, clarkeite, curite, schoepite and compregnacite, and compared their spectral characteristics among these minerals as well as our previously published data on uranyl silicates. For the carbonate minerals, the fluorescence spectra depend on the stoichiometry of the mineral. For the phosphate minerals the fluorescence spectra closely resemble each other despite the differences in their composition and structure. For all uranium oxyhydroxides, the fluorescence spectra are largely red-shifted as compared with those of the uranium carbonates and phosphates and their vibronic bands are broadened and less resolved. The much enhanced spectra resolution at LHeT allows more accurate calculation of the O=U=O symmetrical stretch frequency, ν1, corresponding to the average spacing of the vibronic peaks of the fluorescence spectra and the spectral origin as reflected by the position of the first vibronic band. It was found that both the average ν1 and λ1 values correlate well with the average basicity of the inorganic anion.

  9. XAFS investigation of polyamidoxime-bound uranyl contests the paradigm from small molecule studies

    SciTech Connect

    Mayes, Richard T.; Piechowicz, Marek; Lin, Zekai; Veith, Gabriel M.; Dai, Sheng; Lin, Wenbin; Abney, C. W.; Bryantsev, V. S.

    2015-11-12

    In this study, limited resource availability and population growth have motivated interest in harvesting valuable metals from unconventional reserves, but developing selective adsorbents for this task requires structural knowledge of metal binding environments. Amidoxime polymers have been identified as the most promising platform for large-scale extraction of uranium from seawater. However, despite more than 30 years of research, the uranyl coordination environment on these adsorbents has not been positively identified. We report the first XAFS investigation of polyamidoxime-bound uranyl, with EXAFS fits suggesting a cooperative chelating model, rather than the tridentate or η2 motifs proposed by small molecule and computational studies. Samples exposed to environmental seawater also display a feature consistent with a μ2-oxo-bridged transition metal in the uranyl coordination sphere, suggesting in situ formation of a specific binding site or mineralization of uranium on the polymer surface. These unexpected findings challenge several long-held assumptions and have significant implications for development of polymer adsorbents with high selectivity.

  10. XAFS investigation of polyamidoxime-bound uranyl contests the paradigm from small molecule studies

    DOE PAGES

    Mayes, Richard T.; Piechowicz, Marek; Lin, Zekai; Veith, Gabriel M.; Dai, Sheng; Lin, Wenbin; Abney, C. W.; Bryantsev, V. S.

    2015-11-12

    In this study, limited resource availability and population growth have motivated interest in harvesting valuable metals from unconventional reserves, but developing selective adsorbents for this task requires structural knowledge of metal binding environments. Amidoxime polymers have been identified as the most promising platform for large-scale extraction of uranium from seawater. However, despite more than 30 years of research, the uranyl coordination environment on these adsorbents has not been positively identified. We report the first XAFS investigation of polyamidoxime-bound uranyl, with EXAFS fits suggesting a cooperative chelating model, rather than the tridentate or η2 motifs proposed by small molecule and computationalmore » studies. Samples exposed to environmental seawater also display a feature consistent with a μ2-oxo-bridged transition metal in the uranyl coordination sphere, suggesting in situ formation of a specific binding site or mineralization of uranium on the polymer surface. These unexpected findings challenge several long-held assumptions and have significant implications for development of polymer adsorbents with high selectivity.« less

  11. Regulation of Nitrate Assimilation and Nitrate Respiration in Aerobacter aerogenes

    PubMed Central

    Van 'T Riet, J.; Stouthamer, A. H.; Planta, R. J.

    1968-01-01

    The influence of growth conditions on assimilatory and respiratory nitrate reduction in Aerobacter aerogenes was studied. The level of nitrate reductase activity in cells, growing in minimal medium with nitrate as the sole nitrogen source, was much lower under aerobic than anaerobic conditions. Further, the enzyme of the aerobic cultures was very sensitive to sonic disintegration, as distinct from the enzyme of anaerobic cultures. When a culture of A. aerogenes was shifted from anaerobic growth in minimal medium with nitrate and NH4+ to aerobiosis in the same medium, but without NH4+, the production of nitrite stopped instantaneously and the total activity of nitrate reductase decreased sharply. Moreover, there was a lag in growth of about 3 hr after such a shift. After resumption of growth, the total enzymatic activity increased again slowly and simultaneously became gradually sensitive to sonic disintegration. These findings show that oxygen inactivates the anaerobic nitrate reductase and represses its further formation; only after a de novo synthesis of nitrate reductase with an assimilatory function will growth be resumed. The enzyme in aerobic cultures was not significantly inactivated by air, only by pure oxygen. The formation of the assimilatory enzyme complex was repressed, however, by NH4+, under both aerobic and anaerobic conditions. The results indicate that the formation of the assimilatory enzyme complex and that of the respiratory enzyme complex are regulated differently. We suggest that both complexes have a different composition, but that the nitrate reductase in both cases is the same protein. PMID:5726295

  12. Gas-phase reactions of molecular oxygen with uranyl(V) anionic complexes-synthesis and characterization of new superoxides of uranyl(VI).

    PubMed

    Lucena, Ana F; Carretas, José M; Marçalo, Joaquim; Michelini, Maria C; Gong, Yu; Gibson, John K

    2015-04-16

    Gas-phase complexes of uranyl(V) ligated to anions X(-) (X = F, Cl, Br, I, OH, NO3, ClO4, HCO2, CH3CO2, CF3CO2, CH3COS, NCS, N3), [UO2X2](-), were produced by electrospray ionization and reacted with O2 in a quadrupole ion trap mass spectrometer to form uranyl(VI) anionic complexes, [UO2X2(O2)](-), comprising a superoxo ligand. The comparative rates for the oxidation reactions were measured, ranging from relatively fast [UO2(OH)2](-) to slow [UO2I2](-). The reaction rates of [UO2X2](-) ions containing polyatomic ligands were significantly faster than those containing the monatomic halogens, which can be attributed to the greater number of vibrational degrees of freedom in the polyatomic ligands to dissipate the energy of the initial O2-association complexes. The effect of the basicity of the X(-) ligands was also apparent in the relative rates for O2 addition, with a general correlation between increasing ligand basicity and O2-addition efficiency for polyatomic ligands. Collision-induced dissociation of the superoxo complexes showed in all cases loss of O2 to form the [UO2X2](-) anions, indicating weaker binding of the O2(-) ligand compared to the X(-) ligands. Density functional theory computations of the structures and energetics of selected species are in accord with the experimental observations.

  13. Synergistic cytotoxicity and DNA strand breaks in cells and plasmid DNA exposed to uranyl acetate and ultraviolet radiation

    PubMed Central

    Wilson, Janice; Zuniga, Mary C.; Yazzie, Filbert; Stearns, Diane M.

    2015-01-01

    Depleted uranium (DU) has a chemical toxicity that is independent of its radioactivity. The purpose of this study was to explore the photoactivation of uranyl ion by ultraviolet (UV) radiation as a chemical mechanism of uranium genotoxicity. The ability of UVB (302 nm) and UVA (368 nm) radiation to photoactivate uranyl ion to produce single strand breaks was measured in pBR322 plasmid DNA, and the presence of adducts and apurinic/apyrimidinic sites that could be converted to single strand breaks by heat and piperidine was analyzed. Results showed that DNA lesions in plasmid DNA exposed to UVB- or UVA-activated DU were only slightly heat reactive, but were piperidine sensitive. The cytotoxicity of UVB-activated uranyl ion was measured in repair-proficient and repair-deficient Chinese hamster ovary cells and human keratinocyte HaCaT cells. The cytotoxicity of co-exposures of uranyl ion and UVB radiation was dependent on the order of exposure and was greater than co-exposures of arsenite and UVB radiation. Uranyl ion and UVB radiation were synergistically cytotoxic in cells, and cells exposed to photoactivated DU required different DNA repair pathways than cells exposed to non-photoactivated DU. This study contributes to our understanding of the DNA lesions formed by DU, as well as their repair. Results suggest that excitation of uranyl ion by UV radiation can provide a pathway for uranyl ion to be chemically genotoxic in populations with dermal exposures to uranium and UV radiation, which would make skin an overlooked target organ for uranium exposures. PMID:24832689

  14. Synergistic cytotoxicity and DNA strand breaks in cells and plasmid DNA exposed to uranyl acetate and ultraviolet radiation.

    PubMed

    Wilson, Janice; Zuniga, Mary C; Yazzie, Filbert; Stearns, Diane M

    2015-04-01

    Depleted uranium (DU) has a chemical toxicity that is independent of its radioactivity. The purpose of this study was to explore the photoactivation of uranyl ion by ultraviolet (UV) radiation as a chemical mechanism of uranium genotoxicity. The ability of UVB (302 nm) and UVA (368 nm) radiation to photoactivate uranyl ion to produce single strand breaks was measured in pBR322 plasmid DNA, and the presence of adducts and apurinic/apyrimidinic sites that could be converted to single strand breaks by heat and piperidine was analyzed. Results showed that DNA lesions in plasmid DNA exposed to UVB- or UVA-activated DU were only slightly heat reactive, but were piperidine sensitive. The cytotoxicity of UVB-activated uranyl ion was measured in repair-proficient and repair-deficient Chinese hamster ovary cells and human keratinocyte HaCaT cells. The cytotoxicity of co-exposures of uranyl ion and UVB radiation was dependent on the order of exposure and was greater than co-exposures of arsenite and UVB radiation. Uranyl ion and UVB radiation were synergistically cytotoxic in cells, and cells exposed to photoactivated DU required different DNA repair pathways than cells exposed to non-photoactivated DU. This study contributes to our understanding of the DNA lesions formed by DU, as well as their repair. Results suggest that excitation of uranyl ion by UV radiation can provide a pathway for uranyl ion to be chemically genotoxic in populations with dermal exposures to uranium and UV radiation, which would make skin an overlooked target organ for uranium exposures.

  15. Structural evolution of a uranyl peroxide nano-cage fullerene: U60, at elevated pressures

    NASA Astrophysics Data System (ADS)

    Turner, K. M.; Lin, Y.; Zhang, F.; McGrail, B.; Burns, P. C.; Mao, W. L.; Ewing, R. C.

    2015-12-01

    U60 is a uranyl peroxide nano-cage that adopts a highly symmetric fullerene topology; it is topologically identical to C60. Several studies on the aqueous-phase of U60 clusters, [UO2(O2)(OH)]6060-, have shown its persistence in complex solutions and over lengthy time scales. Peroxide enhances corrosion of nuclear fuel in a reactor accident-uranyl peroxides often form near contaminated sites. U60 (Fm-3) crystallizes with approximate formula: Li68K12(OH)20[UO2(O2)(OH)]60(H2O)310. Here, we have used the diamond anvil cell (DAC) to examine U60 to understand the stability of this cluster at high pressures. We used a symmetric DAC with 300 μm culet diamonds and two different pressure-transmitting media: a mixture of methanol+ethanol and silicone oil. Using a combination of in situ Raman spectroscopy and synchrotron XRD, and electrospray ionization mass spectroscopy (ESI-MS) ex situ, we have determined the pressure-induced evolution of U60. Crystalline U60 undergoes an irreversible phase transition to a tetragonal structure at 4.1 GPa, and irreversibly amorphizes at 13 GPa. The amorphous phase likely consists of clusters of U60. Above 15 GPa, the U60 cluster is irreversibly destroyed. ESI-MS shows that this phase consists of species that likely have between 10-20 uranium atoms. Raman spectroscopy complements the diffraction measurements. U60 shows two dominant vibrational modes: a symmetric stretch of the uranyl U-O triple bond (810 cm-1), and a symmetric stretch of the U-O2-U peroxide bond (820 cm-1). As pressure is increased, these modes shift to higher wavenumbers, and overlap at 4 GPa. At 15 GPa, their intensity decreases below detection. These experiments reveal several novel behaviors including a new phase of U60. Notably, the amorphization of U60 occurs before the collapse of its cluster topology. This is different from the behavior of solvated C60 at high pressure, which maintains a hcp structure up to 30 GPa, while the clusters disorder. These results suggest

  16. Some History of Nitrates

    NASA Astrophysics Data System (ADS)

    Barnum, Dennis W.

    2003-12-01

    The history of saltpeter is an interesting combination of chemistry, world trade, technology, politics, and warfare. Originally it was obtained from the dirt floors of stables, sheep pens, pigeon houses, caverns, and even peasants' cottages; any place manure and refuse accumulated in soil under dry conditions. When these sources became inadequate to meet demand it was manufactured on saltpeter plantations, located in dry climates, where piles of dirt, limestone, and manure were allowed to stand for three to five years while soil microbes oxidized the nitrogen to nitrate—an example of early bioengineering. Extensive deposits of sodium nitrate were mined in the Atacama Desert in northern Chile from 1830 until the mid 1920s when the mines were displaced by the Haber Ostwald process.

  17. Nitrate reductase from Rhodopseudomonas sphaeroides.

    PubMed Central

    Kerber, N L; Cardenas, J

    1982-01-01

    The facultative phototroph Rhodopseudomonas sphaeroides DSM158 was incapable of either assimilating or dissimilating nitrate, although the organism could reduce it enzymatically to nitrite either anaerobically in the light or aerobically in the dark. Reduction of nitrate was mediated by a nitrate reductase bound to chromatophores that could be easily solubilized and functioned with chemically reduced viologens or photochemically reduced flavins as electron donors. The enzyme was solubilized, and some of its kinetic and molecular parameters were determined. It seemed to be nonadaptive, ammonia did not repress its synthesis, and its activity underwent a rapid decline when the cells entered the stationary growth phase. Studies with inhibitors and with metal antagonists indicated that molybdenum and possibly iron participate in the enzymatic reduction of nitrate. The conjectural significance of this nitrate reductase in phototrophic bacteria is discussed. PMID:6978883

  18. TREATMENT OF AMMONIUM NITRATE SOLUTIONS

    DOEpatents

    Boyer, T.W.; MacHutchin, J.G.; Yaffe, L.

    1958-06-10

    The treatment of waste solutions obtained in the processing of neutron- irradiated uranium containing fission products and ammonium nitrate is described. The object of this process is to provide a method whereby the ammonium nitrate is destroyed and removed from the solution so as to permit subsequent concentration of the solution.. In accordance with the process the residual nitrate solutions are treated with an excess of alkyl acid anhydride, such as acetic anhydride. Preferably, the residual nitrate solution is added to an excess of the acetic anhydride at such a rate that external heat is not required. The result of this operation is that the ammonium nitrate and acetic anhydride react to form N/sub 2/ O and acetic acid.

  19. Mortality of nitrate fertiliser workers.

    PubMed

    Al-Dabbagh, S; Forman, D; Bryson, D; Stratton, I; Doll, R

    1986-08-01

    An epidemiological cohort study was conducted to investigate the mortality patterns among a group of workers engaged in the production of nitrate based fertilisers. This study was designed to test the hypothesis that individuals exposed to high concentrations of nitrates might be at increased risk of developing cancers, particularly gastric cancer. A total of 1327 male workers who had been employed in the production of fertilisers between 1946 and 1981 and who had been occupationally exposed to nitrates for at least one year were followed up until 1 March 1981. In total, 304 deaths were observed in this group and these were compared with expected numbers calculated from mortality rates in the northern region of England, where the factory was located. Analysis was also carried out separately for a subgroup of the cohort who had been heavily exposed to nitrates--that is, working in an environment likely to contain more than 10 mg nitrate/m3 for a year or longer. In neither the entire cohort nor the subgroup was any significant excess observed for all causes of mortality or for mortality from any of five broad categories of cause or from four specific types of cancer. A small excess of lung cancer was noted more than 20 years after first exposure in men heavily exposed for more than 10 years. That men were exposed to high concentrations of nitrate was confirmed by comparing concentrations of nitrates in the saliva of a sample of currently employed men with control men, employed at the same factory but not in fertiliser production. The men exposed to nitrate had substantially raised concentrations of nitrate in their saliva compared with both controls within the industry and with men in the general population and resident nearby. The results of this study therefore weight against the idea that exposure to nitrates in the environment leads to the formation in vivo of material amounts of carcinogens. PMID:3015194

  20. Omega-3 fatty acid deficiency does not alter the effects of chronic fluoxetine treatment on central serotonin turnover or behavior in the forced swim test in female rats.

    PubMed

    McNamara, Robert K; Able, Jessica A; Liu, Yanhong; Jandacek, Ronald; Rider, Therese; Tso, Patrick; Lipton, Jack W

    2013-12-01

    While translational evidence suggests that long-chain omega-3 fatty acid status is positively associated with the efficacy of selective serotonin reuptake inhibitor drugs, the neurochemical mechanisms mediating this interaction are not known. Here, we investigated the effects of dietary omega-3 (n-3) fatty acid insufficiency on the neurochemical and behavioral effects of chronic fluoxetine (FLX) treatment. Female rats were fed diets with (CON, n=56) or without (DEF, n=40) the n-3 fatty acids during peri-adolescent development (P21-P90), and one half of each group was administered FLX (10mg/kg/day) for 30days (P60-P90) prior to testing. In adulthood (P90), regional brain serotonin (5-HT) and 5-hydroxyindoleacetic (5-HIAA) concentrations, presynaptic markers of 5-HT neurotransmission, behavioral responses in the forced swim test (FST), and plasma FLX and norfluoxetine (NFLX) concentrations were investigated. Peri-adolescent n-3 insufficiency led to significant reductions in cortical docosahexaenoic acid (DHA, 22:6n-3) composition in DEF (-25%, p≤0.0001) and DEF+FLX (-28%, p≤0.0001) rats. Untreated DEF rats exhibited significantly lower regional 5-HIAA/5-HT ratios compared with untreated CON rats, but exhibited similar behavioral responses in the FST. In both CON and DEF rats, chronic FLX treatment similarly and significantly decreased 5-HIAA concentrations and the 5-HIAA/5-HT ratio in the hypothalamus, hippocampus, and nucleus accumbens, brainstem tryptophan hydroxylase-2 mRNA expression, and immobility in the FST. While the FLX-induced reduction in 5-HIAA concentrations in the prefrontal cortex was significantly blunted in DEF rats, the reduction in the 5-HIAA/5-HT ratio was similar to CON rats. Although plasma FLX and NFLX levels were not significantly different in DEF and CON rats, the NFLX/FLX ratio was significantly lower in DEF+FLX rats. These preclinical data demonstrate that n-3 fatty acid deficiency does not significantly reduce the effects of chronic

  1. Omega-3 Fatty Acid Deficiency Does Not Alter the Effects of Chronic Fluoxetine Treatment on Central Serotonin Turnover or Behavior in the Forced Swim Test in Female Rats

    PubMed Central

    McNamara, Robert K.; Able, Jessica A.; Liu, Yanhong; Jandacek, Ronald; Rider, Therese; Tso, Patrick; Lipton, Jack W.

    2013-01-01

    While translational evidence suggests that long-chain omega-3 fatty acid status is positively associated with the efficacy of selective serotonin reuptake inhibitor drugs, the neurochemical mechanisms mediating this interaction are not known. Here we investigated the effects of dietary omega-3 (n-3) fatty acid insufficiency on the neurochemical and behavioral effects of chronic fluoxetine (FLX) treatment. Female rats were fed diets with (CON, n=56) or without (DEF, n=40) the n-3 fatty acids during peri-adolescent development (P21-P90), and one half of each group were administered FLX (10 mg/kg/d) for 30 d (P60-P90) prior to testing. In adulthood (P90), regional brain serotonin (5-HT) and 5-hydroxyindoleacetic (5-HIAA) concentrations, presynaptic markers of 5-HT neurotransmission, behavioral responses in the forced swim test (FST), and plasma FLX and norfluoxetine (NFLX) concentrations were investigated. Peri-adolescent n-3 insufficiency led to significant reductions in cortical docosahexaenoic acid (DHA, 22:6n-3) composition in DEF (−25%, p≤0.0001) and DEF+FLX (−28%, p≤0.0001) rats. Untreated DEF rats exhibited significantly lower regional 5-HIAA/5-HT ratios compared with untreated CON rats, but exhibited similar behavioral responses in the FST. In both CON and DEF rats, chronic FLX treatment similarly and significantly decreased 5-HIAA concentrations and the 5-HIAA/5-HT ratio in the hypothalamus, hippocampus, and nucleus accumbens, brainstem tryptophan hydroxylase-2 mRNA expression, and immobility in the FST. While the FLX-induced reduction in 5-HIAA concentrations in the prefrontal cortex was significantly blunted in DEF rats, the reduction in the 5-HIAA/5-HT ratio was similar to CON rats. Although plasma FLX and NFLX levels were not significantly different in DEF and CON rats, the NFLX/FLX ratio was significantly lower in DEF+FLX rats. These preclinical data demonstrate that n-3 fatty acid deficiency does not significantly reduce the effects of chronic

  2. Nitrate Transport System in Neurospora crassa

    PubMed Central

    Schloemer, Robert H.; Garrett, Reginald H.

    1974-01-01

    Nitrate uptake in Neurospora crassa has been investigated under various conditions of nitrogen nutrition by measuring the rate of disappearance of nitrate from the medium and by determining mycelial nitrate accumulation. The nitrate transport system is induced by either nitrate or nitrite, but is not present in mycelia grown on ammonia or Casamino Acids. The appearance of nitrate uptake activity is prevented by cycloheximide, puromycin, or 6-methyl purine. The induced nitrate transport system displays a Km for nitrate of 0.25 mM. Nitrate uptake is inhibited by metabolic poisons such as 2,4-dinitrophenol, cyanide, and antimycin A. Furthermore, mycelia can concentrate nitrate 50-fold. Ammonia and nitrite are non-competitive inhibitors with respect to nitrate, with Ki values of 0.13 and 0.17 mM, respectively. Ammonia does not repress the formation of the nitrate transport system. In contrast, the nitrate uptake system is repressed by Casamino Acids. All amino acids individually prevent nitrate accumulation, with the exception of methionine, glutamine, and alanine. The influence of nitrate reduction and the nitrate reductase protein on nitrate transport was investigated in wild-type Neurospora lacking a functional nitrate reductase and in nitrate non-utilizing mutants, nit-1, nit-2, and nit-3. These mycelia contain an inducible nitrate transport system which displays the same characteristics as those found in the wild-type mycelia having the functional nitrate reductase. These findings suggest that nitrate transport is not dependent upon nitrate reduction and that these two processes are separate events in the assimilation of nitrate. PMID:4274457

  3. Nitrate concentrations under irrigated agriculture

    USGS Publications Warehouse

    Zaporozec, A.

    1983-01-01

    In recent years, considerable interest has been expressed in the nitrate content of water supplies. The most notable toxic effect of nitrate is infant methemoglobinemia. The risk of this disease increases significantly at nitrate-nitrogen levels exceeding 10 mg/l. For this reason, this concentration has been established as a limit for drinking water in many countries. In natural waters, nitrate is a minor ionic constituent and seldom accounts for more than a few percent of the total anions. However, nitrate in a significant concentration may occur in the vicinity of some point sources such as septic tanks, manure pits, and waste-disposal sites. Non-point sources contributing to groundwater pollution are numerous and a majority of them are related to agricultural activities. The largest single anthropogenic input of nitrate into the groundwater is fertilizer. Even though it has not been proven that nitrogen fertilizers are responsible for much of nitrate pollution, they are generally recognized as the main threat to groundwater quality, especially when inefficiently applied to irrigated fields on sandy soils. The biggest challenge facing today's agriculture is to maintain the balance between the enhancement of crop productivity and the risk of groundwater pollution. ?? 1982 Springer-Verlag New York Inc.

  4. Selective recognition of uranyl ions from bulk of thorium(iv) and lanthanide(iii) ions by tetraalkyl urea: a combined experimental and quantum chemical study.

    PubMed

    Vats, Bal Govind; Das, Debasish; Sadhu, Biswajit; Kannan, S; Pius, I C; Noronha, D M; Sundararajan, Mahesh; Kumar, Mukesh

    2016-06-21

    The selective separation of uranyl ions from an aqueous solution is one of the most important criteria for sustainable nuclear energy production. We report herein a known, but unexplored extractant, tetraalkyl urea, which shows supreme selectivity for uranium in the presence of interfering thorium and other lanthanide ions from a nitric acid medium. The structural characterization of the uranyl complex (UO2X2·2L, where X = NO3(-), Cl(-) and Br(-)) by IR, NMR and single crystal X-ray diffraction provides insight into the strong interaction between the uranyl ion and the ligand. The origin of this supreme selectivity for uranyl ions is further supported by electronic structure calculations. Uranyl binding with the extractant is thermodynamically more favourable when compared to thorium and the selectivity is achieved through a combination of electronic and steric effects. PMID:27241102

  5. Selective recognition of uranyl ions from bulk of thorium(iv) and lanthanide(iii) ions by tetraalkyl urea: a combined experimental and quantum chemical study.

    PubMed

    Vats, Bal Govind; Das, Debasish; Sadhu, Biswajit; Kannan, S; Pius, I C; Noronha, D M; Sundararajan, Mahesh; Kumar, Mukesh

    2016-06-21

    The selective separation of uranyl ions from an aqueous solution is one of the most important criteria for sustainable nuclear energy production. We report herein a known, but unexplored extractant, tetraalkyl urea, which shows supreme selectivity for uranium in the presence of interfering thorium and other lanthanide ions from a nitric acid medium. The structural characterization of the uranyl complex (UO2X2·2L, where X = NO3(-), Cl(-) and Br(-)) by IR, NMR and single crystal X-ray diffraction provides insight into the strong interaction between the uranyl ion and the ligand. The origin of this supreme selectivity for uranyl ions is further supported by electronic structure calculations. Uranyl binding with the extractant is thermodynamically more favourable when compared to thorium and the selectivity is achieved through a combination of electronic and steric effects.

  6. MCNP5 CALCULATIONS REPLICATING ARH-600 NITRATE DATA

    SciTech Connect

    FINFROCK SH

    2011-10-25

    This report serves to extend the previous document: 'MCNP Calculations Replicating ARH-600 Data' by replicating the nitrate curves found in ARH-600. This report includes the MCNP models used, the calculated critical dimension for each analyzed parameter set, and the resulting data libraries for use with the CritView code. As with the ARH-600 data, this report is not meant to replace the analysis of the fissile systems by qualified criticality personnel. The M CNP data is presented without accounting for the statistical uncertainty (although this is typically less than 0.001) or bias and, as such, the application of a reasonable safety margin is required. The data that follows pertains to the uranyl nitrate and plutonium nitrate spheres, infinite cylinders, and infinite slabs of varying isotopic composition, reflector thickness, and molarity. Each of the cases was modeled in MCNP (version 5.1.40), using the ENDF/B-VI cross section set. Given a molarity, isotopic composition, and reflector thickness, the fissile concentration and diameter (or thicknesses in the case of the slab geometries) were varied. The diameter for which k-effective equals 1.00 for a given concentration could then be calculated and graphed. These graphs are included in this report. The pages that follow describe the regions modeled, formulas for calculating the various parameters, a list of cross-sections used in the calculations, a description of the automation routine and data, and finally the data output. The data of most interest are the critical dimensions of the various systems analyzed. This is presented graphically, and in table format, in Appendix B. Appendix C provides a text listing of the same data in a format that is compatible with the CritView code. Appendices D and E provide listing of example Template files and MCNP input files (these are discussed further in Section 4). Appendix F is a complete listing of all of the output data (i.e., all of the analyzed dimensions and the

  7. Correlation between stabilities of uranyl ion complexes with various monocarboxylic acids and Hammett-Taft substituent constants

    SciTech Connect

    Poluektov, N.S.; Perfil'ev, V.A.; Meshkova, S.B.; Mishchenko, V.T.

    1987-01-01

    A correlation has been observed between the stabilities of uranyl ion complexes (1:1 composition) and the substituent inductive constants in formic and acetic acid derivatives. For substituents which are not directly involved in couples formation the parameters of the Hammett-Taft equation log K/sub 1/ = A + B have the following values: A = 1.311, B = -2.360. For substituents which form a coordination bond with the uranyl ion, A = 7.0077 and B = - 17.321. In the case of complexes formed between the uranyl ion and salicylic acid and its derivatives, there is a correlation between complex stability and sigma/sub m/ and sigma/sub p/ substituent constants for the meta- and para-positions, respectively (A = 12.72, B = -4.41).

  8. Computer simulation of uranyl uptake by the rough lipopolysaccharide membrane of Pseudomonas aeruginosa.

    PubMed

    Lins, Roberto D; Vorpagel, Erich R; Guglielmi, Matteo; Straatsma, T P

    2008-01-01

    Heavy metal environmental contaminants cannot be destroyed but require containment, preferably in concentrated form, in a solid or immobile form for recycling or final disposal. Microorganisms are able to take up and deposit high levels of contaminant metals, including radioactive metals such as uranium and plutonium, into their cell wall. Consequently, these microbial systems are of great interest as the basis for potential environmental bioremediation technologies. The outer membranes of Gram-negative microbes are highly nonsymmetric and exhibit a significant electrostatic potential gradient across the membrane. This gradient has a significant effect on the uptake and transport of charged and dipolar compounds. However, the effectiveness of microbial systems for environmental remediation will depend strongly on specific properties that determine the uptake of targeted contaminants by a particular cell wall. To aid in the design of microbial remediation technologies, knowledge of the factors that determine the affinity of a particular bacterial outer membrane for the most common ionic species found in contaminated soils and groundwater is of great importance. Using our previously developed model for the lipopolysaccharide (LPS) membrane of Pseudomonas aeruginosa, this work presents the potentials of mean force as the estimate of the free energy profile for uptake of sodium, calcium, chloride, uranyl ions, and a water molecule by the bacterial LPS membrane. A compatible classical parameter set for uranyl has been developed and validated. Results show that the uptake of uranyl is energetically a favorable process relative to the other ions studied. At neutral pH, this nuclide is shown to be retained on the surface of the LPS membrane through chelation with the carboxyl and hydroxyl groups located in the outer core.

  9. Transformation of human osteoblast cells to the tumorigenic phenotype by depleted uranium-uranyl chloride.

    PubMed Central

    Miller, A C; Blakely, W F; Livengood, D; Whittaker, T; Xu, J; Ejnik, J W; Hamilton, M M; Parlette, E; John, T S; Gerstenberg, H M; Hsu, H

    1998-01-01

    Depleted uranium (DU) is a dense heavy metal used primarily in military applications. Although the health effects of occupational uranium exposure are well known, limited data exist regarding the long-term health effects of internalized DU in humans. We established an in vitro cellular model to study DU exposure. Microdosimetric assessment, determined using a Monte Carlo computer simulation based on measured intracellular and extracellular uranium levels, showed that few (0.0014%) cell nuclei were hit by alpha particles. We report the ability of DU-uranyl chloride to transform immortalized human osteoblastic cells (HOS) to the tumorigenic phenotype. DU-uranyl chloride-transformants are characterized by anchorage-independent growth, tumor formation in nude mice, expression of high levels of the k-ras oncogene, reduced production of the Rb tumor-suppressor protein, and elevated levels of sister chromatid exchanges per cell. DU-uranyl chloride treatment resulted in a 9.6 (+/- 2.8)-fold increase in transformation frequency compared to untreated cells. In comparison, nickel sulfate resulted in a 7.1 (+/- 2.1)-fold increase in transformation frequency. This is the first report showing that a DU compound caused human cell transformation to the neoplastic phenotype. Although additional studies are needed to determine if protracted DU exposure produces tumors in vivo, the implication from these in vitro results is that the risk of cancer induction from internalized DU exposure may be comparable to other biologically reactive and carcinogenic heavy-metal compounds (e.g., nickel). Images Figure 1 Figure 2 Figure 3 PMID:9681973

  10. Computer Simulation of Uranyl Uptake by the Rough Lipopolysaccharide Membrane of Pseudomonas aeruginosa

    SciTech Connect

    Lins, Roberto D.; Vorpagel, Erich R.; Guglielmi, Matteo; Straatsma, TP

    2008-01-01

    Heavy metal environmental contaminants cannot be destroyed but require containment, preferably in concentrated form, in a solid or immobile form for recycling or final disposal. Microorganisms are able to take up and deposit high levels of contaminant metals, including radioactive metals such as uranium and plutonium, into their cell wall. Consequently, these microbial systems are of great interest as the basis for potential environmental bioremediation technologies. The outer membranes of Gram-negative microbes are highly non-symmetric and exhibit a significant electrostatic potential gradient across the membrane. This gradient has a significant effect on the uptake and transport of charged and dipolar compounds. However, the effectiveness of microbial systems for environmental remediation will depend strongly on specific properties that determine the uptake of targeted contaminants by a particular cell wall. To aid in the design of microbial remediation technologies, knowledge of the factors that determine the affinity of a particular bacterial outer membrane for the most common ionic species found in contaminated soils and groundwater is of great importance. Using our previously developed model for the lipopolisaccharide (LPS) membrane of Pseudomonas aeruginosa, this work presents the potentials of mean force as the estimate of the free energy profile for uptake of sodium, calcium, chloride, uranyl ions and a water molecule by the bacterial LPS membrane. A compatible classical parameter set for uranyl has been developed and validated. Results show that the uptake of uranyl is energetically a favorable process relative to the other ions studied. At neutral pH, this nuclide is shown to be retained on the surface of the LPS membrane through chelation with the carboxyl and hydroxyl groups located in the outer-core.

  11. Computer simulation of uranyl uptake by the rough lipopolysaccharide membrane of Pseudomonas aeruginosa.

    PubMed

    Lins, Roberto D; Vorpagel, Erich R; Guglielmi, Matteo; Straatsma, T P

    2008-01-01

    Heavy metal environmental contaminants cannot be destroyed but require containment, preferably in concentrated form, in a solid or immobile form for recycling or final disposal. Microorganisms are able to take up and deposit high levels of contaminant metals, including radioactive metals such as uranium and plutonium, into their cell wall. Consequently, these microbial systems are of great interest as the basis for potential environmental bioremediation technologies. The outer membranes of Gram-negative microbes are highly nonsymmetric and exhibit a significant electrostatic potential gradient across the membrane. This gradient has a significant effect on the uptake and transport of charged and dipolar compounds. However, the effectiveness of microbial systems for environmental remediation will depend strongly on specific properties that determine the uptake of targeted contaminants by a particular cell wall. To aid in the design of microbial remediation technologies, knowledge of the factors that determine the affinity of a particular bacterial outer membrane for the most common ionic species found in contaminated soils and groundwater is of great importance. Using our previously developed model for the lipopolysaccharide (LPS) membrane of Pseudomonas aeruginosa, this work presents the potentials of mean force as the estimate of the free energy profile for uptake of sodium, calcium, chloride, uranyl ions, and a water molecule by the bacterial LPS membrane. A compatible classical parameter set for uranyl has been developed and validated. Results show that the uptake of uranyl is energetically a favorable process relative to the other ions studied. At neutral pH, this nuclide is shown to be retained on the surface of the LPS membrane through chelation with the carboxyl and hydroxyl groups located in the outer core. PMID:18067253

  12. Synthesis and structures of new uranyl malonate complexes with carbamide derivatives

    SciTech Connect

    Serezhkina, L. B.; Grigor’ev, M. S.; Medvedkov, Ya. A.; Serezhkin, V. N.

    2015-09-15

    Crystals of new malonate-containing uranyl complexes [UO{sub 2}(C{sub 3}H{sub 2}O{sub 4})(Imon)(H{sub 2}O)] (I) and [UO{sub 2}(C{sub 3}H{sub 2}O4)(Meur){sub 3}] (II), where Imon is imidazolidin-2-one (ethylenecarbamide) and Meur is methyl-carbamide, have been synthesized and studied by X-ray diffraction. Both compounds crystallize in the monoclinic system with the following unit-cell parameters (at 100 K): a = 11.1147(10) Å, b = 6.9900(6) Å, c = 14.4934(12) Å, β = 92.042(2)°, V = 1125.30(17) Å{sup 3}, sp. gr. P2{sub 1}/n, Z = 4, R{sub 1} = 0.0398 (I); a = 16.6613(5) Å, b = 9.5635(3) Å, c = 22.9773(6) Å, β = 103.669(2)°, V = 3557.51(18) Å{sup 3}, sp. gr. C2/c, Z = 8, R{sub 1} = 0.0207 (II). The crystals are composed of electroneutral chains [UO{sub 2}(C{sub 3}H{sub 2}O{sub 4})(Imon)(H{sub 2}O)] and mononuclear groups [UO{sub 2}(C{sub 3}H{sub 2}O{sub 4})(Meur){sub 3}] as the structural units belonging to the crystal-chemical groups AT{sup 11}M{sub 2}{sup 1} and AB{sup 01}M{sub 3}{sup 1} (A =UO{sub 2}{sup 2+}, T{sup 11} and B{sup 01} = C{sub 3}H{sub 2}, M{sup 1} = Imon, H{sub 2}O, or Meur), respectively, of uranyl complexes. The packing modes of the uranyl-containing complexes were analyzed by the method of molecular Voronoi—Dirichlet polyhedra.

  13. Speciation Studies of Metals in Trace Concentrations: The Mononuclear Uranyl(VI) Hydroxo Complexes.

    PubMed

    Drobot, Björn; Bauer, Anne; Steudtner, Robin; Tsushima, Satoru; Bok, Frank; Patzschke, Michael; Raff, Johannes; Brendler, Vinzenz

    2016-04-01

    A direct luminescence spectroscopic experimental setup for the determination of complex stability constants of mononuclear uranyl(VI) hydrolysis species is presented. The occurrence of polynuclear species is prevented by using a low uranyl(VI) concentration of 10–8 M (2.4 ppb). Time-resolved laser-induced fluorescence spectra were recorded in the pH range from 3 to 10.5. Deconvolution with parallel factor analysis (PARAFAC) resulted in three hydrolysis complexes. A tentative assignment was based on thermodynamic calculations: UO22+, UO2(OH)+, UO2(OH)2, UO2(OH)3–. An implementation of a Newton–Raphson algorithm into PARAFAC allowed a direct extraction of complex stability constants during deconvolution yielding log(β1M,1°C)1:1 = −4.6, log(β1M,1°C)1:2 = −12.2, log(β1M,1°C)1:3 = −22.3. Extrapolation to standard conditions gave log(β0)1:1 = −3.9, log(β0)1:2 = −10.9, and log(β0)1:3 = −20.7. Luminescence characteristics (band position, lifetime) of the individual mononuclear hydroxo species were derived to serve as a reference data set for further investigations. A correlation of luminescence spectroscopic features with Raman frequencies was demonstrated for the mononuclear uranyl(VI) hydroxo complexes for the first time. Thereby a signal-to-structure correlation was achieved and the complex assignment validated. PMID:26977534

  14. Synthesis, characterization and photo luminescence studies of uranyl doped SrBPO{sub 5}

    SciTech Connect

    Rout, Annapurna; Suriyamurthy, N.; Panigrahi, B. S.

    2015-06-24

    SrBPO{sub 5}: UO{sub 2}{sup 2+} was synthesized using solid state reaction method and characterized using powder X-ray diffraction. PXRD data showed the formation of single phase confirming successful doping of UO{sub 2}{sup 2+}. Photo luminescence investigation informed stabilization of Uranium as Uranyl (UO{sub 2}{sup 2+}) in SrBPO{sub 5} matrix. Luminescence decay time data suggested two possible environments for UO{sub 2}{sup 2+} with two different life time values.

  15. The Complexes of Bisphosphonate and Magnetite Nanoparticles to Remove Uranyl Ions from Aqueous Phase

    SciTech Connect

    Wang, L.; Yang, Z.; Gao, J.; Xu, K.; Gu, H.; Xu, B.; Zhang, B.; Zhang, X.

    2007-03-20

    Using tetraethyl-3-amino-propane-1,1-bisphosphonate (BP) as the functional molecule, we functionalized Fe3O4 magnetic nanoparticles via dopamine (DA) linkage to create a system with an Fe3O4-DA-BP nanostructure, which possesses high specificity for removing uranyl ions from water or blood. This work demonstrates that magnetic nanoparticles, combined with specific receptor-ligand interactions, promise a sensitive and rapid platform for the detection, recovery, and decorporation of radioactive metal toxins from biological environment.

  16. Amine templating effect absent in uranyl sulfates synthesized with 1,4-n-butyldiamine

    SciTech Connect

    Jouffret, Laurent J.; Wylie, Ernest M.; Burns, Peter C.

    2013-01-15

    Two new uranyl sulfates, (C{sub 4}H{sub 14}N{sub 2})[(UO{sub 2}){sub 2}(SO{sub 4}){sub 3}(H{sub 2}O)]{center_dot}2H{sub 2}O (NDUS2) and (C{sub 4}H{sub 14}N{sub 2})[(UO{sub 2})(SO{sub 4}){sub 2}(H{sub 2}O)]{center_dot}2H{sub 2}O (NDUS3), were synthesized and their crystal structures determined. NDUS2 was obtained in highly acidic media heat-treated at 373 K and subsequently maintained at 278 K until crystals formed after two months. NDUS3 results from the degradation of NDUS2 over the course of a few days. NDUS2 and NDUS3 crystallize in the monoclinic space group P2{sub 1}/n, a=10.9075(4) A, b=10.4513(4) A, c=17.7881(7) A, {beta}=97.908(2) Degree-Sign , V=2008.52(13) A{sup 3}, Z=4, at 140 K and a=8.8570(4) A, b=7.3299(3) A, c=20.4260(9) A, {beta}=95.140(2) Degree-Sign , V=1320.74(10) A{sup 3}, Z=4, at 140 K, respectively. The compounds contain interlayer 1,4-n-butyldiammonium cations that charge-balance the anionic structural units. - Graphical abstract: Amine templating effect absent in uranyl sulfates synthesized with 1,4-diaminobutane, as shown by the synthesis of two new uranyl sulfates, (C{sub 4}H{sub 14}N{sub 2})[(UO{sub 2}){sub 2}(SO{sub 4}){sub 3}(H{sub 2}O)]{center_dot}2H{sub 2}O (NDUS2) and (C{sub 4}H{sub 14}N{sub 2})[(UO{sub 2})(SO{sub 4}){sub 2}(H{sub 2}O)]{center_dot}2H{sub 2}O (NDUS3). Highlights: Black-Right-Pointing-Pointer Two layered uranyl sulfates were synthesized. Black-Right-Pointing-Pointer Amine molecules are located in the interlayers of the compounds. Black-Right-Pointing-Pointer No templating effect of the amine was observed. Black-Right-Pointing-Pointer Amine molecules are only charge balancing cations in the structures.

  17. Vasodilator Therapy: Nitrates and Nicorandil.

    PubMed

    Tarkin, Jason M; Kaski, Juan Carlos

    2016-08-01

    Nitrates have been used to treat symptoms of chronic stable angina for over 135 years. These drugs are known to activate nitric oxide (NO)-cyclic guanosine-3',-5'-monophasphate (cGMP) signaling pathways underlying vascular smooth muscle cell relaxation, albeit many questions relating to how nitrates work at the cellular level remain unanswered. Physiologically, the anti-angina effects of nitrates are mostly due to peripheral venous dilatation leading to reduction in preload and therefore left ventricular wall stress, and, to a lesser extent, epicardial coronary artery dilatation and lowering of systemic blood pressure. By counteracting ischemic mechanisms, short-acting nitrates offer rapid relief following an angina attack. Long-acting nitrates, used commonly for angina prophylaxis are recommended second-line, after beta-blockers and calcium channel antagonists. Nicorandil is a balanced vasodilator that acts as both NO donor and arterial K(+) ATP channel opener. Nicorandil might also exhibit cardioprotective properties via mitochondrial ischemic preconditioning. While nitrates and nicorandil are effective pharmacological agents for prevention of angina symptoms, when prescribing these drugs it is important to consider that unwanted and poorly tolerated hemodynamic side-effects such as headache and orthostatic hypotension can often occur owing to systemic vasodilatation. It is also necessary to ensure that a dosing regime is followed that avoids nitrate tolerance, which not only results in loss of drug efficacy, but might also cause endothelial dysfunction and increase long-term cardiovascular risk. Here we provide an update on the pharmacological management of chronic stable angina using nitrates and nicorandil.

  18. 21 CFR 172.170 - Sodium nitrate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Sodium nitrate. 172.170 Section 172.170 Food and... Preservatives § 172.170 Sodium nitrate. The food additive sodium nitrate may be safely used in or on specified... sablefish, smoked, cured salmon, and smoked, cured shad, so that the level of sodium nitrate does not...

  19. 21 CFR 172.170 - Sodium nitrate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Sodium nitrate. 172.170 Section 172.170 Food and... Preservatives § 172.170 Sodium nitrate. The food additive sodium nitrate may be safely used in or on specified... sablefish, smoked, cured salmon, and smoked, cured shad, so that the level of sodium nitrate does not...

  20. 21 CFR 172.170 - Sodium nitrate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Sodium nitrate. 172.170 Section 172.170 Food and... Preservatives § 172.170 Sodium nitrate. The food additive sodium nitrate may be safely used in or on specified... sablefish, smoked, cured salmon, and smoked, cured shad, so that the level of sodium nitrate does not...

  1. 21 CFR 172.170 - Sodium nitrate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Sodium nitrate. 172.170 Section 172.170 Food and... Preservatives § 172.170 Sodium nitrate. The food additive sodium nitrate may be safely used in or on specified... sablefish, smoked, cured salmon, and smoked, cured shad, so that the level of sodium nitrate does not...

  2. Nitrate Utilization by the Diatom Skeletonema costatum

    PubMed Central

    Serra, Juan L.; Llama, Maria J.; Cadenas, Eduardo

    1978-01-01

    Nitrate utilization has been characterized in nitrogen-deficient cells of the marine diatom Skeletonema costatum. In order to separate nitrate uptake from nitrate reduction, nitrate reductase activity was suppressed with tungstate. Neither nitrite nor the presence of amino acids in the external medium or darkness affects nitrate uptake kinetics. Ammonium strongly inhibits carrier-mediated nitrate uptake, without affecting diffusion transfer. A model is proposed for the uptake and assimilation of nitrate in S. costatum and their regulation by ammonium ions. PMID:16660653

  3. Complexation of the uranyl ion with the aminomethylenediphosphonates MAMDP and AMDP

    SciTech Connect

    Bollinger, J.E.; Roundhill, D.M.

    1994-12-21

    The use of uranium as a nuclear energy source has made it a valuable mineral resource over the past forty years. Processing uranium generally involves leaching the metal as the uranyl ion (UO{sub 2}){sup 2+} from ore, followed by solvent extraction, precipitation or batch adsorption onto ion exchange-type resins. Uranium reserves exist also in the form of UO{sub 2}(CO{sub 3}){sub 3}{sup 4{minus}} dissolved in seawater, and although these concentrations are very low they represent globally some 4.9 x 10{sup 9} tons. In the interest of tapping this resource efforts toward developing more efficient and selective means of UO{sub 2}{sup 2+} ion sequestering have been underway for some time. The authors have measured the stability and protonation constants of the different complexes formed in aqueous solution between the UO{sub 2}{sup 2+} ion and the compounds N,N{prime}-dimethylaminomethylenebis(phosphonic acid) (MAMDP) and aminomethylenebis(phosphonic acid) (AMDP). From these data one can evaluate the potential for compounds of this type to be useful as uranyl ion sequestering agents.

  4. Rapid Dissolution of Soluble Uranyl Phases in Arid, Mine-Impacted Catchments near Church Rock, NM

    PubMed Central

    DELEMOS, JAMIE L.; BOSTICK, BENJAMIN C.; QUICKSALL, ANDREW N.; LANDIS, JOSHUA D.; GEORGE, CHRISTINE C.; SLAGOWSKI, NAOMI L.; ROCK, TOMMY; BRUGGE, DOUG; LEWIS, JOHNNYE; DURANT, JOHN L.

    2008-01-01

    We tested the hypothesis that runoff of uranium-bearing particles from mining waste disposal areas was a significant mechanism for redistribution of uranium in the northeastern part of the Upper Puerco River watershed (New Mexico). However, our results were not consistent with this hypothesis. Analysis of >100 sediment and suspended sediment samples collected adjacent to and downstream from uranium source areas indicated that uranium levels in the majority of the samples were not elevated above background. Samples collected within 50 m of a known waste disposal site were subjected to detailed geochemical characterization. Uranium in these samples was found to be highly soluble; treatment with synthetic pore water for 24 h caused dissolution of 10–50% of total uranium in the samples. Equilibrium uranium concentrations in pore water were >4.0 mg/L and were sustained in repeated wetting events, effectively depleting soluble uranium from the solid phase. The dissolution rate of uranium appeared to be controlled by solid-phase diffusion of uranium from within uranium-bearing mineral particles. X-ray adsorption spectroscopy indicated the presence of a soluble uranyl silicate, and possibly a uranyl phosphate. These phases were exhausted in transported sediment suggesting that uranium was readily mobilized from sediments in the Upper Puerco watershed and transported in the dissolved load. These results could have significance for uranium risk assessment as well as mining waste management and cleanup efforts. PMID:18589950

  5. Structural elucidation and physicochemical properties of mononuclear Uranyl(VI) complexes incorporating dianionic units

    PubMed Central

    Azam, Mohammad; Velmurugan, Gunasekaran; Wabaidur, Saikh Mohammad; Trzesowska-Kruszynska, Agata; Kruszynski, Rafal; Al-Resayes, Saud I.; Al-Othman, Zeid A.; Venuvanalingam, Ponnambalam

    2016-01-01

    Two derivatives of organouranyl mononuclear complexes [UO2(L)THF] (1) and [UO2(L)Alc] (2), where L = (2,2′-(1E,1′E)-(2,2-dimethylpropane-1,3-dyl)bis(azanylylidene, THF = Tetrahydrofuran, Alc = Alcohol), have been prepared. These complexes have been determined by elemental analyses, single crystal X-ray crystallography and various spectroscopic studies. Moreover, the structure of these complexes have also been studied by DFT and time dependent DFT measurements showing that both the complexes have distorted pentagonal bipyramidal environment around uranyl ion. TD-DFT results indicate that the complex 1 displays an intense band at 458.7 nm which is mainly associated to the uranyl centered LMCT, where complex 2 shows a band at 461.8 nm that have significant LMCT character. The bonding has been further analyzed by EDA and NBO. The photocatalytic activity of complexes 1 and 2 for the degradation of rhodamine-B (RhB) and methylene blue (MB) under the irradiation of 500W Xe lamp has been explored, and found more efficient in presence of complex 1 than complex 2 for both dyes. In addition, dye adsorption and photoluminescence properties have also been discussed for both complexes. PMID:27595801

  6. Roles of acetone and diacetone alcohol in coordination and dissociation reactions of uranyl complexes.

    PubMed

    Rios, Daniel; Schoendorff, George; Van Stipdonk, Michael J; Gordon, Mark S; Windus, Theresa L; Gibson, John K; de Jong, Wibe A

    2012-12-01

    Combined collision-induced dissociation mass spectrometry experiments with DFT and MP2 calculations were employed to elucidate the molecular structures and energetics of dissociation reactions of uranyl species containing acetone and diacetone alcohol ligands. It is shown that solutions containing diacetone alcohol ligands can produce species with more than five oxygen atoms available for coordination. Calculations confirm that complexes with up to four diacetone alcohol ligands can be energetically stable but that the effective number of atoms coordinating with uranium in the equatorial plane does not exceed five. Water elimination reactions of diacetone alcohol ligands are shown to have two coordination-dependent reaction channels, through formation of mesityl oxide ligands or formation of alkoxide and protonated mesityl oxide species. The present results provide an explanation for the implausible observation of "[UO(2)(ACO)(6,7,8)](2+)" in and observed water-elimination reactions from purportedly uranyl-acetone complexes (Rios, D.; Rutkowski, P. X.; Van Stipdonk, M. J.; Gibson, J. K. Inorg. Chem. 2011, 50, 4781). PMID:23146003

  7. Structural elucidation and physicochemical properties of mononuclear Uranyl(VI) complexes incorporating dianionic units.

    PubMed

    Azam, Mohammad; Velmurugan, Gunasekaran; Wabaidur, Saikh Mohammad; Trzesowska-Kruszynska, Agata; Kruszynski, Rafal; Al-Resayes, Saud I; Al-Othman, Zeid A; Venuvanalingam, Ponnambalam

    2016-01-01

    Two derivatives of organouranyl mononuclear complexes [UO2(L)THF] (1) and [UO2(L)Alc] (2), where L = (2,2'-(1E,1'E)-(2,2-dimethylpropane-1,3-dyl)bis(azanylylidene, THF = Tetrahydrofuran, Alc = Alcohol), have been prepared. These complexes have been determined by elemental analyses, single crystal X-ray crystallography and various spectroscopic studies. Moreover, the structure of these complexes have also been studied by DFT and time dependent DFT measurements showing that both the complexes have distorted pentagonal bipyramidal environment around uranyl ion. TD-DFT results indicate that the complex 1 displays an intense band at 458.7 nm which is mainly associated to the uranyl centered LMCT, where complex 2 shows a band at 461.8 nm that have significant LMCT character. The bonding has been further analyzed by EDA and NBO. The photocatalytic activity of complexes 1 and 2 for the degradation of rhodamine-B (RhB) and methylene blue (MB) under the irradiation of 500W Xe lamp has been explored, and found more efficient in presence of complex 1 than complex 2 for both dyes. In addition, dye adsorption and photoluminescence properties have also been discussed for both complexes. PMID:27595801

  8. Deciphering the energy landscape of the interaction uranyl-DCP with antibodies using dynamic force spectroscopy.

    PubMed

    Teulon, Jean-Marie; Parot, Pierre; Odorico, Michael; Pellequer, Jean-Luc

    2008-11-15

    Previous studies on molecular recognition of uranyl-DCP (dicarboxy-phenanthroline chelator) compound by two distinct monoclonal antibodies (Mabs U04S and U08S) clearly showed the presence of a biphasic shape in Bell-Evans' plots and an accentuated difference in slopes at the high loading rates. To further explore the basis in the slope difference, we have performed complementary experiments using antibody PHE03S, raised against uranyl-DCP but, presenting a strong cross-reactivity toward the DCP chelator. This work allowed us to obtain a reallocation of the respective contributions of the metal ion itself and that of the chelator. Results led us to propose a 2D schematic model representing two energy barriers observed in the systems Mabs U04S- and U08S-[UO(2)-DCP] where the outer barrier characterizes the interaction between UO(2) and Mab whereas the inner barrier characterizes the interaction between DCP and Mab. Using dynamic force spectroscopy, it is thus possible to dissect molecular interactions during the unbinding between proteins and ligands.

  9. Structural elucidation and physicochemical properties of mononuclear Uranyl(VI) complexes incorporating dianionic units.

    PubMed

    Azam, Mohammad; Velmurugan, Gunasekaran; Wabaidur, Saikh Mohammad; Trzesowska-Kruszynska, Agata; Kruszynski, Rafal; Al-Resayes, Saud I; Al-Othman, Zeid A; Venuvanalingam, Ponnambalam

    2016-09-06

    Two derivatives of organouranyl mononuclear complexes [UO2(L)THF] (1) and [UO2(L)Alc] (2), where L = (2,2'-(1E,1'E)-(2,2-dimethylpropane-1,3-dyl)bis(azanylylidene, THF = Tetrahydrofuran, Alc = Alcohol), have been prepared. These complexes have been determined by elemental analyses, single crystal X-ray crystallography and various spectroscopic studies. Moreover, the structure of these complexes have also been studied by DFT and time dependent DFT measurements showing that both the complexes have distorted pentagonal bipyramidal environment around uranyl ion. TD-DFT results indicate that the complex 1 displays an intense band at 458.7 nm which is mainly associated to the uranyl centered LMCT, where complex 2 shows a band at 461.8 nm that have significant LMCT character. The bonding has been further analyzed by EDA and NBO. The photocatalytic activity of complexes 1 and 2 for the degradation of rhodamine-B (RhB) and methylene blue (MB) under the irradiation of 500W Xe lamp has been explored, and found more efficient in presence of complex 1 than complex 2 for both dyes. In addition, dye adsorption and photoluminescence properties have also been discussed for both complexes.

  10. Structural elucidation and physicochemical properties of mononuclear Uranyl(VI) complexes incorporating dianionic units

    NASA Astrophysics Data System (ADS)

    Azam, Mohammad; Velmurugan, Gunasekaran; Wabaidur, Saikh Mohammad; Trzesowska-Kruszynska, Agata; Kruszynski, Rafal; Al-Resayes, Saud I.; Al-Othman, Zeid A.; Venuvanalingam, Ponnambalam

    2016-09-01

    Two derivatives of organouranyl mononuclear complexes [UO2(L)THF] (1) and [UO2(L)Alc] (2), where L = (2,2‧-(1E,1‧E)-(2,2-dimethylpropane-1,3-dyl)bis(azanylylidene, THF = Tetrahydrofuran, Alc = Alcohol), have been prepared. These complexes have been determined by elemental analyses, single crystal X-ray crystallography and various spectroscopic studies. Moreover, the structure of these complexes have also been studied by DFT and time dependent DFT measurements showing that both the complexes have distorted pentagonal bipyramidal environment around uranyl ion. TD-DFT results indicate that the complex 1 displays an intense band at 458.7 nm which is mainly associated to the uranyl centered LMCT, where complex 2 shows a band at 461.8 nm that have significant LMCT character. The bonding has been further analyzed by EDA and NBO. The photocatalytic activity of complexes 1 and 2 for the degradation of rhodamine-B (RhB) and methylene blue (MB) under the irradiation of 500W Xe lamp has been explored, and found more efficient in presence of complex 1 than complex 2 for both dyes. In addition, dye adsorption and photoluminescence properties have also been discussed for both complexes.

  11. Removal of uranyl ions in aquatic mediums by using a new material: gallocyanine grafted hydrogel.

    PubMed

    Ulusoy, Halil İbrahim; Simşek, Selçuk

    2013-06-15

    A new material containing gallocyanine (GC) grafted polyacyril amide (PAA) was synthesized and its adsorption ability was examined for the removal of uranyl ions from aqueous media. The new developed adsorbent was characterized by FTIR, SEM, and PZC analysis. Adsorption of UO₂(2+) ions from aqueous solution as a function of ion concentration, pH, ionic strength, temperature, and reusability of adsorbent was investigated in detail. The adsorption data were analyzed by using the Langmuir, Freundlich and Dubinin-Radushkevich (DR) models. The adsorption of UO₂(2+) increased with pH and reached a plateau value in the pH range 5-6. The adsorption of UO₂(2+) ions were not affected by increasing ionic strength. The adsorption mechanism followed an endothermic and spontaneous process with increased disorderliness at adsorbate/adsorbent interface. The adsorption process followed a pseudo-second-order kinetics. The new developed material is a potential adsorbent for effective removal of uranyl ions from aquatic solutions. PMID:23669652

  12. Strongly coupled binuclear uranium-oxo complexes from uranyl oxo rearrangement and reductive silylation

    NASA Astrophysics Data System (ADS)

    Arnold, Polly L.; Jones, Guy M.; Odoh, Samuel O.; Schreckenbach, Georg; Magnani, Nicola; Love, Jason B.

    2012-03-01

    The most common motif in uranium chemistry is the d0f0 uranyl ion [UO2]2+ in which the oxo groups are rigorously linear and inert. Alternative geometries, such as the cis-uranyl, have been identified theoretically and implicated in oxo-atom transfer reactions that are relevant to environmental speciation and nuclear waste remediation. Single electron reduction is now known to impart greater oxo-group reactivity, but with retention of the linear OUO motif, and reactions of the oxo groups to form new covalent bonds remain rare. Here, we describe the synthesis, structure, reactivity and magnetic properties of a binuclear uranium-oxo complex. Formed through a combination of reduction and oxo-silylation and migration from a trans to a cis position, the new butterfly-shaped Si-OUO2UO-Si molecule shows remarkably strong UV-UV coupling and chemical inertness, suggesting that this rearranged uranium oxo motif might exist for other actinide species in the environment, and have relevance to the aggregation of actinide oxide clusters.

  13. Impact of pore size on the sorption of uranyl under seawater conditions

    DOE PAGES

    Mayes, Richard T.; Gorka, Joanna; Dai, Sheng

    2016-04-05

    The extraction of uranium from seawater has received significant interest recently, because of the possibility of a near-limitless supply of uranium to fuel the nuclear power industry. While sorbent development has focused primarily on polymeric sorbents, nanomaterials represent a new area that has the potential to surpass the current polymeric sorbents, because of the high surface areas that are possible. Mesoporous carbon materials are a stable, high-surface-area material capable of extracting various chemical species from a variety of environments. Herein, we report the use of a dual templating process to understand the effect of pore size on the adsorption ofmore » uranyl ions from a uranyl brine consisting of seawater-relevant sodium, chloride, and bicarbonate ions. It was found that pore size played a more significant role in the effective use of the grafted polymer, leading to higher uranium capacities than the surface area. Furthermore, the pore size must be tailored to meet the demands of the extraction medium and analyte metal to achieve efficacy as an adsorbent.« less

  14. Rapid dissolution of soluble uranyl phases in arid, mine-impacted catchments near Church Rock, NM.

    PubMed

    deLemos, Jamie L; Bostick, Benjamin C; Quicksall, Andrew N; Landis, Joshua D; George, Christine C; Slagowski, Naomi L; Rock, Tommy; Brugge, Doug; Lewis, Johnnye; Durant, John L

    2008-06-01

    We tested the hypothesis that runoff of uranium-bearing particles from mining waste disposal areas was a significant mechanism for redistribution of uranium in the northeastern part of the Upper Puerco River watershed (New Mexico). However, our results were not consistent with this hypothesis. Analysis of > 100 sediment and suspended sediment samples collected adjacent to and downstream from uranium source areas indicated that uranium levels in the majority of the samples were not elevated above background. Samples collected within 50 m of a known waste disposal site were subjected to detailed geochemical characterization. Uranium in these samples was found to be highly soluble; treatment with synthetic pore water for 24 h caused dissolution of 10--50% of total uranium in the samples. Equilibrium uranium concentrations in pore water were > 4.0 mg/L and were sustained in repeated wetting events, effectively depleting soluble uranium from the solid phase. The dissolution rate of uranium appeared to be controlled by solid-phase diffusion of uranium from within uranium-bearing mineral particles. X-ray adsorption spectroscopy indicated the presence of a soluble uranyl silicate, and possibly a uranyl phosphate. These phases were exhausted in transported sediment suggesting that uranium was readily mobilized from sediments in the Upper Puerco watershed and transported in the dissolved load. These results could have significance for uranium risk assessment as well as mining waste management and cleanup efforts.

  15. Elucidating self-assembly mechanisms of uranyl-peroxide capsules from monomers.

    PubMed

    Liao, Zuolei; Deb, Tapash; Nyman, May

    2014-10-01

    Self-assembly of uranyl peroxide polyoxometalates (POMs) in alkaline peroxide solutions has been known for almost a decade, but in these dynamic solutions that contain high concentrations of base and peroxide the reaction pathway could never be discerned, mixed species are obtained, and reproducibility is sometimes a challenge. Here we elucidate the reaction mechanisms utilizing self-assembly of the U24 cluster, [UO2(O2)(OH)]24(24-), from monomers as a model system. Using Raman as our main spectroscopic probe, we learned that the monomeric species is persistent in water at room temperature indefinitely. However, if a redox-active transition metal catalyst (copper (Cu(2+)) or cobalt (Co(2+))) is added, self-assembly is accelerated in a significant manner, forming U24 peroxide clusters in several hours, which is a good time scale for studying reaction mechanisms. From semiquantitative treatment of the spectroscopic data, we elucidate reaction mechanisms that are consistent with prior structural and computational studies that suggest uranyl peroxide rings templated by alkalis are the building units of clusters. By understanding aqueous speciation and processes, we are moving toward assuming control over cluster self-assembly that has been mastered for decades now in the analogous transition-metal POM systems. PMID:25238533

  16. Charge asymmetry of the purple membrane measured by uranyl quenching of dansyl fluorescence. [Halobacterium halobium

    SciTech Connect

    Renthal, R.; Cha, C.H.

    1984-05-01

    Purple membrane was covalently labeled with 5-(dimethylamino) naphthalene-1-sulfonyl hydrazine (dansyl hydrazine) by carbodiimide coupling to the cytoplasmic surface (carboxyl-terminal tail: 0.7 mol/mol bacteriorhodopsin) or by periodate oxidation and dimethylaminoborane reduction at the extracellular surface (glycolipids: 1 mol/mol). In 2 mM acetate buffer, pH 5.6, micromolar concentrations of UO/sub 2//sup 2 +/ were found to quench the dansyl groups on the cytoplasmic surface (maximum = 26%), while little quenching was observed at the extracellular surface (maximum = 4%). Uranyl ion quenched dansyl hydrazine in free solution at much higher concentrations. Uranyl also bound tightly to unmodified purple membrane, (apparent dissociation constant = 0.8 ..mu..M) as measured by a centrifugation assay. The maximum stoichiometry was 10 mol/mol of bacteriorhodopsin, which is close to the amount of phospholipid phosphorus in purple membrane. The results were analyzed on the assumptions that UO/sub 2//sup 2 +/ binds in a 1:1 complex with phospholipid phosphate and that the dansyl distributon and quenching mechanisms are the same at both surfaces. This indicates a 9:1 ratio of phosphate between the cytoplasmic and extracellular surfaces. Thus, the surface change density of the cytoplasmic side of the membrane is more negative than - 0.010 charges/A/sup 2/.

  17. Method for recovering aluminum fluoride from fluorine-containing aqueous aluminum nitrate solutions

    SciTech Connect

    Ishimi, H.; Shimauchi, H.; Tanaka, C.

    1983-02-22

    In a process for converting UF/sub 6/ into UO/sub 2/, the UF/sub 6/ is brought into contact with an aqueous aluminum nitrate solution. The resultant product is solvent extracted with tributyl phosphate to remove uranyl nitrate. The raffinate has a fluorine/aluminum (F/Al) weight ratio within the range of from about 0.5 to about a sufficient quantity of hydrofluoric acid is added to T raffinate to minimize the solubility of aluminum fluoride (AlF/sub 3/) therein and thereby maximize the precipitation potential of AlF/sub 3/. Generally this occurs when sufficient hydrofluoric acid has been added to cause the F/Al weight ratio to be within the range of from about 1.8 to about 2.2. As a result of this treatment, the raffinate is divided into an uranium-containing aqueous solution and an AlF/sub 3/ precipitate which contains substantially no uranium.

  18. Cation–cation interactions and cation exchange in a series of isostructural framework uranyl tungstates

    SciTech Connect

    Balboni, Enrica; Burns, Peter C.

    2014-05-01

    The isotypical compounds (UO{sub 2}){sub 3}(WO{sub 6})(H{sub 2}O){sub 5} (1), Ag(UO{sub 2}){sub 3}(WO{sub 6})(OH)(H{sub 2}O){sub 3} (2), K(UO{sub 2}){sub 3}(WO{sub 6})OH(H{sub 2}O){sub 4} (3), Rb(UO{sub 2}){sub 3}(WO{sub 6})(OH)(H{sub 2}O){sub 3.5} (4), and Cs(UO{sub 2}){sub 3}(WO{sub 6})OH(H{sub 2}O){sub 3} (5) were synthesized, characterized, and their structures determined. Each crystallizes in space group Cc. (1): a=12.979 (3), b=10.238 (2), c=11.302 (2), β=102.044 (2); (2): a=13.148 (2), b=9.520 (1), c=11.083 (2), β=101.568 (2); (3): a=13.111 (8), b=9.930 (6), c=11.242 (7), β=101.024 (7); (4): a=12.940 (2), b=10.231 (2), c=11.259(2), β=102.205 (2); (5): a=12.983 (3), b=10.191 (3), c=11.263 (4), β=101.661 (4). Compounds 1–5 are a framework of uranyl and tungsten polyhedra containing cation–cation interactions. The framework has three symmetrically distinct U(VI) cations, one tungsten, sixteen to eighteen oxygen atoms, and in 2–5, one monovalent cation. Each atom occupies a general position. Each U(VI) cation is present as a typical (UO{sub 2}){sup 2+} uranyl ion in an overall pentagonal bipyramidal coordination environment. Each pentagonal bipyramid shares two equatorial edges with two other pentagonal bipyramids, forming a trimer. Trimers are connected into chains by edge-sharing with WO{sub 6} octahedra. Chains are linked through cation–cation interactions between two symmetrically independent uranyl ions. This yields a remarkably complex system of intersecting channels that extend along [0 0 1] and [−1 1 0]. The cation exchange properties of 2 and 3 were characterized at room temperature and at 140 °C. - Graphical abstract: Chains of uranium and tungsten polyhedra are connected into a three dimensional framework by cation–cation interactions occurring between two symmetrically independent uranyl pentagonal bipyramids. Monovalent cations present in channels within the structure can be exchanged by room temperature or mild hydrothermal

  19. Nitrate transport is independent of NADH and NAD(P)H nitrate reductases in barley seedlings

    NASA Technical Reports Server (NTRS)

    Warner, R. L.; Huffaker, R. C.

    1989-01-01

    Barley (Hordeum vulgare L.) has NADH-specific and NAD(P)H-bispecific nitrate reductase isozymes. Four isogenic lines with different nitrate reductase isozyme combinations were used to determine the role of NADH and NAD(P)H nitrate reductases on nitrate transport and assimilation in barley seedlings. Both nitrate reductase isozymes were induced by nitrate and were required for maximum nitrate assimilation in barley seedlings. Genotypes lacking the NADH isozyme (Az12) or the NAD(P)H isozyme (Az70) assimilated 65 or 85%, respectively, as much nitrate as the wild type. Nitrate assimilation by genotype (Az12;Az70) which is deficient in both nitrate reductases, was only 13% of the wild type indicating that the NADH and NAD(P)H nitrate reductase isozymes are responsible for most of the nitrate reduction in barley seedlings. For all genotypes, nitrate assimilation rates in the dark were about 55% of the rates in light. Hypotheses that nitrate reductase has direct or indirect roles in nitrate uptake were not supported by this study. Induction of nitrate transporters and the kinetics of net nitrate uptake were the same for all four genotypes indicating that neither nitrate reductase isozyme has a direct role in nitrate uptake in barley seedlings.

  20. Reduction of nitrate in Shewanella

    SciTech Connect

    Gao, Haichun; Yang, Zamin Koo; Barua, Sumitra; Reed, SB; Nealson, Kenneth H.; Fredrikson, JK; Tiedje, James; Zhou, Jizhong

    2009-01-01

    In the genome of Shewanella oneidensis, a napDAGHB gene cluster encoding periplasmic nitrate reductase (NapA) and accessory proteins and an nrfA gene encoding periplasmic nitrite reductase (NrfA) have been identified. These two systems seem to be atypical because the genome lacks genes encoding cytoplasmic membrane electron transport proteins, NapC for NAP and NrfBCD/NrfH for NRF, respectively. Here, we present evidence that reduction of nitrate to ammonium in S. oneidensis is carried out by these atypical systems in a two-step manner. Transcriptional and mutational analyses suggest that CymA, a cytoplasmic membrane electron transport protein, is likely to be the functional replacement of both NapC and NrfH in S. oneidensis. Surprisingly, a strain devoid of napB encoding the small subunit of nitrate reductase exhibited the maximum cell density sooner than the wild type. Further characterization of this strain showed that nitrite was not detected as a free intermediate in its culture and NapB provides a fitness gain for S. oneidensis to compete for nitrate in the environments. On the basis results from mutational analyses of napA, napB, nrfA and napBnrfA in-frame deletion mutants, we propose that NapB is able to favor nitrate reduction by routing electrons to NapA exclusively.

  1. Ultrasensitive detection of uranyl by graphene oxide-based background reduction and RCDzyme-based enzyme strand recycling signal amplification.

    PubMed

    Li, Ming-Hui; Wang, Yong-Sheng; Cao, Jin-Xiu; Chen, Si-Han; Tang, Xian; Wang, Xiao-Feng; Zhu, Yu-Feng; Huang, Yan-Qin

    2015-10-15

    We proposed a novel strategy which combines graphene oxide-based background reduction with RCDzyme-based enzyme strand recycling amplification for ultrahigh sensitive detection of uranyl. The RCDzyme is designed to contain a guanine (G)-rich sequence that replaces the partial sequence in an uranyl-specific DNAzyme. This multifunctional probe can act as the target recognition element, DNAzyme and the primer of signal amplification. The presence of UO2(2+) can induce the cleavage of the substrate strands in RCDzyme. Then, each released enzyme strand can hybridize with another substrate strands to trigger many cycles of the cleavage by binding uranyl, leading to the formation of more G-quadruplexes by split guanine-rich oligonucleotide fragments. The resulting G-quadruplexes could bind to N-methyl-mesoporphyrin IX (NMM), causing an amplified detection signal for the target uranyl. Next, graphene oxide-based background reduction strategy was further employed for adsorbing free ssDNA and NMM, thereby providing a proximalis zero-background signal. The combination of RCDzyme signal amplification and proximalis zero-background signal remarkably improves the sensitivity of this method, achieving a dynamic range of two orders of magnitude and giving a detection limit down to 86 pM, which is much lower than those of related literature reports. These achievements might be helpful in the design of highly sensitive analytical platform for wide applications in environmental and biomedical fields. PMID:26000462

  2. Nitrate Trends in Minnesota Rivers

    USGS Publications Warehouse

    Wall, Dave; Christopherson, Dave; Lorenz, Dave; Martin, Gary

    2013-01-01

    The objective of this study was to assess long-term trends (30 to 35 years) of flow-adjusted concentrations of nitrite+nitrate-N (hereinafter referred to as nitrate) in a way that would allow us to discern changing trends. Recognizing that these trends are commonly different from one river to another river and from one part of the state to another, our objective was to examine as many river monitoring sites across the state as possible for which sufficient long term streamflow and concentration data were available.

  3. A new uranyl niobate sheet in the cesium uranyl niobate Cs{sub 9}[(UO{sub 2}){sub 8}O{sub 4}(NbO{sub 5})(Nb{sub 2}O{sub 8}){sub 2}

    SciTech Connect

    Saad, S.; Obbade, S. Yagoubi, S.; Renard, C.; Abraham, F.

    2008-04-15

    A new cesium uranyl niobate, Cs{sub 9}[(UO{sub 2}){sub 8}O{sub 4}(NbO{sub 5})(Nb{sub 2}O{sub 8}){sub 2}] or Cs{sub 9}U{sub 8}Nb{sub 5}O{sub 41} has been synthesized by high-temperature solid-state reaction, using a mixture of U{sub 3}O{sub 8}, Cs{sub 2}CO{sub 3} and Nb{sub 2}O{sub 5}. Single crystals were obtained by incongruent melting of a starting mixture with metallic ratio=Cs/U/Nb=1/1/1. The crystal structure of the title compound was determined from single crystal X-ray diffraction data, and solved in the monoclinic system with the following crystallographic data: a=16.729(2) A, b=14.933(2) A, c=20.155(2) A{beta}=110.59(1){sup o}, P2{sub 1}/c space group and Z=4. The crystal structure was refined to agreement factors R{sub 1}=0.049 and wR{sub 2}=0.089, calculated for 4660 unique observed reflections with I{>=}2{sigma}(I), collected on a BRUKER AXS diffractometer with MoK{alpha} radiation and a CCD detector. In this structure the UO{sub 7} uranyl pentagonal bipyramids are connected by sharing edges and corners to form a uranyl layer {sub {infinity}}{sup 2}[U{sub 8}O{sub 36}] corresponding to a new anion-sheet topology, and creating triangular, rectangular and square vacant sites. The two last sites are occupied by Nb{sub 2}O{sub 8} entities and NbO{sub 5} square pyramids, respectively, to form infinite uranyl niobate sheets {sub {infinity}}{sup 2}[(UO{sub 2}){sub 8}O{sub 4}(NbO{sub 5})(Nb{sub 2}O{sub 8}){sub 2}]{sup 9-} stacking along the [010] direction. The Nb{sub 2}O{sub 8} entities result from two edge-shared NbO{sub 5} square pyramids. The Cs{sup +} cations are localized between layers and ensured the cohesion of the structure. The cesium cation mobility between the uranyl niobate sheets was studied by electrical measurements. The conductivity obeys the Arrhenius law in all the studied temperature domains. The observed low conductivity values with high activation energy may be explained by the strong connection of the Cs{sup +} cations to the infinite

  4. Dietary nitrate and cardiovascular health

    USGS Publications Warehouse

    Ahluwalia, A.; Gladwin, M.T.; Harman, Jane L.; Ward, M.H.; Nolan, Bernard T.

    2014-01-01

    The National Heart, Lung, and Blood Institute convened this workshop to discuss the results of recent research on the effects of inorganic nitrate and nitrite on the cardiovascular system, possible long term effects of these compounds in the diet and drinking water, and future research needs including population-wide effects examined through epidemiological studies.

  5. Biological denitrification of high concentration nitrate waste

    DOEpatents

    Francis, Chester W.; Brinkley, Frank S.

    1977-01-01

    Biological denitrification of nitrate solutions at concentrations of greater than one kilogram nitrate per cubic meter is accomplished anaerobically in an upflow column having as a packing material a support for denitrifying bacteria.

  6. Cluster-Models for Uranyl(VI) Adsorption on alpha-Alumina

    SciTech Connect

    Glezakou, Vassiliki Alexandra; De Jong, Wibe A.

    2011-02-24

    Aqueous complexation, adsorption and redox chemistry of actinide species at mineral surfaces have significant impact on their transport and reactive behaviour in chemically and physically heterogeneous environments. The adsorption configurations and energies of micro-solvated uranyl dication, UO2 2+, on fully hydroxylated and H-deficient a-alumina (0001)-like finite cluster models were studied. The significant size of the models provides faithful representations of features that have emerged from periodic calculations, but most importantly, they afford us a systematic study of the preferred adsorption configurations, effect of secondary solvation shells and explicit treatment of the total charge. The energetics computed from the difference between the optimized structures and the appropriate reference states, point at a preference for inner sphere type complex.

  7. Hydrothermal synthesis, structure and thermal stability of diamine templated layered uranyl-vanadates

    SciTech Connect

    Rivenet, Murielle Vigier, Nicolas; Roussel, Pascal; Abraham, Francis

    2007-02-15

    Six new layered uranyl vanadates (NH{sub 4}){sub 2}[(UO{sub 2}){sub 2}V{sub 2}O{sub 8}] (1), (H{sub 2}EN)[(UO{sub 2}){sub 2}V{sub 2}O{sub 8}] (2), (H{sub 2}DAP)[(UO{sub 2}){sub 2}V{sub 2}O{sub 8}] (3), (H{sub 2}PIP)[(UO{sub 2}){sub 2}(VO{sub 4}){sub 2}].0,8H{sub 2}O (4), (H{sub 2}DMPIP)[(UO{sub 2}){sub 2}V{sub 2}O{sub 8}] (5), (H{sub 2}DABCO)[(UO{sub 2}){sub 2}(VO{sub 4}){sub 2}] (6) were prepared from mild-hydrothermal reactions using 1,2-ethylenediamine (EN); 1,3-diaminopropane (DAP); piperazine (PIP); 1-methylpiperazine (MPIP); 1,4-diazabicyclo[2,2,2]octane (DABCO). The structures of 1, 4, 5 and 6 were solved using single-crystal X-ray diffraction data while the structural models of 2 and 3 were established from powder X-ray diffraction data. In compounds 1, 2, 3 and 5, the uranyl-vanadate layers are built from dimers of edge-shared UO{sub 7} pentagonal bipyramids and dimers of edge-shared VO{sub 5} square pyramids further connected through edge-sharing. In 1 and 3, the layers are identical to that occurring in the carnotite group of uranyl-vanadates. In 2 and 5, the V{sub 2}O{sub 8} dimers differ in orientation leading to a new type of layer. The layers of compound 4 and 6 are built from chains of edge-shared UO{sub 7} pentagonal bipyramids connected by VO{sub 4} tetrahedra and are of uranophane-type anion topology. For the six compounds, the ammonium or organoammonium cation resides in the space between the inorganic layers. Crystallographic data: 1 monoclinic, space group P2{sub 1}/c with a=6.894(2), b=8.384(3), c=10.473(4) A and {beta}=106.066(5){sup o}, 2 monoclinic, space group P2{sub 1}/a with a=13.9816(6), b=8.6165(3), c=10.4237(3) A and {gamma}=93.125(3){sup o}, 3 orthorhombic, space group Pmcn with a=14.7363(8), b=8.6379(4) and c=10.4385(4) A, 4 monoclinic, space group C2/m with a=15.619(2), b=7.1802(8), c=6.9157(8) A and {beta}=101.500(2){sup o}, 5 monoclinic, space group P2{sub 1}/b with a=9.315(2), b=8.617(2), c=10.5246(2) A and {gamma}=114

  8. The effect of uranyl acetate on human lymphoblastoid cells (RPMI 6410) and HeLa cells.

    PubMed Central

    Ghadially, F. N.; Yang-Steppuhn, S. E.; Lalonde, J. M.

    1982-01-01

    RPMI 6410 cells and HeLa cells were exposed to uranyl acetate. In RPMI 6410 cell cultures this produced single-membrane-bound presumably lysosomal bodies (called "uraniosomes") containing electron-dense crystals in the cultured cells and crystalline deposits in extracellular locations. Neither uraniosomes nor extracellular uranium deposits were found in HeLa cell cultures. All uraniosomes and extracellular uranium deposits analysed by electron-probed X-ray analysis were found to contain uranium, potassium and phosphorus. Traces of sulphur were detected in some but not all uraniosomes and extracellular uranium deposits. Traces of calcium were found in all extracellular uranium deposits and in some uraniosomes also. Images Fig. 5 Fig. 6 Fig. 7 Fig. 8 Fig. 9 Fig. 1 Fig. 2 Fig. 3 Fig. 4 PMID:7093141

  9. Roles of Acetone and Diacetone Alcohol in Coordination and Dissociation Reactions of Uranyl Complexes

    SciTech Connect

    Rios, Daniel; Schoendorff, George E.; Van Stipdonk, Michael J.; Gordon, Mark S.; Windus, Theresa L.; Gibson, John K.; De Jong, Wibe A.

    2012-12-03

    Combined collision-induced dissociation mass-spectrometry experiments and DFT calculations were employed to elucidate the molecular structure of "hypercoordinated" species and the energetics of water-elimination reactions of uranyl acetone complexes observed in earlier work (Rios, D.; Rutkowski, P. X.; Van Stipdonk, M. J.; Gibson, J. K. Inorg. Chem. 2011, 50, 4781). It is shown that the "hypercoordinated" species contain diacetone alcohol ligands bonded in either bidentate or monodentate fashion, which are indistinguishable from (acetone)2 in mass spectrometry. Calculations confirm that four diacetone ligands can form stable complexes, but that the effective number of atoms coordinating with uranium in the equatorial plane does not exceed five. Diacetone alcohol ligands are shown to form mesityl oxide ligands and alkoxide species through the elimination of water, providing an explanation for the observed water-elimination reactions.

  10. Syntheses, structures, characterizations and charge-density matching of novel amino-templated uranyl selenates

    SciTech Connect

    Ling Jie; Sigmon, Ginger E.; Burns, Peter C.

    2009-02-15

    Five hybrid organic-inorganic uranyl selenates have been synthesized, characterized and their structures have been determined. The structure of (C{sub 2}H{sub 8}N){sub 2}[(UO{sub 2}){sub 2}(SeO{sub 4}){sub 3}(H{sub 2}O)] (EthylAUSe) is monoclinic, P2{sub 1}, a=8.290(1), b=12.349(2), c=11.038(2) A, {beta}=104.439(4){sup o}, V=1094.3(3) A{sup 3}, Z=2, R{sub 1}=0.0425. The structure of (C{sub 7}H{sub 10}N){sub 2}[(UO{sub 2})(SeO{sub 4}){sub 2}(H{sub 2}O)]H{sub 2}O (BenzylAUSe) is orthorhombic, Pna2{sub 1}, a=24.221(2), b=11.917(1), c=7.4528(7) A, V=2151.1(3) A{sup 3}, Z=4, R{sub 1}=0.0307. The structure of (C{sub 2}H{sub 10}N{sub 2})[(UO{sub 2})(SeO{sub 4}){sub 2}(H{sub 2}O)](H{sub 2}O){sub 2} (EDAUSe) is monoclinic, P2{sub 1}/c, a=11.677(2), b=7.908(1), c=15.698(2) A, {beta}=98.813(3){sup o}, V=1432.4(3) A{sup 3}, Z=4, R{sub 1}=0.0371. The structure of (C{sub 6}H{sub 22}N{sub 4})[(UO{sub 2})(SeO{sub 4}){sub 2}(H{sub 2}O)](H{sub 2}O) (TETAUSe) is monoclinic, P2{sub 1}/n, a=13.002(2), b=7.962(1), c=14.754(2) A, {beta}=114.077(2){sup o}, V=1394.5(3) A{sup 3}, Z=4, R{sub 1}=0.0323. The structure of (C{sub 6}H{sub 21}N{sub 4})[(UO{sub 2})(SeO{sub 4}){sub 2}(HSeO{sub 4})] (TAEAUSe) is monoclinic, P2{sub 1}/m, a=9.2218(6), b=12.2768(9), c=9.4464(7) A, {beta}=116.1650(10){sup o}, V=959.88(12) A{sup 3}, Z=2, R{sub 1}=0.0322. The inorganic structural units in these compounds are composed of uranyl pentagonal bipyramids and selenate tetrahedra. In each case, tetrahedra link bipyramids through vertex-sharing, resulting in chain or sheet topologies. The charge-density matching principle is discussed relative to the orientations of the organic molecules between the inorganic structural units. - Graphical abstract: The structures of five new inorganic-organic hybrid uranyl selenates present new structural topologies based upon chains and sheets of uranyl pentagonal bipyramids and selenate tetrahedra.

  11. The structure of monomeric and dimeric uranyl adsorption complexes on gibbsite: A combined DFT and EXAFS study

    NASA Astrophysics Data System (ADS)

    Hattori, Tatsuya; Saito, Takumi; Ishida, Keisuke; Scheinost, Andreas C.; Tsuneda, Takao; Nagasaki, Shinya; Tanaka, Satoru

    2009-10-01

    We investigated the structure of uranyl sorption complexes on gibbsite (pH 5.6-9.7) by two independent methods, density functional theory (DFT) calculations and extended X-ray absorption fine structure (EXAFS) spectroscopy at the U-L III edge. To model the gibbsite surface with DFT, we tested two Al (hydr)oxide clusters, a dimer and a hexamer. Based on polarization, structure, and relaxation energies during geometry optimization, the hexamer cluster was found to be the more appropriate model. An additional advantage of the hexamer model is that it represents both edges and basal faces of gibbsite. The DFT calculations of (monomeric) uranyl sorption complexes show an energetic preference for the corner-sharing versus the edge-sharing configuration on gibbsite edges. The energy difference is so small, however, that possibly both surface species may coexist. In contrast to the edge sites, sorption to basal sites was energetically not favorable. EXAFS spectroscopy revealed in all investigated samples the same interatomic distances of the uranyl coordination environment ( R ≈ 1.80 Å, R ≈ 2.40 Å), and towards the gibbsite surface ( RU-O ≈ 2.87 Å, RU-Al ≈ 3.38 Å). In addition, two U-U distances were observed, 3.92 Å at pH 9.7 and 4.30 Å at pH 5.6, both with coordination numbers of ˜1. The short U-U distance is close to that of the aqueous uranyl hydroxo dimer, UO 2(OH) 2, reported as 3.875 Å in the literature, but significantly longer than that of aqueous trimers (3.81-3.82 Å), suggesting sorption of uranyl dimers at alkaline pH. The longer U-U distance (4.30 Å) at acidic pH, however, is not in line with known aqueous uranyl polymer complexes. Based on the EXAFS findings we further refined dimeric surface complexes with DFT. We propose two structural models: in the acidic region, the observed long U-U distance can be explained with a distortion of the uranyl dimer to form both a corner-sharing and an edge-sharing linkage to neighboring Al octahedra

  12. The Influence of the Linker Geometry in Bis(3-hydroxy-N-methyl-pyridin-2-one) Ligands on Solution-Phase Uranyl Affinity

    SciTech Connect

    Szigethy, Geza; Raymond, Kenneth

    2010-08-12

    Seven water-soluble, tetradentate bis(3-hydroxy-N-methyl-pyridin-2-one) (bis-Me-3,2-HOPO) ligands were synthesized that vary only in linker geometry and rigidity. Solution phase thermodynamic measurements were conducted between pH 1.6 and pH 9.0 to determine the effects of these variations on proton and uranyl cation affinity. Proton affinity decreases by introduction of the solubilizing triethylene glycol group as compared to un-substituted reference ligands. Uranyl affinity was found to follow no discernable trends with incremental geometric modification. The butyl-linked 4Li-Me-3,2-HOPO ligand exhibited the highest uranyl affinity, consistent with prior in vivo decorporation results. Of the rigidly-linked ligands, the o-phenylene linker imparted the best uranyl affinity to the bis-Me-3,2-HOPO ligand platform.

  13. Potential remediation approach for uranium-contaminated groundwaters through potassium uranyl vanadate precipitation

    SciTech Connect

    Tokunaga, T.K.; Kim, Y.; Wan, J.

    2009-06-01

    Methods for remediating groundwaters contaminated with uranium (U) through precipitation under oxidizing conditions are needed because bioreduction-based approaches require indefinite supply of electron donor. Although strategies based on precipitation of some phosphate minerals within the (meta)autunite group have been considered for this purpose, thermodynamic calculations for K- and Ca-uranyl phopsphates, meta-ankoleite and autunite, predict that U concentrations will exceed the Maximum Contaminant Level (MCL = 0.13 {micro}M for U) at any pH and pCO{sub 2}, unless phosphate is maintained at much higher concentrations than the sub-{micro}M levels typically found in groundwaters. We hypothesized that potassium uranyl vanadate will control U(VI) concentrations below regulatory levels in slightly acidic to neutral solutions based on thermodynamic data available for carnotite, K{sub 2}(UO{sub 2}){sub 2}V{sub 2}O8. The calculations indicate that maintaining U concentrations below the MCL through precipitation of carnotite will be sustainable in some oxidizing waters having pH in the range of 5.5 to 7, even when dissolution of this solid phase becomes the sole supply of sub-{micro}M levels of V. Batch experiments were conducted in solutions at pH 6.0 and 7.8, chosen because of their very different predicted extents of U(VI) removal. Conditions were identified where U concentrations dropped below its MCL within 1 to 5 days of contact with oxidizing solutions containing 0.2 to 10 mM K, and 0.1 to 20 {micro}M V(V). This method may also have application in extracting (mining) U and V from groundwaters where they both occur at elevated concentrations.

  14. Pore-Scale Evaluation of Uranyl Phosphate Precipitation in a Model Groundwater System

    SciTech Connect

    Fanizza, Michael F.; Yoon, Hongkyu; Zhang, Changyong; Oostrom, Martinus; Wietsma, Thomas W.; Hess, Nancy J.; Bowden, Mark E.; Strathmann, Timothy J.; Finneran, Kevin T.; Werth, Charles J.

    2013-02-01

    The abiotic precipitation of uranium (U(VI)) was evaluated in a microfluidic pore network (i.e. micromodel) to assess the efficacy of using a phosphate amendment to immobilize uranium in groundwater. U(VI) was mixed transverse to the direction of flow with hydrogen phosphate (HPO42-), in the presence or absence of calcium (Ca2+) or sulfate (SO42-), in order to identify precipitation rates, morphology and types of minerals formed, and effects of mineral precipitates on pore blockage. Precipitation occurred over the time scale of hours to days. Relative to when only U(VI) and HPO42- were present, precipitation rates were 2.3X slower when SO42- was present, and 1.4X faster when Ca2+ was present; larger crystals formed in the presence of SO42-. Raman backscattering spectroscopy and micro X-ray diffraction (μ-XRD) results both showed that the only mineral precipitated was chernikovite, UO2HPO4•4H2O; energy dispersive x-ray spectroscopy results indicate that Ca and S are not incorporated into the chernikovite lattice. A pore scale model was developed, and simulation results of saturation ratio (SR=Q/Ksp) suggest that chernikovite is the least thermodynamically favored mineral to precipitate (0uranyl hydrogen phosphate and Na-Autunite (13uranyl orthophosphate and Ca-autunite (when Ca2+ is present) (SR>105). Fluorescent tracer studies and laser confocal microscopy images showed that densely aggregated precipitates blocked pores and reduced permeability. The results suggest that uranium precipitation with phosphate as chernikovite is rapid on the time scale of remediation for the conditions considered, and can block pores, alter fluid flow paths, and potentially limit mixing and precipitation.

  15. Precipitation and Dissolution of Uranyl Phosphates in a Microfluidic Pore Structure

    NASA Astrophysics Data System (ADS)

    Werth, C. J.; Fanizza, M.; Strathmann, T.; Finneran, K.; Oostrom, M.; Zhang, C.; Wietsma, T. W.; Hess, N. J.

    2011-12-01

    The abiotic precipitation of uranium (U(VI)) was evaluated in a microfluidic pore structure (i.e. micromodel) to assess the efficacy of using a phosphate amendment to immobilize uranium in groundwater and mitigate the risk of this contaminant to potential down-gradient receptor sites. U(VI) was mixed transverse to the direction of flow with hydrogen phosphate (HPO42-), in the presence or absence of calcium (Ca2+) or sulfate (SO42-), in order to identify precipitation rates, the morphology and types of minerals formed, and the stability of these minerals to dissolution with and without bicarbonate (HCO3-) present. Raman backscattering spectroscopy and micro X-ray diffraction (μ-XRD) results both showed that the only mineral precipitated was chernikovite (also known as hydrogen uranyl phosphate; UO2HPO4), even though the formation of other minerals were thermodynamically favored depending on the experimental conditions. Precipitation and dissolution rates varied with influent conditions. Relative to when only U(VI) and HPO42- were present, precipitation rates were 2.3 times slower when SO42- was present, and 1.4 times faster when Ca2+ was present. These rates were inversely related to the size of crystals formed during precipitation. Dissolution rates for chernikovite increased with increasing HCO3- concentrations, consistent with formation of uranyl carbonate complexes in aqueous solution, and they were the fastest for chernikovite formed in the presence of SO42-, and slowest for the chernikovite formed in the presence of Ca2+. These rates are related to the ratios of mineral-water interfacial area to mineral volume. Fluorescent tracer studies and laser confocal microscopy images showed that densely aggregated precipitates blocked pores and reduced permeability. The results suggest that changes in the solute conditions evaluated affect precipitation rates, crystal morphology, and crystal stability, but not mineral type.

  16. X-ray Absorption Spectroscopy Identifies Calcium-Uranyl-Carbonate Complexes at Environmental Concentrations

    SciTech Connect

    Kelly, Shelly D; Kemner, Kenneth M; Brooks, Scott C

    2007-01-01

    Current research on bioremediation of uranium-contaminated groundwater focuses on supplying indigenous metal-reducing bacteria with the appropriate metabolic requirements to induce microbiological reduction of soluble uranium(VI) to poorly soluble uranium(IV). Recent studies of uranium(VI) bioreduction in the presence of environmentally relevant levels of calcium revealed limited and slowed uranium(VI) reduction and the formation of a Ca-UO2-CO3 complex. However, the stoichiometry of the complex is poorly defined and may be complicated by the presence of a Na-UO2-CO3 complex. Such a complex might exist even at high calcium concentrations, as some UO2-CO3 complexes will still be present. The number of calcium and/or sodium atoms coordinated to a uranyl carbonate complex will determine the net charge of the complex. Such a change in aqueous speciation of uranium(VI) in calcareous groundwater may affect the fate and transport properties of uranium. In this paper, we present the results from X-ray absorption fine structure (XAFS) measurements of a series of solutions containing 50 lM uranium(VI) and 30 mM sodium bicarbonate, with various calcium concentrations of 0-5 mM. Use of the data series reduces the uncertainty in the number of calcium atoms bound to the UO2-CO3 complex to approximately 0.6 and enables spectroscopic identification of the Na-UO2-CO3 complex. At nearly neutral pH values, the numbers of sodium and calcium atoms bound to the uranyl triscarbonate species are found to depend on the calcium concentration, as predicted by speciation calculations.

  17. X-ray absorption spectroscopy identifies calcium-uranyl-carbonate complexes at environmental concentrations.

    SciTech Connect

    Kelly, S. D.; Kemner, K. M.; Brooks, S. C.; Biosciences Division; ORNL

    2007-01-01

    Current research on bioremediation of uranium-contaminated groundwater focuses on supplying indigenous metal-reducing bacteria with the appropriate metabolic requirements to induce microbiological reduction of soluble uranium(VI) to poorly soluble uranium(IV). Recent studies of uranium(VI) bioreduction in the presence of environmentally relevant levels of calcium revealed limited and slowed uranium(VI) reduction and the formation of a Ca-UO{sub 2}-CO{sub 3} complex. However, the stoichiometry of the complex is poorly defined and may be complicated by the presence of a Na-UO{sub 2}-CO{sub 3} complex. Such a complex might exist even at high calcium concentrations, as some UO{sub 2}-CO{sub 3} complexes will still be present. The number of calcium and/or sodium atoms coordinated to a uranyl carbonate complex will determine the net charge of the complex. Such a change in aqueous speciation of uranium(VI) in calcareous groundwater may affect the fate and transport properties of uranium. In this paper, we present the results from X-ray absorption fine structure (XAFS) measurements of a series of solutions containing 50 {micro}M uranium(VI) and 30 mM sodium bicarbonate, with various calcium concentrations of 0-5 mM. Use of the data series reduces the uncertainty in the number of calcium atoms bound to the UO{sub 2}-CO{sub 3} complex to approximately 0.6 and enables spectroscopic identification of the Na-UO{sub 2}-CO{sub 3} complex. At nearly neutral pH values, the numbers of sodium and calcium atoms bound to the uranyl triscarbonate species are found to depend on the calcium concentration, as predicted by speciation calculations.

  18. The Key Role of U28 in the Aqueous Self-Assembly of Uranyl Peroxide Nanocages.

    PubMed

    Falaise, Clément; Nyman, May

    2016-10-01

    For 11 years now, the structural diversity and aesthetic beauty of uranyl-peroxide capsules have fascinated researchers from the diverse fields of mineralogy, polyoxometalate chemistry, and nuclear fuel technologies. There is still much to be learned about the mechanisms of the self-assembly process, and the role of solution parameters including pH, alkali template, temperature, time, and others. Here we have exploited the high solubility of the UO2 (2+) /H2 O2 /LiOH aqueous system to address the effect of the hydroxide concentration. Important techniques of this study are single-crystal X-ray diffraction, small-angle X-ray scattering, and Raman spectroscopy. Three key phases dominate the solution speciation as a function of time and the LiOH/UO2 (2+) ratio: the uranyl-triperoxide monomer [UO2 (O2 )3 ](4-) and the two capsules [(UO2 )(O2 )(OH)]24 (24-) (U24 ) and [(UO2 )(O2 )1.5 ]28 (28-) (U28 ). When the LiOH/U ratio is around three, U28 forms rapidly and this cluster can be isolated in high yield and purity. This result was most surprising and challenges the hypothesis that alkali templating is the most important determinant in the cluster geometry. Moreover, analogous experiments with KOH, NH4 OH, and TEAOH (TEA=tetraethylammonium) also rapidly yield U28 , which suggests that U28 is the kinetically favored species. Complete mapping of the pH-time phase space reveals only a narrow window of the U28 dominance, which is why it was previously overlooked as an important kinetic species in this chemical system, as well as others with different counterions. PMID:27539640

  19. A Novel Chemical Nitrate Destruction Process

    SciTech Connect

    Dziewinski, J.; Marczak, S.

    1999-03-01

    Nitrates represent one of the most significant pollutant discharged to the Baltic Sea by the Sliiamae hydrometallurgical plant. This article contains a brief overview of the existing nitrate destruction technologies followed by the description of a new process developed by the authors. The new chemical process for nitrate destruction is cost effective and simple to operate. It converts the nitrate to nitrogen gas which goes to the atmosphere.

  20. Nitrate reduction in sulfate-reducing bacteria.

    PubMed

    Marietou, Angeliki

    2016-08-01

    Sulfate-reducing bacteria (SRBs) gain their energy by coupling the oxidation of organic substrate to the reduction of sulfate to sulfide. Several SRBs are able to use alternative terminal electron acceptors to sulfate such as nitrate. Nitrate-reducing SRBs have been isolated from a diverse range of environments. In order to be able to understand the significance of nitrate reduction in SRBs, we need to examine the ecology and physiology of the nitrate-reducing SRB isolates.

  1. Nitrate reductase assay using sodium nitrate for rapid detection of multidrug resistant tuberculosis

    PubMed Central

    Macedo, Maíra Bidart; Groll, Andrea Von; Fissette, Krista; Palomino, Juan Carlos; da Silva, Pedro Eduardo Almeida; Martin, Anandi

    2012-01-01

    We validated the nitrate reductase assay (NRA) for the detection of multidrug-resistant Mycobacterium tuberculosis (MDR-TB) using sodium nitrate (NaNO3) in replacement of potassium nitrate (KNO3) as nitrate source. NaNO3 is cheaper than KNO3 and has no restriction on use which facilitates the implementation of NRA to detect MDR-TB. PMID:24031916

  2. 49 CFR 176.410 - Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 2 2012-10-01 2012-10-01 false Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures. 176.410 Section 176.410 Transportation Other Regulations Relating to... nitrate and ammonium nitrate mixtures. (a) This section prescribes requirements to be observed...

  3. 49 CFR 176.410 - Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 2 2011-10-01 2011-10-01 false Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures. 176.410 Section 176.410 Transportation Other Regulations Relating to... nitrate and ammonium nitrate mixtures. (a) This section prescribes requirements to be observed...

  4. 49 CFR 176.410 - Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 2 2014-10-01 2014-10-01 false Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures. 176.410 Section 176.410 Transportation Other Regulations Relating to... nitrate and ammonium nitrate mixtures. (a) This section prescribes requirements to be observed...

  5. 49 CFR 176.410 - Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures. 176.410 Section 176.410 Transportation Other Regulations Relating to... nitrate and ammonium nitrate mixtures. (a) This section prescribes requirements to be observed...

  6. 49 CFR 176.410 - Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 2 2013-10-01 2013-10-01 false Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures. 176.410 Section 176.410 Transportation Other Regulations Relating to... nitrate and ammonium nitrate mixtures. (a) This section prescribes requirements to be observed...

  7. Nitration of Naphthol: A Laboratory Experiment.

    ERIC Educational Resources Information Center

    Mowery, Dwight F.

    1982-01-01

    Products of nitrations, upon distillation or steam distillation, may produce dermatitis in some students. A procedure for nitration of beta-naphthol producing a relatively non-volatile product not purified by steam distillation is described. Nitration of alpha-naphthol by the same procedure yields Martius Yellow dye which dyes wool yellow or…

  8. Modeling nitrate removal in a denitrification bed

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Denitrification beds are being promoted to reduce nitrate concentrations in agricultural drainage water to alleviate the adverse environmental effects associated with nitrate pollution in surface water. In this system, water flows through a trench filled with a carbon media where nitrate is transfor...

  9. Method of producing thin cellulose nitrate film

    DOEpatents

    Lupica, S.B.

    1975-12-23

    An improved method for forming a thin nitrocellulose film of reproducible thickness is described. The film is a cellulose nitrate film, 10 to 20 microns in thickness, cast from a solution of cellulose nitrate in tetrahydrofuran, said solution containing from 7 to 15 percent, by weight, of dioctyl phthalate, said cellulose nitrate having a nitrogen content of from 10 to 13 percent.

  10. 21 CFR 172.160 - Potassium nitrate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Potassium nitrate. 172.160 Section 172.160 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Preservatives § 172.160 Potassium nitrate. The food additive potassium nitrate may be safely used as a...

  11. Post-translational Regulation of Nitrate Reductase

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Nitrate reductase (NR) catalyzes the reduction of nitrate to nitrite, which is the first step in the nitrate assimilation pathway, but can also reduce nitrite to nitric oxide (NO), an important signaling molecule that is thought to mediate a wide array of of developmental and physiological processes...

  12. 21 CFR 172.160 - Potassium nitrate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Potassium nitrate. 172.160 Section 172.160 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD... nitrate. The food additive potassium nitrate may be safely used as a curing agent in the processing of...

  13. 21 CFR 172.160 - Potassium nitrate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Potassium nitrate. 172.160 Section 172.160 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Food Preservatives § 172.160 Potassium nitrate. The food additive potassium nitrate may be safely...

  14. 21 CFR 172.160 - Potassium nitrate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Potassium nitrate. 172.160 Section 172.160 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Food Preservatives § 172.160 Potassium nitrate. The food additive potassium nitrate may be safely...

  15. Efflux Of Nitrate From Hydroponically Grown Wheat

    NASA Technical Reports Server (NTRS)

    Huffaker, R. C.; Aslam, M.; Ward, M. R.

    1992-01-01

    Report describes experiments to measure influx, and efflux of nitrate from hydroponically grown wheat seedlings. Ratio between efflux and influx greater in darkness than in light; increased with concentration of nitrate in nutrient solution. On basis of experiments, authors suggest nutrient solution optimized at lowest possible concentration of nitrate.

  16. 21 CFR 172.170 - Sodium nitrate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Sodium nitrate. 172.170 Section 172.170 Food and... PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Food Preservatives § 172.170 Sodium nitrate. The food additive sodium nitrate may be safely used in or on specified foods in accordance with...

  17. 21 CFR 172.160 - Potassium nitrate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Potassium nitrate. 172.160 Section 172.160 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Food Preservatives § 172.160 Potassium nitrate. The food additive potassium nitrate may be safely...

  18. Protective effect of salivary nitrate and microbial nitrate reductase activity against caries.

    PubMed

    Doel, J J; Hector, M P; Amirtham, C V; Al-Anzan, L A; Benjamin, N; Allaker, R P

    2004-10-01

    To test the hypothesis that a combination of high salivary nitrate and high nitrate-reducing capacity are protective against dental caries, 209 children attending the Dental Institute, Barts and The London NHS Trust were examined. Salivary nitrate and nitrite levels, counts of Streptococcus mutans and Lactobacillus spp., and caries experience were recorded. Compared with control subjects, a significant reduction in caries experience was found in patients with high salivary nitrate and high nitrate-reducing ability. Production of nitrite from salivary nitrate by commensal nitrate-reducing bacteria may limit the growth of cariogenic bacteria as a result of the production of antimicrobial oxides of nitrogen, including nitric oxide. PMID:15458501

  19. Continuous flow nitration in miniaturized devices

    PubMed Central

    2014-01-01

    Summary This review highlights the state of the art in the field of continuous flow nitration with miniaturized devices. Although nitration has been one of the oldest and most important unit reactions, the advent of miniaturized devices has paved the way for new opportunities to reconsider the conventional approach for exothermic and selectivity sensitive nitration reactions. Four different approaches to flow nitration with microreactors are presented herein and discussed in view of their advantages, limitations and applicability of the information towards scale-up. Selected recent patents that disclose scale-up methodologies for continuous flow nitration are also briefly reviewed. PMID:24605161

  20. Phase diagram of ammonium nitrate

    NASA Astrophysics Data System (ADS)

    Dunuwille, M.; Yoo, C. S.

    2014-05-01

    Ammonium Nitrate (AN) has often subjected to uses in improvised explosive devices, due to its wide availability as a fertilizer and its capability of becoming explosive with slight additions of organic and inorganic compounds. Yet, the origin of enhanced energetic properties of impure AN (or AN mixtures) is neither chemically unique nor well understood -resulting in rather catastrophic disasters in the past1 and thereby a significant burden on safety in using ammonium nitrates even today. To remedy this situation, we have carried out an extensive study to investigate the phase stability of AN at high pressure and temperature, using diamond anvil cells and micro-Raman spectroscopy. The present results confirm the recently proposed phase IV-to-IV' transition above 17 GPa2 and provide new constraints for the melting and phase diagram of AN to 40 GPa and 400 °C.

  1. Deconstructing nitrate isotope dynamics in aquifers

    NASA Astrophysics Data System (ADS)

    Granger, J.

    2012-12-01

    The natural abundance N and O stable isotope ratios of nitrate provide an invaluable tool to differentiate N sources to the environment, track their dispersal, and monitor their attenuation by biological transformations. The interpretation of patterns in isotope abundances relies on knowledge of the isotope ratios of the source end-members, as well as on constraints on the isotope discrimination imposed on nitrate by respective biological processes. Emergent observations from mono-culture experiments of denitrifying bacteria reveal nitrate fractionation trends that appear at odds with trends ascribed to denitrification in soils and aquifers. This discrepancy raises the possibility that additional biological N transformations may be acting in tandem with denitrification. Here, the N and O isotope enrichments associated with nitrate removal by denitrification in aquifers are posited to bear evidence of coincident biological nitrate production - from nitrification and/or from anammox. Simulations are presented from a simple time-dependent one-box model of a groundwater mass ageing that is subject to net nitrate loss by denitrification with coincident nitrate production by nitrification or anammox. Within boundary conditions characteristic of freshwater aquifers, the apparent slope of the parallel enrichments in nitrate N and O isotopes associated with net N loss to denitrification can vary in proportion to the nitrate added simultaneous by oxidative processes. Pertinent observations from nitrate plumes in suboxic to anoxic aquifers are examined to validate this premise. In this perspective, nitrate isotope distributions suggest that we may be missing important N fluxes inherent to most aquifers.

  2. Nitrate Utilization by the Diatom Skeletonema costatum

    PubMed Central

    Serra, Juan L.; Llama, Maria J.; Cadenas, Eduardo

    1978-01-01

    Nitrate uptake has been studied in nitrogen-deficient cells of the marine diatom Skeletonema costatum. When these cells are incubated in the presence of nitrate, this ion is quickly taken up from the medium, and nitrite is excreted by the cells. Nitrite is excreted following classical saturation kinetics, its rate being independent of nitrate concentration in the incubation medium for nitrate concentration values higher than 3 micromolar. Nitrate uptake shows mixed-transfer kinetics, which can be attributed to the simultaneous contributions of mediated and diffusion transfer. Cycloheximide and p-hydroxymercuribenzoate inhibit the carrier-mediated contribution to nitrate uptake, without affecting the diffusion component. When cells are preincubated with nitrate, the net nitrogen uptake is increased. PMID:16660652

  3. Pollution of drinking water with nitrate

    SciTech Connect

    Cabel, B.; Kozicki, R.; Lahl, U.; Podbielshi, A.; Stachel, B.; Struss, S.

    1982-01-01

    The main sources of nitrate in man are food and drinking water. The legislature in West Germany intends to lower the permitted level of nitrate in drinking water from the present 90 mg/l to 50 mg/l in 1982. The European Community has issued a directive that recommends a level of only 25 mg/l, and for babies 10 mg/l nitrate should not be exceeded. At present, nitrate cannot be removed from raw water at an acceptable cost. The problem of high nitrate content is mainly one of drinking water generation from ground water. Several analyses indicate rising concentrations of nitrate in ground water in different regions of West Germany, especially in the last few years. The following sources of nitrate-contamination of ground water aquifers in West are discussed: natural sources; over-manuring of agricultural areas with natural organic fertilizers; over-manuring of agricultural areas with synthetic fertilizers.

  4. Periodic Density Functional Theory Investigation of the Uranyl Ion Sorption on Three Mineral Surfaces: A Comparative Study

    PubMed Central

    Roques, Jérôme; Veilly, Edouard; Simoni, Eric

    2009-01-01

    Canister integrity and radionuclides retention is of prime importance for assessing the long term safety of nuclear waste stored in engineered geologic depositories. A comparative investigation of the interaction of uranyl ion with three different mineral surfaces has thus been undertaken in order to point out the influence of surface composition on the adsorption mechanism(s). Periodic DFT calculations using plane waves basis sets with the GGA formalism were performed on the TiO2(110), Al(OH)3(001) and Ni(111) surfaces. This study has clearly shown that three parameters play an important role in the uranyl adsorption mechanism: the solvent (H2O) distribution at the interface, the nature of the adsorption site and finally, the surface atoms’ protonation state. PMID:19582222

  5. High performance ammonium nitrate propellant

    NASA Technical Reports Server (NTRS)

    Anderson, F. A. (Inventor)

    1979-01-01

    A high performance propellant having greatly reduced hydrogen chloride emission is presented. It is comprised of: (1) a minor amount of hydrocarbon binder (10-15%), (2) at least 85% solids including ammonium nitrate as the primary oxidizer (about 40% to 70%), (3) a significant amount (5-25%) powdered metal fuel, such as aluminum, (4) a small amount (5-25%) of ammonium perchlorate as a supplementary oxidizer, and (5) optionally a small amount (0-20%) of a nitramine.

  6. 49 CFR 176.415 - Permit requirements for Division 1.5, ammonium nitrates, and certain ammonium nitrate fertilizers.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... nitrates, and certain ammonium nitrate fertilizers. 176.415 Section 176.415 Transportation Other... requirements for Division 1.5, ammonium nitrates, and certain ammonium nitrate fertilizers. (a) Except as... Captain of the Port (COTP). (1) Ammonium nitrate UN1942, ammonium nitrate fertilizers containing more...

  7. 49 CFR 176.415 - Permit requirements for Division 1.5, ammonium nitrates, and certain ammonium nitrate fertilizers.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... nitrates, and certain ammonium nitrate fertilizers. 176.415 Section 176.415 Transportation Other... requirements for Division 1.5, ammonium nitrates, and certain ammonium nitrate fertilizers. (a) Except as... Captain of the Port (COTP). (1) Ammonium nitrate UN1942, ammonium nitrate fertilizers containing more...

  8. 49 CFR 176.415 - Permit requirements for Division 1.5, ammonium nitrates, and certain ammonium nitrate fertilizers.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... nitrates, and certain ammonium nitrate fertilizers. 176.415 Section 176.415 Transportation Other... requirements for Division 1.5, ammonium nitrates, and certain ammonium nitrate fertilizers. (a) Except as... Captain of the Port (COTP). (1) Ammonium nitrate UN1942, ammonium nitrate fertilizers containing more...

  9. 49 CFR 176.415 - Permit requirements for Division 1.5, ammonium nitrates, and certain ammonium nitrate fertilizers.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... nitrates, and certain ammonium nitrate fertilizers. 176.415 Section 176.415 Transportation Other... requirements for Division 1.5, ammonium nitrates, and certain ammonium nitrate fertilizers. (a) Except as... Captain of the Port (COTP). (1) Ammonium nitrate UN1942, ammonium nitrate fertilizers containing more...

  10. 49 CFR 176.415 - Permit requirements for Division 1.5, ammonium nitrates, and certain ammonium nitrate fertilizers.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... nitrates, and certain ammonium nitrate fertilizers. 176.415 Section 176.415 Transportation Other... requirements for Division 1.5, ammonium nitrates, and certain ammonium nitrate fertilizers. (a) Except as... Captain of the Port (COTP). (1) Ammonium nitrate UN1942, ammonium nitrate fertilizers containing more...

  11. Highly Sensitive and Selective Method for Detecting Ultratrace Levels of Aqueous Uranyl Ions by Strongly Photoluminescent-Responsive Amine-Modified Cadmium Sulfide Quantum Dots.

    PubMed

    Dutta, R K; Kumar, Ambika

    2016-09-20

    Detection of ultratrace levels of aqueous uranyl ions without using sophisticated analytical instrumentation and a tedious sample preparation method is a challenge for environmental monitoring and mitigation. Here we present a novel yet simple analytical method for highly sensitive and specific detection of uranyl ions via photoluminescence quenching of CdS quantum dots. We have demonstrated a new approach for synthesizing highly water-soluble and strong photoluminescence-emitting CdS quantum dots (i.e., CdS-MAA and CdS-MAA-TU) of sizes less than 3 nm. The structural, morphological, and optical properties of both the batches of CdS quantum dots were thoroughly characterized by XRD, high-resolution transmission electron microscopy (HRTEM), zeta potential, UV-visible absorption, and photoluminescence spectroscopy. Compared to the batch of CdS quantum dots prepared by capping with only mercaptoacetic acid (CdS-MAA), the batch prepared by capping with mercaptoacetic acid and thiourea in tandem (CdS-MAA-TU) exhibited higher quantum yield= 16.64 ± 1.02%, and more importantly, CdS-MAA-TU exhibited significantly a higher order of photoluminescence quenching responses when treated with ultratrace concentrations of uranyl ions. Under the optimized conditions, the sensitivity of detecting uranyl ion by CdS-MAA-TU was several folds better (0.316 L/ μg) than that of CdS-MAA (0.0053 (L/μg/), as determined from their respective Stern-Volmer plots. Qualitatively, CdS-MAA-TU probe can be used for visual detection of uranyl ions of concentration greater than 5 μg/L. However, the instrumental method of analysis based on photoluminescence spectroscopy confirmed the feasibility for quantitative analysis of ultratrace concentrations of uranyl ions as implied from a very low limit of detection (LoD = 0.07 μg/L) and limit of quantification (LoQ = and 0.231 μg/L). Systematic studies revealed very high selectivity for uranyl ion detection, though minor interference from Cu(2+), Pb(2

  12. Sensitivity of nitrate aerosols to ammonia emissions and to nitrate chemistry: implications for present and future nitrate optical depth

    NASA Astrophysics Data System (ADS)

    Paulot, F.; Ginoux, P.; Cooke, W. F.; Donner, L. J.; Fan, S.; Lin, M.-Y.; Mao, J.; Naik, V.; Horowitz, L. W.

    2016-02-01

    We update and evaluate the treatment of nitrate aerosols in the Geophysical Fluid Dynamics Laboratory (GFDL) atmospheric model (AM3). Accounting for the radiative effects of nitrate aerosols generally improves the simulated aerosol optical depth, although nitrate concentrations at the surface are biased high. This bias can be reduced by increasing the deposition of nitrate to account for the near-surface volatilization of ammonium nitrate or by neglecting the heterogeneous production of nitric acid to account for the inhibition of N2O5 reactive uptake at high nitrate concentrations. Globally, uncertainties in these processes can impact the simulated nitrate optical depth by up to 25 %, much more than the impact of uncertainties in the seasonality of ammonia emissions (6 %) or in the uptake of nitric acid on dust (13 %). Our best estimate for fine nitrate optical depth at 550 nm in 2010 is 0.006 (0.005-0.008). In wintertime, nitrate aerosols are simulated to account for over 30 % of the aerosol optical depth over western Europe and North America. Simulated nitrate optical depth increases by less than 30 % (0.0061-0.010) in response to projected changes in anthropogenic emissions from 2010 to 2050 (e.g., -40 % for SO2 and +38 % for ammonia). This increase is primarily driven by greater concentrations of nitrate in the free troposphere, while surface nitrate concentrations decrease in the midlatitudes following lower concentrations of nitric acid. With the projected increase of ammonia emissions, we show that better constraints on the vertical distribution of ammonia (e.g., convective transport and biomass burning injection) and on the sources and sinks of nitric acid (e.g., heterogeneous reaction on dust) are needed to improve estimates of future nitrate optical depth.

  13. Selective preconcentration of uranyl ion by silica gel phases modified with chelating compounds as inorganic polymeric ion exchangers.

    PubMed

    Mahmoud, Mohamed E; Kenawy, Ibrahim M M; Soliman, Ezzat M; Hafez, Medhat A; Akl, Magda A A; Lashein, Rabab R A

    2008-03-01

    Four chemically modified chelating silica gel phases (I - IV) with ion exchange groups were tested for their potential capability to selectively bind, extract and preconcentrate uranyl ions (UO(2)(2+)) from different aqueous solutions as well as ore samples. Factors affecting such determination processes were studied and optimized. These included the pH of the contact solution, the mass of the silica gel phase extractant, the stirring time during the application of a static technique and the eluent concentration for desorption of the surface-bound uranyl ion and interfering anions and cations. All these factors were evaluated on the basis of determinations of the distribution coefficient value (K(d)) and the percent recovery (R%). Percent recovery values of 91% for silica phase (II) and 93% for silica phase (IV) were identified in the optimum conditions. The proposed preconcentration method was further applied to uranium ore samples as well as granite samples. The determined percentage and ppm values are in good agreement with the standard assigned ones. The structure of the synthesized silica gel phases (I - IV) and their uranyl bound complexes were identified and characterized by means of infrared analysis, thermal analysis (TGA) and potentiometric titration.

  14. Selective preconcentration of uranyl ion by silica gel phases modified with chelating compounds as inorganic polymeric ion exchangers.

    PubMed

    Mahmoud, Mohamed E; Kenawy, Ibrahim M M; Soliman, Ezzat M; Hafez, Medhat A; Akl, Magda A A; Lashein, Rabab R A

    2008-03-01

    Four chemically modified chelating silica gel phases (I - IV) with ion exchange groups were tested for their potential capability to selectively bind, extract and preconcentrate uranyl ions (UO(2)(2+)) from different aqueous solutions as well as ore samples. Factors affecting such determination processes were studied and optimized. These included the pH of the contact solution, the mass of the silica gel phase extractant, the stirring time during the application of a static technique and the eluent concentration for desorption of the surface-bound uranyl ion and interfering anions and cations. All these factors were evaluated on the basis of determinations of the distribution coefficient value (K(d)) and the percent recovery (R%). Percent recovery values of 91% for silica phase (II) and 93% for silica phase (IV) were identified in the optimum conditions. The proposed preconcentration method was further applied to uranium ore samples as well as granite samples. The determined percentage and ppm values are in good agreement with the standard assigned ones. The structure of the synthesized silica gel phases (I - IV) and their uranyl bound complexes were identified and characterized by means of infrared analysis, thermal analysis (TGA) and potentiometric titration. PMID:18332547

  15. Polymer complexes: XLX. Novel supramolecular coordination modes of structure and bonding in polymeric hydrazone sulphadrugs uranyl complexes

    NASA Astrophysics Data System (ADS)

    El-Sonbati, A. Z.; Diab, M. A.; El-Shehawy, M. S.; Moqbal, M.

    2010-01-01

    Novel five binuclear polymeric dioxouranium(VI) of azosulphadrugs [(azodrug substances) azobenzene sulphonamides] were prepared for the first time. The infrared spectra of the samples were recorded and their fundamental vibration wave number was obtained. The resulting polymeric uranyl complexes were characterized on the basis of their elemental analyses, conductance and spectral (IR, NMR, and electronic spectra) data. The ligation modes of the azosulphadrugs ligands towards uranyl(II) ions were critically assigned and addressed properly on the basis of their IR and their uranyl(II) complexes. The theoretical aspects are described in terms of the well-known theory of 5d-4f transitions. The coordination geometries and electronic structures are determined from a framework for the modeling of novel polymer complexes. The values of ν3 of the prepared complexes containing UO 22+ were successfully used to calculate the force constant, FUO (1n 10 -8 N/Å) and the bond length RUO of the U-O bond. Wilson's, matrix method, Badger's formula, and Jones and El-Sonbati equations were used to calculate the U-O bond distances from the values of the stretching and interaction force constants. The most probable correlations between U-O force constant to U-O bond distance were satisfactorily discussed in terms of "Badger's rule", "Jones" and "El-Sonbati equations".

  16. Impact of uranyl-calcium-carbonato complexes on uranium(VI) adsorption to synthetic and natural sediments

    SciTech Connect

    Stewart, B.D.; Mayes, Melanie; Fendorf, Scott

    2010-01-01

    Adsorption on soil and sediment solids may decrease aqueous uranium concentrations and limit its propensity for migration in natural and contaminated settings. Uranium adsorption will be controlled in large part by its aqueous speciation, with a particular dependence on the presence of dissolved calcium and carbonate. Here we quantify the impact of uranyl speciation on adsorption to both goethite and sediments from the Hanford Clastic Dike and Oak Ridge Melton Branch Ridgetop formations. Hanford sediments were preconditioned with sodium acetate and acetic acid to remove carbonate grains, and Ca and carbonate were reintroduced at defined levels to provide a range of aqueous uranyl species. U(VI) adsorption is directly linked to UO{sub 2}{sup 2+} speciation, with the extent of retention decreasing with formation of ternary uranyl-calcium-carbonato species. Adsorption isotherms under the conditions studied are linear, and K{sub d} values decrease from 48 to 17 L kg{sup -1} for goethite, from 64 to 29 L kg{sup -1} for Hanford sediments, and from 95 to 51 L kg{sup -1} for Melton Branch sediments as the Ca concentration increases from 0 to 1 mM at pH 7. Our observations reveal that, in carbonate-bearing waters, neutral to slightly acidic pH values ({approx}5) and limited dissolved calcium are optimal for uranium adsorption.

  17. Effect of nitrate on microbial perchlorate reduction

    NASA Astrophysics Data System (ADS)

    Sun, Y.; Coates, J. D.

    2007-12-01

    Over the last decade perchlorate has been recognized as an important emerging water contaminant that poses a significant public health threat. Because of its chemical stability, low ionic charge density, and significant water solubility microbial remediation has been identified as the most feasible method for its in situ attenuation. Our previous studies have demonstrated that dissimilatory perchlorate reducing bacteria (DPRB) capable of the respiratory reduction of perchlorate into innocuous chloride are ubiquitous in soil and sedimentary environments. As part of their metabolism these organisms reduce perchlorate to chlorite which is subsequently dismutated into chloride and molecular oxygen. These initial steps are mediated by the perchlorate reductase and chlorite dismutase enzymes respectively. Previously we found that the activity of these organisms is dependent on the presence of molybdenum and is inhibited by the presence of oxygen and to different extents nitrate. However, to date, there is little understanding of the mechanisms involved in the regulation of perchlorate reduction by oxygen and nitrate. As a continuation of our studies into the factors that control DPRB activity we investigated these regulatory mechanisms in more detail as a model organism, Dechloromonas aromatica strain RCB, transitions from aerobic metabolism through nitrate reduction to perchlorate reduction. In series of growth transition studies where both nitrate and perchlorate were present, preference for nitrate to perchlorate was observed regardless of the nitrate to perchlorate ratio. Even when the organism was pre-grown anaerobically in perchlorate, nitrate was reduced prior to perchlorate. Using non-growth washed cell suspension, perchlorate- grown D. aromatica was capable of reducing both perchlorate and nitrate concomitantly suggesting the preferentially utilization of nitrate was not a result of enzyme functionality. To elucidate the mechanism for preferential utilization of

  18. Nitrate deposition and impact on Adirondack streams

    SciTech Connect

    Simonin, H.A.; Kretser, W.A.

    1997-12-31

    Acidic deposition has a great impact on water chemistry and fish populations in the Adirondack region. Although the Clean Air Act Amendments of 1990 have resulted in some reductions of sulfate deposition, nitrate deposition has not yet been well controlled, and continues to impact aquatic resources. As part of the USEPA funded Episodic Response Project four Adirondack headwater streams were intensively monitored over an 18 month period. Atmospheric deposition was also monitored at a centrally located station. The quantity of nitrate being deposited on the study watersheds was calculated based on monthly net deposition data which ranged from 0.6 kg/ha/month to 3.6 kg/ha/month. These data were then compared to the monthly export of nitrate from the watershed in these streams. Nitrate concentrations were highest in the streamwater during the spring snowmelt period prior to the time when forest vegetation actively utilizes nitrate. On an annual basis the amount of nitrate which left the watershed via stream water exceeded the amount which fell as nitrate deposition. These data are important in documenting the impact of nitrate in the acidification of Adirondack streams during the spring, which coincides with brook trout hatching. Control programs for nitrous oxide emissions are presently aimed at reducing ozone levels during the May-September period. These emissions control programs need to be expanded to also reduce nitrate deposition in the sensitive Adirondack region during the winter and spring periods when nitrate deposition has its greatest impact on aquatic resources.

  19. Structures and luminescent properties of new uranyl-based hybrid materials

    NASA Astrophysics Data System (ADS)

    Severance, Rachel C.; Vaughn, Shae Anne; Smith, Mark D.; zur Loye, Hans-Conrad

    2011-06-01

    Six uranyl coordination compounds, UO 2(OH)(PYCA) ( 1), UO 2(PYCA) 2(H 2O)·2H 2O ( 2), UO 2(PIC) 2 ( 3), UO 2(H 2O) 2(NIC) 2 ( 4), UO 2(OH)(HINIC)(INIC) ( 5), and UO 2(PYTAC) 2(H 2O) 2 ( 6) were grown as single crystals via hydrothermal synthesis (PYCA = pyrazine-2-carboxylate, PIC = picolinate, NIC = nicotinate, INIC = isonicotinate, and PYTAC = 2-(pyridin-4-yl)thiazole-5-carboxylate) to study their optical properties. All six compounds have been identified via single crystal X-ray diffraction and fully characterized via powder X-ray diffraction, infrared spectroscopy, UV-Vis spectroscopy, and fluorescence spectroscopy. Three of the complexes, 1, 3, and 6, represent new structures, and their synthesis and structural characterization is detailed within. The structures of 2, 4, and 5 have previously been reported in the literature. Coordination polymer 1 crystallizes in the orthorhombic space group Pca21 ( a = 13.5476(5) Å, b = 6.6047(2) Å, c = 8.3458(3) Å), and forms infinite 1-D chains of corner-sharing uranium polyhedra connected into 2-D layers by bridging ligands. Coordination polymer 3 crystallizes in the monoclinic space group Cc ( a = 8.4646(8) Å, b = 13.0357(11) Å, c = 11.8955(10) Å, β = 96.815(2)°), and forms ligand-bridged 1-D chains. Complex 6 crystallizes in the triclinic space group P-1 ( a = 5.6272(7) Å, b = 8.9568(10) Å, c = 10.4673(12) Å, α = 90.508(2)°, β = 104.194(2)°, γ = 91.891(2)°), and consists of isolated uranyl complexes connected via hydrogen bonds. The structures and luminescent properties of UO 2(OH)(PYCA) ( 1), UO 2(PYCA) 2(H 2O)·2H 2O ( 2), UO 2(PIC) 2 ( 3), UO 2(H 2O) 2(NIC) 2 ( 4), UO 2(OH)(HINIC)(INIC) ( 5), and UO 2(PYTAC) 2(H 2O) 2 ( 6) are discussed.

  20. Influence of uranyl speciation and iron oxides on uranium biogeochemical redox reactions

    SciTech Connect

    Stewart, B.D.; Amos, R.T.; Nico, P.S.; Fendorf, S.

    2010-03-15

    Uranium is a pollutant of concern to both human and ecosystem health. Uranium's redox state often dictates its partitioning between the aqueous- and solid-phases, and thus controls its dissolved concentration and, coupled with groundwater flow, its migration within the environment. In anaerobic environments, the more oxidized and mobile form of uranium (UO{sub 2}{sup 2+} and associated species) may be reduced, directly or indirectly, by microorganisms to U(IV) with subsequent precipitation of UO{sub 2}. However, various factors within soils and sediments may limit biological reduction of U(VI), inclusive of alterations in U(VI) speciation and competitive electron acceptors. Here we elucidate the impact of U(VI) speciation on the extent and rate of reduction with specific emphasis on speciation changes induced by dissolved Ca, and we examine the impact of Fe(III) (hydr)oxides (ferrihydrite, goethite and hematite) varying in free energies of formation on U reduction. The amount of uranium removed from solution during 100 h of incubation with S. putrefaciens was 77% with no Ca or ferrihydrite present but only 24% (with ferrihydrite) and 14% (no ferrihydrite) were removed for systems with 0.8 mM Ca. Imparting an important criterion on uranium reduction, goethite and hematite decrease the dissolved concentration of calcium through adsorption and thus tend to diminish the effect of calcium on uranium reduction. Dissimilatory reduction of Fe(III) and U(VI) can proceed through different enzyme pathways, even within a single organism, thus providing a potential second means by which Fe(III) bearing minerals may impact U(VI) reduction. We quantify rate coefficients for simultaneous dissimilatory reduction of Fe(III) and U(VI) in systems varying in Ca concentration (0 to 0.8 mM), and using a mathematical construct implemented with the reactive transport code MIN3P, we reveal the predominant influence of uranyl speciation, specifically the formation of uranyl

  1. Nitrates

    MedlinePlus

    ... or interactions with other medicines and vitamin or herbal supplements. This information should not be used as medical ... your doctor about every medicine and vitamin or herbal supplement that you are taking, so he or she ...

  2. Modeling in-situ U(VI) bioreduction by sulfate-reducing bacteria in the presence of nitrate.

    SciTech Connect

    Luo, Jian; Cirpka, Olaf; Wu, Weimin; Carley, Jack M; Nyman, Jennifer L; Jardine, Philip M; Criddle, Craig; Kitanidis, Peter K

    2007-06-01

    We present a travel-time based reactive transport model to simulate an in-situ bioremediation experiment for demonstrating enhanced bioreduction of uranium(VI). The model considers aquatic equilibrium chemistry of uranium and other groundwater constituents, uranium sorption and precipitation, and the microbial reduction of nitrate, sulfate and U(VI). Kinetic sorption/desorption of U(VI) is characterized by mass transfer between stagnant micro-pores and mobile flow zones. The model describes the succession of terminal electron accepting processes and the growth and decay of sulfate-reducing bacteria, concurrent with the enzymatic reduction of aqueous U(VI) species. The effective U(VI) reduction rate and sorption site distributions are determined by fitting the model simulation to an in-situ experiment at Oak Ridge, TN. Results show that (1) the presence of nitrate inhibits U(VI) reduction at the site; (2) the fitted effective rate of in-situ U(VI) reduction is much smaller than the values reported for laboratory experiments; (3) U(VI) sorption/desorption, which affects U(VI) bioavailability at the site, is strongly controlled by kinetics; (4) both pH and bicarbonate concentration significantly influence the sorption/desorption of U(VI), which therefore cannot be characterized by empirical isotherms; and (5) calcium-uranyl-carbonate complexes significantly influence the model performance of U(VI) reduction.

  3. Extraction and coordination studies of a carbonyl-phosphine oxide scorpionate ligand with uranyl and lanthanide(III) nitrates: structural, spectroscopic and DFT characterization of the complexes.

    PubMed

    Matveeva, Anna G; Vologzhanina, Anna V; Goryunov, Evgenii I; Aysin, Rinat R; Pasechnik, Margarita P; Matveev, Sergey V; Godovikov, Ivan A; Safiulina, Alfiya M; Brel, Valery K

    2016-03-28

    Hybrid scorpionate ligand (OPPh2)2CHCH2C(O)Me (L) was synthesized and characterized by spectroscopic methods and X-ray diffraction. The selected coordination chemistry of L with UO2(NO3)2 and Ln(NO3)3 (Ln = La, Nd, Lu) has been evaluated. The isolated mono- and binuclear complexes, namely, [UO2(NO3)2L] (1), [{UO2(NO3)L}2(μ2-O2)]·EtOH (2), [La(NO3)3L2]·2.33MeCN (3), [Nd(NO3)3L2]·3MeCN (4), [Nd(NO3)2L2]+·(NO3)−·EtOH (5) and [Lu(NO3)3L2] (6) have been characterized by IR spectroscopy and elemental analysis. Single-crystal X-ray structures have been determined for complexes 1-5. Intramolecular intraligand π-stacking interactions between two phenyl fragments of the coordinated ligand(s) were observed in all complexes 1-5. The π-stacking interaction energy was estimated from Bader's AIM theory calculations performed at the DFT level. Solution properties have been examined using IR and multinuclear ((1)H, (13)C, and (31)P) NMR spectroscopy in CD3CN and CDCl3. Coordination modes of L vary with the coordination polyhedron of the metal and solvent nature showing many coordination modes: P(O),P(O), P(O),P(O),C(O), P(O),C(O), and P(O). Preliminary extraction studies of U(VI) and Ln(III) (Ln = La, Nd, Ho, Yb) from 3.75 M HNO3 into CHCl3 show that scorpionate L extracts f-block elements (especially uranium) better than its unmodified prototype (OPPh2)2CH2.

  4. Omega-3 fatty acid deficient male rats exhibit abnormal behavioral activation in the forced swim test following chronic fluoxetine treatment: association with altered 5-HT1A and alpha2A adrenergic receptor expression.

    PubMed

    Able, Jessica A; Liu, Yanhong; Jandacek, Ronald; Rider, Therese; Tso, Patrick; McNamara, Robert K

    2014-03-01

    Omega-3 fatty acid deficiency during development leads to enduing alterations in central monoamine neurotransmission in rat brain. Here we investigated the effects of omega-3 fatty acid deficiency on behavioral and neurochemical responses to chronic fluoxetine (FLX) treatment. Male rats were fed diets with (CON, n = 34) or without (DEF, n = 30) the omega-3 fatty acid precursor alpha-linolenic acid (ALA) during peri-adolescent development (P21-P90). A subset of CON (n = 14) and DEF (n = 12) rats were administered FLX (10 mg/kg/d) through their drinking water for 30 d beginning on P60. The forced swimming test (FST) was initiated on P90, and regional brain mRNA markers of serotonin and noradrenaline neurotransmission were determined. Dietary ALA depletion led to significant reductions in frontal cortex docosahexaenoic acid (DHA, 22:6n-3) composition in DEF (-26%, p = 0.0001) and DEF + FLX (-32%, p = 0.0001) rats. Plasma FLX and norfluoxetine concentrations did not different between FLX-treated DEF and CON rats. During the 15-min FST pretest, DEF + FLX rats exhibited significantly greater climbing behavior compared with CON + FLX rats. During the 5-min test trial, FLX treatment reduced immobility and increased swimming in CON and DEF rats, and only DEF + FLX rats exhibited significant elevations in climbing behavior. DEF + FLX rats exhibited greater midbrain, and lower frontal cortex, 5-HT1A mRNA expression compared with all groups including CON + FLX rats. DEF + FLX rats also exhibited greater midbrain alpha2A adrenergic receptor mRNA expression which was positively correlated with climbing behavior in the FST. These preclinical data demonstrate that low omega-3 fatty acid status leads to abnormal behavioral and neurochemical responses to chronic FLX treatment in male rats.

  5. Channels occupancy and distortion in new lithium uranyl phosphates with three-dimensional open-frameworks

    SciTech Connect

    Renard, C.; Obbade, S.; Abraham, F.

    2009-06-15

    Three new lithium uranyl phosphates, Li{sub 2}(UO{sub 2}){sub 3}(PO{sub 4}){sub 2}O (1), Li(UO{sub 2}){sub 4}(PO{sub 4}){sub 3} (2) and Li{sub 3}(UO{sub 2}){sub 7}(PO{sub 4}){sub 5}O (3) were synthesized and studied. Powders of 1 and 2 were synthesized via solid state reaction, and single crystals of the three compounds were obtained by melting of 1 and 2 powders. The structures of the three compounds have been solved and refined from single crystal X-ray diffraction data. In the three compounds, the uranium atoms occupy square and pentagonal bipyramids. The uranium square bipyramids and phosphate tetrahedra are connected by vertices to form two types of layers with autunite sheet anion-topology {sub i}nfinity{sup 2}[(UO{sub 2})(PO{sub 4}){sub 2}]{sup 4-} and {sub i}nfinity{sup 2}[(UO{sub 2}){sub 2}(PO{sub 4}){sub 3}]{sup 5-}denoted S and D, respectively. The uranyl pentagonal bipyramids share opposite equatorial edges to form {sub i}nfinity{sup 1}[UO{sub 5}]{sup 4-} infinite chains. Mutually perpendicular chains are hung on each side of the sheets to build frameworks with non-crossing perpendicular channels that accommodate the lithium ions. Various stacking sequences of the S and D layers, S-S, D-D and S-D, generate three different frameworks in 1, 2 and 3, respectively. These compounds are similar to the recently reported vanadate analogous. However, the phosphate tetrahedra, smaller than the vanadate ones, gives distortion of the layers and a lowering of the symmetry and/or a change of periodicity. The electrical conductivity of 1 and 2 was measured using impedance spectroscopy method. The rather low conductivity of the lithium cations is explained by the crystal structure and the Li{sup +} position within the tunnels. These results corroborate those on the analogous three-dimensional alkaline uranyl vanadates. Crystallographic data: 293 K, BRUKER X8-APEX2 X-ray diffractometer, 4 K CCD detector, MoKalpha, lambda=0.71073 A, full-matrix least-squares refinement

  6. Sorption of strontium on uranyl peroxide: implications for a high-level nuclear waste repository.

    PubMed

    Sureda, Rosa; Martínez-Lladó, Xavier; Rovira, Miquel; de Pablo, Joan; Casas, Ignasi; Giménez, Javier

    2010-09-15

    Strontium-90 is considered the most important radioactive isotope in the environment and one of the most frequently occurring radionuclides in groundwaters at nuclear facilities. The uranyl peroxide studtite (UO2O2 . 4H2O) has been observed to be formed in spent nuclear fuel leaching experiments and seems to have a relatively high sorption capacity for some radionuclides. In this work, the sorption of strontium onto studtite is studied as a function of time, strontium concentration in solution and pH. The main results obtained are (a) sorption is relatively fast although slower than for cesium; (b) strontium seems to be sorbed via a monolayer coverage of the studtite surface, (c) sorption has a strong dependence on ionic strength, is negligible at acidic pH, and increases at neutral to alkaline pH (almost 100% of the strontium in solution is sorbed above pH 10). These results point to uranium secondary solid phase formation on the spent nuclear fuel as an important mechanism for strontium retention in a high-level nuclear waste repository (HLNW).

  7. Free energies and mechanisms of water exchange around Uranyl from first principles molecular dynamics

    SciTech Connect

    Atta-Fynn, Raymond; Bylaska, Eric J.; De Jong, Wibe A.

    2012-02-01

    From density functional theory (DFT) based ab initio (Car-Parrinello) metadynamics, we compute the activation energies and mechanisms of water exchange between the first and second hydration shells of aqueous Uranyl (UO{sub 2}{sup 2+}) using the primary hydration number of U as the reaction coordinate. The free energy and activation barrier of the water dissociation reaction [UO{sub 2}(OH{sub 2}){sub 5}]{sup 2+}(aq) {yields} [UO{sub 2}(OH{sub 2})4]{sup 2+}(aq) + H{sub 2}O are 0.7 kcal and 4.7 kcal/mol respectively. The free energy is in good agreement with previous theoretical (-2.7 to +1.2 kcal/mol) and experimental (0.5 to 2.2 kcal/mol) data. The associative reaction [UO{sub 2}(OH{sub 2}){sub 5}]{sup 2+}(aq) + H{sub 2}O {yields} [UO{sub 2}(OH{sub 2})6]{sup 2+}(aq) is short-lived with a free energy and activation barrier of +7.9 kcal/mol and +8.9 kca/mol respectively; it is therefore classified as associative-interchange. On the basis of the free energy differences and activation barriers, we predict that the dominant exchange mechanism between [UO{sub 2}(OH{sub 2}){sub 5}]{sup 2+}(aq) and bulk water is dissociative.

  8. Time scales for sorption-desorption and surface precipitation of uranyl on goethite.

    PubMed

    Giammar, D E; Hering, J G

    2001-08-15

    The sorption of uranium on mineral surfaces can significantly influence the fate and transport of uranium contamination in soils and groundwater. The rates of uranium adsorption and desorption on a synthetic goethite have been evaluated in batch experiments conducted at constant pH of 6 and ionic strength of 0.1 M. Adsorption and desorption reactions following the perturbation of initial states were complete within minutes to hours. Surface-solution exchange rates as measured by an isotope exchange method occur on an even shorter time scale. Although the uranium desorption rate was unaffected by the aging of uranium-goethite suspensions, the aging process appears to remove a portion of adsorbed uranium from a readily exchangeable pool. The distinction between sorption control and precipitation control of the dissolved uranium concentration was also investigated. In heterogeneous nucleation experiments, the dissolved uranium concentration was ultimately controlled by the solubility of a precipitated uranyl oxide hydrate. The X-ray diffraction pattern of the precipitate is characteristic of the mineral schoepite. Precipitation is kinetically hindered at low degrees of supersaturation. In one experiment, metastable sorption controlled dissolved uranium concentrations in excess of the solubility limit for more than 30 d.

  9. Bioaccumulation of nickel by intercalation into polycrystalline hydrogen uranyl phosphate deposited via an enzymatic mechanism

    SciTech Connect

    Bonthrone, K.M.; Basnakova, G.; Lin, F.; Macaskie, L.E.

    1996-05-01

    A Citrobacter sp. accumulates uranyl ion (UO{sub 2}{sup 2+}) as crystalline HUO{sub 2}PO{sub 4}{center_dot}4H{sub 2}O (HUP), using enzymatically generated inorganic phosphate. Ni was not removed by this mechanism, but cells already loaded with HUP removed Ni{sup 2+} by intercalative ion-exchange, forming Ni(UO{sub 2}PO{sub 4}){sub 2}{center_dot}7H{sub 2}O, as concluded by x-ray diffraction (XRD) and proton induced x-ray emission (PIXE) analyses. The loaded biomass became saturated with Ni rapidly, with a molar ratio of Ni:U in the cellbound deposit of approx. 1:6; Ni penetration was probably surface-localized. Cochallenge of the cells with Ni{sup 2+} and UO{sub 2}{sup 2+}, and glycerol 2-phosphate (phosphate donor for phosphate release and metal bioprecipitation) gave sustained removal of both metals in a flow through bioreactor, with more extensively accumulated Ni. We propose `Microbially Enhanced Chemisorption of Heavy Metals` (MECHM) to describe this hybrid mechanism of metal bioaccumulation via intercalation into preformed, biogenic crystals, and note also that MECHM can promote the removal of the transuranic radionuclide neptunium, which is difficult to achieve by conventional methods. 42 refs., 1 fig., 1 tab.

  10. Bioaccumulation of nickel by intercalation into polycrystalline hydrogen uranyl phosphate deposited via an enzymatic mechanism.

    PubMed

    Bonthrone, K M; Basnakova, G; Lin, F; Macaskie, L E

    1996-05-01

    A Citrobacter sp. accumulates uranyl ion (UO2(2+)) as crystalline HUO2PO4.4H2O (HUP), using enzymatically generated inorganic phosphate. Ni was not removed by this mechanism, but cells already loaded with HUP removed Ni2+ by intercalative ion-exchange, forming Ni(UO2PO4)2.7H2O, as concluded by x-ray diffraction (XRD) and proton induced x-ray emission (PIXE) analyses. The loaded biomass became saturated with Ni rapidly, with a molar ratio of Ni:U in the cellbound deposit of approx. 1:6; Ni penetration was probably surface-localized. Cochallenge of the cells with Ni2+ and UO2(2+), and glycerol 2-phosphate (phosphate donor for phosphate release and metal bioprecipitation) gave sustained removal of both metals in a flow through bioreactor, with more extensively accumulated Ni. We propose 'Microbially Enhanced Chemisorption of Heavy Metals' (MECHM) to describe this hybrid mechanism of metal bioaccumulation via intercalation into preformed, biogenic crystals, and note also that MECHM can promote the removal of the transuranic radionuclide neptunium, which is difficult to achieve by conventional methods.

  11. Improvement of the cloud point extraction of uranyl ions by the addition of ionic liquids.

    PubMed

    Gao, Song; Sun, Taoxiang; Chen, Qingde; Shen, Xinghai

    2013-12-15

    The cloud point extraction (CPE) of uranyl ions by different kinds of extractants in Triton X-114 (TX-114) micellar solution was investigated upon the addition of ionic liquids (ILs) with various anions, i.e., bromide (Br(-)), tetrafluoroborate (BF4(-)), hexafluorophosphate (PF6(-)) and bis[(trifluoromethyl)sulfonyl]imide (NTf2(-)). A significant increase of the extraction efficiency was found on the addition of NTf2(-) based ILs when using neutral extractant tri-octylphosphine oxide (TOPO), and the extraction efficiency kept high at both nearly neutral and high acidity. However, the CPE with acidic extractants, e.g., bis(2-ethylhexyl) phosphoric acid (HDEHP) and 8-hydroxyquinoline (8-HQ) which are only effective at nearly neutral condition, was not improved by ILs. The results of zeta potential and (19)F NMR measurements indicated that the anion NTf2(-) penetrated into the TX-114 micelles and was enriched in the surfactant-rich phase during the CPE process. Meanwhile, NTf2(-) may act as a counterion in the CPE of UO2(2+) by TOPO. Furthermore, the addition of IL increased the separation factor of UO2(2+) and La(3+), which implied that in the micelle TOPO, NTf2(-) and NO3(-) established a soft template for UO2(2+). Therefore, the combination of CPE and IL provided a supramolecular recognition to concentrate UO2(2+) efficiently and selectively.

  12. Glomerular alterations in uranyl acetate-induced acute renal failure in rabbits

    SciTech Connect

    Kobayashi, S.; Nagase, M.; Honda, N.; Hishida, A.

    1984-12-01

    The study was performed to elucidate the progression and regression of superficial and inner glomerular alterations in uranyl acetate-induced renal failure in rabbits. Fifteen hours after the drug injection, creatinine clearance (CCr) decreased to 55% of controls with slightly elevated plasma creatinine concentration (initiation stage). After 5 days, urine flow and CCr decreased to approximately zero, with severe azotemia (maintenance stage). Scanning electron microscopic observations in these stages revealed a flattening and spreading of podocyte cell bodies associated with loss of epithelial foot processes, and reduction in the density of endothelial fenestrae. These changes were more advanced in the maintenance stage. Glomerular and fenestral diameters did not significantly change in the initiation stage but increased in the maintenance stage. There was no significant difference in these morphologic alterations, however, between the superficial and inner glomeruli. Glomerular alterations reverted to normal within 14 days, with good recovery of glomerular function. The findings show no significant difference in the progression or regression of the glomerular changes between the superficial and deep cortex. These morphologic changes may play a role in the reduction of CCr observed in this model.

  13. Trend Analyses of Nitrate in Danish Groundwater

    NASA Astrophysics Data System (ADS)

    Hansen, B.; Thorling, L.; Dalgaard, T.; Erlandsen, M.

    2012-04-01

    This presentation assesses the long-term development in the oxic groundwater nitrate concentration and nitrogen (N) loss due to intensive farming in Denmark. Firstly, up to 20-year time-series from the national groundwater monitoring network enable a statistically systematic analysis of distribution, trends and trend reversals in the groundwater nitrate concentration. Secondly, knowledge about the N surplus in Danish agriculture since 1950 is used as an indicator of the potential loss of N. Thirdly, groundwater recharge CFC (Chlorofluorocarbon) age determination allows linking of the first two dataset. The development in the nitrate concentration of oxic groundwater clearly mirrors the development in the national agricultural N surplus, and a corresponding trend reversal is found in groundwater. Regulation and technical improvements in the intensive farming in Denmark have succeeded in decreasing the N surplus by 40% since the mid 1980s while at the same time maintaining crop yields and increasing the animal production of especially pigs. Trend analyses prove that the youngest (0-15 years old) oxic groundwater shows more pronounced significant downward nitrate trends (44%) than the oldest (25-50 years old) oxic groundwater (9%). This amounts to clear evidence of the effect of reduced nitrate leaching on groundwater nitrate concentrations in Denmark. Are the Danish groundwater monitoring strategy obtimal for detection of nitrate trends? Will the nitrate concentrations in Danish groundwater continue to decrease or are the Danish nitrate concentration levels now appropriate according to the Water Framework Directive?

  14. Measurement of isoprene nitrates by GCMS

    NASA Astrophysics Data System (ADS)

    Mills, Graham P.; Hiatt-Gipson, Glyn D.; Bew, Sean P.; Reeves, Claire E.

    2016-09-01

    According to atmospheric chemistry models, isoprene nitrates play an important role in determining the ozone production efficiency of isoprene; however this is very poorly constrained through observations as isoprene nitrates have not been widely measured. Measurements have been severely restricted largely due to a limited ability to measure individual isoprene nitrate isomers. An instrument based on gas chromatography/mass spectrometry (GCMS) and the associated calibration methods are described for the speciated measurements of individual isoprene nitrate isomers. Five of the primary isoprene nitrates which formed in the presence of NOx by reaction of isoprene with the hydroxyl radical (OH) in the Master Chemical Mechanism are identified using known isomers on two column phases and are fully separated on the Rtx-200 column. Three primary isoprene nitrates from the reaction of isoprene with the nitrate radical (NO3) are identified after synthesis from the already identified analogous hydroxy nitrate. A Tenax adsorbent-based trapping system allows the analysis of the majority of the known hydroxy and carbonyl primary isoprene nitrates, although not the (1,2)-IN isomer, under field-like levels of humidity and showed no impact from typical ambient concentrations of NOx and ozone.

  15. Groundwater nitrate contamination: factors and indicators.

    PubMed

    Wick, Katharina; Heumesser, Christine; Schmid, Erwin

    2012-11-30

    Identifying significant determinants of groundwater nitrate contamination is critical in order to define sensible agri-environmental indicators that support the design, enforcement, and monitoring of regulatory policies. We use data from approximately 1200 Austrian municipalities to provide a detailed statistical analysis of (1) the factors influencing groundwater nitrate contamination and (2) the predictive capacity of the Gross Nitrogen Balance, one of the most commonly used agri-environmental indicators. We find that the percentage of cropland in a given region correlates positively with nitrate concentration in groundwater. Additionally, environmental characteristics such as temperature and precipitation are important co-factors. Higher average temperatures result in lower nitrate contamination of groundwater, possibly due to increased evapotranspiration. Higher average precipitation dilutes nitrates in the soil, further reducing groundwater nitrate concentration. Finally, we assess whether the Gross Nitrogen Balance is a valid predictor of groundwater nitrate contamination. Our regression analysis reveals that the Gross Nitrogen Balance is a statistically significant predictor for nitrate contamination. We also show that its predictive power can be improved if we account for average regional precipitation. The Gross Nitrogen Balance predicts nitrate contamination in groundwater more precisely in regions with higher average precipitation.

  16. Groundwater nitrate contamination: Factors and indicators

    PubMed Central

    Wick, Katharina; Heumesser, Christine; Schmid, Erwin

    2012-01-01

    Identifying significant determinants of groundwater nitrate contamination is critical in order to define sensible agri-environmental indicators that support the design, enforcement, and monitoring of regulatory policies. We use data from approximately 1200 Austrian municipalities to provide a detailed statistical analysis of (1) the factors influencing groundwater nitrate contamination and (2) the predictive capacity of the Gross Nitrogen Balance, one of the most commonly used agri-environmental indicators. We find that the percentage of cropland in a given region correlates positively with nitrate concentration in groundwater. Additionally, environmental characteristics such as temperature and precipitation are important co-factors. Higher average temperatures result in lower nitrate contamination of groundwater, possibly due to increased evapotranspiration. Higher average precipitation dilutes nitrates in the soil, further reducing groundwater nitrate concentration. Finally, we assess whether the Gross Nitrogen Balance is a valid predictor of groundwater nitrate contamination. Our regression analysis reveals that the Gross Nitrogen Balance is a statistically significant predictor for nitrate contamination. We also show that its predictive power can be improved if we account for average regional precipitation. The Gross Nitrogen Balance predicts nitrate contamination in groundwater more precisely in regions with higher average precipitation. PMID:22906701

  17. The Influence of Linker Geometry on Uranyl Complexation by Rigidly-Linked Bis(3-hydroxy-N-methyl-pyridin-2-one)

    SciTech Connect

    Szigethy, Geza; Raymond, Kenneth

    2010-04-22

    A series of bis(3-hydroxy-N-methyl-pyridin-2-one) ligands was synthesized, and their respective uranyl complexes were characterized by single crystal X-ray diffraction analyses. These structures were inspected for high-energy conformations and evaluated using a series of metrics to measure co-planarity of chelating moieties with each other and the uranyl coordination plane, as well as to measure coordinative crowding about the uranyl dication. Both very short (ethyl, 3,4-thiophene and o-phenylene) and very long ({alpha},{alpha}{prime}-m-xylene and 1,8-fluorene) linkers provide optimal ligand geometries about the uranyl cation, resulting in planar, unstrained molecular arrangements. The planarity of the rigid linkers also suggests there is a degree of pre-organization for a planar coordination mode that is ideal for uranyl-selective ligand design. Comparison of intramolecular N{sub amide}-O{sub phenolate} distances and {sup 1}H NMR chemical shifts of amide protons supports earlier results that short linkers provide the optimal geometry for intramolecular hydrogen bonding.

  18. Phase Diagram of Ammonium Nitrate

    NASA Astrophysics Data System (ADS)

    Dunuwille, Mihindra; Yoo, Choong-Shik

    2013-06-01

    Ammonium Nitrate (AN) has often been subjected to uses in improvised explosive devices, due to its wide availability as a fertilizer and its capability of becoming explosive with slight additions of organic and inorganic compounds. Yet, the origin of enhanced energetic properties of impure AN (or AN mixtures) is neither chemically unique nor well understood - resulting in rather catastrophic disasters in the past1 and thereby a significant burden on safety, in using ammonium nitrates even today. To remedy this situation, we have carried out an extensive study to investigate the phase stability of AN, in different chemical environments, at high pressure and temperature, using diamond anvil cells and micro-Raman spectroscopy. The present results confirm the recently proposed phase IV-to-IV' transition above 15 GPa2 and provide new constraints for the melting and phase diagram of AN to 40 GPa and 673 K. The present study has been supported by the U.S. DHS under Award Number 2008-ST-061-ED0001.

  19. Peroxyacetyl nitrate and peroxypropionyl nitrate in Porto Alegre, Brazil

    NASA Astrophysics Data System (ADS)

    Grosjean, Eric; Grosjean, Daniel; Woodhouse, Luis F.; Yang, Yueh-Jiun

    For 41 days between 25 May 1996 and 27 March 1997, peroxyacetyl nitrate (PAN) and peroxypropionyl nitrate (PPN) have been measured by electron capture gas chromatography at Santa Rita near Porto Alegre, RS, Brazil, where light-duty vehicles used either ethanol or a gasoline-MTBE blend. Daily maximum concentrations ranged from 0.19 to 6.67 ppb for PAN and 0.06 to 0.72 ppb for PPN. Linear regression of maximum PPN vs. maximum PAN yielded a slope of 0.105±0.004 ( R2=0.974). Diurnal variations of ambient PAN often followed those of ozone with respect to time of day but not with respect to amplitude. This was reflected in the large relative standard deviations associated with the study-averaged PAN/ozone concentration ratio, 0.037±0.105 (ppb/ppb, n=789) and the maximum PAN/maximum ozone concentration ratio, 0.028±0.015 (ppb/ppb, range 0.005-0.078, n=41). On several days PAN accounted for large fractions of the total ambient NO x in the late morning and afternoon hours, e.g., PAN/NO x⩽0.58 and PAN/(NO x-NO) ⩽0.76 on 27 March 1997. The amount of PAN lost by thermal decomposition (TPAN) was comparable in magnitude to that present in ambient air. The ratios TPAN/(PAN+TPAN) were up to 0.53, 0.67 and 0.64 during the warm afternoons of 25, 26 and 27 March 1997, respectively. The highest calculated value of TPAN was 5.6 ppb on 27 March 1997. On that day the 24 h-averaged value of TPAN (1.01 ppb) was nearly the same as that of PAN (1.09 ppb). Using computer kinetic modeling (SAPRC 97 chemical mechanism) and sensitivity analysis of VOC incremental reactivity, we ranked VOC present in Porto Alegre ambient air for their importance as precursors to PAN and to PPN. Using as input data the averages of VOC concentrations measured in downtown Porto Alegre during the ca. 1 yr period March 1996-April 1997, we calculated that the most important precursors to PAN and PPN were the SAPRC 97 model species ARO2 (which includes the aromatics xylenes, trimethylbenzenes, ethyltoluenes, etc

  20. Challenges with nitrate therapy and nitrate tolerance: prevalence, prevention, and clinical relevance.

    PubMed

    Thadani, Udho

    2014-08-01

    Nitrate therapy has been an effective treatment for ischemic heart disease for over 100 years. The anti-ischemic and exercise-promoting benefits of sublingually administered nitrates are well established. Nitroglycerin is indicated for the relief of an established attack of angina and for prophylactic use, but its effects are short lived. In an effort to increase the duration of beneficial effects, long-acting orally administered and topical applications of nitrates have been developed; however, following their continued or frequent daily use, patients soon develop tolerance to these long-acting nitrate preparations. Once tolerance develops, patients begin losing the protective effects of the long-acting nitrate therapy. By providing a nitrate-free interval, or declining nitrate levels at night, one can overcome or reduce the development of tolerance, but cannot provide 24-h anti-anginal and anti-ischemic protection. In addition, patients may be vulnerable to occurrence of rebound angina and myocardial ischemia during periods of absent nitrate levels at night and early hours of the morning, and worsening of exercise capacity prior to the morning dose of the medication. This has been a concern with nitroglycerin patches but not with oral formulations of isosorbide-5 mononitrates, and has not been adequately studied with isosorbide dinitrate. This paper describes problems associated with nitrate tolerance, reviews mechanisms by which nitrate tolerance and loss of efficacy develop, and presents strategies to avoid nitrate tolerance and maintain efficacy when using long-acting nitrate formulations.

  1. Arabidopsis Nitrate Transporter NRT1.9 Is Important in Phloem Nitrate Transport[W][OA

    PubMed Central

    Wang, Ya-Yun; Tsay, Yi-Fang

    2011-01-01

    This study of the Arabidopsis thaliana nitrate transporter NRT1.9 reveals an important function for a NRT1 family member in phloem nitrate transport. Functional analysis in Xenopus laevis oocytes showed that NRT1.9 is a low-affinity nitrate transporter. Green fluorescent protein and β-glucuronidase reporter analyses indicated that NRT1.9 is a plasma membrane transporter expressed in the companion cells of root phloem. In nrt1.9 mutants, nitrate content in root phloem exudates was decreased, and downward nitrate transport was reduced, suggesting that NRT1.9 may facilitate loading of nitrate into the root phloem and enhance downward nitrate transport in roots. Under high nitrate conditions, the nrt1.9 mutant showed enhanced root-to-shoot nitrate transport and plant growth. We conclude that phloem nitrate transport is facilitated by expression of NRT1.9 in root companion cells. In addition, enhanced root-to-shoot xylem transport of nitrate in nrt1.9 mutants points to a negative correlation between xylem and phloem nitrate transport. PMID:21571952

  2. REDUCTION OF NITRATE THROUGH THE USE OF NITRATE REDUCTASE FOR THE SMARTCHEM AUTOANALYZER

    EPA Science Inventory

    The standard method for the determination of nitrate in drinking water, USEPA Method 353.2 “Determination of Nitrate-Nitrite by Automated Colorimetry,” employs cadmium as the reductant for the conversion of nitrate to nitrite. The nitrite is then analyzed colorimetrically by way ...

  3. Removal of Nitrate from Groundwater by Cyanobacteria: Quantitative Assessment of Factors Influencing Nitrate Uptake

    PubMed Central

    Hu, Qiang; Westerhoff, Paul; Vermaas, Wim

    2000-01-01

    The feasibility of biologically removing nitrate from groundwater was tested by using cyanobacterial cultures in batch mode under laboratory conditions. Results demonstrated that nitrate-contaminated groundwater, when supplemented with phosphate and some trace elements, can be used as growth medium supporting vigorous growth of several strains of cyanobacteria. As cyanobacteria grew, nitrate was removed from the water. Of three species tested, Synechococcus sp. strain PCC 7942 displayed the highest nitrate uptake rate, but all species showed rapid removal of nitrate from groundwater. The nitrate uptake rate increased proportionally with increasing light intensity up to 100 μmol of photons m−2 s−1, which parallels photosynthetic activity. The nitrate uptake rate was affected by inoculum size (i.e., cell density), fixed-nitrogen level in the cells in the inoculum, and aeration rate, with vigorously aerated, nitrate-sufficient cells in mid-logarithmic phase having the highest long-term nitrate uptake rate. Average nitrate uptake rates up to 0.05 mM NO3− h−1 could be achieved at a culture optical density at 730 nm of 0.5 to 1.0 over a 2-day culture period. This result compares favorably with those reported for nitrate removal by other cyanobacteria and algae, and therefore effective nitrate removal from groundwater using this organism could be anticipated on large-scale operations. PMID:10618214

  4. Safety in the Chemical Laboratory: Nitric Acid, Nitrates, and Nitro Compounds.

    ERIC Educational Resources Information Center

    Bretherick, Leslie

    1989-01-01

    Discussed are the potential hazards associated with nitric acid, inorganic and organic nitrate salts, alkyl nitrates, acyl nitrates, aliphatic nitro compounds, aromatic nitro compounds, and nitration reactions. (CW)

  5. Resistance to Botrytis cinerea in sitiens, an Abscisic Acid-Deficient Tomato Mutant, Involves Timely Production of Hydrogen Peroxide and Cell Wall Modifications in the Epidermis1[C][W][OA

    PubMed Central

    Asselbergh, Bob; Curvers, Katrien; França, Soraya C.; Audenaert, Kris; Vuylsteke, Marnik; Van Breusegem, Frank; Höfte, Monica

    2007-01-01

    Plant defense mechanisms against necrotrophic pathogens, such as Botrytis cinerea, are considered to be complex and to differ from those that are effective against biotrophs. In the abscisic acid-deficient sitiens tomato (Solanum lycopersicum) mutant, which is highly resistant to B. cinerea, accumulation of hydrogen peroxide (H2O2) was earlier and stronger than in the susceptible wild type at the site of infection. In sitiens, H2O2 accumulation was observed from 4 h postinoculation (hpi), specifically in the leaf epidermal cell walls, where it caused modification by protein cross-linking and incorporation of phenolic compounds. In wild-type tomato plants, H2O2 started to accumulate 24 hpi in the mesophyll layer and was associated with spreading cell death. Transcript-profiling analysis using TOM1 microarrays revealed that defense-related transcript accumulation prior to infection was higher in sitiens than in wild type. Moreover, further elevation of sitiens defense gene expression was stronger than in wild type 8 hpi both in number of genes and in their expression levels and confirmed a role for cell wall modification in the resistant reaction. Although, in general, plant defense-related reactive oxygen species formation facilitates necrotrophic colonization, these data indicate that timely hyperinduction of H2O2-dependent defenses in the epidermal cell wall can effectively block early development of B. cinerea. PMID:17573540

  6. Nitrate Reduction Functional Genes and Nitrate Reduction Potentials Persist in Deeper Estuarine Sediments. Why?

    PubMed Central

    Papaspyrou, Sokratis; Smith, Cindy J.; Dong, Liang F.; Whitby, Corinne; Dumbrell, Alex J.; Nedwell, David B.

    2014-01-01

    Denitrification and dissimilatory nitrate reduction to ammonium (DNRA) are processes occurring simultaneously under oxygen-limited or anaerobic conditions, where both compete for nitrate and organic carbon. Despite their ecological importance, there has been little investigation of how denitrification and DNRA potentials and related functional genes vary vertically with sediment depth. Nitrate reduction potentials measured in sediment depth profiles along the Colne estuary were in the upper range of nitrate reduction rates reported from other sediments and showed the existence of strong decreasing trends both with increasing depth and along the estuary. Denitrification potential decreased along the estuary, decreasing more rapidly with depth towards the estuary mouth. In contrast, DNRA potential increased along the estuary. Significant decreases in copy numbers of 16S rRNA and nitrate reducing genes were observed along the estuary and from surface to deeper sediments. Both metabolic potentials and functional genes persisted at sediment depths where porewater nitrate was absent. Transport of nitrate by bioturbation, based on macrofauna distributions, could only account for the upper 10 cm depth of sediment. A several fold higher combined freeze-lysable KCl-extractable nitrate pool compared to porewater nitrate was detected. We hypothesised that his could be attributed to intracellular nitrate pools from nitrate accumulating microorganisms like Thioploca or Beggiatoa. However, pyrosequencing analysis did not detect any such organisms, leaving other bacteria, microbenthic algae, or foraminiferans which have also been shown to accumulate nitrate, as possible candidates. The importance and bioavailability of a KCl-extractable nitrate sediment pool remains to be tested. The significant variation in the vertical pattern and abundance of the various nitrate reducing genes phylotypes reasonably suggests differences in their activity throughout the sediment column. This

  7. Alkali-metal ion coordination in uranyl(VI) poly-peroxo complexes in solution, inorganic analogues to crown-ethers. Part 2. Complex formation in the tetramethyl ammonium-, Li(+)-, Na(+)- and K(+)-uranyl(VI)-peroxide-carbonate systems.

    PubMed

    Zanonato, Pier Luigi; Szabó, Zoltán; Vallet, Valerie; Di Bernardo, Plinio; Grenthe, Ingmar

    2015-10-01

    The constitution and equilibrium constants of ternary uranyl(vi) peroxide carbonate complexes [(UO2)p(O2)q(CO3)r](2(p-q-r)) have been determined at 0 °C in 0.50 M MNO3, M = Li, K, and TMA (tetramethyl ammonium), ionic media using potentiometric and spectrophotometric data; (17)O NMR data were used to determine the number of complexes present. The formation of cyclic oligomers, "[(UO2)(O2)(CO3)]n", n = 4, 5, 6, with different stoichiometries depending on the ionic medium used, suggests that Li(+), Na(+), K(+) and TMA ions act as templates for the formation of uranyl peroxide rings where the uranyl-units are linked by μ-η(2)-η(2) bridged peroxide-ions. The templating effect is due to the coordination of the M(+)-ions to the uranyl oxygen atoms, where the coordination of Li(+) results in the formation of Li[(UO2)(O2)(CO3)]4(7-), Na(+) and K(+) in the formation of Na/K[(UO2)(O2)(CO3)]5(9-) complexes, while the large tetramethyl ammonium ion promotes the formation of two oligomers, TMA[(UO2)(O2)(CO3)]5(9-) and TMA[(UO2)(O2)(CO3)]6(11-). The NMR spectra demonstrate that the coordination of Na(+) in the five- and six-membered oligomers is significantly stronger than that of TMA(+); these observations suggest that the templating effect is similar to the one observed in the synthesis of crown-ethers. The NMR experiments also demonstrate that the exchange between TMA[(UO2)(O2)(CO3)]5(9-) and TMA[(UO2)(O2)(CO3)]6(11-) is slow on the (17)O chemical shift time-scale, while the exchange between TMA[(UO2)(O2)(CO3)]6(11-) and Na[(UO2)(O2)(CO3)]6(11-) is fast. There was no indication of the presence of large clusters of the type identified by Burns and Nyman (M. Nyman and P. C. Burns, Chem. Soc. Rev., 2012, 41, 7314-7367) and possible reasons for this and the implications for the synthesis of large clusters are briefly discussed.

  8. 76 FR 46907 - Ammonium Nitrate Security Program

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-03

    ... Federal Bureau of Investigation FR Federal Register HMR Hazardous Materials Regulations HMT Hazardous... ``Secure Handling of Ammonium Nitrate Program'' on October 29, 2008. See 73 FR 64280. The ANPRM solicited... interacting with state and local governments regarding ammonium nitrate security. ] See 73 FR 64280,...

  9. Dietary Nitrate, Nitric Oxide, and Cardiovascular Health.

    PubMed

    Bondonno, Catherine P; Croft, Kevin D; Hodgson, Jonathan M

    2016-09-01

    Emerging evidence strongly suggests that dietary nitrate, derived in the diet primarily from vegetables, could contribute to cardiovascular health via effects on nitric oxide (NO) status. NO plays an essential role in cardiovascular health. It is produced via the classical L-arginine-NO-synthase pathway and the recently discovered enterosalivary nitrate-nitrite-NO pathway. The discovery of this alternate pathway has highlighted dietary nitrate as a candidate for the cardioprotective effect of a diet rich in fruit and vegetables. Clinical trials with dietary nitrate have observed improvements in blood pressure, endothelial function, ischemia-reperfusion injury, arterial stiffness, platelet function, and exercise performance with a concomitant augmentation of markers of NO status. While these results are indicative of cardiovascular benefits with dietary nitrate intake, there is still a lingering concern about nitrate in relation to methemoglobinemia, cancer, and cardiovascular disease. It is the purpose of this review to present an overview of NO and its critical role in cardiovascular health; to detail the observed vascular benefits of dietary nitrate intake through effects on NO status as well as to discuss the controversy surrounding the possible toxic effects of nitrate.

  10. Intravesical silver nitrate for refractory hemorrhagic cystitis

    PubMed Central

    Montgomery, Brian D.; Boorjian, Stephen A.; Ziegelmann, Matthew J.; Joyce, Daniel D.; Linder, Brian J.

    2016-01-01

    Objective Hemorrhagic cystitis is a challenging clinical entity with limited evidence available to guide treatment. The use of intravesical silver nitrate has been reported, though supporting literature is sparse. Here, we sought to assess outcomes of patients treated with intravesical silver nitrate for refractory hemorrhagic cystitis. Material and methods We identified nine patients with refractory hemorrhagic cystitis treated at our institution with intravesical silver nitrate between 2000–2015. All patients had failed previous continuous bladder irrigation with normal saline and clot evacuation. Treatment success was defined as requiring no additional therapy beyond normal saline irrigation after silver nitrate instillation prior to hospital discharge. Results Median patient age was 80 years (IQR 73, 82). Radiation was the most common etiology for hemorrhagic cystitis 89% (8/9). Two patients underwent high dose (0.1%–0.4%) silver nitrate under anesthesia, while the remaining seven were treated with doses from 0.01% to 0.1% via continuous bladder irrigation for a median of 3 days (range 2–4). All nine patients (100%) had persistent hematuria despite intravesical silver nitrate therapy, requiring additional interventions and red blood cell transfusion during the hospitalization. There were no identified complications related to intravesical silver nitrate instillation. Conclusion Although well tolerated, we found that intravesical silver nitrate was ineffective for bleeding control, suggesting a limited role for this agent in the management of patients with hemorrhagic cystitis.

  11. COMPARTMENTAL MODEL OF NITRATE RETENTION IN STREAMS

    EPA Science Inventory

    A compartmental modeling approach is presented to route nitrate retention along a cascade of stream reach sections. A process transfer function is used for transient storage equations with first order reaction terms to represent nitrate uptake in the free stream, and denitrifica...

  12. Intravesical silver nitrate for refractory hemorrhagic cystitis

    PubMed Central

    Montgomery, Brian D.; Boorjian, Stephen A.; Ziegelmann, Matthew J.; Joyce, Daniel D.; Linder, Brian J.

    2016-01-01

    Objective Hemorrhagic cystitis is a challenging clinical entity with limited evidence available to guide treatment. The use of intravesical silver nitrate has been reported, though supporting literature is sparse. Here, we sought to assess outcomes of patients treated with intravesical silver nitrate for refractory hemorrhagic cystitis. Material and methods We identified nine patients with refractory hemorrhagic cystitis treated at our institution with intravesical silver nitrate between 2000–2015. All patients had failed previous continuous bladder irrigation with normal saline and clot evacuation. Treatment success was defined as requiring no additional therapy beyond normal saline irrigation after silver nitrate instillation prior to hospital discharge. Results Median patient age was 80 years (IQR 73, 82). Radiation was the most common etiology for hemorrhagic cystitis 89% (8/9). Two patients underwent high dose (0.1%–0.4%) silver nitrate under anesthesia, while the remaining seven were treated with doses from 0.01% to 0.1% via continuous bladder irrigation for a median of 3 days (range 2–4). All nine patients (100%) had persistent hematuria despite intravesical silver nitrate therapy, requiring additional interventions and red blood cell transfusion during the hospitalization. There were no identified complications related to intravesical silver nitrate instillation. Conclusion Although well tolerated, we found that intravesical silver nitrate was ineffective for bleeding control, suggesting a limited role for this agent in the management of patients with hemorrhagic cystitis. PMID:27635296

  13. NITRATE CONTAMINATION OF GROUND WATER (GW-761)

    EPA Science Inventory

    The occurrence of nitrate and related compounds in ground water is discussed from the perspectives of its natural as well as anthropogenic origins. A brief explanation of the nitrogen cycle touches on the production as well as utilization of ammonia, nitrite, nitrate, and nitrog...

  14. The contributions of nitrate uptake and efflux to isotope fractionation during algal nitrate assimilation

    NASA Astrophysics Data System (ADS)

    Karsh, K. L.; Trull, T. W.; Sigman, D. M.; Thompson, P. A.; Granger, J.

    2014-05-01

    In order to strengthen environmental application of nitrate N and O isotopes, we measured the N and O isotopic fractionation associated with cellular nitrate uptake and efflux in the nitrate-assimilating marine diatom Thalassiosira weissflogii. We isolated nitrate uptake and efflux from nitrate reduction by growing the cells in the presence of tungsten, which substitutes for molybdenum in assimilatory nitrate reductase, yielding an inactive enzyme. After growth on ammonium and then N starvation, cells were exposed to nitrate. Numerical models fit to the evolution of intracellular nitrate concentration and N and O isotopic composition yielded distinct N isotope effects (15ɛ) for nitrate uptake and nitrate efflux (2.0 ± 0.3‰ and 1.2 ± 0.4‰, respectively). The O isotope effects (18ɛ) for nitrate uptake and nitrate efflux were indistinguishable (2.8 ± 0.6‰), yielding a ratio of O to N isotopic fractionation for uptake of 1.4 ± 0.4 and for efflux of 2.3 ± 0.9. The 15ɛ for nitrate uptake can account for at most 40% of the organism-level N isotope effect (15ɛorg) measured in laboratory studies of T. weissflogii and in the open ocean (typically 5‰ or greater). This observation supports previous evidence that most isotope fractionation during nitrate assimilation is due to intracellular nitrate reduction, with nitrate efflux allowing the signal to be communicated to the environment. An O to N fractionation ratio (18ɛorg:15ɛorg) of ˜1 has been measured for nitrate assimilation in algal cultures and linked to the N and O isotope effects of nitrate reductase. Our results suggest that the ratios of O to N fractionation for both nitrate uptake and efflux may be distinct from a ratio of 1, to a degree that could cause the net 18ɛorg:15ɛorg to rise appreciably above 1 when 15ɛorg is low (e.g., yielding a ratio of 1.1 when 15ɛorg is 5‰). However, field and culture studies have consistently measured nearly equivalent fractionation of N and O isotopes in

  15. Topologically and geometrically flexible structural units in seven new organically templated uranyl selenates and selenite–selenates

    SciTech Connect

    Gurzhiy, Vladislav V.

    2015-09-15

    Single crystals of seven novel uranyl oxysalts of selenium with protonated methylamine molecules, [C{sub 2}H{sub 8}N]{sub 2}[(UO{sub 2})(SeO{sub 4}){sub 2}(H{sub 2}O)] (I), [C{sub 2}H{sub 8}N]{sub 2}[(UO{sub 2}){sub 2}(SeO{sub 4}){sub 3}(H{sub 2}O)] (II), [C{sub 4}H{sub 15}N{sub 3}][H{sub 3}O]{sub 0.5}[(UO{sub 2}){sub 2}(SeO{sub 4}){sub 2.93}(SeO{sub 3}){sub 0.07}(H{sub 2}O)](NO{sub 3}){sub 0.5} (III), [C{sub 2}H{sub 8}N]{sub 3}[H{sub 5}O{sub 2}][(UO{sub 2}){sub 2}(SeO{sub 4}){sub 3}(H{sub 2}O){sub 2}]{sub 2}(H{sub 2}O){sub 5} (IV), [C{sub 2}H{sub 8}N]{sub 2}[H{sub 3}O][(UO{sub 2}){sub 3}(SeO{sub 4}){sub 4}(HSeO{sub 3})(H{sub 2}O)](H{sub 2}SeO{sub 3}){sub 0.2} (V), [C{sub 4}H{sub 12}N]{sub 3}[H{sub 3}O][(UO{sub 2}){sub 3}(SeO{sub 4}){sub 5}(H{sub 2}O)] (VI), and [C{sub 2}H{sub 8}N]{sub 3}(C{sub 2}H{sub 7}N)[(UO{sub 2}){sub 3}(SeO{sub 4}){sub 4}(HSeO{sub 3})(H{sub 2}O)] (VII) have been prepared by isothermal evaporation from aqueous solutions. Their crystal structures have been solved by direct methods and their uranyl selenate and selenite–selenate units investigated using black-and-white graphs from the viewpoints of topology of interpolyhedral linkages and isomeric variations. The crystal structure of IV is based upon complex layers with unique topology, which has not been observed previously in uranyl selenates. Investigations of the statistics and local distribution of the U–O{sub br}–Se bond angles demonstrates that shorter angles associate with undulations, whereas larger angles correspond to planar areas of the uranyl selenite layers. - Graphical abstract: Crystal structures of the seven novel Se-contaning uranyl oxysalts that contain protonated organic molecules as interlayer species have been investigated from the viewpoints of topology of interpolyhedral linkages, isomeric variations and flexibility of structural units. - Highlights: • Single crystals of seven novel uranyl oxysalts were prepared by evaporation method. • The graph theory was used

  16. PREPARATION OF DIBASIC ALUMINUM NITRATE

    DOEpatents

    Gresky, A.T.; Nurmi, E.O.; Foster, D.L.; Wischow, R.P.; Savolainen, J.E.

    1960-04-01

    A method is given for the preparation and recovery of basic aluminum nltrates having an OH: Al ratio of at least two, comprising two steps. First, metallic aluminum is dissolved in aqueous Al(NO/sub 3/)/sub 3/, in the presence of a small quantity of elemental or ionic mercury, to increase its Al: NO/sub 3/ ratio into the range 1 to 1.2. The resulting aqueous solution is then added to an excess of a special organic solvent, typically a mixture of five parts methanol and six parts diethyl ether, whereupon the basic aluminum nitrate, e.g. Al/sub 6/(OH)/sub 13/-(NO/sub 3/)/sub 5/, recoverably precipitates.

  17. Phase diagram of ammonium nitrate.

    PubMed

    Dunuwille, Mihindra; Yoo, Choong-Shik

    2013-12-01

    Ammonium Nitrate (AN) is a fertilizer, yet becomes an explosive upon a small addition of chemical impurities. The origin of enhanced chemical sensitivity in impure AN (or AN mixtures) is not well understood, posing significant safety issues in using AN even today. To remedy the situation, we have carried out an extensive study to investigate the phase stability of AN and its mixtures with hexane (ANFO-AN mixed with fuel oil) and Aluminum (Ammonal) at high pressures and temperatures, using diamond anvil cells (DAC) and micro-Raman spectroscopy. The results indicate that pure AN decomposes to N2, N2O, and H2O at the onset of the melt, whereas the mixtures, ANFO and Ammonal, decompose at substantially lower temperatures. The present results also confirm the recently proposed phase IV-IV' transition above 17 GPa and provide new constraints for the melting and phase diagram of AN to 40 GPa and 400°C.

  18. Phase diagram of ammonium nitrate

    NASA Astrophysics Data System (ADS)

    Dunuwille, Mihindra; Yoo, Choong-Shik

    2013-12-01

    Ammonium Nitrate (AN) is a fertilizer, yet becomes an explosive upon a small addition of chemical impurities. The origin of enhanced chemical sensitivity in impure AN (or AN mixtures) is not well understood, posing significant safety issues in using AN even today. To remedy the situation, we have carried out an extensive study to investigate the phase stability of AN and its mixtures with hexane (ANFO-AN mixed with fuel oil) and Aluminum (Ammonal) at high pressures and temperatures, using diamond anvil cells (DAC) and micro-Raman spectroscopy. The results indicate that pure AN decomposes to N2, N2O, and H2O at the onset of the melt, whereas the mixtures, ANFO and Ammonal, decompose at substantially lower temperatures. The present results also confirm the recently proposed phase IV-IV' transition above 17 GPa and provide new constraints for the melting and phase diagram of AN to 40 GPa and 400°C.

  19. Nitrate removal from drinking water -- Review

    SciTech Connect

    Kapoor, A.; Viraraghavan, T.

    1997-04-01

    Nitrate concentrations in surface water and especially in ground water have increased in Canada, the US, Europe, and other areas of the world. This trend has raised concern because nitrates cause methemoglobiinemia in infants. Several treatment processes including ion exchange, biological denitrification, chemical denitrification, reverse osmosis, electrodialysis, and catalytic denitrification can remove nitrates from water with varying degrees of efficiency, cost, and ease of operation. Available technical data, experience, and economics indicate that ion exchange and biological denitrification are more acceptable for nitrate removal than reverse osmosis. Ion exchange is more viable for ground water while biological denitrification is the preferred alternative for surface water. This paper reviews the developments in the field of nitrate removal processes.

  20. Use of nitrates in ischemic heart disease.

    PubMed

    Giuseppe, Cocco; Paul, Jerie; Hans-Ulrich, Iselin

    2015-01-01

    Short-acting nitrates are beneficial in acute myocardial ischemia. However, many unresolved questions remain about the use of long-acting nitrates in stable ischemic heart disease. The use of long-acting nitrates is weakened by the development of endothelial dysfunction and tolerance. Also, we currently ignore whether lower doses of transdermal nitroglycerin would be better than those presently used. Multivariate analysis data from large nonrandomized studies suggested that long-acting nitrates increase the incidence of acute coronary syndromes, while data from another multivariate study indicate that they have positive effects. Because of methodological differences and open questions, the two studies cannot be compared. A study in Japanese patients with vasospastic angina has shown that, when compared with calcium antagonists, long-acting nitrates do not improve long-term prognosis and that the risk for cardiac adverse events increases with the combined therapy. We have many unanswered questions.

  1. Dietary nitrates, nitrites, and cardiovascular disease.

    PubMed

    Hord, Norman G

    2011-12-01

    Dietary nitrate (NO(3)), nitrite (NO(2)), and arginine can serve as sources for production of NO(x) (a diverse group of metabolites including nitric oxide, nitrosothiols, and nitroalkenes) via ultraviolet light exposure to skin, mammalian nitrate/nitrite reductases in tissues, and nitric oxide synthase enzymes, respectively. NO(x) are responsible for the hypotensive, antiplatelet, and cytoprotective effects of dietary nitrates and nitrites. Current regulatory limits on nitrate intakes, based on concerns regarding potential risk of carcinogenicity and methemoglobinemia, are exceeded by normal daily intakes of single foods, such as soya milk and spinach, as well as by some recommended dietary patterns such as the Dietary Approaches to Stop Hypertension diet. This review includes a call for regulatory bodies to consider all available data on the beneficial physiologic roles of nitrate and nitrite in order to derive rational bases for dietary recommendations.

  2. Density Functional Theory Study of the Complexation of the Uranyl Dication with Anionic Phosphate Ligands with and without Water Molecules

    SciTech Connect

    Jackson, Virgil E.; Gutowski, Keith E.; Dixon, David A.

    2013-08-01

    The structures, vibrational frequencies and energetics of anhydrous and hydrated complexes of UO2 2+ with the phosphate anions H2PO4 -, HPO4 2-, and PO4 3- were predicted at the density functional theory (DFT) and MP2 molecular orbital theory levels as isolated gas phase species and in aqueous solution by using self-consistent reaction field (SCRF) calculations with different solvation models. The geometries and vibrational frequencies of the major binding modes for these complexes are compared to experiment where possible and good agreement is found. The uranyl moiety is nonlinear in many of the complexes, and the coordination number (CN) 5 in the equatorial plane is the predominant binding motif. The phosphates are found to bind in both monodentate and bidentate binding modes depending on the charge and the number of water molecules. The SCRF calculations were done with a variety of approaches, and different SCRF approaches were found to be optimal for different reaction types. The acidities of HxPO4 3-x in HxPO4 3-x(H2O)4, x = 0-3 complexes were calculated with different SCRF models and compared to experiment. Phosphate anions can displace water molecules from the first solvation shell at the uranyl exothermically. The addition of water molecules can cause the bonding of H2PO4 - and HPO4 2- to change from bidentate to monodentate exothermically while maintaining CN 5. The addition of water can generate monodentate structures capable of cross-linking to other uranyl phosphates to form the types of structures found in the solid state. [UO2(HPO4)(H2O)3] is predicted to be a strong base in the gas phase and in aqueous solution. It is predicted to be a much weaker acid than H3PO4 in the gas phase and in solution.

  3. Efficient syntheses of climate relevant isoprene nitrates and (1R,5S)-(-)-myrtenol nitrate.

    PubMed

    Bew, Sean P; Hiatt-Gipson, Glyn D; Mills, Graham P; Reeves, Claire E

    2016-01-01

    Here we report the chemoselective synthesis of several important, climate relevant isoprene nitrates using silver nitrate to mediate a 'halide for nitrate' substitution. Employing readily available starting materials, reagents and Horner-Wadsworth-Emmons chemistry the synthesis of easily separable, synthetically versatile 'key building blocks' (E)- and (Z)-3-methyl-4-chlorobut-2-en-1-ol as well as (E)- and (Z)-1-((2-methyl-4-bromobut-2-enyloxy)methyl)-4-methoxybenzene has been achieved using cheap, 'off the shelf' materials. Exploiting their reactivity we have studied their ability to undergo an 'allylic halide for allylic nitrate' substitution reaction which we demonstrate generates (E)- and (Z)-3-methyl-4-hydroxybut-2-enyl nitrate, and (E)- and (Z)-2-methyl-4-hydroxybut-2-enyl nitrates ('isoprene nitrates') in 66-80% overall yields. Using NOESY experiments the elucidation of the carbon-carbon double bond configuration within the purified isoprene nitrates has been established. Further exemplifying our 'halide for nitrate' substitution chemistry we outline the straightforward transformation of (1R,2S)-(-)-myrtenol bromide into the previously unknown monoterpene nitrate (1R,2S)-(-)-myrtenol nitrate. PMID:27340495

  4. Efficient syntheses of climate relevant isoprene nitrates and (1R,5S)-(-)-myrtenol nitrate.

    PubMed

    Bew, Sean P; Hiatt-Gipson, Glyn D; Mills, Graham P; Reeves, Claire E

    2016-01-01

    Here we report the chemoselective synthesis of several important, climate relevant isoprene nitrates using silver nitrate to mediate a 'halide for nitrate' substitution. Employing readily available starting materials, reagents and Horner-Wadsworth-Emmons chemistry the synthesis of easily separable, synthetically versatile 'key building blocks' (E)- and (Z)-3-methyl-4-chlorobut-2-en-1-ol as well as (E)- and (Z)-1-((2-methyl-4-bromobut-2-enyloxy)methyl)-4-methoxybenzene has been achieved using cheap, 'off the shelf' materials. Exploiting their reactivity we have studied their ability to undergo an 'allylic halide for allylic nitrate' substitution reaction which we demonstrate generates (E)- and (Z)-3-methyl-4-hydroxybut-2-enyl nitrate, and (E)- and (Z)-2-methyl-4-hydroxybut-2-enyl nitrates ('isoprene nitrates') in 66-80% overall yields. Using NOESY experiments the elucidation of the carbon-carbon double bond configuration within the purified isoprene nitrates has been established. Further exemplifying our 'halide for nitrate' substitution chemistry we outline the straightforward transformation of (1R,2S)-(-)-myrtenol bromide into the previously unknown monoterpene nitrate (1R,2S)-(-)-myrtenol nitrate.

  5. 70. INTERIOR VIEW OF AMMONIUM NITRATE HOUSE, LOOKING AT AMMONIUM ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    70. INTERIOR VIEW OF AMMONIUM NITRATE HOUSE, LOOKING AT AMMONIUM NITRATE IN STORAGE. APRIL 18, 1919. - United States Nitrate Plant No. 2, Reservation Road, Muscle Shoals, Muscle Shoals, Colbert County, AL

  6. Nitrate Transport, Sensing, and Responses in Plants.

    PubMed

    O'Brien, José A; Vega, Andrea; Bouguyon, Eléonore; Krouk, Gabriel; Gojon, Alain; Coruzzi, Gloria; Gutiérrez, Rodrigo A

    2016-06-01

    Nitrogen (N) is an essential macronutrient that affects plant growth and development. N is an important component of chlorophyll, amino acids, nucleic acids, and secondary metabolites. Nitrate is one of the most abundant N sources in the soil. Because nitrate and other N nutrients are often limiting, plants have developed sophisticated mechanisms to ensure adequate supply of nutrients in a variable environment. Nitrate is absorbed in the root and mobilized to other organs by nitrate transporters. Nitrate sensing activates signaling pathways that impinge upon molecular, metabolic, physiological, and developmental responses locally and at the whole plant level. With the advent of genomics technologies and genetic tools, important advances in our understanding of nitrate and other N nutrient responses have been achieved in the past decade. Furthermore, techniques that take advantage of natural polymorphisms present in divergent individuals from a single species have been essential in uncovering new components. However, there are still gaps in our understanding of how nitrate signaling affects biological processes in plants. Moreover, we still lack an integrated view of how all the regulatory factors identified interact or crosstalk to orchestrate the myriad N responses plants typically exhibit. In this review, we provide an updated overview of mechanisms by which nitrate is sensed and transported throughout the plant. We discuss signaling components and how nitrate sensing crosstalks with hormonal pathways for developmental responses locally and globally in the plant. Understanding how nitrate impacts on plant metabolism, physiology, and growth and development in plants is key to improving crops for sustainable agriculture. PMID:27212387

  7. Nitrate Transport, Sensing, and Responses in Plants.

    PubMed

    O'Brien, José A; Vega, Andrea; Bouguyon, Eléonore; Krouk, Gabriel; Gojon, Alain; Coruzzi, Gloria; Gutiérrez, Rodrigo A

    2016-06-01

    Nitrogen (N) is an essential macronutrient that affects plant growth and development. N is an important component of chlorophyll, amino acids, nucleic acids, and secondary metabolites. Nitrate is one of the most abundant N sources in the soil. Because nitrate and other N nutrients are often limiting, plants have developed sophisticated mechanisms to ensure adequate supply of nutrients in a variable environment. Nitrate is absorbed in the root and mobilized to other organs by nitrate transporters. Nitrate sensing activates signaling pathways that impinge upon molecular, metabolic, physiological, and developmental responses locally and at the whole plant level. With the advent of genomics technologies and genetic tools, important advances in our understanding of nitrate and other N nutrient responses have been achieved in the past decade. Furthermore, techniques that take advantage of natural polymorphisms present in divergent individuals from a single species have been essential in uncovering new components. However, there are still gaps in our understanding of how nitrate signaling affects biological processes in plants. Moreover, we still lack an integrated view of how all the regulatory factors identified interact or crosstalk to orchestrate the myriad N responses plants typically exhibit. In this review, we provide an updated overview of mechanisms by which nitrate is sensed and transported throughout the plant. We discuss signaling components and how nitrate sensing crosstalks with hormonal pathways for developmental responses locally and globally in the plant. Understanding how nitrate impacts on plant metabolism, physiology, and growth and development in plants is key to improving crops for sustainable agriculture.

  8. Diffusion and Adsorption of Uranyl Carbonate Species in Nanosized Mineral Fractures

    SciTech Connect

    Kerisit, Sebastien N.; Liu, Chongxuan

    2012-02-07

    Atomistic simulations were performed to study the diffusion and adsorption of Ca{sub 2}UO{sub 2}(CO{sub 3}){sub 3} and of some of its constituent species, i.e., UO{sub 2}{sup 2+}, CO{sub 3}{sup 2-}, and UO{sub 2}CO{sub 3}, in feldspar nano-sized fractures. Feldspar is important to uranium remediation efforts at the U.S. Department of Energy Hanford site as it has been found in recent studies to host contaminants within its intragrain fractures. In addition, uranyl carbonate species are known to dominate U(VI) speciation in conditions relevant to the Hanford site. Molecular dynamics (MD) simulations showed that the presence of the feldspar surface diminishes the diffusion coefficients of all the species considered in this work and that the diffusion coefficients do not reach their bulk aqueous solution values in the center of a 2.5 nm fracture. Moreover, the MD simulations showed that the rate of decrease in the diffusion coefficients with decreasing distance from the surface is greater for larger adsorbing species. Free energy profiles of the same species adsorbing on the feldspar surface revealed a large exothermic free energy of adsorption for UO{sub 2}{sup 2+} and UO{sub 2}CO{sub 3}, which are able to adsorb to the surface with their uranium atom directly bonded to a surface hydroxyl oxygen, whereas adsorption of CO{sub 3}{sup 2-} and Ca{sub 2}UO{sub 2}(CO{sub 3}){sub 3}, which attach to the surface via hydrogen bonding from a surface hydroxyl group to a carbonate oxygen, was calculated to be either only slightly exothermic or endothermic.

  9. CsUV 3O 11, a New Uranyl Vanadate with a Layered Structure

    NASA Astrophysics Data System (ADS)

    Duribreux, I.; Dion, C.; Abraham, F.; Saadi, M.

    1999-08-01

    A new cesium uranyl vanadate CsUV3O11 has been synthesized by solid state reaction. Its crystal structure has been determined from single-crystal X-ray diffraction data. It crystallizes in the monoclinic system with space group P21/a and unit cell parameters a=11.904(2) Å, b=6.8321(6) Å, c= 12.095(2) Å, β=106.989(5)°, Z=4, and Dexp=4.89(2) g/cm3. A full-matrix least squares refinement yielded R=0.046 and Rw=0.045 for 1831 independent reflections with I>3σ(I) collected on a Nonius CAD4 diffractometer (MoKα radiation). The structure of CsUV3O11 is characterized by [UV3O11]∞ layers parallel to the (001) plane. The layers, very similar to those found in UV3O10, are built up from VO5 square pyramids sharing corners of their equatorial bases and UO8 hexagonal bipyramids, the U atoms occupying the hexagonal holes created by the VO5 array. The Cs+ ions are located between two successive layers and hold them together; the Cs+ ions and two layers constitute a neutral "sandwich" {(UV3O-11)-(Cs)2+2-(UV3O-11)}. In this unusual structure, the neutral sandwiches are stacked one above another along the [104] direction with no formal chemical bonds between the neutral sandwiches. The Cs mobilities in CsUV3O11 and Cs carnotite are compared.

  10. Effects of sulfate ligand on uranyl carbonato surface species on ferrihydrite surfaces

    USGS Publications Warehouse

    Arai, Yuji; Fuller, C.C.

    2012-01-01

    Understanding uranium (U) sorption processes in permeable reactive barriers (PRB) are critical in modeling reactive transport for evaluating PRB performance at the Fry Canyon demonstration site in Utah, USA. To gain insight into the U sequestration mechanism in the amorphous ferric oxyhydroxide (AFO)-coated gravel PRB, U(VI) sorption processes on ferrihydrite surfaces were studied in 0.01 M Na2SO4 solutions to simulate the major chemical composition of U-contaminatedgroundwater (i.e., [SO42-]~13 mM L-1) at the site. Uranyl sorption was greater at pH 7.5 than that at pH 4 in both air- and 2% pCO2-equilibrated systems. While there were negligible effects of sulfate ligands on the pH-dependent U(VI) sorption (<24 h) in both systems, X-ray absorption spectroscopy (XAS) analysis showed sulfate ligand associated U(VI) surface species at the ferrihydrite–water interface. In air-equilibrated systems, binary and mono-sulfate U(VI) ternary surface species co-existed at pH 5.43. At pH 6.55–7.83, a mixture of mono-sulfate and bis-carbonato U(VI) ternary surface species became more important. At 2% pCO2, there was no contribution of sulfate ligands on the U(VI) ternary surface species. Instead, a mixture of bis-carbonato inner-sphere (38%) and tris-carbonato outer-sphere U(VI) ternary surface species (62%) was found at pH 7.62. The study suggests that the competitive ligand (bicarbonate and sulfate) coordination on U(VI) surface species might be important in evaluating the U solid-state speciation in the AFO PRB at the study site where pCO2 fluctuates between 1 and 2 pCO2%.

  11. Scale-Dependent Rates of Uranyl Surface Complexation Reaction in Sediments

    SciTech Connect

    Liu, Chongxuan; Shang, Jianying; Kerisit, Sebastien N.; Zachara, John M.; Zhu, Weihuang

    2013-03-15

    Scale-dependency of uranyl[U(VI)] surface complexation rates was investigated in stirred flow-cell and column systems using a U(VI)-contaminated sediment from the US Department of Energy, Hanford site, WA. The experimental results were used to estimate the apparent rate of U(VI) surface complexation at the grain-scale and in porous media. Numerical simulations using molecular, pore-scale, and continuum models were performed to provide insights into and to estimate the rate constants of U(VI) surface complexation at the different scales. The results showed that the grain-scale rate constant of U(VI) surface complexation was over 3 to 10 orders of magnitude smaller, dependent on the temporal scale, than the rate constant calculated using the molecular simulations. The grain-scale rate was faster initially and slower with time, showing the temporal scale-dependency. The largest rate constant at the grain-scale decreased additional 2 orders of magnitude when the rate was scaled to the porous media in the column. The scaling effect from the grain-scale to the porous media became less important for the slower sorption sites. Pore-scale simulations revealed the importance of coupled mass transport and reactions in both intragranular and inter-granular domains, which caused both spatial and temporal dependence of U(VI) surface complexation rates in the sediment. Pore-scale simulations also revealed a new rate-limiting mechanism in the intragranular porous domains that the rate of coupled diffusion and surface complexation reaction was slower than either process alone. The results provided important implications for developing models to scale geochemical/biogeochemical reactions.

  12. Platinum blue as an alternative to uranyl acetate for staining in transmission electron microscopy.

    PubMed

    Inaga, Sumire; Katsumoto, Tetsuo; Tanaka, Keiichi; Kameie, Toshio; Nakane, Hironobu; Naguro, Tomonori

    2007-04-01

    This paper introduces an aqueous solution of platinum blue (Pt-blue) as an alternative to uranyl acetate (UA) for staining in transmission electron microscopy (TEM). Pt-blue was prepared from a reaction of cis-dichlorodiamine-platinum (II) (cis-platin) with thymidine. When Pt-blue was dried on a microgrid and observed by TEM it showed a uniform appearance with tiny particles less than 1 nm in diameter. The effect of Pt-blue as an electron stain was then examined not only for positive staining of conventional ultrathin resin sections and counterstaining of post-embedding immuno-electron microscopy but also for negative staining. In ultrathin sections of the rat liver and renal glomerulus, Pt-blue provided good contrast images, especially in double staining combined with a lead stain (Pb). Almost all cell organelles were clearly observed with high contrast in these sections. Glycogen granules in the hepatic parenchymal cells were particularly electron dense in Pt-blue stained sections compared with those treated with UA. In longitudinal and transverse sections of budding influenza A viruses, a specific arrangement of rod-like structures, which correspond to the ribonucleoprotein complexes, was clearly shown in each virion stained with Pt-blue and Pb. When post-embedding immunoelectron microscopy was performed in ultrathin sections of HeLa cells embedded in Lowicryl K4M, the localization of Ki-67 protein was sufficiently detected even after Pt-blue and Pb staining. The present study also revealed that Pt-blue could be used for the negative staining of E. coli, allowing the visualization of a flagellum. These findings indicate that Pt-blue is a useful, safe, and easily obtainable electron stain that is an alternative to UA for TEM preparations. PMID:17558143

  13. Syntheses and structures of a series of uranyl phosphonates and sulfonates: an insight into their correlations and discrepancies.

    PubMed

    Yang, Weiting; Tian, Tao; Wu, Hong-Yue; Pan, Qing-Jiang; Dang, Song; Sun, Zhong-Ming

    2013-03-01

    Six uranyl phosphonates and sulfonates have been hydrothermally synthesized, namely, (H2tib)[(UO2)3(PO3C6H5)4]·2H2O (UPhP-1), Zn(pi)2(UO2)(PO3C6H5)2 (UPhP-2), Zn(dib)(UO2)(PO3C6H5)2·2H2O (UPhP-3), (HTEA)[(UO2)(5-SP)] (USP-1), (Hdib)2[(UO2)2(OH)(O)(5-SP)] (USP-2), and Zn(phen)3(UO2)2(3-SP)2 (USP-3) (tib = 1,3,5-tri(1H-imidazol-1-yl)benzene, pi = 1-phenyl-1H-imidazole, dib = 1,4-di(1H-imidazol-1-yl)benzene, TEA = triethylamine, phen = 1,10-phenanthroline, 5-SP = 5-sulfoisophthalic acid, and 3-SP = 3-sulfoisophthalic acid). UPhP-1 has been determined to be a layered structure constructed by UO7 pentagonal bipyramids, UO6 octahedra, and phenylphosphonates. Protonated tib plays a role in balancing the negative charge and holding its structure together. UPhP-2 is made up of UO6 octahedra, ZnO2N2 tetrahedra and PO3C tetrahedra in phenylphosphonates, forming a 1D assembly, which is stabilized by chelate phen ligand. Further connection of such chainlike structure via dib yields a 2D layered architecture of UPhP-3. Although sulfonate group possesses similar tetrahedral structure as the phosphonate group, a unidentated coordination mode is only found in this work. UO7 pentagonal bipyramids are linked by 5-SP to form the layered assembly of USP-1. USP-2 also consists of the same sulfonate ligand, but features tetranulear uranyl clusters. Similarly, protonated TEA and dib molecules enable stabilization of their structures, respectively. Formed by dinuclear uranyl cluster and 3-SP ligand, USP-3 appears as a 1D arrangement, in which Zn(phen)3 acts as the counterion to compensate the negative charge. All of these compounds have been characterized by IR and photoluminescent spectroscopy. Their characteristic emissions have been attributed as transition properties of uranyl cations.

  14. Interaction between chitosan and uranyl ions. Role of physical and physicochemical parameters on the kinetics of sorption

    SciTech Connect

    Piron, E. |; Accominotti, M.; Domard, A.

    1997-03-19

    This work corresponds to the first part of our studies on the interactions between chitosan particles dispersed in water and uranyl ions. The measurements were obtained by ICP, and we considered the role of various physical and physicochemical parameters related to chitosan. We showed that the crystallinity, the particle dimensions, and the swelling in water of chitosan are parameters which are connected together and govern the kinetic laws of metal diffusion and sorption. The molecular mobility of the polymer chains is then essential parameter. 31 refs., 5 figs., 3 tabs.

  15. Designing the ideal uranyl ligand: a sterically induced speciation change in complexes with thiophene-bridged bis(3-hydroxy-n-methylpyridin-2-one).

    PubMed

    Szigethy, Géza; Raymond, Kenneth N

    2009-12-21

    Structural characterization of a mononuclear uranyl complex with a tetradentate, thiophene-linked bis(3-hydroxy-N-methylpyridin-2-one) ligand reveals the most planar coordination geometry yet observed with this ligand class. The introduction of ethylsulfanyl groups onto the thiophene linker disrupts this planar, conjugated ligand arrangement, resulting in the formation of dimeric (UO(2))(2)L(2) species in which each ligand spans two uranyl centers. Relative energy calculations reveal that this tendency toward dimer formation is the result of steric interference between ethylsulfanyl substitutents and linking amides. PMID:19928845

  16. Designing the Ideal Uranyl Ligand: a Sterically-Induced Speciation Change in Complexes with Thiophene-Bridged Bis(3-hydroxy-N-methylpyridin-2-one)

    SciTech Connect

    Szigethy, Geza; Raymond, Kenneth N.

    2009-09-11

    Structural characterization of a mononuclear uranyl complex with a tetradentate, thiophene-linked bis(3-hydroxy-N-methylpyridin-2-one) ligand reveals the most planar coordination geometry yet observed with this ligand class. The introduction of ethylsulfanyl groups onto the thiophene linker disrupts this planar, conjugated ligand arrangement, resulting in the formation of dimeric (UO{sub 2}){sub 2}L{sub 2} species in which each ligand spans two uranyl centers. Relative energy calculations reveal that this tendency toward dimer formation is the result of steric interference between ethylsulfanyl substituents and linking amides.

  17. Modeling nitrate removal in a denitrification bed.

    PubMed

    Ghane, Ehsan; Fausey, Norman R; Brown, Larry C

    2015-03-15

    Denitrification beds are promoted to reduce nitrate load in agricultural subsurface drainage water to alleviate the adverse environmental effects associated with nitrate pollution of surface water. In this system, drainage water flows through a trench filled with a carbon media where nitrate is transformed into nitrogen gas under anaerobic conditions. The main objectives of this study were to model a denitrification bed treating drainage water and evaluate its adverse greenhouse gas emissions. Field experiments were conducted at an existing denitrification bed. Evaluations showed very low greenhouse gas emissions (mean N2O emission of 0.12 μg N m(-2) min(-1)) from the denitrification bed surface. Field experiments indicated that nitrate removal rate was described by Michaelis-Menten kinetics with the Michaelis-Menten constant of 7.2 mg N L(-1). We developed a novel denitrification bed model based on the governing equations for water flow and nitrate removal kinetics. The model evaluation statistics showed satisfactory prediction of bed outflow nitrate concentration during subsurface drainage flow. The model can be used to design denitrification beds with efficient nitrate removal which in turn leads to enhanced drainage water quality. PMID:25638338

  18. Synthesis of Nitrate Reductase in Chlorella

    PubMed Central

    Funkhouser, Edward A.; Shen, Teh-Chien; Ackermann, Renate

    1980-01-01

    Synthesis of nitrate reductase (EC 1.6.6.1) in Chlorella vulgaris was studied under inducing conditions, i.e. with cells grown on ammonia and then transferred to nitrate medium. Cycloheximide (but not chloramphenicol) completely inhibited synthesis of the enzyme, but only if it was added at the start (i.e. at the time of nitrate addition) of the induction period. Cycloheximide inhibition became less effective as induction by nitrate proceeded. Enzyme from small quantities of culture (1 to 3 milliliters of packed cells) was purified to homogeneity with the aid of blue dextran-Sepharose chromatography. Incorporation of radioactivity from labeled arginine into nitrate reductase was measured in the presence and absence of cycloheximide. Conditions were found under which the inhibitor completely blocked the incorporation of labeled amino acid, but only slightly decreased the increase in nitrate reductase activity. The results indicate that synthesis of nitrate reductase from amino acids proceeds by way of a protein precursor which is inactive enzymically. PMID:16661310

  19. Microbial Uranium Immobilization Independent of Nitrate Reduction

    SciTech Connect

    Madden, Andrew; Smith, April; Balkwill, Dr. David; Fagan, Lisa Anne; Phelps, Tommy Joe

    2007-01-01

    At many uranium processing and handling facilities, including sites in the U.S. Department of Energy (DOE) complex, high levels of nitrate are present as co-contamination with uranium in groundwater. The daunting prospect of complete nitrate removal prior to the reduction of uranium provides a strong incentive to explore bioremediation strategies that allow for uranium bioreduction and stabilization in the presence of nitrate. Typical in-situ strategies involving the stimulation of metal-reducing bacteria are hindered by low pH environments at this study site and require that the persistent nitrate must first and continuously be removed or transformed prior to uranium being a preferred electron acceptor. This project investigates the possibility of stimulating nitrate-indifferent, pH-tolerant microorganisms to achieve bioreduction of U(VI) despite nitrate persistence. Successful enrichments from U-contaminated sediments demonstrated nearly complete reduction of uranium with very little loss of nitrate from pH 4.9-5.6 using methanol or glycerol as a carbon source. Higher pH enrichments also demonstrated similar U reduction capacity with 5-30% nitrate loss within one week. Bacterial 16S rRNA genes were amplified from uranium-reducing enrichments (pH 5.7-6.7) and sequenced. Phylogenetic analyses classified the clone sequences into four distinct clusters. Data from sequencing and T-RFLP profiles indicated that the majority of the microorganisms stimulated by these enrichment conditions consisted of low G+C Gram-positive bacteria most closely related to Clostridium and Clostridium-like organisms. This research demonstrates that the stimulation of a natural microbial community to immobilize U through bioreduction is possible without the removal of nitrate.

  20. Measurement and Chemistry of Atmospheric Organic Nitrates

    NASA Astrophysics Data System (ADS)

    Buhr, Martin Patrick

    1990-01-01

    Organic nitrates are important reservoir species for NO_{rm x} (NO + NO_2) in the atmosphere. Typically formed in and around urban areas, the organic nitrates sequester NO_{rm x} and allow it to be transported to rural and remote regions, wherein it may be released into the atmosphere and participate in catalytic cycles leading to the formation of ozone. The research described in this work focusses on two problems related to our understanding of the atmospheric chemistry of the organic nitrates, (1) measuring the organic nitrates contributions to total reactive nitrogen (NO_ {rm y}) in the atmosphere, and (2) determining the conditions under which the organic nitrates release NO_{rm x} into the atmosphere and thereby participate in ozone formation. The work performed included development of measurement methods for the organic nitrates, ambient measurements of several organic nitrates made under a variety of conditions, and data interpretation using a combination of bivariate and multivariate analysis. The instrument development that was performed centered around incorporation of capillary column technology in a gas chromatographic method. Use of a capillary column resulted in improved chromatographic resolution and instrument sensitivity. In addition to the work on the chromatographic separation of the organic nitrates, some work was done regarding the sensitivity of the electron capture detector (ECD) as a function of electrical mode of operation. Ambient measurements of several of the organic nitrates were made during three field experiments in conjunction with NOAA's Aeronomy laboratory, including PAN rm CH_3C(O)O_2NO_2), PPN rm (C_2H_5C(O)O_2NO _2), and the C_1-C _5 alkyl nitrates (RONO_2 ). The measurements were made in conjunction with a wide variety of other chemical and physical parameters. Data interpretation was performed using bivariate analysis in order to understand the diurnal variation of the concentrations of the organic nitrates and their

  1. Photodegradation of Paracetamol in Nitrate Solution

    SciTech Connect

    Meng Cui; Qu Ruijuan; Liang Jinyan; Yang Xi

    2010-11-24

    The photodegradation of paracetamol in nitrate solution under simulated solar irradiation has been investigated. The degradation rates were compared by varying environmental parameters including concentrations of nitrate ion, humic substance and pH values. The quantifications of paracetamol were conducted by HPLC method. The results demonstrate that the photodegradation of paracetamol followed first-order kinetics. The photoproducts and intermediates of paracetamol in the presence of nitrate ions were identified by extensive GC-MS method. The photodegradation pathways involving. OH radicals as reactive species were proposed.

  2. Characterizing the interaction between uranyl ion and fulvic acid using regional integration analysis (RIA) and fluorescence quenching.

    PubMed

    Zhu, Bingqi; Ryan, David K

    2016-03-01

    The development of chemometric methods has substantially improved the quantitative usefulness of the fluorescence excitation-emission matrix (EEM) in the analysis of dissolved organic matter (DOM). In this study, Regional Integration Analysis (RIA) was used to quantitatively interpret EEMs and assess fluorescence quenching behavior in order to study the binding between uranyl ion and fulvic acid. Three fulvic acids including soil fulvic acid (SFA), Oyster River fulvic acid (ORFA) and Suwannee River fulvic acid (SRFA) were used and investigated by the spectroscopic techniques. The EEM spectra obtained were divided into five regions according to fluorescence structural features and two distinct peaks were observed in region III and region V. Fluorescence quenching analysis was conducted for these two regions with the stability constants, ligand concentrations and residual fluorescence values calculated using the Ryan-Weber model. Results indicated a relatively strong binding ability between uranyl ion and fulvic acid samples at low pH (log K value varies from 4.11 to 4.67 at pH 3.50). Fluorophores in region III showed a higher binding ability with fewer binding sites than in region V. Stability constants followed the order, SFA > ORFA > SRFA, while ligand concentrations followed the reverse order, SRFA > ORFA > SFA. A comparison between RIA and Parallel Factor Analysis (PARAFAC) data treatment methods was also performed and good agreement between these two methods (less than 4% difference in log K values) demonstrates the reliability of the RIA method in this study. PMID:26736183

  3. A family of uranyl-aromatic dicarboxylate (pht-, ipa-, tpa-) framework hybrid materials: photoluminescence, surface photovoltage and dye adsorption.

    PubMed

    Gao, Xue; Wang, Che; Shi, Zhong-Feng; Song, Jian; Bai, Feng-Ying; Wang, Ji-Xiao; Xing, Yong-Heng

    2015-07-01

    Four uranyl complexes [(UO2)(pht)H2O]·H2O (pht = phthalic acid) (1), (UO2)2(Hipa)4(H2O)2 (Hipa = isophthalic acid) (2), (UO2)(tpa)(DMF)2 (tpa = terephthalic acid) (3) and (UO2)(box)2 (box = benzoic acid) (4) were synthesized by the reaction of UO2(CH3COO)2·2H2O as the metal source and phthalic acid, isophthalic acid, terephthalic acid or benzoic acid as the ligand. They were characterized by elemental analyses, IR, UV-Vis, XRD, single crystal X-ray diffraction analysis and thermal gravimetric analysis. The structural analysis reveals that complex 1 exhibits a one-dimensional chain structure constructed by the building unit [(UO2)2(pht)4(H2O)2] and further extends the chain into a 2D supramolecular architecture by hydrogen bonding interactions. Complex 2 is a discrete [(UO2)2(Hipa)4(H2O)2] structure, and by the hydrogen bonding interaction, forms a 3D supramolecular structure. In complexes 3 and 4, adjacent uranyl polyhedra form a 1D chain through bridging terephthalic acid and benzoic acid, respectively. In order to extend their functional properties, their photoluminescence, surface photovoltage and dye adsorption properties have been studied. PMID:26038888

  4. Uranyl-sorption properties of amorphous and crystalline TiO₂/ZrO₂ millimeter-sized hierarchically porous beads.

    PubMed

    Chee Kimling, Maryline; Scales, Nicholas; Hanley, Tracey L; Caruso, Rachel A

    2012-07-17

    Hierarchically porous TiO(2)/ZrO(2) millimeter-sized beads were synthesized using a sol-gel templating technique, and investigated for suitability as radionuclide sorbents using uranyl as a radionuclide-representative probe. The bead properties were varied by altering either composition (22, 36, and 82 wt % Zr in the Ti/Zr composite) or calcination temperature (500 or 700 °C). Uranyl adsorption was higher for the crystalline beads (surface area: 52-59 m(2) g(-1)) than the amorphous beads (surface area: 95-247 m(2) g(-1)), reaching a maximum of 0.170 mmol g(-1) for the 22 wt % Zr sample. This was attributed to the higher surface hydroxyl density (OH nm(-2)), presence of limited microporosity, and larger mesopores in the crystalline beads. Mass transport properties of the crystalline beads were not compromised by the large bead diameter: sorption rates comparable to those reported for powders were achieved and rates were higher than exclusively mesoporous reported systems, thereby highlighting the importance of pore hierarchy in designing materials with improved kinetics. Chemical stability of the sorbent, an important property for processes involving corrosive effluents (e.g., radioactive waste), was also assessed. Crystalline beads displayed superior resistance against matrix leaching in HNO(3). Stability varied with composition: the 22 wt % Zr sample demonstrated the highest stability. PMID:22738810

  5. Effects of a low-radiotoxicity uranium salt (uranyl acetate) on biochemical and hematological parameters of the catfish, Clarias gariepinus

    NASA Astrophysics Data System (ADS)

    Al-Ghanim, Khalid A.; Ahmad, Zubair; Al-Kahem Al-Balawi, Hmoud F.; Al-Misned, Fahad; Maboob, Shahid; Suliman, El-Amin M.

    2016-01-01

    Specimens of Clarias gariepinus were treated with lethal (70, 75, 80, 85, 90, and 95 mg/L) and sub-lethal concentrations (8, 12 and 16 mg/L) of uranyl acetate, a low-radiotoxicity uranium salt. The LC 50 value was registered as 81.45 mg/L. The protein and glycogen concentrations in liver and muscles were decreased in the fish exposed to sub-lethal concentrations. The red blood cell (RBC) and white blood cell (WBC) counts, haemoglobin (Hb) concentration and haematocrit (Hct) values were decreased. Different blood indices like mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin concentration (MCHC) were negatively affected. Level of plasma glucose was elevated whereas protein was decreased. The level of calcium concentration (Ca) was declined in the blood of exposed fish whereas magnesium (Mg) remains unchanged. The activity level of glutamic-oxaloacetic transaminase (GOT) and glutamic-pyruvic transaminase (GPT) was elevated in exposed fish. These effects were more pronounced in the last period of exposure and in higher concentrations. Results of the present study indicate that uranyl acetate has adverse effects on Clarias gariepinus and causes changes in the biochemical and hematological parameters of the fish.

  6. The radiation induced chemistry of uranyl cation in aqueous carbonate –bicarbonate solutions as followed by NMR spectroscopy

    SciTech Connect

    McNamara, Bruce K.; Snow, Lanee A.; Soderquist, Chuck Z.; Sinkov, Sergei I.; Cho, Herman M.; Friese, Judah I.

    2006-05-01

    Alpha radiation induced formation of hydrogen peroxide in carbonate ?bicarbonate media was followed by 13C NMR using dissolved [233UO2(13CO3)3]4- as the alpha source (Dalpha= 12.1 Gy/hr). Between the pH region between 5.9 and 11.6 hydrogen peroxide causes a varied speciation of the uranyl carbonates that is a function of the uranium, carbonate and the hydrogen peroxide concentrations. It is shown that the speciation of the peroxy carbonates (or other species) formed in solution by titration with hydrogen peroxide are common to those formed by hydrogen peroxide generated by radiolysis. The radiolysis experiment was carried out above pH = 9.96 to minimize the loss of 13CO2 over a 2800 hr period. Radiolytic generation of hydrogen peroxide was followed by formation of a uranyl peroxy carbonate complex and complex formation accelerated for about 1200 hours. Complex formation was observed to terminate at a concentration between 1x10-4 and 5x10-4 M. It is assumed that either a steady state H2O2 production rate was established in solution or that some limiting feature of the experiment was responsible for slowing the yield of product.

  7. Crystal chemistry and application development of uranyl extended structure and nanoscale materials and actinyl ion-substituted mineral phases

    NASA Astrophysics Data System (ADS)

    Wylie, Ernest M.

    The worldwide use of nuclear energy presents both significant advantages and challenges for society. Actinide research seeks to address these challenges and drive advancement in the fields of nuclear science and engineering. Here, key aspects of the fuel cycle are examined from both a fundamental and an applications-based perspective. Hydrothermal, ionothermal, room-temperature evaporation, and liquid diffusion synthesis techniques and single-crystal X-ray diffraction were used to study the structures of 18 uranyl compounds and six actinyl-doped mineral phases. These compounds represent a diverse group ranging from unique molecular clusters to novel and known extended structures isolated from aqueous and ionic liquid media. Ultrafiltration techniques were utilized to separate uranyl peroxide nanoclusters from complex aqueous solutions. Inductively coupled plasma optical emission spectroscopy and mass spectrometry were used to quantify elemental distributions in the feed and permeate solutions while Raman spectroscopy, small-angle X-ray scattering, and electrospray ionization mass spectrometry were used to define the characteristics of the cluster species across a range different solution conditions.

  8. Structure and dynamics of the uranyl tricarbonate complex in aqueous solution: insights from quantum mechanical charge field molecular dynamics.

    PubMed

    Tirler, Andreas O; Hofer, Thomas S

    2014-11-13

    This investigation presents the characterization of structural and dynamical properties of uranyl tricarbonate in aqueous solution employing an extended hybrid quantum mechanical/molecular mechanical (QM/MM) approach. It is shown that the inclusion of explicit solvent molecules in the quantum chemical treatment is essential to mimic the complex interaction occurring in an aqueous environment. Thus, in contrast to gas phase cluster calculations on a quantum chemical level proposing a 6-fold coordination of the three carbonates, the QMCF MD simulation proposes a 5-fold coordination. An extensive comparison of the simulation results to structural and dynamical data available in the literature was found to be in excellent agreement. Furthermore, this work is the first theoretical study on a quantum chemical level of theory able to observe the conversion of carbonate (CO₃²⁻) to bicarbonate (HCO₃⁻) in the equatorial coordination sphere of the uranyl ion. From a comparison of the free energy ΔG values for the unprotonated educt [UO₂(CO₃)₃]⁴⁻ and the protonated [UO₂(CO₃)₂(HCO₃)]³⁻, it could be concluded that the reaction equilibrium is strongly shifted toward the product state confirming the benignity for the observed protonation reaction. Structural properties and the three-dimensional arrangement of carbonate ligands were analyzed via pair-, three-body, and angular distributions, the dynamical properties were evaluated by hydrogen-bond correlation functions and vibrational power spectra.

  9. Simultaneous reduction of arsenic(V) and uranium(VI) by mackinawite: role of uranyl arsenate precipitate formation.

    PubMed

    Troyer, Lyndsay D; Tang, Yuanzhi; Borch, Thomas

    2014-12-16

    Uranium (U) and arsenic (As) often occur together naturally and, as a result, can be co-contaminants at sites of uranium mining and processing, yet few studies have examined the simultaneous redox dynamics of U and As. This study examines the influence of arsenate (As(V)) on the reduction of uranyl (U(VI)) by the redox-active mineral mackinawite (FeS). As(V) was added to systems containing 47 or 470 μM U(VI) at concentrations ranging from 0 to 640 μM. In the absence of As(V), U was completely removed from solution and fully reduced to nano-uraninite (nano-UO2). While the addition of As(V) did not reduce U uptake, at As(V) concentrations above 320 μM, the reduction of U(VI) was limited due to the formation of a trögerite-like uranyl arsenate precipitate. The presence of U also significantly inhibited As(V) reduction. While less U(VI) reduction to nano-UO2 may take place in systems with high As(V) concentrations, formation of trögerite-like mineral phases may be an acceptable reclamation end point due to their high stability under oxic conditions. PMID:25383895

  10. The neurology of folic acid deficiency.

    PubMed

    Reynolds, E H

    2014-01-01

    The metabolism of folic acid and the metabolism of vitamin B12 are intimately linked such that deficiency of either vitamin leads to an identical megaloblastic anemia. The neurologic manifestations of folate deficiency overlap with those of vitamin B12 deficiency and include cognitive impairment, dementia, depression, and, less commonly, peripheral neuropathy and subacute combined degeneration of the spinal cord. In both deficiency states there is often dissociation between the neuropsychiatric and the hematologic complications. There is a similar overlap and dissociation between neurologic and hematologic manifestations of inborn errors of folate and vitamin B12 metabolism. Low folate and raised homocysteine levels are risk factors for dementia, including Alzheimer's disease, and depression. Even when folate deficiency is secondary to psychiatric illness due to apathy or poor diet it may eventually aggravate the underlying disorder in a vicious circle effect. Clinical responses to treatment with folates are usually slow over weeks and months, probably due to the efficient blood-brain barrier mechanism for the vitamin, perhaps in turn related to the experimentally demonstrated excitatory properties of folate derivatives. The inappropriate administration of folic acid in the presence of vitamin B12 deficiency may lead to both neurologic and, later, hematologic relapse. Impaired maternal folate intake and status increases the risk of neural tube defects. Periconceptual prophylactic administration of the vitamin reduces, but does not eliminate the risk of neural tube defects even in the absence of folate deficiency. Folates and vitamin B12 have fundamental roles in central nervous system function at all ages, especially in purine, thymidine, neucleotide, and DNA synthesis, genomic and nongenomic methylation and, therefore, in tissue growth, differentiation and repair. There is interest in the potential role of both vitamins in the prevention of disorders of central nervous system development, mood, dementia, including Alzheimer's disease, and aging. PMID:24365361

  11. Phase diagram of ammonium nitrate

    SciTech Connect

    Dunuwille, Mihindra; Yoo, Choong-Shik

    2013-12-07

    Ammonium Nitrate (AN) is a fertilizer, yet becomes an explosive upon a small addition of chemical impurities. The origin of enhanced chemical sensitivity in impure AN (or AN mixtures) is not well understood, posing significant safety issues in using AN even today. To remedy the situation, we have carried out an extensive study to investigate the phase stability of AN and its mixtures with hexane (ANFO–AN mixed with fuel oil) and Aluminum (Ammonal) at high pressures and temperatures, using diamond anvil cells (DAC) and micro-Raman spectroscopy. The results indicate that pure AN decomposes to N{sub 2}, N{sub 2}O, and H{sub 2}O at the onset of the melt, whereas the mixtures, ANFO and Ammonal, decompose at substantially lower temperatures. The present results also confirm the recently proposed phase IV-IV{sup ′} transition above 17 GPa and provide new constraints for the melting and phase diagram of AN to 40 GPa and 400°C.

  12. Peroxyacetyl nitrate in eastern Scotland.

    PubMed

    McFadyen, G G; Cape, J N

    2005-01-20

    Peroxyacetyl nitrate (PAN) concentrations in air were sampled hourly from 1994 to 1998 at a rural site 15 km south-west of Edinburgh, in eastern Scotland. Annual average concentrations were between 0.1 and 0.15 nl l(-1), with episodes up to 3 nl l(-1) in long-range transported polluted air. PAN concentrations were approximately log-normally distributed. The concentrations measured are the result of a balance between photochemical production rates and removal by thermal decomposition and dry deposition. In general, there was a poor correlation between PAN and ozone concentrations at this rural site except during episodes of photochemical pollution, when the PAN/O(3) volume ratio exceeded 0.01. The PAN/NO(x) volume ratio had a median value of 0.015 but ranged up to 0.25. There was a pronounced seasonal maximum in PAN concentrations in late spring, and a strong diurnal cycle only in April-June, with a maximum at 1700 h. Individual episodes, with concentrations up to 3 nl l(-1), could be traced over distances of ca. 1000 km, with rapid changes in concentration as the prevailing winds advected polluted air masses across the site.

  13. New methods of nitrate removal from water.

    PubMed

    Shrimali, M; Singh, K P

    2001-01-01

    Nitrate contamination in groundwater resources originates mainly from the excessive use of fertilisers and uncontrolled land discharges of treated wastewater. This can cause potential health hazards to infants and pregnant women, thus limiting the direct use of the groundwater resources for the human consumption in several parts of the world, including India. The conventional processes used to eliminate nitrate from water are ion exchange, reverse osmosis and electro-dialysis. The utility of these processes has been limited due to their expensive operation and subsequent disposal problem of the generated nitrate waste brine. This paper presents a comprehensive account of the methods/techniques used for the removal of nitrate ion from water during the last 10 years with special reference to the biological denitrification and fate of the metals in decontamination processes.

  14. Qualitative Determination of Nitrate with Triphenylbenzylphosphonium Chloride.

    ERIC Educational Resources Information Center

    Berry, Donna A.; Cole, Jerry J.

    1984-01-01

    Discusses two procedures for the identification of nitrate, the standard test ("Brown Ring" test) and a new procedure using triphenylbenzylphosphonium chloride (TPBPC). Effectiveness of both procedures is compared, with the TPBPC test proving to be more sensitive and accurate. (JM)

  15. Reactive Transport of the Uranyl Ion in Soils, Sediments, and Groundwater Systems

    SciTech Connect

    Zachara, John M.; Ilton, Eugene S.; Liu, Chongxuan

    2013-05-16

    Uranium is a ubiquitous trace component in rocks ranging from 1.2 to 1.3 µg g-1 in sedimentary rocks, 2.2 to 15 µg g-1 in granites, and 20 to 120 µg g-1 in phosphates (Langmuir, 1997; Plant et al., 1999). Uranium (U) is released to natural waters in dilute concentrations (generally < 10-7 mole L-1) from the weathering of these sources, with water concentrations in uraniferous geologic terrains, such as the southwestern U.S. (USGS, 2011), being higher (~ 10-6.5 mol L-1). Elevated water-borne concentrations are associated with the weathering of natural ore bodies [~10-6 mol L-1; e.g, (Payne and Airey, 2006)], the extraction and mining of U for armaments (Jiang and Aschner, 2009; WHO, 2001) and nuclear fuels [10-6 to 10-3 mol L-1; (Abdelouas et al., 1999)], and the disposal of waste solids and liquids from nuclear fuels reprocessing and arms production [~ 10-6 to 10-2 mol L-1; e.g., (Wan et al., 2009; Zachara et al., 2007)]. The form of U present in natural waters at high concentration is generally the uranyl ion [e.g., UO22+] which is quite soluble. Groundwater in many parts of the world contains dissolved U originating from natural and anthropogenic sources (ATSDR, 2011; EFSA, 2009). Low levels of dissolved U in drinking water are considered a health concern, causing renal and other effects (Kurttio et al., 2002; Kurttio et al., 2005; Limson Zamora et al., 1998; Nriagu et al., 2012; Raymond-Whish et al., 2007; Selden et al., 2009). The U.S. Environmental Protection Agency has established a regulatory drinking water standard of 30 µg L-1 (1.26 x 10-7 mol L-1) or 30 pCi L-1, whichever is exceeded first. The World Health Organization has recommended an even lower drinking water standard of 15 µg L-1 [6.3 x 10-8 mol L-1; (WHO, 2005)]. Human exposure to U through drinking water is expected to rise as world-wide reliance on groundwater sources increase (ESS, 2010).

  16. First three-dimensional actinide polyrotaxane framework mediated by windmill-like six-connected oligomeric uranyl: dual roles of the pseudorotaxane precursor.

    PubMed

    Mei, Lei; Xie, Zhen-Ni; Hu, Kong-Qiu; Wang, Lin; Yuan, Li-Yong; Li, Zi-Jie; Chai, Zhi-Fang; Shi, Wei-Qun

    2016-09-14

    The first 3D actinide polyrotaxane framework (named IHEP-URCP-2) has been obtained based on windmill-like six-connected high-nuclear oligomeric uranyl nodes under hydrothermal conditions. Notably, the in situ formed pseudorotaxane ligand simultaneously plays dual roles of both a bulky pseudorotaxane linker and a supramolecular guest.

  17. Subtle Interactions and Electron Transfer between U(III) , Np(III) , or Pu(III) and Uranyl Mediated by the Oxo Group.

    PubMed

    Arnold, Polly L; Dutkiewicz, Michał S; Zegke, Markus; Walter, Olaf; Apostolidis, Christos; Hollis, Emmalina; Pécharman, Anne-Fréderique; Magnani, Nicola; Griveau, Jean-Christophe; Colineau, Eric; Caciuffo, Roberto; Zhang, Xiaobin; Schreckenbach, Georg; Love, Jason B

    2016-10-01

    A dramatic difference in the ability of the reducing An(III) center in AnCp3 (An=U, Np, Pu; Cp=C5 H5 ) to oxo-bind and reduce the uranyl(VI) dication in the complex [(UO2 )(THF)(H2 L)] (L="Pacman" Schiff-base polypyrrolic macrocycle), is found and explained. These are the first selective functionalizations of the uranyl oxo by another actinide cation. At-first contradictory electronic structural data are explained by combining theory and experiment. Complete one-electron transfer from Cp3 U forms the U(IV) -uranyl(V) compound that behaves as a U(V) -localized single molecule magnet below 4 K. The extent of reduction by the Cp3 Np group upon oxo-coordination is much less, with a Np(III) -uranyl(VI) dative bond assigned. Solution NMR and NIR spectroscopy suggest Np(IV) U(V) but single-crystal X-ray diffraction and SQUID magnetometry suggest a Np(III) -U(VI) assignment. DFT-calculated Hirshfeld charge and spin density analyses suggest half an electron has transferred, and these explain the strongly shifted NMR spectra by spin density contributions at the hydrogen nuclei. The Pu(III) -U(VI) interaction is too weak to be observed in THF solvent, in agreement with calculated predictions. PMID:27628291

  18. Subtle Interactions and Electron Transfer between U(III) , Np(III) , or Pu(III) and Uranyl Mediated by the Oxo Group.

    PubMed

    Arnold, Polly L; Dutkiewicz, Michał S; Zegke, Markus; Walter, Olaf; Apostolidis, Christos; Hollis, Emmalina; Pécharman, Anne-Fréderique; Magnani, Nicola; Griveau, Jean-Christophe; Colineau, Eric; Caciuffo, Roberto; Zhang, Xiaobin; Schreckenbach, Georg; Love, Jason B

    2016-10-01

    A dramatic difference in the ability of the reducing An(III) center in AnCp3 (An=U, Np, Pu; Cp=C5 H5 ) to oxo-bind and reduce the uranyl(VI) dication in the complex [(UO2 )(THF)(H2 L)] (L="Pacman" Schiff-base polypyrrolic macrocycle), is found and explained. These are the first selective functionalizations of the uranyl oxo by another actinide cation. At-first contradictory electronic structural data are explained by combining theory and experiment. Complete one-electron transfer from Cp3 U forms the U(IV) -uranyl(V) compound that behaves as a U(V) -localized single molecule magnet below 4 K. The extent of reduction by the Cp3 Np group upon oxo-coordination is much less, with a Np(III) -uranyl(VI) dative bond assigned. Solution NMR and NIR spectroscopy suggest Np(IV) U(V) but single-crystal X-ray diffraction and SQUID magnetometry suggest a Np(III) -U(VI) assignment. DFT-calculated Hirshfeld charge and spin density analyses suggest half an electron has transferred, and these explain the strongly shifted NMR spectra by spin density contributions at the hydrogen nuclei. The Pu(III) -U(VI) interaction is too weak to be observed in THF solvent, in agreement with calculated predictions.

  19. Synthesis of a new energetic nitrate ester

    SciTech Connect

    Chavez, David E

    2008-01-01

    Nitrate esters have been known as useful energetic materials since the discovery of nitroglycerin by Ascanio Sobrero in 1846. The development of methods to increase the safety and utility of nitroglycerin by Alfred Nobel led to the revolutionary improvement in the utility of nitroglycerin in explosive applications in the form of dynamite. Since then, many nitrate esters have been prepared and incorporated into military applications such as double-based propellants, detonators and as energetic plasticizers. Nitrate esters have also been shown to have vasodilatory effects in humans and thus have been studied and used for treatments of ailments such as angina. The mechanism of the biological response towards nitrate esters has been elucidated recently. Interestingly, many of the nitrate esters used for military purposes are liquids (ethylene glycol dinitrate, propylene glycol dinitrate, etc). Pentaerythritol tetranitrate (PETN) is one of the only solid nitrate esters, besides nitrocellulose, that is used in any application. Unfortunately, PETN melting point is above 100 {sup o}C, and thus must be pressed as a solid for detonator applications. A more practical material would be a melt-castable explosive, for potential simplification of manufacturing processes. Herein we describe the synthesis of a new energetic nitrate ester (1) that is a solid at ambient temperatures, has a melting point of 85-86 {sup o}C and has the highest density of any known nitrate ester composed only of carbon, hydrogen, nitrogen and oxygen. We also describe the chemical, thermal and sensitivity properties of 1 as well as some preliminary explosive performance data.

  20. The UK Nitrate Time Bomb (Invited)

    NASA Astrophysics Data System (ADS)

    Ward, R.; Wang, L.; Stuart, M.; Bloomfield, J.; Gooddy, D.; Lewis, M.; McKenzie, A.

    2013-12-01

    The developed world has benefitted enormously from the intensification of agriculture and the increased availability and use of synthetic fertilizers during the last century. However there has also been unintended adverse impact on the natural environment (water and ecosystems) with nitrate the most significant cause of water pollution and ecosystem damage . Many countries have introduced controls on nitrate, e.g. the European Union's Water Framework and Nitrate Directives, but despite this are continuing to see a serious decline in water quality. The purpose of our research is to investigate and quantify the importance of the unsaturated (vadose) zone pathway and groundwater in contributing to the decline. Understanding nutrient behaviour in the sub-surface environment and, in particular, the time lag between action and improvement is critical to effective management and remediation of nutrient pollution. A readily-transferable process-based model has been used to predict temporal loading of nitrate at the water table across the UK. A time-varying nitrate input function has been developed based on nitrate usage since 1925. Depth to the water table has been calculated from groundwater levels based on regional-scale observations in-filled by interpolated river base levels and vertical unsaturated zone velocities estimated from hydrogeological properties and mapping. The model has been validated using the results of more than 300 unsaturated zone nitrate profiles. Results show that for about 60% of the Chalk - the principal aquifer in the UK - peak nitrate input has yet to reach the water table and concentrations will continue to rise over the next 60 years. The implications are hugely significant especially where environmental objectives must be achieved in much shorter timescales. Current environmental and regulatory management strategies rarely take lag times into account and as a result will be poorly informed, leading to inappropriate controls and conflicts

  1. A search for nitrates in Martian meteorites

    NASA Astrophysics Data System (ADS)

    Grady, Monica M.; Wright, I. P.; Pillinger, C. T.

    1995-03-01

    Martian atmospheric nitrogen is highly enriched in N-15; nitrates formed by interaction of the atmosphere with the Martian regolith should therefore also be characterized by an elevated delta N-15 value. A search has been made for nitrates in two Martian meteorites, in order to determine the extent of possible regolith-atmosphere interaction. Shock-produced glass from the Elephant Moraine (EET) A79001 shergottite (E1,149) and a water-soluble extract from Nakhla were analyzed by Fourier transform infrared (FTIR) spectroscopy and stepped combustion-stable isotope mass spectrometry. FTIR of both meteorites had features at 1375/cm and 1630/cm, consistent with nitrates. On account of their low thermal stability, nitrates break down at temperatures below 600 C; in this temperature range, E1,149 yeilded approximately 1250 ppb nitrogen with delta N-15 -8 +/- 5%. If this nitrogen is from a nitrate, then it cannot be distinquished from terrestial salts by its isotopic composition. The water-soluble extract from Nakhla also released nitrogen at low temperatures, approximately 17 ppb with delta N-15 approximately -11 +/- 4%. Since Nakhla is an observed 'fall', this is unlikely to be a terrestial weathering product. Nitrates apparently occur in E1,149 and Nakhla, but in very low abundance, and their origin is unclear. The isotopic composition of the salts, which is within the range of that proposed for Martian magmatic volatiles, is far removed from that of nitrogen in the present-day Martian atmosphere. If the nitrates are Martian in origin, they did not form in recent times from reactions involving atmospheric gases. Rather, the nitrates could be the result of an earlier episode of atmospheric interaction with the regolith, or with implantation of magmatic volatiles introduced during degassing.

  2. Microbial uranium immobilization independent of nitrate reduction.

    PubMed

    Madden, Andrew S; Smith, April C; Balkwill, David L; Fagan, Lisa A; Phelps, Tommy J

    2007-09-01

    At many uranium processing and handling facilities, including sites in the US Department of Energy (DOE) complex, high levels of nitrate are present as co-contamination with uranium in groundwater. The daunting prospect of complete nitrate removal prior to the reduction of uranium provides a strong incentive to explore bioremediation strategies that allow for uranium bioreduction and stabilization in the presence of nitrate. Typical in situ strategies involving the stimulation of metal-reducing bacteria are hindered by low-pH environments and require that the persistent nitrate must first and continuously be removed or transformed prior to uranium being a preferred electron acceptor. This work investigated the possibility of stimulating nitrate-indifferent, pH-tolerant microorganisms to achieve bioreduction of U(VI) despite nitrate persistence. Enrichments from U-contaminated sediments demonstrated nearly complete reduction of uranium with very little loss of nitrate from pH 5.7-6.2 using methanol or glycerol as a carbon source. Bacterial 16S rRNA genes were amplified from uranium-reducing enrichments (pH 5.7-6.2) and sequenced. Phylogenetic analyses classified the clone sequences into four distinct clusters. Data from sequencing and terminal-restriction fragment length polymorphism (T-RFLP) profiles indicated that the majority of the microorganisms stimulated by these enrichment conditions consisted of low G+C Gram-positive bacteria most closely related to Clostridium and Clostridium-like organisms. This research demonstrates that the stimulation of a natural microbial community to immobilize U through bioreduction is possible without the removal of nitrate.

  3. Is beetroot juice more effective than sodium nitrate? The effects of equimolar nitrate dosages of nitrate-rich beetroot juice and sodium nitrate on oxygen consumption during exercise.

    PubMed

    Flueck, Joelle Leonie; Bogdanova, Anna; Mettler, Samuel; Perret, Claudio

    2016-04-01

    Dietary nitrate has been reported to lower oxygen consumption in moderate- and severe-intensity exercise. To date, it is unproven that sodium nitrate (NaNO3(-); NIT) and nitrate-rich beetroot juice (BR) have the same effects on oxygen consumption, blood pressure, and plasma nitrate and nitrite concentrations or not. The aim of this study was to compare the effects of different dosages of NIT and BR on oxygen consumption in male athletes. Twelve healthy, well-trained men (median [minimum; maximum]; peak oxygen consumption: 59.4 mL·min(-1)·kg(-1) [40.5; 67.0]) performed 7 trials on different days, ingesting different nitrate dosages and placebo (PLC). Dosages were 3, 6, and 12 mmol nitrate as concentrated BR or NIT dissolved in plain water. Plasma nitrate and nitrite concentrations were measured before, 3 h after ingestion, and postexercise. Participants cycled for 5 min at moderate intensity and further 8 min at severe intensity. End-exercise oxygen consumption at moderate intensity was not significantly different between the 7 trials (p = 0.08). At severe-intensity exercise, end-exercise oxygen consumption was ~4% lower in the 6-mmol BR trial compared with the 6-mmol NIT (p = 0.003) trial as well as compared with PLC (p = 0.010). Plasma nitrite and nitrate concentrations were significantly increased after the ingestion of BR and NIT with the highest concentrations in the 12-mmol trials. Plasma nitrite concentration between NIT and BR did not significantly differ in the 6-mmol (p = 0.27) and in the 12-mmol (p = 0.75) trials. In conclusion, BR might reduce oxygen consumption to a greater extent compared with NIT. PMID:26988767

  4. Preformed Nitrate in the Glacial North Atlantic

    NASA Astrophysics Data System (ADS)

    Homola, K.; Spivack, A. J.; D'Hondt, S.; Estes, E. R.; Insua, T. L.; McKinley, C. C.; Murray, R. W.; Pockalny, R. A.; Robinson, R. S.; Sauvage, J.

    2015-12-01

    Atmospheric CO2 abundances are highly correlated with global temperature variations over the past 800,000 years. Consequently, understanding the feedbacks between climate and CO2 is important for predictions of future climate. Leading hypotheses to explain this feedback invoke changes in ocean biology, circulation, chemistry, and/or gas exchange rates to trap CO2 in the deep ocean, thereby reducing the greenhouse effect of CO2 in the atmosphere. To test these hypotheses, we use sediment pore water profiles of dissolved nitrate and oxygen to reconstruct paleo-preformed nitrate concentrations at two deep-water sites in the western North Atlantic (23°N 57°W, 5557 m water depth; 30°N 58°W, 5367 m water depth). Preformed nitrate increases down-core to 22.7 μM (25.6 m core depth) at the northern site, and to 28.5 μM (27.8 m core depth) at the southern site. The large preformed nitrate gradient between these sites reveals a paleo-boundary between a southern water source high in preformed nitrate and a northern water source with lower concentrations, similar to today's ocean. However, the boundary between these water masses occurs north of where their modern counterparts meet, indicating that Antarctic Bottom Water (AABW) extended farther north during the Last Glacial Maximum (LGM). In addition, the southern source had a higher preformed nitrate concentration than today's AABW (25 μM), contradicting hypotheses that nutrient utilization was more efficient in the Southern Ocean deep-water formation regions during the LGM. Comparison to our previous Pacific data reveals that the average preformed nitrate concentration of the deep ocean was slightly higher during the LGM than today. This result implies that the CO2-climate feedback was not principally due to more efficient nitrate utilization.

  5. Nitrate inhibition of legume nodule growth and activity. II. Short term studies with high nitrate supply

    SciTech Connect

    Streeter, J.G.

    1985-02-01

    Soybean plants (Glycine max (L.) Merr) were grown in sand culture with 2 millimolar nitrate for 37 days and then supplied with 15 millimolar nitrate for 7 days. Control plants received 2 millimolar nitrate and 13 millimolar chloride and, after the 7-day treatment period, all plants were supplied with nil nitrate. The temporary treatment with high nitrate inhibited nitrogenase (acetylene reduction) activity by 80% whether or not Rhizobium japonicum bacteroids had nitrate reductase (NR) activity. The pattern of nitrite accumulation in nodules formed by NR/sup +/ rhizobia was inversely related to the decrease and recovery of nitrogenase activity. However, nitrite concentration in nodules formed by NR/sup -/ rhizobia appeared to be too low to explain the inhibition of nitrogenase. Nodules on plants treated with 15 millimolar nitrate contained higher concentrations of amino N and, especially, ureide N than control nodules and, after withdrawal of nitrate, reduced N content of treated and control nodules returned to similar levels. The accumulation of N/sub 2/ fixation products in nodules in response to high nitrate treatment was observed with three R. japonicum strains, two NR/sup +/ and one NR/sup -/.

  6. Approximate prediction of melting point of nitramines, nitrate esters, nitrate salts and nitroaliphatics energetic compounds.

    PubMed

    Keshavarz, Mohammad Hossein

    2006-12-01

    A simple new procedure is introduced to predict melting point of selected class of energetic compounds containing nitramines, nitrate esters, nitrate salts and nitroaliphatics energetic compounds. The number of nitrogen and oxygen as well as the number of nitramine group and the contribution of some specific functional groups would be needed in the new method. Energetic compounds should contain at least one of the functional groups including N-NO(2), C-ONO(2) or nonaromatic C-NO(2). Calculated melting point for 33 nitramines, nitrate esters, nitrate salt and nitroaliphatics are compared with experimental data. Predicted melting points have average deviation of 5.4% for these energetic compounds.

  7. The Arabidopsis ATNRT2.7 nitrate transporter controls nitrate content in seeds.

    PubMed

    Chopin, Franck; Orsel, Mathilde; Dorbe, Marie-France; Chardon, Fabien; Truong, Hoai-Nam; Miller, Anthony J; Krapp, Anne; Daniel-Vedele, Françoise

    2007-05-01

    In higher plants, nitrate is taken up by root cells where Arabidopsis thaliana NITRATE TRANSPORTER2.1 (ATNRT2.1) chiefly acts as the high-affinity nitrate uptake system. Nitrate taken up by the roots can then be translocated from the root to the leaves and the seeds. In this work, the function of the ATNRT2.7 gene, one of the seven members of the NRT2 family in Arabidopsis, was investigated. High expression of the gene was detected in reproductive organs and peaked in dry seeds. beta-Glucuronidase or green fluorescent protein reporter gene expression driven by the ATNRT2.7 promoter confirmed this organ specificity. We assessed the capacity of ATNRT2.7 to transport nitrate in Xenopus laevis oocytes or when it is expressed ectopically in mutant plants deficient in nitrate transport. We measured the impact of an ATNRT2.7 mutation and found no difference from the wild type during vegetative development. By contrast, seed nitrate content was affected by overexpression of ATNRT2.7 or a mutation in the gene. Finally, we showed that this nitrate transporter protein was localized to the vacuolar membrane. Our results demonstrate that ATNRT2.7 plays a specific role in nitrate accumulation in the seed.

  8. Organic nitrates and nitrate tolerance--state of the art and future developments.

    PubMed

    Daiber, Andreas; Münzel, Thomas; Gori, Tommaso

    2010-01-01

    The hemodynamic and antiischemic effects of nitroglycerin (GTN) are lost upon chronic administration due to the rapid development of nitrate tolerance. The mechanism of this phenomenon has puzzled several generations of scientists, but recent findings have led to novel hypotheses. The formation of reactive oxygen and nitrogen species in the mitochondria and the subsequent inhibition of the nitrate-bioactivating enzyme mitochondrial aldehyde dehydrogenase (ALDH-2) appear to play a central role, at least for GTN, that is, bioactivated by ALDH-2. Importantly, these findings provide the opportunity to reconcile the two "traditional" hypotheses of nitrate tolerance, that is, the one postulating a decreased bioactivation and the concurrent one suggesting a role of oxidative stress. Furthermore, recent animal and human experimental studies suggest that the organic nitrates are not a homogeneous group but demonstrate a broad diversity with regard to induction of vascular dysfunction, oxidative stress, and other side effects. In the past, attempts to avoid nitrate-induced side effects have focused on administration schedules that would allow a "nitrate-free interval"; in the future, the role of co-therapies with antioxidant compounds and of activation of endogeneous protective pathways such as the heme oxygenase 1 (HO-1) will need to be explored. However, the development of new nitrates, for example, tolerance-free aminoalkyl nitrates or combination of nitrate groups with established cardiovascular drugs like ACE inhibitors or AT(1)-receptor blockers (hybrid molecules) may be of great clinical interest.

  9. Stimulating nitrate removal processes of restored wetlands.

    PubMed

    Ballantine, Kate A; Groffman, Peter M; Lehmann, Johannes; Schneider, Rebecca L

    2014-07-01

    The environmental and health effects caused by nitrate contamination of aquatic systems are a serious problem throughout the world. A strategy proposed to address nitrate pollution is the restoration of wetlands. However, although natural wetlands often remove nitrate via high rates of denitrification, wetlands restored for water quality functions often fall below expectations. This may be in part because key drivers for denitrification, in particular soil carbon, are slow to develop in restored wetlands. We added organic soil amendments that range along a gradient of carbon lability to four newly restored wetlands in western New York to investigate the effect of carbon additions on denitrification and other processes of the nitrogen cycle. Soil carbon increased by 12.67-63.30% with the use of soil amendments (p ≤ 0.0001). Soil nitrate, the carbon to nitrogen ratio, and microbial biomass nitrogen were the most significant predictors of denitrification potential. Denitrification potential, potential net nitrogen nitrification and mineralization, and soil nitrate and ammonium, were highest in topsoil-amended plots, with increases in denitrification potential of 161.27% over control plots. While amendment with topsoil more than doubled several key nitrogen cycling processes, more research is required to determine what type and level of amendment application are most effective for stimulating removal of exogenous nitrate and meeting functional goals within an acceptable time frame. PMID:24915604

  10. Denitrification inhibition by high nitrate wastes

    SciTech Connect

    Veydovec, W.; Silverstein, J.; Cook, N.E. Jr.; Figueroa, L.A.; Hund, R.; Lehmkuhl, G.D.

    1994-12-31

    The processing of radioactive metal products at nuclear weapons plants and research labs has produced wastewaters containing high concentrations of nitrate, often greater than 50,000 mg/l N. The adaptation of activated sludge and inhibition of denitrification at high nitrate concentrations was studied using pH controlled bench-scale sequencing batch reactors (SBRs), operated with 50% of the SBR volume recycled (recycle volume = influent volume). Denitrification of 1,350 and 2,700 mg/l NO{sub 3}{sup {minus}}-N was completed after approximately 5 hours and 15 hours, respectively. No denitrification of 5,400 mg/l NO{sub 3}{sup {minus}}-N was observed. These results suggest that there is a progressive inhibition of denitrification as nitrate concentrations increase from 1,350 to 5,400 mg/l NO{sub 3}{sup {minus}}-N. In a subsequent series of experiments at an initial reactor nitrate concentration of 1,350 mg/l N, a significant accumulation of nitrate was observed, resulting once in destabilization with loss of denitrification and once in successful adaptation of the activated sludge. At a nitrate concentration of 1,350 mg/l N, the adaptation of activated sludge appears to be unstable, resulting sometimes in stable denitrification and sometimes in biomass washout.

  11. Stimulating nitrate removal processes of restored wetlands.

    PubMed

    Ballantine, Kate A; Groffman, Peter M; Lehmann, Johannes; Schneider, Rebecca L

    2014-07-01

    The environmental and health effects caused by nitrate contamination of aquatic systems are a serious problem throughout the world. A strategy proposed to address nitrate pollution is the restoration of wetlands. However, although natural wetlands often remove nitrate via high rates of denitrification, wetlands restored for water quality functions often fall below expectations. This may be in part because key drivers for denitrification, in particular soil carbon, are slow to develop in restored wetlands. We added organic soil amendments that range along a gradient of carbon lability to four newly restored wetlands in western New York to investigate the effect of carbon additions on denitrification and other processes of the nitrogen cycle. Soil carbon increased by 12.67-63.30% with the use of soil amendments (p ≤ 0.0001). Soil nitrate, the carbon to nitrogen ratio, and microbial biomass nitrogen were the most significant predictors of denitrification potential. Denitrification potential, potential net nitrogen nitrification and mineralization, and soil nitrate and ammonium, were highest in topsoil-amended plots, with increases in denitrification potential of 161.27% over control plots. While amendment with topsoil more than doubled several key nitrogen cycling processes, more research is required to determine what type and level of amendment application are most effective for stimulating removal of exogenous nitrate and meeting functional goals within an acceptable time frame.

  12. Protein tyrosine nitration in the cell cycle

    SciTech Connect

    Jia, Min; Mateoiu, Claudia; Souchelnytskyi, Serhiy

    2011-09-23

    Highlights: {yields} Enrichment of 3-nitrotyrosine containing proteins from cells synchronized in different phases of the cell cycle. {yields} Identification of 76 tyrosine nitrated proteins that change expression during the cell cycle. {yields} Nineteen identified proteins were previously described as regulators of cell proliferation. -- Abstract: Nitration of tyrosine residues in proteins is associated with cell response to oxidative/nitrosative stress. Tyrosine nitration is relatively low abundant post-translational modification that may affect protein functions. Little is known about the extent of protein tyrosine nitration in cells during progression through the cell cycle. Here we report identification of proteins enriched for tyrosine nitration in cells synchronized in G0/G1, S or G2/M phases of the cell cycle. We identified 27 proteins in cells synchronized in G0/G1 phase, 37 proteins in S phase synchronized cells, and 12 proteins related to G2/M phase. Nineteen of the identified proteins were previously described as regulators of cell proliferation. Thus, our data indicate which tyrosine nitrated proteins may affect regulation of the cell cycle.

  13. Process for decomposing nitrates in aqueous solution

    DOEpatents

    Haas, Paul A.

    1980-01-01

    This invention is a process for decomposing ammonium nitrate and/or selected metal nitrates in an aqueous solution at an elevated temperature and pressure. Where the compound to be decomposed is a metal nitrate (e.g., a nuclear-fuel metal nitrate), a hydroxylated organic reducing agent therefor is provided in the solution. In accordance with the invention, an effective proportion of both nitromethane and nitric acid is incorporated in the solution to accelerate decomposition of the ammonium nitrate and/or selected metal nitrate. As a result, decomposition can be effected at significantly lower temperatures and pressures, permitting the use of system components composed of off-the-shelf materials, such as stainless steel, rather than more costly materials of construction. Preferably, the process is conducted on a continuous basis. Fluid can be automatically vented from the reaction zone as required to maintain the operating temperature at a moderate value--e.g., at a value in the range of from about 130.degree.-200.degree. C.

  14. Organic Nitrate Therapy, Nitrate Tolerance, and Nitrate-Induced Endothelial Dysfunction: Emphasis on Redox Biology and Oxidative Stress

    PubMed Central

    2015-01-01

    Abstract Organic nitrates, such as nitroglycerin (GTN), isosorbide-5-mononitrate and isosorbide dinitrate, and pentaerithrityl tetranitrate (PETN), when given acutely, have potent vasodilator effects improving symptoms in patients with acute and chronic congestive heart failure, stable coronary artery disease, acute coronary syndromes, or arterial hypertension. The mechanisms underlying vasodilation include the release of •NO or a related compound in response to intracellular bioactivation (for GTN, the mitochondrial aldehyde dehydrogenase [ALDH-2]) and activation of the enzyme, soluble guanylyl cyclase. Increasing cyclic guanosine-3′,-5′-monophosphate (cGMP) levels lead to an activation of the cGMP-dependent kinase I, thereby causing the relaxation of the vascular smooth muscle by decreasing intracellular calcium concentrations. The hemodynamic and anti-ischemic effects of organic nitrates are rapidly lost upon long-term (low-dose) administration due to the rapid development of tolerance and endothelial dysfunction, which is in most cases linked to increased intracellular oxidative stress. Enzymatic sources of reactive oxygen species under nitrate therapy include mitochondria, NADPH oxidases, and an uncoupled •NO synthase. Acute high-dose challenges with organic nitrates cause a similar loss of potency (tachyphylaxis), but with distinct pathomechanism. The differences among organic nitrates are highlighted regarding their potency to induce oxidative stress and subsequent tolerance and endothelial dysfunction. We also address pleiotropic effects of organic nitrates, for example, their capacity to stimulate antioxidant pathways like those demonstrated for PETN, all of which may prevent adverse effects in response to long-term therapy. Based on these considerations, we will discuss and present some preclinical data on how the nitrate of the future should be designed. Antioxid. Redox Signal. 23, 899–942. PMID:26261901

  15. Organic Nitrate Therapy, Nitrate Tolerance, and Nitrate-Induced Endothelial Dysfunction: Emphasis on Redox Biology and Oxidative Stress.

    PubMed

    Daiber, Andreas; Münzel, Thomas

    2015-10-10

    Organic nitrates, such as nitroglycerin (GTN), isosorbide-5-mononitrate and isosorbide dinitrate, and pentaerithrityl tetranitrate (PETN), when given acutely, have potent vasodilator effects improving symptoms in patients with acute and chronic congestive heart failure, stable coronary artery disease, acute coronary syndromes, or arterial hypertension. The mechanisms underlying vasodilation include the release of •NO or a related compound in response to intracellular bioactivation (for GTN, the mitochondrial aldehyde dehydrogenase [ALDH-2]) and activation of the enzyme, soluble guanylyl cyclase. Increasing cyclic guanosine-3',-5'-monophosphate (cGMP) levels lead to an activation of the cGMP-dependent kinase I, thereby causing the relaxation of the vascular smooth muscle by decreasing intracellular calcium concentrations. The hemodynamic and anti-ischemic effects of organic nitrates are rapidly lost upon long-term (low-dose) administration due to the rapid development of tolerance and endothelial dysfunction, which is in most cases linked to increased intracellular oxidative stress. Enzymatic sources of reactive oxygen species under nitrate therapy include mitochondria, NADPH oxidases, and an uncoupled •NO synthase. Acute high-dose challenges with organic nitrates cause a similar loss of potency (tachyphylaxis), but with distinct pathomechanism. The differences among organic nitrates are highlighted regarding their potency to induce oxidative stress and subsequent tolerance and endothelial dysfunction. We also address pleiotropic effects of organic nitrates, for example, their capacity to stimulate antioxidant pathways like those demonstrated for PETN, all of which may prevent adverse effects in response to long-term therapy. Based on these considerations, we will discuss and present some preclinical data on how the nitrate of the future should be designed.

  16. Nitrate in groundwater in the United States

    NASA Astrophysics Data System (ADS)

    Burow, K. R.; Nolan, B. T.; Rupert, M. G.; Dubrovsky, N. M.

    2009-12-01

    An assessment of nitrate concentrations in groundwater in the United States (US) indicates that concentrations are highest in shallow, oxic groundwater beneath areas with high nitrogen inputs. During 1991-2003, 5,101 wells were sampled in 51 study areas throughout the US as part of the USGS National Water-Quality Assessment program. Well locations for individual 30-well networks were selected for sampling using a computerized, stratified, random site-selection procedure to minimize spatial bias. These well networks reflect the existing used resource in major aquifers represented by domestic wells (major aquifer studies), and recently recharged groundwater beneath dominant land-surface activities (land-use studies). Nitrate concentrations in groundwater were compared with nationally-available variables such as nonpoint-source nitrogen inputs, soils, water chemistry, and other aquifer and well construction characteristics to predict the conditions most vulnerable to high nitrate concentrations. Nitrate was detected at concentrations above background of 1.0 mg/L (as N) in 50% of the wells sampled. Shallow groundwater beneath agricultural land had the highest median concentration of nitrate (3.1 mg/L). Median nitrate in shallow groundwater beneath urban land (1.4 mg/L) was lower than beneath agricultural land, but was higher than the median in major aquifers (0.56 mg/L). Although most wells sampled in the shallow land-use studies were not used for drinking water, concentrations exceeded the US EPA drinking-water standard (MCL) of 10 mg/L in 20% of wells in the agricultural land-use setting. Concentrations exceeded the MCL in only 3% of wells in the urban land-use setting, and 4% of wells in major aquifers. Classification and regression tree analysis was used to identify the relative importance of nitrogen inputs, water chemistry, and physical aquifer properties on nitrate concentrations in groundwater. Factors ranked by reduction in sum of squares indicate that

  17. Historical Tracking of Nitrate in Contrasting Vineyard Using Water Isotopes and Nitrate Depth Profiles

    NASA Astrophysics Data System (ADS)

    Sprenger, M.; Erhardt, M.; Riedel, M.; Weiler, M.

    2015-12-01

    The European Water Framework Directive (EWFD) aims to achieve a good chemical status for the groundwater bodies in Europe by the year 2015. Despite the effort to reduce the nitrate pollution from agriculture within the last two decades, there are still many groundwater aquifers that exceed nitrate concentrations above the EWFD threshold of 50 mg/l. Viticulture is seen as a major contributor of nitrate leaching and sowing of a green cover was shown to have a positive effect on lowering the nitrate loads in the upper 90 cm of the soil. However, the consequences for nitrate leaching into the subsoil were not yet tested. We analyzed the nitrate concentrations and pore water stable isotope composition to a depth of 380 cm in soil profiles under an old vineyard and a young vineyard with either soil tillage or permanent green cover in between the grapevines. The pore water stable isotopes were used to calibrate a soil physical model, which was then used to infer the age of the soil water at different depths. This way, we could relate elevated nitrate concentrations below an old vineyard to tillage processes that took place during the winter two years before the sampling. We further showed that the elevated nitrate concentration in the subsoil of a young vineyard can be related to the soil tillage prior to the planting of the new vineyard. If the soil is kept bare due to tillage, a nitrate concentration of 200 kg NO3--N/ha is found in 290 to 380 cm depth 2.5 years after the installation of the vineyard. The amount of nitrate leaching is considerably reduced due to a seeded green cover between the grapevines that takes up a high share of the mobilized nitrate reducing a potential contamination of the groundwater.

  18. Nitrate in aquifers beneath agricultural systems

    USGS Publications Warehouse

    Burkart, M.R.; Stoner, J.D.; ,

    2007-01-01

    Research from several regions of the world provides spatially anecdotal evidence to hypothesize which hydrologic and agricultural factors contribute to groundwater vulnerability to nitrate contamination. Analysis of nationally consistent measurements from the U.S. Geological Survey's NAWQA program confirms these hypotheses for a substantial range of agricultural systems. Shallow unconfined aquifers are most susceptible to nitrate contamination associated with agricultural systems. Alluvial and other unconsolidated aquifers are the most vulnerable and also shallow carbonate aquifers that provide a substantial but smaller contamination risk. Where any of these aquifers are overlain by permeable soils the risk of contamination is larger. Irrigated systems can compound this vulnerability by increasing leaching facilitated by additional recharge and additional nutrient applications. The system of corn, soybean, and hogs produced significantly larger concentrations of groundwater nitrate than all other agricultural systems because this system imports the largest amount of N-fertilizer per unit production area. Mean nitrate under dairy, poultry, horticulture, and cattle and grains systems were similar. If trends in the relation between increased fertilizer use and groundwater nitrate in the United States are repeated in other regions of the world, Asia may experience increasing problems because of recent increases in fertilizer use. Groundwater monitoring in Western and Eastern Europe as well as Russia over the next decade may provide data to determine if the trend in increased nitrate contamination can be reversed. If the concentrated livestock trend in the United States is global, it may be accompanied by increasing nitrogen contamination in groundwater. Concentrated livestock provide both point sources in the confinement area and intense non-point sources as fields close to facilities are used for manure disposal. Regions where irrigated cropland is expanding, such as

  19. Nitrate in aquifers beneath agricultural systems.

    PubMed

    Burkart, M R; Stoner, J D

    2007-01-01

    Research from several regions of the world provides spatially anecdotal evidence to hypothesize which hydrologic and agricultural factors contribute to groundwater vulnerability to nitrate contamination. Analysis of nationally consistent measurements from the U.S. Geological Survey's NAWQA program confirms these hypotheses for a substantial range of agricultural systems. Shallow unconfined aquifers are most susceptible to nitrate contamination associated with agricultural systems. Alluvial and other unconsolidated aquifers are the most vulnerable and also shallow carbonate aquifers that provide a substantial but smaller contamination risk. Where any of these aquifers are overlain by permeable soils the risk of contamination is larger. Irrigated systems can compound this vulnerability by increasing leaching facilitated by additional recharge and additional nutrient applications. The system of corn, soybean, and hogs produced significantly larger concentrations of groundwater nitrate than all other agricultural systems because this system imports the largest amount of N-fertilizer per unit production area. Mean nitrate under dairy, poultry, horticulture, and cattle and grains systems were similar. If trends in the relation between increased fertilizer use and groundwater nitrate in the United States are repeated in other regions of the world, Asia may experience increasing problems because of recent increases in fertilizer use. Groundwater monitoring in Western and Eastern Europe as well as Russia over the next decade may provide data to determine if the trend in increased nitrate contamination can be reversed. If the concentrated livestock trend in the United States is global, it may be accompanied by increasing nitrogen contamination in groundwater. Concentrated livestock provide both point sources in the confinement area and intense non-point sources as fields close to facilities are used for manure disposal. Regions where irrigated cropland is expanding, such as

  20. Nitrate removal from high strength nitrate-bearing wastes in granular sludge sequencing batch reactors.

    PubMed

    Krishna Mohan, Tulasi Venkata; Renu, Kadali; Nancharaiah, Yarlagadda Venkata; Satya Sai, Pedapati Murali; Venugopalan, Vayalam Purath

    2016-02-01

    A 6-L sequencing batch reactor (SBR) was operated for development of granular sludge capable of denitrification of high strength nitrates. Complete and stable denitrification of up to 5420 mg L(-1) nitrate-N (2710 mg L(-1) nitrate-N in reactor) was achieved by feeding simulated nitrate waste at a C/N ratio of 3. Compact and dense denitrifying granular sludge with relatively stable microbial community was developed during reactor operation. Accumulation of large amounts of nitrite due to incomplete denitrification occurred when the SBR was fed with 5420 mg L(-1) NO3-N at a C/N ratio of 2. Complete denitrification could not be achieved at this C/N ratio, even after one week of reactor operation as the nitrite levels continued to accumulate. In order to improve denitrification performance, the reactor was fed with nitrate concentrations of 1354 mg L(-1), while keeping C/N ratio at 2. Subsequently, nitrate concentration in the feed was increased in a step-wise manner to establish complete denitrification of 5420 mg L(-1) NO3-N at a C/N ratio of 2. The results show that substrate concentration plays an important role in denitrification of high strength nitrate by influencing nitrite accumulation. Complete denitrification of high strength nitrates can be achieved at lower substrate concentrations, by an appropriate acclimatization strategy.

  1. An unexpected truth: increasing nitrate loading can decrease nitrate export from watersheds

    NASA Astrophysics Data System (ADS)

    Askarizadeh Bardsiri, A.; Grant, S. B.; Rippy, M.

    2015-12-01

    The discharge of anthropogenic nitrate (e.g., from partially treated sewage, return flows from agricultural irrigation, and runoff from animal feeding operations) to streams can negatively impact both human and ecosystem health. Managing these many point and non-point sources to achieve some specific end-point—for example, reducing the annual mass of nitrate exported from a watershed—can be a challenge, particularly in rapidly growing urban areas. Adding to this complexity is the fact that streams are not inert: they too can add or remove nitrate through assimilation (e.g., by stream-associated plants and animals) and microbially-mediated biogeochemical reactions that occur in streambed sediments (e.g., respiration, ammonification, nitrification, denitrification). By coupling a previously published correlation for in-stream processing of nitrate [Mulholland et al., Nature, 2008, 452, 202-205] with a stream network model of the Jacksons Creek watershed (Victoria, Australia) I demonstrate that managing anthropogenic sources of stream nitrate without consideration of in-stream processing can result in a number of non-intuitive "surprises"; for example, wastewater effluent discharges that increase nitrate loading but decrease in-stream nitrate concentrations can reduce the mass of nitrate exported from a watershed.

  2. Contribution of atmospheric nitrate deposition to nitrate loading in the Chesapeake Bay. Final report

    SciTech Connect

    Tyler, M.

    1988-12-01

    Recent studies have suggested that nitrate introduced into the Chesapeake Bay via atmospheric deposition may be a significant source of excess nutrients. In order to determine if concerns about atmospheric deposition are justified, modeled estimates of wetfall nitrate deposition over the Chesapeake Bay basin, based on monitoring data collected in 1984, were used to estimate basin-wide nitrate loading (1.38 x 10/sup 8/ kg) over the land area of the basin. Estimates of transfer coefficients and nitrate loadings to the Bay for various land-use categories were also calculated, using figures developed by the EPA Chesapeake Bay Program. The conservative nature of assumptions made in developing these figures suggests that the actual percentage contribution of atmospheric nitrate deposition may be lower than the estimated value.

  3. An experimental and ab initio study on the abiotic reduction of uranyl by ferrous iron

    NASA Astrophysics Data System (ADS)

    Taylor, S. D.; Marcano, M. C.; Rosso, K. M.; Becker, U.

    2015-05-01

    It is important to understand the mechanisms controlling the removal of uranyl from solution from an environmental standpoint, particularly whether soluble Fe(II) is capable of reducing soluble U(VI) to insoluble U(IV). Experiments were performed to shed light into discrepancies of recent studies about precipitation of U-containing solids without changing oxidation states versus precipitation/reduction reactions, especially with respect to the kinetics of these reactions. To understand the atomistic mechanisms, thermodynamics, and kinetics of these redox processes, ab initio electron transfer (ET) calculations, using Marcus theory, were applied to study the reduction of U(VI)aq to U(V)aq by Fe(II)aq (the first rate-limiting ET-step). Outer-sphere (OS) and inner-sphere (IS) Fe-U complexes were modeled to represent simple species within a homogeneous environment through which ET could occur. Experiments on the chemical reduction were performed by reacting 1 mM Fe(II)aq at pH 7.2 with high (i.e., 0.16 mM) and lower (i.e., 0.02 mM) concentrations of U(VI)aq. At higher U concentration, a rapid decrease in U(VI)aq was observed within the first hour of reaction. XRD and XPS analyses of the precipitates confirmed the presence of (meta)schoepite phases, where up to ∼25% of the original U was reduced to U4+ and/or U5+-containing phases. In contrast, at 0.02 mM U, the U(VI)aq concentration remained fairly constant for the first 3 h of reaction and only then began to decrease due to slower precipitation kinetics. XPS spectra confirm the partial chemical reduction U associated with the precipitate (up to ∼30%). Thermodynamic calculations support that the reduction of U(VI)aq to U(IV)aq by Fe(II)aq is energetically unfavorable. The batch experiments in this study show U(VI) is removed from solution by precipitation and that transitioning to a heterogeneous system in turn enables the solid U phase to be partially reduced. Ab initio ET calculations revealed that OS ET is

  4. Uranyl Ion Complexes with Long-Chain Aliphatic α,ω-Dicarboxylates and 3d-Block Metal Counterions.

    PubMed

    Thuéry, Pierre; Harrowfield, Jack

    2016-03-01

    Twelve new complexes were obtained from reaction of uranyl ions with the aliphatic dicarboxylic acids HOOC-(CH2)n-2-COOH (H2Cn; n = 7-10 and 12) under solvo-hydrothermal conditions, in the presence of 3d-block metal ions (Mn(2+), Fe(3+), Co(2+), Ni(2+), and Cu(2+)) and 2,2'-bipyridine (bipy) or 1,10-phenanthroline (phen). In contrast to previously reported triple-stranded helicates obtained with C9(2-) and C12(2-), all these complexes crystallize as polymeric one-dimensional (1D) or two-dimensional (2D) species. [Fe(bipy)3][(UO2)2(C7)3]·3H2O (1), [Cu(phen)2]2[(UO2)3(C7)4(H2O)2]·2H2O (2), and [Cu(bipy)2]2[(UO2)2(C9)3] (6), in which the 3d cation was reduced in situ, are 1D ladderlike polymers displaying tetra- or hexanuclear rings, of sufficient width to encompass two counterions in 2 and 6. The three complexes [Co(phen)3][(UO2)3(C8)3(O)]·H2O (3), [Ni(phen)3][(UO2)3(C8)3(O)]·H2O (4) and [Co(phen)3][(UO2)3(C9)3(O)]·H2O (5) contain bis(μ3-oxo)-bridged tetranuclear secondary building units, and they crystallize as deeply furrowed 2D assemblies. Depending on the nature of the counterion, C10(2-) gives [Ni(bipy)3][(UO2)2(C10)3]·2H2O (7), a 2D network displaying elongated decanuclear rings containing the counterions, or [Mn(phen)3][(UO2)2(C10)3]·6H2O (8), [Co(phen)3][(UO2)2(C10)3]·7H2O (9), and [Ni(phen)3][(UO2)2(C10)3]·7H2O (10), which consist of 2D assemblies with honeycomb topology; the hexanuclear rings in 8-10 are chairlike and occupied by one counterion and two uranyl groups from neighboring layers. Two complexes of the ligand with the longest chain, C12(2-), are reported. [UO2(C12)(bipy)] (11) is a neutral 1D species in which bipy chelates the uranyl ion and plays an important role in the packing through π-stacking interactions. Two polymeric units, 1D and 2D, coexist in the complex [Ni(bipy)3][(UO2)2(C12)3][UO2(C12)(H2O)2]·H2O (12); the 2D network has the honeycomb topology, but the hexanuclear rings are markedly convoluted, with local features akin to

  5. Structural and mechanistic insights on nitrate reductases.

    PubMed

    Coelho, Catarina; Romão, Maria João

    2015-12-01

    Nitrate reductases (NR) belong to the DMSO reductase family of Mo-containing enzymes and perform key roles in the metabolism of the nitrogen cycle, reducing nitrate to nitrite. Due to variable cell location, structure and function, they have been divided into periplasmic (Nap), cytoplasmic, and membrane-bound (Nar) nitrate reductases. The first crystal structure obtained for a NR was that of the monomeric NapA from Desulfovibrio desulfuricans in 1999. Since then several new crystal structures were solved providing novel insights that led to the revision of the commonly accepted reaction mechanism for periplasmic nitrate reductases. The two crystal structures available for the NarGHI protein are from the same organism (Escherichia coli) and the combination with electrochemical and spectroscopic studies also lead to the proposal of a reaction mechanism for this group of enzymes. Here we present an overview on the current advances in structural and functional aspects of bacterial nitrate reductases, focusing on the mechanistic implications drawn from the crystallographic data. PMID:26362109

  6. Exclusion of Nitrate from Frozen Aqueous Solutions

    NASA Astrophysics Data System (ADS)

    Marrocco, H. A.; Michelsen, R. R.

    2013-12-01

    Reactions occurring at the surface of ice, sea ice, and snow in Earth's cryosphere have an impact on the composition of the overlying atmosphere. In order to elucidate reaction mechanisms and model their contributions to atmospheric processes, the morphology of frozen aqueous surfaces and amounts of reactants contained therein must be determined. To this end, the exclusion of nitrate ions to the surface of frozen aqueous solutions has been studied by attenuated total reflection infrared spectroscopy (ATR-IR). In this technique the near-surface region of the frozen films are interrogated to a depth of a few hundred nanometers from the film-crystal interface. Aqueous solutions (0.001 to 0.01 M) of sodium nitrate (NaNO3), magnesium nitrate (Mg(NO3)2), and nitric acid (HNO3) were quickly frozen on the germanium ATR crystal and observed at a constant temperature of about -18°C. In addition to ice and the solutes, liquid water in varying amounts was observed in the spectra. The amount of nitrate in the surface liquid is three to four orders of magnitude higher than in the unfrozen solution. While all the nitrate salts exhibit exclusion to the unfrozen surface, the dynamics are different for different counter-ions. Results are compared to freezing point depression data and the predictions of equilibrium thermodynamics.

  7. Cutaneous candidiasis: treatment with miconazole nitrate.

    PubMed

    Cullin, S I

    1977-01-01

    In a well-controlled, double-blind, randomized study, 30 patients with cutaneous candidiasis were treated with a 2% miconazole nitrate lotion or its placebo control. By the 14th day, 13 of the 15 patients [87%] treated with miconazole nitrate achieved clinical and mycologic cures. Only a single patient treated with the placebo lotion would be classified as a therapeutic cure. In a second portion of the study those patients judged to be therapeutic failures were treated with the lotion containing 2% miconazole nitrate. By combining the results of both portions of the study we find that miconazole nitrate lotion produced both a clinical and mycologic cure in all patients receiving the active lotion. The miconazole lotion formula was well tolerated by all patients and no side effects were noted. The fact that miconazole nitrate acts rapidly in relieving symptoms, is well tolerated, and is highly effective against dermatophytes, yeasts and gram-positive bacteria, makes it a welcome addition to available topical therapy of skin infections.

  8. Ion Pairing in Alkali Nitrate Electrolyte Solutions.

    PubMed

    Xie, Wen Jun; Zhang, Zhen; Gao, Yi Qin

    2016-03-10

    In this study, we investigate the thermodynamics of alkali nitrate salt solutions, especially the formation of contact ion pairs between alkali cation and nitrate anion. The ion-pairing propensity shows an order of LiNO3 < NaNO3 < KNO3. Such results explain the salt activity coefficients and suggest that the empirical "law of matching water affinity" is followed by these alkali nitrate salt solutions. The spatial patterns of contact ion pairs are different in the three salt solutions studied here: Li(+) forms the contact ion pair with only one oxygen of the nitrate while Na(+) and K(+) can also be shared by two oxygens of the nitrate. In reproducing the salt activity coefficient using Kirkwood-Buff theory, we find that it is essential to include electronic polarization for Li(+) which has a high charge density. The electronic continuum correction for nonpolarizable force field significantly improves the agreement between the calculated activity coefficients and their experimental values. This approach also improves the performance of the force field on salt solubility. From these two aspects, this study suggests that electronic continuum correction can be a promising approach to force-field development for ions with high charge densities. PMID:26901167

  9. Measurement of Isoprene Nitrates by GCMS

    NASA Astrophysics Data System (ADS)

    Mills, Graham; Hiatt-Gipson, Glyn; Bew, Sean; Reeves, Claire

    2016-04-01

    We have, for the first time, synthesised and identified the majority of the primary isoprene nitrates (INs), formed by reaction of isoprene with the hydroxyl radical (OH) and nitrate radical (NO3) as described in the Master Chemical Mechanism (MCM). An instrument based on gas chromatography/mass spectrometry (GCMS) and the associated calibration methods is described for the speciated measurements of individual isoprene nitrate isomers. Seven of the primary isoprene nitrates formed by reaction of the OH with isoprene in the MCM and three primary isoprene nitrates from the reaction of the NO3 and isoprene are identified, including six newly synthesised INs. Simple photochemistry bag experiments were performed to demonstrate the capability to measure speciated INs in complex mixtures. Interestingly, the results showed isomeric distributions of INs that were quite different to those predicted by model calculations in earlier studies. In addition, we observed INs that we would expect from NO3 addition to isoprene despite the bag experiments being carried out in daylight conditions when we would expect OH to be the only isoprene oxidant.

  10. Ion Pairing in Alkali Nitrate Electrolyte Solutions.

    PubMed

    Xie, Wen Jun; Zhang, Zhen; Gao, Yi Qin

    2016-03-10

    In this study, we investigate the thermodynamics of alkali nitrate salt solutions, especially the formation of contact ion pairs between alkali cation and nitrate anion. The ion-pairing propensity shows an order of LiNO3 < NaNO3 < KNO3. Such results explain the salt activity coefficients and suggest that the empirical "law of matching water affinity" is followed by these alkali nitrate salt solutions. The spatial patterns of contact ion pairs are different in the three salt solutions studied here: Li(+) forms the contact ion pair with only one oxygen of the nitrate while Na(+) and K(+) can also be shared by two oxygens of the nitrate. In reproducing the salt activity coefficient using Kirkwood-Buff theory, we find that it is essential to include electronic polarization for Li(+) which has a high charge density. The electronic continuum correction for nonpolarizable force field significantly improves the agreement between the calculated activity coefficients and their experimental values. This approach also improves the performance of the force field on salt solubility. From these two aspects, this study suggests that electronic continuum correction can be a promising approach to force-field development for ions with high charge densities.

  11. Vulnerability of streams to legacy nitrate sources

    USGS Publications Warehouse

    Tesoriero, Anthony J.; Duff, John H.; Saad, David A.; Spahr, Norman E.; Wolock, David M.

    2013-01-01

    The influence of hydrogeologic setting on the susceptibility of streams to legacy nitrate was examined at seven study sites having a wide range of base flow index (BFI) values. BFI is the ratio of base flow to total streamflow volume. The portion of annual stream nitrate loads from base flow was strongly correlated with BFI. Furthermore, dissolved oxygen concentrations in streambed pore water were significantly higher in high BFI watersheds than in low BFI watersheds suggesting that geochemical conditions favor nitrate transport through the bed when BFI is high. Results from a groundwater-surface water interaction study at a high BFI watershed indicate that decades old nitrate-laden water is discharging to this stream. These findings indicate that high nitrate levels in this stream may be sustained for decades to come regardless of current practices. It is hypothesized that a first approximation of stream vulnerability to legacy nutrients may be made by geospatial analysis of watersheds with high nitrogen inputs and a strong connection to groundwater (e.g., high BFI).

  12. Combined uranous nitrate production consisting of undivided electrolytic cell and divided electrolytic cell (Electrolysis → Electrolytic cell)

    SciTech Connect

    Yuan, Zhongwei; Yan, Taihong; Zheng, Weifang; Li, Xiaodong; Yang, Hui; Xian, Liang

    2013-07-01

    The electrochemical reduction of uranyl nitrate is a green, mild way to make uranous ions. Undivided electrolyzers whose maintenance is less but their conversion ratio and current efficiency are low, have been chosen. However, at the beginning of undivided electrolysis, high current efficiency can also be maintained. Divided electrolyzers' conversion ratio and current efficiency is much higher because the re-oxidation of uranous on anode is avoided, but their maintenance costs are more, because in radioactive environment the membrane has to be changed after several operations. In this paper, a combined method of uranous production is proposed which consists of 2 stages: undivided electrolysis (early stage) and divided electrolysis (late stage) to benefit from the advantages of both electrolysis modes. The performance of the combined method was tested. The results show that in combined mode, after 200 min long electrolysis (80 min undivided electrolysis and 120 min divided electrolysis), U(IV) yield can achieve 92.3% (500 ml feed, U 199 g/l, 72 cm{sup 2} cathode, 120 mA/cm{sup 2}). Compared with divided mode, about 1/3 working time in divided electrolyzer is reduced to achieve the same U(IV) yield. If 120 min long undivided electrolysis was taken, more than 1/2 working time can be reduced in divided electrolyzer, which means that about half of the maintenance cost can also be reduced. (authors)

  13. Uranyl Acetate Induces Oxidative Stress and Mitochondrial Membrane Potential Collapse in the Human Dermal Fibroblast Primary Cells

    PubMed Central

    Daraie, Bahram; Pourahmad, Jalal; Hamidi-Pour, Neda; Hosseini, Mir-Jamal; Shaki, Fatemeh; Soleimani, Masoud

    2012-01-01

    Cytotoxicity of depleted uranium, as a byproduct of military has been came to spotlight in recent decades. DU is known as a chemical rather than radioactive hazard and efforts to illustrating its mechanism is undergo, but the precise complete molecular mechanisms are still unclear. Recent studies showed that uranium induces biological changes in many different target tissues, such as the kidney, brain and skin. The aim of this study was to assess the impact of depleted uranium exposure at the cellular level in the human dermal fibroblast primary cells. The human dermal fibroblast primary cells incubated with different concentration (250-750 μM) of depleted uranium. Cytotoxicity and mitochondrial function in this cell lines were determined with the LDH leakage assay and the MTT test respectively. MDA levels were measured for determination of Lipid peroxidation in DU treated cells. Besides glutathione depletion and apoptosis phenotype detection were also assessed to complete the mechanistic screening. Results showed that the cell viability ameliorates in concentration and time dependent manners following in 24, 48 and 72 h incubation with DU. Moreover the significant increase in lipid peroxidation and significant decrease in cellular GSH recorded in DU treated human dermal fibroblast primary cells suggesting the preoxidant effect of uranyl ions. Cytoprotective effects of N-acetylcysteine (NAC) and dramatic decrease of cell viability in buthionin sulfoxamid (BSO) pretreated cells indicated the possibility of a critical role for glutathione system in DU detoxification. Death pattern, in fibroblast cells following DU treatment was varied from apoptosis to necrosis while the time and concentration increased. Since ROS formation is the initiation step for cell apoptosis, the present studies suggest Uranyl-induced toxicity in the human dermal fibroblast primary cells originated from oxidative stress and lead to occurrence of programmed cell death. PMID:24250472

  14. Influence of (calcium-)uranyl-carbonate complexation on U(VI) sorption on Ca- and Na-bentonites.

    PubMed

    Meleshyn, A; Azeroual, M; Reeck, T; Houben, G; Riebe, B; Bunnenberg, C

    2009-07-01

    The influence of uranyl-carbonate and calcium-uranyl-carbonate complexations on the kinetics of U(VI) (approximately 3.4 x 10(-3) mol L(-1)) sorption from NaNO3 and Ca(NO3)2 solutions on Na- and Ca-bentonites at circumneutral ambient conditions was investigated. Complexation of U(VI) in Ca2UO2(CO3)3(aq) aqueous species, dominating the U(VI) speciation in Ca(NO3)2 solution, reduces its adsorption on bentonite by a factor of 2-3 in comparison with that in (UO2)2CO3(OH)3- species, dominating in NaNO3 solution, within the studied period of time (21 days). As a result of the dissolution of accessory calcite, Ca2UO2(CO3)3(aq) can be formed in the initially Ca-free solution in contact with either Na- or Ca-bentonite. U(VI) adsorption on Na-bentonite is a factor of approximately 2 higher than that on Ca-bentonite for solutions with the Ca2UO2(CO3)3(aq) complex dominating aqueous U(VI) speciation. This favors use of Na-bentonite over that of Ca-bentonite in final disposal of radioactive waste. Furthermore, the observed strong correlation between U(VI) adsorption and Mg release as a result of montmorillonite dissolution indicates in agreement with previous findings that under the applied conditions U(VI) is adsorbed on the edge surface of montmorillonite, which is a major mineral phase of the studied clays. PMID:19673282

  15. Design and Construction of Experiment for Direct Electron Irradiation of Uranyl Sulfate Solution: Bubble Formation and Thermal Hydraulics Studies

    SciTech Connect

    Chemerisov, Sergey; Gromov, Roman; Makarashvili, Vakho; Heltemes, Thad; Sun, Zaijing; Wardle, Kent E.; Bailey, James; Quigley, Kevin; Stepinski, Dominique; Vandegrift, George

    2014-10-01

    Argonne is assisting SHINE Medical Technologies in developing SHINE, a system for producing fission-product 99Mo using a D/T-accelerator to produce fission in a non-critical target solution of aqueous uranyl sulfate. We have developed an experimental setup for studying thermal-hydraulics and bubble formation in the uranyl sulfate solution to simulate conditions expected in the SHINE target solution during irradiation. A direct electron beam from the linac accelerator will be used to irradiate a 20 L solution (sector of the solution vessel). Because the solution will undergo radiolytic decomposition, we will be able to study bubble formation and dynamics and effects of convection and temperature on bubble behavior. These experiments will serve as a verification/ validation tool for the thermal-hydraulic model. Utilization of the direct electron beam for irradiation allows homogeneous heating of a large solution volume and simplifies observation of the bubble dynamics simultaneously with thermal-hydraulic data collection, which will complement data collected during operation of the miniSHINE experiment. Irradiation will be conducted using a 30-40 MeV electron beam from the high-power linac accelerator. The total electron-beam power will be 20 kW, which will yield a power density on the order of 1 kW/L. The solution volume will be cooled on the front and back surfaces and central tube to mimic the geometry of the proposed SHINE solution vessel. Also, multiple thermocouples will be inserted into the solution vessel to map thermal profiles. The experimental design is now complete, and installation and testing are in progress.

  16. Molecular Components of Nitrate and Nitrite Efflux in Yeast

    PubMed Central

    Cabrera, Elisa; González-Montelongo, Rafaela; Giraldez, Teresa; de la Rosa, Diego Alvarez

    2014-01-01

    Some eukaryotes, such as plant and fungi, are capable of utilizing nitrate as the sole nitrogen source. Once transported into the cell, nitrate is reduced to ammonium by the consecutive action of nitrate and nitrite reductase. How nitrate assimilation is balanced with nitrate and nitrite efflux is unknown, as are the proteins involved. The nitrate assimilatory yeast Hansenula polymorpha was used as a model to dissect these efflux systems. We identified the sulfite transporters Ssu1 and Ssu2 as effective nitrate exporters, Ssu2 being quantitatively more important, and we characterize the Nar1 protein as a nitrate/nitrite exporter. The use of strains lacking either SSU2 or NAR1 along with the nitrate reductase gene YNR1 showed that nitrate reductase activity is not required for net nitrate uptake. Growth test experiments indicated that Ssu2 and Nar1 exporters allow yeast to cope with nitrite toxicity. We also have shown that the well-known Saccharomyces cerevisiae sulfite efflux permease Ssu1 is also able to excrete nitrite and nitrate. These results characterize for the first time essential components of the nitrate/nitrite efflux system and their impact on net nitrate uptake and its regulation. PMID:24363367

  17. Ammonium and nitrate tolerance in lichens.

    PubMed

    Hauck, Markus

    2010-05-01

    Since lichens lack roots and take up water, solutes and gases over the entire thallus surface, these organisms respond more sensitively to changes in atmospheric purity than vascular plants. After centuries where effects of sulphur dioxide and acidity were in the focus of research on atmospheric chemistry and lichens, recently the globally increased levels of ammonia and nitrate increasingly affect lichen vegetation and gave rise to intense research on the tolerance of lichens to nitrogen pollution. The present paper discusses the main findings on the uptake of ammonia and nitrate in the lichen symbiosis and to the tolerance of lichens to eutrophication. Ammonia and nitrate are both efficiently taken up under ambient conditions. The tolerance to high nitrogen levels depends, among others, on the capability of the photobiont to provide sufficient amounts of carbon skeletons for ammonia assimilation. Lowly productive lichens are apparently predisposed to be sensitive to excess nitrogen.

  18. Organic nitrates: past, present and future.

    PubMed

    França-Silva, Maria S; Balarini, Camille M; Cruz, Josiane C; Khan, Barkat A; Rampelotto, Pabulo H; Braga, Valdir A

    2014-09-24

    Nitric oxide (NO) is one of the most important vasodilator molecules produced by the endothelium. It has already been established that NO/cGMP signaling pathway deficiencies are involved in the pathophysiological mechanisms of many cardiovascular diseases. In this context, the development of NO-releasing drugs for therapeutic use appears to be an effective alternative to replace the deficient endogenous NO and mimic the role of this molecule in the body. Organic nitrates represent the oldest class of NO donors that have been clinically used. Considering that tolerance can occur when these drugs are applied chronically, the search for new compounds of this class with lower tolerance potential is increasing. Here, we briefly discuss the mechanisms involved in nitrate tolerance and highlight some achievements from our group in the development of new organic nitrates and their preclinical application in cardiovascular disorders.

  19. Nitrate in aquifers beneath agricultural systems

    USGS Publications Warehouse

    Burkart, M.R.; Stoner, J.D.

    2002-01-01

    Research from several regions of the world provides spatially anecdotal evidence to hypothesize which hydrologic and agricultural factors contribute to groundwater vulnerability to nitrate contamination. Analysis of nationally consistent measurements from the U.S. Geological Survey's NAWOA program confirms these hypotheses for a substantial range of agricultural systems. Shallow unconfined aquifers are most susceptible to nitrate contamination associated with agricultural systems. Alluvial and other unconsolidated aquifers are the most vulnerable and shallow carbonate aquifers provide a substantial but smaller contamination risk. Where any of these aquifers are overlain by permeable soils the risk of contamination is larger. Irrigated systems can compound this vulnerability by increasing leaching facilitated by additional recharge and additional nutrient applications. The agricultural system of corn, soybeans, and hogs produced significantly larger concentrations of groundwater nitrate than all other agricultural systems, although mean nitrate concentrations in counties with dairy, poultry, cattle and grains, and horticulture systems were similar. If trends in the relation between increased fertilizer use and groundwater nitrate in the United States are repeated in other regions of the world, Asia may experience increasing problems because of recent increases in fertilizer use. Groundwater monitoring in Western and Eastern Europe as well as Russia over the next decade may provide data to determine if the trend in increased nitrate contamination can be reversed. If the concentrated livestock trend in the United States is global, it may be accompanied by increasing nitrogen contamination in groundwater. Concentrated livestock provide both point sources in the confinement area and intense non-point sources as fields close to facilities are used for manure disposal. Regions where irrigated cropland is expanding, such as in Asia, may experience the greatest impact of

  20. Halide Ion Enhancement of Nitrate Ion Photolysis

    NASA Astrophysics Data System (ADS)

    Richards, N. K.; Wingen, L. M.; Callahan, K. M.; Tobias, D. J.; Finlayson-Pitts, B. J.

    2009-12-01

    Nitrate ion photochemistry is an important source of NOx in the polar regions. It is uncertain whether coexisting ions such as halides play a role in nitrate photochemistry. The effect of halides on NO3 photolysis was investigated using photolysis experiments in 230 L Teflon chambers that contain deliquesced aerosols of NaBr:NaNO3, KBr:KNO3 and ternary mixtures of NaCl:NaBr:NaNO3. Gas phase NO2 and gaseous halogen products were measured as a function of photolysis time using long path FTIR, NOx chemiluminescence and API-MS (atmospheric pressure ionization mass spectrometry). Experiments were conducted with NO3- held at a constant 0.5 M and with the amount of total halide concentration varying from 0.25 M to 4 M. Studies on NaBr:NaNO3 mixtures suggest that as the bromide ion to nitrate ion ratio increases, there is an enhancement in the rate of production of NO2 in the nitrate-bromide mixtures over that formed in the photolysis of NaNO3. Molecular dynamic (MD) simulations provide molecular level insight into the ions near the air-water interface in the aqueous halide-nitrate mixtures. These studies suggest that the presence of sodium halides at the air-water interface may encourage some nitrate ions to approach the top layers of water, allowing for more efficient escape of photoproducts than is seen in the absence of halides. Experiments on mixtures of KBr:KNO3 are being conducted to determine potential cation effects. In addition, ternary mixtures of NaCl:NaBr:NaNO3 are being examined to determine the effects of mixtures of halides on production of NO2 and gaseous halogen products. The implications of this photochemistry for tropospheric chemistry will be discussed.