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Sample records for ligand promoted dissolution

  1. Iron isotope fractionation during proton-promoted, ligand-controlled, and reductive dissolution of Goethite.

    PubMed

    Wiederhold, Jan G; Kraemer, Stephan M; Teutsch, Nadya; Borer, Paul M; Halliday, Alex N; Kretzschmar, Ruben

    2006-06-15

    Iron isotope fractionation during dissolution of goethite (alpha-FeOOH) was studied in laboratory batch experiments. Proton-promoted (HCl), ligand-controlled (oxalate dark), and reductive (oxalate light) dissolution mechanisms were compared in order to understand the behavior of iron isotopes during natural weathering reactions. Multicollector ICP-MS was used to measure iron isotope ratios of dissolved iron in solution. The influence of kinetic and equilibrium isotope fractionation during different time scales of dissolution was investigated. Proton-promoted dissolution did not cause iron isotope fractionation, concurrently demonstrating the isotopic homogeneity of the goethite substrate. In contrast, both ligand-controlled and reductive dissolution of goethite resulted in significant iron isotope fractionation. The kinetic isotope effect, which caused an enrichment of light isotopes in the early dissolved fractions, was modeled with an enrichment factor for the 57Fe/ 54Fe ratio of -2.6 per thousandth between reactive surface sites and solution. Later dissolved fractions of the ligand-controlled experiments exhibit a reverse trend with a depletion of light isotopes of approximately 0.5 per thousandth in solution. We interpret this as an equilibrium isotope effect between Fe(III)-oxalate complexes in solution and the goethite surface. In conclusion, different dissolution mechanisms cause diverse iron isotope fractionation effects and likely influence the iron isotope signature of natural soil and weathering environments. PMID:16830543

  2. Oxalate adsorption at a plagioclase (An47) surface and models for ligand-promoted dissolution

    USGS Publications Warehouse

    Stillings, L.L.; Drever, J.I.; Poulson, S.R.

    1998-01-01

    Previous work on adsorption of oxalate at aluminosilicate surfaces suggests that maximum adsorption occurs through a bidentate attachment of the organic ligand, at near-neutral pH. Rates of ligand-promoted dissolution are expected to be greatest at this pH as well. We tested this model by measuring oxalate adsorption on the surface of andesine (An47), in solutions of pH 3- 5 and total oxalate concentrations of 0-8 mM. Contrary to expectation, the greatest adsorption density of 24 ??mol m-2 total oxalate was observed at pH 3 and 8 mM total oxalate. Adsorption is dependent upon the activities of both oxalate (C2O42-) and bioxalate (HC2O4-) in solution and can be modeled with either a two-term Langmuir or a two-term Freundlich isotherm. A Freundlich adsorption model provided the best fit to rate data because it was not constrained to a finite number of adsorption sites, as was the Langmuir model. The two-term ligand adsorption model was incorporated into a rate model: R(tot) = k(H-)[H(ads)/+](L) + k(HOx-)[HOx(ads)/-] + k(Ox2- )[Ox2(ads)/-] where R(tot) is the net dissolution rate of the feldspar, [i(ads)] is the concentration of species i adsorbed to the surface, and k(i) is the rate constant for release of the surface complex. The model was fit to data for oxalate-promoted dissolution of andesine, resulting in estimates for the rate constants of k(HOx-) = 1.16 x 10-12, k(Ox2-) = 1.05 x 10-12, and k(H-) = 9.61 x 10-13 mol of feldspar (??mol of i) (??mol of i)-1 s-1.Previous work on adsorption of oxalate at aluminosilicate surfaces suggests that maximum adsorption occurs through a bidentate attachment of the organic ligand, at near-neutral pH. Rates of ligand-promoted dissolution are expected to be greatest at this pH as well. We tested this model by measuring oxalate adsorption on the surface of andesine (An47), in solutions of pH 3-5 and total oxalate concentrations of 0-8 mM. Contrary to expectation, the greatest adsorption density of 24 ??mol m-2 total oxalate was

  3. Examination of Uranium(VI) Leaching During Ligand Promoted Dissolution of Waste Tank Sludge Surrogates

    SciTech Connect

    Powell, Brian; Powell, Brian A.; Rao, Linfeng; Nash, Kenneth. L.

    2008-06-10

    The dissolution of synthetic boehmite (?-AlOOH) by 1-hydroxyethane-1,1-diphosphonic acid (HEDPA) was examined in a series of batch adsorption/dissolution experiments. Additionally, the leaching behavior of {sup 233}U(VI) from boehmite was examined as a function of pH and HEDPA concentration. The results are discussed in terms of sludge washing procedures that may be utilized during underground tank waste remediation. In the pH range 4 to 10, complexation of Al(III) by HEDPA significantly enhanced dissolution of boehmite. This phenomenon was especially pronounced in the neutral pH region where the solubility of aluminum, in the absence of complexants, is limited by the formation of sparsely soluble aluminum hydroxides. At pH higher than 10, dissolution of synthetic boehmite was inhibited by HEDPA, likely due to sorption of Al(III):HEDPA complexes. Addition of HEDPA to equilibrated U(VI)-synthetic boehmite suspensions yielded an increase in the aqueous phase uranium concentration. Partitioning of uranium between the solid and aqueous phase is described in terms of U(VI):HEDPA speciation and dissolution of the boehmite solid phase.

  4. Do organic ligands affect calcite dissolution rates?

    NASA Astrophysics Data System (ADS)

    Oelkers, Eric H.; Golubev, Sergey V.; Pokrovsky, Oleg S.; Bénézeth, Pascale

    2011-04-01

    Steady state Iceland-spar calcite dissolution rates were measured at 25 °C in aqueous solutions containing 0.1 M NaCl and up to 0.05 M dissolved bicarbonate at pH from 7.9 to 9.1 in the presence of 13 distinct dissolved organic ligands in mixed-flow reactors. The organic ligands considered in this study include those most likely to be present in either (1) aquifers at the conditions pertinent to CO 2 sequestration or (2) soil/early diagenetic environments: acetate, phthalate, citrate, EDTA 4-, succinate, D-glucosaminate, L-glutamate, D-gluconate, 2,4-dihydroxybenzoate, 3,4-dihydroxybenzoate, fumarate, malonate, and gallate. Results show that the presence of <0.05 mol/kg of these organic anions changes calcite dissolution rates by less than a factor of 2.5 with the exception of citrate and EDTA 4-. The presence of 0.05 mol/kg citrate and EDTA 4- increases calcite dissolution rates by as much as a factor of 35 and 500, respectively, compared to rates in organic anion-free solutions. Further calcite dissolution experiments were performed in the presence of organic polymers similar to bacterial exudates, cell exopolysaccharides, and analogs of microbial cell envelopes: alginate, lichen extract, humic acid, pectin, and gum xanthan. In no case did the presence of <100 ppm of these organics change calcite dissolution rates by more than a factor of 2.5. Results obtained in this study suggest that the presence of aqueous organic anions negligibly affects calcite forward dissolution rates in most natural environments. Some effect on calcite reactivity may be observed, however, by the presence of organic anions if they change substantially the chemical affinity of the fluid with respect to calcite.

  5. Siderophore-promoted dissolution of cobalt from hydroxide minerals

    NASA Astrophysics Data System (ADS)

    Bi, Yuqiang; Hesterberg, Dean L.; Duckworth, Owen W.

    2010-05-01

    Recent research has revealed that siderophores, a class of biogenic ligands with high affinities for Fe(III), can also strongly complex Co(III), an element essential to the normal metabolic function of microbes and animals. This study was conducted to quantify the rates and identify the products and mechanisms of the siderophore-promoted dissolution of Co from synthetic Co-bearing minerals. The dissolution reactions of heterogenite (CoOOH) and four Co-substituted goethites (Co-FeOOH) containing different Co concentrations were investigated in the presence of a trihydroxamate siderophore, desferrioxamine B (DFOB), using batch and flow-through experiments. Results showed that DFOB-promoted dissolution of Co from Co-bearing minerals may occur via pH-dependent ligand-promoted or reductive dissolution mechanisms. For heterogenite, ligand-promoted dissolution was the dominant pathway at neutral to alkaline pH, while production of dissolved Co(II) for pH <6. It was not possible from our data to decouple the separate contributions of homogenous and heterogeneous reduction reactions to the aqueous Co(II) pool. Cobalt substitution in Co-substituted goethite, possibly caused by distortion of goethite structure and increased lattice strain, resulted in enhanced total dissolution rates of both Co and Fe. The DFOB-promoted dissolution rates of Co-bearing minerals, coupled with the high affinity of Co(III) for DFOB, suggest that siderophores may be effective for increasing Co solubility, and thus possibly Co bioavailability. The results also suggest that siderophores may contribute to the mobilization of radioactive 60Co from Co-bearing mineral phases through mineral weathering and dissolution processes.

  6. Dissolution of Technetium(IV) Oxide by Natural and Synthetic Organic Ligands Under both Reducing and Oxidizing Conditions

    SciTech Connect

    Gu, Baohua; Dong, W.; Liang, Liyuan; Wall, Nathalie

    2011-01-01

    Technetium-99 (Tc) in nuclear waste is a significant environmental concern due to its long half-life and high mobility in the subsurface. Reductive precipitation of Tc(IV) oxides [TcO2(s)] is an effective means of immobilizing Tc, thereby impeding its migration in groundwater. However, TcO2(s) is subject to dissolution by oxidants and/or complexing agents. In this study we ascertain the effects of a synthetic organic ligand, ethylenediaminetetraacetate (EDTA), and two natural humic isolates on the dissolution and solubility of Tc(IV) oxides. Pure synthetic TcO2(s) (0.23 mM) was used in batch experiments to determine dissolution kinetics at pH ~6 under both reducing and oxidizing conditions. All organic ligands were found to enhance the dissolution of Tc(IV) oxides, increasing their solubility from ~10-8 M (without ligands) to 4 10-7 M under strictly anoxic conditions. Reduced Tc(IV) was also found to re-oxidize rapidly under oxic conditions, with an observed oxidative dissolution rate approximately an order of magnitude higher than that of ligand-promoted dissolution under reducing conditions. Significantly, oxidative dissolution was inhibited by EDTA but enhanced by humic acid compared with experiments without any complexing agents. The redox functional properties of humics, capable of facilitating intra-molecular electron transfer, may account for this increased oxidation rate under oxic conditions. Our results highlight the importance of complex interactions for the stability and mobility of Tc, and thus for the long-term fate of Tc in contaminated environments.

  7. Steady-state dissolution kinetics of aluminum-goethite in the presence of desferrioxamine-B and oxalate ligands.

    PubMed

    Cervini-Silva, Javiera; Sposito, Garrison

    2002-02-01

    This paper reports steady-state dissolution rates of synthetic low-substitution Al-goethites (mol % Al < 10) at pH 5 in the presence of the trihydroxamate siderophore, desferrioxamine B (DFO-B), and the common biological ligand, oxalate. The siderophore-promoted Fe release rate increased both with the level of Al substitution and with DFO-B concentration up to about 100 microM, after which a plateau occurred, suggesting a saturation effect from DFO-B adsorption as a precursor to dissolution. At concentrations above 200 microM, oxalate also enhanced the Fe release rate, which however was not influenced by Al substitution. For Al-goethites with mol % Al < 4, the Fe release rate in the presence of 40 microM DFO-B together with varying concentrations of oxalate was typically greater than the corresponding sum of dissolution rates in the presence of the two ligands alone. This synergism may be the combined result of the ability of oxalate to adsorb strongly at the goethite surface, thus promoting Fe release, and of the high selectivity of DFO for Fe(III). Ferric oxalate complexes formed during dissolution will likely lose Fe3+ by ligand substitution with DFO-B, leading to the production of Fe(HDFO-B)+ and uncomplexed oxalate, the latter of which, in turn, could adsorb to the goethite surface again. For Al-goethites with mol % Al > 4, synergism was not apparent, which may signal the effect of a decreased surface density of Fe-OH sites associated with Al for Fe substitution. The oxalate-promoted release rates of Al did not scale with those of Fe, indicating incongruent dissolution. However, Al release rates in the presence of DFO-B did scale approximately with those of Fe but were not affected by the concentration of siderophore. These results are consistent with the presence of Al(OH)3 inclusions in Al-goethite. PMID:11871546

  8. Organic Ligands And The Dissolution Of Iron- Laden Dust In Seawater

    NASA Astrophysics Data System (ADS)

    RS, S. T.; Sander, S.; Boyd, P. W.

    2013-12-01

    Atmospherically supplied dust deposition has proven to be a critical source of iron (Fe) to high nitrate - low chlorophyll (HNLC) oceanic regions. The low solubility (Ksp = 2 x 10-39) of the hydrolysis species of Fe (Fe (III) oxyhydroxide solids) renders Fe to become less bioavailable. Fe is kept in the dissolved form by organic ligands above this solubility limit. The dissolution of Fe (III) bearing minerals in the presence of siderophores has been the subject of numerous recent studies. For our study, different dust dissolution experiments were carried out on Australian dust and iron minerals (goethite and lepidocrocite) using surface ocean water from different latitudes collected during the GEOTRACES Pacific ocean cruise in June 2011 and Iron Cycle III - Spring Bloom voyage in September 2012 to determine the effect of the presence or absence of siderophore (desferrioxamine B (DFB)), oxalate and light on the dissolution of Fe from dust. Short- and long- term dissolution experiments were performed at ambient seawater pH. Iron species were measured by electrochemical methods or chemiluminescence, and HPLC-ESI-MS was used to study structural changes of the organic ligands. In all cases iron dissolution was observed, with the largest increase being observed in the presence of DFB and light. Addition of the weak ligand and electron donor oxalate had no significant effect on the dissolution. The results indicate that light and the complexing capacity of the ligands critically affects the dissolution process. Preliminary results show that a maximum dissolved iron concentration was reached three hours after the addition of the dust, which subsequently decreased again. This observation might be due to the onsetting precipitation of iron. We will also present results from an artificial iron-mineral dissolution experiment conducted under comparable conditions.

  9. Microbial exudate promoted dissolution and transformation of chromium containing minerals

    NASA Astrophysics Data System (ADS)

    Saad, E. M.; Sun, J.; Tang, Y.

    2015-12-01

    Because of its utility in many industrial processes, chromium has become the second most common metal contaminant in the United States. The two most common oxidation states of chromium in nature are Cr(III), which is highly immobile, and Cr(VI), which is highly mobile and toxic. In both natural and engineered environments, the most common remediation of Cr(VI) is through reduction, which results in chromium sequestration in the low solubility mixed Cr(III)-Fe(III) (oxy)hydroxide phases. Consequently, the stability of these minerals must be examined to assess the fate of chromium in the subsurface. We examined the dissolution of mixed Cr(III)-Fe(III) (oxy)hydroxides in the presence of common microbial exudates, including the siderophore desferrioxamine B (DFOB; a common organic ligand secreted by most microbes with high affinity for ferric iron and other trivalent metal ions) and oxalate (a common organic acid produced by microbes). The solids exhibited incongruent dissolution with preferential leaching of Fe from the solid phase. Over time, this leads to a more Cr rich mineral, which is known to be more soluble than the corresponding mixed mineral phase. We are currently investigating the structure of the reacted mineral phases and soluble Cr(III) species, as well as the potential oxidation and remobilization of the soluble Cr species. Results from this study will provide insights regarding the long term transport and fate of chromium in the natural environment in the presence of microbial activities.

  10. Simulating Succinate-Promoted Dissolution at Calcite {104} Steps

    NASA Astrophysics Data System (ADS)

    Mkhonto, D.; Sahai, N.

    2008-12-01

    Organic molecules of a wide range of molecular weights from small organic acids, amino-acids, acidic peptides and acidic proteins to humic and fulvic acids play a key role in modulating nucleation, crystal growth and dissolution of calcium carbonate polymorphs. In general, these acidic molecules inhibit calcite growth and, promote dissolution preferentially along specific crystallographic directions, in the process, regulating crystal shape and size, and even whether a metastable polymorph (e.g., vaterite or aragonite) is nucleated first. For example, chiral faces of calcite are selected by chiral amino-acids and the unusual {hk0} faces are expressed in the presence of amino-acids [Orme et al., 2001], and unusual heptagonal dissolution etch-pit are seen in the presence of succinate compared to the normal rhombohedral pits in water alone [Teng et al., 2006]. Thus, the presence of unusual crystal morphologies may indicate organic-mediated growth, thus serving as a biosignature. We have conducted the Molecular Dynamics (MD) simulations using the Consistent Valence Force Field (CVFF) as implemented in the FORCITE© module of the Materials Studio © software package (Accelrys, Inc. TM) to model the adsorption of succinate, a dicarboxylic acid, and charge- balancing Na+ ions on dry and hydrated steps in different directions on the {104} cleavage face of calcite [Mkhonto and Sahai, in prep.]. At the site of succinate adsorption, we find elongation of the interatomic distances (Ca-OCO3,i) between surface Ca2+ cation and the oxygen of the underlying inorganic CO32- anion the first surface layer of calcite, compared to the corresponding distances in the presence of water alone, suggesting greater ease of surface Ca2+ detachment. This result is consistent with the empirically observed increase in overall dissolution rate with succinate [Teng et al., 2006]. Furthermore, succinate adsorption lowers the step energies, which explains the appearance of steps in the unsusual [42

  11. Effect of pH and organic ligands on the kinetics of smectite dissolution at 25 °C

    NASA Astrophysics Data System (ADS)

    Golubev, Sergey V.; Bauer, Andreas; Pokrovsky, Oleg S.

    2006-09-01

    Forward dissolution rates of Na-Montmorillonite (Wyoming) SWy-2 smectite (Ca 0.06Na 0.56)[Al 3.08Fe(III) 0.38Mg 0.54] [Si 7.93 Al 0.07]O 20(OH) 4 were measured at 25 °C in a mixed-flow reactor equipped with interior dialysis compartment (6-8 kDa membrane) as a function of pH (1-12), dissolved carbonate (0.5-10 mM), phosphate (10 -5 to 0.03 M), and nine organic ligands (acetate, oxalate, citrate, EDTA, alginate, glucuronic acid, 3,4-dihydroxybenzoic acid, gluconate, and glucosamine) in the concentration range from 10 -5 to 0.03 M. In organic-free solutions, the Si-based rates decrease with increasing pH at 1 ⩽ pH ⩽ 8 with a slope close to -0.2. At 9 ⩽ pH ⩽ 12, the Si-based rates increase with a slope of ˜0.3. In contrast, non-stoichiometric Mg release weakly depends on pH at 1 ⩽ pH ⩽ 12 and decreases with increasing pH. The empirical expression describing Si-release rates [ R, mol/cm 2/s] obtained in the present study at 25 °C, I = 0.01 M is given by R=2.2·10-17·aH0.21+1.0·10-20+6·10-17·aOH0.33 At circum-neutral pH, the Si-release-based dissolution is promoted by the addition of the following ligands ranked by decreasing effectiveness: EDTA > 3,4-DHBA > citrate ⩾ oxalate. Phosphate, glucuronate, glucosamine, gluconate, alginate, and acetate act as inhibitors of dissolution and HCO 3-, CO 32- exhibit no effect on dissolution rate. Non-stoichiometric, non-steady-state Mg release was very weakly affected by the presence of ligands. Analysis of reacted solid products using XRD, FT-IR, and XPS revealed no major change in structure, surface chemical composition or specific surface area as a function of pH, ligand concentration, and duration of experiments. Ligand-affected rates re-calculated to constant pH were interpreted using a phenomenological equation which postulates the Langmurian adsorption of a ligand on surface sites. Overall, results of this study demonstrate that very high concentrations (0.001-0.01 M) of organic ligands, whether they are

  12. Polarization Transfer from Ligands Hyperpolarized by Dissolution Dynamic Nuclear Polarization for Screening in Drug Discovery.

    PubMed

    Min, Hlaing; Sekar, Giridhar; Hilty, Christian

    2015-09-01

    Nuclear magnetic resonance (NMR) spectroscopy is a valuable technique for ligand screening, because it exhibits high specificity toward chemical structure and interactions. Dissolution dynamic nuclear polarization (DNP) is a recent advance in NMR methodology that enables the creation of non-equilibrium spin states, which can dramatically increase NMR sensitivity. Here, the transfer of such spin polarization from hyperpolarized ligand to protein is observed. Mixing hyperpolarized benzamidine with the serine protease trypsin, a "fingerprint" of enhanced protein signals is observed, which shows a different intensity profile than the equilibrium NMR spectrum of the protein, but coincides closely to the frequency profile of a saturation transfer difference (STD) NMR experiment. The DNP experiment benefits from hyperpolarization and enables observation of all frequencies in a single, rapid experiment. Based on these merits, it is an interesting alternative to the widely used STD experiment for identification of protein-ligand interactions. PMID:26315550

  13. Siderophore-promoted dissolution of smectite by fluorescent Pseudomonas.

    PubMed

    Ferret, Claire; Sterckeman, Thibault; Cornu, Jean-Yves; Gangloff, Sophie; Schalk, Isabelle J; Geoffroy, Valérie A

    2014-10-01

    Siderophores are organic chelators produced by microorganisms to fulfil their iron requirements. Siderophore-promoted dissolution of iron-bearing minerals has been clearly documented for some siderophores, but few studies have addressed metabolizing siderophore-producing bacteria. We investigated iron acquisition from clays by fluorescent Pseudomonads, bacteria that are ubiquitous in the environment. We focused on the interactions between smectite and Pseudomonas aeruginosa, a bacterium producing two structurally different siderophores: pyoverdine and pyochelin. The presence of smectite in iron-limited growth media promoted planktonic growth of P. aeruginosa and biofilm surrounding the smectite aggregates. Chemical analysis of the culture media indicated increases in the dissolved silicon, iron and aluminium concentrations following smectite supplementation. The use of P. aeruginosa mutants unable to produce either one or both of the two siderophores indicated that pyoverdine, the siderophore with the higher affinity for iron, was involved in iron and aluminium solubilization by the wild-type strain. However, in the absence of pyoverdine, pyochelin was also able to solubilize iron but with a twofold lower efficiency. In conclusion, pyoverdine and pyochelin, two structurally different siderophores, can solubilize structural iron from smectite and thereby make it available for bacterial growth. PMID:25646536

  14. Silver nanoparticle dissolution in the presence of ligands and of hydrogen peroxide.

    PubMed

    Sigg, Laura; Lindauer, Ursula

    2015-11-01

    Dissolution of silver nanoparticles (AgNP with carbonate or citrate coating, total Ag 1-5 μM) was examined in the presence of the ligands cysteine, chloride and fulvic acids and of the oxidant hydrogen peroxide (H2O2) at low concentrations at pH 7.5. Dissolved Ag was separated from AgNP by ultrafiltration. Cysteine in the concentration range 0.2-5 μM resulted in an initial increase of dissolved Ag within few hours. Chloride (up to 0.1 mM) and fulvic acids (up to 15 mg L(-1)) had little effect on the dissolution of AgNP within hours to days. In contrast, very rapid dissolution within 1-2 h of both carbonate and citrate coated AgNP was observed in the presence of H2O2 in the concentration range 0.1-10 μM, under dark or light conditions. The high efficiency of H2O2 in dissolving AgNP is likely to be of importance in toxic effects of AgNP to algae, as H2O2 is produced and released into solution by algae. PMID:26310977

  15. Evidence for ligand hydrolysis and Fe(III) reduction in the dissolution of goethite by desferrioxamine-B

    NASA Astrophysics Data System (ADS)

    Simanova, Anna A.; Persson, Per; Loring, John S.

    2010-12-01

    Desferrioxamine-B (DFOB) is a bacterial trihydroxamate siderophore and probably the most studied to date. However, the manner in which DFOB adsorbs at mineral surfaces and promotes dissolution is still under discussion. Here we investigated the adsorption and dissolution reactions in the goethite-DFOB system using both in situ infrared spectroscopic and quantitative analytical methods. Experiments were carried out at a total DFOB concentration of 1 μmol/m 2, at pH 6, and in the absence of visible light. Our infrared spectroscopic results indicated that the adsorption of DFOB was nearly complete after a 4-h reaction time. In an attempt to determine the coordination mode at the goethite surface, we compared the spectrum of adsorbed DFOB after a 4-h reaction time to the spectra of model aqueous species. However, this approach proved too simplistic in the case of such a complex ligand as DFOB, and we suggest that a more detailed investigation (IR in D 2O, EXAFS of adsorbed model complexes) is needed to elucidate the structure of the adsorbed siderophore. Between a 4-h and 4-day reaction time, we observed the growth of carboxylate stretching bands at 1548 and 1404 cm -1, which are indicators of DFOB hydrolysis. Acetate, a product of DFOB hydrolysis at its terminal hydroxamate group, was quantified by ion chromatography. Its rate of formation was linear and nearly the same as the rate of Fe(III) dissolution. The larger hydrolysis product, a hydroxylamine fragment, was not detected by LC-MS. However, a signal due to the oxidized form of this fragment, a nitroso compound, was found to increase linearly with time, which is an indirect indication for Fe(III) reduction. Based on these findings, we propose that DFOB undergoes metal-enhanced hydrolysis at the mineral surface followed by the reduction of surface Fe(III). While Fe(II) was not detected in solution, this is likely because it remains adsorbed at the goethite surface or becomes buried in the goethite crystal by

  16. Dissolution of Uranium-Bearing Minerals and Mobilization of Uranium by Organic Ligands in a Biologically Reduced Sediment

    SciTech Connect

    Luo, Wensui; Gu, Baohua

    2011-01-01

    The stability and mobility of uranium (U) is a concern following its reductive precipitation or immobilization by techniques such as bioremediation at contaminated sites. In this study, the influences of complexing organic ligands such as citrate and ethylenediaminetetraacetate (EDTA) on the mobilization of U were investigated in both batch and column flow systems using a contaminated and bioreduced sediment. Results indicate that both reduced U(IV) and oxidized U(VI) in the sediment can be effectively mobilized with the addition of EDTA or citrate under anaerobic conditions. The dissolution and mobilization of U appear to be correlated to the dissolution of iron (Fe)- or aluminum (Al)-bearing minerals, with EDTA being more effective (with R2 0.89) than citrate (R2 <0.60) in dissolving these minerals. The column flow experiments confirm that U, Fe, and Al can be mobilized by these ligands under anoxic conditions, although the cumulative amounts of U removal constituted ~0.1% of total U present in this sediment following a limited period of leaching. This study concludes that the presence of complexing organic ligands may pose a long-term concern by slowly dissolving U-bearing minerals and mobilizing U even under a strict anaerobic environment.

  17. Oxidative Stress Promotes Ligand-independent and Enhanced Ligand-dependent Tumor Necrosis Factor Receptor Signaling*

    PubMed Central

    Ozsoy, Hatice Z.; Sivasubramanian, Natarajan; Wieder, Eric D.; Pedersen, Steen; Mann, Douglas L.

    2008-01-01

    Tumor necrosis factor (TNF) receptor 1 (TNFR1, p55) and 2 (TNFR2, p75) are characterized by several cysteine-rich modules in the extracellular domain, raising the possibility that redox-induced modifications of these cysteine residues might alter TNFR function. To test this possibility, we examined fluorescence resonance energy transfer (FRET) in 293T cells transfected with CFP- and YFP-tagged TNFRs exposed to the thiol oxidant diamide. Treatment with high concentrations of diamide (1 mm) resulted in an increase in the FRET signal that was sensitive to inhibition with the reducing agent dithiothreitol, suggesting that oxidative stress resulted in TNFR self-association. Treatment of cells with low concentrations of diamide (1 μm) that was not sufficient to provoke TNFR self-association resulted in increased TNF-induced FRET signals relative to the untreated cells, suggesting that oxidative stress enhanced ligand-dependent TNFR signaling. Similar findings were obtained when the TNFR1- and TNFR2-transfected cells were pretreated with a cell-impermeable oxidase, DsbA, that catalyzes disulfide bond formation between thiol groups on cysteine residues. The changes in TNFR self-association were functionally significant, because pretreating the HeLa cells and 293T cells resulted in increased TNF-induced NF-κB activation and TNF-induced expression of IκB and syndecan-4 mRNA levels. Although pretreatment with DsbA did not result in an increase in TNF binding to TNFRs, it resulted in increased TNF-induced activation of NF-κB, consistent with an allosteric modification of the TNFRs. Taken together, these results suggest that oxidative stress promotes TNFR receptor self-interaction and ligand-independent and enhanced ligand-dependent TNF signaling. PMID:18544535

  18. Siderophore Promoted Dissolution of a Series of Mn-Substituted Goethites

    NASA Astrophysics Data System (ADS)

    Holmstrom, S. J.; Sposito, G.

    2005-12-01

    The presence of organic ligands, like siderophores, can strongly influence mineral dissolution. Recent research suggests that at least some siderophores enhance mineral dissolution by formation of surface complexes with Fe and Mn. The impact of biogeochemical weathering caused by exudates of plants, fungi and bacteria containing siderophores has been discussed. We have studied the dissolution kinetics of Mn-substituted goethites (mol % Mn < 11) in the presences of 80 μM desferrioxamine B (DFO-B), a common and well-studied hydroxamate siderophore that has been identified in both terrestrial and marine environments and which forms very stable 1:1 complexes with Fe(III) or Mn(III). (The stability constants at I = 0.1 are 1030.6 and 1028.3, respectively.) A series of Mn-substituted goethites (α-MnxFe1-xOOH) were synthesized from ferrihydrite in the presence of Mn(II) in alkaline media. The Fe(III) in octahedral positions in the mineral structure was partially replaced by Mn, which was confirmed visually by the change to darker color when the content of Mn increased and proved by infra-red spectroscopy and X-ray diffraction studies of the samples. Substitution of Fe in the goethite by Mn caused a change in the cell dimensions. The calculated unit cell edge lengths a and c decreased, while b increased, for the Mn-goethites compared to pure goethite. The difference of the unit cell parameters between the pure goethite and the Mn-substituted goethites increased with increased Mn content, providing further confirmation that Fe had been substituted by Mn incorporated into the goethite structure. X-ray absorption near-edge structure spectroscopy analysis of the Mn-substituted goethites showed that the oxidation state of Mn in the samples was, as expected, Mn(III), even when Mn-goethites were prepared from Mn(II) solutions. Both SEM and TEM micrographs showed that the Mn-substituted goethite crystals had the same acicular shape as pure goethite. The specific surface area

  19. The temperature dependence of bytownite feldspar dissolution in neutral aqueous solutions of inorganic and organic ligands at low temperature (5-35 deg C)

    SciTech Connect

    Welch, Susan A.; Ullman, William J.

    2000-06-15

    The temperature dependence of silica release from bytownite, a Ca,Al-rich feldspar, was determined in solutions of inorganic and organic ligands at neutral pH from 5 deg C to 35 deg C. The apparent activation energy of dissolution in the inorganic (distilled water and KNO3) solutions was approximately 10 Kcal/mole. The rates and temperature dependence in acetate solutions was indistinguishable from the inorganic solutions. In contrast, both oxalate and gluconate, ligands that form strong complexes with Al in solution and presumably with Al at the mineral surface, enhanced the dissolution rates relative to the inorganic controls and had a significantly lower apparent activation energy consistent with a catalytic effect on the dissolution process.

  20. Ursodeoxycholic acid impairs atherogenesis and promotes plaque regression by cholesterol crystal dissolution in mice.

    PubMed

    Bode, Niklas; Grebe, Alena; Kerksiek, Anja; Lütjohann, Dieter; Werner, Nikos; Nickenig, Georg; Latz, Eicke; Zimmer, Sebastian

    2016-09-01

    Atherosclerosis is a chronic inflammatory disease driven primarily by a continuous retention of cholesterol within the subendothelial space where it precipitates to form cholesterol crystals (CC). These CC trigger a complex inflammatory response through activation of the NLRP3 inflammasome and promote lesion development. Here we examined whether increasing cholesterol solubility with ursodeoxycholic acid (UDCA) affects vascular CC formation and ultimately atherosclerotic lesion development. UDCA mediated intracellular CC dissolution in macrophages and reduced IL-1β production. In ApoE(-/-) mice, UDCA treatment not only impaired atherosclerotic plaque development but also mediated regression of established vascular lesions. Importantly, mice treated with UDCA had decreased CC-depositions in atherosclerotic plaques compared to controls. Together, our data demonstrate that UDCA impaired CC and NLRP3 dependent inflammation by increasing cholesterol solubility and diminished atherosclerosis in mice. PMID:27416761

  1. Characterization and dissolution properties of ruthenium oxides.

    PubMed

    Luxton, Todd P; Eick, Matthew J; Scheckel, Kirk G

    2011-07-01

    Ruthenium oxides (RuO(2)·1·10H(2)O and RuO(2)) have been synthesized by forced hydrolysis and oxidation of ruthenium chloride. The resulting materials were extensively characterized to determine the crystallinity, surface area, and ruthenium oxidation state. Surface charging experiments indicate a large quantity of reactive functional groups for both materials and a decrease in the acidity of the surface functional groups with crystallization of the hydrous oxide. Dissolution studies conducted in acidic and basic pH environments indicate Ru-oxides are insoluble in 0.1 M HCl and slightly soluble in 0.1 M NaOH. Oxalate and ascorbate (5 mM) promoted dissolution of RuO(2)·1·10H(2)O demonstrated an increase in dissolution rates with decreasing pH and increasing ligand surface coverage. XPS analysis of the RuO(2)·1·10H(2)O surface after ligand promoted dissolution revealed the reduction of Ru(IV) to Ru(III) indicating that both ascorbate and oxalate reductively dissolve RuO(2)·1·10H(2)O. Dissolution experiments with RuO(2) resulted in dissolution only for 5 mM oxalate at pH 3. Dissolution rates calculated for RuO(2)·1·10H(2)O and RuO(2) are compared with previously published dissolution rates for iron oxides, demonstrating an order of magnitude decrease in the oxalate and ascorbate promoted dissolution. PMID:21511266

  2. Intracrystalline Proteins Promote Dissolution of Urinary Calcium Oxalate Crystals in Cultured Renal Epithelial Cells

    NASA Astrophysics Data System (ADS)

    Grover, Phulwinder K.; Thurgood, Lauren A.; Fleming, David E.; van Bronswijk, Wilhelm; Ryall, Rosemary L.

    2007-04-01

    We have proposed that internalized calcium oxalate (CaOx) crystals containing intracrystalline proteins would be vulnerable to intracellular dissolution. The aims of this study were (1) to measure non-uniform strain and crystallite size in CaOx monohydrate (COM) crystals containing increasing amounts of intracrystalline crystal matrix extract (CME) and (2) to compare the rates of crystal dissolution in Madin-Darby canine kidney (MDCKII) cells. CME was isolated by demineralization of COM crystals generated from human urine. Cold and 14C-oxalate-labelled COM crystals were precipitated from ultrafiltered urine containing CME at final concentrations of 0-5mg/L. Non-uniform strain and crystallite size were determined using synchrotron X-ray diffraction with Rietveld whole-pattern peak fitting and profile analysis, and the protein content of the crystals was analyzed using SDS-PAGE and Western blotting for prothrombin fragment 1. Radiolabeled crystals were added to MDCKII cells and dissolution was expressed as radioactive label released into the medium relative to that in the crystals at zero time. Non-uniform strain increased and crystallite size decreased proportionally with rising CME concentration, reaching saturation between approximately 1 and 5 mg/L, and demonstrating unequivocally the inclusion of increasing quantities of proteins in the crystals. This was confirmed by SDS-PAGE and Western blotting. Crystal dissolution also followed saturation kinetics. These findings were confirmed by field emission scanning electron microscopy (FESEM), which showed that the degree of crystal degradation increased relative to CME concentration. We conclude that intracrystalline proteins enhance intracellular dissolution of CaOx crystals and thus may provide a natural defense against stone pathogenesis.

  3. Ligand-Promoted Meta-C-H Arylation of Anilines, Phenols, and Heterocycles.

    PubMed

    Wang, Peng; Farmer, Marcus E; Huo, Xing; Jain, Pankaj; Shen, Peng-Xiang; Ishoey, Mette; Bradner, James E; Wisniewski, Steven R; Eastgate, Martin D; Yu, Jin-Quan

    2016-07-27

    Here we report the development of a versatile 3-acetylamino-2-hydroxypyridine class of ligands that promote meta-C-H arylation of anilines, heterocyclic aromatic amines, phenols, and 2-benzyl heterocycles using norbornene as a transient mediator. More than 120 examples are presented, demonstrating this ligand scaffold enables a wide substrate and coupling partner scope. Meta-C-H arylation with heterocyclic aryl iodides as coupling partners is also realized for the first time using this ligand. The utility for this transformation for drug discovery is showcased by allowing the meta-C-H arylation of a lenalidomide derivative. The first steps toward a silver-free protocol for this reaction are also demonstrated. PMID:27384126

  4. The effect of organic acids on plagioclase dissolution rates and stoichiometry

    NASA Astrophysics Data System (ADS)

    Welch, Susan A.; Ullman, William J.

    1993-06-01

    The rates of plagioclase dissolution in solutions containing organic acids are up to ten times greater than the rates determined in solutions containing inorganic acids at the same acidity. Initial rates of dissolution are poorly reproduced in replicate experiments. After a day, however, the rates of plagioclase dissolution calculated from the rates of silicon release are reproducible and constant for up to nineteen days. Steady-state rates of dissolution are highest (up to 1.3 × 10 -8 mol/m 2/sec) in acidic solutions (pH ≈ 3) and decrease (to 1 × 10 -11 mol/m 2/sec) as acidity decreases toward neutral pH. The polyfunctional acids, oxalate, citrate, succinate, pyruvate, and 2-ketoglutarate, are the most effective at promoting dissolution. Acetate and propionate are not as effective as the other organic acids but are nonetheless more effective than solutions containing only inorganic acids. The degree of ligand-promoted enhancement of dissolution rate (rate in organic-containing solution/rate in inorganic solution at the same pH) decreases as acidity increases, indicating that the ligand-promoted dissolution mechanism becomes relatively more important as the rate of proton-promoted dissolution decreases. The stoichiometry of release to solution indicates that dissolution is selective even after the rates of dissolution become constant. As in previously published studies, Na and Ca are rapidly released from the plagioclase feldspar, leaving a surface enriched in Si and/or Al. The ratio of Al/Si released to solution indicates that the stoichiometry of the residual plagioclase surface is a function of pH and the nature of the organic ligand. The ligands which remove Al in preference to Si from the dissolving mineral surface are also those which enhance overall plagioclase dissolution rates.

  5. Ligand-Promoted C(sp(3) )-H Olefination en Route to Multi-functionalized Pyrazoles.

    PubMed

    Yang, Weibo; Ye, Shengqing; Schmidt, Yvonne; Stamos, Dean; Yu, Jin-Quan

    2016-05-17

    A Pd-catalyzed/N-heterocycle-directed C(sp(3) )-H olefination has been developed. The monoprotected amino acid ligand (MPAA) is found to significantly promote Pd-catalyzed C(sp(3) )-H olefination for the first time. Cu(OAc)2 instead of Ag(+) salts are used as the terminal oxidant. This reaction provides a useful method for the synthesis of alkylated pyrazoles. PMID:26991450

  6. Multifunctional ligands based on dihydrolipoic acid and polyethylene glycol to promote biocompatibility of quantum dots.

    PubMed

    Susumu, Kimihiro; Mei, Bing C; Mattoussi, Hedi

    2009-01-01

    One of the common strategies to promote the transfer of quantum dots (QDs) to buffer media and to couple them to biological molecules has relied on cap exchange. We have shown previously that dihydrolipoic acid (DHLA) and polyethylene glycol (PEG)-appended DHLA can effectively replace the native ligands on CdSe-ZnS QDs. Here we explain in detail the synthesis of a series of modular ligands made of the DHLA-PEG motif appended with terminal functional groups. This design allows easy coupling of biomolecules and dyes to the QDs. The ligands are modular and each is comprised of three units: a potential biological functional group (biotin, carboxylic acid and amine) and a DHLA appended at the ends of a short PEG chain, where PEG promotes water solubility and DHLA provides anchoring onto the QD. The resulting QDs are stable over a broad pH range and accessible to simple bioconjugation techniques, such as avidin-biotin binding. PMID:19265801

  7. Ligand-Promoted Borylation of C(sp(3))-H Bonds with Palladium(II) Catalysts.

    PubMed

    He, Jian; Jiang, Heng; Takise, Ryosuke; Zhu, Ru-Yi; Chen, Gang; Dai, Hui-Xiong; Dhar, T G Murali; Shi, Jun; Zhang, Hao; Cheng, Peter T W; Yu, Jin-Quan

    2016-01-11

    A quinoline-based ligand effectively promotes the palladium-catalyzed borylation of C(sp(3))-H bonds. Primary β-C(sp(3))-H bonds in carboxylic acid derivatives as well as secondary C(sp(3))-H bonds in a variety of carbocyclic rings, including cyclopropanes, cyclobutanes, cyclopentanes, cyclohexanes, and cycloheptanes, can thus be borylated. This directed borylation method complements existing iridium(I)- and rhodium(I)-catalyzed C-H borylation reactions in terms of scope and operational conditions. PMID:26611496

  8. Modeling the transport of metals with rate-limited EDTA-promoted extraction and dissolution during EDTA-flushing of copper-contaminated soils.

    PubMed

    Tsang, Daniel C W; Lo, Irene M C; Chan, K L

    2007-05-15

    EDTA-flushing of artificially contaminated soils enhanced Cu extraction but also induced mineral dissolution simultaneously. The mobilization and transport of these metal-EDTA complexes was investigated with column experiments. A quantitative transport model was proposed for simulating the experimental breakthrough curves of Cu, Fe, Al, and Ca. The rate-limited EDTA-promoted extraction and dissolution could be described by respective second-order kinetic terms, which were necessary for explaining the time-dependent depletion of extractable metals (sorbed and indigenous) in soils with continuous EDTA-flushing. Simultaneous simulation of extraction of sorbed Cu and dissolution of soil Fe, Al, and Ca is more conceptually accurate than individual modeling of each metal because the latter approach tends to overestimate the concentration of free EDTA during transport and thus underestimate the rate coefficients of EDTA-promoted dissolution. The fitted rate coefficients of Cu were about an order of magnitude larger than those of Fe and Al; these values probably reflect Cu extraction from weakly sorbed fractions and Fe and Al dissolution from amorphous oxides. The apparent retardation of Fe, Al, and Ca transport had to be taken into account by empirical determination, which was attributed to the metal lability in soils and thermodynamics of surface complexation. PMID:17547193

  9. Ligand-dependent occupancy of the retinoic acid receptor beta 2 promoter in vivo.

    PubMed Central

    Dey, A; Minucci, S; Ozato, K

    1994-01-01

    Retinoic acid (RA) activates transcription of the RA receptor beta 2 (RAR beta 2) gene in embryonal carcinoma (EC) cells. This activation involves binding of the RAR/retinoid X receptor (RAR/RXR) heterodimer to the RA-responsive element (beta RARE). Dimethyl sulfate-based genomic footprinting was performed to examine occupancy of this promoter in P19 EC cells. No footprint was detected at the beta RARE prior to RA treatment, but a footprint was detected within the first hour of RA treatment. Concomitantly, other elements in the promoter, the cyclic AMP-responsive element and tetradecanoyl phorbol acetate-like-responsive element became footprinted. Footprints at these elements were induced by RA without requiring new protein synthesis and remained for the entire duration of RA treatment but rapidly reversed upon withdrawal of RA. A delayed protection observed at the initiator site was also reversed upon RA withdrawal. The RA-inducible footprint was not due to induction of factors that bind to these element, since in vitro assays showed that these factors are present in P19 cell extracts before RA treatment. Significantly, no RA-induced footprint was observed at any of these elements in P19 cells expressing a dominant negative RXR beta, in which RXR heterodimers are unable to bind to the beta RARE. Results indicate that binding of a liganded heterodimer receptor to the beta RARE is the initial event that allows other elements to gain access to the factors. In accordance, reporter analyses showed that a mutation in the beta RARE, but not those in other elements, abrogates RA activation of the promoter. It is likely that the RAR beta 2 promoter opens in a hierarchically ordered manner, signalled by the occupancy of liganded heterodimers. Images PMID:7969156

  10. Dissolution kinetics and biodurability of tremolite particles in mimicked lung fluids: Effect of citrate and oxalate

    NASA Astrophysics Data System (ADS)

    Rozalen, Marisa; Ramos, M. Elena; Huertas, F. Javier; Fiore, Saverio; Gervilla, Fernando

    2013-11-01

    The effect of citrate and oxalate on tremolite dissolution rate was measured at 37 °C in non-stirred flow-through reactors, using modified Gamble's solutions at pH 4 (macrophages), 7.4 (interstitial fluids) and 5.5 (intermediate check point) containing 0, 0.15, 1.5 and 15 mmol L-1 of citrate or oxalate. The dissolution rates calculated from Si concentration in the output solutions without organic ligands depend on pH, decreasing when the pH increases from -13.00 (pH 4) to -13.35 (pH 7.4) mol g-1 s-1 and following a proton-promoted mechanism. The presence of both ligands enhances dissolution rates at every pH, increasing this effect when the ligand concentration increases. Citrate produces a stronger effect as a catalyst than oxalate, mainly at more acidic pHs and enhances dissolution rates until 20 times for solutions with 15 mmol L-1 citrate. However, at pH 7.4 the effect is lighter and oxalate solutions (15 mmol L-1) only enhances dissolution rates eight times respect to free organic ligand solutions. Dissolution is promoted by the attack to protons and organic ligands to the tremolite surface. Magnesium speciation in oxalate and citrate solutions shows that Mg citrate complexes are more effective than oxalate ones during the alteration of tremolite in magrophages, but this tendency is the opposite for interstitial fluids, being oxalate magnesium complexes stronger. The biodurability estimations show that the destruction of the fibers is faster in acidic conditions (macrophages) than in the neutral solutions (interstitial fluid). At pH 4, both ligands oxalate and citrate reduce the residence time of the fibers with respect to that calculated in absence of ligands. Nevertheless, at pH 7.4 the presence of ligands does not reduce significantly the lifetime of the fibers.

  11. Blockade of Nogo receptor ligands promotes functional regeneration of sensory axons after dorsal root crush.

    PubMed

    Harvey, Pamela A; Lee, Daniel H S; Qian, Fang; Weinreb, Paul H; Frank, Eric

    2009-05-13

    A major impediment for regeneration of axons within the CNS is the presence of multiple inhibitory factors associated with myelin. Three of these factors bind to the Nogo receptor, NgR, which is expressed on axons. Administration of exogenous blockers of NgR or NgR ligands promotes the regeneration of descending axonal projections after spinal cord hemisection. A more detailed analysis of CNS regeneration can be made by examining the growth of specific classes of sensory axons into the spinal cord after dorsal root crush injury. In this study, we assessed whether administration of a soluble peptide fragment of the NgR (sNgR) that binds to and blocks all three NgR ligands can promote regeneration after brachial dorsal root crush in adult rats. Intraventricular infusion of sNgR for 1 month results in extensive regrowth of myelinated sensory axons into the white and gray matter of the dorsal spinal cord, but unmyelinated sensory afferents do not regenerate. In concert with the anatomical growth of sensory axons into the cord, there is a gradual restoration of synaptic function in the denervated region, as revealed by extracellular microelectrode recordings from the spinal gray matter in response to stimulation of peripheral nerves. These positive synaptic responses are correlated with substantial improvements in use of the forelimb, as assessed by paw preference, paw withdrawal to tactile stimuli and the ability to grasp. These results suggest that sNgR may be a potential therapy for restoring sensory function after injuries to sensory roots. PMID:19439606

  12. GM1485, a nonimmunosuppressive immunophilin ligand, promotes neurofunctional improvement and neural regeneration following stroke.

    PubMed

    Ducruet, Andrew F; DeRosa, Peter A; Zacharia, Brad E; Sosunov, Sergey A; Connolly, E Sander; Weinstein, David E

    2012-07-01

    Stroke is the leading cause of disability in the industrialized world, and the development of pharmacologic strategies to promote poststroke recovery is of paramount importance. GM1485, a nonimmunosuppressive immunophilin ligand, promotes regeneration of multiple cell types following injury. In the present study, we evaluated the effect of GM1485 treatment on functional recovery and neurogenesis following rat stroke. Transient cerebral ischemia was induced in rats receiving daily GM1485 (5 mg/kg) beginning 24 hr postischemia and continuing for a total of 6 weeks. Neurological function was evaluated over this period using a battery of neurobehavioral tests, and immunostaining for stem-cell markers was performed following animal sacrifice. An in vitro model of oxidative stress was also employed to evaluate the ability of GM1485 to mediate stem-cell-like induction and plasticity. GM1485-treated rats demonstrated improved neurological function as well as increased Sox2(+) cells in the ipsilateral SVZ and striatum relative to vehicle-treated rats. Additionally, GM1485-treated fibroblasts subjected to oxidative stress were reprogrammed to a stem-cell-like phenotype and were able to differentiate down a neuronal lineage. These data demonstrate that GM1485 administration improves neurological function and is consistent with an upregulation of endogenous neurogenesis following stroke in rats. Further experiments are necessary to characterize the molecular pathways involved in these processes. PMID:22431363

  13. Formation and dissolution of twin ZnO nanostructures promoted by water and control over their emitting properties.

    PubMed

    Distaso, Monica; Mačković, Mirza; Spiecker, Erdmann; Peukert, Wolfgang

    2014-06-23

    By using ZnO as a model system, the formation of twinned nanostructures has been investigated under microwave irradiation, exploiting experimental conditions ranging from purely solvothermal when N,N-dimethylformamide was used, to purely hydrothermal when water was the solvent. A progressive increase in size, elongation and roughness of the surface was observed with increasing water content in the solvent mixture. Particular attention was paid to the reactivity of the ZnO surfaces towards dissolution. Our results show that the formation of twinned nanorods is a dynamic process and that the coupling interphase itself is highly reactive. Consequently, the twinned rods undergo a number of complex dissolution processes that are responsible for the appearance of a wide distribution of defects either on the surface or inside the structure. Poly(N-vinyl pyrrolidone) influences the photoluminescent properties of the as-synthesised materials and allows control of the ratio of the intensity of the UV and visible emission. PMID:24828278

  14. A shed NKG2D ligand that promotes natural killer cell activation and tumor rejection

    PubMed Central

    Deng, Weiwen; Gowen, Benjamin G.; Zhang, Li; Wang, Lin; Lau, Stephanie; Iannello, Alexandre; Xu, Jianfeng; Rovis, Tihana L.; Xiong, Na; Raulet, David H.

    2016-01-01

    Immune cells, including natural killer (NK) cells, recognize transformed cells and eliminate them in a process termed immunosurveillance. It is thought that tumor cells evade immunosurveillance by shedding membrane ligands that bind to the NKG2D activating receptor on NK cells and/or T cells, and desensitize these cells. In contrast, we show that in mice, shedding of MULT1, a high affinity NKG2D ligand, causes NK cell activation and tumor rejection. Recombinant soluble MULT1 stimulated tumor rejection in mice. Soluble MULT1 functions, at least in part, by competitively reversing a global desensitization of NK cells imposed by engagement of membrane NKG2D ligands on tumor-associated cells, such as myeloid cells. The results overturn conventional wisdom that soluble ligands are inhibitory, and suggest a new approach for cancer immunotherapy. PMID:25745066

  15. Atmospheric Dissolved Iron Depostiion to the Global Oceans: Effects of Oxalate-Promoted Fe Dissolution, Photochemical Redox Cycling, and Dust Mineralogy

    NASA Technical Reports Server (NTRS)

    Johnson, M. S.; Meskhidze, N.

    2013-01-01

    Mineral dust deposition is suggested to be a significant atmospheric supply pathway of bioavailable iron (Fe) to Fe-depleted surface oceans. In this study, mineral dust and dissolved Fe (Fed) deposition rates are predicted for March 2009 to February 2010 using the 3-D chemical transport model GEOS-Chem implemented with a comprehensive dust-Fe dissolution scheme. The model simulates Fed production during the atmospheric transport of mineral dust taking into account inorganic and organic (oxalate)-promoted Fe dissolution processes, photochemical redox cycling between ferric (Fe(III)) and ferrous (Fe(II)) forms of Fe, dissolution of three different Fe-containing minerals (hematite, goethite, and aluminosilicates), and detailed mineralogy of windblown dust from the major desert regions. Our calculations suggest that during the yearlong simulation is approximately 0.26 Tg (1 Tg = 1012 g) of Fed was deposited to global oceanic regions. Compared to simulations only taking into account proton-promoted Fe dissolution, the addition of oxalate to the dust-Fe mobilization scheme increased total annual model-predicted Fed deposition to global oceanic regions by approximately 75%. The implementation of Fe(II)/Fe(III) photochemical redox cycling in the model allows for the distinction between different oxidation states of deposited Fed. Our calculations suggest that during the daytime, large fractions of Fed deposited to the global oceans is likely to be in Fe(II) form, while nocturnal fluxes of Fed are largely in Fe(III) form. Model simulations also show that atmospheric fluxes of Fed can be strongly influenced by the mineralogy of Fe-containing compounds. This study shows that Fed deposition to the oceans is controlled by total dust-Fe mass concentrations, mineralogy, the surface area of dust particles, atmospheric chemical composition, cloud processing, and meteorological parameters and exhibits complex and spatiotemporally variable patterns. Our study suggests that the

  16. The effects of organic acids on the dissolution of silicate minerals: A case study of oxalate catalysis of kaolinite dissolution

    NASA Astrophysics Data System (ADS)

    Cama, Jordi; Ganor, Jiwchar

    2006-05-01

    Most studies agree that the dissolution rate of aluminosilicates in the presence of oxalic and other simple carboxylic acids is faster than the rate with non-organic acid under the same pH. However, the mechanisms by which organic ligands enhance the dissolution of minerals are in debate. The main goal of this paper was to study the mechanism that controls the dissolution rate of kaolinite in the presence of oxalate under far from equilibrium conditions (-29 < Δ Gr < -18 kcal mol -1). Two types of experiments were performed: non-stirred flow-through dissolution experiments and batch type adsorption isotherms. All the experiments were conducted at pH 2.5-3.5 in a thermostatic water-bath held at a constant temperature of 25.0, 50.0 or 70.0 ± 0.1 °C. Kaolinite dissolution rates were obtained based on the release of silicon and aluminum at steady state. The results show good agreement between these two estimates of kaolinite dissolution rate. At constant temperature, there is a general trend of increase in the overall dissolution rate as a function of the total concentration of oxalate in solution. The overall kaolinite dissolution rates in the presence of oxalate was up to 30 times faster than the dissolution rate of kaolinite at the same temperature and pH without oxalate as was observed in our previous study. Therefore, these rate differences are related to differences in oxalate and aluminum concentrations. Within the experimental variability, the oxalate adsorption at 25, 50, and 70 °C showed the same dependence on the sum of the activities of oxalate and bioxalate in solution. The change of oxalate concentration on the kaolinite surface ( Cs,ox) as a function of the sum of the activities of the oxalate and bioxalate in solution may be described by the general adsorption isotherm: C=6.1×10-7·{64·a}/{1+64·a}. The possible effect of oxalate on the proton-promoted dissolution rate was examined by comparing the results of the present study to literature

  17. TSPO PIGA Ligands Promote Neurosteroidogenesis and Human Astrocyte Well-Being

    PubMed Central

    Da Pozzo, Eleonora; Giacomelli, Chiara; Costa, Barbara; Cavallini, Chiara; Taliani, Sabrina; Barresi, Elisabetta; Da Settimo, Federico; Martini, Claudia

    2016-01-01

    The steroidogenic 18 kDa translocator protein (TSPO) is an emerging, attractive therapeutic tool for several pathological conditions of the nervous system. Here, 13 high affinity TSPO ligands belonging to our previously described N,N-dialkyl-2-phenylindol-3-ylglyoxylamide (PIGA) class were evaluated for their potential ability to affect the cellular Oxidative Metabolism Activity/Proliferation index, which is used as a measure of astrocyte well-being. The most active PIGA ligands were also assessed for steroidogenic activity in terms of pregnenolone production, and the values were related to the metabolic index in rat and human models. The results showed a positive correlation between the increase in the Oxidative Metabolism Activity/Proliferation index and the pharmacologically induced stimulation of steroidogenesis. The specific involvement of steroid molecules in mediating the metabolic effects of the PIGA ligands was demonstrated using aminoglutethimide, a specific inhibitor of the first step of steroid biosynthesis. The most promising steroidogenic PIGA ligands were the 2-naphthyl derivatives that showed a long residence time to the target, in agreement with our previous data. In conclusion, TSPO ligand-induced neurosteroidogenesis was involved in astrocyte well-being. PMID:27367681

  18. Anti-idiotypic antibody to an anti-alprenolol monoclonal antibody: promotion of ligand binding to the idiotype

    SciTech Connect

    Sawutz, G.; Homcy, C.J.

    1986-03-01

    The authors previously described the production of four monoclonal antibodies to the beta-adrenergic receptor antagonist alprenolol. One of these antibodies, 5B7 (IgG/sub 2a/k), was used to generate polyclonal anti-idiotypic antisera in rabbits. In contrast to the predicted results, the anti-idiotypic antisera (R-9) promoted (/sup 125/I)-CYP binding to the monoclonal antibody 5B7. In the presence of R-9 antisera (1:300 dilution), the binding affinity improved with the dissociation constant decreasing 100-fold from 10nM to 0.1nM. This effect could not be reproduced with pre-immune, rabbit anti-mouse, or antiidiotypic antisera generated to monoclonal antibodies of different specificity. Furthermore, R-9 alone did not bind ligand. The R-9 IgG fraction was isolated by DEAE-cellulose chromatography then adsorbed to a 5B7-immunoaffinity resin and eluted with 0.5 M NaCl. This yielded a fraction with enhanced binding activity. F(ab) fragments of 5B7 and R-9 produced the same effect indicating that polyvalency was not necessary for the enhanced ligand binding. Finally, the ligand alprenolol promoted the binding of (/sup 125/I)-5B7 to %-9 as assessed by fractionating the resulting soluble complex by size exclusion chromatography on a TSK-3000 HPLC column. These results demonstrate that anti-idiotypic antibodies can be generated which will promote the binding of antigen to the original idiotype.

  19. ErbB1 dimerization is promoted by domain co-confinement and stabilized by ligand-binding

    PubMed Central

    Low-Nam, Shalini T.; Lidke, Keith A.; Cutler, Patrick J.; Roovers, Rob C.; van Bergen en Henegouwen, Paul M.P.; Wilson, Bridget S.; Lidke, Diane S.

    2011-01-01

    The extent to which ligand occupancy and dimerization contribute to erbB1 signaling is controversial. To examine this, we utilized two-color Quantum Dot tracking for visualization of erbB1 homodimerization and quantification of the dimer off rate (koff) on living cells. Kinetic parameters were extracted using a 3-state Hidden Markov Model to identify transition rates between free, co-confined, and dimerized states. We report that dimers composed of 2 ligand-bound receptors are long-lived and their koff is independent of kinase activity. By comparison, unliganded dimers have >4-fold faster koff. Transient co-confinement of receptors promotes repeated encounters and enhances dimer formation. Mobility decreases >6-fold when ligand-bound receptors dimerize. Blockade of erbB1 kinase activity or disruption of actin networks results in faster diffusion of receptor dimers. These results implicate both signal propagation and the cortical cytoskeleton in reduced mobility of signaling-competent erbB1 dimers. PMID:22020299

  20. β3 Integrin Promotes Long-Lasting Activation and Polarization of Vascular Endothelial Growth Factor Receptor 2 by Immobilized Ligand

    PubMed Central

    Ravelli, Cosetta; Grillo, Elisabetta; Corsini, Michela; Coltrini, Daniela

    2015-01-01

    Objective— During neovessel formation, angiogenic growth factors associate with the extracellular matrix. These immobilized factors represent a persistent stimulus for the otherwise quiescent endothelial cells (ECs), driving directional EC migration and proliferation and leading to new blood vessel growth. Vascular endothelial growth factor receptor 2 (VEGFR2) is the main mediator of angiogenesis. Although VEGFR2 signaling has been deeply characterized, little is known about its subcellular localization during neovessel formation. Aim of this study was the characterization and molecular determinants of activated VEGFR2 localization in ECs during neovessel formation in response to matrix-immobilized ligand. Approach and Results— Here we demonstrate that ECs stimulated by extracellular matrix–associated gremlin, a noncanonical VEGFR2 ligand, are polarized and relocate the receptor in close contact with the angiogenic factor–enriched matrix both in vitro and in vivo. GM1 (monosialotetrahexosylganglioside)-positive planar lipid rafts, β3 integrin receptors, and the intracellular signaling transducers focal adhesion kinase and RhoA (Ras homolog gene family, member A) cooperate to promote VEGFR2 long-term polarization and activation. Conclusions— A ligand anchored to the extracellular matrix induces VEGFR2 polarization in ECs. Long-lasting VEGFR2 relocation is closely dependent on lipid raft integrity and activation of β3 integrin pathway. The study of the endothelial responses to immobilized growth factors may offer insights into the angiogenic process in physiological and pathological conditions, including cancer, and for a better engineering of synthetic tissue scaffolds to blend with the host vasculature. PMID:26293466

  1. Surface-promoted aggregation of amphiphilic quadruplex ligands drives their selectivity for alternative DNA structures.

    PubMed

    Laguerre, Aurélien; Chang, Yi; Pirrotta, Marc; Desbois, Nicolas; Gros, Claude P; Lesniewska, Eric; Monchaud, David

    2015-07-01

    Scientists are currently truly committed to enhance the specificity of chemotherapeutics that target DNA. To this end, sequence-specific drugs have progressively given way to structure-specific therapeutics. However, while numerous strategies have been implemented to design high-affinity candidates, strategies devoted to the design of high-selectivity ligands are still rare. Here we report on such an approach via the study of an amphiphilic compound, TEGPy, that self-assembles at a liquid/solid interface to provide nanosized objects that are stable in water. The resulting aggregates, identified through atomic force microscopy measurements, were found to disassemble upon interaction with DNA in a structure-specific manner (quadruplex- versus duplex-DNA). Our results provide a fertile ground for devising new strategies aiming at concomitantly enhancing DNA structural specificity and the water-solubility of aggregation-prone ligands. PMID:26040925

  2. Melanoma cells express ICOS ligand to promote the activation and expansion of T-regulatory cells

    PubMed Central

    Martin-Orozco, Natalia; Li, Yufeng; Wang, Yijun; Liu, Shijuan; Hwu, Patrick; Liu, Yong-Jun; Dong, Chen; Radvanyi, Laszlo

    2010-01-01

    CD4+CD25+Foxp3+ T-regulatory cells (Tregs) accumulate in tumors, however little is known about how the tumor environment influences this process. Here we show that human melanomas express ICOS-ligand (ICOS-L/B7H) that can provide costimulation through ICOS for the expansion of activated Tregs maintaining high Foxp3 and CD25 expression as well as suppressive function. Thus, ICOS-L expression by melanoma tumor cells may directly drive Treg activation and expansion in the tumor microenvironment as another mechanism of immune evasion. PMID:21098714

  3. Recovery of plutonium from HEPA filters by Ce(IV): promoted dissolution of PuO/sub 2/ and recycle of the cerium promoter

    SciTech Connect

    Scheitlin, F.M.; Bond, W.D.

    1980-05-01

    Studies carried out in this investigation included (1) electrolytic production of Ce(IV) from Ce(III), (2) leaching of refractory PuO/sub 2/ from HEPA filters with maintenance of Ce(IV) by anodic oxidation during leaching, and (3) evaluation of methods for contacting the HEPA solids with the leaching solution and for separating the solid residue from the leaching liquor. Anodic oxidation of Ce(III) was accomplished with an electric current efficiency of about 85% at current densities of 0.04 to 0.4 A/dm/sup 2/ at Pt anode. Refractory PuO/sub 2/ was dissolved by a 4.0 M HNO/sub 3/ - 0.1 M Ce(IV) solution in 1.5 h at 100/sup 0/C using stirred-contact leaching of the solids or by recirculating the leachant through a packed column of the solids. Cerium(IV) concentrations were maintained continuously by anodic oxidation throughout leaching. Dissolution times up to 10 h were required unless the HEPA media were oxidized initially in air at 300/sup 0/C to destroy carbonaceous species which consumed Ce(IV) more rapidly than it could be regenerated be anodic oxidation. Leaching solids in packed columns avoided the relatively difficult liquid-solids separation by centrifugation which was required after stirred-contact leaching; however, the solids handling difficulties remain. A flowsheet is proposed for the recovery of actinides from HEPA filters. A 4 M HNO/sub 3/ - 0.1 M Ce(IV) nitrate solution is used as the leachant and the Ce(III) is recycled to the leaching operation using bidentate solvent extraction.

  4. The Suzuki reaction in aqueous media promoted by P, N ligands.

    PubMed

    Weeden, Jason A; Huang, Rongcai; Galloway, Kathryn D; Gingrich, Phillip W; Frost, Brian J

    2011-01-01

    The synthesis and structure of palladium complexes of trisubstituted PTA derivatives, PTA(R3), are described. Water-soluble phosphine ligands 1,3,5-triaza-7-phosphaadmantane (PTA), tris(aminomethyl)phosphine trihydrobromide, tri(aminomethyl) phosphine, 3,7-dimethyl-1,5,7-triaza-3-phosphabicyclo[3,3,1]nonane (RO-PTA), 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane (DAPTA), lithium 1,3,5-triaza-7-phosphaadamantane-6-carboxylate (PTA-CO₂Li), 2,4,6-triphenyl-1,3,5-triaza-7-phosphatricyclo [3.3.1.1]decane, and 2,4,6-triphenyl-1,3,5-triaza-7-phosphatricyclo[3.3.1.1]decane were used as ligands for palladium catalyzed Suzuki reactions in aqueous media. RO-PTA in combination with palladium acetate or palladium chloride was the most active catalyst for Suzuki cross coupling of aryl bromides and phenylboronic acid at 80 °C in 1:1 water:acetonitrile. The activity of Pd(II) complexes of RO-PTA is comparable to PPh₂(m-C₆H₄SO₃Na) (TPPMS) and P(m-C₆H₄SO₃Na)₃ (TPPTS) and less active than tri(4,6-dimethyl-3-sulfonatophenyl)phosphine trisodium salt (TXPTS). Activated, deactivated, and sterically hindered aryl bromides were examined, with yields ranging from 50% to 90% in 6 h with 5% palladium precatalyst loading. X-ray crystal structures of (RO-PTA)PdCl₂, (PTA(R3))₂PdCl₂ (R = Ph, p-tert-butylC₆H₅), and PTA(R3) (R = p-tert-butylC₆H₅) are reported. PMID:21788930

  5. Kit ligand promotes the transition from primordial to primary follicles after in vitro culture of ovine ovarian tissue.

    PubMed

    Cavalcante, A Y P; Gouveia, B B; Barberino, R S; Lins, T L B G; Santos, L P; Gonçalves, R J S; Celestino, J J H; Matos, M H T

    2016-08-01

    This study evaluated the effects of kit ligand (KL) on the morphology and development of ovine preantral follicles (fresh control) and after 7 days of in vitro culture in α-Minimal Essential Medium (α-MEM; control medium) or the presence of KL (1, 10, 50, 100 or 200 ng/ml). There was an increase in the percentage of primary follicles at the concentration of 100 ng/ml KL, compared with the fresh control, control medium (α-MEM) and the other KL concentrations. Follicle diameter was significantly higher than the control medium only at concentrations of 50 and 100 ng/ml KL. In conclusion, 100 ng/ml KL promoted the transition from primordial to primary follicles (follicular activation) after in vitro culture of ovine ovarian tissue. PMID:26503557

  6. Elevated autocrine chemokine ligand 18 expression promotes oral cancer cell growth and invasion via Akt activation

    PubMed Central

    Hong, Yun; Wu, Tong; Chen, Xiaobing; Xia, Juan; Cheng, Bin

    2016-01-01

    Chemokine (C-C motif) ligand 18 (CCL18) has been implicated in the pathogenesis and progression of various cancers; however, in oral squamous cell carcinoma (OSCC), the role of CCL18 is unknown. In this study, we found that CCL18 was overexpressed in primary OSCC tissues and was associated with an advanced clinical stage. CCL18 was found in both the cytoplasm and cell membrane of OSCC cells and was predominantly produced by cancer epithelial cells, as opposed to tumor-infiltrating macrophages. In vitro studies indicated that the effects of endogenous CCL18 on OSCC cell growth, migration, and invasion could be blocked by treatment with a neutralizing anti-CCL18 antibody or CCL18 knockdown, while exogenous recombinant CCL18 (rCCL18) rescued those effects. Akt was activated in rCCL18-treated OSCC cells, while LY294002, a pan-PI3K inhibitor, abolished both endogenous and exogenous CCL18-induced OSCC cell invasion. In vivo, LY294002 treatment attenuated rCCL18-induced OSCC cell growth. Our results indicate that CCL18 acts in an autocrine manner via Akt activation to stimulate OSCC cell growth and invasion during OSCC progression. They also provide a potential therapeutic target for the treatment of oral cancer. PMID:26919103

  7. Dissolution rates of phyllosilicates as a function of bacterial metabolic diversity

    NASA Astrophysics Data System (ADS)

    Balland, C.; Poszwa, A.; Leyval, C.; Mustin, C.

    2010-10-01

    Weathering experiments using biotite and phlogopite in the presence of bacteria were conducted to better understand biotic dissolution kinetics and processes (proton- and ligand-promoted dissolution) under aerobic conditions. Miniature batch reactors (300 μl in microplate wells) were used at 24 °C for 3 days with and without bacterial strains. Abiotic experiments were performed with organic and nitric acids in order to calibrate the biotite-phlogopite chemical dissolution. An empirical model was used to fit the pH dependence for iron release rate (r Fe) considering the influence of both protons and ligands from acidic to neutral conditions (pH ranging from 3 to 7): rFe=kH(a)m+kL(aL)1 where k is the apparent rate constant, a H+ and a L are the activities of protons and ligands, and m and l are the reaction orders. For both minerals in most cases at a given pH, the iron release rates in the presence of bacteria were in good agreement with rates determined by the chemical model and could be explained by a combination of proton- and ligand-promoted processes. Bacteria affect mineral dissolution and iron release rates through the quantities and nature of the organic acids they produce. Three domains were differentiated and proposed as biochemical models of mica dissolution: (1) below pH 3, only proton-promoted dissolution occurred, (2) in weakly acidic solutions both ligand- and proton-promoted mechanisms were involved, and (3) iron immobilization occured, at pH values greater than 4 for biotite and greater than 5 for phlogopite. This model allows us to distinguish the "weathering pattern phenotypes" of strains. Bacteria that are isolated from horizons poor in carbon appear more efficient at weathering micas than bacterial strains isolated from environments rich in carbon. Moreover, our results suggest that the mineral could exert a control on the release of organic acids and the "weathering pattern phenotypes" of bacteria.

  8. CC-chemokine receptor 7 and its ligand CCL19 promote mitral valve interstitial cell migration and repair

    PubMed Central

    Wang, Xiaozhi; Wang, Liang; Miao, Liping; Zhao, Rong; Wu, Yanhu; Kong, Xiangqing

    2015-01-01

    Abstract The effect of CC-chemokine receptor 7 (CCR7) and CC-chemokine ligand 19 (CCL19) on rheumatic mitral stenosis is unknown. This study aimed to explore the roles of CCR7 and CCL19 in rheumatic mitral stenosis by measuring the expression of CCR7 and CCL19 in human mitral valves from rheumatic mitral stenosis patients. Additionally, we examined their effects on human mitral valve interstitial cells (hMVICs) proliferation, apoptosis and wound repair. CCR7 and CCL19 expression was measured in the mitral valves from rheumatic mitral stenosis patients (n = 10) and compared to normal mitral valves (n = 5). CCR7 was measured in cultured hMVICs from rheumatic mitral stenosis patients and normal donors by RT-PCR and immunofluorescence. The cells were also treated with exogenous CCL19, and the effects on wound healing, proliferation and apoptosis were assayed. In the rheumatic mitral valves, valve interstitial cells expressed CCR7, while mononuclear cells and the endothelium expressed CCL19. Healthy mitral valves did not stain positive for CCR7 or CCL19. CCR7 was also detected in cultured rheumatic hMVICs or in normal hMVICs treated with CCL19. In a wound healing experiment, wound closure rates of both rheumatic and normal hMVICs were significantly accelerated by CCL19. These effects were abrogated by a CCR7 neutralizing antibody. The CCR7/CCL19 axis did not influence the proliferation or apoptosis of hMVICs, indicating that wound healing was due to increased migration rates rather than increased proliferation. In conclusion, CCR7 and CCL19 were expressed in rheumatic mitral valves. The CCR7/CCL19 axis may regulate remodeling of rheumatic valve injury through promoting migratory ability of hMVICs. PMID:26668580

  9. Tensile force on human macrophage cells promotes osteoclastogenesis through receptor activator of nuclear factor κB ligand induction.

    PubMed

    Kao, Chia-Tze; Huang, Tsui-Hsien; Fang, Hsin-Yuan; Chen, Yi-Wen; Chien, Chien-Fang; Shie, Ming-You; Yeh, Chia-Hung

    2016-07-01

    Little is known about the effects of tensile forces on osteoclastogenesis by human monocytes in the absence of mechanosensitive cells, including osteoblasts and fibroblasts. In this study we consider the effects of tensile force on osteoclastogenesis in human monocytes. The cells were treated with receptor activator of nuclear factor κB ligand (RANKL) to promote osteoclastogenesis. Then,expression and secretion of cathepsin K were examined. RANKL and the formation of osteoclasts during the osteoclast differentiation process under continual tensile stress were evaluated by Western blot. It was also found that -100 kPa or lower induces RANKL-enhanced tartrate-resistant acid phosphatase activity in a dose-dependent manner. Furthermore, an increased tensile force raises the expression and secretion of cathepsin K elevated by RANKL, and is concurrent with the increase of TNF-receptor-associated factor 6 induction and nuclear factor κB activation. Overall, the current report demonstrates that tensile force reinforces RANKL-induced osteoclastogenesis by retarding osteoclast differentiation. The tensile force is able to modify every cell through dose-dependent in vitro RANKL-mediated osteoclastogenesis, affecting the fusion of preosteoclasts and function of osteoclasts. However, tensile force increased TNF-receptor-associated factor 6 expression. These results are in vitro findings and were obtained under a condition of tensile force. The current results help us to better understand the cellular roles of human macrophage populations in osteoclastogenesis as well as in alveolar bone remodeling when there is tensile stress. PMID:26204845

  10. Dissolution kinetics of kaolinite in acidic aqueous solutions at 25 C

    SciTech Connect

    Wieland, E.; Stumm, W. Swiss Federal Inst. of Tech., Zuerich )

    1992-09-01

    The dissolution of kaolinite is interpreted in terms of the surface complexation model. Acid/base properties of the terminal OH groups and ion exchange reactions occurring at the kaolinite surface have been investigated. A three-site model incorporating solid-solution equilibria at aluminol groups of the edge and gibbsite surfaces and at negatively charged XO groups of the siloxane surface account for the protonation of kaolinite platelets in acidic solutions. The dissolution kinetics of kaolinite at 25 C has been studied as a function of solution pH. The dissolution of kaolinite is nonstoichiometric in the pH range 2-6.5 with a preferential release of silicon. Stoichiometry of the dissolution reaction is achieved, however, in the presence of oxalate as Al-complexing ligand. The detachment of aluminium from the lattice structure of the kaolinite surface and its readsorption on distinct surface sites occur simultaneously during the dissolution process causing the experimentally observed nonstoichiometry. The proton-promoted dissolution of kaolinite occurs at the edge surface (pH < 6.5) and the gibbsite surface (pH < 4). The pH-dependence of the dissolution rate R[sub H](Si) reflects sequential protonation of terminal OH groups on both surfaces. The dissolution reaction can be interpreted as a coupled release of Al and Si with the detachment of the Al center from the surface lattice structure as the rate-limiting step. The aluminium:proton stoichiometry of the activated complex is 1:3 at the gibbsite surface and 1:1 at the edge surface.

  11. Double hydrophosphination of alkynes promoted by rhodium: the key role of an N-heterocyclic carbene ligand.

    PubMed

    Di Giuseppe, Andrea; De Luca, Roberto; Castarlenas, Ricardo; Pérez-Torrente, Jesús J; Crucianelli, Marcello; Oro, Luis A

    2016-04-25

    The regioselective double hydrophosphination of alkynes mediated by rhodium catalysts is presented. The distinctive stereoelectronic properties of the NHC ligand prevent the catalyst deactivation by diphosphine coordination thereby allowing for the closing of a productive catalytic cycle. PMID:27022648

  12. Fas ligand based immunotherapy: A potent and effective neoadjuvant with checkpoint inhibitor properties, or a systemically toxic promoter of tumor growth?

    PubMed

    Modiano, Jaime F; Bellgrau, Donald

    2016-02-01

    Fas ligand (FasL, CD95L) is a 40-kDa type II transmembrane protein that binds to Fas (CD95) receptors and promotes programmed cell death. Fas receptors are expressed at higher levels in many tumors than in normal cells; however, systemic administration of FasL or agonistic anti-Fas antibodies to mice with tumors caused lethal hepatitis. Somewhat paradoxically, elimination of Fas or FasL from tumors also leads to death induced by CD95 receptor/ligand elimination (DICE). At face value, this suggests that Fas signaling not only kills normal cells, but that it also is essential for tumor cell survival. Targeting this pathway may not only fail to kill tumors, but instead may even enhance their growth, leading some to report the demise of Fas ligand in cancer immunotherapy. But, to paraphrase Mark Twain, is this death an exaggeration? Here, we provide a careful examination of the literature exploring the merits of FasL as a novel form of cancer immunotherapy. With local administration using delivery vectors that achieve high levels of expression in the tumor environment, our results indicate that the potential for systemic toxicity is eliminated in higher mammals, and that a systemic anti-tumor response ensues, which delays or prevents progression and simultaneously attacks distant metastases. PMID:27011046

  13. Role of estrogen receptor ligand and estrogen response element sequence on interaction with chicken ovalbumin upstream promoter transcription factor (COUP-TF).

    PubMed

    Klinge, C M

    1999-11-01

    Estrogen-responsive genes are regulated by altering the balance of estrogen receptor (ER) interaction with transcription activators and inhibitors. Here we examined the role of ER ligand on ER interaction with the Chicken Ovalbumin Upstream Promoter Transcription Factor (COUP-TF) orphan nuclear receptor. COUP-TF binding to half-site estrogen response elements (EREs) was increased by the addition of estradiol (E2) -liganded ER (E2-ER), but not by ER liganded with the antiestrogens 4-hydroxytamoxifen (4-OHT-ER) or tamoxifen aziridine (TAz-ER). ER did not bind to single half-sites. Conversely, COUP-TF enhanced the ERE binding of purified E2-ER, but did not affect TAz-ER-ERE binding. In contrast, only antiestrogens enhanced direct interaction between ER and COUP-TF as assessed by GST pull-down assays. Identical results were obtained using either purified bovine or recombinant human ERalpha. Co-immunoprecipitation assays showed that ER and COUP-TF interact in extracts from MCF-7 and ERalpha-transfected MDA-MB-231 cells. Here we document that ER ligand impacts COUP-TF-ER interaction. COUP-TF interaction is mediated by the DNA binding and ligand-binding domains of ER. We suggest that changes in ER conformation induced by DNA binding reduce ER-COUP-TF interaction. Transient transfection of human MCF-7 breast cancer cells with a COUP-TFI expression vector repressed E2-induced luciferase reporter gene expression from single or multiple tandem copies of a consensus ERE. COUP-TFI stimulated 4-OHT-induced luciferase activity from a minimal ERE. Alone, COUP-TFI increased transcription from ERE half-sites or a single ERE in a sequence-dependent manner. These data provide evidence that the ERE sequence and its immediate flanking regions influence whether COUP-TF enhances, inhibits, or has no effect on ER ligand-induced ERE reporter gene expression and that COUP-TFI activates gene transcription from ERE half-sites. We suggest that COUP-TFI plays a role in mitigating estrogen

  14. EphA2 promotes cell adhesion and spreading of monocyte and monocyte/macrophage cell lines on integrin ligand-coated surfaces

    PubMed Central

    Saeki, Noritaka; Nishino, Shingo; Shimizu, Tomohiro; Ogawa, Kazushige

    2015-01-01

    Eph signaling, which arises following stimulation by ephrins, is known to induce opposite cell behaviors such as promoting and inhibiting cell adhesion as well as promoting cell-cell adhesion and repulsion by altering the organization of the actin cytoskeleton and influencing the adhesion activities of integrins. However, crosstalk between Eph/ephrin with integrin signaling has not been fully elucidated in leukocytes, including monocytes and their related cells. Using a cell attachment stripe assay, we have shown that, following stimulation with ephrin-A1, kinase-independent EphA2 promoted cell spreading/elongation as well as adhesion to integrin ligand-coated surfaces in cultured U937 (monocyte) and J774.1 (monocyte/macrophage) cells as well as sublines of these cells expressing dominant negative EphA2 that lacks most of the intracellular region. Moreover, a pull-down assay showed that dominant negative EphA2 is recruited to the β2 integrin/ICAM1 and β2 integrin/VCAM1 molecular complexes in the subline cells following stimulation with ephrin-A1-Fc. Notably, this study is the first comprehensive analysis of the effects of EphA2 receptors on integrin-mediated cell adhesion in monocytic cells. Based on these findings we propose that EphA2 promotes cell adhesion by an unknown signaling pathway that largely depends on the extracellular region of EphA2 and the activation of outside-in integrin signaling. PMID:26565750

  15. Binding of the Lactococcal Drug Dependent Transcriptional Regulator LmrR to Its Ligands and Responsive Promoter Regions

    PubMed Central

    van der Berg, Jan Pieter; Madoori, Pramod Kumar; Komarudin, Amalina Ghaisani; Thunnissen, Andy-Mark; Driessen, Arnold J. M.

    2015-01-01

    The heterodimeric ABC transporter LmrCD from Lactococcus lactis is able to extrude several different toxic compounds from the cell, fulfilling a role in the intrinsic and induced drug resistance. The expression of the lmrCD genes is regulated by the multi-drug binding repressor LmrR, which also binds to its own promoter to autoregulate its own expression. Previously, we reported the crystal structure of LmrR in the presence and absence of the drugs Hoechst 33342 and daunomycin. Analysis of the mechanism how drugs control the repressor activity of LmrR is impeded by the fact that these drugs also bind to DNA. Here we identified, using X-ray crystallography and fluorescence, that riboflavin binds into the drug binding cavity of LmrR, adopting a similar binding mode as Hoechst 33342 and daunomycin. Microscale thermophoresis was employed to quantify the binding affinity of LmrR to its responsive promoter regions and to evaluate the cognate site of LmrR in the lmrCD promoter region. Riboflavin reduces the binding affinity of LmrR for the promoter regions. Our results support a model wherein drug binding to LmrR relieves the LmrR dependent repression of the lmrCD genes. PMID:26267906

  16. Promotion

    PubMed Central

    Alam, Hasan B.

    2013-01-01

    This article gives an overview of the promotion process in an academic medical center. A description of different promotional tracks, tenure and endowed chairs, and the process of submitting an application is provided. Finally, some practical advice about developing skills and attributes that can help with academic growth and promotion is dispensed. PMID:24436683

  17. Tunable DNA cleavage activity promoted by copper(ii) ternary complexes with N-donor heterocyclic ligands.

    PubMed

    Bortolotto, T; Silva-Caldeira, P P; Pich, C T; Pereira-Maia, E C; Terenzi, H

    2016-06-01

    Several small molecules have the capacity to cleave DNA promptly at high yields, even under mild conditions. Usually, this activity has no constraints, occurring without external or user control. Here, we demonstrate that UV-light exposure can greatly enhance the DNA cleavage activity promoted by four ternary copper(ii) complexes. A remarkable photocontrolled activity was achieved, which may be interesting for chemical and biochemical applications. PMID:27168172

  18. Nicotinic acetylcholine receptors induce c-Kit ligand/Stem Cell Factor and promote stemness in an ARRB1/ β-arrestin-1 dependent manner in NSCLC

    PubMed Central

    Perumal, Deepak; Pillai, Smitha; Nguyen, Jonathan; Schaal, Courtney; Coppola, Domenico; Chellappan, Srikumar P.

    2014-01-01

    Lung cancer remains the leading cause of cancer-related deaths worldwide. β-arrestin-1 (ARRB1), a scaffolding protein involved in the desensitization of signals arising from activated G-protein-coupled receptors (GPCRs), has been shown to play a role in invasion and proliferation of cancer cells, including nicotine-induced proliferation of human non–small cell lung cancers (NSCLCs). In this study, we identified genes that are differentially regulated by nicotine in an ARRB1/β-arrestin-1 dependent manner in NSCLC cells by microarray analysis. Among the identified genes, SCF (Stem cell factor) strongly differentiated smokers from non-smokers in the Director's Challenge Set expression data and its high expression correlated with poor prognosis. SCF, a major cytokine is the ligand for the c-Kit proto-oncogene and was found to be over expressed in human lung adenocarcinomas, but not squamous cell carcinomas. Data presented here show that transcription factor E2F1 can induce SCF expression at the transcriptional level and depletion of E2F1 or ARRB1/β-arrestin-1 could not promote self-renewal of SP cells. These studies suggest that nicotine might be promoting NSCLC growth and metastasis by inducing the secretion of SCF, and raise the possibility that targeting signalling cascades that activate E2F1 might be an effective way to combat NSCLC. PMID:25401222

  19. GQ-16, a Novel Peroxisome Proliferator-activated Receptor γ (PPARγ) Ligand, Promotes Insulin Sensitization without Weight Gain

    PubMed Central

    Amato, Angélica A.; Rajagopalan, Senapathy; Lin, Jean Z.; Carvalho, Bruno M.; Figueira, Ana C. M.; Lu, Jenny; Ayers, Stephen D.; Mottin, Melina; Silveira, Rodrigo L.; Souza, Paulo C. T.; Mourão, Rosa H. V.; Saad, Mário J. A.; Togashi, Marie; Simeoni, Luiz A.; Abdalla, Dulcinéia S. P.; Skaf, Munir S.; Polikparpov, Igor; Lima, Maria C. A.; Galdino, Suely L.; Brennan, Richard G.; Baxter, John D.; Pitta, Ivan R.; Webb, Paul; Phillips, Kevin J.; Neves, Francisco A. R.

    2012-01-01

    The recent discovery that peroxisome proliferator-activated receptor γ (PPARγ) targeted anti-diabetic drugs function by inhibiting Cdk5-mediated phosphorylation of the receptor has provided a new viewpoint to evaluate and perhaps develop improved insulin-sensitizing agents. Herein we report the development of a novel thiazolidinedione that retains similar anti-diabetic efficacy as rosiglitazone in mice yet does not elicit weight gain or edema, common side effects associated with full PPARγ activation. Further characterization of this compound shows GQ-16 to be an effective inhibitor of Cdk5-mediated phosphorylation of PPARγ. The structure of GQ-16 bound to PPARγ demonstrates that the compound utilizes a binding mode distinct from other reported PPARγ ligands, although it does share some structural features with other partial agonists, such as MRL-24 and PA-082, that have similarly been reported to dissociate insulin sensitization from weight gain. Hydrogen/deuterium exchange studies reveal that GQ-16 strongly stabilizes the β-sheet region of the receptor, presumably explaining the compound's efficacy in inhibiting Cdk5-mediated phosphorylation of Ser-273. Molecular dynamics simulations suggest that the partial agonist activity of GQ-16 results from the compound's weak ability to stabilize helix 12 in its active conformation. Our results suggest that the emerging model, whereby “ideal” PPARγ-based therapeutics stabilize the β-sheet/Ser-273 region and inhibit Cdk5-mediated phosphorylation while minimally invoking adipogenesis and classical agonism, is indeed a valid framework to develop improved PPARγ modulators that retain antidiabetic actions while minimizing untoward effects. PMID:22584573

  20. Manganese Electrocatalysts with Bulky Bipyridine Ligands: Utilizing Lewis Acids To Promote Carbon Dioxide Reduction at Low Overpotentials.

    PubMed

    Sampson, Matthew D; Kubiak, Clifford P

    2016-02-01

    Earth-abundant manganese bipyridine (bpy) complexes are well-established molecular electrocatalysts for proton-coupled carbon dioxide (CO2) reduction to carbon monoxide (CO). Recently, a bulky bipyridine ligand, 6,6'-dimesityl-2,2'-bipyridine (mesbpy), was utilized to significantly lower the potential necessary to access the doubly reduced states of these manganese catalysts by eliminating their ability to dimerize after one-electron reduction. Although this Mn mesbpy catalyst binds CO2 at very low potentials, reduction of a resulting Mn(I)-COOH complex at significantly more negative potentials is required to achieve fast catalytic rates. Without reduction of Mn(I)-COOH, catalysis occurs slowly via a alternate catalytic pathway-protonation of Mn(I)-COOH to form a cationic tetracarbonyl complex. We report the use of Lewis acids, specifically Mg(2+) cations, to significantly increase the rate of catalysis (by over 10-fold) at these low overpotentials (i.e., the same potential as CO2 binding). Reduction of CO2 occurs at one of the lowest overpotentials ever reported for molecular electrocatalysts (η = 0.3-0.45 V). With Mg(2+), catalysis proceeds via a reductive disproportionation reaction of 2CO2 + 2e(-) → CO and CO3(2-). Insights into the catalytic mechanism were gained by using variable concentration cyclic voltammetry, infrared spectroelectrochemistry, and bulk electrolysis studies. The catalytic Tafel behavior (log turnover frequency vs overpotential relationship) of [Mn(mesbpy)(CO)3(MeCN)](OTf) with added Mg(2+) is compared with those of other commonly studied CO2 reduction catalysts. PMID:26745814

  1. The Receptor Guanylyl Cyclase Type D (GC-D) Ligand Uroguanylin Promotes the Acquisition of Food Preferences in Mice

    PubMed Central

    2013-01-01

    Rodents rely on olfactory stimuli to communicate information between conspecifics that is critical for health and survival. For example, rodents that detect a food odor simultaneously with the social odor carbon disulfide (CS2) will acquire a preference for that food. Disruption of the chemosensory transduction cascade in CS2-sensitive olfactory sensory neurons (OSNs) that express the receptor guanylyl cyclase type D (GC-D; GC-D+ OSNs) will prevent mice from acquiring these preferences. GC-D+ OSNs also respond to the natriuretic peptide uroguanylin, which is excreted into urine and feces. We analyzed if uroguanylin could also act as a social stimulus to promote the acquisition of food preferences. We found that feces of mice that had eaten odored food, but not unodored food, promoted a strong preference for that food in mice exposed to the feces. Olfactory exploration of uroguanylin presented with a food odor similarly produced a preference that was absent when mice were exposed to the food odor alone. Finally, the acquisition of this preference was dependent on GC-D+ OSNs, as mice lacking GC-D (Gucy2d − /− mice) showed no preference for the demonstrated food. Together with our previous findings, these results demonstrate that the diverse activators of GC-D+ OSNs elicit a common behavioral result and suggest that this specialized olfactory subsystem acts as a labeled line for a type of associative olfactory learning. PMID:23564012

  2. Arsenic Induced Phytate Exudation, and Promoted FeAsO4 Dissolution and Plant Growth in As-Hyperaccumulator Pteris vittata.

    PubMed

    Liu, Xue; Fu, Jing-Wei; Guan, Dong-Xing; Cao, Yue; Luo, Jun; Rathinasabapathi, Bala; Chen, Yanshan; Ma, Lena Q

    2016-09-01

    Arsenic hyperaccumulator Pteris vittata (PV) is efficient in taking up As and nutrients from As-contaminated soils. We evaluated the mechanisms used by PV to mobilize As and Fe by examining the impacts of As and root exudates on FeAsO4 solubilization, and As and Fe uptake in four plants: As-hyperaccumulators PV and Pteris multifida (PM), nonhyperaccumulator Pteris ensiformis (PE), and angiosperm plant tomato (Solanum lycopersicum). Phytate and oxalate were dominant in fern plants (>93%), which were 50-83, 15-42, and 0-32 mg kg(-1) phytate and 10-15, 7-26, and 4-12 mg kg(-1) oxalate for PV, PM, and PE respectively, with higher As inducing greater phytate exudation and no phytate being detected in tomato exudates. PV treated with phytate+FeAsO4 had higher As and Fe contents and larger biomass than phytate or FeAsO4 treatment, which were 340 vs 20 and 130 mg kg(-1) As in the fronds and 7900 vs 1600 and 4100 mg kg(-1) Fe in the roots. We hypothesized that As-induced phytate exudation helped PV to take up Fe and As from insoluble FeAsO4 and promoted PV growth. Our study suggests that phytate exudation may be special to fern plants, which may play an important role in enhancing As and nutrient uptake by plants, thereby increasing their efficiency in phytoremediation of As-contaminated soils. PMID:27483027

  3. Continuous plutonium dissolution apparatus

    DOEpatents

    Meyer, F.G.; Tesitor, C.N.

    1974-02-26

    This invention is concerned with continuous dissolution of metals such as plutonium. A high normality acid mixture is fed into a boiler vessel, vaporized, and subsequently condensed as a low normality acid mixture. The mixture is then conveyed to a dissolution vessel and contacted with the plutonium metal to dissolve the plutonium in the dissolution vessel, reacting therewith forming plutonium nitrate. The reaction products are then conveyed to the mixing vessel and maintained soluble by the high normality acid, with separation and removal of the desired constituent. (Official Gazette)

  4. Dissolution DNP for in vivo preclinical studies

    NASA Astrophysics Data System (ADS)

    Comment, Arnaud

    2016-03-01

    The tremendous polarization enhancement afforded by dissolution dynamic nuclear polarization (DNP) can be taken advantage of to perform preclinical in vivo molecular and metabolic imaging. Following the injection of molecules that are hyperpolarized via dissolution DNP, real-time measurements of their biodistribution and metabolic conversion can be recorded. This technology therefore provides a unique and invaluable tool for probing cellular metabolism in vivo in animal models in a noninvasive manner. It gives the opportunity to follow and evaluate disease progression and treatment response without requiring ex vivo destructive tissue assays. Although its considerable potential has now been widely recognized, hyperpolarized magnetic resonance by dissolution DNP remains a challenging method to implement for routine in vivo preclinical measurements. The aim of this article is to provide an overview of the current state-of-the-art technology for preclinical applications and the challenges that need to be addressed to promote it and allow its wider dissemination in the near future.

  5. Dissolution DNP for in vivo preclinical studies.

    PubMed

    Comment, Arnaud

    2016-03-01

    The tremendous polarization enhancement afforded by dissolution dynamic nuclear polarization (DNP) can be taken advantage of to perform preclinical in vivo molecular and metabolic imaging. Following the injection of molecules that are hyperpolarized via dissolution DNP, real-time measurements of their biodistribution and metabolic conversion can be recorded. This technology therefore provides a unique and invaluable tool for probing cellular metabolism in vivo in animal models in a noninvasive manner. It gives the opportunity to follow and evaluate disease progression and treatment response without requiring ex vivo destructive tissue assays. Although its considerable potential has now been widely recognized, hyperpolarized magnetic resonance by dissolution DNP remains a challenging method to implement for routine in vivo preclinical measurements. The aim of this article is to provide an overview of the current state-of-the-art technology for preclinical applications and the challenges that need to be addressed to promote it and allow its wider dissemination in the near future. PMID:26920829

  6. Distinctive Reactivities at Biotite Edge and Basal Planes in the Presence of Organic Ligands: Implications for Organic-Rich Geologic CO2 Sequestration.

    PubMed

    Zhang, Lijie; Jun, Young-Shin

    2015-08-18

    To better understand how scCO2-saturated brine-mineral interactions can affect safe and efficient geologic CO2 sequestration (GCS), we studied the effects of organic ligands (acetate and oxalate) on biotite dissolution and surface morphological changes. The experimental conditions were chosen to be relevant to GCS sites (95 °C and 102 atm CO2). Quantitative analyses of dissolution differences between biotite edge and basal planes were made. Acetate slightly inhibited biotite dissolution and promoted secondary precipitation. The effect of acetate was mainly pH-induced aqueous acetate speciation and the subsequent surface adsorption. Under the experimental conditions, most of acetate exists as acetic acid and adsorbs to biotite surface Si and Al sites, thereby reducing their release. However, oxalate strongly enhanced biotite dissolution and induced faster and more significant surface morphology changes by forming bidentate mononuclear surface complexes. For the first time, we show that oxalate selectively attacks edge surface sites and enhances biotite dissolution. Thus, oxalate increases the relative reactivity ratio of biotite edge surfaces to basal surfaces, while acetate does not impact this relative reactivity. This study provides new information on reactivity differences at biotite edge and basal planes in the presence of organic ligands, which has implications for safe CO2 storage in organic-rich sites. PMID:26171995

  7. HEPA filter dissolution process

    SciTech Connect

    Brewer, K.N.; Murphy, J.A.

    1992-12-31

    This invention is comprised of a process for dissolution of spent high efficiency particulate air (HEPA) filters and then combining the complexed filter solution with other radioactive wastes prior to calcining the mixed and blended waste feed. The process is an alternate to a prior method of acid leaching the spent filters which is an inefficient method of treating spent HEPA filters for disposal.

  8. Mergers, Annexations, Dissolutions

    ERIC Educational Resources Information Center

    Russo, Alexander

    2006-01-01

    Consolidations come in all shapes and sizes, including mergers, annexations and dissolutions. They do not all take place under state mandate, however. A handful of districts consolidate every year in some states like Illinois that have large numbers of small districts, many of them dual districts that serve K-8 or 9-12 in the same geographic area.…

  9. Hepa filter dissolution process

    DOEpatents

    Brewer, Ken N.; Murphy, James A.

    1994-01-01

    A process for dissolution of spent high efficiency particulate air (HEPA) filters and then combining the complexed filter solution with other radioactive wastes prior to calcining the mixed and blended waste feed. The process is an alternate to a prior method of acid leaching the spent filters which is an inefficient method of treating spent HEPA filters for disposal.

  10. HEPA filter dissolution process

    DOEpatents

    Brewer, K.N.; Murphy, J.A.

    1994-02-22

    A process is described for dissolution of spent high efficiency particulate air (HEPA) filters and then combining the complexed filter solution with other radioactive wastes prior to calcining the mixed and blended waste feed. The process is an alternate to a prior method of acid leaching the spent filters which is an inefficient method of treating spent HEPA filters for disposal. 4 figures.

  11. Plutonium oxide dissolution

    SciTech Connect

    Gray, J.H.

    1992-09-30

    Several processing options for dissolving plutonium oxide (PuO[sub 2]) from high-fired materials have been studied. The scoping studies performed on these options were focused on PuO[sub 2] typically generated by burning plutonium metal and PuO[sub 2] produced during incineration of alpha contaminated waste. At least two processing options remain applicable for dissolving high-fired PuO[sub 2] in canyon dissolvers. The options involve solid solution formation of PuO[sub 2] With uranium oxide (UO[sub 2]) and alloying incinerator ash with aluminum. An oxidative dissolution process involving nitric acid solutions containing a strong oxidizing agent, such as cerium (IV), was neither proven nor rejected. This uncertainty was due to difficulty in regenerating cerium (IV) ions during dissolution. However, recent work on silver-catalyzed dissolution of PuO[sub 2] with persulfate has demonstrated that persulfate ions regenerate silver (II). Use of persulfate to regenerate cerium (IV) or bismuth (V) ions during dissolution of PuO[sub 2] materials may warrant further study.

  12. Plutonium oxide dissolution

    SciTech Connect

    Gray, J.H.

    1992-09-30

    Several processing options for dissolving plutonium oxide (PuO{sub 2}) from high-fired materials have been studied. The scoping studies performed on these options were focused on PuO{sub 2} typically generated by burning plutonium metal and PuO{sub 2} produced during incineration of alpha contaminated waste. At least two processing options remain applicable for dissolving high-fired PuO{sub 2} in canyon dissolvers. The options involve solid solution formation of PuO{sub 2} With uranium oxide (UO{sub 2}) and alloying incinerator ash with aluminum. An oxidative dissolution process involving nitric acid solutions containing a strong oxidizing agent, such as cerium (IV), was neither proven nor rejected. This uncertainty was due to difficulty in regenerating cerium (IV) ions during dissolution. However, recent work on silver-catalyzed dissolution of PuO{sub 2} with persulfate has demonstrated that persulfate ions regenerate silver (II). Use of persulfate to regenerate cerium (IV) or bismuth (V) ions during dissolution of PuO{sub 2} materials may warrant further study.

  13. Understanding gas hydrate dissolution

    NASA Astrophysics Data System (ADS)

    Lapham, Laura; Chanton, Jeffrey; MacDonald, Ian; Martens, Christopher

    2010-05-01

    In order to understand the role gas hydrates play in climate change or their potential as an energy source, we must first understand their basic behaviors. One such behavior not well understood is their dissolution and the factors that control it. Theoretically, hydrates are stable in areas of high pressure, low temperature, moderate salt concentrations, and saturated methane. Yet in nature, we observe hydrate to outcrop seafloor sediments into overlying water that is under-saturated with respect to methane. How do these hydrates not dissolve away? To address this question, we combine both field and laboratory experiments. In the field, we have collected pore-waters directly surrounding gas hydrate outcrops and measured for in situ methane concentrations. This gives us an understanding of the concentration gradients, and thus methane flux, directly from the hydrate to the surrounding environment. From these samples, we found that methane concentrations decreased further from hydrate yet are always under-saturated with respect to methane hydrate. The resulting low methane gradients were then used to calculate low dissolution rates. This result suggests that hydrates are meta-stable in the environment. What controls their apparent meta-stability? We hypothesize that surrounding oils or microbial slimes help protect the hydrate and slow down their dissolution. To test this hypothesis, we conducted a series of laboratory experiments where hydrate was formed at in situ pressure and temperature and the source gas removed; first with no oils, then with oils. Dissolved methane concentrations were then measured in surrounding fluids over time and dissolution rates calculated. To date, both methane and mixed gas hydrate (methane, ethane, and propane) have similar dissolution rates of 0.12 mM/hr. Future experiments will add oils to determine how different hydrate dissolves with such contaminants. This study will further our understanding of factors that control hydrate

  14. Determinants of marriage dissolution

    NASA Astrophysics Data System (ADS)

    Rahim, Mohd Amirul Rafiq Abu; Shafie, Siti Aishah Mohd; Hadi, Az'lina Abdul; Razali, Nornadiah Mohd; Azid @ Maarof, Nur Niswah Naslina

    2015-10-01

    Nowadays, the number of divorce cases among Muslim couples is very worrisome whereby the total cases reported in 2013 increased by half of the total cases reported in the previous year. The questions on the true key factors of dissolution of marriage continue to arise. Thus, the objective of this study is to reveal the factors that contribute to the dissolution of marriage. A total of 181 cases and ten potential determinants were included in this study. The potential determinants considered were age at marriage of husband and wife, educational level of husband and wife, employment status of husband and wife, income of husband and wife, the number of children and the presence at a counseling session. Logistic regression analysis was used to analyze the data. The findings revealed that four determinants, namely the income of husband and wife, number of children and the presence at a counselling session were significant in predicting the likelihood of divorce among Muslim couples.

  15. Bisphenol AF stimulates transcription and secretion of C-X-C chemokine ligand 12 to promote proliferation of cultured T47D breast cancer cells.

    PubMed

    Li, Ming; Han, Xiaoyu; Gao, Wenhui; Chen, Feng; Shao, Bing

    2015-12-01

    Bisphenol AF (4,4'-hexafluoroisopropylidene-2-diphenol, BPAF), an endocrine disruptor, has been shown to stimulate the proliferation of human breast cancer cells. However, the underlying mechanism has not been fully elucidated. We found that BPAF promoted the in vitro proliferation of estrogen receptor α (ERα)-positive breast cancer cells (T47D and MCF7), but not ERα-negative cells (MDA-MB-231 and MDA-MB-435s). BPAF significantly stimulated the proliferation of cultured T47D cell in a dose-dependent manner, and the half-maximal effective concentration (EC50) was approximately 123 nM. We employed lentivirus-mediated short hairpin RNA (shRNA) to knockdown ERα and ER antagonist ICI 182780 to inhibit ER activation, which resulted in the repression of BPAF-induced proliferation of T47D and MCF7 cells. We observed that C-X-C chemokine ligand 12 (CXCL12) was up-regulated in T47D cells under treatment with BPAF. Quantitative real-time PCR results showed that BPAF caused a time and dose dependent increase in mRNA level of CXCL12. Furthermore, treatment of T47D cells with BPAF increased CXCL12 secretion according to ELISA assay. BPAF-induced CXCL12 transcription and secretion was significantly attenuated by small interfering RNA (siRNA) targeting ERα and ICI 182780, indicating BPAF-induced CXCL12 expression is mediated through ERα. Notably, knockdown CXCL12 in T47D cells significantly attenuated BPAF-induced cell proliferation. We also observed that inhibition of CXCL12 binding to its receptors CXCR4 and CXCR7 by chalcone 4 blocked BPAF-induced cell growth. Our results indicated that CXCL12 facilitated BPAF-induced proliferation of T47D cells. Taken together, our data provided support that BPAF stimulated transcription and secretion of CXCL12 depending on ERα, and ERα/CXCL12 signaling positively regulated BPAF-induced proliferation of cultured T47D breast cancer cells. PMID:26435001

  16. Solubility limits on radionuclide dissolution

    SciTech Connect

    Kerrisk, J.F.

    1984-12-31

    This paper examines the effects of solubility in limiting dissolution rates of a number of important radionuclides from spent fuel and high-level waste. Two simple dissolution models were used for calculations that would be characteristics of a Yucca Mountain repository. A saturation-limited dissolution model, in which the water flowing through the repository is assumed to be saturated with each waste element, is very conservative in that it overestimates dissolution rates. A diffusion-limited dissolution model, in which element-dissolution rates are limited by diffusion of waste elements into water flowing past the waste, is more realistic, but it is subject to some uncertainty at this time. Dissolution rates of some elements (Pu, Am, Sn, Th, Zr, Sm) are always limited by solubility. Dissolution rates of other elements (Cs, Tc, Np, Sr, C, I) are never solubility limited; their release would be limited by dissolution of the bulk waste form. Still other elements (U, Cm, Ni, Ra) show solubility-limited dissolution under some conditions. 9 references, 3 tables.

  17. Fundamental studies of dissolution inhibition in poly(norbornene-alt-maleic anhydride) based resins

    NASA Astrophysics Data System (ADS)

    Houlihan, F. M.; Dabbagh, G.; Rushkin, I.; Hutton, R.; Bolan, K.; Reichmanis, E.; Nalamasu, O.; Yan, Z.; Reiser, A.

    2001-07-01

    The dissolution inhibition mechanism for tert-butylcarboxylate (e.g. tert-butyl cholate) dissolution inhibitors and onium salt photoacid generators (PAG's) were examined in terpolymers of poly(norbornene-maleic anhydride-acrylic acid) (P(NB/MA/AA)). For tert-butyl carboxylates, increasing hydrophobicity increased the dissolution inhibition ability. Dissolution promotion tracked with the number of carboxylic acid moieties and the hydrophobicity of carboxylic acids moieties released upon acidolytic cleavage of the tert-butyl carboxylate. For onium salt PAG's, increasing the hydrophobicity and size of fluorinated anions decreased dissolution inhibition.

  18. Organic Ligand Enhanced Cr(VI) Treatment in Pyrite Permeable Reactive Barriers

    NASA Astrophysics Data System (ADS)

    Kantar, Cetin; Ari, Cihan; Samet Bulbul, Muhammet

    2014-05-01

    Permeable reactive barriers (PRB), installed in subsurface in the path of flowing groundwater can offer a viable option for in situ remediation of Cr(VI)-contaminated subsurface systems. In this study, batch and column experiments were performed to determine the effects of organic ligands (L) on Cr(VI) treatment in PRBs containing pyrite. The organic ligands used include citrate, tartrate, oxalate, EDTA and salycilate. The results indicate that in the absence of organic ligands, the Cr(VI)removal by pyrite occurred only under acidic conditions (e.g., pH > 5). However, organic ligands led to a significant increase in Cr(VI) removal with pyrite depending on the type of organic ligand used, Cr(VI)/LT ratio and water chemistry (e.g., pH). While salicylate had no effect on Cr(VI) removal relative to non-ligand systems, the organic ligands including citrate, tartrate and oxalate significantly improved Cr(VI) removal under acidic to alkaline pH range. On the other hand, EDTA only improved Cr(VI) removal by pyrite under alkaline pH conditions relative to non-ligand conditions. In general, the efficiency of organic ligands on Cr(VI) removal decreased in the order: citrate > tartrate> oxalate>EDTA>salycilate. The X-ray photoelectron spectroscopy (XPS) and zeta potential measurements suggest that the Cr(VI) removal by pyrite occured due to the reduction of Cr(VI) to Cr(III), coupled with the oxidation of Fe(II) to Fe(III) and disulfide (S22-) to sulfate (SO42-) at the pyrite surface as well as in aqueous phase. However, the precipitation of sparingly soluble Fe(III-Cr(III)(oxy) hydroxide phases on pyrite surface led to surface passivation, which, then, inhibited further Cr(VI) reduction. The addition of organic ligands increased Cr(VI) reduction by pyrite due to: 1) the removal of the surface oxidation products by forming highly soluble Cr(III) and Fe(III)-ligand complexes as well as 2) the ligand promoted dissolution of Fe(II) from pyrite, which, subsequently, reduced Cr

  19. A Dinuclear Ruthenium-Based Water Oxidation Catalyst: Use of Non-Innocent Ligand Frameworks for Promoting Multi-Electron Reactions

    PubMed Central

    Laine, Tanja M; Kärkäs, Markus D; Liao, Rong-Zhen; Siegbahn, Per E M; Åkermark, Björn

    2015-01-01

    Insight into how H2O is oxidized to O2 is envisioned to facilitate the rational design of artificial water oxidation catalysts, which is a vital component in solar-to-fuel conversion schemes. Herein, we report on the mechanistic features associated with a dinuclear Ru-based water oxidation catalyst. The catalytic action of the designed Ru complex was studied by the combined use of high-resolution mass spectrometry, electrochemistry, and quantum chemical calculations. Based on the obtained results, it is suggested that the designed ligand scaffold in Ru complex 1 has a non-innocent behavior, in which metal–ligand cooperation is an important part during the four-electron oxidation of H2O. This feature is vital for the observed catalytic efficiency and highlights that the preparation of catalysts housing non-innocent molecular frameworks could be a general strategy for accessing efficient catalysts for activation of H2O. PMID:25925847

  20. Plutonium dissolution process

    DOEpatents

    Vest, Michael A.; Fink, Samuel D.; Karraker, David G.; Moore, Edwin N.; Holcomb, H. Perry

    1996-01-01

    A two-step process for dissolving plutonium metal, which two steps can be carried out sequentially or simultaneously. Plutonium metal is exposed to a first mixture containing approximately 1.0M-1.67M sulfamic acid and 0.0025M-0.1M fluoride, the mixture having been heated to a temperature between 45.degree. C. and 70.degree. C. The mixture will dissolve a first portion of the plutonium metal but leave a portion of the plutonium in an oxide residue. Then, a mineral acid and additional fluoride are added to dissolve the residue. Alteratively, nitric acid in a concentration between approximately 0.05M and 0.067M is added to the first mixture to dissolve the residue as it is produced. Hydrogen released during the dissolution process is diluted with nitrogen.

  1. Plutonium dissolution process

    DOEpatents

    Vest, M.A.; Fink, S.D.; Karraker, D.G.; Moore, E.N.; Holcomb, H.P.

    1994-01-01

    A two-step process for dissolving Pu metal is disclosed in which two steps can be carried out sequentially or simultaneously. Pu metal is exposed to a first mixture of 1.0-1.67 M sulfamic acid and 0.0025-0.1 M fluoride, the mixture having been heated to 45-70 C. The mixture will dissolve a first portion of the Pu metal but leave a portion of the Pu in an oxide residue. Then, a mineral acid and additional fluoride are added to dissolve the residue. Alternatively, nitric acid between 0.05 and 0.067 M is added to the first mixture to dissolve the residue as it is produced. Hydrogen released during the dissolution is diluted with nitrogen.

  2. The mouse CCR2 gene is regulated by two promoters that are responsive to plasma cholesterol and peroxisome proliferator-activated receptor {gamma} ligands

    SciTech Connect

    Chen Yiming; Green, Simone R.; Ho, Jessica; Li, Andrew; Almazan, Felizidad; Quehenberger, Oswald . E-mail: oquehenberger@ucsd.edu

    2005-06-24

    We have previously shown that the expression of monocyte CCR2, the receptor for monocyte chemoattractant protein-1, is induced by plasma cholesterol. The present study examines the mechanisms that regulate monocyte CCR2 expression in hypercholesterolemia using a mouse model. Our data demonstrate that in the mouse, CCR2 expression in circulating monocytes is controlled by two promoters P1 and P2. The two distinct transcripts, which encode the same protein, are produced by alternative splicing in the 5'-untranslated region. Both promoters are constitutively active, but only P2 is stimulated by cholesterol. However, both promoters are repressed by peroxisome proliferator-activated receptor {gamma}.

  3. The copper-free Sonogashira cross-coupling reaction promoted by palladium complexes of nitrogen-containing chelating ligands in neat water at room temperature.

    PubMed

    Zhong, Hong; Wang, Jinyun; Li, Liuyi; Wang, Ruihu

    2014-02-01

    The commercially available 2,2'-dipyridylamine was used as a supporting ligand in the palladium-catalyzed Sonogashira cross-coupling reaction. The reactions between aryl iodides and terminal alkynes with different steric hindrance can be efficiently performed in the absence of copper in neat water at room temperature. The superior catalytic performance of the catalytic system was attributed to water solubility of the palladium 2,2'-dipyridylamine complex. Palladium nanoparticles with small size and narrow size distribution were formed after the cross-coupling reaction. PMID:24281778

  4. FAM19A4 is a novel cytokine ligand of formyl peptide receptor 1 (FPR1) and is able to promote the migration and phagocytosis of macrophages

    PubMed Central

    Wang, Wenyan; Li, Ting; Wang, Xiaolin; Yuan, Wanxiong; Cheng, Yingying; Zhang, Heyu; Xu, Enquan; Zhang, Yingmei; Shi, Shuang; Ma, Dalong; Han, Wenling

    2015-01-01

    FAM19A4 is an abbreviation for family with sequence similarity 19 (chemokine (C–C motif)-like) member A4, which is a secretory protein expressed in low levels in normal tissues. The biological functions of FAM19A4 remain to be determined, and its potential receptor(s) is unclarified. In this study, we demonstrated that FAM19A4 was a classical secretory protein and we verified for the first time that its mature protein is composed of 95 amino acids. We found that the expression of this novel cytokine was upregulated in lipopolysaccharide (LPS)-stimulated monocytes and macrophages and was typically in polarized M1. FAM19A4 shows chemotactic activities on macrophages and enhances the macrophage phagocytosis of zymosan both in vitro and in vivo with noticeable increases of the phosphorylation of protein kinase B (Akt). FAM19A4 can also increase the release of reactive oxygen species (ROS) upon zymosan stimulation. Furthermore, based on receptor internalization, radio ligand binding assays and receptor blockage, we demonstrated for the first time that FAM19A4 is a novel ligand of formyl peptide receptor 1 (FPR1). The above data indicate that upon inflammatory stimulation, monocyte/macrophage-derived FAM19A4 may play a crucial role in the migration and activation of macrophages during pathogenic infections. PMID:25109685

  5. Kinetics of feldspar and quartz dissolution at 70-80°C and near-neutral pH: effects of organic acids and NaCl

    NASA Astrophysics Data System (ADS)

    Blake, R. E.; Waltera, L. M.

    1999-07-01

    Effects of the organic acid (OA) anions, oxalate and citrate, on the solubility and dissolution kinetics of feldspars (labradorite, orthoclase, and albite) at 80°C and of quartz at 70°C were investigated at pH 6 in separate batch experiments and in media with different ionic strength (0.02-2.2 M NaCl). Although it has been shown that OAs can increase rates of feldspar dissolution, prior experiments have focused primarily on dilute, highly undersaturated and acidic conditions where feldspar dissolution kinetics are dominated by H + adsorption and exchange reactions. Many natural waters, however, are only weakly acidic and have variable ionic strength and composition which would be expected to influence mineral surface properties and mechanisms of organic ligand-promoted reactions. Oxalate and citrate (2-20 mM) increased the rate of quartz dissolution by up to a factor of 2.5. Quartz solubility, however, was not increased appreciably by these OAs, suggesting that Si-OA complexation is not significant under these conditions. The lack of significant OA-SiO 2 interaction is important to understanding the effects of OAs on the release of both Si and Al from feldspars. In contrast to quartz, both the rates of dissolution and amounts of Si and Al released from the three feldspars studied increased regularly with increasing OA concentration. Feldspar dissolution was congruent at all but the lowest OA concentrations. Total dissolved Al concentrations increased by 1-2 orders of magnitude in the presence of oxalate and citrate, and reached values as high as 43 mg/l (1.6 mM). Si concentrations reached values up to 65 mg/l (2.3 mM) in feldspar-OA experiments. Precipitation of authigenic clays was observed only in experiments without or at very low concentrations of OAs. The high concentrations of dissolved Si attained during dissolution of feldspars in OA solutions, relative to Si concentrations in quartz-OA experiments, is attributed to concomitant release of Si driven by

  6. Phthalic acid complexation and the dissolution of forsteritic glass studied via in situ FTIR and X-ray scattering

    NASA Astrophysics Data System (ADS)

    Morris, Peter M.; Wogelius, Roy A.

    2008-04-01

    Multiple Internal Reflection Fourier Transform Infra-Red (MIR-FTIR) spectroscopy was developed and used for in situ flow-through experiments designed to study the process of organic acid promoted silicate dissolution. In tandem with the FTIR analysis, ex situ X-ray scattering was used to perform detailed analyses of the changes in the surface structure and chemistry resulting from the dissolution process. Phthalic acid and forsteritic glass that had been Chemically Vapour Deposited (CVD) onto an internal reflection element were used as reactants, and the MIR-FTIR results showed that phthalic acid may promote dissolution by directly binding to exposed Mg metal ion centers on the solid surface. Integrated infrared absorption intensity as a function of time shows that phthalic acid attachment apparently follows a t1/2 dependence, indicating that attachment is a diffusive process. The diffusion coefficient of phthalic acid was estimated to be approximately 7 × 10 -6 cm 2 s -1 in the solution near the interface with the glass. Shifts in the infrared absorption structure of the phthalate complexed with the surface compared to the solute species indicate that phthalate forms a seven-membered ring chelate complex. This bidentate complex efficiently depletes Mg from the glass surface, such that after reaction as much as 95% of the Mg may be removed. Surface depletion in Mg causes adsorbate density to fall after an initial attachment stage for the organic ligand. In addition, the infrared analysis shows that silica in the near surface polymerizes after Mg removal, presumably to maintain charge balance. X-ray reflectivity shows that the dissolution rate of forsteritic glass at pH 4 based on Mg removal in such flow-through experiments was equal to 4 × 10 -12 mol cm -2 s -1 (geometric surface area normalized). Reflectivity also shows how the surface mass density decreases during reaction from 2.64 g cm -3 to 2.2 g cm -3, consistent with preferential loss of Mg from the

  7. A novel phase variation mechanism in the meningococcus driven by a ligand-responsive repressor and differential spacing of distal promoter elements.

    PubMed

    Metruccio, Matteo M E; Pigozzi, Eva; Roncarati, Davide; Berlanda Scorza, Francesco; Norais, Nathalie; Hill, Stuart A; Scarlato, Vincenzo; Delany, Isabel

    2009-12-01

    Phase variable expression, mediated by high frequency reversible changes in the length of simple sequence repeats, facilitates adaptation of bacterial populations to changing environments and is frequently important in bacterial virulence. Here we elucidate a novel phase variable mechanism for NadA, an adhesin and invasin of Neisseria meningitidis. The NadR repressor protein binds to operators flanking the phase variable tract and contributes to the differential expression levels of phase variant promoters with different numbers of repeats likely due to different spacing between operators. We show that IHF binds between these operators, and may permit looping of the promoter, allowing interaction of NadR at operators located distally or overlapping the promoter. The 4-hydroxyphenylacetic acid, a metabolite of aromatic amino acid catabolism that is secreted in saliva, induces NadA expression by inhibiting the DNA binding activity of the repressor. When induced, only minor differences are evident between NadR-independent transcription levels of promoter phase variants and are likely due to differential RNA polymerase contacts leading to altered promoter activity. Our results suggest that NadA expression is under both stochastic and tight environmental-sensing regulatory control, both mediated by the NadR repressor, and may be induced during colonization of the oropharynx where it plays a major role in the successful adhesion and invasion of the mucosa. Hence, simple sequence repeats in promoter regions may be a strategy used by host-adapted bacterial pathogens to randomly switch between expression states that may nonetheless still be induced by appropriate niche-specific signals. PMID:20041170

  8. Alunite dissolution rates: Dissolution mechanisms and implications for Mars

    NASA Astrophysics Data System (ADS)

    Miller, J. L.; Elwood Madden, A. S.; Phillips-Lander, C. M.; Pritchett, B. N.; Elwood Madden, M. E.

    2016-01-01

    Alunite (KAl3(SO4)2(OH)6) is a hydrated aluminous sulfate mineral associated with acidic, oxidizing aqueous environments on Earth. Additionally, orbiting spacecraft and rovers on Mars have reported spectral data that indicate a range of mono- and polyhydrated sulfate phases and hydroxysulfate phases, suggesting such conditions also existed on Mars in the past. This study examines alunite dissolution rates in aqueous systems with varying pH, temperature, and solution chemistry conditions. Alunite dissolution rates in dilute solutions are 2-3 orders of magnitude slower than jarosite dissolution rates measured under analogous conditions. Similar to jarosite, alunite dissolution rates vary as a function of activity of H+ and OH- following the rate law log r (mol m-2 s-1) = -0.133(±0.02)pH - 10.65(±0.07) at pH < 5 and log r = 0.194(±0.04)pH - 12.53(±0.26) at pH > 5. However, minimum alunite dissolution rates are shifted to higher pH (5-5.5), likely due to differences in Fe and Al speciation. Alunite and jarosite rates converge in saturated NaCl and CaCl2 brines as the activity of water decreases, suggesting that differences in water exchange rates with Fe3+ and Al3+ control dissolution rates in dilute solutions, while metal-Cl- complexation occurs at similar rates within the brines. Particle lifetimes based on measured dissolution rates in dilute solutions show that alunite particles are expected to be preserved two orders of magnitude longer than jarosite particles over a range of pH and temperature conditions. In particular, alunite is more likely to be preserved in neutral to moderately alkaline systems compared to jarosite, which is expected to be preserved in more acidic conditions. Alunite dissolution produced amorphous Al-rich alteration products at moderate to high pH. Unlike jarosite, alunite dissolution does not show a clear trend as a function of temperature; alunite dissolution rates do not increase with increasing temperature, likely due to lower

  9. Statistical comparison of dissolution profiles.

    PubMed

    Wang, Yifan; Snee, Ronald D; Keyvan, Golshid; Muzzio, Fernando J

    2016-05-01

    Statistical methods to assess similarity of dissolution profiles are introduced. Sixteen groups of dissolution profiles from a full factorial design were used to demonstrate implementation details. Variables in the design include drug strength, tablet stability time, and dissolution testing condition. The 16 groups were considered similar when compared using the similarity factor f2 (f2 > 50). However, multivariate ANOVA (MANOVA) repeated measures suggested statistical differences. A modified principal component analysis (PCA) was used to describe the dissolution curves in terms of level and shape. The advantage of the modified PCA approach is that the calculated shape principal components will not be confounded by level effect. Effect size test using omega-squared was also used for dissolution comparisons. Effects indicated by omega-squared are independent of sample size and are a necessary supplement to p value reported from the MANOVA table. Methods to compare multiple groups show that product strength and dissolution testing condition had significant effects on both level and shape. For pairwise analysis, a post-hoc analysis using Tukey's method categorized three similar groups, and was consistent with level-shape analysis. All these methods provide valuable information that is missed using f2 method alone to compare average profiles. The improved statistical analysis approach introduced here enables one to better ascertain both statistical significance and clinical relevance, supporting more objective regulatory decisions. PMID:26294289

  10. Glyconanomaterials: Synthesis, Characterization, and Ligand Presentation

    PubMed Central

    Wang, Xin

    2010-01-01

    Glyconanomaterials, nanomaterials carrying surface-tethered carbohydrate ligands, have emerged and demonstrated increasing potential in biomedical imaging, therapeutics, and diagnostics. These materials combine the unique properties of nanometer-scale objects with the ability to present multiple copies of carbohydrate ligands, greatly enhancing the weak affinity of individual ligands to their binding partners. Critical to the performance of glyconanomaterials is the proper display of carbohydrate ligands, taking into consideration of the coupling chemistry, the type and length of the spacer linkage, and the ligand density. This article provides an overview of the coupling chemistry for attaching carbohydrate ligands to nanomaterials, and discusses the need for thorough characterization of glyconanomaterials, especially quantitative analyses of the ligand density and binding affinities. Using glyconanoparticles synthesized by a versatile photocoupling chemistry, methods for determining the ligand density by colorimetry and the binding affinity with lectins by a fluorescence competition assay are determined. The results show that the multivalent presentation of carbohydrate ligands significantly enhances the binding affinity by several orders of magnitude in comparison to the free ligands in solution. The effect is sizeable even at low surface ligand density. The type and length of the spacer linkage also affect the binding affinity, with the longer linkage promoting the association of bound ligands with the corresponding lectins. PMID:20301131

  11. NKG2D ligands as therapeutic targets

    PubMed Central

    Spear, Paul; Wu, Ming-Ru; Sentman, Marie-Louise; Sentman, Charles L.

    2013-01-01

    The Natural Killer Group 2D (NKG2D) receptor plays an important role in protecting the host from infections and cancer. By recognizing ligands induced on infected or tumor cells, NKG2D modulates lymphocyte activation and promotes immunity to eliminate ligand-expressing cells. Because these ligands are not widely expressed on healthy adult tissue, NKG2D ligands may present a useful target for immunotherapeutic approaches in cancer. Novel therapies targeting NKG2D ligands for the treatment of cancer have shown preclinical success and are poised to enter into clinical trials. In this review, the NKG2D receptor and its ligands are discussed in the context of cancer, infection, and autoimmunity. In addition, therapies targeting NKG2D ligands in cancer are also reviewed. PMID:23833565

  12. Enhanced dissolution of silicate minerals by bacteria at near-neutral pH.

    PubMed

    Vandevivere, P; Welch, S A; Ullman, W J; Kirchman, D L

    1994-05-01

    Previous studies have shown that various microorganisms can enhance the dissolution of silicate minerals at low (<5) or high (>8) pH. However, it was not known if they can have an effect at near-neutral pH. Almost half of 17 isolates examined in this study stimulated bytownite dissolution at near-neutral pH while in a resting state in buffered glucose. Most of the isolates found to stimulate dissolution also oxidized glucose to gluconic acid. More detailed analysis with one of these isolates suggested that this partial oxidation was the predominant, if not sole, mechanism of enhanced dissolution. Enhanced dissolution did not require direct contact between the dissolving mineral and the bacteria. Gluconate-promoted dissolution was also observed with other silicate minerals such as albite, quartz, and kaolinite. PMID:24190338

  13. Effect of bacteria and dissolved organics on mineral dissolution kinetics:

    NASA Astrophysics Data System (ADS)

    Pokrovsky, Oleg; Shirokova, Liudmila; Benezeth, Pascale; Zabelina, Svetlana

    2010-05-01

    Quantification of the effect of microorganisms and associated organic ligands on mineral dissolution rate is one among the last remaining challenges in modeling of water-rock interactions under earth surface and subsurface environments. This is especially true for deep underground settings within the context of CO2 capture, sequestration and storage. First, elevated CO2 pressures create numerous experimental difficulties for performing robust flow-through experiments at a given saturation state. Second, reactivity of main rock-forming minerals in abiotic systems at pCO2 >> 1 atm and circumneutral pH is still poorly constrained. And third, most of microbial habitats of the subsurface biosphere are not suitable for routine culturing in the laboratory, many of them are anaerobic and even strictly anaerobic, and many bacteria and archae cultures can live only in the consortium of microorganisms which is very hard to maintain at a controlled and stable biomass concentration. For experimental modeling of bio-mineral interactions in the laboratory, two other main conceptual challenges exist. Typical concentration of dissolved organic carbon that serves as a main nutrient for heterotrophic bacteria in underground waters rarely exceeds 3-5 mg/L. Typical concentration of DOC in nutrient media used for bacteria culturing is between 100 and 10,000 mg/L. Therefore, performing mineral-bacteria interactions in the laboratory under environmentally-sound conditions requires significant dilution of the nutrient media or the use of flow-through reactors. Concerning the effect of organic ligands and bacterial excudates on rock-forming mineral dissolution, at the present time, mostly empirical (phenomenological) approach can be used. Indeed, the pioneering studies of Stumm and co-workers have established a firm basis for modeling the catalyzing and inhibiting effects of ligands on metal oxide dissolution rate. This approach, very efficient for studying the interaction of organic and

  14. Predicting target-ligand interactions using protein ligand-binding site and ligand substructures

    PubMed Central

    2015-01-01

    the interactions. Conclusions The target and ligand bindings are local events, and the local information dominate the binding ability. Though integrating of the global information can promote the predictive ability, the role is very limited. The fragment interaction network is helpful for understanding the mechanism of the ligand-target interaction. PMID:25707321

  15. Effect of oxalate on the dissolution rates of oligoclase and tremolite (journal version)

    SciTech Connect

    Mast, M.A.; Drever, J.I.

    1987-01-01

    The effect of oxalate, a strong chelator for Al and other cations, on the dissolution rates of oligoclase feldspar and tremolite amphibole was investigated in a flow-through reactor at 22 deg C. Oxalate at concentrations of 0.5 and 1 mM has essentially no effect on the dissolution rate of tremolite, nor on the steady-state rate of release of Si from oligoclase. The fact that oxalate has no effect on dissolution rate suggests that detachment of Si rather than Al or Mg is the rate-limiting step. At pH 4 and 9, oxalate has no effect on the steady-state rate of release of Al, and dissolution is congruent. At pH 5 and 7, oligoclase dissolution is congruent in the presence of oxalate, but in the absence of oxalate Al is preferentially retained in the solid relative to Si. The rate of dissolution of tremolite is independent of pH over the pH range 2-5, and decreases at higher pH. The rate of dissolution of oligoclase was independent of pH over the pH range 4-9. Since the dissolution rate of these minerals is independent of pH and organic ligand concentration, the effect of acid deposition from the atmosphere on the rate of supply of cations from weathering of granitic rocks should be minor.

  16. The TLR9 ligand CpG promotes the acquisition of Plasmodium falciparum-specific memory B cells in malaria-naive individuals.

    PubMed

    Crompton, Peter D; Mircetic, Marko; Weiss, Greta; Baughman, Amy; Huang, Chiung-Yu; Topham, David J; Treanor, John J; Sanz, Iñaki; Lee, F Eun-Hyung; Durbin, Anna P; Miura, Kazutoyo; Narum, David L; Ellis, Ruth D; Malkin, Elissa; Mullen, Gregory E D; Miller, Louis H; Martin, Laura B; Pierce, Susan K

    2009-03-01

    Despite the central role of memory B cells (MBC) in protective immune responses, little is understood about how they are acquired in naive individuals in response to Ag exposure, and how this process is influenced by concurrent activation of the innate immune system's TLR. In this longitudinal study of malaria-naive individuals, we examined the MBC response to two candidate malaria vaccines administered with or without CpG, a TLR9 ligand. We show that the acquisition of MBC is a dynamic process in which the vaccine-specific MBC pool rapidly expands and then contracts, and that CpG enhances the kinetics, magnitude, and longevity of this response. We observed that the percentage of vaccine-specific MBC present at the time of reimmunization predicts vaccine-specific Ab levels 14 days later; and that at steady-state, there is a positive correlation between vaccine-specific MBC and Ab levels. An examination of the total circulating MBC and plasma cell pools also suggests that MBC differentiate into plasma cells through polyclonal activation, independent of Ag specificity. These results provide important insights into the human MBC response, which can inform the development of vaccines against malaria and other pathogens that disrupt immunological memory. PMID:19234231

  17. Dissolution of Plasma-Sprayed Wollastonite Coatings: The Effects of Microstructure Coupled with Stress

    NASA Astrophysics Data System (ADS)

    Wang, Weize; Xuan, Fuzhen; Liang, Jiachun; Wang, Luobin

    2012-09-01

    Wollastonite coatings are deposited on the U-shape titanium alloy coupons by atmospheric plasma spraying at substrate temperatures of room temperature and 400 °C, respectively. The effects of applied stresses and microstructure on the dissolution behavior of wollastonite coatings have been investigated. The dissolution rate is characterized by the ion concentration changes of Ca, Si, and P in the SBF solution. The coatings deposited at room temperature show higher porosity and lower crystallinity, and further higher dissolution rate is observed, compared with the coatings deposited at a substrate temperature of 400 °C. Applied tensile stresses promote the coating dissolution. The effect of compressive stresses on the dissolution of coatings depends on the balance between the hindrance effect and the promotion action caused by the debonding and/or peeling off. The stress condition cannot change the phase transformation process when the substrate crystal structure is adverse for the apatite precipitation.

  18. Alginic Acid Accelerates Calcite Dissolution

    NASA Astrophysics Data System (ADS)

    Perry, T. D.; Duckworth, O. W.; McNamara, C. J.; Martin, S. T.; Mitchell, R.

    2003-12-01

    Accelerated carbonate weathering through biological activity affects both geochemical cycling and the local pH and alkalinity of terrestrial and marine waters. Microbes affect carbonate dissolution through metabolic activity, production of acidic or chelating exudates, and cation binding by cell walls. Dissolution occurs within microbial biofilms - communities of microorganisms attached to stone in an exopolymer matrix. We investigated the effect of alginic acid, a common biological polymer produced by bacteria and algae, on calcite dissolution using a paired atomic force microscopy/flow-through reactor apparatus. The alginic acid caused up to an order of magnitude increase in dissolution rate at 3 < pH < 12. Additionally, the polymer preferentially binds to the obtuse pit steps and increases step velocity. We propose that the polymer is actively chelating surficial cations reducing the activation energy and increasing dissolution rate. The role of biologically produced polymers in mineral weathering is important in the protection of cultural heritage materials and understanding of marine and terrestrial systems.

  19. Nanotechnology versus other techniques in improving drug dissolution.

    PubMed

    Kwok, Philip Chi Lip; Chan, Hak-Kim

    2014-01-01

    Many newly discovered drug molecules have low aqueous solubility, which results in low bioavailability. One way to improve their dissolution is to formulate them as nanoparticles, which have high specific surface areas, consequently increasing the dissolution rate and solubility. Nanoparticles can be produced via top-down or bottom-up methods. Top-down techniques such as wet milling and high pressure homogenisation involve reducing large particles to nano-sizes. Some pharmaceutical products made by these processes have been marketed. Bottom-up methods such as precipitation and controlled droplet evaporation form nanoparticles from molecules in solution. To minimise aggregation upon drying and promote redispersion of the nanoparticles upon reconstitution or administration, hydrophilic matrix formers are added to the formulation. However, the nanoparticles will eventually agglomerate together after dispersing in the liquid and hinders dissolution. Currently there is no pharmacopoeial method specified for nanoparticles. Amongst the current dissolution apparatus available for powders, the flow-through cell has been shown to be the most suitable. Regulatory and pharmacopoeial standards should be established in the future to standardise the dissolution testing of nanoparticles. More nanoparticle formulations of new hydrophobic drugs are expected to be developed in the future with the advancement of nanotechnology. However, the agglomeration problem is inherent and difficult to overcome. Thus the benefit of dissolution enhancement often cannot be fully realised. On the other hand, chemical strategies such as modifying the parent drug molecule to form a more soluble salt form, prodrug, or cyclodextrin complexation are well established and have been shown to be effective in enhancing dissolution. Thus the value of nanoformulations needs to be interpreted in the light of their limitations. Chemical approaches should also be considered in new product development. PMID

  20. Mechanism of single-layer 193-nm dissolution inhibition resist

    NASA Astrophysics Data System (ADS)

    Yan, Zhenglin; Houlihan, Francis M.; Reichmanis, Elsa; Nalamasu, Omkaram; Reiser, Arnost; Dabbagh, Gary; Hutton, Richard S.; Osei, Dan; Sousa, Jose; Bolan, Kevin J.

    2000-06-01

    We have found that the progress of developer base into films of terpolymers of norbornene (NB)-maleic anhydride (MA) and acrylic acid (AA) is a percolation process with a critical site concentration of x(c) equals 0.084 which suggests that every acrylic acid site in the terpolymer of norbornene-maleic anhydride-acrylic acid can make 12 monomer units of the polymer water compatible. In practice these systems are being used with various tert-butyl esters of cholic acid as dissolution inhibitors. The cholates differ very much in their dissolution inhibition factors (lowest t-butyl cholate (1.3) to highest t-butyl lithocholate glutarate dimer (7.4). The change in these factors corrected for molarity follow the hydrophobic character of the dissolution as measured by log(p). A quick screening method has also been established to evaluate dissolution inhibitors based on our observation that the cloud point (the volume % acetone in a water/acetone which gives persistent cloudiness) parallels the dissolution inhibiting power as measured by the dissolution inhibition factor. For dissolution promotion, optimal results are obtained with t-butyl 1,3,5-cyclohexanetricarboxylate (f equals -6.3) and poorest results with t-butyl lithocholate (f equals -2.8); this appears to track with the number of carboxyl groups and the hydrophobicity of the carboxylic acids. The Rmax found for resist formulations tracks well with these findings. Another factor in determining the ultimate achievable contrast is the degree of acidolytic deprotection achieved by the material. It appears that acidolyticaly cleaveable carboxylate esters with a higher concentration of electron withdrawing groups such as t-butyl 1,3,5-cyclohexanetricarboxylate are more effective.

  1. Bench Scale Saltcake Dissolution Test Report

    SciTech Connect

    BECHTOLD, D.B.; PACQUET, E.A.

    2000-12-06

    A potential scenario for retrieving saltcake from single shell tanks is the ''Rainbird{reg_sign} sprinkler'' method. Water is distributed evenly across the surface of the saltcake and allowed to percolate by gravity through the waste. The salt dissolves in the water, forming a saturated solution. The saturated liquid is removed by a saltwell pump situated near the bottom of the tank. By this method, there is never a large inventory of liquid in the tank that could pose a threat of leakage. There are many variables or factors that can influence the hydrodynamics of this retrieval process. They include saltcake porosity; saltwell pumping rate; salt dissolution chemistry; factors that could promote flow channeling (e.g. tank walls, dry wells, inclusions or discontinuities in the saltcake); method of water distribution; plug formation due to crystal formations or accumulation of insoluble solids. A brief literature search indicates that very little experimental data exist on these aspects of saltcake dissolution (Wiersma 1996, 1997). The tests reported here were planned (Herting, 2000) to provide preliminary data and information for planning future, scaled-up tests of the sprinkler method.

  2. The coordinated increased expression of biliverdin reductase and heme oxygenase-2 promotes cardiomyocyte survival: a reductase-based peptide counters β-adrenergic receptor ligand-mediated cardiac dysfunction

    PubMed Central

    Ding, Bo; Gibbs, Peter E. M.; Brookes, Paul S.; Maines, Mahin D.

    2011-01-01

    HO-2 oxidizes heme to CO and biliverdin; the latter is reduced to bilirubin by biliverdin reductase (BVR). In addition, HO-2 is a redox-sensitive K/Ca2-associated protein, and BVR is an S/T/Y kinase. The two enzymes are components of cellular defense mechanisms. This is the first reporting of regulation of HO-2 by BVR and that their coordinated increase in isolated myocytes and intact heart protects against cardiotoxicity of β-adrenergic receptor activation by isoproterenol (ISO). The induction of BVR mRNA, protein, and activity and HO-2 protein was maintained for ≥96 h; increase in HO-1 was modest and transient. In isolated cardiomyocytes, experiments with cycloheximide, proteasome inhibitor MG-132, and siBVR suggested BVR-mediated stabilization of HO-2. In both models, activation of BVR offered protection against the ligand's stimulation of apoptosis. Two human BVR-based peptides known to inhibit and activate the reductase, KKRILHC281 and KYCCSRK296, respectively, were tested in the intact heart. Perfusion of the heart with the inhibitory peptide blocked ISO-mediated BVR activation and augmented apoptosis; conversely, perfusion with the activating peptide inhibited apoptosis. At the functional level, peptide-mediated inhibition of BVR was accompanied by dysfunction of the left ventricle and decrease in HO-2 protein levels. Perfusion of the organ with the activating peptide preserved the left ventricular contractile function and was accompanied by increased levels of HO-2 protein. Finding that BVR and HO-2 levels, myocyte apoptosis, and contractile function of the heart can be modulated by small human BVR-based peptides offers a promising therapeutic approach for treatment of cardiac dysfunctions.—Ding, B., Gibbs, P. E. M., Brookes, P. S., Maines, M. D. The coordinated increased expression of biliverdin reductase and heme oxygenase-2 promotes cardiomyocyte survival; a reductase-based peptide counters β-adrenergic receptor ligand-mediated cardiac dysfunction

  3. Brokenhearts: Dissolution of Romantic Relationships.

    ERIC Educational Resources Information Center

    Meeker, F. B.; La Fong, Carl

    Results of an investigation examining the dissolution of romantic relationships are analyzed. Men and women (N=105) who had ended romantic relationships were surveyed in structured individual interviews. Commonalities and differences in respondents' perceptions of the experience were examined. Specific tests were made of a corollary to Waller's…

  4. Formulations for iron oxides dissolution

    DOEpatents

    Horwitz, Earl P.; Chiarizia, Renato

    1992-01-01

    A mixture of a di- or polyphosphonic acid and a reductant wherein each is present in a sufficient amount to provide a synergistic effect with respect to the dissolution of metal oxides and optionally containing corrosion inhibitors and pH adjusting agents.

  5. Optimizing dissolution dynamic nuclear polarization

    NASA Astrophysics Data System (ADS)

    Bornet, Aurélien; Jannin, Sami

    2016-03-01

    This article is a short review of some of our recent developments in dissolution dynamic nuclear polarization (d-DNP). We present the basic principles of d-DNP, and motivate our choice to step away from conventional approaches. We then introduce a modified d-DNP recipe that can be summed up as follows:

  6. Boehmite Actual Waste Dissolutions Studies

    SciTech Connect

    Snow, Lanee A.; Lumetta, Gregg J.; Fiskum, Sandra K.; Peterson, Reid A.

    2008-07-15

    The U.S. Department of Energy plans to vitrify approximately 60,000 metric tons of high-level waste (HLW) sludge from underground storage tanks at the Hanford Nuclear Reservation. To reduce the volume of HLW requiring treatment, a goal has been set to remove a significant quantity of the aluminum, which comprises nearly 70 percent of the sludge. Aluminum is found in the form of gibbsite, sodium aluminate and boehmite. Gibbsite and sodium aluminate can be easily dissolved by washing the waste stream with caustic. Boehmite, which comprises nearly half of the total aluminum, is more resistant to caustic dissolution and requires higher treatment temperatures and hydroxide concentrations. Samples were taken from four Hanford tanks and homogenized in order to give a sample that is representative of REDOX (Reduction Oxidation process for Pu recovery) sludge solids. Bench scale testing was performed on the homogenized waste to study the dissolution of boehmite. Dissolution was studied at three different hydroxide concentrations, with each concentration being run at three different temperatures. Samples were taken periodically over the 170 hour runs in order to determine leaching kinetics. Results of the dissolution studies and implications for the proposed processing of these wastes will be discussed.

  7. Optimizing dissolution dynamic nuclear polarization.

    PubMed

    Bornet, Aurélien; Jannin, Sami

    2016-03-01

    This article is a short review of some of our recent developments in dissolution dynamic nuclear polarization (d-DNP). We present the basic principles of d-DNP, and motivate our choice to step away from conventional approaches. We then introduce a modified d-DNP recipe that can be summed up as follows. PMID:26920826

  8. Dissolution of nickel ferrite in aqueous solutions containing oxalic acid and ferrous salts

    SciTech Connect

    Figueroa, C.A.; Sileo, E.E.; Morando, P.J.; Blesa, M.A.

    2000-05-15

    The dissolution of nickel ferrite in oxalic acid and in ferrous oxalate-oxalic acid aqueous solution was studied. Nickel ferrite was synthesized by thermal decomposition of a mixed tartrate; the particles were shown to be coated with a thin ferric oxide layer. Dissolution takes place in two stages, the first one corresponding to the dissolution of the ferric oxide outer layer and the second one being the dissolution of Ni{sub 1.06}Fe{sub 1.96}O{sub 4}. The kinetics of dissolution during this first stage is typical of ferric oxides: in oxalic acid, both a ligand-assisted and a redox mechanism operates, whereas in the presence of ferrous ions, redox catalysis leads to a faster dissolution. The rate dependence on both oxalic acid and on ferrous ion is described by the Langmuir-Hinshelwood equation. In the second stage, Langmuir-Hinshelwood kinetics also describes the dissolution of iron and nickel from nickel ferrite. It may be concluded that oxalic acid operates to dissolve iron, and the ensuing disruption of the solid framework accelerates the release of nickel.

  9. DISSOLUTION AND CRYSTALLIZATION OF CALCIUM SULFITE PLATELETS

    EPA Science Inventory

    The paper discusses the dissolution and crystallization of calcium sulfite platelets. The rates of calcium sulfite dissolution and crystallization are important in slurry scrubbing processes for flue gas desulfurization. The rates affect the scrubber solution composition, SO2 abs...

  10. A Role for Antibiotics in Mineral Dissolution and Biofilm Physiology

    NASA Astrophysics Data System (ADS)

    Newman, D. K.

    2002-12-01

    Respiration by bacteria is remarkable due to their ability to use a variety of compounds, including insoluble minerals, as terminal electron acceptors. How bacteria solve the problem of breathing something that is solid is poorly understood, but recent evidence points to the role of redox active natural products in shuttling electrons between microbes and minerals. Given the ubiquity of these substances in natural waters and soils, we must now revisit previous conclusions about whether direct contact between microbes and minerals is necessary to promote reductive mineral dissolution. To explore the degree to which extracellular electron transfer catalyzes important biogeochemical processes, we are studying the types of molecules that function as electron shuttles, including redox active antibiotics. I will discuss my laboratory's current understanding of how interspecies exchange of these molecules promotes mineral dissolution, as well as our emerging hypotheses regarding their function in biofilms.

  11. Dissolution patterns on caramel blocks

    NASA Astrophysics Data System (ADS)

    Cohen, Caroline; Derr, Julien; Berhanu, Michael; Courrech Du Pont, Sylvain

    2015-11-01

    We investigate erosion by dissolution processes. We perform laboratory experiments on hard caramel bodies, which dissolve on a short timescale, compared to geological material such as limestone. We put a block of caramel, tilted from the horizontal, in a water tank without flow. The dissolution syrup, which is denser than pure water, sinks and the flow detaching from the surface creates patterns underneath the caramel block. These patterns result from the coupled dynamics of the flow detaching and the eroding surface and are reminiscent of scallops observed in the walls of phreatic cave passages. We investigate the mechanisms of formation of these structures and their evolution depending on several parameters such as the fluid density or the flow velocity. We finally parallel the formation of patterns on melting iceberg.

  12. Dissolution Kinetics of Alumina Calcine

    SciTech Connect

    Batcheller, Thomas Aquinas

    2001-09-01

    Dissolution kinetics of alumina type non-radioactive calcine was investigated as part of ongoing research that addresses permanent disposal of Idaho High Level Waste (HLW). Calcine waste was produced from the processing of nuclear fuel at the Idaho Nuclear Technology and Engineering Center (INTEC). Acidic radioactive raffinates were solidified at ~500°C in a fluidized bed reactor to form the dry granular calcine material. Several Waste Management alternatives for the calcine are presented in the Idaho High Level Waste Draft EIS. The Separations Alternative addresses the processing of the calcine so that the HLW is ready for removal to a national geological repository by the year 2035. Calcine dissolution is the key front-end unit operation for the separations alternative.

  13. Mass exchange during simultaneous grinding and dissolution

    SciTech Connect

    Aksel'rud, G.A.; Semenishin, E.M.; Kopyt, S.Ya.; Trotskii, V.I.

    1988-03-20

    Extraction of ore components of interest has a number of disadvantages, one of which being low efficiency. Combining the grinding and dissolution steps in one apparatus makes the process more efficient. Adoption of this technology, however, requires theoretical and mathematical studies. This paper reports the kinetics of simultaneous grinding and dissolution of copper-containing minerals. Simultaneous grinding and dissolution accelerated several fold the mass transfer of components of interest in the interaction of malachite and azurite with sulfuric acid solutions. The complete dissolution time was determined by adding the experimental rates of dissolution and abrasion.

  14. Effect of oxalate on the dissolution rates of oligoclase and tremolite

    SciTech Connect

    Mast, M.A.; Drever, J.I.

    1987-09-01

    The effect of oxalate, a strong chelator for Al and other cations, on the dissolution rates of oligoclase feldspar and tremolite amphibole was investigated in a flow-through reactor at 22/sup 0/C. Oxalate at concentrations of 0.5 and 1 mM has essentially no effect on the dissolution rate of tremolite, nor on the steady-state rate of release of Si from oligoclase. The fact that oxalate has no effect on dissolution rate suggests that detachment of Si rather than Al or Mg is the rate-limiting step. At pH 4 and 9, oxalate has no effect on the steady-state rate of release of Al, and dissolution is congruent. At pH 5 and 7, oligoclase dissolution is congruent in the presence of oxalate, but in the absence of oxalate Al is preferentially retained in the solid relative to Si. Large transient spikes of Al or Si are observed when oxalate is added to or removed from the system. The cause of the spikes is unknown; the authors suggest adsorption feldspar surfaces away from sites of active dissolution as a possibility. The rate of dissolution of tremolite is independent of pH over the pH range 2-5, and decreases at higher pH. The rate of dissolution of oligoclase in these experiments was independent of pH over the pH range 4-9. Since the dissolution rate of these minerals is independent of pH and organic ligand concentration, the effect of acid deposition from the atmosphere on the rate of supply of cations from weathering of granitic rocks should be minor.

  15. Dissolution/swelling behavior of cycloolefin polymers in aqueous base

    NASA Astrophysics Data System (ADS)

    Ito, Hiroshi; Allen, Robert D.; Opitz, Juliann; Wallow, Thomas I.; Truong, Hoa D.; Hofer, Donald C.; Varanasi, Pushkara R.; Jordhamo, George M.; Jayaraman, Saikumar; Vicari, Richard

    2000-06-01

    Polycycloolefins prepared by addition polymerization of norbornene derivatives are quite different from hydroxystyrene-based polymers in terms of their interaction with aqueous base. Their dissolution kinetics monitored on a quartz crystal microbalance is not a smooth function of the ratio of the polar to nonpolar functionalities in polymer but abruptly changes from very fast dissolution to massive swelling within a narrow range of composition. The maximum swelling is a function of thickness and the entire film thickness can swell in a few seconds at > 3,000 angstroms/sec or at immeasurably fast rates. The initial concentration of a pendant carboxylic acid in polymer has to be selected to minimize swelling and the concentration of an acid-labile group to induce fast dissolution in the exposed area. Furthermore, swelling which occurs in the partially- exposed regions must be minimized by incorporating a third monomer unit or by adding a dissolution modifying agent (DMA) such as t-butyl cholate. However, the function of DMA which is also acid-labile is quite complex; depending on the matrix polymer composition and its dissolution/swelling behavior, DMA could function as a swelling suppressor or promoter and a carboxylic acid generated by acidolysis of DMA as a dissolution or swelling promoter. Photochemically generated sulfonic acid could also affect the dissolution/swelling behavior. Base hydrolysis of anhydride during development is controlled by the polarity (carboxylic acid concentration) in polymer film, which has been demonstrated in an unequivocal fashion by IR spectroscopy under the condition strongly mimicking the development process and thus could boost development contrast but could hurt performance as well. Thus, incorporation of carboxylic acid in the form of methacrylic acid, for example, in radical copolymerization of norbornene with maleic anhydride must be handled carefully as it would increase the susceptibility of the anhydride hydrolysis and could

  16. Kinetics and mechanism of As2S3(am) dissolution under N2.

    PubMed

    Floroiu, Ruxandra M; Davis, Allen P; Torrents, Alba

    2004-02-15

    Arsenic presence in ground and surface waters poses a risk to ecosystem and human health; consequently, detailed information is needed on the factors that govern arsenic fate and transport in the environment. As2S3 is commonly found in hydrothermal and geothermal environments, hot springs, and in gold deposits, but the dominant reaction pathways and rates of dissolution are not well understood. The objectives of this research were as follows: (1) to understand the effect of pH on the dissolution of As2S3 under nitrogen-purged conditions, (2) to examine arsenic and sulfur speciation upon dissolution, and (3) to develop kinetic data for modeling the dissolution of As2S3. Studies were performed in batch reactors for a range of pH from 2 to 8. Results indicate that As2S3 dissolution is kinetically slow but very much dependent on pH. A J-shaped dissolution rate versus pH curve is described by the following expression: rate (microM h(-1)) = 0.9 + 610[OH-](0.3). Rate trends seem to follow As2S3 solubility as a function of pH. A surface dissolution mechanism is proposed, leading to dissolved As(III) species. Results indicate that under anaerobic conditions, an increase in pH will act to promote the arsenic sulfide dissolution rate. PMID:14998015

  17. Plagioclase dissolution during CO₂-SO₂ cosequestration: effects of sulfate.

    PubMed

    Min, Yujia; Kubicki, James D; Jun, Young-Shin

    2015-02-01

    Geologic CO2 sequestration (GCS) is one of the most promising methods to mitigate the adverse impacts of global climate change. The performance of GCS can be affected by mineral dissolution and precipitation induced by injected CO2. Cosequestration with acidic gas such as SO2 can reduce the high cost of GCS, but it will increase the sulfate's concentration in GCS sites, where sulfate can potentially affect plagioclase dissolution/precipitation. This work investigated the effects of 0.05 M sulfate on plagioclase (anorthite) dissolution and subsequent mineral precipitation at 90 °C, 100 atm CO2, and 1 M NaCl, conditions relevant to GCS sites. The adsorption of sulfate on anorthite, a Ca-rich plagioclase, was examined using attenuated total reflectance Fourier-transform infrared spectroscopy and then simulated using density functional theory calculations. We found that the dissolution rate of anorthite was enhanced by a factor of 1.36 by the formation of inner-sphere monodentate complexes between sulfate and the aluminum sites on anorthite surfaces. However, this effect was almost completely suppressed in the presence of 0.01 M oxalate, an organic ligand that can exist in GCS sites. Interestingly, sulfate also inhibited the formation of secondary mineral precipitation through the formation of aluminum-sulfate complexes in the aqueous phase. This work, for the first time, reports the surface complexation between sulfate and plagioclase that can occur in GCS sites. The results provide new insights for obtaining scientific guidelines for the proper amount of SO2 coinjection and finally for evaluating the economic efficiency and environmental safety of GCS operations. PMID:25549263

  18. Enhanced dissolution of cinnabar (mercuric sulfide) by dissolved organic matter isolated from the Florida Everglades

    SciTech Connect

    Ravichandran, M.; Ryan, J.N.; Aiken, G.R.; Reddy, M.M.

    1998-11-01

    Organic matter isolated from the Florida Everglades caused a dramatic increase in mercury release from cinnabar (HgS), a solid with limited solubility. Hydrophobic (a mixture of both humic and fulvic) acids dissolved more mercury than hydrophilic acids and other nonacid fractions of dissolved organic matter (DOM). Cinnabar dissolution by isolated organic matter and natural water samples was inhibited by cations such as Ca{sup 2+}. Dissolution was independent of oxygen content in experimental solutions. Dissolution experiments conducted in Dl water had no detectable dissolved mercury. The presence of various inorganic (chloride, sulfate, or sulfide) and organic ligands (salicylic acid, acetic acid, EDTA, or cysteine) did not enhance the dissolution of mercury from the mineral. Aromatic carbon content in the isolates correlated positively with enhanced cinnabar dissolution. {zeta}-potential measurements indicated sorption of negatively charged organic matter to the negatively charged cinnabar at pH 6.0. Possible mechanisms of dissolution include surface complexation of mercury and oxidation of surface sulfur species by the organic matter.

  19. DISSOLUTION OF NEPTUNIUM OXIDE RESIDUES

    SciTech Connect

    Kyser, E

    2009-01-12

    This report describes the development of a dissolution flowsheet for neptunium (Np) oxide (NpO{sub 2}) residues (i.e., various NpO{sub 2} sources, HB-Line glovebox sweepings, and Savannah River National Laboratory (SRNL) thermogravimetric analysis samples). Samples of each type of materials proposed for processing were dissolved in a closed laboratory apparatus and the rate and total quantity of off-gas were measured. Samples of the off-gas were also analyzed. The quantity and type of solids remaining (when visible) were determined after post-dissolution filtration of the solution. Recommended conditions for dissolution of the NpO{sub 2} residues are: Solution Matrix and Loading: {approx}50 g Np/L (750 g Np in 15 L of dissolver solution), using 8 M nitric acid (HNO{sub 3}), 0.025 M potassium fluoride (KF) at greater than 100 C for at least 3 hours. Off-gas: Analysis of the off-gas indicated nitric oxide (NO), nitrogen dioxide (NO{sub 2}) and nitrous oxide (N{sub 2}O) as the only identified components. No hydrogen (H{sub 2}) was detected. The molar ratio of off-gas produced per mole of Np dissolved ranged from 0.25 to 0.4 moles of gas per mole of Np dissolved. A peak off-gas rate of {approx}0.1 scfm/kg bulk oxide was observed. Residual Solids: Pure NpO{sub 2} dissolved with little or no residue with the proposed flowsheet but the NpCo and both sweepings samples left visible solid residue after dissolution. For the NpCo and Part II Sweepings samples the residue amounted to {approx}1% of the initial material, but for the Part I Sweepings sample, the residue amounted to {approx}8 % of the initial material. These residues contained primarily aluminum (Al) and silicon (Si) compounds that did not completely dissolve under the flowsheet conditions. The residues from both sweepings samples contained minor amounts of plutonium (Pu) particles. Overall, the undissolved Np and Pu particles in the residues were a very small fraction of the total solids.

  20. Physicochemical Hydrodynamics of NAPL Dissolution

    NASA Astrophysics Data System (ADS)

    Doss, S. K.; Ezzedine, S.; Ziagos, J. P.; Hoffman, F.; Gelinas, R. J.

    2001-05-01

    Determining the continually changing interface between the non-aqueous phase liquid (NAPL) and aqueous phase liquid (APL) phases, and the physical and chemical processes by which mass is transferred across the interface is critical to the understanding of NAPL dissolution. Most researchers, however, address only the flux of mass from NAPL into the aqueous phase and the subsequent migration of the dissolved contaminants; little effort has been made to track the NAPL/APL interface. While it is crucial to have an accurate account of mass flux from NAPL to APL in order to design successful remediation strategies, the absence of rigor in tracking the NAPL/APL boundary interface makes such mass flux estimates less reliable. Our studies account for the moving NAPL/APL boundary interface. We introduce a new approach in developing non-linearly coupled flow and transport equations in order to include specific description of chemical dissolution processes.The governing NAPL/APL evolution equations were formulated along principles similar to the Stefan Problem of moving interfaces. Essentially, the diffusion coefficient is allowed to vary in unison with the concentration but with a near discontinuity at the threshold of the NAPL solubility limit. Below the solubility limit, the diffusion takes on its customary value throughout the aqueous phase. Meanwhile, very small values are assigned to the diffusion coefficient within the non-aqueous phase. Along the NAPL/APL interface, the diffusion coefficient is given some transition shape function, which is ultimately determined by calibration to laboratory experiments. In addition to accounting for the continuous erosion of NAPL/APL interface due to the dissolution, blobs of NAPL are allowed to diffuse and move, rather freely, under the influence of prevailing physical forces. Our numerical simulations were obtained using Adaptive Grid, Galerkin Finite Elements technique to solve the coupled flow and transport equations simultaneously

  1. Optimizing dissolution dynamic nuclear polarization

    NASA Astrophysics Data System (ADS)

    Bornet, Aurélien; Jannin, Sami

    2016-03-01

    This article is a short review of some of our recent developments in dissolution dynamic nuclear polarization (d-DNP). We present the basic principles of d-DNP, and motivate our choice to step away from conventional approaches. We then introduce a modified d-DNP recipe that can be summed up as follows: Using broad line polarizing agents to efficiently polarize 1H spins. Increasing the magnetic field to 6.7 T and above. Applying microwave frequency modulation. Applying 1H-13C cross polarization. Transferring hyperpolarized solution through a magnetic tunnel.

  2. Plutonium dioxide dissolution in glass

    SciTech Connect

    Vienna, J.D.; Alexander, D.L.; Li, Hong

    1996-09-01

    In the aftermath of the Cold War, the U.S. Department of Energy`s (DOE) Office of Fissile Materials Disposition (OFMD) is charged with providing technical support for evaluation of disposition options for excess fissile materials manufactured for the nation`s defense. One option being considered for the disposition of excess plutonium (Pu) is immobilization by vitrification. The vitrification option entails immobilizing Pu in a host glass and waste package that are criticality-safe (immune to nuclear criticality), proliferation-resistant, and environmentally acceptable for long-term storage or disposal. To prove the technical and economic feasibility of candidate vitrification options it is necessary to demonstrate that PuO{sub 2} feedstock can be dissolved in glass in sufficient quantity. The OFMD immobilization program has set a Pu solubility goal of 10 wt% in glass. The life cycle cost of the vitrification options are strongly influenced by the rate at which PUO{sub 2} dissolves in glass. The total number of process lines needed for vitrification of 50 t of Pu in 10 years is directly dependent upon the time required for Pu dissolution in glass. The objective of this joint Pacific Northwest National Laboratory (PNNL) - Savannah River Technology Center (SRTC) study was to demonstrate a high Pu solubility in glass and to identify on a rough scale the time required for Pu dissolution in the glass. This study was conducted using a lanthanide borosilicate (LaBS) glass composition designed at the SRTC for the vitrification of actinides.

  3. Effects of Natural Organic Matter Properties on the Dissolution Kinetics of Zinc Oxide Nanoparticles.

    PubMed

    Jiang, Chuanjia; Aiken, George R; Hsu-Kim, Heileen

    2015-10-01

    The dissolution of zinc oxide (ZnO) nanoparticles (NPs) is a key step of controlling their environmental fate, bioavailability, and toxicity. Rates of dissolution often depend upon factors such as interactions of NPs with natural organic matter (NOM). We examined the effects of 16 different NOM isolates on the dissolution kinetics of ZnO NPs in buffered potassium chloride solution using anodic stripping voltammetry to directly measure dissolved zinc concentrations. The observed dissolution rate constants (kobs) and dissolved zinc concentrations at equilibrium increased linearly with NOM concentration (from 0 to 40 mg C L(-1)) for Suwannee River humic and fulvic acids and Pony Lake fulvic acid. When dissolution rates were compared for the 16 NOM isolates, kobs was positively correlated with certain properties of NOM, including specific ultraviolet absorbance (SUVA), aromatic and carbonyl carbon contents, and molecular weight. Dissolution rate constants were negatively correlated to hydrogen/carbon ratio and aliphatic carbon content. The observed correlations indicate that aromatic carbon content is a key factor in determining the rate of NOM-promoted dissolution of ZnO NPs. The findings of this study facilitate a better understanding of the fate of ZnO NPs in organic-rich aquatic environments and highlight SUVA as a facile and useful indicator of NOM interactions with metal-based nanoparticles. PMID:26355264

  4. DISSOLUTION OF LANTHANUM FLUORIDE PRECIPITATES

    DOEpatents

    Fries, B.A.

    1959-11-10

    A plutonium separatory ore concentration procedure involving the use of a fluoride type of carrier is presented. An improvement is given in the derivation step in the process for plutonium recovery by carrier precipitation of plutonium values from solution with a lanthanum fluoride carrier precipitate and subsequent derivation from the resulting plutonium bearing carrier precipitate of an aqueous acidic plutonium-containing solution. The carrier precipitate is contacted with a concentrated aqueous solution of potassium carbonate to effect dissolution therein of at least a part of the precipitate, including the plutonium values. Any remaining precipitate is separated from the resulting solution and dissolves in an aqueous solution containing at least 20% by weight of potassium carbonate. The reacting solutions are combined, and an alkali metal hydroxide added to a concentration of at least 2N to precipitate lanthanum hydroxide concomitantly carrying plutonium values.

  5. Mechanism of Non-Steady State Dissolution of Goethite in the Presence of Siderophores

    NASA Astrophysics Data System (ADS)

    Reichard, P. U.; Kretzschmar, R.; Kraemer, S. M.

    2003-12-01

    Iron is an essential micronutrient for almost all known organisms. Bacteria, fungi, and graminaceous plants are capable of exuding siderophores as part of an iron acquisition strategy. The production of these strong iron chelating ligands is induced by iron limited conditions. Grasses under iron stress, for example, exude phytosiderophores into the rhizosphere in a special diurnal rhythm (Roemheld and Marschner 1986). A few hours after sunrise the exudation starts, culminates around noon and is shut down again until about 4 hours after noon. The phytosiderophores diffuse into the rhizosphere (Marschner et al. 1986) and are passively back transported to the plants by advective flow induced by high transpiration around noon. Despite a fairly short residence time of the phytosiderophores in the rhizosphere, it is a very effective strategy for iron acquisition. To investigate the effect of such pulse inputs of siderophores on iron acquisition, we studied the dissolution mechanism of goethite (alpha-FeOOH), a mineral phase common in soils, under non-steady state conditions. In consideration of the chemical complexity of the rhizosphere, we also investigated the effect of other organic ligands commonly found in the rhizosphere (e. g. oxalate) on the dissolution kinetics. The dissolution experiments were conducted in batch reactors with a constant goethite solids concentration of 2.5 g/l, an ionic strength of 0.01 M, a pH of 6 and 100 microM oxalate. To induce non-steady state conditions, 3 mM phytosiderophores were added to a batch after the goethite-oxalate suspension reacted for a certain time period. Before the siderophore was added to the goethite-oxalate suspension, no dissolution of iron was observed. But, with the addition of the siderophore, a high rate was observed for the iron mobilization under these non-steady state conditions that subsequently was followed by a slow steady state dissolution rate. The results of these non-steady state experiments are very

  6. 25 CFR 11.606 - Dissolution proceedings.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... marriage may initiate dissolution proceedings. (b) If a proceeding is commenced by one of the parties, the... proceeding for dissolution of marriage or legal separation shall allege that the marriage is irretrievably... under the jurisdiction of the court of each party; (2) The date of the marriage and the place at...

  7. 25 CFR 11.606 - Dissolution proceedings.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... marriage may initiate dissolution proceedings. (b) If a proceeding is commenced by one of the parties, the... proceeding for dissolution of marriage or legal separation shall allege that the marriage is irretrievably... under the jurisdiction of the court of each party; (2) The date of the marriage and the place at...

  8. Emotional and Cognitive Coping in Relationship Dissolution

    ERIC Educational Resources Information Center

    Wrape, Elizabeth R.; Jenkins, Sharon Rae; Callahan, Jennifer L.; Nowlin, Rachel B.

    2016-01-01

    Dissolution of a romantic relationship can adversely affect functioning among college students and represents one primary reason for seeking campus counseling. This study examined the associations among common coping strategies and distress following relationship dissolution. Avoidance and repetitive negative thinking (RNT) were significantly…

  9. CALCIUM CARBONATE DISSOLUTION RATE IN LIMESTONE CONTRACTORS

    EPA Science Inventory

    The rate of carbonate mineral dissolution from limestone was studied using a rotating disk apparatus and samples of limestone of varied composition. he purpose of this study was to determine the effect of limestone composition on the kinetics of carbonate mineral dissolution. he ...

  10. Thermal dissolution of solid fossil fuels

    SciTech Connect

    E.G. Gorlov

    2007-10-15

    The use of oil shales and coals in the processes of thermal dissolution is considered. It is shown that thermal dissolution is a mode of liquefaction of solid fossil fuels and can be used both independently and in combination with liquefaction of coals and processing of heavy petroleum residues.

  11. Stirring effect on kaolinite dissolution rate

    NASA Astrophysics Data System (ADS)

    Metz, Volker; Ganor, Jiwchar

    2001-10-01

    Experiments were carried out measuring kaolinite dissolution rates using stirred and nonstirred flow-through reactors at pHs 2 to 4 and temperatures of 25°C, 50°C, and 70°C. The results show an increase of kaolinite dissolution rate with increasing stirring speed. The stirring effect is reversible, i.e., as the stirring slows down the dissolution rate decreases. The effect of stirring speed on kaolinite dissolution rate is higher at 25°C than at 50°C and 70°C and at pH 4 than at pHs 2 and 3. It is suggested that fine kaolinite particles are formed as a result of stirring-induced spalling or abrasion of kaolinite. These very fine particles have an increased ratio of reactive surface area to specific surface area, which results in enhancement of kaolinite dissolution rate. A balance between production and dissolution of the fine particles explains both the reversibility and the temperature and pH dependence of the stirring effect. Since the stirring effect on kaolinite dissolution rate varies with temperature and pH, measurement of kinetic parameters such as activation energy may be influenced by stirring. Therefore, standard use of nonagitated reaction vessels for kinetic experiments of mineral dissolution and precipitation is recommended, at least for slow reactions that are surface controlled.

  12. Nanosizing of drugs: Effect on dissolution rate

    PubMed Central

    Dizaj, S. Maleki; Vazifehasl, Zh.; Salatin, S.; Adibkia, Kh.; Javadzadeh, Y.

    2015-01-01

    The solubility, bioavailability and dissolution rate of drugs are important parameters for achieving in vivo efficiency. The bioavailability of orally administered drugs depends on their ability to be absorbed via gastrointestinal tract. For drugs belonging to Class II of pharmaceutical classification, the absorption process is limited by drug dissolution rate in gastrointestinal media. Therefore, enhancement of the dissolution rate of these drugs will present improved bioavailability. So far several techniques such as physical and chemical modifications, changing in crystal habits, solid dispersion, complexation, solubilization and liquisolid method have been used to enhance the dissolution rate of poorly water soluble drugs. It seems that improvement of the solubility properties ofpoorly water soluble drugscan translate to an increase in their bioavailability. Nowadays nanotechnology offers various approaches in the area of dissolution enhancement of low aqueous soluble drugs. Nanosizing of drugs in the form of nanoparticles, nanocrystals or nanosuspensions not requiring expensive facilities and equipment or complicated processes may be applied as simple methods to increase the dissolution rate of poorly water soluble drugs. In this article, we attempted to review the effects of nanosizing on improving the dissolution rate of poorly aqueous soluble drugs. According to the reviewed literature, by reduction of drug particle size into nanometer size the total effective surface area is increased and thereby dissolution rate would be enhanced. Additionally, reduction of particle size leads to reduction of the diffusion layer thickness surrounding the drug particles resulting in the increment of the concentration gradient. Each of these process leads to improved bioavailability. PMID:26487886

  13. CALCIUM CARBONATE DISSOLUTION RATE IN LIMESTONE CONTACTORS

    EPA Science Inventory

    The rate of carbonate mineral dissolution from limestone was studied using a rotating disk apparatus and samples of limestone of varied composition. The purpose of this study was to determine the effect of limestone composition on the kinetics of carbonate mineral dissolution. Th...

  14. 25 CFR 11.606 - Dissolution proceedings.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... marriage may initiate dissolution proceedings. (b) If a proceeding is commenced by one of the parties, the... proceeding for dissolution of marriage or legal separation shall allege that the marriage is irretrievably... under the jurisdiction of the court of each party; (2) The date of the marriage and the place at...

  15. 25 CFR 11.606 - Dissolution proceedings.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... marriage may initiate dissolution proceedings. (b) If a proceeding is commenced by one of the parties, the... proceeding for dissolution of marriage or legal separation shall allege that the marriage is irretrievably... under the jurisdiction of the court of each party; (2) The date of the marriage and the place at...

  16. 25 CFR 11.606 - Dissolution proceedings.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... marriage may initiate dissolution proceedings. (b) If a proceeding is commenced by one of the parties, the... proceeding for dissolution of marriage or legal separation shall allege that the marriage is irretrievably... under the jurisdiction of the court of each party; (2) The date of the marriage and the place at...

  17. Dissolution enthalpies of cellulose in ionic liquids.

    PubMed

    Parviainen, Helena; Parviainen, Arno; Virtanen, Tommi; Kilpeläinen, Ilkka; Ahvenainen, Patrik; Serimaa, Ritva; Grönqvist, Stina; Maloney, Thaddeus; Maunu, Sirkka Liisa

    2014-11-26

    In this work, interactions between cellulose and ionic liquids were studied calorimetrically and by optical microscopy. Two novel ionic liquids (1,5-Diazabicyclo[4.3.0]non-5-enium propionate and N-methyl-1,5-diazabicyclo[4.3.0]non-5-enium dimethyl phosphate) and 1-ethyl-3-methylimidazolium acetate-water mixtures were used as solvents. Optical microscopy served in finding the extent of dissolution and identifying the dissolution pattern of the cellulose sample. Calorimetric studies identified a peak relating to dissolution of cellulose in solvent. The transition did, however, not indicate complete dissolution, but rather dissolution inside fibre or fibrils. This method was used to study differences between four cellulose samples with different pretreatment or origins. PMID:25256460

  18. A General Ligand Design for Gold Catalysis allowing Ligand-Directed Anti Nucleophilic Attack of Alkynes

    PubMed Central

    Wang, Yanzhao; Wang, Zhixun; Li, Yuxue; Wu, Gongde; Cao, Zheng; Zhang, Liming

    2014-01-01

    Most homogenous gold catalyses demand ≥0.5 mol % catalyst loading. Due to the high cost of gold, these reactions are unlikely to be applicable in medium or large scale applications. Here we disclose a novel ligand design based on the privileged biphenyl-2-phosphine framework that offers a potentially general approach to dramatically lowering catalyst loading. In this design, an amide group at the 3’ position of the ligand framework directs and promotes nucleophilic attack at the ligand gold complex-activated alkyne, which is unprecedented in homogeneous gold catalysis considering the spatial challenge of using ligand to reach antiapproaching nucleophile in a linear P-Au-alkyne centroid structure. With such a ligand, the gold(I) complex becomes highly efficient in catalyzing acid addition to alkynes, with a turnover number up to 99,000. Density functional theory calculations support the role of the amide moiety in directing the attack of carboxylic acid via hydrogen bonding. PMID:24704803

  19. Variation of crystal dissolution rate based on a dissolution stepwave model.

    PubMed

    Lasaga, A C; Luttge, A

    2001-03-23

    A formulation based on defect-generated dissolution stepwaves of the variation of dissolution rate with the degree of undersaturation is validated by near-atomic-scale observations of surfaces, Monte Carlo simulations, and experimental bulk dissolution rates. The dissolution stepwaves emanating from etch pits provide a train of steps similar to those of a spiral but with different behavior. Their role in accounting for the bulk dissolution rate of crystals provides a conceptual framework for mineral dissolution far from equilibrium. Furthermore, the law extends research to conditions closer to equilibrium and predicts a nonlinear decrease in the rate of dissolution as equilibrium is approached, which has implications for understanding artificial and natural processes involving solid-fluid reactions. PMID:11264534

  20. Surface properties, solubility and dissolution kinetics of bamboo phytoliths

    NASA Astrophysics Data System (ADS)

    Fraysse, Fabrice; Pokrovsky, Oleg S.; Schott, Jacques; Meunier, Jean-Dominique

    2006-04-01

    Although phytoliths, constituted mainly by micrometric opal, exhibit an important control on silicon cycle in superficial continental environments, their thermodynamic properties and reactivity in aqueous solution are still poorly known. In this work, we determined the solubility and dissolution rates of bamboo phytoliths collected in the Réunion Island and characterized their surface properties via electrophoretic measurements and potentiometric titrations in a wide range of pH. The solubility product of "soil" phytoliths ( pKsp0=2.74 at 25 °C) is equal to that of vitreous silica and is 17 times higher than that of quartz. Similarly, the enthalpy of phytoliths dissolution reaction (ΔHr25-80°C=10.85kJ/mol) is close to that of amorphous silica but is significantly lower than the enthalpy of quartz dissolution. Electrophoretic measurements yield isoelectric point pH IEP = 1.2 ± 0.1 and 2.5 ± 0.2 for "soil" (native) and "heated" (450 °C heating to remove organic matter) phytoliths, respectively. Surface acid-base titrations allowed generation of a 2-p K surface complexation model. Phytoliths dissolution rates, measured in mixed-flow reactors at far from equilibrium conditions at 2 ⩽ pH ⩽ 12, were found to be intermediate between those of quartz and vitreous silica. The dissolution rate dependence on pH was modeled within the concept of surface coordination theory using the equation: R=k1·{>SiOH2+}n+k2·{>SiOH0}+k3·{>SiO-}m, where {> i} stands for the concentration of the surface species present at the SiO 2-H 2O interface, ki are the rate constants of the three parallel reactions and n and m represent the order of the proton- and hydroxy-promoted reactions, respectively. It follows from the results of this study that phytoliths dissolution rates exhibit a minimum at pH ˜ 3. This can explain their good preservation in the acidic soil horizons of Réunion Island. In terms of silicon biogeochemical cycle, phytoliths represent a large buffering reservoir

  1. Molecular dynamic simulations of ocular tablet dissolution.

    PubMed

    Ru, Qian; Fadda, Hala M; Li, Chung; Paul, Daniel; Khaw, Peng T; Brocchini, Steve; Zloh, Mire

    2013-11-25

    Small tablets for implantation into the subconjunctival space in the eye are being developed to inhibit scarring after glaucoma filtration surgery (GFS). There is a need to evaluate drug dissolution at the molecular level to determine how the chemical structure of the active may correlate with dissolution in the nonsink conditions of the conjunctival space. We conducted molecular dynamics simulations to study the dissolution process of tablets derived from two drugs that can inhibit fibrosis after GFS, 5-fluorouracil (5-FU) and the matrix metalloprotease inhibitor (MMPi), ilomastat. The dissolution was simulated in the presence of simple point charge (SPC) water molecules, and the liquid turnover of the aqueous humor in the subconjunctival space was simulated by removal of the dissolved drug molecules at regular intervals and replacement by new water molecules. At the end of the simulation, the total molecular solvent accessible surface area of 5-FU tablets increased by 60 times more than that of ilomastat as a result of tablet swelling and release of molecules into solution. The tablet dissolution pattern shown in our molecular dynamic simulations tends to correlate with experimental release profiles. This work indicates that a series of molecular dynamic simulations can be used to predict the influence of the molecular properties of a drug on its dissolution profile and could be useful during preformulation where sufficient amounts of the drug are not always available to perform dissolution studies. PMID:24073784

  2. Metal-ligand cooperation.

    PubMed

    Khusnutdinova, Julia R; Milstein, David

    2015-10-12

    Metal-ligand cooperation (MLC) has become an important concept in catalysis by transition metal complexes both in synthetic and biological systems. MLC implies that both the metal and the ligand are directly involved in bond activation processes, by contrast to "classical" transition metal catalysis where the ligand (e.g. phosphine) acts as a spectator, while all key transformations occur at the metal center. In this Review, we will discuss examples of MLC in which 1) both the metal and the ligand are chemically modified during bond activation and 2) bond activation results in immediate changes in the 1st coordination sphere involving the cooperating ligand, even if the reactive center at the ligand is not directly bound to the metal (e.g. via tautomerization). The role of MLC in enabling effective catalysis as well as in catalyst deactivation reactions will be discussed. PMID:26436516

  3. Microbial extracellular polysaccharides and plagioclase dissolution

    SciTech Connect

    Welch, S.A.; Barker, W.W.; Banfield, J.F.

    1999-05-01

    Bytownite feldspar was dissolved in batch reactors in solutions of starch (glucose polymer), gum xanthan (glucose, mannose, glucuronic acid), pectin (poly-galacturonic acid), and four alginates (mannuronic and guluronic acid) with a range of molecular weights (low, medium, high and uncharacterized) to evaluate the effect of extracellular microbial polymers on mineral dissolution rates. Solutions were analyzed for dissolved Si and Al as an indicator of feldspar dissolution. At neutral pH, feldspar dissolution was inhibited by five of the acid polysaccharides, gum xanthan, pectin, alginate low, alginate medium, alginate high, compared to an organic-free control. An uncharacterized alginate substantially enhanced both Si and Al release from the feldspar. Starch, a neutral polysaccharide, had no apparent effect. Under mildly acidic conditions, initial pH {approx} 4, all of the polymers enhanced feldspar dissolution compared to the inorganic controls. Si release from feldspar in starch solution exceeded the control by a factor of three. Pectin and gum xanthan increased feldspar dissolution by a factor of 10, and the alginates enhanced feldspar dissolution by a factor of 50 to 100. Si and Al concentrations increased with time, even though solutions were supersaturated with respect to several possible secondary phases. Under acidic conditions, initial pH {approx} 3, below the pK{sub a} of the carboxylic acid groups, dissolution rates increased, but the relative increase due to the polysaccharides is lower, approximately a factor of two to ten. Microbial extracellular polymers play a complex role in mineral weathering. Polymers appear to inhibit dissolution under some conditions, possibly by irreversibly binding to the mineral surfaces. The extracellular polysaccharides can also enhance dissolution by providing protons and complexing with ions in solution.

  4. 10 CFR 960.4-2-6 - Dissolution.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... host rock within the site was subject to significant dissolution during the Quaternary Period. (c..., dissolution cavities, significant volumetric reduction of the host rock or surrounding strata, or...

  5. Bifunctional crosslinking ligands for transthyretin

    PubMed Central

    Mangione, P. Patrizia; Deroo, Stéphanie; Ellmerich, Stephan; Bellotti, Vittorio; Kolstoe, Simon; Wood, Stephen P.; Robinson, Carol V.; Smith, Martin D.; Tennent, Glenys A.; Broadbridge, Robert J.; Council, Claire E.; Thurston, Joanne R.; Steadman, Victoria A.; Vong, Antonio K.; Swain, Christopher J.; Pepys, Mark B.; Taylor, Graham W.

    2015-01-01

    Wild-type and variant forms of transthyretin (TTR), a normal plasma protein, are amyloidogenic and can be deposited in the tissues as amyloid fibrils causing acquired and hereditary systemic TTR amyloidosis, a debilitating and usually fatal disease. Reduction in the abundance of amyloid fibril precursor proteins arrests amyloid deposition and halts disease progression in all forms of amyloidosis including TTR type. Our previous demonstration that circulating serum amyloid P component (SAP) is efficiently depleted by administration of a specific small molecule ligand compound, that non-covalently crosslinks pairs of SAP molecules, suggested that TTR may be also amenable to this approach. We first confirmed that chemically crosslinked human TTR is rapidly cleared from the circulation in mice. In order to crosslink pairs of TTR molecules, promote their accelerated clearance and thus therapeutically deplete plasma TTR, we prepared a range of bivalent specific ligands for the thyroxine binding sites of TTR. Non-covalently bound human TTR–ligand complexes were formed that were stable in vitro and in vivo, but they were not cleared from the plasma of mice in vivo more rapidly than native uncomplexed TTR. Therapeutic depletion of circulating TTR will require additional mechanisms. PMID:26400472

  6. In situ Characterization of Photoresist Dissolution

    NASA Astrophysics Data System (ADS)

    Itani, Toshiro; Santillan, Julius Joseph

    2010-06-01

    The dissolution process plays an important role in optimizing photoresist materials and processes for next-generation lithographic technologies. In this paper, we describe the application of high-speed atomic force microscopy for in situ analysis and characterization of photoresist dissolution. In particular, the physical changes in an exposed extreme ultraviolet (EUV) photoresist film are analyzed in real time - before, during, and after the development process. In this initial work, we report the dissolution characteristics of an EUV-exposed poly(4-hyrdroxystyrene)-based polymer resist processed with a tetramethylammonium hydroxide developer solution.

  7. Experimental alkali feldspar dissolution at 100 degree C by carboxylic acids and their anions

    SciTech Connect

    Stoessell, R.K. ); Pittman, E.D. )

    1990-05-01

    Feldspar dissolution will enhance sandstone porosity if the released aluminum can be transported away in the subsurface waters. Carboxylic acids have been proposed to provide hydrogen ions to promote dissolution and anions to complex aqueous aluminum to keep it in solution. However, the hydrogen ions should react quickly following acid generation in source beds, leaving monocarboxylic anions with lesser amounts of dicarboxylic acids and their anions on feldspar dissolution and the apparent complexing of aluminum in solution. Two-week dissolution experiments of alkali feldspar were run at 100{degree}C and 300 bars in acetic acid, oxalic acid, and sodium salt solutions of chloride, acetate, propionate, oxalate, and malonate. Extrapolation of the results, to reservoir conditions during sandstone diagenesis, implies that concentrations of aluminum-organic complexes are not significant for acetate and propionate and are possibly significant for oxalate and malonate, depending upon fluid compositions. Propionate appeared to inhibit feldspar dissolution and hence might decrease secondary porosity formation. Increases in aluminum concentrations in the presence of oxalic and acetic acid solutions appear to be due to enhanced dissolution kinetics and greater aluminum solubility under low-pH conditions. Such low-pH fluids are generally absent in subsurface reservoirs, making this an unlikely mechanism for enhancing porosity. Furthermore, the observed thermal instability of oxalate and malonate anions explains their general low concentrations in subsurface fluids which limits their aluminum complexing potential in reservoirs during late diagenesis.

  8. Differential dissolution susceptibility of Paleocene foraminiferal assemblage from Farafra Oasis, Egypt

    NASA Astrophysics Data System (ADS)

    Orabi, Orabi H.; Zaky, Amr S.

    2016-01-01

    Four inferred carbonate dissolution intervals are recognized at North Gunna section within the Dakhla and Esna formations (Paleocene) of the Farafra Oasis of Egypt as the following: 1) at the Danian/Selandian boundary (P3a/P3b), 2) at the upper part of Acarinina soldadoensis/Globanomalina pseudomenardii Subzone (P4c), 3) at the upper two third of the Morozvella velascoenis P5 Biozone and 4) at the Paleocene/Eocene boundary of Morozovella velascoensis/Morozovella aragonensis-Morozovelia subbotinae (P5/E5), where the P/E boundary is marked by major hiatus. The essential indicators of dissolution within the four intervals samples are low P/B ratios, high relative abundance of the agglutinated taxa, high relative abundance of calcareous taxa resistant to dissolution, especially Lenticulin, Cibicidoides and Anomalinoides and low relative abundance of susceptible calcareous taxa, such as unilocular, uniserial and biserial taxa for the benthics and non-muricate taxa for the planktonic, associated with the high percentage of organic carbon. The probably factors may contribute to the dissolution of planktonic foraminiferal tests in the four intervals of dissolution at the Farafra Oasis is that acidity produced by the degradation of organic matter promotes dissolution in sediment pore waters.

  9. The effect of surfactants on the dissolution behavior of amorphous formulations.

    PubMed

    Mah, Pei T; Peltonen, Leena; Novakovic, Dunja; Rades, Thomas; Strachan, Clare J; Laaksonen, Timo

    2016-06-01

    The optimal design of oral amorphous formulations benefits from the use of excipients to maintain drug supersaturation and thus ensures adequate absorption during intestinal transit. The use of surfactants for the maintenance of supersaturation in amorphous formulations has not been investigated in detail. The main aim of this study was to investigate the effect of surfactant on the dissolution behavior of neat amorphous drug and binary polymer based solid dispersion. Indomethacin was used as the model drug and the surfactants studied were polysorbate 80 and poloxamer 407. The presence of surfactants (alone or in combination with polymers) in the buffer was detrimental to the dissolution of neat amorphous indomethacin, suggesting that the surfactants promoted the crystallization of neat amorphous indomethacin. In contrast, the presence of surfactants (0.01% w/v) in the buffer resulted in a significant improvement on the dissolution behavior of binary polymer based solid dispersion. Incorporating the surfactant to the formulation to form ternary solid dispersion adversely affected the dissolution behavior. In conclusion, the use of surfactants (as wetting or solubilization agents) in dissolution studies of neat amorphous drugs requires prudent consideration. The design of amorphous formulations with optimal dissolution performance requires the appropriate selection of a combination of excipients and consideration of the method of introducing the excipients. PMID:26955750

  10. Dissolution and Separation of Aluminum and Aluminosilicates

    DOE PAGESBeta

    McFarlane, Joanna; Benker, Dennis; DePaoli, David W.; Felker, Leslie Kevin; Mattus, Catherine H.

    2015-12-19

    The selection of an aluminum alloy for target irradiation affects post-irradiation target dissolution and separations. Recent tests with aluminum alloy 6061 yielded greater than expected precipitation in the dissolver, forming up to 10 wt.% solids of aluminum hydroxides and aluminosilicates. Aluminosilicate dissolution presents challenges in a number of different areas, metals extraction from minerals, flyash treatment, and separations from aluminum alloys. We present experimental work that attempts to maximize dissolution of aluminum metal, along with silicon, magnesium, and copper impurities, through control of temperature, the rate of reagent addition, and incubation time. Aluminum phase transformations have been identified as amore » function of time and temperature, using X-ray diffraction. Solutions have been analyzed using wet chemical methods and X-ray fluorescence. Our data have been compared with published calculations of aluminum phase diagrams. Approaches are given to enhance the dissolution of aluminum and aluminosilicate phases in caustic solution.« less

  11. Dissolution and Separation of Aluminum and Aluminosilicates

    SciTech Connect

    McFarlane, Joanna; Benker, Dennis; DePaoli, David W.; Felker, Leslie Kevin; Mattus, Catherine H.

    2015-12-19

    The selection of an aluminum alloy for target irradiation affects post-irradiation target dissolution and separations. Recent tests with aluminum alloy 6061 yielded greater than expected precipitation in the dissolver, forming up to 10 wt.% solids of aluminum hydroxides and aluminosilicates. Aluminosilicate dissolution presents challenges in a number of different areas, metals extraction from minerals, flyash treatment, and separations from aluminum alloys. We present experimental work that attempts to maximize dissolution of aluminum metal, along with silicon, magnesium, and copper impurities, through control of temperature, the rate of reagent addition, and incubation time. Aluminum phase transformations have been identified as a function of time and temperature, using X-ray diffraction. Solutions have been analyzed using wet chemical methods and X-ray fluorescence. Our data have been compared with published calculations of aluminum phase diagrams. Approaches are given to enhance the dissolution of aluminum and aluminosilicate phases in caustic solution.

  12. The Alkaline Dissolution Rate of Calcite.

    PubMed

    Colombani, Jean

    2016-07-01

    Due to the widespread presence of calcium carbonate on Earth, several geochemical systems, among which is the global CO2 cycle, are controlled to a large extent by the dissolution and precipitation of this mineral. For this reason, the dissolution of calcite has been thoroughly investigated for decades. Despite this intense activity, a consensual value of the dissolution rate of calcite has not been found yet. We show here that the inconsistency between the reported values stems mainly from the variability of the chemical and hydrodynamic conditions of measurement. The spreading of the values, when compared in identical conditions, is much less than expected and is interpreted in terms of sample surface topography. This analysis leads us to propose benchmark values of the alkaline dissolution rate of calcite compatible with all the published values, and a method to use them in various chemical and hydrodynamic contexts. PMID:27282839

  13. Nylon Dissolution in Nitric Acid Solutions

    SciTech Connect

    KESSINGER, GLENF.

    2004-06-16

    H Area Operations is planning to process Pu-contaminated uranium scrap in support of de-inventory efforts. Nylon bags will be used to hold materials to be dissolved in H-Canyon. Based on this set of twelve nylon dissolutions, it is concluded that (when other variables are held constant): increased acid concentration results in increased dissolution rates; increased acid concentration results in a lower dissolution onset temperature; little, if any, H plus is consumed during the depolymerization process; and 2.0-3.0 M HNO3, with 0.025 M KF and 2 g/L B, is satisfactory for the dissolution of nylon bag materials to be used during H-Canyon processing.

  14. Dissolution rates of prehnite, epidote, and albite

    SciTech Connect

    Rosemary, N.M. )

    1991-11-01

    Dissolution rates of prehnite and epidote in aqueous solutions were measured in the temperature range 25 to 90C, and as a function of pH. The dissolution rate of albite was measured at pH 1.4 at temperatures between 25 and 90C. Batch experiments using low ionic strength pH buffers in constant temperature water batch or ovens provided data on cumulative element release as a function of time. Steady state Si, Ca, Na, and Al release data obtained from these experiments were used to obtain limiting dissolution rates, where the term limiting rate denotes dissolution of a bulk mineral under conditions where it is far from equilibrium with the fluid. At 90C and at pH 1.4 to 6, prehnite and epidote dissolution rates decrease and are proportional to approximately {minus}0.3 pH for prehnite and {minus}0.2 pH for epidote. Above pH 6, prehnite dissolution becomes pH independent, by epidote dissolution increases with rates that are proportional to between +0.3 and +0.6 pH. Prehnite and epidote dissolution is linear and stoichiometric at low pH. At pH greater than 7, both minerals initially display preferential release of Si and Al relative to Ca; however, with increasing reaction dissolution becomes stoichiometric. This suggests that a Ca-enriched layer forms but reaches a steady state thickness which does not impede subsequent linear stoichiometric release. At pH 1.4, the limiting dissolution rate for albite is linear and stoichiometric. At pH 1.4, the activation energies are 18.12 {plus minus} 0.81 kcal mol{sup {minus}1} for prehnite, 19.76 {plus minus} 1.2 kcal mol{sup {minus}1} for epidote and 17.07 {plus minus} 1.6 kcal mol{sup {minus}1} for albite. At pH 6.5, the activation energy for prehnite dissolution is 20.73 {plus minus} 3.2 kcal mol{sup {minus}1}.

  15. Impact of iron chelators on short-term dissolution of basaltic glass

    NASA Astrophysics Data System (ADS)

    Perez, Anne; Rossano, Stéphanie; Trcera, Nicolas; Verney-Carron, Aurélie; Huguenot, David; van Hullebusch, Eric D.; Catillon, Gilles; Razafitianamaharavo, Angelina; Guyot, François

    2015-08-01

    Although microorganisms seem to play an important role in the alteration processes of basaltic glasses in solution, the elementary mechanisms involved remain unclear in particular with regard to the role of organic ligands excreted by the cells. Two glasses, one with Fe and one without Fe were synthesized to model basaltic glass compositions. Fe in the glass was mostly Fe(III) for enhancing interaction with siderophores, yet with small but significant amounts of Fe(II) (between 10% and 30% of iron). The prepared samples were submitted to abiotic alteration experiments in buffered (pH 6.4) diluted solutions of metal-specific ligands, namely oxalic acid (OA, 10 mM), desferrioxamine (DFA, 1 mM) or 2,2‧-bipyridyl (BPI, 1 mM). Element release from the glass into the solution after short term alteration (maximum 1 week) was measured by ICP-OES, and normalized mass losses and relative release ratios (with respect to Si) were evaluated for each element in each experimental condition. The presence of organic ligands had a significant effect on the dissolution of both glasses. Trivalent metals chelators (OA, DFA) impacted on the release of Fe3+ and Al3+, and thus on the global dissolution of both glasses, enhancing all release rates and dissolution stoichiometry (release rates were increased up to 7 times for Al or Fe). As expected, the mostly divalent metal chelator BPI interacted preferentially with Ca2+, Mg2+ and Fe2+. This study thus allows to highlight the central roles of iron and aluminium in interaction with some organic ligands in the alteration processes of basaltic glasses. It thus provides a step toward understanding the biological contribution of this fundamental geological process.

  16. Conceptual and instrumental progress in dissolution DNP

    NASA Astrophysics Data System (ADS)

    Jähnig, Fabian; Kwiatkowski, Grzegorz; Ernst, Matthias

    2016-03-01

    We discuss conceptual and instrumental progress in dissolution DNP since its introduction in 2003. In our view there are three critical steps in the dissolution DNP process: (i) The achievable polarization level in a sample. (ii) The time required to build up the polarization. (iii) The transfer of the sample to the measurement system with minimum loss of polarization. In this review we describe in detail these steps and the different methodological and instrumental implementations, which have been proposed to optimize them.

  17. A multiphase interfacial model for the dissolution of spent nuclear fuel

    NASA Astrophysics Data System (ADS)

    Jerden, James L.; Frey, Kurt; Ebert, William

    2015-07-01

    The Fuel Matrix Dissolution Model (FMDM) is an electrochemical reaction/diffusion model for the dissolution of spent uranium oxide fuel. The model was developed to provide radionuclide source terms for use in performance assessment calculations for various types of geologic repositories. It is based on mixed potential theory and consists of a two-phase fuel surface made up of UO2 and a noble metal bearing fission product phase in contact with groundwater. The corrosion potential at the surface of the dissolving fuel is calculated by balancing cathodic and anodic reactions occurring at the solution interfaces with UO2 and NMP surfaces. Dissolved oxygen and hydrogen peroxide generated by radiolysis of the groundwater are the major oxidizing agents that promote fuel dissolution. Several reactions occurring on noble metal alloy surfaces are electrically coupled to the UO2 and can catalyze or inhibit oxidative dissolution of the fuel. The most important of these is the oxidation of hydrogen, which counteracts the effects of oxidants (primarily H2O2 and O2). Inclusion of this reaction greatly decreases the oxidation of U(IV) and slows fuel dissolution significantly. In addition to radiolytic hydrogen, large quantities of hydrogen can be produced by the anoxic corrosion of steel structures within and near the fuel waste package. The model accurately predicts key experimental trends seen in literature data, the most important being the dramatic depression of the fuel dissolution rate by the presence of dissolved hydrogen at even relatively low concentrations (e.g., less than 1 mM). This hydrogen effect counteracts oxidation reactions and can limit fuel degradation to chemical dissolution, which results in radionuclide source term values that are four or five orders of magnitude lower than when oxidative dissolution processes are operative. This paper presents the scientific basis of the model, the approach for modeling used fuel in a disposal system, and preliminary

  18. Experimental determination of chlorite dissolution rates

    SciTech Connect

    Rochelle, C.A.; Bateman, K.; MacGregor, R.; Pearce, J.M.; Wetton, P.D.; Savage, D.

    1995-12-31

    Current concepts of the geological disposal of low- and intermediate-level radioactive wastes in the UK envisage the construction of a mined facility (incorporating cementitious engineered barriers) in chlorite-bearing rocks. To model accurately the fluid-rock reactions within the disturbed zone surrounding a repository requires functions that describe mineral dissolution kinetics under pH conditions that vary from near neutral to highly alkaline. Therefore, an experimental study to determine the dissolution rates of Fe-rich chlorite has been undertaken as part of the Nirex Safety Assessment Research Program. Four experiments have been carried out at 25 C and four at 70 C, both sets using a range of NaCl/NaOH solutions of differing pH (of nominal pH 9.0, 10.3, 11.6 and 13.0 [at 25 C]). Dissolution rates have been calculated and were found to increase with increasing pH and temperature. However, increased pH resulted in non-stoichiometric dissolution possibly due to preferential dissolution of part of the chlorite structure relative to another, or reprecipitation of some elements as thin hydroxide or oxyhydroxide surface coatings on the chlorite. These results also show that chlorite dissolution is appreciably slower than that of albite and quartz at both 25 and 70 C, but slightly faster than that of muscovite at 70 C.

  19. Kinetics of anorthite dissolution in basaltic melt

    NASA Astrophysics Data System (ADS)

    Yu, Yi; Zhang, Youxue; Chen, Yang; Xu, Zhengjiu

    2016-04-01

    We report convection-free anorthite dissolution experiments in a basaltic melt at 1280-1500 °C and 0.5 GPa on two different crystallographic surfaces, (1 2 1 bar) and (3 bar 0 2) to investigate dissolution kinetics. The anisotropy of the anorthite dissolution rate along these two surfaces is negligible. Time series experiments at ∼1280 °C show that anorthite dissolution is mainly controlled by diffusion in the melt within experimental uncertainty. Analytical solutions were used to model the dissolution and diffusion processes, and to obtain the diffusivities and the saturation concentrations of the equilibrium-determining component (Al2O3) for anorthite dissolution into the basaltic melt. For the first time, we are able to show the physical and chemical characteristics of quench growth effect on the near-interface melt using high spatial resolution (0.3 μm) EDS analyses. For anorthite (An# ⩾ 90) saturation in a melt with 39-53 wt% SiO2 and ⩽0.4 wt% H2O, the concentration of Al2O3 in wt% depends on temperature as follows:

  20. [In vitro dissolution rate of Liuwei Wuling tablet based on biological potency and integrated dissolution].

    PubMed

    Zheng, Juan; Cheng, Ling; Shen, Cheng-ying; Li, Juan-juan; Qiu, Ling; Shen, Gang; Han, Jin; Yuan, Hai-long

    2015-11-01

    To explore the feasibility of chemical and biological method in evaluation of the in vitro dissolution rate of Liuwei Wuling tablet (LWT), this experiment investigated the inhibitory effect of LWT dissolving solutions on LX-2 hepatic stellate cells in 0.1% SDS dissolution medium in different dissolving periods. From these results, the cumulative dissolution rate of LWT was obtained based on the cell inhibitory rate. The dissolution rates of deoxyschizandrin, phillyrin, and Specnuezhenide were determined by HPLC method. A novel approach of self-defined weighting coefficient had been created to establish the integrated dissolution rate model. Then f2 similar factor method was used to evaluate the relevance of these two methods. The results showed that f2 values for deoxyschizandrin, phillyrin, Specnuezhenide, and the integrated dissolution were 61, 43, 61 and 75 respectively, indicating that the dissolution of multi-component integration could fully reflect the biological potency of the whole recipe. The dissolution evaluation method for multicomponent integration based on biological activity is expected to be one of the effective means for in vitro dissolution test of LWT. PMID:27097413

  1. Water-Soluble Phosphine Capable of Dissolving Elemental Gold: The Missing Link between 1,3,5-Triaza-7-phosphaadamantane (PTA) and Verkade's Ephemeral Ligand.

    PubMed

    Britvin, Sergey N; Lotnyk, Andriy

    2015-04-29

    We herein describe a tricyclic phosphine with previously unreported tris(homoadamantane) cage architecture. That water-soluble, air- and thermally stable ligand, 1,4,7-triaza-9-phosphatricyclo[5.3.2.1(4,9)]tridecane (hereinafter referred to as CAP) exhibits unusual chemical behavior toward gold and gold compounds: it readily reduces Au(III) to Au(0), promotes oxidative dissolution of nanocrystalline gold(0) with the formation of water-soluble trigonal CAP-Au(I) complexes, and displaces cyanide from [Au(CN)2](-) affording triangular [Au(CAP)3](+) cation. From the stereochemical point of view, CAP can be regarded as an intermediate between 1,3,5-triaza-7-phosphaadamantane (PTA) and very unstable aminophosphine synthesized by Verkade's group: hexahydro-2a,4a,6a-triaza-6b-phosphacyclopenta[cd]pentalene. The chemical properties of CAP are likely related to its anomalous stereoelectronic profile: combination of strong electron-donating power (Tolman's electronic parameter 2056.8 cm(-1)) with the low steric demand (cone angle of 109°). CAP can be considered as macrocyclic counterpart of PTA with the electron-donating power approaching that of strongest known phosphine electron donors such as P(t-Bu)3 and PCy3. Therefore, CAP as sterically undemanding and electron-rich ligand populates the empty field on the stereoelectronic map of phosphine ligands: the niche between the classic tertiary phosphines and the sterically undemanding aminophosphines. PMID:25897572

  2. DISSOLUTION OF FISSILE MATERIALS CONTAINING TANTALUM METAL

    SciTech Connect

    Rudisill, T; Mark Crowder, M; Michael Bronikowski, M

    2007-05-29

    The dissolution of composite materials containing plutonium (Pu) and tantalum (Ta) metals is currently performed in Phase I of the HB-Line facility. The conditions for the present flowsheet are the dissolution of 500 g of Pu metal in the 15 L dissolver using a 4 M nitric acid (HNO{sub 3}) solution containing 0.2 M potassium fluoride (KF) at 95 C for 4-6 h.[1] The Ta metal, which is essentially insoluble in HNO{sub 3}/fluoride solutions, is rinsed with process water to remove residual acid, and then burned to destroy classified information. During the initial dissolution campaign, the total mass of Pu and Ta in the dissolver charge was limited to nominally 300 g. The reduced amount of Pu in the dissolver charge coupled with significant evaporation of solution during processing of several dissolver charges resulted in the precipitation of a fluoride salt contain Pu. Dissolution of the salt required the addition of aluminum nitrate (Al(NO{sub 3}){sub 3}) and a subsequent undesired 4 h heating cycle. As a result of this issue, HB-Line Engineering requested the Savannah River National Laboratory (SRNL) to optimize the dissolution flowsheet to reduce the cycle time, reduce the risk of precipitating solids, and obtain hydrogen (H{sub 2}) generation data at lower fluoride concentrations.[2] Using samples of the Pu/Ta composite material, we performed three experiments to demonstrate the dissolution of the Pu metal using HNO{sub 3} solutions containing 0.15 and 0.175 M KF. When 0.15 M KF was used in the dissolving solution, 95.5% of the Pu in the sample dissolved in approximately 6 h. The undissolved material included a small amount of Pu metal and plutonium oxide (PuO{sub 2}) solids. Complete dissolution of the metal would have likely occurred if the dissolution time had been extended. This assumption is based on the steady increase in the Pu concentration observed during the last several hours of the experiment. We attribute the formation of PuO{sub 2} to the complexation

  3. Ligand modeling and design

    SciTech Connect

    Hay, B.P.

    1997-10-01

    The purpose of this work is to develop and implement a molecular design basis for selecting organic ligands that would be used in the cost-effective removal of specific radionuclides from nuclear waste streams. Organic ligands with metal ion specificity are critical components in the development of solvent extraction and ion exchange processes that are highly selective for targeted radionuclides. The traditional approach to the development of such ligands involves lengthy programs of organic synthesis and testing, which in the absence of reliable methods for screening compounds before synthesis, results in wasted research effort. The author`s approach breaks down and simplifies this costly process with the aid of computer-based molecular modeling techniques. Commercial software for organic molecular modeling is being configured to examine the interactions between organic ligands and metal ions, yielding an inexpensive, commercially or readily available computational tool that can be used to predict the structures and energies of ligand-metal complexes. Users will be able to correlate the large body of existing experimental data on structure, solution binding affinity, and metal ion selectivity to develop structural design criteria. These criteria will provide a basis for selecting ligands that can be implemented in separations technologies through collaboration with other DOE national laboratories and private industry. The initial focus will be to select ether-based ligands that can be applied to the recovery and concentration of the alkali and alkaline earth metal ions including cesium, strontium, and radium.

  4. Can the dissolution rates of individual minerals be used to describe whole rock dissolution?

    NASA Astrophysics Data System (ADS)

    Critelli, Teresa; Marini, Luigi; Schott, Jacques; Mavromatis, Vasileios; Apollaro, Carmine; Rinder, Thomas; De Rosa, Rosanna; Oelkers, Eric H.

    2014-05-01

    There have been an exhaustive number of laboratory studies determining the dissolution rates of individual minerals, but few have focused on the dissolution rates of minerals in multi-mineralic rocks. As a result, geochemical modeling of the temporal evolution of water-rock interaction is generally based on the assumption that the dissolution rate of minerals within a rock is equal to that measured in the laboratory on individual minerals. To verify this hypothesis, we have determined experimentally the dissolution rates of a well characterized metabasalt rock (Apollaro et al., 2011; Bloise et al., 2012) from the Mt. Reventino area (Southern Italy) at 25°C in mixed flow reactors. From these experiments and rock modal analysis we have deduced the dissolution rates of the minerals present in the rock (actinolite, albite, chlorite, epidote, and phengite). The major observation of this effort include: (i) only small differences in the dissolution rates of the individual minerals were observed; these rates are close to the whole-rock dissolution rate and (ii) the dissolution rates of albite and chlorite are in close agreement with laboratory rates obtained from individual mineral dissolution experiments, whereas those of actinolite, phengite, and epidote are not consistent with those reported in literature by 1-2 orders of magnitude. These results demonstrate that the dissolution rate of a given mineral in a multi-phase rock can be affected by the presence of the other minerals. Rock dissolution kinetics are likely constrained by the dissolution rates of the more abundant, lesser reactive mineral or minerals in the rock. These unreactive minerals can prevent the dissolution of the more rapidly dissolving mineral grains by keeping them out of contact with the aqueous phase. This implies that the overall weathering rate of rocks cannot be modelled from the measured dissolution rates of its individual minerals. If confirmed through further studies, this conclusion may

  5. Towards a less biased dissolution of chitosan.

    PubMed

    Thevarajah, Joel J; Bulanadi, Jerikho C; Wagner, Manfred; Gaborieau, Marianne; Castignolles, Patrice

    2016-09-01

    The dissolution of polysaccharides is notoriously challenging, especially when one needs a "true" solution. Factors influencing chitosan's solubility include composition, also known as degree of acetylation (DA). The dissolution of chitosan was investigated by visual observation, size-exclusion chromatography (SEC), pressure mobilization (PM), free-solution capillary electrophoresis (CE) and real-time solution-state NMR spectroscopy. Aqueous HCl dissolves around 15% more chitosan than the commonly used aqueous acetic acid (AcOH), however aggregates were detected in SEC suggesting incomplete dissolution. Significant deacetylation of chitosan over the period needed for dissolution at high temperature was observed by NMR spectroscopy in DCl by about 20% of the initial DA value. Accurate DA determination by NMR spectroscopy may thus be possible only in the solid state (with a precision within 1% on the DA % scale above a DA of 10%). Overall a compromise between maximum solubilization and minimum degradation is required in attempting to obtain a "true" solution of chitosan. The completeness of the dissolution may be more influenced by the average DA than by molar mass. PMID:27543035

  6. Reductive dissolution of goethite by phenolic reductants

    NASA Astrophysics Data System (ADS)

    LaKind, Judy S.; Stone, Alan T.

    1989-05-01

    The reductive dissolution of goethite (α-FeOOH) and hematite (α-Fe 2O 3) by phenolic reductants has been examined in order to improve the understanding of iron transformations in soils, sediments and aquifers. Rates of goethite reductive dissolution by hydroquinone increased as the pH was increased from pH 1.8 to 4.65, arid the following reaction stoichiometry was obeyed: 2 α- FeOOH + QH2 = 2 Fe2+ + Q + 4 OH-. As the pH was increased from pH 4.5 to 6.0, the reductive dissolution rate decreased to below the detection limit. At pH 3.4, the reductive dissolution of hematite was two orders of magnitude slower than goethite. The relationship between structure and reactivity was examined for a series of mono-, di-, and tri-hydroxybenzene reductants. Rates of reductive dissolution decreased in the following order: catechol ˜- hydroquinone > 3,4-dihydroxybenzoic acid > resorcinol-phenol-4-hydroxybenzoic acid.

  7. Visualizing nanoparticle dissolution by imaging mass spectrometry.

    PubMed

    Szakal, Christopher; Ugelow, Melissa S; Gorham, Justin M; Konicek, Andrew R; Holbrook, R David

    2014-04-01

    We demonstrate the ability to visualize nanoparticle dissolution while simultaneously providing chemical signatures that differentiate between citrate-capped silver nanoparticles (AgNPs), AgNPs forced into dissolution via exposure to UV radiation, silver nitrate (AgNO3), and AgNO3/citrate deposited from aqueous solutions and suspensions. We utilize recently developed inkjet printing (IJP) protocols to deposit the different solutions/suspensions as NP aggregates and soluble species, which separate onto surfaces in situ, and collect mass spectral imaging data via time-of-flight secondary ion mass spectrometry (TOF-SIMS). Resulting 2D Ag(+) chemical images provide the ability to distinguish between the different Ag-containing starting materials and, when coupled with mass spectral peak ratios, provide information-rich data sets for quick and reproducible visualization of NP-based aqueous constituents. When compared to other measurements aimed at studying NP dissolution, the IJP-TOF-SIMS approach offers valuable information that can potentially help in understanding the complex equilibria in NP-containing solutions and suspensions, including NP dissolution kinetics and extent of overall dissolution. PMID:24611464

  8. Forsterite dissolution rates in Mg-sulfate-rich Mars-analog brines and implications of the aqueous history of Mars

    NASA Astrophysics Data System (ADS)

    Albright Olsen, Amanda; Hausrath, Elisabeth M.; Rimstidt, J. Donald

    2015-03-01

    High salinity brines, although rare on Earth's surface, may have been important in the geologic history of Mars. Increasing evidence suggests the importance of liquid brines in multiple locations on Mars. In order to interpret the effect of high ionic strength brines on olivine dissolution, which is widely present on Mars, 47 new batch reactor experiments combined with 35 results from a previous study conducted at 25°C from 1 < pH < 4 in magnesium sulfate, sodium sulfate, magnesium nitrate, and potassium nitrate solutions with ionic strengths as high as 12 m show that very high ionic strength brines have an inhibitory effect of forsterite dissolution rates. Multiple linear regression analysis of the data suggests that the inhibition in dissolution rates is due to decreased water activity at high ionic strengths. Regression models also show that mMg up to 4 m and mSO4 up to 3 m have no effect on forsterite dissolution rates. The effect of decreasing dissolution rates with decreasing aH2O is consistent with the idea that water acts as a ligand that participates in the dissolution process. Less available water to participate in the dissolution reaction results in a slower dissolution rate. Multiple linear regression analysis of the data produces the rate equation log r = -6.81 - 0.52pH + 3.26log aH2O. Forsterite in dilute solutions with a water activity of one dissolves twice as fast as those in brines with a water activity of 0.8.

  9. Ligand modeling and design

    SciTech Connect

    Hay, B.

    1996-10-01

    The purpose of this work is to develop and implement a molecular design basis for selecting organic ligands that would be used tin applications for the cost-effective removal of specific radionuclides from nuclear waste streams.

  10. Criticality safety in high explosives dissolution

    SciTech Connect

    Troyer, S.D.

    1997-06-01

    In 1992, an incident occurred at the Pantex Plant in which the cladding around a fissile material component (pit) cracked during dismantlement of the high explosives portion of a nuclear weapon. Although the event did not result in any significant contamination or personnel exposures, concerns about the incident led to the conclusion that the current dismantlement process was unacceptable. Options considered for redesign, dissolution tooling design considerations, dissolution tooling design features, and the analysis of the new dissolution tooling are summarized. The final tooling design developed incorporated a number of safety features and provides a simple, self-contained, low-maintenance method of high explosives removal for nuclear explosive dismantlement. Analyses demonstrate that the tooling design will remain subcritical under normal, abnormal, and credible accident scenarios. 1 fig.

  11. Buoyant currents arrested by convective dissolution

    NASA Astrophysics Data System (ADS)

    MacMinn, Christopher W.; Juanes, Ruben

    2013-05-01

    When carbon dioxide (CO2) dissolves into water, the density of water increases. This seemingly insubstantial phenomenon has profound implications for geologic carbon sequestration. Here we show, by means of laboratory experiments with analog fluids, that the up-slope migration of a buoyant current of CO2 is arrested by the convective dissolution that ensues from a fingering instability at the moving CO2-groundwater interface. We consider the effectiveness of convective dissolution as a large-scale trapping mechanism in sloping aquifers, and we show that a small amount of slope is beneficial compared to the horizontal case. We study the development and coarsening of the fingering instability along the migrating current and predict the maximum migration distance of the current with a simple sharp-interface model. We show that convective dissolution exerts a powerful control on CO2 plume dynamics and, as a result, on the potential of geologic carbon sequestration.

  12. Formation and dissolution of bacterial colonies.

    PubMed

    Weber, Christoph A; Lin, Yen Ting; Biais, Nicolas; Zaburdaev, Vasily

    2015-09-01

    Many organisms form colonies for a transient period of time to withstand environmental pressure. Bacterial biofilms are a prototypical example of such behavior. Despite significant interest across disciplines, physical mechanisms governing the formation and dissolution of bacterial colonies are still poorly understood. Starting from a kinetic description of motile and interacting cells we derive a hydrodynamic equation for their density on a surface, where most of the kinetic coefficients are estimated from experimental data for N. gonorrhoeae bacteria. We use it to describe the formation of multiple colonies with sizes consistent with experimental observations. Finally, we show how the changes in the cell-to-cell interactions lead to the dissolution of the bacterial colonies. The successful application of kinetic theory to a complex far from equilibrium system such as formation and dissolution of living bacterial colonies potentially paves the way for the physical quantification of the initial stages of biofilm formation. PMID:26465495

  13. Formation and dissolution of bacterial colonies

    NASA Astrophysics Data System (ADS)

    Weber, Christoph A.; Lin, Yen Ting; Biais, Nicolas; Zaburdaev, Vasily

    2015-09-01

    Many organisms form colonies for a transient period of time to withstand environmental pressure. Bacterial biofilms are a prototypical example of such behavior. Despite significant interest across disciplines, physical mechanisms governing the formation and dissolution of bacterial colonies are still poorly understood. Starting from a kinetic description of motile and interacting cells we derive a hydrodynamic equation for their density on a surface, where most of the kinetic coefficients are estimated from experimental data for N. gonorrhoeae bacteria. We use it to describe the formation of multiple colonies with sizes consistent with experimental observations. Finally, we show how the changes in the cell-to-cell interactions lead to the dissolution of the bacterial colonies. The successful application of kinetic theory to a complex far from equilibrium system such as formation and dissolution of living bacterial colonies potentially paves the way for the physical quantification of the initial stages of biofilm formation.

  14. Design and evaluation of Lumefantrine – Oleic acid self nanoemulsifying ionic complex for enhanced dissolution

    PubMed Central

    2013-01-01

    Background Lumefantrine, an antimalarial molecule has very low and variable bioavailability owing to its extremely poor solubility in water. It is recommended to be taken with milk to enhance its solubility and bioavailability. The aim of present study was to develop a Self Nanoemulsifying Delivery system (SNEDs) of lumefantrine (LF) to achieve rapid and complete dissolution independent of food-fat and surfactant in dissolution media. Methods Solubility of LF in oil, co-solvent/co-surfactant and surfactant solution and emulsification efficiency of surfactant were analyzed to optimize the LF loaded self nanoemulsifying preconcentrate. Effect of LF-oleic acid complexation on emulsification, droplet size, zeta potential and dissolution were investigated. Effect of milk concentration and fat content on saturation solubility and dissolution of LF was investigated. Dissolution of marketed formulation and LF-SNEDs was carried out in pH 1.2 and pH 6.8 phosphate buffer. Results LF exhibited very high solubility in oleic acid owing to complexation between tertiary amine of LF and carboxyl group of oleic acid (OA). Cremophore EL and medium chain monoglyceride were selected surfactant and co-surfactant, respectively. Significantly smaller droplet size (37 nm), shift in zeta potential from negative to positive value, very high drug loading in lipid based system (> 10%), no precipitation after dissolution are the major distinguish characteristics contributed by LF-OA complex in the SNED system. Saturation solubility and dissolution study in milk containing media pointed the significant increment in solubility of LF in the presence of milk-food fat. LF-SNEDs showed > 90% LF release within 30 min in pH 1.2 while marketed tablet showed almost 0% drug release. Conclusion Self nanoemulsification promoting ionic complexation between basic drug and oleic acid hold great promise in enhancing solubility of hydrophobic drugs. PMID:23531442

  15. Comparative Dissolution Kinetics of Biogenic and Chemogenic Uraninite Under Oxidizing Conditions in the Presence of Carbonate

    SciTech Connect

    Ulrich, Kai-Uwe; Ilton, Eugene S.; Veeramani, Harish; Sharp, Jonathan O.; Bernier-Latmani, Rizlan; Schofield, Eleanor J.; Bargar, John; Giammar, Daniel E.

    2009-10-15

    The long-term stability of biogenic uraninite with respect to oxidation is pivotal to the success of in situ bioreduction strategies for the subsurface remediation of uranium legacies. Given the structural homology between biogenic uraninite nanoparticles obtained from Shewanella oneidensis MR-1 and chemogenic UO2.00, similar surface free energy and reactivity is expected. Batch and flow-through dissolution experiments were conducted along with spectroscopic analyses to compare both materials with respect to their equilibrium solubility, dissolution mechanisms, and dissolution kinetics in water of varied oxygen and carbonate concentrations. Both uraninite materials exhibited a similar intrinsic solubility of ~10-8 M under reducing conditions. The observation of comparable dissolution rates under anoxic as well as oxidizing conditions is consistent with the structural bulk homology of biogenic and stoichiometric uraninite. Carbonate, a ubiquitous groundwater component and strong complexant of U(VI), reversibly promoted the uraninite dissolution not only under moderately oxidizing, but also under reducing conditions, where the biogenic material yielded higher dissolution rates than the chemogenic. This difference is in accordance with the higher proportion of U(V) detected on the biogenic uraninite surface by means of x-ray photoelectron spectroscopy. Reasonable sources of the intermediate U(V) are discussed. The observed increase of the dissolution rates can be explained by carbonate complexation of U(V) facilitating the detachment of U(V) from the uraninite surface. The fraction of surface U(VI) increased with increasing oxygen concentration; this result is consistent with x-ray absorption near-edge spectra showing evidence of higher-valent U in the form of UO2+x (0 < x ≤ 0.20). In equilibrium with air, combined spectroscopic results support the formation of a near-surface layer of U4O9 (UO2.25) coated by an outer layer of U(VI) corresponding to a metaschoepite

  16. DISSOLUTION OF IRRADIATED MURR FUEL ASSEMBLIES

    SciTech Connect

    Kyser, E.

    2010-06-17

    A literature survey on the dissolution of spent nuclear fuel from the University of Missouri Research Reactor (MURR) has been performed. This survey encompassed both internal and external literature sources for the dissolution of aluminum-clad uranium alloy fuels. The most limiting aspect of dissolution in the current facility configuration involves issues related to the control of the flammability of the off-gas from this process. The primary conclusion of this work is that based on past dissolution of this fuel in H-Canyon, four bundles of this fuel (initial charge) may be safely dissolved in a nitric acid flowsheet catalyzed with 0.002 M mercuric nitrate using a 40 scfm purge to control off-gas flammability. The initial charge may be followed by a second charge of up to five bundles to the same dissolver batch depending on volume and concentration constraints. The safety of this flowsheet relies on composite lower flammability limits (LFL) estimated from prior literature, pilot-scale work on the dissolution of site fuels, and the proposed processing flowsheet. Equipment modifications or improved LFL data offer the potential for improved processing rates. The fuel charging sequence, as well as the acid and catalyst concentrations, will control the dissolution rate during the initial portion of the cycle. These parameters directly impact the hydrogen and off-gas generation and, along with the purge flowrate determine the number of bundles that may be charged. The calculation approach within provides Engineering a means to determine optimal charging patterns. Downstream processing of this material should be similar to that of recent processing of site fuels requiring only minor adjustments of the existing flowsheet parameters.

  17. Microbial dissolution of silicate materials. Final report

    SciTech Connect

    Schwartzman, D.

    1996-03-26

    The objective of this research was to better understand the role of selected thermophilic bacteria in the colonization and dissolution of silicate minerals, with potential applications to the HDR Project. The demonstration of enhanced dissolution from microbial effects is critically dependent on providing a mineral bait within a media deficient in the critical nutrient found in the mineral (e.g., Fe). Reproducible experimental conditions in batch experiments require agitation to expose mineral powders, as well as nearly similar initial conditions for both inoculated cultures and controls. It is difficult, but not impossible to ensure reproducible conditions with microbes favoring filamentous growth habits.

  18. Effects of magnetic fields on dissolution of arthritis causing crystals

    NASA Astrophysics Data System (ADS)

    Takeuchi, Y.; Iwasaka, M.

    2015-05-01

    The number of gout patients has rapidly increased because of excess alcohol and salt intake. The agent responsible for gout is the monosodium urate (MSU) crystal. MSU crystals are found in blood and consist of uric acid and sodium. As a substitute for drug dosing or excessive water intake, physical stimulation by magnetic fields represents a new medical treatment for gout. In this study, we investigated the effects of a magnetic field on the dissolution of a MSU crystal suspension. The white MSU crystal suspension was dissolved in an alkaline solution. We measured the light transmission of the MSU crystal suspension by a transmitted light measuring system. The magnetic field was generated by a horizontal electromagnet (maximum field strength was 500 mT). The MSU crystal suspension that dissolved during the application of a magnetic field of 500 mT clearly had a higher dissolution rate when compared with the control sample. We postulate that the alkali solution promoted penetration upon diamagnetic rotation and this magnetic field orienting is because of the pronounced diamagnetic susceptibility anisotropy of the MSU crystal. The results indicate that magnetic fields represent an effective gout treatment approach.

  19. Melanoma cell galectin-1 ligands functionally correlate with malignant potential*

    PubMed Central

    Yazawa, Erika M.; Geddes-Sweeney, Jenna E.; Cedeno-Laurent, Filiberto; Walley, Kempland C.; Barthel, Steven R.; Opperman, Matthew J.; Liang, Jennifer; Lin, Jennifer Y.; Schatton, Tobias; Laga, Alvaro C.; Mihm, Martin C.; Qureshi, Abrar A.; Widlund, Hans R.; Murphy, George F.; Dimitroff, Charles J.

    2015-01-01

    Galectin-1 (Gal-1)-binding to Gal-1 ligands on immune and endothelial cells can influence melanoma development through dampening anti-tumor immune responses and promoting angiogenesis. However, whether Gal-1 ligands are functionally expressed on melanoma cells to help control intrinsic malignant features remains poorly understood. Here, we analyzed expression, identity and function of Gal-1 ligands in melanoma progression. Immunofluorescent analysis of benign and malignant human melanocytic neoplasms revealed that Gal-1 ligands were abundant in severely-dysplastic nevi as well as in primary and metastatic melanomas. Biochemical assessments indicated that melanoma cell adhesion molecule (MCAM) was a major Gal-1 ligand on melanoma cells that was largely dependent on its N-glycans. Other melanoma cell Gal-1 ligand activity conferred by O-glycans was negatively regulated by α2,6 sialyltransferase ST6GalNAc2. In Gal-1-deficient mice, MCAM-silenced (MCAMKD) or ST6GalNAc2-overexpressing (ST6O/E) melanoma cells exhibited slower growth rates, underscoring a key role for melanoma cell Gal-1 ligands and host Gal-1 in melanoma growth. Further analysis of MCAMKD or ST6O/E melanoma cells in cell migration assays indicated that Gal-1 ligand-dependent melanoma cell migration was severely inhibited. These findings provide a refined perspective on Gal-1 – melanoma cell Gal-1 ligand interactions as contributors to melanoma malignancy. PMID:25756799

  20. Natural remobilization of multicomponent DNAPL pools due to dissolution.

    PubMed

    Roy, J W; Smith, J E; Gillham, R W

    2002-12-01

    Mixtures of dense nonaqueous phase liquids (DNAPLs) trapped in the subsurface can act as long-term sources of contamination by dissolving into flowing groundwater. If the components have different solubilities then dissolution will alter the composition of the remaining DNAPL. We theorized that a multicomponent DNAPL pool may become mobile due to the natural dissolution process. In this study, we focused on two scenarios: (1) a DNAPL losing light component(s), with the potential for downward migration; and (2) a DNAPL losing dense component(s), with the potential for upward migration following transformation into a less dense than water nonaqueous phase liquid (LNAPL). We considered three binary mixtures of common groundwater contaminants: benzene and tetrachloroethylene (PCE), PCE and dichloromethane (DCM), and DCM and toluene. A number of physical properties that control the retention and transport of DNAPL in porous media were measured for the mixtures, namely: density, interfacial tension, effective solubility, and viscosity. All properties except density exhibited nonlinear relationships with changing molar ratio of the DNAPL. To illustrate the potential for natural remobilization, we modelled the following two primary mechanisms: the reduction in pool height as mass is lost by dissolution, and the changes in fluid properties with changing molar ratio of the DNAPL. The first mechanism always reduces the capillary pressure in the pool, while the second mechanism may increase the capillary pressure or alter the direction of the driving force. The difference between the rate of change of each determines whether the potential for remobilization increases or decreases. Static conditions and horizontal layering were assumed along with a one-dimensional, compositional modelling approach. Our results indicated that for initial benzene/PCE ratios greater than 25:75, the change in density was sufficiently faster than the decline in pool height to promote DNAPL

  1. Sodium tetraphenylborate solubility and dissolution rates

    SciTech Connect

    Barnes, M.J.; Peterson, R.A.; Swingle, R.F.; Reeves, C.T.

    1995-12-31

    The rate of solid sodium tetraphenylborate (NaTPB) dissolution in In-Tank Precipitation salt solutions has been experimentally determined. The data indicates that the dissolution rate of solid NaTPB is a minor contributor the lag time experienced in the 1983 Salt Decontamination Demonstration Test and should not be considered as the rate determining step. Current analytical models for predicting the time to reach the composite lower flammability limit assume that the lag time is not more than 6 hours, and the data supports this assumption (i.e., dissolution by itself requires much less than 6 hours). The data suggests that another step--such as mass transport, the reaction of a benzene precursor or the mixing behavior--is the rate determining factor for benzene release to the vapor space in Tank 48H. In addition, preliminary results from this program show that the degree of agitation employed is not a significant parameter in determining the rate of NaTPB dissolution. As a result of this study, an improved equation for predicting equilibrium tetraphenylborate solubility with respect to temperature and sodium ion concentration has been determined.

  2. Dissolution enhancement of chlorzoxazone using cogrinding technique

    PubMed Central

    Raval, Mihir K.; Patel, Jaydeep M.; Parikh, Rajesh K.; Sheth, Navin R.

    2015-01-01

    Purpose: The aim of the present work was to improve rate of dissolution and processing parameters of BCS class II drug, chlorzoxazone using cogrinding technique in the presence of different excipients as a carrier. Materials and Methods: The drug was coground with various carriers like polyethylene glycol (PEG 4000), hydroxypropyl methylcellulose (HPMC) E50LV, polyvinylpyrrolidone (PVP)K30, Kaolin and Neusilin US2 using ball mill, where only PEG 4000 improved dissolution rate of drug by bringing amorphization in 1:3 ratio. The coground mixture after 3 and 6 h was evaluated for various analytical, physicochemical and mechanical parameters. Results: The analysis showed conversion of Chlorzoxazone from its crystalline to amorphization form upon grinding with PEG 4000. Coground mixture as well as its directly compressed tablet showed 2.5-fold increment in the dissolution rate compared with pure drug. Directly compressible tablets prepared from pure drug required a large quantity of microcrystalline cellulose (MCC) during compression. The coground mixture and formulation was found stable in nature even after storage (40°C/75% relative humidity). Conclusions: Cogrinding can be successfully utilized to improve the rate of dissolution of poorly water soluble drugs and hence bioavailability. PMID:26682195

  3. 12 CFR 546.4 - Voluntary dissolution.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... savings association's board of directors may propose a plan for dissolution of the association. The plan... approved by the association's board of directors and by the OTS, it shall be submitted to the association's... charter either for cash sufficient to pay all obligations of the association and retire all...

  4. 25 CFR 11.605 - Dissolution.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... dissolution of marriage if: (1) The court finds that the marriage is irretrievably broken, if the finding is... affecting the attitude of one or both of the parties towards the marriage; (2) The court finds that either... of marriage, the Court of Indian Offenses shall grant the decree in that form unless the other...

  5. Dissolution of human teeth-derived hydroxyapatite.

    PubMed

    Seo, Dong Seok; Lee, Jong Kook

    2008-01-01

    We have been interested in human teeth which consist of hydroxyapatite (HA), but do not degrade for a long time. In order to overcome dissolution and mechanical degradation of man-made HA, biologically derived hydroxyapatite (BHA) ceramics were prepared from human teeth and their dissolving behavior was investigated in distilled water for 3-14 days and compared with an artificial HA made of synthetic HA powder. BHA ceramics were prepared by calcining freshly extracted human teeth at 900 degrees C and followed by sintering at 1200 degrees C for 2 h. All detectable peaks in the artificial HA are identical to HA lattice planes, whereas BHA consisted of a mixture of HA and beta-tricalcium phosphate (TCP). Although the artificial HA was expected to be stable in water, the surface dissolution initiated at grain boundaries followed by generated many separated grains and their associated pores. On the other hand, BHA showed that definite grains considered as beta-TCP were predominantly dissolved and the grains were separated from the matrix leaving pores. In the mean time, the rest region, mainly consisting of HA, did not show any evidence of dissolution. It indicates that BHA showed rather stable grain boundaries and lack of excessive dissolution in liquid environment. PMID:17943445

  6. Slow dissolution behaviour of amorphous capecitabine.

    PubMed

    Meulenaar, Jelte; Beijnen, Jos H; Schellens, Jan H M; Nuijen, Bastiaan

    2013-01-30

    In this article, we report the anomalous dissolution behaviour of amorphous capecitabine. In contrast to what is expected from thermodynamic theory, amorphous capecitabine dissolves significantly slower compared to its crystalline counterpart. Our experiments show that this is due to the "gelling" properties of amorphous capecitabine in an aqueous environment. The "gel", which is immediately formed upon contact with water, entraps the capecitabine and significantly slows down its dissolution. This "gelling" property is hypothesized to be related to the low glass transition temperature (Tg 19°C) of amorphous capecitabine, resulting in an instant collapse ("gelling") in an aqueous environment. From IR and DSC analysis it is shown that this collapsed capecitabine is remarkably stable and does not recrystallize upon an increased water content or temperature. This highly reproducible dissolution behaviour can be applied in the development of a sustained release dosage form as substantially less sustained release excipient is required in order to attain the desired release profile. As capecitabine is a high-dosed drug, this is highly favourable in view of the size and thus clinical feasibility of the final dosage form. Currently, we are developing and clinically testing a sustained release formulation making use of amorphous capecitabine and its remarkable dissolution behaviour. PMID:23219704

  7. Rate equations for sodium catalyzed quartz dissolution

    NASA Astrophysics Data System (ADS)

    Rimstidt, J. Donald

    2015-10-01

    Quartz dissolution rate data were fit to an equation that predicts the dissolution flux (J, mol/m2 sec) as a function of temperature (T, K), sodium concentration (mNa+, molal), and hydrogen ion activity (aH+). The same data fit equally well to an equation that expresses the rate as a function of temperature, sodium concentration, and hydroxide ion activity (aOH-) . These equations are more convenient to use than those given by Bickmore et al. (2008) because rates can be predicted without the implementation of a surface speciation model. They predict that at 25 °C quartz dissolves more than 200 times faster in seawater than in pure water. These two equations fit the data just as well as five other equations from Bickmore et al. (2008) that are based on surface species concentrations. All of these rate equations contain information about the reaction mechanism(s) for quartz dissolution but that information is ambiguous because the independent variables used to develop the equations are correlated. This means that rate equations alone cannot be used to infer the dissolution mechanism. Existing surface complexation, surface charge, terrace-ledge-kink, and Lewis acid-base models must be modified and amalgamated in order to develop a reliable model of the reaction mechanism(s).

  8. Dissolution Treatment of Depleted Uranium Waste

    SciTech Connect

    Gates-Anderson, D D; Laue, C A; Fitch, T E

    2004-02-09

    Researchers at LLNL have developed a 3-stage process that converts pyrophoric depleted uranium metal turnings to a solidified final product that can be transported to and buried at a permitted land disposal site. The three process stages are: (1) pretreatment; (2) dissolution; and (3) solidification. Each stage was developed following extensive experimentation. This report presents the results of their experimental studies.

  9. Oral and contact dissolution of gallstones.

    PubMed

    Schoenfield, L J; Marks, J W

    1993-04-01

    The appropriate selection of patients for treatment with oral ursodeoxycholic acid (UDCA)--a drug that has virtually no side effects--results in about 50% of patients experiencing safe dissolution of gallstones within 2 years. Eligible patients have small (less than 20 mm in diameter) radiolucent gallstones in a gallbladder visualized by oral cholecystography (OCG); ideal candidates are thin women who have gallstones that are less than 15 mm in diameter, floating when observed by OCG, or of low density on computed tomographic (CT) scanning. Contact dissolution with methyl tert-butyl ether (MTBE) is rapid, effective more often than UDCA, and safe but requires the expertise of an interventional radiologist. Any size and number of cholesterol gallstones that are not CT-dense will be dissolved by MTBE, leaving at most only insoluble debris that is clinically innocuous. Although gallstones recur after dissolution by UDCA or MTBE in 50% of patients within 5 years, recurrent gallstones are usually asymptomatic and/or can probably be dissolved. We conclude that oral or contact dissolution provides an alternative treatment to cholecystectomy for about 30% of patients with symptomatic gallstones. PMID:8480875

  10. On the dissolution of iridium by aluminum.

    SciTech Connect

    Hewson, John C.

    2009-08-01

    The potential for liquid aluminum to dissolve an iridium solid is examined. Substantial uncertainties exist in material properties, and the available data for the iridium solubility and iridium diffusivity are discussed. The dissolution rate is expressed in terms of the regression velocity of the solid iridium when exposed to the solvent (aluminum). The temperature has the strongest influence in the dissolution rate. This dependence comes primarily from the solubility of iridium in aluminum and secondarily from the temperature dependence of the diffusion coefficient. This dissolution mass flux is geometry dependent and results are provided for simplified geometries at constant temperatures. For situations where there is negligible convective flow, simple time-dependent diffusion solutions are provided. Correlations for mass transfer are also given for natural convection and forced convection. These estimates suggest that dissolution of iridium can be significant for temperatures well below the melting temperature of iridium, but the uncertainties in actual rates are large because of uncertainties in the physical parameters and in the details of the relevant geometries.

  11. Efavirenz Dissolution Enhancement I: Co-Micronization

    PubMed Central

    da Costa, Maíra Assis; Seiceira, Rafael Cardoso; Rodrigues, Carlos Rangel; Hoffmeister, Cristiane Rodrigues Drago; Cabral, Lucio Mendes; Rocha, Helvécio Vinícius Antunes

    2012-01-01

    AIDS constitutes one of the most serious infectious diseases, representing a major public health priority. Efavirenz (EFV), one of the most widely used drugs for this pathology, belongs to the Class II of the Biopharmaceutics Classification System for drugs with very poor water solubility. To improve EFV’s dissolution profile, changes can be made to the physical properties of the drug that do not lead to any accompanying molecular modifications. Therefore, the study objective was to develop and characterize systems with efavirenz able to improve its dissolution, which were co-processed with sodium lauryl sulfate (SLS) and polyvinylpyrrolidone (PVP). The technique used was co-micronization. Three different drug:excipient ratios were tested for each of the two carriers. The drug dispersion dissolution results showed significant improvement for all the co-processed samples in comparison to non-processed material and corresponding physical mixtures. The dissolution profiles obtained for dispersion with co-micronized SLS samples proved superior to those of co-micronized PVP, with the proportion (1:0.25) proving the optimal mixture. The improvements may be explained by the hypothesis that formation of a hydrophilic layer on the surface of the micronized drug increases the wettability of the system formed, corroborated by characterization results indicating no loss of crystallinity and an absence of interaction at the molecular level. PMID:24300394

  12. Dilution physics modeling: Dissolution/precipitation chemistry

    SciTech Connect

    Onishi, Y.; Reid, H.C.; Trent, D.S.

    1995-09-01

    This report documents progress made to date on integrating dilution/precipitation chemistry and new physical models into the TEMPEST thermal-hydraulics computer code. Implementation of dissolution/precipitation chemistry models is necessary for predicting nonhomogeneous, time-dependent, physical/chemical behavior of tank wastes with and without a variety of possible engineered remediation and mitigation activities. Such behavior includes chemical reactions, gas retention, solids resuspension, solids dissolution and generation, solids settling/rising, and convective motion of physical and chemical species. Thus this model development is important from the standpoint of predicting the consequences of various engineered activities, such as mitigation by dilution, retrieval, or pretreatment, that can affect safe operations. The integration of a dissolution/precipitation chemistry module allows the various phase species concentrations to enter into the physical calculations that affect the TEMPEST hydrodynamic flow calculations. The yield strength model of non-Newtonian sludge correlates yield to a power function of solids concentration. Likewise, shear stress is concentration-dependent, and the dissolution/precipitation chemistry calculations develop the species concentration evolution that produces fluid flow resistance changes. Dilution of waste with pure water, molar concentrations of sodium hydroxide, and other chemical streams can be analyzed for the reactive species changes and hydrodynamic flow characteristics.

  13. 25 CFR 11.605 - Dissolution.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... dissolution of marriage if: (1) The court finds that the marriage is irretrievably broken, if the finding is... affecting the attitude of one or both of the parties towards the marriage; (2) The court finds that either... of marriage, the Court of Indian Offenses shall grant the decree in that form unless the other...

  14. 25 CFR 11.605 - Dissolution.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... dissolution of marriage if: (1) The court finds that the marriage is irretrievably broken, if the finding is... affecting the attitude of one or both of the parties towards the marriage; (2) The court finds that either... of marriage, the Court of Indian Offenses shall grant the decree in that form unless the other...

  15. 25 CFR 11.605 - Dissolution.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... dissolution of marriage if: (1) The court finds that the marriage is irretrievably broken, if the finding is... affecting the attitude of one or both of the parties towards the marriage; (2) The court finds that either... of marriage, the Court of Indian Offenses shall grant the decree in that form unless the other...

  16. 25 CFR 11.605 - Dissolution.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... dissolution of marriage if: (1) The court finds that the marriage is irretrievably broken, if the finding is... affecting the attitude of one or both of the parties towards the marriage; (2) The court finds that either... of marriage, the Court of Indian Offenses shall grant the decree in that form unless the other...

  17. Effect of background electrolytes on gypsum dissolution

    NASA Astrophysics Data System (ADS)

    Burgos-Cara, Alejandro; Putnis, Christine; Ruiz-Agudo, Encarnacion

    2015-04-01

    Knowledge of the dissolution behaviour of gypsum (CaSO4· 2H2O) in aqueous solutions is of primary importance in many natural and technological processes (Pachon-Rodriguez and Colombani, 2007), including the weathering of rocks and gypsum karst formations, deformation of gypsum-bearing rocks, the quality of drinking water, amelioration of soil acidity, scale formation in the oil and gas industry or measurement of water motion in oceanography. Specific ions in aqueous solutions can play important but very different roles on mineral dissolution. For example, the dissolution rates and the morphology of dissolution features may be considerably modified by the presence of the foreign ions in the solution, which adsorb at the surface and hinder the detachment of the ions building the crystal. Dissolution processes in the aqueous environment are closely related to the rearrangement of water molecules around solute ions and the interaction between the solvent molecules themselves. The rearrangement of water molecules with respect to solute species has been recognized as the main kinetic barrier for crystal dissolution in many systems (Davis, 2000; De Yoreo and Dove 2004; Wasylenki et al. 2005). Current research suggest that the control that electrolytes exert on water structure is limited to the local environment surrounding the ions and is not related to long-range electric fields emanating from the ions but results from effects associated with the hydration shell(s) of the ions (Collins et al. 2007) and the ions' capacity to break or structure water (i.e. chaotropic and kosmotropic ions, respectively). These effects will ultimately affect the kinetics of crystal dissolution, and could be correlated with the water affinity of the respective background ions following a trend known as the lyotropic or Hofmeister series (Kunz et al. 2004; Dove and Craven, 2005). In situ macroscopic and Atomic Force Microscopy (AFM) flow-through dissolution experiments were conducted at a

  18. A novel determination of calcite dissolution kinetics in seawater

    NASA Astrophysics Data System (ADS)

    Subhas, Adam V.; Rollins, Nick E.; Berelson, William M.; Dong, Sijia; Erez, Jonathan; Adkins, Jess F.

    2015-12-01

    We present a novel determination of the dissolution kinetics of inorganic calcite in seawater. We dissolved 13 C -labeled calcite in unlabeled seawater, and traced the evolving δ13 C composition of the fluid over time to establish dissolution rates. This method provides sensitive determinations of dissolution rate, which we couple with tight constraints on both seawater saturation state and surface area of the dissolving minerals. We have determined dissolution rates for two different abiotic calcite materials and three different grain sizes. Near-equilibrium dissolution rates are highly nonlinear, and are well normalized by geometric surface area, giving an empirical dissolution rate dependence on saturation state (Ω) of: This result substantiates the non-linear response of calcite dissolution to undersaturation. The bulk dissolution rate constant calculated here is in excellent agreement with those determined in far from equilibrium and dilute solution experiments. Plots of dissolution versus undersaturation indicates the presence of at least two dissolution mechanisms, implying a criticality in the calcite-seawater system. Finally, our new rate determination has implications for modeling of pelagic and seafloor dissolution. Nonlinear dissolution kinetics in a simple 1-D lysocline model indicate a possible transition from kinetic to diffusive control with increasing water depth, and also confirm the importance of respiration-driven dissolution in setting the shape of the calcite lysocline.

  19. The chlorinated AHR ligand 3,3′,4,4′,5-pentachlorobiphenyl (PCB126) promotes reactive oxygen species (ROS) production during embryonic development in the killifish (Fundulus heteroclitus)

    USGS Publications Warehouse

    Arzuaga, Xabier; Wassenberg, Deena; Giulio, Richard D.; Elskus, Adria

    2006-01-01

    Exposure to dioxin-like chemicals that activate the aryl hydrocarbon receptor (AHR) can result in increased cellular and tissue production of reactive oxygen species (ROS). Little is known of these effects during early fish development. We used the fish model, Fundulus heteroclitus, to determine if the AHR ligand and pro-oxidant 3,3′,4,4′,5-pentachlorobiphenyl (PCB126) can increase ROS production during killifish development, and to test a novel method for measuring ROS non-invasively in a living organism. The superoxide-sensitive fluorescent dye, dihydroethidium (DHE), was used to detect in ovo ROS production microscopically in developing killifish exposed to PCB126 or vehicle. Both in ovo CYP1A activity (ethoxyresorufin-o-deethylase, EROD) and in ovo ROS were induced by PCB126. In ovo CYP1A activity was inducible by PCB126 concentrations as low as 0.003 nM, with maximal induction occurring at 0.3 nM PCB126. These PCB126 concentrations also significantly increased in ovo ROS production in embryonic liver, ROS being detectable as early as 5 days post-fertilization. These data demonstrate that the pro-oxidant and CYP1A inducer, PCB126, increases both CYP1A activity and ROS production in developing killifish embryos. The superoxide detection assay (SoDA) described in this paper provides a semi-quantitative, easily measured, early indicator of altered ROS production that can be used in conjunction with simultaneous in ovo measurements of CYP1A activity and embryo development to explore functional relationships among biochemical, physiological and developmental responses to AHR ligands.

  20. Adenovirus E3/19K Promotes Evasion of NK Cell Recognition by Intracellular Sequestration of the NKG2D Ligands Major Histocompatibility Complex Class I Chain-Related Proteins A and B▿

    PubMed Central

    McSharry, Brian P.; Burgert, Hans-Gerhard; Owen, Douglas P.; Stanton, Richard J.; Prod'homme, Virginie; Sester, Martina; Koebernick, Katja; Groh, Veronika; Spies, Thomas; Cox, Steven; Little, Ann-Margaret; Wang, Eddie C. Y.; Tomasec, Peter; Wilkinson, Gavin W. G.

    2008-01-01

    The adenovirus (Ad) early transcription unit 3 (E3) encodes multiple immunosubversive functions that are presumed to facilitate the establishment and persistence of infection. Indeed, the capacity of E3/19K to inhibit transport of HLA class I (HLA-I) to the cell surface, thereby preventing peptide presentation to CD8+ T cells, has long been recognized as a paradigm for viral immune evasion. However, HLA-I downregulation has the potential to render Ad-infected cells vulnerable to natural killer (NK) cell recognition. Furthermore, expression of the immediate-early Ad gene E1A is associated with efficient induction of ligands for the key NK cell-activating receptor NKG2D. Here we show that while infection with wild-type Ad enhances synthesis of the NKG2D ligands, major histocompatibility complex class I chain-related proteins A and B (MICA and MICB), their expression on the cell surface is actively suppressed. Both MICA and MICB are retained within the endoplasmic reticulum as immature endoglycosidase H-sensitive forms. By analyzing a range of cell lines and viruses carrying mutated versions of the E3 gene region, E3/19K was identified as the gene responsible for this activity. The structural requirements within E3/19K necessary to sequester MICA/B and HLA-I are similar. In functional assays, deletion of E3/19K rendered Ad-infected cells more sensitive to NK cell recognition. We report the first NK evasion function in the Adenoviridae and describe a novel function for E3/19K. Thus, E3/19K has a dual function: inhibition of T-cell recognition and NK cell activation. PMID:18287244

  1. Dissolution of two NWCF calcines: Extent of dissolution and characterization of undissolved solids

    SciTech Connect

    Brewer, K.N.; Herbst, R.S.; Tranter, T.J.

    1995-01-01

    A study was undertaken to determine the dissolution characteristics of two NWCF calcine types. A two-way blended calcine made from 4 parts nonradioactive aluminum nitrate and one part WM-102 was studied to determine the extent of dissolution for aluminum-type calcines. A two-way blend of 3.5 parts fluorinel waste from WM-187 and 1 part sodium waste from WM-185 was used to determine the extent of dissolution for zirconium-type calcines. This study was necessary to develop suitable aqueous separation flowsheets for the partitioning of actinides and fission products from ICPP calcines and to determine the disposition of the resulting undissolved solids (UDS). The dissolution flowsheet developed by Herbst was used to dissolve these two NWCF calcine types. Results show that greater than 95 wt% of aluminum and zirconium calcine types were dissolved after a single batch contact with 5 M HNO{sub 3}. A characterization of the UDS indicates that the weight percent of TRU elements in the UDS resulting from both calcine type dissolutions increases by approximately an order of magnitude from their concentrations prior to dissolution. Substantial activities of cesium and strontium are also present in the UDS resulting from the dissolution of both calcine types. Multiple TRU, Cs, and Sr analyses of both UDS types show that these solids are relatively homogeneous. From this study, it is estimated that between 63.5 and 635 cubic meters of UDS will be generated from the dissolution of 3800 M{sub 3} of calcine. The significant actinide and fission product activities in these UDS will preclude their disposal as low-level waste. If the actinide and fission activity resulting from the UDS is the only considered source in the dissolved calcine solutions, an estimated 99.9 to 99.99 percent of the solids must be removed from this solution for it to meet non-TRU Class A low-level waste.

  2. An Investigation of Density Driven Salt Dissolution Techniques

    SciTech Connect

    Wiersma, B.J.

    1998-03-01

    Laboratory experiments were performed to support the salt dissolution demonstration in Tank 41H. The desire was to improve upon past salt dissolution operations and develop a safe, efficient and cost effective means for future operations.

  3. In vitro Dissolution Studies on Solid Dispersions of Mefenamic Acid

    PubMed Central

    Rao, K. R. S. Sambasiva; Nagabhushanam, M V; Chowdary, K. P. R.

    2011-01-01

    Solid dispersions of mefanamic acid with a water-soluble polymer polyvinyl pyrrolidine and a super disintegrant, primojel were prepared by common solvent and solvent evaporation methods employing methanol as the solvent. The dissolution rate and dissolution efficiency of the prepared solid dispersions were evaluated in comparison to the corresponding pure drug. Solid dispersions of mefenamic acid showed a marked enhancement in dissolution rate and dissolution efficiency. At 1:4 ratio of mefenamic acid-primojel a 2.61 fold increase in the dissolution rate of mefenamic acid was observed with solid dispersion. The solid dispersions in combined carriers gave much higher rates of dissolution than super disintegrants alone. Mefanamic acid-primojel-polyvinyl pyrrolidine (1:3.2:0.8) solid dispersion gave a 4.11 fold increase in the dissolution rate of mefenamic acid. Super disintegrants alone or in combination with polyvinyl pyrrolidine could be used to enhance the dissolution rate of mefenamic acid. PMID:22303074

  4. Dissolution Kinetics of Biogenic Magnesian Calcites

    NASA Astrophysics Data System (ADS)

    Thompson, R.; Guidry, M.; Mackenzie, F. T.; De Carlo, E. H.

    2014-12-01

    Ocean acidification (OA) is a serious concern for the health of calcifying ecosystems in the near future. During the past century, surface ocean pH has decreased by ~0.1 pH units, and is expected to decrease further by 0.3-0.4 pH units by the end of this century. The process of OA will likely result in both decreased calcification rates and increased rates of carbonate mineral dissolution, particularly involving the magnesian calcite (Mg-calcite) calcifiers found in shallow-water reef and other carbonate environments. Many Mg-calcite compositions are the most soluble of the carbonate phases commonly found in reef environments (often comprising much of the cementation and structure within a reef), and are therefore potentially the most susceptible to dissolution processes associated with OA. However, the dissolution kinetics of these phases is poorly known, limiting our ability to understand their behavior in nature. Laboratory experiments designed to investigate the mechanisms and dissolution rates of biogenic Mg-calcite mineral phases in distilled water and seawater over a range of CO2 and T conditions were conducted employing both batch and fluidized-bed reactor systems and using a variety of cleaned and annealed biogenic Mg-calcite phases. Our initial results have shown that the dissolution rate at 298 K and a pCO2 of ~350 ppm of the crustose coralline alga Amphiroa rigida (~20 mol% MgCO3) in seawater undersaturated with respect to this phase is 3.6 μmol g-1 hr-1, nearly 50% greater than that under similar conditions for aragonite. This rate and the derived experimental rate law are consistent with the preliminary findings of Walter and Morse (1985). Additional kinetic (and also solubility) data will be presented for the following species: Chiton tuberculatus (~0-4 mol% MgCO3); Echinometra mathei and/or Lytechinus variegatus (~8-12 mol% MgCO3); Homotrema rubrum (12-16 mol% MgCO3); and Lithothamnion sp. (~18-24 mol% MgCO3). Quantification of the rates of

  5. Montmorillonite Dissolution in Simulated Lung Fluids

    NASA Astrophysics Data System (ADS)

    Schmidt, M.; Wendlandt, R. F.

    2008-12-01

    Because lung fluids" first interaction is with the surface of inhaled grains, the surface properties of inhaled mineral dusts may have a generally mitigating effect on cytotoxicity and carcinogenicity. Wendlandt et al. (Appl. Geochem. 22, 2007) investigated the surface properties of respirable-sized quartz grains in bentonites and recognized pervasive montmorillonite surface coatings on silica grains. The purpose of this study was to determine the dissolution rate and biodurability of montmorillonite in simulated lung fluids and to assess its potential to mitigate silica cytotoxicity. Modified batch reaction experiments were conducted on purified and size fractionated calcic (SAz-2; 0.4-5 μm) and sodic (DC-2; 0.4-2 μm) montmorillonites for 120 to 160 days of reaction time at 37°C in both simulated extracellular lung fluid (Lu) and simulated lysosomal fluid (Ly). Modified batch experiments simulated a flow-through setup and minimized sample handling difficulties. Reacted Lu and Ly fluid was analyzed for Mg, Al, and Si on an ICP-OE spectrometer. Steady state dissolution was reached 90-100 days after the start of the experiment and maintained for 40-60 days. Measured montmorillonite dissolution rates based on BET surface areas and Si steady state release range from 4.1x10-15 mol/m2/s at the slowest to 1.0x10-14 mol/m2/s at the fastest with relative uncertainties of less than 10%. Samples reacting in Ly (pH = 4.55) dissolved faster than those in Lu (pH = 7.40), and DC-2 dissolved faster than SAz-2. The measured range of biodurabilities was 1,300 to 3,400 years for a 1 μm grain assuming a spherical volume and a molar volume equal to that of illite. The difference in salinities of the two fluids was too slight to draw conclusions about the relationship of ionic strength to dissolution rate. Results indicate that montmorillonite dissolution is incongruent and edge controlled. Dissolution rates for DC- 2 and SAz-2 clays were comparable to those reported in the

  6. Examining Two Types of Best Friendship Dissolution during Early Adolescence

    ERIC Educational Resources Information Center

    Bowker, Julie C.

    2011-01-01

    This study examined young adolescents' experiences with best friendship dissolution. Participants were 77 sixth-grade students (M age = 11.63 years, SD = 0.36; 11.00-12.69 age range) who reported on past experiences with (1) "complete dissolutions" (when friendship ties are completely severed), and (2) "downgrade dissolutions" (when the best…

  7. Characterization and Dissolution Kinetics Testing of Radioactive H-3 Calcine

    SciTech Connect

    Garn, Troy Gerry; Batcheller, Thomas Aquinas

    2002-09-01

    Characterization and dissolution kinetics testing were performed with Idaho radioactive H-3 calcine. Calcine dissolution is the key front-end unit operation for the Separations Alternative identified in the Idaho High Level Waste Draft EIS. The impact of the extent of dissolution on the feasibility of Separations must be clearly quantified.

  8. A select set of opioid ligands induce up-regulation by promoting the maturation and stability of the rat kappa-opioid receptor in human embryonic kidney 293 cells.

    PubMed

    Wannemacher, Kenneth M; Yadav, Prem N; Howells, Richard D

    2007-11-01

    Ligand-induced regulation of the rat kappa-opioid receptor (rKOR) was investigated in human embryonic kidney 293 cells stably expressing the FLAG-tagged rKOR. Incubation of rKOR cells with naltrexone for 24 h increased the B(max) >3-fold, with no change in the affinity of [(3)H]diprenorphine. Two immunoreactive receptor species were present in cell lysates: naltrexone treatment caused a >3-fold increase in the 52-kDa species while decreasing the level of the 42-kDa species. Dynorphin(1-13), U69,593 [(5alpha,7alpha,8beta)-(+)-N-methyl-N-(7-[1-pyrrolidinyl]-1-oxaspiro[4,5]dec-8-yl)benzeneacetamide], or salvinorin A [2S,4aR,6aR,7R,9S,10aS, 10bR)-9-(acetyloxy)-2-(3-furanyl)dodecahydro-6a,10b-dimethyl-4,10-dioxo-2H-naphtho[2,1c]pyran-7-carboxylic acid methyl ester] treatment did not alter the level of immunoreactive rKOR protein, whereas etorphine, cyclazocine, naloxone, and naloxone methiodide increased the 52-kDa and decreased the 42-kDa rKOR bands. Receptor up-regulation was associated with an increase in the number of cell surface receptors and a 2-fold increase in the E(max) for guanosine 5'-O-(3-[(35)S]thio)triphosphate binding. Glycosidase digestion indicated that the 52- and 42-kDa receptors contained complex and high-mannose N-glycans, respectively, Pulse-chase analysis and glycosidase digestion sensitivities suggested that the 42-kDa rKOR species was a precursor of the 52-kDa species. Naltrexone did not alter rKOR mRNA levels or translational efficiency, and rKOR up-regulation was not inhibited by cycloheximide. Brefeldin A caused accumulation of intracellular rKOR intermediates, and coincubation with naltrexone increased the levels of the brefeldin-induced species significantly. These results suggest that select opioid ligands up-regulate rKOR by enhancing the rate of receptor folding and maturation and by protecting the receptor from degradation, resulting in an increase in the number of rKOR binding sites, immunoreactive protein, and functional receptors

  9. Ego-Dissolution and Psychedelics: Validation of the Ego-Dissolution Inventory (EDI)

    PubMed Central

    Nour, Matthew M.; Evans, Lisa; Nutt, David; Carhart-Harris, Robin L.

    2016-01-01

    Aims: The experience of a compromised sense of “self”, termed ego-dissolution, is a key feature of the psychedelic experience. This study aimed to validate the Ego-Dissolution Inventory (EDI), a new 8-item self-report scale designed to measure ego-dissolution. Additionally, we aimed to investigate the specificity of the relationship between psychedelics and ego-dissolution. Method: Sixteen items relating to altered ego-consciousness were included in an internet questionnaire; eight relating to the experience of ego-dissolution (comprising the EDI), and eight relating to the antithetical experience of increased self-assuredness, termed ego-inflation. Items were rated using a visual analog scale. Participants answered the questionnaire for experiences with classical psychedelic drugs, cocaine and/or alcohol. They also answered the seven questions from the Mystical Experiences Questionnaire (MEQ) relating to the experience of unity with one’s surroundings. Results: Six hundred and ninety-one participants completed the questionnaire, providing data for 1828 drug experiences (1043 psychedelics, 377 cocaine, 408 alcohol). Exploratory factor analysis demonstrated that the eight EDI items loaded exclusively onto a single common factor, which was orthogonal to a second factor comprised of the items relating to ego-inflation (rho = −0.110), demonstrating discriminant validity. The EDI correlated strongly with the MEQ-derived measure of unitive experience (rho = 0.735), demonstrating convergent validity. EDI internal consistency was excellent (Cronbach’s alpha 0.93). Three analyses confirmed the specificity of ego-dissolution for experiences occasioned by psychedelic drugs. Firstly, EDI score correlated with drug-dose for psychedelic drugs (rho = 0.371), but not for cocaine (rho = 0.115) or alcohol (rho = −0.055). Secondly, the linear regression line relating the subjective intensity of the experience to ego-dissolution was significantly steeper for psychedelics

  10. Co-culture of primary CLL cells with bone marrow mesenchymal cells, CD40 ligand and CpG ODN promotes proliferation of chemoresistant CLL cells phenotypically comparable to those proliferating in vivo

    PubMed Central

    Purroy, Noelia; Abrisqueta, Pau; Carabia, Júlia; Carpio, Cecilia; Palacio, Carles

    2015-01-01

    Chronic lymphocytic leukemia (CLL) cells residing in the bone marrow (BM) and in secondary lymphoid tissues receive survival and proliferative signals from the microenvironment, resulting in persistence of residual disease after treatment. In this study, we characterized primary CLL cells cultured with BM stromal cells, CD40 ligand and CpG ODN to partially mimic the microenvironment in the proliferative centers. This co-culture system induced proliferation and chemoresistance in primary CLL cells. Importantly, co-cultured primary CLL cells shared many phenotypical features with circulating proliferative CLL cells, such as upregulation of ZAP-70 and CD38 and higher CD49d and CD62L expression. This indicates aggressiveness and capability to interact with surrounding cells, respectively. In addition, levels of CXCR4 were decreased due to CXCR4 internalization after CXCL12 stimulation by BM stromal cells. We suggest that this co-culture system can be used to test drugs and their combinations that target the proliferative and drug resistant CLL cells. PMID:25544766

  11. A morpholinium ionic liquid for cellulose dissolution.

    PubMed

    Raut, Dilip G; Sundman, Ola; Su, Weiqing; Virtanen, Pasi; Sugano, Yasuhito; Kordas, Krisztian; Mikkola, Jyri-Pekka

    2015-10-01

    A series of substituted morpholinium ionic salts and allyl ammonium acetates were prepared. Amongst those, N-allyl-N-methylmorpholinium acetate ([AMMorp][OAc]) was found to dissolve cellulose readily without any pre-processing of native cellulose. At 120°C, [AMMorp][OAc] could dissolve 30 wt%, 28 wt% and 25 wt% of cellulose with degree of polymerization (DPn) - 789, 1644 and 2082 respectively, in 20 min. Importantly, SEC analysis indicated that no discernible changes occurred in terms of the degree of polymerization of the different celluloses after regeneration. Furthermore, when comparing the cellulose dissolution capability of these newly synthesized ionic liquids, it is evident that the combination of all three constituents - the morpholinium cation, the existence of an allyl group and choosing the acetate anion are essential for efficient cellulose dissolution. The structure and morphology of the regenerated cellulosic materials were characterized by SEM, XRD, TGA, CP/MAS (13)C NMR and FTIR, respectively. PMID:26076596

  12. Uranium-Molybdenum Dissolution Flowsheet Studies

    SciTech Connect

    Pierce, R. A.

    2007-03-01

    The Super Kukla (SK) Prompt Burst Reactor operated at the Nevada Test Site from 1964 to 1978. The SK material is a uranium-molybdenum (U-Mo) alloy material of 90% U/10% Mo by weight at approximately 20% 235U enrichment. H-Canyon Engineering (HCE) requested that the Savannah River National Lab (SRNL) define a flowsheet for safely and efficiently dissolving the SK material. The objective is to dissolve the material in nitric acid (HNO3) in the H-Canyon dissolvers to a U concentration of 15-20 g/L (3-4 g/L 235U) without the formation of precipitates or the generation of a flammable gas mixture. Testing with SK material validated the applicability of dissolution and solubility data reported in the literature for various U and U-Mo metals. Based on the data, the SK material can be dissolved in boiling 3.0-6.0 M HNO3 to a U concentration of 15-20 g/L and a corresponding Mo concentration of 1.7-2.2 g/L. The optimum flowsheet will use 4.0-5.0 M HNO3 for the starting acid. Any nickel (Ni) cladding associated with the material will dissolve readily. After dissolution is complete, traditional solvent extraction flowsheets can be used to recover and purify the U. Dissolution rates for the SK material are consistent with those reported in the literature and are adequate for H-Canyon processing. When the SK material dissolved at 70-100 o C in 1-6 M HNO3, the reaction bubbled vigorously and released nitrogen oxide (NO) and nitrogen dioxide (NO2) gas. Gas generation tests in 1 M and 2 M HNO3 at 100 o C generated less than 0.1 volume percent hydrogen (H2) gas. It is known that higher HNO3 concentrations are less favorable for H2 production. All tests at 70-100 o C produced sufficient gas to mix the solutions without external agitation. At room temperature in 5 M HNO3, the U-Mo dissolved slowly and the U-laden solution sank to the bottom of the dissolution vessel because of its greater density. The effect of the density difference insures that the SK material cannot dissolve and

  13. Bile acid dissolution therapy of gallbladder stones.

    PubMed

    Fromm, H; Malavolti, M

    1992-11-01

    Oral cholelitholytic bile acid therapy has become established treatment for selected patients with cholesterol gallstones. The treatment finds its clinical application both alone and in combination with ESWL. UDCA alone or, less commonly, a combination of this bile acid with CDCA is used. Optimal results can be expected only in carefully selected patients. Bile acid dissolution therapy is most successful in patients with radiolucent gallstones which are < or = 0.5 cm in diameter or are shown by OCG to be floating. Dissolution is seldom seen when the stones are > 1 cm in size. Cholelitholytic treatment in combination with ESWL yields optimal results in single radiolucent gallstones which are not greater than 2 cm. ESWL thus makes it possible to use medical treatment effectively in single 1-2 cm gallstones when bile acids alone would not be successful. Bile acid treatment is extremely safe, especially if UDCA is given without the addition of CDCA. PMID:1486209

  14. The Dissolution of an Interfween Miscible Liquids

    NASA Technical Reports Server (NTRS)

    Vlad, D.H.; Maher, J.V.

    1999-01-01

    The disappearance of the surface tension of the interface of a binary mixture, measured using the dynamic surface light scattering technique, is slower for a binary mixture of higher density contrast. A comparison with a naive diffusion model, expected to provide a lower limit for the speed of dissolution in the absence of gravity shows that the interfacial surface tension disappears much slower than even by diffusion with the effect becoming much more pronounced when density contrast between the liquid phases is increased. Thus, the factor most likely to be responsible for this anomalously slow dissolution is gravity. A mechanism could be based on the competition between diffusive relaxation and sedimentation at the dissolving interface.

  15. Calcite dissolution in two deep eutrophic lakes

    SciTech Connect

    Ramisch, F.; Dittrich, M.; Mattenberger, C.; Wehrli, B.; Wueest, A.

    1999-10-01

    The calcium cycle, in particular carbonate dissolution, was analyzed in two deep eutrophic lakes, Lago di Lugano (288 m maximum depth) and Sempachersee (87 m) located in Switzerland. A box model approach was used to calculate calcite dissolution in the water column and at the sediment-water interface based on various lake monitoring data such as sediment traps, sediment cores, water and pore-water interface based on various lake monitoring data such as sediment traps, sediment cores, water and pore-water analysis. A model for stationary conditions allowing the calculation of calcite dissolution in the water column for a given particle size distribution was developed. The relative values of the simulated flux were consistent with sediment trap observations. The best fit of the dissolution rate constant of sinking calcite in Lago di Lugano was on the same order of magnitude (3 {center{underscore}dot} 10{sup {minus}10} kg{sup 1/3} s{sup {minus}1}) as published laboratory values for this surface controlled process. Both lakes show a similar specific calcite precipitation rate of 170 g Ca m{sup {minus}2} a{sup {minus}1}. The diffusive flux across the sediment-water interface amounts to about 15 and 10% of total calcite precipitation in Sempachersee and Lago di Lugano, respectively. However, 61% of the precipitated calcite is dissolved in the water column of Lago di Lugano compared to only 13% in Sempachersee. These results point towards the importance of grain size distributions and settling times in stratified deep waters as the two most important factors determining calcite retention in sediments of hard water lakes.

  16. DISSOLUTION OF ZIRCONIUM AND ALLOYS THEREFOR

    DOEpatents

    Swanson, J.L.

    1961-07-11

    The dissolution of zirconium cladding in a water solution of ammonium fluoride and ammonium nitrate is described. The method finds particular utility in processing spent fuel elements for nuclear reactors. The zirconium cladding is first dissolved in a water solution of ammonium fluoride and ammonium nitrate; insoluble uranium and plutonium fiuorides formed by attack of the solvent on the fuel materiai of the fuel element are then separated from the solution, and the fuel materiai is dissolved in another solution.

  17. The impact of changing surface ocean conditions on the dissolution of aerosol iron

    NASA Astrophysics Data System (ADS)

    Fishwick, Matthew P.; Sedwick, Peter N.; Lohan, Maeve C.; Worsfold, Paul J.; Buck, Kristen N.; Church, Thomas M.; Ussher, Simon J.

    2014-11-01

    The proportion of aerosol iron (Fe) that dissolves in seawater varies greatly and is dependent on aerosol composition and the physicochemical conditions of seawater, which may change depending on location or be altered by global environmental change. Aerosol and surface seawater samples were collected in the Sargasso Sea and used to investigate the impact of these changing conditions on aerosol Fe dissolution in seawater. Our data show that seawater temperature, pH, and oxygen concentration, within the range of current and projected future values, had no significant effect on the dissolution of aerosol Fe. However, the source and composition of aerosols had the most significant effect on the aerosol Fe solubility, with the most anthropogenically influenced samples having the highest fractional solubility (up to 3.2%). The impact of ocean warming and acidification on aerosol Fe dissolution is therefore unlikely to be as important as changes in land usage and fossil fuel combustion. Our experimental results also reveal important changes in the size distribution of soluble aerosol Fe in solution, depending on the chemical conditions of seawater. Under typical conditions, the majority (77-100%) of Fe released from aerosols into ambient seawater existed in the colloidal (0.02-0.4 µm) size fraction. However, in the presence of a sufficient concentration of strong Fe-binding organic ligands (10 nM) most of the aerosol-derived colloidal Fe was converted to soluble Fe (<0.02 µm). This finding highlights the potential importance of organic ligands in retaining aerosol Fe in a biologically available form in the surface ocean.

  18. Theoretical Analysis of Drug Dissolution: I. Solubility and Intrinsic Dissolution Rate.

    PubMed

    Shekunov, Boris; Montgomery, Eda Ross

    2016-09-01

    The first-principles approach presented in this work combines surface kinetics and convective diffusion modeling applied to compounds with pH-dependent solubility and in different dissolution media. This analysis is based on experimental data available for approximately 100 compounds of pharmaceutical interest. Overall, there is a linear relationship between the drug solubility and intrinsic dissolution rate expressed through the total kinetic coefficient of dissolution and dimensionless numbers defining the mass transfer regime. The contribution of surface kinetics appears to be significant constituting on average ∼20% resistance to the dissolution flux in the compendial rotating disk apparatus at 100 rpm. The surface kinetics contribution becomes more dominant under conditions of fast laminar or turbulent flows or in cases when the surface kinetic coefficient may decrease as a function of solution composition or pH. Limitations of the well-known convective diffusion equation for rotating disk by Levich are examined using direct computational modeling with simultaneous dissociation and acid-base reactions in which intrinsic dissolution rate is strongly dependent on pH profile and solution ionic strength. It is shown that concept of diffusion boundary layer does not strictly apply for reacting/interacting species and that thin-film diffusion models cannot be used quantitatively in general case. PMID:26906172

  19. LigandRNA: computational predictor of RNA–ligand interactions

    PubMed Central

    Philips, Anna; Milanowska, Kaja; Łach, Grzegorz; Bujnicki, Janusz M.

    2013-01-01

    RNA molecules have recently become attractive as potential drug targets due to the increased awareness of their importance in key biological processes. The increase of the number of experimentally determined RNA 3D structures enabled structure-based searches for small molecules that can specifically bind to defined sites in RNA molecules, thereby blocking or otherwise modulating their function. However, as of yet, computational methods for structure-based docking of small molecule ligands to RNA molecules are not as well established as analogous methods for protein-ligand docking. This motivated us to create LigandRNA, a scoring function for the prediction of RNA–small molecule interactions. Our method employs a grid-based algorithm and a knowledge-based potential derived from ligand-binding sites in the experimentally solved RNA–ligand complexes. As an input, LigandRNA takes an RNA receptor file and a file with ligand poses. As an output, it returns a ranking of the poses according to their score. The predictive power of LigandRNA favorably compares to five other publicly available methods. We found that the combination of LigandRNA and Dock6 into a “meta-predictor” leads to further improvement in the identification of near-native ligand poses. The LigandRNA program is available free of charge as a web server at http://ligandrna.genesilico.pl. PMID:24145824

  20. Analysis of macromolecules, ligands and macromolecule-ligand complexes

    DOEpatents

    Von Dreele, Robert B.

    2008-12-23

    A method for determining atomic level structures of macromolecule-ligand complexes through high-resolution powder diffraction analysis and a method for providing suitable microcrystalline powder for diffraction analysis are provided. In one embodiment, powder diffraction data is collected from samples of polycrystalline macromolecule and macromolecule-ligand complex and the refined structure of the macromolecule is used as an approximate model for a combined Rietveld and stereochemical restraint refinement of the macromolecule-ligand complex. A difference Fourier map is calculated and the ligand position and points of interaction between the atoms of the macromolecule and the atoms of the ligand can be deduced and visualized. A suitable polycrystalline sample of macromolecule-ligand complex can be produced by physically agitating a mixture of lyophilized macromolecule, ligand and a solvent.

  1. Mineral dissolution kinetics at the pore scale

    SciTech Connect

    Li, L.; Steefel, C.I.; Yang, L.

    2007-05-24

    Mineral dissolution rates in the field have been reported to be orders of magnitude slower than those measured in the laboratory, an unresolved discrepancy that severely limits our ability to develop scientifically defensible predictive or even interpretive models for many geochemical processes in the earth and environmental sciences. One suggestion links this discrepancy to the role of physical and chemical heterogeneities typically found in subsurface soils and aquifers in producing scale-dependent rates where concentration gradients develop. In this paper, we examine the possibility that scale-dependent mineral dissolution rates can develop even at the single pore and fracture scale, the smallest and most fundamental building block of porous media. To do so, we develop two models to analyze mineral dissolution kinetics at the single pore scale: (1) a Poiseuille Flow model that applies laboratory-measured dissolution kinetics at the pore or fracture wall and couples this to a rigorous treatment of both advective and diffusive transport, and (2) a Well-Mixed Reactor model that assumes complete mixing within the pore, while maintaining the same reactive surface area, average flow rate, and geometry as the Poiseuille Flow model. For a fracture, a 1D Plug Flow Reactor model is considered in addition to quantify the effects of longitudinal versus transverse mixing. The comparison of averaged dissolution rates under various conditions of flow, pore size, and fracture length from the three models is used as a means to quantify the extent to which concentration gradients at the single pore and fracture scale can develop and render rates scale-dependent. Three important minerals that dissolve at widely different rates, calcite, plagioclase, and iron hydroxide, are considered. The modeling indicates that rate discrepancies arise primarily where concentration gradients develop due to comparable rates of reaction and advective transport, and incomplete mixing via molecular

  2. Peridotite dissolution and carbonation rates at fracture surfaces under conditions relevant for in situ mineralization of CO2

    NASA Astrophysics Data System (ADS)

    van Noort, R.; Spiers, C. J.; Drury, M. R.; Kandianis, M. T.

    2013-04-01

    Whereas the dissolution of pure single phases (e.g. olivine and other mafic minerals) has been the focus of many studies, no investigation has been reported on the progress of reactions at and within polymineralic, transgranular fracture surfaces cutting peridotites. We document experiments that address the evolution of dissolving peridotite surfaces, and the rates of dissolution and carbonation reactions that occur at these surfaces, under both open- and closed-system conditions relevant for in situ CO2-sequestration. The results of experiments, conducted under quasi-open system conditions, on solid samples of peridotite whose surfaces were taken as an analogue of free fracture surfaces, demonstrate apparent rates of olivine dissolution at the free surfaces that are equivalent to or upwards of 100 times greater than those determined for pure olivine under similar conditions. This increase in apparent olivine dissolution rate is ascribed to fluid penetration along grain boundaries and veins, which resulted in increased accessibility of reactive olivine surface area. Apparent dissolution rates under closed system conditions, where serial olivine dissolution and magnesite precipitation take place, are ˜1 order of magnitude slower owing to changes in fluid composition and pH. In both of these reaction environments, it is apparent that serpentinized veins and mineral grain boundaries within the peridotite allowed fluids to penetrate the rock and to promote the release of divalent metals and silica from within the sample or simulated fracture walls. These results indicate that the microstructure of free (fracture) surfaces exerts a dominant control on peridotite dissolution and carbonation rates, relative to the proportion of highly reactive minerals that compose such ultramafic rock. The rapid dissolution we observe under open system conditions implies that CO2-mineralization may be viable, in open systems, if the composition of injected fluids can be maintained at or

  3. Suppressing Manganese Dissolution from Lithium Manganese Oxide Spinel Cathodes with Single-Layer Graphene

    SciTech Connect

    Jaber-Ansari, Laila; Puntambekar, Kanan P.; Kim, Soo; Aykol, Muratahan; Luo, Langli; Wu, Jinsong; Myers, Benjamin D.; Iddir, Hakim; Russell, John T.; Saldana, Spencer J.; Kumar, Rajan; Thackeray, Michael M.; Curtiss, Larry A.; Dravid, Vinayak P.; Wolverton, Christopher M.; Hersam, Mark C.

    2015-06-24

    Spinel-structured LiMn 2 O 4 (LMO) is a desirable cathode material for Li-ion batteries due to its low cost, abundance, and high power capability. However, LMO suffers from limited cycle life that is triggered by manganese dissolution into the electrolyte during electrochemical cycling. Here, it is shown that single-layer graphene coatings suppress manganese dissolution, thus enhancing the performance and lifetime of LMO cathodes. Relative to lithium cells with uncoated LMO cathodes, cells with graphene-coated LMO cathodes provide improved capacity retention with enhanced cycling stability. X-ray photoelectron spectroscopy reveals that graphene coatings inhibit manganese depletion from the LMO surface. Additionally, transmission electron microscopy demonstrates that a stable solid electrolyte interphase is formed on graphene, which screens the LMO from direct contact with the electrolyte. Density functional theory calculations provide two mechanisms for the role of graphene in the suppression of manganese dissolution. First, common defects in single-layer graphene are found to allow the transport of lithium while concurrently acting as barriers for manganese diffusion. Second, graphene can chemically interact with Mn 3+ at the LMO electrode surface, promoting an oxidation state change to Mn 4+ , which suppresses dissolution.

  4. Magnesite growth inhibition by organic ligands: An experimental study at 100, 120 and 146 °C

    NASA Astrophysics Data System (ADS)

    Gautier, Quentin; Bénézeth, Pascale; Schott, Jacques

    2016-05-01

    It has been proposed that simple organic ligands, which accelerate Mg-silicates dissolution, could be used to accelerate CO2 mineral sequestration through mineral carbonation. The influence of these ligands on magnesite growth has however never been quantified. In this work, we investigated the influence of three organic ligands: oxalate, citrate and EDTA on magnesite growth in alkaline conditions and at hydrothermal temperatures (100, 120 and 146 °C) using mixed flow reactors. We show that the studied carboxylates decrease magnesite growth rates, due to two converging mechanisms:

  5. EGF receptor ligands: recent advances

    PubMed Central

    Singh, Bhuminder; Carpenter, Graham; Coffey, Robert J.

    2016-01-01

    Seven ligands bind to and activate the mammalian epidermal growth factor (EGF) receptor (EGFR/ERBB1/HER1): EGF, transforming growth factor-alpha (TGFA), heparin-binding EGF-like growth factor (HBEGF), betacellulin (BTC), amphiregulin (AREG), epiregulin (EREG), and epigen (EPGN). Of these, EGF, TGFA, HBEGF, and BTC are thought to be high-affinity ligands, whereas AREG, EREG, and EPGN constitute low-affinity ligands. This focused review is meant to highlight recent studies related to actions of the individual EGFR ligands, the interesting biology that has been uncovered, and relevant advances related to ligand interactions with the EGFR.

  6. The combined effect of temperature and pH on albite dissolution rate under far-from-equilibrium conditions

    NASA Astrophysics Data System (ADS)

    Gruber, Chen; Kutuzov, Ilya; Ganor, Jiwchar

    2016-08-01

    Two of the most studied aspects of albite dissolution kinetics are the effects of temperature and pH. Previous studies quantified the effect of pH on albite dissolution rate under constant temperature. These studies suggested that the effect of pH on dissolution rate can be attributed to three independent dissolution mechanisms that are dominant in different pH region: acidic - proton-promoted, neutral - water-promoted and alkaline - hydroxide-promoted. Based on experimental results, those studies developed a rate law to predict albite dissolution rate as a function of pH, assuming that the effect of pH is temperature independent. The effect of temperature was attributed either to the temperature dependency of the rate under constant pH or that of the rate law coefficients. Nevertheless no unified rate law that combines both effects was suggested. When applying the effects of temperature and pH assuming they are independent of each other in order to predict the dissolution rate at pH of about 5 and various temperatures, the predicted rate overestimate the rate by 0.5-1 order of magnitude. The current study develops and suggests the use of new rate law that is based on two fast adsorption reactions of protons and hydroxides on two different surface sites. The new rate law considers the effect of surface coverage of protons and hydroxides that is temperature dependent. The new rate law successfully describes the variation of albite dissolution rate (about 8 orders of magnitude) under wide temperature (3.6-300 °C) and pH (1.20-12.40) ranges. Under slightly acidic conditions (pH 5-7) the new rate law predicts a minimum rate zone that was not observed before. In order to confirm whether this minimum rate zone does exist, three SPBE (single-point-batch-experiment) of albite dissolution were conducted at pH 5 and temperatures of 3.6, 25 and 50 °C. The SPBE experiments confirm the existence of minimum rate zone predicted by the independent new rate law. The new rate law

  7. Role of root exudates in dissolution of Cd containing iron oxides

    NASA Astrophysics Data System (ADS)

    Rosenfeld, C.; Martinez, C. E.

    2011-12-01

    Dissolved organic matter (DOM) in the rhizosphere contains organic acids, amino acids and more complex organic molecules that can substantially impact the solubility of soil solid phases. Plant roots and soil microorganisms contribute a large fraction of these organic compounds to DOM, potentially accelerating the transfer of solid phase elements into solution. In highly contaminated soils, heavy metals such as Cd are commonly found coprecipitated with common minerals (e.g. iron oxides). Introducing or changing vegetation on these contaminated soils may increase DOM levels in the soil pore fluids and thus enhance the biological and chemical weathering of soil minerals. Here, we investigate the role of root exudates on mineral dissolution and Cd mobility in contaminated soils. We hypothesize that plant exudates containing nitrogen and sulfur functional groups will dissolve Cd-containing mineral phases to a greater extent than exudates containing only oxygen functional groups, resulting in higher Cd concentrations in solution. Two different iron oxide mineral phases were utilized in a laboratory-scale model study system investigating the effects of low molecular weight, oxygen-, nitrogen-, and sulfur-containing organic compounds on mineral dissolution. Goethite (α-FeOOH) was synthesized in the laboratory with 0, 2.4, 5, and 100 theoretical mol% Cd, and franklinite (ZnFe2O4) was prepared with 0, 10, and 25 theoretical mol% Cd. Phase identity of all minerals was verified with X-ray diffraction (XRD). All minerals were reacted with 0.01 mM solutions containing one of four different organic ligands (oxalic acid, citric acid, histidine or cysteine) and aliquots of these solutions were sampled periodically over 40 days. Results from solution samples suggest that oxalic acid, citric acid, and histidine consistently increase mineral dissolution relative to the control (no organic compound present) while cysteine consistently inhibits dissolution relative to the control in

  8. Systematic review of forsterite dissolution rate data

    NASA Astrophysics Data System (ADS)

    Rimstidt, J. Donald; Brantley, Susan L.; Olsen, Amanda A.

    2012-12-01

    This paper demonstrates a method for systematic analysis of published mineral dissolution rate data using forsterite dissolution as an example. The steps of the method are: (1) identify the data sources, (2) select the data, (3) tabulate the data, (4) analyze the data to produce a model, and (5) report the results. This method allows for a combination of critical selection of data, based on expert knowledge of theoretical expectations and experimental pitfalls, and meta-analysis of the data using statistical methods. Application of this method to all currently available forsterite dissolution rates (0 < pH < 14, and 0 < T < 150 °C) normalized to geometric surface area produced the following rate equations: For pH < 5.6 and 0° < T < 150 °C, based on 519 data logr=6.05(0.22)-0.46(0.02)pH-3683.0(63.6)1/T(R2=0.88) For pH > 5.6 and 0° < T < 150 °C, based on 125 data logr=4.07(0.38)-0.256(0.023)pH-3465(139)1/T(R2=0.92) The R2 values show that ˜10% of the variance in r is not explained by variation in 1/T and pH. Although the experimental error for rate measurements should be ± ˜30%, the observed error associated with the log r values is ˜0.5 log units (±300% relative error). The unexplained variance and the large error associated with the reported rates likely arises from the assumption that the rates are directly proportional to the mineral surface area (geometric or BET) when the rate is actually controlled by the concentration and relative reactivity of surface sites, which may be a function of duration of reaction. Related to these surface area terms are other likely sources of error that include composition and preparation of mineral starting material. Similar rate equations were produced from BET surface area normalized rates. Comparison of rate models based on geometric and BET normalized rates offers no support for choosing one normalization method over the other. However, practical considerations support the use of geometric surface area normalization

  9. Dissolution rate enhancement of piroxicam by ordered mixing.

    PubMed

    Saharan, Vikas Anand; Choudhury, Pratim Kumar

    2012-07-01

    Micronized piroxicam was mixed with lactose, mannitol, sorbitol, maltitol and sodium chloride to produce ordered mixture in a glass vial by manual hand shaking method. The effect of excipients, surfactant, superdisintegrant, drug concentration and carrier particle size on dissolution rate was investigated. Dissolution rate studies of the prepared ordered mixtures revealed that all water soluble excipients increased the dissolution rate of piroxicam when compared to the dissolution rate of piroxicam or its suspension. Ordered mixture formulation PLF4, consisting of lactose as water soluble excipient, SSG (8% w/s) and SLS (1% w/w), released piroxcam at a very fast rate so much so that about 90% of the composition had passed into solution within 2 min. The order of the dissolution rate enhancement for ordered mixtures of various water soluble excipients was: lactose > mannitol > maltitol > sorbitol > sodium chloride. Carrier granules of size 355-710 µm were most effective in increasing the dissolution rate of drug from ordered mixtures. Decreasing the carrier particle size reduced drug dissolution from ordered mixtures. The dissolution rate of ordered mixtures consisting of 1-5% w/w piroxicam was superior to dissolution rate of piroxicam suspension. The dissolution data fitting and the resulting regression parameters indicated Hixson Crowell, cube root law, as the best fit to drug release data of ordered mixtures. PMID:22713937

  10. Dissolution kinetics of single crystals of alpha-lactose monohydrate.

    PubMed

    Raghavan, S L; Ristic, R I; Sheen, D B; Sherwood, J N

    2002-10-01

    The dissolution kinetics of alpha-lactose monohydrate (alphaLM) single crystals were studied by a flow-cell method at different undersaturations. Linear dissolution profiles were obtained as a function of time for all the faces except the (010) face. The dissolution rates, obtained from these profiles, were anisotropic and varied considerably with undersaturation. At low undersaturations (0-2%), the order of dissolution rate was (110) > (100) > (011) = (110) > (010). This order changed with increasing undersaturation (>5%) to (011) > (100) > (110) > (110) > (010). In alphaLM crystals in which lattice strain was induced by synchrotron X-irradiation, the rates of dissolution of all faces increased with increasing strain. The increase was less significant for the (011) faces than for the remainder. Under this constraint, the (010) face became the fastest dissolving one and the [011]face became the slowest one. The results of all experiments are explained on the basis that although dislocations may act as initiating dissolution centers at very low undersaturations, these sources rapidly give way to two-dimensional nucleation of randomly distributed dissolution sites as the undersaturation is increased. Under these conditions, which better reflect the normal dissolution processes of materials, bulk lattice strain plays the most significant role in defining the dissolution rate. The results show a potential route to the controlled engineering of the dissolution behavior of crystalline materials. PMID:12226843

  11. Discriminative Dissolution Method for Benzoyl Metronidazole Oral Suspension.

    PubMed

    da Silva, Aline Santos; da Rosa Silva, Carlos Eduardo; Paula, Fávero Reisdorfer; da Silva, Fabiana Ernestina Barcellos

    2016-06-01

    A dissolution method for benzoyl metronidazole (BMZ) oral suspensions was developed and validated using a high-performance liquid chromatography (HPLC) method. After determination of sink conditions, dissolution profiles were evaluated using different dissolution media and agitation speeds. The sample insertion mode in dissolution media was also evaluated. The best conditions were obtained using a paddle, 50 rpm stirring speed, simulated gastric fluid (without pepsin) as the dissolution medium, and sample insertion by a syringe. These conditions were suitable for providing sink conditions and discriminatory power between different formulations. Through the tested conditions, the results can be considered specific, linear, precise, accurate, and robust. The dissolution profiles of five samples were compared using the similarity factor (f 2) and dissolution efficiency. The dissolution kinetics were evaluated and described by the Weibull model. Whereas there is no monograph for this pharmaceutical formulation, the dissolution method proposed can be considered suitable for quality control and dissolution profile comparison of different commercial formulations. PMID:26349689

  12. Interactions between gravity currents and convective dissolution

    NASA Astrophysics Data System (ADS)

    Elenius, M. T.; Voskov, D. V.; Tchelepi, H. A.

    2015-09-01

    Geological storage of carbon dioxide (CO2) is a promising technology for reducing atmospheric emissions. The large discrepancy in the time- and length-scales between up-dip migration of buoyant supercritical CO2 and the sinking fingers of dissolved CO2 poses a challenge for numerical simulations aimed at describing the fate of the plume. Hence, several investigators have suggested methods to simplify the problem, but to date there has been no reference solution with which these simplified models can be compared. We investigate the full problem of Darcy-based two-phase flow with gravity-current propagation and miscible convective mixing, using high-resolution numerical simulations. We build on recent developments of the Automatic Differentiation - General Purpose Research Simulator (AD-GPRS) at Stanford. The results show a CO2 plume that travels for 5000 years reaching a final distance of 14 km up-dip from the injection site. It takes another 2000 years before the CO2 is completely trapped as residual (40%) and dissolved (60%) CO2. Dissolution causes a significant reduction of the plume speed. While fingers of dissolved CO2 appear under the propagating gravity current, the resident brine does not become fully saturated with CO2 anywhere under the plume. The overall mass transfer of CO2 into the brine under the plume remains practically constant for several thousands of years. These results can be used as a benchmark for verification, or improvements, of simplified (reduced-dimensionality, upscaled) models. Our results indicate that simplified models need to account for: (i) reduced dissolution due to interaction with the plume, and (ii) gradual reduction of the local dissolution rate after the fingers begin to interact with the bottom of the aquifer.

  13. Fluorinated dissolution inhibitors for 157-nm lithography

    NASA Astrophysics Data System (ADS)

    Hamad, Alyssandrea H.; Bae, Young C.; Liu, Xiang-Qian; Ober, Christopher K.; Houlihan, Francis M.; Dabbagh, Gary; Novembre, Anthony E.

    2002-07-01

    Fluorinated dissolution inhibitors (DIs) for 157 nm lithography were designed and synthesized as part of an ongoing study on the structure/property relationships of photoresist additives. The problem of volatilization of small DI candidates was observed from matrices such as poly(methyl methacrylate) (PMMA) and poly(hexafluorohydroxy-isopropyl styrene) (PHFHIPS) during post-apply bake cycles using Fourier Transform Infrared Spectroscopy (FT-IR). To avoid this problem, low volatility fluorinated inhibitors were designed and synthesized. Three fluorinated DIs, perfluorosuberic acid bis-(2,2,2,-trifluoro-1-phenyl-1-trifluoromethyl-ethyl) ester (PFSE1), perfluorosuberic acid bis-[1-(4-trifluoromethyl-phenyl)-ethyl] ester (PFSE2) and a fluorinated phenylmethanediol diester (FPMD1), largely remained in a PHFHIPS film during the post-apply bake. The dissolution behavior of the two fluorinated diesters was studied and found to slow down the dissolution rate of PHFHIPS with inhibition factors of 1.9 and 1.6, respectively. The absorbance of PHFHIPS films containing 10 wt% of the diester inhibitors is 3.6 AU/micron compared with an absorbance of 3.3 AU/micron for the polymer itself. The absorbance of 10% FPMD1 in PHFHIPS was measured as 3.5 AU/micron compared with an absorbance of 3.4 AU/micron for the polymer itself. Thus, the non-volatility and transparency of the fluorinated inhibitors at 157 nm as well as their ability to reduce the development rate of fluorinated polymers make them suitable for use in a 157 nm resist system.

  14. Dissolution of FB-Line Cabinet Sweepings

    SciTech Connect

    Crowder, Mark L.

    2005-06-14

    Three FB-Line samples were received by the Savannah River National Laboratory (SRNL) for characterization and evaluation for suitability for HB-Line dissolution. These samples are part of a larger sampling/evaluation program in support of FB-Line deinventory efforts. The samples studied were identified as MC04-147- HBL, MC04-148-HBL, and FBL-SWP-04-016-HBL (N). The first sample, MC04-147-HBL, is a portion of FB-Line Packaging and Stabilization (P&S) materials. The second sample, MC04-148-HBL, is a sweeping from Cabinet 6-8, which is not representative of the mechanical line. The third sample, FBL-SWP-04-016-HBL (N), is an FB-Line North cabinet sweeping. The samples were described by FB-Line personnel as containing plutonium oxide (PuO{sub 2}) which had not been high-fired. This description was generally confirmed by solids analysis and off gas measurements. All three samples were dissolved in 8 M HNO{sub 3}/0.1 M KF at 90-100 C leaving minor amounts of solid residue. During dissolution, sample MC04-147 did not generate hydrogen gas. Sample MC04-148 generated modest amounts of gas, which contained 4.0 to 4.7 volume percent (vol %) hydrogen (H{sub 2}) at a ratio of up to 8.4 x 10{sup -5} mol H{sub 2}/g sample. Sample FBL-SWP-04-016-HBL (N) was nearly completely soluble in 8 M HNO{sub 3}and produced a very small amount of gas. Apparently, the CaF{sub 2} in that sample dissolves and provides sufficient fluoride to support the dissolution of other components.

  15. Mesoscale Approach to Feldspar Dissolution: Quantification of Dissolution Incongruency Based on Al/Si Ordering State

    NASA Astrophysics Data System (ADS)

    Yang, Y.; Min, Y.; Jun, Y.

    2012-12-01

    Dissolution mechanism of aluminosilicates is important for understanding natural and anthropogenic carbon cycles. The total mass of atmospheric CO2 is regulated by the weathering of silicate minerals, and the fate of geologically sequestered CO2 is affected by the interactions between brine, sandstone, caprock, and CO2, which is initiated by mineral dissolution. It has been shown through both experimental and ab initio studies that the dissolution/weathering reactivities of Al and Si in the matrix of an aluminosilicate can be different under many conditions. A subsequent observation is that the release rates of Al and Si, both from the same mineral, may not be stoichiometric when compared to the bulk chemistry of the mineral. For a very long time, the relationship between mineral dissolution incongruency and mineral crystallographic properties remain largely qualitative and descriptive. Here we study the dissolution incongruency of feldspars, the most abundant aluminosilicate on earth. Mineral dissolution experiments for a series of alkali feldspars (albite, anorthoclase, sanidine, and microcline) and plagioclases (oligoclase, andesine, labradorite, bytownite, and anorthite) were conducted at pH 1.68 under ambient conditions. Synchrotron-based X-ray diffraction (HR-XRD), Fourier transform infrared spectroscopy (FTIR), and water chemistry analysis (ICP-MS) are combined to examine the effect of Al/Si ordering on mineral dissolution. Our analysis based on a C1 structure model shows that the incongruency, stemming from the different reactivities of Al-O-Si and Si-O-Si linkages in feldspar's framework, is quantifiable and closely related to the Al/Si ordering state of a feldspar. Our results also suggest that the more random the Al/Si distribution of a mineral, the greater the dissolution incongruency. Our results have significant implications for understanding water-rock interactions. First, when studying the effect of water chemistry on water-rock interaction, smaller

  16. VEGFR-2 conformational switch in response to ligand binding

    PubMed Central

    Sarabipour, Sarvenaz; Ballmer-Hofer, Kurt; Hristova, Kalina

    2016-01-01

    VEGFR-2 is the primary regulator of angiogenesis, the development of new blood vessels from pre-existing ones. VEGFR-2 has been hypothesized to be monomeric in the absence of bound ligand, and to undergo dimerization and activation only upon ligand binding. Using quantitative FRET and biochemical analysis, we show that VEGFR-2 forms dimers also in the absence of ligand when expressed at physiological levels, and that these dimers are phosphorylated. Ligand binding leads to a change in the TM domain conformation, resulting in increased kinase domain phosphorylation. Inter-receptor contacts within the extracellular and TM domains are critical for the establishment of the unliganded dimer structure, and for the transition to the ligand-bound active conformation. We further show that the pathogenic C482R VEGFR-2 mutant, linked to infantile hemangioma, promotes ligand-independent signaling by mimicking the structure of the ligand-bound wild-type VEGFR-2 dimer. DOI: http://dx.doi.org/10.7554/eLife.13876.001 PMID:27052508

  17. Low Temperature Aluminum Dissolution Of Sludge Waste

    SciTech Connect

    Keefer, M.T.; Hamm, B.A.; Pike, J.A.

    2008-07-01

    High Level Waste (HLW) at the Savannah River Site (SRS) is currently stored in aging underground storage tanks. This waste is a complex mixture of insoluble solids, referred to as sludge, and soluble salts. Continued long-term storage of these radioactive wastes poses an environmental risk. The sludge is currently being stabilized in the Defense Waste Processing Facility (DWPF) through a vitrification process immobilizing the waste in a borosilicate glass matrix for long-term storage in a federal repository. Without additional treatment, the existing volume of sludge would produce nearly 8000 canisters of vitrified waste. Aluminum compounds, along with other non-radioactive components, represent a significant portion of the sludge mass currently planned for vitrification processing in DWPF. Removing the aluminum from the waste stream reduces the volume of sludge requiring vitrification and improves production rates. Treating the sludge with a concentrated sodium hydroxide (caustic) solution at elevated temperatures (>90 deg. C) to remove aluminum is part of an overall sludge mass reduction effort to reduce the number of vitrified canisters, shorten the life cycle for the HLW system, and reduce the risk associated with the long term storage of radioactive wastes at SRS. A projected reduction of nearly 900 canisters will be achieved by performing aluminum dissolution on six targeted sludge batches; however, a project to develop and install equipment will not be ready for operation until 2013. The associated upgrades necessary to implement a high temperature process in existing facilities are costly and present many technical challenges. Efforts to better understand the characteristics of the sludge mass and dissolution kinetics are warranted to overcome these challenges. Opportunities to further reduce the amount of vitrified waste and increase production rates should also be pursued. Sludge staged in Tank 51 as the next sludge batch for feed to DWPF consisted

  18. Aryl hydrocarbon receptor ligands in cancer: friend and foe.

    PubMed

    Murray, Iain A; Patterson, Andrew D; Perdew, Gary H

    2014-12-01

    The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that is best known for mediating the toxicity and tumour-promoting properties of the carcinogen 2,3,7,8-tetrachlorodibenzo-p-dioxin, commonly referred to as ‘dioxin’. AHR influences the major stages of tumorigenesis — initiation, promotion, progression and metastasis — and physiologically relevant AHR ligands are often formed during disease states or during heightened innate and adaptive immune responses. Interestingly, ligand specificity and affinity vary between rodents and humans. Studies of aggressive tumours and tumour cell lines show increased levels of AHR and constitutive localization of this receptor in the nucleus. This suggests that the AHR is chronically activated in tumours, thus facilitating tumour progression. This Review discusses the role of AHR in tumorigenesis and the potential for therapeutic modulation of its activity in tumours. PMID:25568920

  19. Effects of Al/Si ordering on feldspar dissolution: Part II. The pH dependence of plagioclases' dissolution rates

    NASA Astrophysics Data System (ADS)

    Yang, Yi; Min, Yujia; Jun, Young-Shin

    2014-02-01

    The rate of mineral dissolution in an aquatic environment is sensitive to the pH of the contacting solution. The pH dependence of mineral dissolution rate has been interpreted by the Transition State Theory-Surface Complexation Model (TST-SCM) formalism in terms of pH-sensitive variability in surface chemistry. In this study, we provide an alternative interpretation for the experimentally observed nonlinear pH dependence of feldspar dissolution rates. The interpretation is based on a new formalism for feldspar dissolution which, while compatible with the TST-SCM formalism, incorporates the effects of both surface chemistry and bulk chemistry on feldspar dissolution into the quantification of dissolution rate. The pH dependence of dissolution rate varies from one feldspar specimen to another because different TOT linkages within one solid matrix can respond differently to the attack of proton. Our results suggest that the pH dependence of feldspar dissolution rate is not a constant in general, and could be affected by pH, substitutional Al/Si ordering, chemical composition of the specimen, and the relative rapidness of linkage hydrolysis according to different mechanisms. The rate law proposed in this study is able to capture the experimentally observed pH dependence of the dissolution rates of a series of plagioclases, including albite, andesine, labradorite, bytownite, and anorthite. The effectiveness of the newly proposed formalism for feldspar dissolution, hence, suggests that dissolution reactions of minerals are combinations of surface renewal and heterogeneous chemical reactions. The currently widely used TST-SCM-based rate laws can be further improved by taking into account the effects of bulk chemistry and surface renewal in the prediction of mineral dissolution rates. An improved formalism for mineral dissolution will be mineral-specific, and will reflect the effects of the temporal decay in the availability of reactive surface sites as well as the

  20. Coupled Mineral Dissolution and Precipitation Reactions in Shale-Hydraulic Fracturing Fluid Systems

    NASA Astrophysics Data System (ADS)

    Joe-Wong, C. M.; Harrison, A. L.; Thomas, D.; Dustin, M. K.; Jew, A. D.; Brown, G. E.; Maher, K.; Bargar, J.

    2015-12-01

    Hydraulic fracturing of low-permeability, hydrocarbon-rich shales has recently become an important energy source in the United States. However, hydrocarbon recovery rates are low and drop rapidly after a few months. Hydraulic fracture fluids, which contain dissolved oxygen and numerous organic additives, induce dissolution and precipitation reactions that change the porosity and permeability of the shale. To investigate these reactions, we studied the interactions of four shales (Eagle Ford, Barnett, Marcellus, and Green River) with a simulated hydraulic fracture fluid in batch reactors at 80 °C. The shales were chosen for both economic viability and chemical variety, allowing us to explore the reactivities of different components. The Eagle Ford shale is carbonate rich, and the Green River shale contains significant siderite and kerogen. The Barnett shale also has a high organic content, while the Marcellus shale has the highest fractions of clay and pyrite. Our experiments show that hydrochloric acid in the fluid promotes carbonate mineral dissolution, rapidly raising the pH from acidic to circumneutral levels for the Eagle Ford and Green River shales. Dissolution textures in the Green River shale and large cavities in the Barnett shale indicate significant mineralogical and physical changes in the reacted rock. Morphological changes are not readily apparent in the Eagle Ford and Marcellus shales. For all shales, ongoing changes to the solution Al: Si ratio suggest incongruent aluminosilicate dissolution. Siderite or pyrite dissolution occurs within days and is followed by the formation of secondary Fe precipitates in suspension and coating the walls of the reactor. However, little evidence of any coatings on shale surfaces was found. The net effect of these reactions on porosity and permeability and their influence on the long-term efficacy of oil and gas recovery after hydraulic fracturing are critical to the energy landscape of the United States.

  1. The role of carboxylic acids in albite and quartz dissolution: An experimental study under diagenetic conditions

    SciTech Connect

    Franklin, S.P. ); Hajash, A. Jr.; Tieh, T.T. ); Dewers, T.A. )

    1994-10-01

    Simple water soluble organic acids may promote secondary porosity development in sandstones during diagenesis by increasing feldspar solubility and dissolution rate. To test this hypothesis, Amelia albite and Brazilian hydrothermal quartz were reacted with 0.07 m acetate and 0.07 m acetate-0.005 m oxalate solutions at selected pH values, and distilled water. Pore fluid chemistry was monitored through time at various flow rates to obtain both solubility and dissolution rate data. The experiments were conducted in large volume, semi-static, flow-through systems at 100[degrees]C and 347 bars. These systems simulate subsurface flow rates, low mass water/rock, and high surface area/fluid mass. Acetate and acetate + oxalate solutions significantly increase albite solubility at temperatures, pressures, and pH values typical of diagenetic environments. Albite solubilities increased in acetate and acetate + oxalate solutions by factors of 2 and 3.4, respectively, compared to distilled water. In these same solutions, Al concentrations were [approx] 140 and [approx] 480 times higher than that calculated for kaolinite solubility at the same conditions without organic species. These enhanced solubilities occur at pH values (4.6-4.8) that may overlap with formation waters. In contrast to albite, quartz solubility was essentially identical in all solutions investigated. Dissolution rates in the acid region decreased with increasing pH in the acetate and acetate + oxalate solutions. Slopes of log rate vs. pH curves were [approx] 0.6 for acetate and [approx] 0.3 for acetate + oxalate. Although the effects of acetate on the dissolution rate are small, the effects of oxalate are significant. A rate law valid for albite dissolution at 100[degrees]C, oxalate concentrations to 0.01 m, and pH values ranging from 3.4 to 5.5 is given.

  2. From cellulose fibrils to single chains: understanding cellulose dissolution in ionic liquids.

    PubMed

    Yuan, Xueming; Cheng, Gang

    2015-12-21

    Cellulose is the most abundant and renewable organic compound on Earth, it is however not soluble in common organic solvents and aqueous solutions. Cellulose dissolution is a key aspect to promote its value-added applications. Ionic liquids (ILs) have been shown to solubilize cellulose under relatively mild conditions. The easy processability of cellulose with ILs and their environmental-friendly nature prompted research in various fields such as biomass pretreatment and conversion, cellulose fiber and composite production, and chemical conversion of cellulose in ILs. Progress has been made on understanding the mechanism of cellulose dissolution in ILs, including the structural characteristics of ILs that are cellulose solvents, however many details remain unknown. In light of rapid development and importance of cellulose dissolution in the field of IL-based cellulose and biomass processing, it is necessary to provide an overview of current understanding of cellulose dissolution in ILs and outline possible future research trends. Recent literature studies suggest that synergistic effects between the anions and the cations of ILs need to be revealed, which requires refining the structure of cellulose elementary fibrils, simulation of more realistic cellulose fibrils and detailed studies on the solution structure of cellulose in ILs. After analyzing literature studies, three interacting modules are identified, which are crucial to understand the process of cellulose dissolution in ILs: (1) the structure of elementary fibrils; (2) solvation of cellulose in ILs; and (3) solution structure of cellulose solubilized in ILs. A coherent analysis of these modules will aid in better design of more efficient ILs and processes. PMID:26562500

  3. Dissolution of Uranium Oxides Under Alkaline Oxidizing Conditions

    SciTech Connect

    Smith, Steven C.; Peper, Shane M.; Douglas, Matthew; Ziegelgruber, Kate L.; Finn, Erin C.

    2009-11-01

    Bench scale experiments were conducted to determine the dissolution characteristics of uranium oxide powders (UO2, U3O8, and UO3) in aqueous peroxide-carbonate solutions. Experimental parameters included H2O2 concentration, carbonate counter cation (NH4+, Na+, K+, and Rb+), and pH. Results indicate the dissolution rate of UO2 in 1 M (NH4)2CO3 increases linearly with peroxide concentration ranging from 0.05 – 2 M. The three uranium oxide powders exhibited different dissolution patterns however, UO3 exhibited prompt complete dissolution. Carbonate counter cation affected the dissolution kinetics. There is minimal impact of solution pH, over the range 8.8 to 10.6, on initial dissolution rate.

  4. Dissolution of Platinum in the Operational Range of Fuel Cells

    PubMed Central

    Keeley, Gareth P.; Geiger, Simon; Zeradjanin, Aleksandar R.; Hodnik, Nejc; Kulyk, Nadiia

    2015-01-01

    Abstract One of the most important practical issues in low‐temperature fuel‐cell catalyst degradation is platinum dissolution. According to the literature, it initiates at 0.6–0.9 VRHE, whereas previous time‐ and potential‐resolved inductively coupled plasma mass spectrometry (ICP–MS) experiments, however, revealed dissolution onset at only 1.05 VRHE. In this manuscript, the apparent discrepancy is addressed by investigating bulk and nanoparticulated catalysts. It is shown that, given enough time for accumulation, traces of platinum can be detected at potentials as low as 0.85 VRHE. At these low potentials, anodic dissolution is the dominant process, whereas, at more positive potentials, more platinum dissolves during the oxide reduction after accumulation. Interestingly, the potential and time dissolution dependence is similar for both types of electrode. Dissolution processes are discussed with relevance to fuel‐cell operation and plausible dissolution mechanisms are considered. PMID:27525206

  5. Use of partial dissolution techniques in geochemical exploration

    USGS Publications Warehouse

    Chao, T.T.

    1984-01-01

    Application of partial dissolution techniques to geochemical exploration has advanced from an early empirical approach to an approach based on sound geochemical principles. This advance assures a prominent future position for the use of these techniques in geochemical exploration for concealed mineral deposits. Partial dissolution techniques are classified as single dissolution or sequential multiple dissolution depending on the number of steps taken in the procedure, or as "nonselective" extraction and as "selective" extraction in terms of the relative specificity of the extraction. The choice of dissolution techniques for use in geochemical exploration is dictated by the geology of the area, the type and degree of weathering, and the expected chemical forms of the ore and of the pathfinding elements. Case histories have illustrated many instances where partial dissolution techniques exhibit advantages over conventional methods of chemical analysis used in geochemical exploration. ?? 1984.

  6. Dissolution kinetics of calcium phosphate coatings.

    PubMed

    Burke, E M; Lucas, L C

    1998-01-01

    Plasma spray and high velocity oxy-fuel (HVOF) techniques produce coatings with varying composition and amounts of amorphous and crystalline phases. For coatings containing greater amorphous phases, a higher release of calcium ions is evident when samples are placed in Hank's calcium-free balanced salt solutions. Calcium is released from the amorphous phases in the coating, a conclusion that is supported by x-ray powder diffraction (XRD) results. Ion beam sputtering and RF magnetron sputtering under lower energy conditions produce amorphous coatings that will dissolve in a very short time period. When heat treated, crystalline phases are produced in the coatings. Heat-treated coatings are significantly more stable than the amorphous coatings. The dissolution rates of both amorphous and crystalline coatings produced by RF magnetron sputtering have been measured under constant solution conditions at pH 6.50. No reprecipitation is possible under these conditions. The amorphous coating dissolved at a significantly higher rate than the heat-treated coating. Reprecipitation of calcium phosphate onto amorphous coatings is possible in a physiological pH solution. Under these conditions, the dissolution rate of the amorphous coating is four times slower than at the pH 6.50 conditions. PMID:10196809

  7. On the dissolution properties of GaAs in Ga

    NASA Technical Reports Server (NTRS)

    Davidson, M. C.; Moynahan, A. H.

    1977-01-01

    The dissolution of GaAs in Ga was studied to determine the nature and cause of faceting effects. Ga was allowed to dissolve single crystalline faces under isothermal conditions. Of the crystalline planes with low number indices, only the (100) surface showed a direct correlation of dissolution sites to dislocations. The type of dissolution experienced depended on temperature, and there were three distinct types of behavior.

  8. Dissolution of biogenic ooze over basement edifices in the equatorial Pacific with implications for hydrothermal ventilation of the oceanic crust

    USGS Publications Warehouse

    Bekins, B.A.; Spivack, A.J.; Davis, E.E.; Mayer, L.A.

    2007-01-01

    Recent observations indicate that curious closed depressions in carbonate sediments overlying basement edifices are widespread in the equatorial Pacific. A possible mechanism for their creation is dissolution by fluids exiting basement vents from off-axis hydrothermal flow. Quantitative analysis based on the retrograde solubility of calcium carbonate and cooling of basement fluids during ascent provides an estimate for the dissolution capacity of the venting fluids. Comparison of the dissolution capacity and fluid flux with typical equatorial Pacific carbonate mass accumulation rates shows that this mechanism is feasible. By maintaining sediment-free basement outcrops, the process may promote widespread circulation of relatively unaltered seawater in the basement in an area where average sediment thicknesses are 300-500 m. The enhanced ventilation can explain several previously puzzling observations in this region, including anomalously low heat flux, relatively unaltered seawater in the basement, and aerobic and nitrate-reducing microbial activity at the base of the sediments. ?? 2007 The Geological Society of America.

  9. Dissolution Studies With Pilot Plant and Actual INTEC Calcines

    SciTech Connect

    Herbst, Ronald Scott; Garn, Troy Gerry

    1999-04-01

    The dissolution of Idaho Nuclear Technology and Engineering Center (INTEC) pilot plant calcines was examined to determine solubility of calcine matrix components in acidic media. Two representatives pilot plant calcine types were studied: Zirconia calcine and Zirconia/ Sodium calcine. Dissolution of these calcines was evaluated using lower initial concentrations of nitric acid than used in previous tests to decrease the [H+] concentration in the final solutions. Lower [H+] concentrations contribute to more favorable TRUEX/SREX solvent extraction flowsheet performance. Dissolution and analytical results were also obtained for radioactive calcines produced using high sodium feeds blended with non-radioactive A1(NO3)3 solutions to dilute the sodium concentration and prevent bed agglomeration during the calcination process. Dissolution tests indicated >95 wt. % of the initial calcine mass can be dissolved using the baseline dissolution procedure, with the exception that higher initial nitric acid concentrations are required. The higher initial acid concentration is required for stoichiometric dissolution of the oxides, primarily aluminum oxide. Statistically designed experiments using pilot plant calcine were performed to determine the effect of mixing rate on dissolution efficiency. Mixing rate was determined to provide minimal effects on wt. % dissolution. The acid/calcine ratio and temperature were the predominate variables affecting the wt. % dissolution, a result consistent with previous studies using other similar types of pilot plant calcines.

  10. Dissolution studies with pilot plant and actual INTEC calcines

    SciTech Connect

    Herbst, R.S.; Garn, T.G.

    1999-04-01

    The dissolution of Idaho Nuclear Technology and Engineering Center (INTEC) pilot plant calcines was examined to determine solubility of calcine matrix components in acidic media. Two representatives pilot plant calcine types were studied: Zirconia calcine and Zirconia/Sodium calcine. Dissolution of these calcines was evaluated using lower initial concentrations of nitric acid than used in previous tests to decrease the [H+] concentration in the final solutions. Lower [H+] concentrations contribute to more favorable TRUEX/SREX solvent extraction flowsheet performance. Dissolution and analytical results were also obtained for radioactive calcines produced using high sodium feeds blended with non-radioactive Al(NO{sub 3}){sub 3} solutions to dilute the sodium concentration and prevent bed agglomeration during the calcination process. Dissolution tests indicated {gt}95 wt.% of the initial calcine mass can be dissolved using the baseline dissolution procedure, with the exception that higher initial nitric acid concentrations are required. The higher initial acid concentration is required for stoichiometric dissolution of the oxides, primarily aluminum oxide. Statistically designed experiments using pilot plant calcine were performed to determine the effect of mixing rate on dissolution efficiency. Mixing rate was determined to provide minimal effects on wt.% dissolution. The acid/calcine ratio and temperature were the predominate variables affecting the wt.% dissolution, a result consistent with previous studies using other similar types of pilot plant calcines.

  11. Dissolution of beryllium in artificial lung alveolar macrophage phagolysosomal fluid.

    PubMed

    Stefaniak, Aleksandr B; Virji, M Abbas; Day, Gregory A

    2011-05-01

    Dissolution of a lung burden of poorly soluble beryllium particles is hypothesized to be necessary for development of chronic beryllium lung disease (CBD) in humans. As such, particle dissolution rate must be sufficient to activate the lung immune response and dissolution lifetime sufficient to maintain chronic inflammation for months to years to support development of disease. The purpose of this research was to investigate the hypothesis that poorly soluble beryllium compounds release ions via dissolution in lung fluid. Dissolution kinetics of 17 poorly soluble particulate beryllium materials that span extraction through ceramics machining (ores, hydroxide, metal, copper-beryllium [CuBe] fume, oxides) and three CuBe alloy reference materials (chips, solid block) were measured over 31 d using artificial lung alveolar macrophage phagolysosomal fluid (pH 4.5). Differences in beryllium-containing particle physicochemical properties translated into differences in dissolution rates and lifetimes in artificial phagolysosomal fluid. Among all materials, dissolution rate constant values ranged from 10(-5) to 10(-10)gcm(-2)d(-1) and half-times ranged from tens to thousands of days. The presence of magnesium trisilicate in some beryllium oxide materials may have slowed dissolution rates. Materials associated with elevated prevalence of CBD had faster beryllium dissolution rates [10(-7)-10(-8)gcm(-2)d(-1)] than materials not associated with elevated prevalence (p<0.05). PMID:21251696

  12. The dissolution behavior of scorodite in acidic environments

    NASA Astrophysics Data System (ADS)

    Pande, Preeti

    2001-11-01

    The safe disposal of arsenic-containing waste has been a difficult problem for the mining and metallurgical industry. One of the solutions to the arsenic problem is the precipitation of scorodite, an arsenic-containing mineral. Scorodite is reported to be relatively stable over a wide range of pH, and therefore may be a preferred disposal option. The effect of organic complexing agents on scorodite stability, however, is largely unknown. The present study is a phenomenological investigation into the dissolution kinetics of scorodite in the presence of oxalic acid under varying conditions of pH, oxalic acid concentration and temperature. The effect of scorodite particle size was also investigated. The morphological changes accompanying the dissolution process were examined by SEM and TEM analyses. Dissolution curves were divided into a linear induction period and a post-induction period. Activation energies were determined. Complete dissolution data were fit to the Prout-Tompkins/Austin-Rickett model. Dissolution data are indicative of auto-accelerated processes. The rapid increase in dissolution rate following the induction period is believed to be associated with an increase in the effective surface area. Pitting was observed on the surface of scorodite in the early stages of dissolution. In the later stages of dissolution, these pits were observed to grow and coalesce, in many cases resulting in the formation of dissolution holes.

  13. Molecular dynamics simulation of NaCl dissolution.

    PubMed

    Lanaro, Gabriele; Patey, G N

    2015-03-19

    Molecular dynamics simulations are used to investigate the dissolution of NaCl nanocrystals (containing ∼2400 ions) in water. We focus on systems under sink conditions at 300 K, but the influences of concentration and temperature are also investigated. Cubical, spherical, tablet-shaped, and rod-shaped nanocrystals are considered, and it is shown that the initial shape can influence the dissolution process. Dissolution is observed to occur in three stages: an initial period where the most exposed ions are removed from the crystal surface, and the crystal takes on a solution-annealed shape which persists throughout the second stage of dissolution; a second long intermediate stage where dissolution roughly follows a fixed rate law; and a final stage where the small residual crystal (≲200 ions) dissolves at an ever increasing rate until it disappears. The second stage of dissolution which applies for most of the dissolution process is well described by classical rate equations which simply assume that the dissolution rate is proportional to an active surface area from which ions are most easily detached from the crystal. The active area depends on the initial crystal shape. We show that for our model NaCl nanocrystals the rate-determining step for dissolution under sink conditions is ion detachment from the crystal, and that diffusion layers do not exist for these systems. PMID:25704286

  14. Effect of thermal gelation on dissolution from coated tablets.

    PubMed

    Schwartz, J B; Alvino, T P

    1976-04-01

    Tablets with a methylcellulose coating were found to exhibit lower dissolution profiles than those coated with a hydroxypropyl methylcellulose coating at 37 degrees, and the cause was investigated. The differences are attributed to thermal gelation of the methylcellulose at temperatures near 37 degrees, which creates a barrier to the dissolution process and essentially changes the dissolution mechanism. This mechanism is substantiated by the fact that at temperatures below the gel point and at increased agitation, the effect disappears. The retarded dissolution effect is not peculiar to the drug involved. PMID:1271258

  15. Mathematical modeling of variables involved in dissolution testing.

    PubMed

    Gao, Zongming

    2011-11-01

    Dissolution testing is an important technique used for development and quality control of solid oral dosage forms of pharmaceutical products. However, the variability associated with this technique, especially with USP apparatuses 1 and 2, is a concern for both the US Food and Drug Administration and pharmaceutical companies. Dissolution testing involves a number of variables, which can be divided into four main categories: (1) analyst, (2) dissolution apparatus, (3) testing environment, and (4) sample. Both linear and nonlinear models have been used to study dissolution profiles, and various mathematical functions have been used to model the observed data. In this study, several variables, including dissolved gases in the dissolution medium, off-center placement of the test tablet, environmental vibration, and various agitation speeds, were modeled. Mathematical models including Higuchi, Korsmeyer-Peppas, Weibull, and the Noyes-Whitney equation were employed to study the dissolution profile of 10 mg prednisone tablets (NCDA #2) using the USP paddle method. The results showed that the nonlinear models (Korsmeyer-Peppas and Weibull) accurately described the entire dissolution profile. The results also showed that dissolution variables affected dissolution rate constants differently, depending on whether the tablets disintegrated or dissolved. PMID:21702052

  16. K Basin sludge dissolution engineering study

    SciTech Connect

    Westra, A.G.

    1998-08-28

    The purpose of this engineering study is to investigate the available technology related to dissolution of the K Basin sludge in nitric acid. The conclusion of this study along with laboratory and hot cell tests with actual sludge samples will provide the basis for beginning conceptual design of the sludge dissolver. The K Basin sludge contains uranium oxides, fragments of metallic U, and some U hydride as well as ferric oxyhydroxide, aluminum oxides and hydroxides, windblown sand that infiltrated the basin enclosure, ion exchange resin, and miscellaneous materials. The decision has been made to dispose of this sludge separate from the fuel elements stored in the basins. The sludge will be conditioned so that it meets Tank Waste Remediation System waste acceptance criteria and can be sent to one of the underground storage tanks. Sludge conditioning will be done by dissolving the fuel constituents in nitric acid, separating the insoluble material, adding neutron absorbers for criticality safety, and then reacting the solution with caustic to co-precipitate the uranium and plutonium. There will be five distinct feed streams to the sludge conditioning process two from the K East (KE) Basin and three from the K West (KW) Basin. The composition of the floor and pit sludges which contain more iron oxides and sand than uranium is much different than the canister sludges which are composed of mostly uranium oxides. The sludge conditioning equipment will be designed to process all of the sludge streams, but some of the operating parameters will be adjusted as necessary to handle the different sludge stream compositions. The volume of chemical additions and the amount of undissolved solids will be much different for floor and pit sludge than for canister sludge. Dissolution of uranium metal and uranium dioxide has been studied quite thoroughly and much information is available. Both uranium metal and uranium dioxide have been dissolved on a large scale in nuclear fuel

  17. Dolomite Dissolution in Alkaline Cementious Media

    NASA Astrophysics Data System (ADS)

    Mittermayr, Florian; Klammer, Dietmar; Köhler, Stephan; Dietzel, Martin

    2010-05-01

    Chemical alteration of concrete has gained much attention over the past years as many cases of deterioration due to sulphate attack, thaumasite formation (TSA) or alkali silica reactions (ASR) have been reported in various constructions (Schmidt et al, 2009). Much less is known about the so called alkali carbonate reaction (ACR). It is believed that dolomite aggregates can react with the alkalis from the cement, dissolve and form calcite and brucite (Katayama, 2004). Due to very low solubility of dolomite in alkaline solutions this reaction seems doubtful. In this study we are trying to gain new insides about the conditions that can lead to the dissolution of dolomite in concrete. Therefore we investigated concrete samples from Austrian tunnels that show partially dissolved dolomite aggregates. Petrological analysis such as microprobe, SEM and Raman spectroscopy as well as a hydrochemical analysis of interstitial solutions and ground water and modelling with PhreeqC (Parkhurst and Appelo, 1999) are carried out. In addition a series of batch experiments is set up. Modelling approaches by PhreeqC show a thermodynamically possibility in the alkaline range when additional Ca2+ in solution causes dolomite to become more and more undersaturated as calcite gets supersaturated. Interacting ground water is enriched in Ca2+and saturated with respect to gypsum as marine evaporites are found in situ rocks. Furthermore it is more likely that Portlandite (Ca(OH)2) plays a more important role than Na and K in the cement. Portlandite acts as an additional Ca2+ source and is much more abundant than the alkalies. Some interstitial solutions are dominated mainly by Na+ and SO42- and reach concentrations up to 30 g/l TDS. It is believed that solutions can even reach thenardite saturation as efflorescences are found on the tunnel walls. In consequence dolomite solubility increases with increasing ionic strength. pH > 11 further accelerate the process of dedolomitization by the removal

  18. Dissolution and compaction instabilities in geomaterials

    NASA Astrophysics Data System (ADS)

    Stefanou, I.; Sulem, J.; de Sauvage, J.

    2014-12-01

    Compaction bands play an important role in reservoir engineering and geological storage. Their presence in geological formations may also provide useful information on various geological processes. Several mechanisms can be involved at different scales and may be responsible for compaction band instabilities [1]. Compaction bands can be seen as a particular instability of the governing mathematical system leading to localization of deformation [2-4]. In a saturated porous rock, the progressive mechanical damage of the solid skeleton during compaction, results in the increase of the interface area of the reactants and consequently in the acceleration of the dissolution rate of the solid phase [2,5]. Thus, the solid skeleton is degraded more rapidly (mass removal because of dissolution), the overall mechanical properties of the system diminish (contraction of the elastic domain - chemical softening), deformations increase and the solid skeleton is further damaged (intergranular fractures, debonding, breakage of the porous network etc.). The stability of this positive feedback process is investigated analytically through linear stability analysis by considering the strong chemo-poro-mechanical coupling due to chemical dissolution. The post bifurcation behavior is then studied analytically and numerically revealing the compaction band thickness and periodicity. The effect of various parameters is studied as for instance the influence of the hydraulic diffusivity on the compaction band thickness. [1] P. Baud, S. Vinciguerra, C. David, A. Cavallo, E. Walker and T. Reuschlé (2009), Pure Appl. Geophys., 166(5-7), 869-898 [2] I. Stefanou and J. Sulem (2014), JGR: Solid Earth, 119(2), 880-899. doi:10.1002/2013JB010342I [3] J.W. Rudnicki and J.R. Rice (1975), Journal of the Mechanics and Physics of Solids 23(6),: 371-394 [4] K.A. Issen and J.W. Rudnicki (2000), JGR, 105(B9), 21529. doi:10.1029/2000JB900185 [5] R. Nova, R. Castellanza and C. Tamagnini (2003), International

  19. Effect of pulmonary surfactant on the dissolution, stability and uptake of zinc oxide nanowires by human respiratory epithelial cells.

    PubMed

    Theodorou, Ioannis G; Ruenraroengsak, Pakatip; Gow, Andrew; Schwander, Stephan; Zhang, Junfeng Jim; Chung, Kian Fan; Tetley, Teresa D; Ryan, Mary P; Porter, Alexandra E

    2016-11-01

    Inhaled nanoparticles (NPs) have high-deposition rates in the alveolar region of the lung but the effects of pulmonary surfactant (PS) on nanoparticle bioreactivity are unclear. Here, the impact of PS on the stability and dissolution of ZnO nanowires (ZnONWs) was investigated, and linked with their bioreactivity in vitro with human alveolar epithelial type 1-like cells (TT1). Pre-incubation of ZnONWs with Curosurf® (a natural porcine PS) decreased their dissolution at acidic pH, through the formation of a phospholipid corona. Confocal live cell microscopy confirmed that Curosurf® lowered intracellular dissolution, thus delaying the onset of cell death compared to bare ZnONWs. Despite reducing dissolution, Curosurf® significantly increased the uptake of ZnONWs within TT1 cells, ultimately increasing their toxicity after 24 h. Although serum improved ZnONW dispersion in suspension similar to Curosurf®, it had no effect on ZnONW internalization and toxicity, indicating a unique role of PS in promoting particle uptake. In the absence of PS, ZnONW length had no effect on dissolution kinetics or degree of cellular toxicity, indicating a less important role of length in determining ZnONW bioreactivity. This work provides unique findings on the effects of PS on the stability and toxicity of ZnONWs, which could be important in the study of pulmonary toxicity and epithelial-endothelial translocation of nanoparticles in general. PMID:27441789

  20. Noble gas and carbon isotopic evidence for CO2-driven silicate dissolution in a recent natural CO2 field

    NASA Astrophysics Data System (ADS)

    Dubacq, Benoît; Bickle, Mike J.; Wigley, Max; Kampman, Niko; Ballentine, Chris J.; Sherwood Lollar, Barbara

    2012-08-01

    Secure storage of anthropogenic carbon dioxide (CO2) in geological reservoirs requires predicting gas-water-rock interactions over millennial timescales. Noble gases and carbon isotope measurements can be used to shed light on the nature of competing dissolution-precipitation processes over different timescales, from the fast dissolution of gaseous CO2 in groundwater to more sluggish reactions involving dissolution and precipitation of newly formed minerals in the reservoir. Here we study a compilation of gas analyses including noble gases and δ13C of CO2 from nine different natural CO2 reservoirs. Amongst these reservoirs, the Bravo Dome CO2 field (New Mexico, USA) shows distinct geochemical trends which are explained by degassing of noble gases from groundwater altering the composition of the gas phase. This groundwater degassing is synchronous with the dissolution of CO2 in groundwater. Progressive creation of alkalinity via CO2-promoted mineral dissolution is required to explain the observed positive correlation between CO2/3He and δ13C of the gas phase, a unique feature of Bravo Dome. The differences between Bravo Dome and other natural CO2 reservoirs are likely explained by the more recent filling of Bravo Dome, reflecting CO2-water-rock interactions over thousands of years rather than over millions of years in older reservoirs.

  1. The Study of the Successive Metal-ligand Binding Energies for Fe(+), Fe(-), V(+) and Co(+)

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Ricca, Alessandra; Maitre, Philippe; Langhoff, Stephen R. (Technical Monitor)

    1994-01-01

    The successive binding energies of CO and H2O to Fe(+), CO to Fe(-), and H2 to Co(+) and V(+) are presented. Overall the computed results are in good agreement with experiment. The trends in binding energies are analyzed in terms of metal to ligand donation, ligand to metal donation, ligand-ligand repulsion, and changes in the metal atom, such as hybridization, promotion, and spin multiplicity. The geometry and vibrational frequencies are also shown to be directly affected by these effects.

  2. The Study Of The Successive Metal-Ligand Binding Energies For Fe+, Fe-, V+ and Co+

    NASA Technical Reports Server (NTRS)

    Bauschicher, Charles W., Jr.; Ricca, Alessandra; Maitre, Philippe; Langhoff, Stephen R. (Technical Monitor)

    1995-01-01

    The successive binding energies of CO and H2O to Fe(+), CO to Fe(-), and H2 to Co(+) and V(+) are presented. Overall the computed results are in good agreement with experiment. The trends in binding energies are analyzed in terms of metal to ligand donation, ligand to metal donation, ligand-ligand repulsion, and changes in the metal atom, such as hybridization, promotion, and spin multiplicity. The geometry and vibrational frequencies are also shown to be directly affected by these effects.

  3. Parameterization of phosphine ligands reveals mechanistic pathways and predicts reaction outcomes

    NASA Astrophysics Data System (ADS)

    Niemeyer, Zachary L.; Milo, Anat; Hickey, David P.; Sigman, Matthew S.

    2016-06-01

    The mechanistic foundation behind the identity of a phosphine ligand that best promotes a desired reaction outcome is often non-intuitive, and thus has been addressed in numerous experimental and theoretical studies. In this work, multivariate correlations of reaction outcomes using 38 different phosphine ligands were combined with classic potentiometric analyses to study a Suzuki reaction, for which the site selectivity of oxidative addition is highly dependent on the nature of the phosphine. These studies shed light on the generality of hypotheses regarding the structural influence of different classes of phosphine ligands on the reaction mechanism(s), and deliver a methodology that should prove useful in future studies of phosphine ligands.

  4. Helium enrichment during convective carbon dioxide dissolution

    NASA Astrophysics Data System (ADS)

    Larson, T.; Hesse, M. A.

    2013-12-01

    Motivated by observed variations of the CO2/He ratios in natural carbon dioxide (CO2) reservoirs, such as the Bravo Dome field in northeastern New Mexico, we have performed laboratory experiments equilibrating gas mixtures containing Helium (He) and CO2 with water, at close to ambient conditions in a closed system. The experimental design allows for continuous measurement of headspace pressure as well as timed interval measurements of the CO2/He ratios and the δ13C value of CO2 in the headspace. Results from three dissolution experiments are reported: 1) pure Helium system, 2) 98% CO2 + 2% Nitrogen system, and 3) 97% CO2 and 3% Helium. Final equilibrated experimental results are compared to theoretical results obtained using Henry's Law relationships. The evolution of the amount of dissolved CO2 computed from gas pressure and gas compositions are in good agreement with Henry's Law relationships. For example, the CO2 + N2 system was initially pressurized with pure CO2 to 1323 mbar and after six days it equilibrated to a measured headspace pressure of 596 mbar. This compares very well with a calculated equilibrium headspace pressure of 592 mbar for this system. The CO2 + He system was pressurized to 1398 mbar CO2 and after six days equilibrated to a measured headspace pressure of 397 mbar. This measured pressure is slightly higher than the predicted equilibrated headspace pressure of 341 mbar, indicating a possible leak in the system during this particular experiment. In both experiments the initial pH of the water was 9.3 and the final equilibrated pH was 5.4. The δ13C value of equilibrated headspace CO2 was within 0.25‰ of its starting δ13C value, demonstrating insignificant carbon isotope fractionation at low pH. Measured Helium/ CO2 ratios throughout the CO2+Helium experiment preserve a non-linear trend of increasing He/ CO2 ratios through time that correlate very well with the measured pressure drop from CO2 dissolution. This indicates that gas composition

  5. New mixing system in dissolution isoperibol microcalorimeter.

    PubMed

    Moreno-Piraján, Juan Carlos; Giraldo-Gutierréz, Liliana

    2007-04-01

    In order to determine dissolution enthalpies of small amounts of easily or slightly soluble solids, a new cell for batch isoperibolic microcalorimetry was developed at the Universities of the Andes and the National of Colombia. An innovative mixing system for avoiding error due to the common effect of the brittle point breakage has been designed for this cell. The cell has a capacity of 40 ml and the sample holder can bear solid samples between 10.0 and 30.0 mg. The high stability of the base line allows solution experiments to be extended over several hours. All measurements reported were conducted at 298.15 K using water as solvent. PMID:17477696

  6. Uranium Metal Analysis via Selective Dissolution

    SciTech Connect

    Delegard, Calvin H.; Sinkov, Sergey I.; Schmidt, Andrew J.; Chenault, Jeffrey W.

    2008-09-10

    Uranium metal, which is present in sludge held in the Hanford Site K West Basin, can create hazardous hydrogen atmospheres during sludge handling, immobilization, or subsequent transport and storage operations by its oxidation/corrosion in water. A thorough knowledge of the uranium metal concentration in sludge therefore is essential to successful sludge management and waste process design. The goal of this work was to establish a rapid routine analytical method to determine uranium metal concentrations as low as 0.03 wt% in sludge even in the presence of up to 1000-fold higher total uranium concentrations (i.e., up to 30 wt% and more uranium) for samples to be taken during the upcoming sludge characterization campaign and in future analyses for sludge handling and processing. This report describes the experiments and results obtained in developing the selective dissolution technique to determine uranium metal concentration in K Basin sludge.

  7. Dehydration, dissolution, and melting of cyclodextrin crystals.

    PubMed

    Specogna, Erika; Li, King Wo; Djabourov, Madeleine; Carn, Florent; Bouchemal, Kawthar

    2015-01-29

    Cyclodextrins are a family of oligosaccharides with a toroid shape that exhibit a unique ability of entrapping guest molecules in their internal cavity. Water is the primary guest molecule and is omnipresent in the crystalline phases stabilizing the overall architecture. Despite the presence of water molecules inside the cavity, cyclodextrins provide a hydrophobic environment where poorly soluble molecules can easily fit. In this investigation we put in evidence different types of water in the hydrated α-, β-, and γ-cyclodextrin crystals. Thermogravimetric measurements identify various binding sites of water and highlight the difference between the crystals equilibrated under various humid atmospheres. We establish by microcalorimetry the limit of solubility versus temperature and measure for the first time the melting temperatures of the hydrated crystals. Dissolution and melting enthalpies are derived and the solubility curves are compared to existing literature. The specific features of each cyclodextrin are underlined. PMID:25565266

  8. Homopolymer Dissolution in a Hydrophilic Ionic Liquid

    NASA Astrophysics Data System (ADS)

    Hoagland, David; Harner, John

    2010-03-01

    Dissolution, structure, and dynamics of both neutral and charged polymers dissolved in a hydrophilic room temperature ionic liquid (IL), ethylmethylimidazolium ethyl sulfate [EMIM][EtSO4], have been studied by classical physicochemical methods (static and dynamic light scattering, intrinsic viscosity, refractometry) to determine differences in solution behavior from conventional aqueous and organic solvents. This IL is water miscible. Many neutral polymers and charged polymer salts molecularly dissolve, although solubility doesn't correlate with polymer hydrophilicity. Model neutral soluble polymers are polyvinylpyrrolidone and hydroroxyethyl cellulose while sodium poly(styrene sulfonate) and the iodo salt of methyl-quaternized poly(vinyl pyridine) fill the same role for charged polymers. The latter display none of the polyelectrolyte effects found in low ionic strength water, consistent with strong electrostatic screening in IL. In virial coefficient and coil size, the IL acts for these neutral and charged polymers as a classical good solvent. (Support: UMass MRSEC)

  9. Glass dissolution rate measurement and calculation revisited

    NASA Astrophysics Data System (ADS)

    Fournier, Maxime; Ull, Aurélien; Nicoleau, Elodie; Inagaki, Yaohiro; Odorico, Michaël; Frugier, Pierre; Gin, Stéphane

    2016-08-01

    Aqueous dissolution rate measurements of nuclear glasses are a key step in the long-term behavior study of such waste forms. These rates are routinely normalized to the glass surface area in contact with solution, and experiments are very often carried out using crushed materials. Various methods have been implemented to determine the surface area of such glass powders, leading to differing values, with the notion of the reactive surface area of crushed glass remaining vague. In this study, around forty initial dissolution rate measurements were conducted following static and flow rate (SPFT, MCFT) measurement protocols at 90 °C, pH 10. The international reference glass (ISG), in the forms of powders with different particle sizes and polished monoliths, and soda-lime glass beads were examined. Although crushed glass grains clearly cannot be assimilated with spheres, it is when using the samples geometric surface (Sgeo) that the rates measured on powders are closest to those found for monoliths. Overestimation of the reactive surface when using the BET model (SBET) may be due to small physical features at the atomic scale-contributing to BET surface area but not to AFM surface area. Such features are very small compared with the thickness of water ingress in glass (a few hundred nanometers) and should not be considered in rate calculations. With a SBET/Sgeo ratio of 2.5 ± 0.2 for ISG powders, it is shown here that rates measured on powders and normalized to Sgeo should be divided by 1.3 and rates normalized to SBET should be multiplied by 1.9 in order to be compared with rates measured on a monolith. The use of glass beads indicates that the geometric surface gives a good estimation of glass reactive surface if sample geometry can be precisely described. Although data clearly shows the repeatability of measurements, results must be given with a high uncertainty of approximately ±25%.

  10. Wollastonite: Incongruent dissolution and leached layer formation

    NASA Astrophysics Data System (ADS)

    Weissbart, Erich J.; Rimstidt, J. Donald

    2000-12-01

    Measurements of the dissolution rates of wollastonite in solutions with pH ranging from 2 to 6 in an externally recycled mixed flow reactor show that the concentrations of Ca and Si in the reactor effluent decline with time following a power law behavior. After 24 h of reaction, the release rate of Si was 1.90 × 10 -9 mol/m 2 s and the release rate of Ca was 9.09 × 10 -9 mol/m 2 s and these rates were effectively independent of pH. The more rapid release of Ca relative to Si produced a leached layer with an average thickness, x, that is a function of both hydrogen ion activity and time: x = (1.19 × 10 -9)( aH+) 0.121t0.412. The rate of Si release from the hydrated silica leached layer was thousands of times faster than the dissolution rate of vitreous silica. We believe that this is best explained by the release of large silica polymers from the leached layer. The rate of silica release declined as a power law function of time. This behavior is consistent with the idea that the silica in the leached layer undergoes reconstruction reactions that produce regions that are more polymerized and therefore dissolve at a slower rate. In addition, we found that the specific surface of the reacted grains increases as the leached layer grows. This additional surface area appears to come from crazing of the surface and the development of internal porosity. These results are not consistent with the idea that the dissolving mineral will eventually display a steady state behavior.

  11. Galanin Receptors and Ligands

    PubMed Central

    Webling, Kristin E. B.; Runesson, Johan; Bartfai, Tamas; Langel, Ülo

    2012-01-01

    The neuropeptide galanin was first discovered 30 years ago. Today, the galanin family consists of galanin, galanin-like peptide (GALP), galanin-message associated peptide (GMAP), and alarin and this family has been shown to be involved in a wide variety of biological and pathological functions. The effect is mediated through three GPCR subtypes, GalR1-3. The limited number of specific ligands to the galanin receptor subtypes has hindered the understanding of the individual effects of each receptor subtype. This review aims to summarize the current data of the importance of the galanin receptor subtypes and receptor subtype specific agonists and antagonists and their involvement in different biological and pathological functions. PMID:23233848

  12. Bifunctional DTPA-type ligand

    SciTech Connect

    Gansow, O.A.; Brechbiel, M.W.

    1990-03-26

    The subject matter of the invention relates to bifunctional cyclohexyl DTPA ligands and methods of using these compounds. Specifically, such ligands are useful for radiolabeling proteins with radioactive metals, and can consequently be utilized with respect to radioimmunoimaging and/or radioimmunotherapy.

  13. Al(+)-ligand binding energies

    NASA Technical Reports Server (NTRS)

    Sodupe, M.; Bauschlicher, Charles W., Jr.

    1991-01-01

    Ab initio calculations are used to optimize the structure and determine the binding energies of Al(+) to a series of ligands. For Al(+)-CN, the bonding was found to have a large covalent component. For the remaining ligands, the bonding is shown to be electrostatic in origin. The results obtained for Al(+) are compared with those previously reported for Mg(+).

  14. Uranium carbide dissolution in nitric solution: Sonication vs. silent conditions

    NASA Astrophysics Data System (ADS)

    Virot, Matthieu; Szenknect, Stéphanie; Chave, Tony; Dacheux, Nicolas; Moisy, Philippe; Nikitenko, Sergey I.

    2013-10-01

    The dissolution of uranium carbide (UC) in nitric acid media is considered by means of power ultrasound (sonication) or magnetic stirring. The induction period required to initiate UC dissolution was found to be dramatically shortened when sonicating a 3 M nitric solution (Ar, 20 kHz, 18 W cm-2, 20 °C). At higher acidity, magnetic stirring offers faster dissolution kinetics compared to sonication. Ultrasound-assisted UC dissolution is found to be passivated after ∼60% dissolution and remains incomplete whatever the acidity which is confirmed by ICP-AES, LECO and SEM-EDX analyses. In general, the kinetics of UC dissolution is linked to the in situ generation of nitrous acid in agreement with the general mechanism of UC dissolution; the nitrous acid formation is reported to be faster under ultrasound at low acidity due to the nitric acid sonolysis. The carbon balance shared between the gaseous, liquid, and solid phases is strongly influenced by the applied dissolution procedure and HNO3 concentration.

  15. 20 CFR 404.1219 - Dissolution of political subdivision.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 20 Employees' Benefits 2 2014-04-01 2014-04-01 false Dissolution of political subdivision. 404.1219 Section 404.1219 Employees' Benefits SOCIAL SECURITY ADMINISTRATION FEDERAL OLD-AGE, SURVIVORS AND... Agreements Is Obtained and Continues § 404.1219 Dissolution of political subdivision. If a...

  16. 20 CFR 404.1219 - Dissolution of political subdivision.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 20 Employees' Benefits 2 2011-04-01 2011-04-01 false Dissolution of political subdivision. 404.1219 Section 404.1219 Employees' Benefits SOCIAL SECURITY ADMINISTRATION FEDERAL OLD-AGE, SURVIVORS AND... Agreements Is Obtained and Continues § 404.1219 Dissolution of political subdivision. If a...

  17. 20 CFR 404.1219 - Dissolution of political subdivision.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 20 Employees' Benefits 2 2013-04-01 2013-04-01 false Dissolution of political subdivision. 404.1219 Section 404.1219 Employees' Benefits SOCIAL SECURITY ADMINISTRATION FEDERAL OLD-AGE, SURVIVORS AND... Agreements Is Obtained and Continues § 404.1219 Dissolution of political subdivision. If a...

  18. 20 CFR 404.1219 - Dissolution of political subdivision.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 20 Employees' Benefits 2 2010-04-01 2010-04-01 false Dissolution of political subdivision. 404.1219 Section 404.1219 Employees' Benefits SOCIAL SECURITY ADMINISTRATION FEDERAL OLD-AGE, SURVIVORS AND... Agreements Is Obtained and Continues § 404.1219 Dissolution of political subdivision. If a...

  19. 20 CFR 404.1219 - Dissolution of political subdivision.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 20 Employees' Benefits 2 2012-04-01 2012-04-01 false Dissolution of political subdivision. 404.1219 Section 404.1219 Employees' Benefits SOCIAL SECURITY ADMINISTRATION FEDERAL OLD-AGE, SURVIVORS AND... Agreements Is Obtained and Continues § 404.1219 Dissolution of political subdivision. If a...

  20. Kinetic study of asphaltene dissolution in amphiphile/alkane solutions

    SciTech Connect

    Permsukarome, P.; Chang, C.; Fogler, H.S.

    1997-09-01

    The kinetics of dissolution of pentane-insoluble solid asphaltene precipitates by amphiphile/alkane solutions were investigated using a differential reactor flow system. Two amphiphiles, dodecylbenzenesulfonic acid and nonylphenol, and five alkane solvents, ranging from hexane to hexadecane, were used. Results showed that the rate of asphaltene dissolution in amphiphile/alkane fluids could be approximated with a first-order kinetics with respect to the undissolved asphaltene mass in solution. The specific dissolution rate constant, k, varied with the concentration of amphiphiles, the type of alkane solvents, the temperature, and the fluid flow rate. The rate of asphaltene dissolution displayed a Langmuir-Hinshelwood kinetics with respect to the concentration of amphiphiles. Increasing the temperature of amphiphile/alkane fluids also enhanced the rate of asphaltene dissolution. The apparent activation energy for asphaltene dissolution was approximated to be 4--7 kcal/mol. The rate of asphaltene dissolution was also greater in amphiphile solutions containing lighter alkanes, such as hexane, with lower viscosities. These trends suggest that both surface reaction and mass transfer processes are important to the rate of asphaltene dissolution in amphiphile/alkane fluids.

  1. Dissolution of populations of ultrafine grains with applications to feldspars

    NASA Astrophysics Data System (ADS)

    Talman, S. J.; Nesbitt, H. W.

    1988-06-01

    Mineral dissolution studies are difficult to interpret when the solid reactant displays a wide range in grain sizes, since the rate of dissolution of the finest grains may not be simply related to their surface area. The transient apparent rate of dissolution of a population of fine-grained reactants is modeled to predict changes to the solution composition, as well as changes in the size distribution of ultra-fine particles as functions of time. The model is applied to the experimental data on Amelia albite of HOLDREN and BERNER (1979) from which both solution composition and grain size distribution have been obtained. The observed size distribution cannot be duplicated if the dissolution rate is proportional to surface area ( i.e.dV/dt = Kr 2); other contributions to the rate, such as dependence on grain size and the specific contributions from edges and corners, must be invoked. The observed grain size distribution and pseudo-parabolic rate can be reproduced when the rate of dissolution of the fine grains is proportional to its radius ( i.e.dV/dt = kr ). The rate constant, k, is consistent with a rate limited by dissolution at the edges of the grains. The possibility of predicting both the contribution of ultra-fine particles to the observed dissolution rate and the time evolution of the grain size distribution makes the model a useful tool for interpreting mineral dissolution data.

  2. 10 CFR 960.4-2-6 - Dissolution.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 10 Energy 4 2014-01-01 2014-01-01 false Dissolution. 960.4-2-6 Section 960.4-2-6 Energy DEPARTMENT OF ENERGY GENERAL GUIDELINES FOR THE PRELIMINARY SCREENING OF POTENTIAL SITES FOR A NUCLEAR WASTE REPOSITORY Postclosure Guidelines § 960.4-2-6 Dissolution. (a) Qualifying condition. The site shall...

  3. 10 CFR 960.4-2-6 - Dissolution.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 10 Energy 4 2013-01-01 2013-01-01 false Dissolution. 960.4-2-6 Section 960.4-2-6 Energy DEPARTMENT OF ENERGY GENERAL GUIDELINES FOR THE PRELIMINARY SCREENING OF POTENTIAL SITES FOR A NUCLEAR WASTE REPOSITORY Postclosure Guidelines § 960.4-2-6 Dissolution. (a) Qualifying condition. The site shall...

  4. 10 CFR 960.4-2-6 - Dissolution.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 4 2012-01-01 2012-01-01 false Dissolution. 960.4-2-6 Section 960.4-2-6 Energy DEPARTMENT OF ENERGY GENERAL GUIDELINES FOR THE PRELIMINARY SCREENING OF POTENTIAL SITES FOR A NUCLEAR WASTE REPOSITORY Postclosure Guidelines § 960.4-2-6 Dissolution. (a) Qualifying condition. The site shall...

  5. Thermal dissolution of maize starches in aqueous medium

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Starches are not soluble in neutral water at room temperature. However, if they are heated in a closed container beyond the boiling point of water, they eventually dissolve. The dissolution temperature depends on the type of starch. The dissolution process was monitored in real time by measuring ...

  6. Overview of chemical modeling of nuclear waste glass dissolution

    SciTech Connect

    Bourcier, W.L.

    1991-02-01

    Glass dissolution takes place through metal leaching and hydration of the glass surface accompanied by development of alternation layers of varying crystallinity. The reaction which controls the long-term glass dissolution rate appears to be surface layer dissolution. This reaction is reversible because the buildup of dissolved species in solution slows the dissolution rate due to a decreased dissolution affinity. Glass dissolution rates are therefore highly dependent on silica concentrations in solution because silica is the major component of the alteration layer. Chemical modeling of glass dissolution using reaction path computer codes has successfully been applied to short term experimental tests and used to predict long-term repository performance. Current problems and limitations of the models include a poorly defined long-term glass dissolution mechanism, the use of model parameters determined from the same experiments that the model is used to predict, and the lack of sufficient validation of key assumptions in the modeling approach. Work is in progress that addresses these issues. 41 refs., 7 figs., 2 tabs.

  7. Chlorite dissolution rates under CO2 saturated conditions from 50 to 120 °C and 120 to 200 bar CO2

    NASA Astrophysics Data System (ADS)

    Black, Jay R.; Haese, Ralf R.

    2014-01-01

    Chlorite dissolution rates were measured in a series of batch reactor experiments testing the effect of pCO2, pH, chloride and bicarbonate concentrations and temperature. Chlorite is an important diagenetic mineral in sedimentary basins, often found cementing mineral grains and filling pore space in formations that may serve as reservoirs for storing carbon dioxide. Conflicting reports of whether chlorite acts as a barrier to reservoir rock reactivity or leads to enhanced porosity due to dissolution, after the injection of supercritical CO2 into a reservoir, makes studying the reactivity of chlorite in contact with CO2 saturated waters pertinent. Measured dissolution rates were initially rapid and decreased over time as the saturation state of solution relative to chlorite increased. Temperature had the strongest effect on dissolution rate, with an apparent activation energy of 16 ± 0.5 kJ mol-1 and rate constant of log k0 = -9.56 ± 0.07 mol m-2 s-1 assuming a rate law of the form: rate = k0exp(-EA/RT). The apparent activation energy is lower than previously accepted values, but is consistent with a study of chlorite dissolution using flow through techniques (Smith et al., 2013). Mineral dissolution rates are typically proton enhanced, but the lack of a significant pH effect or pCO2 effect on chlorite dissolution rate in this study suggests that the use of NaHCO3 to buffer the pH of CO2 saturated solutions led to an inhibition of mineral dissolution in competition with the expected pH effect. This is supported by the observed dissolution rate increasing dramatically (half a log unit) with the use of an organic acid buffer (KHpthalate) under CO2 free conditions. The effect of chloride (NaCl ∼5 to 50 g/L) was found not to affect the dissolution rate of chlorite. Various empirical rate laws are proposed and fit to the data and lead to the development of a surface complex model describing proton promoted dissolution and bicarbonate inhibition of chlorite

  8. The maximal affinity of ligands

    PubMed Central

    Kuntz, I. D.; Chen, K.; Sharp, K. A.; Kollman, P. A.

    1999-01-01

    We explore the question of what are the best ligands for macromolecular targets. A survey of experimental data on a large number of the strongest-binding ligands indicates that the free energy of binding increases with the number of nonhydrogen atoms with an initial slope of ≈−1.5 kcal/mol (1 cal = 4.18 J) per atom. For ligands that contain more than 15 nonhydrogen atoms, the free energy of binding increases very little with relative molecular mass. This nonlinearity is largely ascribed to nonthermodynamic factors. An analysis of the dominant interactions suggests that van der Waals interactions and hydrophobic effects provide a reasonable basis for understanding binding affinities across the entire set of ligands. Interesting outliers that bind unusually strongly on a per atom basis include metal ions, covalently attached ligands, and a few well known complexes such as biotin–avidin. PMID:10468550

  9. Convective dissolution of carbon dioxide in saline aquifers

    NASA Astrophysics Data System (ADS)

    Neufeld, Jerome A.; Hesse, Marc A.; Riaz, Amir; Hallworth, Mark A.; Tchelepi, Hamdi A.; Huppert, Herbert E.

    2010-11-01

    Geological carbon dioxide (CO2) storage is a means of reducing anthropogenic emissions. Dissolution of CO2 into the brine, resulting in stable stratification, increases storage security. The dissolution rate is determined by convection in the brine driven by the increase of brine density with CO2 saturation. We present a new analogue fluid system that reproduces the convective behaviour of CO2-enriched brine. Laboratory experiments and high-resolution numerical simulations show that the convective flux scales with the Rayleigh number to the 4/5 power, in contrast with a classical linear relationship. A scaling argument for the convective flux incorporating lateral diffusion from downwelling plumes explains this nonlinear relationship for the convective flux, provides a physical picture of high Rayleigh number convection in a porous medium, and predicts the CO2 dissolution rates in CO2 accumulations. These estimates of the dissolution rate show that convective dissolution can play an important role in enhancing storage security.

  10. Aluminum Target Dissolution in Support of the Pu-238 Program

    SciTech Connect

    McFarlane, Joanna; Benker, Dennis; DePaoli, David W; Felker, Leslie Kevin; Mattus, Catherine H

    2014-09-01

    Selection of an aluminum alloy for target cladding affects post-irradiation target dissolution and separations. Recent tests with aluminum alloy 6061 yielded greater than expected precipitation in the caustic dissolution step, forming up to 10 wt.% solids of aluminum hydroxides and aluminosilicates. We present a study to maximize dissolution of aluminum metal alloy, along with silicon, magnesium, and copper impurities, through control of temperature, the rate of reagent addition, and incubation time. Aluminum phase transformations have been identified as a function of time and temperature, using X-ray diffraction. Solutions have been analyzed using wet chemical methods and X-ray fluorescence. These data have been compared with published calculations of aluminum phase diagrams. Temperature logging during the transients has been investigated as a means to generate kinetic and mass transport data on the dissolution process. Approaches are given to enhance the dissolution of aluminum and aluminosilicate phases in caustic solution.

  11. DFT Study of Acceptorless Alcohol Dehydrogenation Mediated by Ruthenium Pincer Complexes: Ligand Tautomerization Governing Metal Ligand Cooperation.

    PubMed

    Hou, Cheng; Zhang, Zhihan; Zhao, Cunyuan; Ke, Zhuofeng

    2016-07-01

    Metal ligand cooperation (MLC) catalysis is a popular strategy to design highly efficient transition metal catalysts. In this presented theoretical study, we describe the key governing factor in the MLC mechanism, with the Szymczak's NNN-Ru and the Milstein's PNN-Ru complexes as two representative catalysts. Both the outer-sphere and inner-sphere mechanisms were investigated and compared. Our calculated result indicates that the PNN-Ru pincer catalyst will be restored to aromatic state during the catalytic cycle, which can be considered as the driving force to promote the MLC process. On the contrary, for the NNN-Ru catalyst, the MLC mechanism leads to an unfavored tautomerization in the pincer ligand, which explains the failure of the MLC mechanism in this system. Therefore, the strength of the driving force provided by the pincer ligand actually represents a prerequisite factor for MLC. Spectator ligands such as CO, PPh3, and hydride are important to ensure the catalyst follow a certain mechanism as well. We also evaluate the driving force of various bifunctional ligands by computational methods. Some proposed pincer ligands may have the potential to be the new pincer catalysts candidates. The presented study is expected to offer new insights for MLC catalysis and provide useful guideline for future catalyst design. PMID:27322755

  12. Enhanced dissolution and systemic availability of albendazole formulated as solid dispersions.

    PubMed

    Castro, Silvina G; Sanchez Bruni, Sergio F; Urbizu, Lucía P; Confalonieri, Alejandra; Ceballos, Laura; Lanusse, Carlos E; Allemandi, Daniel A; Palma, Santiago D

    2013-01-01

    Solid dispersions (SDs) containing the anthelmintic compound albendazole (ABZ) and either Pluronic 188 (P 188) or polyethylene glycol 6000 (PEG 6000) as hydrophilic carriers were formulated. Drug-polymers interactions in solid state were investigated using different techniques. Only a 4% of total ABZ was dissolved at 5 min post-incubation, reaching dissolution rates of 32.8% (PEG 6000) and 69.4% (P 188) in SDs. In this way, P 188 was substantially more efficient as ABZ dissolution promoter in comparison to PEG 6000, especially at the initial stages of the dissolution processes (<30 min). An increased systemic availability (p < 0.001) was obtained when ABZ was administered as ABZ-P 188 SDs, with a 50% enhancement in systemic exposure (AUC values) compared to treatment with an ABZ suspension. Consistently, the Cmax increased 130% (p < 0.001) following treatment with P 188 based SD ABZ formulation. For the ABZ-PEG 6000 SD formulation, the favorable effect on ABZ systemic availability did not reached statistical significance compared to the control group. The study reported here showed the utility of pharmacokinetic assays performed on mice as a model for preliminary drug formulation screening studies. PMID:22670782

  13. Carbonate ions and arsenic dissolution by groundwater

    USGS Publications Warehouse

    Kim, M.-J.; Nriagu, J.; Haack, S.

    2000-01-01

    solutions. The effects of pH and redox conditions on As dissolution were examined. Results showed that As was not leached significantly out of the Marshall Sandstone samples after 3 d using either deionized water or groundwater, but As was leached efficiently by sodium bicarbonate, potassium bicarbonate, and ferric chloride solutions. The leaching rate with sodium bicarbonate was about 25% higher than that with potassium bicarbonate. The data indicated that bicarbonate ion was involved primarily in As dissolution and that hydroxyl radical ion did not affect As dissolution to any significant degree. The amount of As leached was dependent upon the sodium bicarbonate concentration, increasing with reaction time for each concentration. Significant As leaching was found in the extreme pH ranges of <1.9 and 8.0-10.4. The resulting arseno-carbonate complexes formed were stable in groundwater.

  14. Tissue dissolution and modifications in dentin composition by different sodium hypochlorite concentrations

    PubMed Central

    TARTARI, Talita; BACHMANN, Luciano; MALIZA, Amanda Garcia Alves; ANDRADE, Flaviana Bombarda; DUARTE, Marco Antonio Hungaro; BRAMANTE, Clovis Monteiro

    2016-01-01

    ABSTRACT Sodium hypochlorite (NaOCl) remains the most used irrigation solution during root canal preparation because of characteristics such as wide-spectrum antimicrobial activity and organic tissue dissolution capacity. However, these solutions can alter dentin composition and there is no consensus on the optimal concentration of NaOCl to be used. Objectives To determine the organic matter dissolution and changes in dentin chemical composition promoted by different concentrations of NaOCl over time. Material and Methods: Fragments of bovine muscle tissue were weighed before and after 5, 10, and 15 min of immersion in the groups (n=10): G1- 0.9% saline solution; G2- 1% NaOCl; G3- 2.5% NaOCl; and G4- 5% NaOCl. Bovine dentin fragments were subjected to the same irrigants and absorption spectra were collected by Attenuated Total Reflectance of Fourier Transform Infrared Spectroscopy (ATR-FTIR) before and after 0,5, 1, 2, 3, 5, 8, and 10 min of immersion in the solutions. The ratios of the amide III/phosphate and carbonate/phosphate absorption bands were determined. The tissue dissolution and carbonate/phosphate ratios were submitted to the two-way analysis of variance (ANOVA) with Tukey’s multiple-comparison test (α<0.05) and to the one-way analysis of variance with Tukey’s (α<0.05). The amide III/phosphate ratio was analyzed by Friedman test (α<0.05) and the Kruskal-Wallis test with Dunn’s post-hoc (α<0.05). Results The increase in NaOCl concentration and contact time intensified the dissolution of organic matter and dentin collagen with reduction in the amide III/phosphate ratio. Significant differences between all groups (p<0.05) were observed in the dissolution of organic matter at 10 min and in the amide III/phosphate ratio between the saline solution and 5% NaOCl at 5 min. The carbonate/phosphate ratio decreased significantly in G2, G3, and G4 after 0,5 min of immersion (p<0.05), but more alterations did not occur in the subsequent periods (p>0

  15. The role of carboxylic acids in albite and quartz dissolution: An experimental study under diagenetic conditions

    NASA Astrophysics Data System (ADS)

    Franklin, Stan P.; Hajash, Andrew, Jr.; Dewers, Thomas A.; Tieh, Thomas T.

    1994-10-01

    Simple water soluble organic acids may promote secondary porosity development in sandstones during diagenesis by increasing feldspar solubility and dissolution rate. To test this hypothesis, Amelia albite and Brazilian hydrothermal quartz were reacted with 0.07 m acetate and 0.07 m acetate-0.005 m oxalate solutions at selected pH values, and distilled water. Pore fluid chemistry was monitored through time at various flow rates to obtain both solubility and dissolution rate data. The experiments were conducted in large volume, semi-static, flow-through systems at 100°C and 347 bars. These systems simulate subsurface flow rates, low mass water/rock, and high surface area/fluid mass. Acetate and acetate + oxalate solutions significantly increase albite solubility at temperatures, pressures, and pH values typical of diagenetic environments. Albite solubilities increased in acetate and acetate + oxalate solutions by factors of 2 and 3.4, respectively, compared to distilled water. In these same solutions, Al concentrations were ≈ 140 and ≈480 times higher than that calculated for kaolinite solubility at the same conditions without organic species. These enhanced solubilities occur at pH values (4.6-4.8) that may overlap with formation waters. In contrast to albite, quartz solubility was essentially identical in all solutions investigated. Dissolution rates in the acid region decreased with increasing pH in the acetate and acetate + oxalate solutions. Slopes of log rate vs. pH curves were ≈0.6 for acetate and ≈0.3 for acetate + oxalate. Although the effects of acetate on the dissolution rate are small, the effects of oxalate are significant. A rate law valid for albite dissolution at 100°C, oxalate concentrations to 0.01 m, and pH values ranging from 3.4 to 5.5 is given below (assuming activity coefficients = 1 and acetate rate ≈ the proton-promoted rate): Rtotal = 5.88 × 10 -11+ 5.01 × 10 -8m 0.56H+ + 6.7 ×10 -102.3 × 10 -4m O x/(1.0+2.3 × 10 -4 m O x

  16. Instabilities in geomaterials induced by dissolution

    NASA Astrophysics Data System (ADS)

    Stefanou, I.; Sulem, J.

    2015-12-01

    Deformation bands play an important role in reservoir engineering, geological storage, underwater landslides and slow geological procedures. Various mechanisms can be involved at different scales and may be responsible for deformation bands. Mechanical and chemical degradation of the grain skeleton is a softening factor that can lead to compaction, shear or even dilation band formation [1]-[3]. The present study is twofold. On one hand it focuses on the mathematical modeling of chemically induced strain localization instabilities in porous rocks and on the other hand it explores the conditions for their creation [4], [5]. In a saturated porous rock, the progressive mechanical damage of the solid skeleton during deformation, results in the increase of the interface area of the reactants and consequently in the acceleration of the dissolution rate of the solid phase [6]. Under the presence of dissolving fluids the solid skeleton is degraded more rapidly (mass removal because of dissolution), the overall mechanical properties of the system diminish (contraction of the elastic domain - chemical softening), deformations increase and the solid skeleton is further damaged (intergranular fractures, debonding, breakage of the porous network etc.). Based on a micromechanical model, the conditions for deformation band triggering are investigated analytically. The heterogeneity of the microstructure in terms of chemical reactivity of the constituents of the REV is taken into account resulting in a characteristic internal length of the system. The post bifurcation behavior is finally studied both analytically and numerically revealing the thickness of the localized zone. References[1] I. Stefanou and J. Sulem, DOI: 10.1002/2013JB010342 [2] M. Cha and J. C. Santamarina, DOI: 10.1680/geot.14P.115 [3] M. D. Ingraham, K. A. Issen, and D. J. Holcomb, DOI: 10.1007/s11440-013-0275-y [4] K. A. Issen and J. W. Rudnicki, DOI: 10.1029/2000JB900185 [5] J. W. Rudnicki and J. R. Rice, DOI

  17. Dissolution rate enhancement of gliclazide by ordered mixing.

    PubMed

    Saharan, Vikas A; Choudhury, Pratim K

    2011-09-01

    The poorly water soluble antidiabetic drug gliclazide was selected to study the effect of excipients on dissolution rate enhancement. Ordered mixtures of micronized gliclazide with lactose, mannitol, sorbitol, maltitol and sodium chloride were prepared by manual shaking of glass vials containing the drug and excipient(s). Different water soluble excipients, addition of surfactant and superdisintegrant, drug concentration and carrier particle size influenced the dissolution rate of the drug. Dissolution rate studies of the prepared ordered mixtures revealed an increase in drug dissolution with all water soluble excipients. The order of dissolution rate improvement for gliclazide was mannitol > lactose > maltitol > sorbitol > sodium chloride. Composite granules of the particle size range 355-710 μm were superior in increasing the drug dissolution rate from ordered mixtures. Reducing the carrier particle size decreased the dissolution rate of the drug as well as the increase in drug concentration. Kinetic modeling of drug release data fitted best the Hixson-Crowell model, which indicates that all the ordered mixture formulations followed the cube root law fairly well. PMID:21945911

  18. Dissolution rate measurements of TiN in Ti-6242

    SciTech Connect

    Bewlay, B.P.; Gigliotti, M.F.X.

    1997-01-01

    This paper describes measurements of the dissolution rate of nitrided Ti sponge and monolithic TiN rod in molten Ti-6242. The dissolution rate is described in terms of an interface recession rate that was 2.2 {micro}m/s for a Ti-6242 temperature of 1,725 C and dissolution times between 1 and 100 min. Similar dissolution rates were measured for nitrided sponge and monolithic rod. This report also descries the microstructural and chemical interdiffusion phenomena that occur during dissolution of solid {delta}TiN in molten Ti-6242. There is a N-containing solid {alpha}Ti layer and a N-solidified {beta}Ti layer between the solid {delta}TiN and liquid Ti-6242 during dissolution. Microprobe measurements indicate that diffusion of Al, Zr, Sn and Mo into {delta}TiN did not occur. Steep N concentration profiles were observed in the {alpha}Ti layer. Al, Zr, Sn and Mo were observed in the N-solidified {beta}Ti layer contained <1% N. Similar microstructural and interdiffusional behaviors were observed during dissolution of nitrided sponge and monolithic {delta}TiN rod in molten Ti-6242.

  19. CTAB-Influenced Electrochemical Dissolution of Silver Dendrites.

    PubMed

    O'Regan, Colm; Zhu, Xi; Zhong, Jun; Anand, Utkarsh; Lu, Jingyu; Su, Haibin; Mirsaidov, Utkur

    2016-04-19

    Dendrite formation on the electrodes of a rechargeable battery during the charge-discharge cycle limits its capacity and application due to short-circuits and potential ignition. However, understanding of the underlying dendrite growth and dissolution mechanisms is limited. Here, the electrochemical growth and dissolution of silver dendrites on platinum electrodes immersed in an aqueous silver nitrate (AgNO3) electrolyte solution was investigated using in situ liquid-cell transmission electron microscopy (TEM). The dissolution of Ag dendrites in an AgNO3 solution with added cetyltrimethylammonium bromide (CTAB) surfactant was compared to the dissolution of Ag dendrites in a pure aqueous AgNO3 solution. Significantly, when CTAB was added, dendrite dissolution proceeded in a step-by-step manner, resulting in nanoparticle formation and transient microgrowth stages due to Ostwald ripening. This resulted in complete dissolution of dendrites and "cleaning" of the cell of any silver metal. This is critical for practical battery applications because "dead" lithium is known to cause short circuits and high-discharge rates. In contrast to this, in a pure aqueous AgNO3 solution, without surfactant, dendrites dissolved incompletely back into solution, leaving behind minute traces of disconnected silver particles. Finally, a mechanism for the CTAB-influenced dissolution of silver dendrites was proposed based on electrical field dependent binding energy of CTA(+) to silver. PMID:27017834

  20. Dissolution behaviour of silicon nitride coatings for joint replacements.

    PubMed

    Pettersson, Maria; Bryant, Michael; Schmidt, Susann; Engqvist, Håkan; Hall, Richard M; Neville, Anne; Persson, Cecilia

    2016-05-01

    In this study, the dissolution rate of SiNx coatings was investigated as a function of coating composition, in comparison to a cobalt chromium molybdenum alloy (CoCrMo) reference. SiNx coatings with N/Si ratios of 0.3, 0.8 and 1.1 were investigated. Electrochemical measurements were complemented with solution (inductively coupled plasma techniques) and surface analysis (vertical scanning interferometry and x-ray photoelectron spectroscopy). The dissolution rate of the SiNx coatings was evaluated to 0.2-1.4nm/day, with a trend of lower dissolution rate with higher N/Si atomic ratio in the coating. The dissolution rates of the coatings were similar to or lower than that of CoCrMo (0.7-1.2nm/day). The highest nitrogen containing coating showed mainly Si-N bonds in the bulk as well as at the surface and in the dissolution area. The lower nitrogen containing coatings showed Si-N and/or Si-Si bonds in the bulk and an increased formation of Si-O bonds at the surface as well as in the dissolution area. The SiNx coatings reduced the metal ion release from the substrate. The possibility to tune the dissolution rate and the ability to prevent release of metal ions encourage further studies on SiNx coatings for joint replacements. PMID:26952452

  1. Miniaturized INtrinsic DISsolution Screening (MINDISS) assay for preformulation.

    PubMed

    Alsenz, Jochem; Haenel, Elisabeth; Anedda, Aline; Du Castel, Pauline; Cirelli, Giorgio

    2016-05-25

    This study describes a novel Miniaturized INtrinsic DISsolution Screening (MINDISS) assay for measuring disk intrinsic dissolution rates (DIDR). In MINDISS, compacted mini disks of drugs (2-5mg/disk) are prepared in custom made holders with a surface area of 3mm(2). Disks are immersed, pellet side down, into 0.35ml of appropriate dissolution media per well in 96-well microtiter plates, media are stirred and disk-holders are transferred to new wells after defined periods of time. After filtration, drug concentration in dissolution media is quantified by Ultra Performance Liquid Chromatography (UPLC) and solid state property of the disk is characterized by Raman spectroscopy. MINDISS was identified as an easy-to-use tool for rapid, parallel determination of DIDR of compounds that requires only small amounts of compound and of dissolution medium. Results obtained with marketed drugs in MINDISS correlate well with large scale DIDR methods and indicate that MINDISS can be used for (1) rank-ordering of compounds by intrinsic dissolution in late phase discovery and early development, (2) comparison of polymorphic forms and salts, (3) screening and selection of appropriate dissolution media, and (4) characterization of the intestinal release behavior of compounds along the gastro intestinal tract by changing biorelevant media during experiments. PMID:26360839

  2. Evaluation of fluorinated dissolution inhibitors for 157-nm lithography

    NASA Astrophysics Data System (ADS)

    Hamad, Alyssandrea H.; Houlihan, Francis M.; Seger, Larry; Chang, Chun; Ober, Christopher K.

    2003-06-01

    Fluorinated diesters were synthesized and evaluated as dissolution inhibitors (DIs) for 157 nm lithography. The results of dissolution rate measurements, exposure studies, and etching experiments on blends of fluorinated polymers containing these dissolution inhibitors are reported. It was shown that the DIs effectively slow the dissolution rate of the matrix polymer, poly(hexafluorohydroxyisopropyl styrene) (PHFHIPS). Etching studies show that they enhance the plasma etch resistance of poly(methyl methacrylate) using tetrafluoromethane plasma. Addition of the best performing dissolution inhibitor, cyclohexane-1,4-dicarboxylic acid bis-(1-cyclohexyl-2,2,2-trifluoro-1-methyl-ethyl) ester) (FCDE1) to candidate 157 nm photoresist polymers, Duvcor and poly(hexafluorohydroxyisopropyl styrene)-co-poly(t-butyl methacrylate) [pPHFHIPS-co-pt-BMA], improves the imaging behavior of these polymers. Our attempts to elucidate the mechanism of dissolution inhibition for this series of compounds will be discussed. Fourier Transform Infrared (FTIR) studies in conjunction with dissolution rate measurements performed on a series of DI analogues suggest a mechanism based on hydrogen bonding.

  3. Dissolution and reduction of magnetite by bacteria

    NASA Technical Reports Server (NTRS)

    Kostka, J. E.; Nealson, K. H.

    1995-01-01

    Magnetite (Fe3O4) is an iron oxide of mixed oxidation state [Fe(II), Fe(III)] that contributes largely to geomagnetism and plays a significant role in diagenesis in marine and freshwater sediments. Magnetic data are the primary evidence for ocean floor spreading and accurate interpretation of the sedimentary magnetic record depends on an understanding of the conditions under which magnetite is stable. Though chemical reduction of magnetite by dissolved sulfide is well known, biological reduction has not been considered likely based upon thermodynamic considerations. This study shows that marine and freshwater strains of the bacterium Shewanella putrefaciens are capable of the rapid dissolution and reduction of magnetite, converting millimolar amounts to soluble Fe(II)in a few days at room temperature. Conditions under which magnetite reduction is optimal (pH 5-6, 22-37 degrees C) are consistent with an enzymatic process and not with simple chemical reduction. Magnetite reduction requires viable cells and cell contact, and it appears to be coupled to electron transport and growth. In a minimal medium with formate or lactate as the electron donor, more than 10 times the amount of magnetite was reduced over no carbon controls. These data suggest that magnetite reduction is coupled to carbon metabolism in S. putrefaciens. Bacterial reduction rates of magnetite are of the same order of magnitude as those estimated for reduction by sulfide. If such remobilization of magnetite occurs in nature, it could have a major impact on sediment magnetism and diagenesis.

  4. Dissolution and reduction of magnetite by bacteria.

    PubMed

    Kostka, J E; Nealson, K H

    1995-10-01

    Magnetite (Fe3O4) is an iron oxide of mixed oxidation state [Fe(II), Fe(III)] that contributes largely to geomagnetism and plays a significant role in diagenesis in marine and freshwater sediments. Magnetic data are the primary evidence for ocean floor spreading and accurate interpretation of the sedimentary magnetic record depends on an understanding of the conditions under which magnetite is stable. Though chemical reduction of magnetite by dissolved sulfide is well known, biological reduction has not been considered likely based upon thermodynamic considerations. This study shows that marine and freshwater strains of the bacterium Shewanella putrefaciens are capable of the rapid dissolution and reduction of magnetite, converting millimolar amounts to soluble Fe(II)in a few days at room temperature. Conditions under which magnetite reduction is optimal (pH 5-6, 22-37 degrees C) are consistent with an enzymatic process and not with simple chemical reduction. Magnetite reduction requires viable cells and cell contact, and it appears to be coupled to electron transport and growth. In a minimal medium with formate or lactate as the electron donor, more than 10 times the amount of magnetite was reduced over no carbon controls. These data suggest that magnetite reduction is coupled to carbon metabolism in S. putrefaciens. Bacterial reduction rates of magnetite are of the same order of magnitude as those estimated for reduction by sulfide. If such remobilization of magnetite occurs in nature, it could have a major impact on sediment magnetism and diagenesis. PMID:11539843

  5. Dissolution of three insensitive munitions formulations.

    PubMed

    Taylor, Susan; Park, Eileen; Bullion, Katherine; Dontsova, Katerina

    2015-01-01

    The US military fires live munitions during training. To save soldiers lives both during training and war, the military is developing insensitive munitions (IM) that minimize unintentional detonations. Some of the compounds in the IM formulation are, however, very soluble in water, raising environmental concerns about their fate and transport. We measured the dissolution of three of these IM formulations, IMX101, IMX104 and PAX21 using laboratory drip tests and studied the accompanying changes in particle structure using micro computed tomography. Our laboratory drip tests mimic conditions on training ranges, where spatially isolated particles of explosives scattered by partial detonations are dissolved by rainfall. We found that the constituents of these IM formulations dissolve sequentially and in the order predicted by their aqueous solubility. The order of magnitude differences in solubility among their constituents produce water solutions whose compositions and concentrations vary with time. For IMX101 and IMX104, that contain 3-nitro-1,2,4-triazol-5-one (NTO), the solutions also vary in pH. The good mass balances measured for the drip tests indicate that the formulations are not being photo-or bio-transformed under laboratory conditions. PMID:25043961

  6. Dissolution of oxygen-enriched Zircaloy-2

    NASA Astrophysics Data System (ADS)

    Oskarsson, M.; Ahlberg, E.; Pettersson, K.

    2001-10-01

    When metal is removed from oxidised Zircaloy specimens in order to study the morphology of the oxide at the metal-oxide interface needle-like features are frequently observed. Since similar features are not observed in cross-section TEM examinations it has been questioned whether or not the needles are a result of the dissolution process. In particular it has been proposed that reprecipitation of oxide may take place when the metal is enriched with oxygen. In the present work oxygen-enriched Zircaloy has been dissolved and the resulting structures examined. The results indicate that the needles are in fact artefacts of the specimen preparation procedure. However, there are no significant differences between oxygen-enriched and normal Zircaloy below an oxide layer grown in steam at about 400 °C. In view of the differences between the needle structure observed after metal removal with bromine or by electropolishing and removal by HF-HNO 3 pickling solution it is speculated that the needles consist of a hydrous zirconium oxide which is unstable in the pickling solution.

  7. Cytotoxicity and intracellular dissolution of nickel nanowires.

    PubMed

    Perez, Jose E; Contreras, Maria F; Vilanova, Enrique; Felix, Laura P; Margineanu, Michael B; Luongo, Giovanni; Porter, Alexandra E; Dunlop, Iain E; Ravasi, Timothy; Kosel, Jürgen

    2016-09-01

    The assessment of cytotoxicity of nanostructures is a fundamental step for their development as biomedical tools. As widely used nanostructures, nickel nanowires (Ni NWs) seem promising candidates for such applications. In this work, Ni NWs were synthesized and then characterized using vibrating sample magnetometry, energy dispersive X-Ray analysis, and electron microscopy. After exposure to the NWs, cytotoxicity was evaluated in terms of cell viability, cell membrane damage, and induced apoptosis/necrosis on the model human cell line HCT 116. The influence of NW to cell ratio (10:1 to 1000:1) and exposure times up to 72 hours was analyzed for Ni NWs of 5.4 μm in length, as well as for Ni ions. The results show that cytotoxicity markedly increases past 24 hours of incubation. Cellular uptake of NWs takes place through the phagocytosis pathway, with a fraction of the dose of NWs dissolved inside the cells. Cell death results from a combination of apoptosis and necrosis, where the latter is the outcome of the secondary necrosis pathway. The cytotoxicity of Ni ions and Ni NWs dissolution studies suggest a synergistic toxicity between NW aspect ratio and dissolved Ni, with the cytotoxic effects markedly increasing after 24 hours of incubation. PMID:26692167

  8. Physiologically Based In vitro Models to Predict the Oral Dissolution and Absorption of a Solid Drug Delivery System.

    PubMed

    Li, Ziqiang; He, Xin

    2015-01-01

    To understand the sophisticated dynamic behaviors of drug elution and permeation in the gastrointestinal tract (GIT), researchers have tried to reemerge it by employing various in vitro experimental models. However, official in vitro apparatuses routinely used for quality control purposes, employ simple, non-physiologic buffers, and hydrodynamics conditions, and can not accurately perform continuous, dynamic in vivo pharmacokinetics (PK) behaviors. Therefore, different angles of GI physiology information are incorporate into novel models to forecast the dissolution and permeation of drug solid dosage forms. This review, in general, discusses some related studies of physiologically-based mechanical models to predict human absorption following oral administration in four sections. First the GIT, taken out of a complex physiological environment, where the drug is absorbed, distributed, metabolized and excreted (ADME) in the human body, is considered as the physiological basis for active pharmaceutics ingredients (API) dissolved and permeated through the epithelial cell. The second part embodies the theoretical foundation of in vitro models to predict human absorption and the corresponding in vitro.in vivo correlations (IVIVC). The third section summarizes physiologically based dissolution models developed recently, ranging from dynamic compartmental dissolution models, to biorelevant dissolution models based on certain physiological factors, to biphasic dissolution models. The last part is devoted to combined dissolution and absorption models that can be employed to simulate the continuous, dynamic behavior of oral drug delivery being dissolved and subsequently permeated across the GIT. Along with physiologically-based mechanically models spring up, pharmaceutical researchers will harvest better level A IVIVC for oral drug delivery systems, especially for sustained and controlled release preparations. On the other way hand, it will successively promote more effective

  9. A spatially resolved surface kinetic model for forsterite dissolution

    NASA Astrophysics Data System (ADS)

    Maher, Kate; Johnson, Natalie C.; Jackson, Ariel; Lammers, Laura N.; Torchinsky, Abe B.; Weaver, Karrie L.; Bird, Dennis K.; Brown, Gordon E.

    2016-02-01

    The development of complex alteration layers on silicate mineral surfaces undergoing dissolution is a widely observed phenomenon. Given the complexity of these layers, most kinetic models used to predict rates of mineral-fluid interactions do not explicitly consider their formation. As a result, the relationship between the development of the altered layers and the final dissolution rate is poorly understood. To improve our understanding of the relationship between the alteration layer and the dissolution rate, we developed a spatially resolved surface kinetic model for olivine dissolution and applied it to a series of closed-system experiments consisting of three-phases (water (±NaCl), olivine, and supercritical CO2) at conditions relevant to in situ mineral carbonation (i.e. 60 °C, 100 bar CO2). We also measured the corresponding δ26/24Mg of the dissolved Mg during early stages of dissolution. Analysis of the solid reaction products indicates the formation of Mg-depleted layers on the olivine surface as quickly as 2 days after the experiment was started and before the bulk solution reached saturation with respect to amorphous silica. The δ26/24Mg of the dissolved Mg decreased by approximately 0.4‰ in the first stages of the experiment and then approached the value of the initial olivine (-0.35‰) as the steady-state dissolution rate was approached. We attribute the preferential release of 24Mg to a kinetic effect associated with the formation of a Mg-depleted layer that develops as protons exchange for Mg2+. We used experimental data to calibrate a surface kinetic model for olivine dissolution that includes crystalline olivine, a distinct "active layer" from which Mg can be preferentially removed, and secondary amorphous silica precipitation. By coupling the spatial arrangement of ions with the kinetics, this model is able to reproduce both the early and steady-state long-term dissolution rates, and the kinetic isotope fractionation. In the early stages of

  10. Dissolution retardation of solid silica during glass batch-melting

    SciTech Connect

    Hrma, Pavel R.; Marcial, Jose

    2011-07-15

    During glass-batch melting, solid silica (quartz) usually dissolves last. A retardation function was defined as a measure of the progressive inhibition of silica dissolution that occurs during batch melting. This function is based on the comparison of the measured rate of dissolution of silica particles with the hypothetical diffusion-controlled volume flux from regularly distributed particles with uniform concentration layers around them. The severe inhibition of silica dissolution has been attributed to the irregular spatial distribution of silica particles that is associated with the formation of nearly saturated melt at a portion of their surfaces. Irregular shapes and unequal sizes of particles also contribute to their extended lifetime.

  11. Calcite dissolution: an in situ study in the Panama Basin

    SciTech Connect

    Thunell, R.C.; Keir, R.S.; Honjo, S.

    1981-05-08

    The results of an in situ study of calcite dissolution in the Panama Basin indicate that the rate of dissolution in the water column increases suddenly below a water depth of about 2800 meters. This coincides with the depth at which the calcium carbonate content of surface sediments begins to decrease rapidly or the sedimentary lysocline. Since this level of increased dissolution both in the water column and on the sea floor does not appear to be related to the transition from supersaturation to undersaturation with respect to carbonate, there may be a kinetic origin for the lysocline in this region.

  12. Dissolution rate and apparent solubility of poorly soluble drugs in biorelevant dissolution media.

    PubMed

    Fagerberg, Jonas H; Tsinman, Oksana; Sun, Na; Tsinman, Konstantin; Avdeef, Alex; Bergström, Christel A S

    2010-10-01

    A series of poorly soluble BCS class II compounds with "grease ball" characteristics were assessed for solubility and dissolution rate in biorelevant dissolution media (BDM) with the purpose of investigating which molecular structures gain most in solubility when dissolved under physiologically relevant conditions. The compounds were studied in four media (simulated intestinal fluid in fasted (FaSSIF pH 6.5) and fed state (FeSSIF pH 5.0), and their corresponding blank buffers (FaSSIF(blk) and FeSSIF(blk))) at a temperature of 37 °C. The experimental results were used to analyze which molecular characteristics are of importance for the solubility in BDM and for in silico modeling using multivariate data analysis. It was revealed that a majority of the compounds exhibited a higher dissolution rate and higher solubility in the FaSSIF and FeSSIF than in their corresponding blank buffers. Compounds which were neutral or carried a positive charge were more soluble in FeSSIF than FaSSIF. The acidic compounds displayed clear pH dependency, although the higher concentration of solubilizing agents in FeSSIF than FaSSIF also improved the solubility. Five of the ten compounds were upgraded to BCS class I when dissolved in FaSSIF or FeSSIF, i.e., the maximum dose of these compounds given orally was soluble in 250 mL of these BDMs. Lipophilicity as described by the log D(oct) value was identified as a good predictor of the solubilization ratio (R(2) = 0.74), and computed molecular descriptors were also shown to successfully predict the solubilities in BDM for this data set. To conclude, the physiological solubility of "grease ball" molecules may be largely underestimated in in vitro solubility assays unless BDM is used. Moreover, the results herein indicate that the improvement obtained in BDM may be possible to predict from chemical features alone. PMID:20507160

  13. Magnesite growth inhibition by organic ligands: An experimental study at 100, 120 and 146 °C

    NASA Astrophysics Data System (ADS)

    Gautier, Quentin; Bénézeth, Pascale; Schott, Jacques

    2016-05-01

    It has been proposed that simple organic ligands, which accelerate Mg-silicates dissolution, could be used to accelerate CO2 mineral sequestration through mineral carbonation. The influence of these ligands on magnesite growth has however never been quantified. In this work, we investigated the influence of three organic ligands: oxalate, citrate and EDTA on magnesite growth in alkaline conditions and at hydrothermal temperatures (100, 120 and 146 °C) using mixed flow reactors. We show that the studied carboxylates decrease magnesite growth rates, due to two converging mechanisms: Complexation of Mg2+ in solution, which decreases the saturation state of the solution. This effect was carefully taken into account by using a thermodynamic database relevant for the studied system. EDTA being the stronger chelate of the three investigated ligands, it has the strongest influence on solution saturation state. Adsorption of the ligand on magnesite surface growth sites, which decreases the kinetic rate constant of magnesite growth. We observed the following inhibition effectiveness of investigated organic ligands: citrate > EDTA > oxalate. While citrate exerts the strongest growth inhibition due to adsorption, it does not apparently lead to a complete interruption of magnesite growth. Preliminary adsorption experiments suggest that citrate adsorbs to active growth sites at the mineral surface with a much higher affinity than for the bulk of the surface. Using experimentally retrieved magnesite growth rate laws and published forsterite (Mg2SiO4) dissolution rate law, we performed simple numerical simulations to estimate the overall influence of the investigated ligands on the carbonation rates of forsterite. We observe that all ligands will clearly be detrimental to forsterite carbonation rates in typical conditions foreseen for Mg-silicates mineral carbonation. Their use may be positive for the carbonation of less reactive Mg-silicate minerals, but the delayed formation of

  14. Ligand Identification Scoring Algorithm (LISA)

    PubMed Central

    Zheng, Zheng; Merz, Kenneth M.

    2011-01-01

    A central problem in de novo drug design is determining the binding affinity of a ligand with a receptor. A new scoring algorithm is presented that estimates the binding affinity of a protein-ligand complex given a three-dimensional structure. The method, LISA (Ligand Identification Scoring Algorithm), uses an empirical scoring function to describe the binding free energy. Interaction terms have been designed to account for van der Waals (VDW) contacts, hydrogen bonding, desolvation effects and metal chelation to model the dissociation equilibrium constants using a linear model. Atom types have been introduced to differentiate the parameters for VDW, H-bonding interactions and metal chelation between different atom pairs. A training set of 492 protein-ligand complexes was selected for the fitting process. Different test sets have been examined to evaluate its ability to predict experimentally measured binding affinities. By comparing with other well known scoring functions, the results show that LISA has advantages over many existing scoring functions in simulating protein-ligand binding affinity, especially metalloprotein-ligand binding affinity. Artificial Neural Network (ANN) was also used in order to demonstrate that the energy terms in LISA are well designed and do not require extra cross terms. PMID:21561101

  15. Investigation on Microbial Dissolution of Uranium (VI) from Autunite Mineral - 13421

    SciTech Connect

    Sepulveda, Paola; Katsenovich, Yelena; Lagos, Leonel

    2013-07-01

    Precipitating autunite minerals by polyphosphate injection was identified as a feasible remediation strategy for sequestering uranium in contaminated groundwater and soil in situ at the Hanford Site. Autunite stability under vadose and saturated zone environmental conditions can help to determine the long-term effectiveness of this remediation strategy. The Arthrobacter bacteria are one of the most common groups in soils and are found in large numbers in Hanford soil as well as other subsurface environments contaminated with radionuclides. Ubiquitous in subsurface microbial communities, these bacteria can play a significant role in the dissolution of minerals and the formation of secondary minerals. The main objective of this investigation was to study the bacterial interactions under oxidizing conditions with uranium (VI); study the potential role of bicarbonate, which is an integral complexing ligand for U(VI) and a major ion in groundwater compositions; and present data from autunite dissolution experiments using Arthrobacter strain G968, a less U(VI)-tolerant strain. Sterile 100 mL glass mixed reactors served as the major bioreactor for initial experimentation. These autunite-containing bioreactors were injected with bacterial cells after the autunite equilibrated with the media solution amended with 0 mM, 3 mM 5 mM and 10 mM concentrations of bicarbonate. G968 Arthrobacter cells in the amount of 10{sup 6} cells/mL were injected into the reactors after 27 days, giving time for the autunite to reach steady state. Abiotic non-carbonate controls were kept without bacterial inoculation to provide a control for the biotic samples. Samples of the solution were analyzed for dissolved U(VI) by means of kinetic phosphorescence analyzer KPA-11 (Chemcheck Instruments, Richland, WA). Analysis showed that as [HCO{sub 3}{sup -}] increases, a diminishing trend on the effect of bacteria on autunite leaching is observed. Viability of cells was conducted after 24 hours of cell

  16. NKG2D ligands mediate immunosurveillance of senescent cells

    PubMed Central

    Moshayev, Zhana; Vadai, Ezra; Wensveen, Felix; Ben-Dor, Shifra; Golani, Ofra; Polic, Bojan; Krizhanovsky, Valery

    2016-01-01

    Cellular senescence is a stress response mechanism that limits tumorigenesis and tissue damage. Induction of cellular senescence commonly coincides with an immunogenic phenotype that promotes self-elimination by components of the immune system, thereby facilitating tumor suppression and limiting excess fibrosis during wound repair. The mechanisms by which senescent cells regulate their immune surveillance are not completely understood. Here we show that ligands of an activating Natural Killer (NK) cell receptor (NKG2D), MICA and ULBP2 are consistently up-regulated following induction of replicative senescence, oncogene-induced senescence and DNA damage - induced senescence. MICA and ULBP2 proteins are necessary for efficient NK-mediated cytotoxicity towards senescent fibroblasts. The mechanisms regulating the initial expression of NKG2D ligands in senescent cells are dependent on a DNA damage response, whilst continuous expression of these ligands is regulated by the ERK signaling pathway. In liver fibrosis, the accumulation of senescent activated stellate cells is increased in mice lacking NKG2D receptor leading to increased fibrosis. Overall, our results provide new insights into the mechanisms regulating the expression of immune ligands in senescent cells and reveal the importance of NKG2D receptor-ligand interaction in protecting against liver fibrosis. PMID:26878797

  17. NKG2D ligands mediate immunosurveillance of senescent cells.

    PubMed

    Sagiv, Adi; Burton, Dominick G A; Moshayev, Zhana; Vadai, Ezra; Wensveen, Felix; Ben-Dor, Shifra; Golani, Ofra; Polic, Bojan; Krizhanovsky, Valery

    2016-02-01

    Cellular senescence is a stress response mechanism that limits tumorigenesis and tissue damage. Induction of cellular senescence commonly coincides with an immunogenic phenotype that promotes self-elimination by components of the immune system, thereby facilitating tumor suppression and limiting excess fibrosis during wound repair. The mechanisms by which senescent cells regulate their immune surveillance are not completely understood. Here we show that ligands of an activating Natural Killer (NK) cell receptor (NKG2D), MICA and ULBP2 are consistently up-regulated following induction of replicative senescence, oncogene-induced senescence and DNA damage - induced senescence. MICA and ULBP2 proteins are necessary for efficient NK-mediated cytotoxicity towards senescent fibroblasts. The mechanisms regulating the initial expression of NKG2D ligands in senescent cells are dependent on a DNA damage response, whilst continuous expression of these ligands is regulated by the ERK signaling pathway. In liver fibrosis, the accumulation of senescent activated stellate cells is increased in mice lacking NKG2D receptor leading to increased fibrosis. Overall, our results provide new insights into the mechanisms regulating the expression of immune ligands in senescent cells and reveal the importance of NKG2D receptor-ligand interaction in protecting against liver fibrosis. PMID:26878797

  18. Sticky physics of joy: on the dissolution of spherical candies

    NASA Astrophysics Data System (ADS)

    Windisch, Andreas; Windisch, Herbert; Windisch, Anita

    2013-03-01

    Assuming a constant mass decrease per unit surface and unit time we provide a very simplistic model for the dissolution process of spherical candies. The aim is to investigate the quantitative behaviour of the dissolution process throughout the act of eating the candy. In our model we do not take any microscopic mechanism of the dissolution process into account, but rather provide an estimate which is based on easy-to-follow calculations. Having obtained a description based on this calculation, we confirm the assumed behaviour by providing experimental data for the dissolution process. Besides a deviation from our prediction caused by the production process of the candies below a diameter of 2 mm, we find good agreement with our model-based expectations. Delicate questions on the optimal strategy for enjoying a candy will be addressed, such as whether it is wise to split the candy by breaking it with the teeth or not.

  19. 21 CFR 343.90 - Dissolution and drug release testing.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...) Aspirin, alumina, and magnesium oxide tablets. Aspirin in combination with alumina, and magnesium oxide in a tablet dosage form must meet the dissolution standard for aspirin, alumina, and magnesium...

  20. Dissolution rates of uranium compounds in simulated lung fluid.

    PubMed

    Kalkwarf, D R

    1983-06-01

    Maximum dissolution rates of uranium into simulated lung fluid were measured at 37 degrees C to estimate clearance rates from the deep lung. The materials tested included: ore and yellowcake, an airborne sample from an industrial site, and purified samples of (NH4)2U2O7, U3O8, UO2 and UF4. A batch procedure was developed to test samples containing as little as 10 micrograms of natural uranium. Values of dissolution halftimes varied from 0.01 day to several thousand days depending on the physical and chemical form of the uranium. Dissolution occurred predominantly by formation of the #UO2(CO3)3 ]4-ion; and as a result, tetravalent uranium compounds dissolved slowly. Dissolution rates of size-separated yellowcake aerosols were found to be more closely correlated with specific surface area than with aerodynamic diameter. PMID:6879160

  1. Dissolution kinetics of calcium carbonate in equatorial Pacific sediments

    SciTech Connect

    Berelson, W.M.; Hammond, D.E.; McManus, J.; Kilgore, T.E. )

    1994-06-01

    Calcium carbonate dissolution exerts a major influence on the carbonate chemistry of seawater and is an important factor in regulating atmospheric CO2 concentration. The authors use a numerical model, based on an estimate of k determined from benthic chamber flux measurements, the distribution of CO3 2-in the water column and percent of CaCO3 in the sediments, to derive the total alkalinity flux from Pacific Ocean sediments. The significance of this budget is discussed as are the following questions: what is the rate of calcium carbonate dissolution on the deep sea floor what controls carbonate dissolution, organic carbon rain rates, or bottom water carbonate ion concentration what is the equations that relates carbonate dissolution to degree of undersaturation and what is the associate rate constant 43 refs., 10 figs., 4 tabs.

  2. 21 CFR 343.90 - Dissolution and drug release testing.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...) Aspirin, alumina, and magnesium oxide tablets. Aspirin in combination with alumina, and magnesium oxide in a tablet dosage form must meet the dissolution standard for aspirin, alumina, and magnesium...

  3. 21 CFR 343.90 - Dissolution and drug release testing.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...) Aspirin, alumina, and magnesium oxide tablets. Aspirin in combination with alumina, and magnesium oxide in a tablet dosage form must meet the dissolution standard for aspirin, alumina, and magnesium...

  4. 21 CFR 343.90 - Dissolution and drug release testing.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...) Aspirin, alumina, and magnesium oxide tablets. Aspirin in combination with alumina, and magnesium oxide in a tablet dosage form must meet the dissolution standard for aspirin, alumina, and magnesium...

  5. In vivo dissolution measurement with indium-111 summation peak ratios

    SciTech Connect

    Jay, M.; Woodward, M.A.; Brouwer, K.R.

    1985-10-01

    Dissolution of (/sup 111/In)labeled tablets was measured in vivo in a totally noninvasive manner by using a modification of the perturbed angular correlation technique known as the summation peak ratio method. This method, which requires the incorporation of only 10-12 microCi into the dosage form, provided reliable dissolution data after oral administration of (/sup 111/In)lactose tablets. These results were supported by in vitro experiments which demonstrated that the dissolution rate as measured by the summation peak ratio method was in close agreement with the dissolution rate of salicylic acid in a (/sup 111/In)salicylic acid tablet. The method has the advantages of using only one detector, thereby avoiding the need for complex coincidence counting systems, requiring less radioactivity, and being potentially applicable to a gamma camera imaging system.

  6. 10 CFR 960.4-2-6 - Dissolution.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... greater than those allowable under the requirements specified in § 960.4-1. In predicting the likelihood...,000 years after closure, active dissolution, as predicted on the basis of the geologic record,...

  7. Dissolution rates of carbonated hydroxyapatite in hydrochloric acid.

    PubMed

    Hankermeyer, Christine R; Ohashi, Kevin L; Delaney, David C; Ross, John; Constantz, Brent R

    2002-02-01

    Osteoclasts have been shown to dissolve efficiently and effectively the mineral phase of bone by locally controlling the environment surrounding the cell. Although this mineral phase has been identified and well characterized as carbonated hydroxyapatite, there is little understanding of the factors that affect the dissolution properties of this mineral phase. Mimicking the mechanism by which osteoclasts dissolve the mineral phase of bone may provide insight into methods for the decalcification of atherosclerotic mineral deposits in the vascular system. Accordingly, a detailed characterization of the effects of various chemical and mechanical parameters on the dissolution of carbonated hydroxyapatite mineral was investigated in this study. Increases in the mineral dissolution rate (2-10 times) were associated with increases in dissolving solution [H+], osmolality, temperature, and flow rate. Mineral dissolution rate increases (5-8 times) were associated with greater surface area of the mineral and mechanical agitation of the dissolving solution. PMID:11771694

  8. Modeling solid-state transformations occurring in dissolution testing.

    PubMed

    Laaksonen, Timo; Aaltonen, Jaakko

    2013-04-15

    Changes in the solid-state form can occur during dissolution testing of drugs. This can often complicate interpretation of results. Additionally, there can be several mechanisms through which such a change proceeds, e.g. solvent-mediated transformation or crystal growth within the drug material itself. Here, a mathematical model was constructed to study the dissolution testing of a material, which undergoes such changes. The model consisted of two processes: the recrystallization of the drug from a supersaturated liquid state caused by the dissolution of the more soluble solid form and the crystal growth of the stable solid form at the surface of the drug formulation. Comparison to experimental data on theophylline dissolution showed that the results obtained with the model matched real solid-state changes and that it was able to distinguish between cases where the transformation was controlled either by solvent-mediated crystallization or solid-state crystal growth. PMID:23506958

  9. Tank 12 Sludge Characterization and Aluminum Dissolution Demonstration

    SciTech Connect

    Reboul, S.; Hay, M.; Zeigler, K; Stone, M.

    2010-05-05

    A 3-L sludge slurry sample from Tank 12 was characterized and then processed through an aluminum dissolution demonstration. The dominant constituent of the sludge was found to be aluminum in the form of boehmite. The iron content was minor, about one-tenth that of the aluminum. The salt content of the supernatant was relatively high, with a sodium concentration of {approx}7 M. Due to these characteristics, the yield stress and plastic viscosity of the unprocessed slurry were relatively high (19 Pa and 27 cP), and the settling rate of the sludge was relatively low ({approx}20% settling over a two and a half week period). Prior to performing aluminum dissolution, plutonium and gadolinium were added to the slurry to simulate receipt of plutonium waste from H-Canyon. Aluminum dissolution was performed over a 26 day period at a temperature of 65 C. Approximately 60% of the insoluble aluminum dissolved during the demonstration, with the rate of dissolution slowing significantly by the end of the demonstration period. In contrast, approximately 20% of the plutonium and less than 1% of the gadolinium partitioned to the liquid phase. However, about a third of the liquid phase plutonium became solubilized prior to the dissolution period, when the H-Canyon plutonium/gadolinium simulant was added to the Tank 12 slurry. Quantification of iron dissolution was less clear, but appeared to be on the order of 1% based on the majority of data (a minor portion of the data suggested iron dissolution could be as high as 10%). The yield stress of the post-dissolution slurry (2.5 Pa) was an order of magnitude lower than the initial slurry, due most likely to the reduced insoluble solids content caused by aluminum dissolution. In contrast, the plastic viscosity remained unchanged (27 cP). The settling rate of the post-dissolution slurry was higher than the initial slurry, but still relatively low compared to settling of typical high iron content/low salt content sludges. Approximately 40

  10. TANK 12 SLUDGE CHARACTERIZATION AND ALUMINUM DISSOLUTION DEMONSTRATION

    SciTech Connect

    Reboul, S; Michael Hay, M; Kristine Zeigler, K; Michael Stone, M

    2009-03-25

    A 3-L sludge slurry sample from Tank 12 was characterized and then processed through an aluminum dissolution demonstration. The dominant constituent of the sludge was found to be aluminum in the form of boehmite. The iron content was minor, about one-tenth that of the aluminum. The salt content of the supernatant was relatively high, with a sodium concentration of {approx}7 M. Due to these characteristics, the yield stress and plastic viscosity of the unprocessed slurry were relatively high (19 Pa and 27 cP), and the settling rate of the sludge was relatively low ({approx}20% settling over a two and a half week period). Prior to performing aluminum dissolution, plutonium and gadolinium were added to the slurry to simulate receipt of plutonium waste from H-Canyon. Aluminum dissolution was performed over a 26 day period at a temperature of 65 C. Approximately 60% of the insoluble aluminum dissolved during the demonstration, with the rate of dissolution slowing significantly by the end of the demonstration period. In contrast, approximately 20% of the plutonium and less than 1% of the gadolinium partitioned to the liquid phase. However, about a third of the liquid phase plutonium became solubilized prior to the dissolution period, when the H-Canyon plutonium/gadolinium simulant was added to the Tank 12 slurry. Quantification of iron dissolution was less clear, but appeared to be on the order of 1% based on the majority of data (a minor portion of the data suggested iron dissolution could be as high as 10%). The yield stress of the post-dissolution slurry (2.5 Pa) was an order of magnitude lower than the initial slurry, due most likely to the reduced insoluble solids content caused by aluminum dissolution. In contrast, the plastic viscosity remained unchanged (27 cP). The settling rate of the post-dissolution slurry was higher than the initial slurry, but still relatively low compared to settling of typical high iron content/low salt content sludges. Approximately 40

  11. Two-phase convective CO2 dissolution in saline aquifers

    DOE PAGESBeta

    Martinez, M. J.; Hesse, M. A.

    2016-01-30

    Geologic carbon storage in deep saline aquifers is a promising technology for reducing anthropogenic emissions into the atmosphere. Dissolution of injected CO2 into resident brines is one of the primary trapping mechanisms generally considered necessary to provide long-term storage security. Given that diffusion of CO2 in brine is woefully slow, convective dissolution, driven by a small increase in brine density with CO2 saturation, is considered to be the primary mechanism of dissolution trapping. Previous studies of convective dissolution have typically only considered the convective process in the single-phase region below the capillary transition zone and have either ignored the overlyingmore » two-phase region where dissolution actually takes place or replaced it with a virtual region with reduced or enhanced constant permeability. Our objective is to improve estimates of the long-term dissolution flux of CO2 into brine by including the capillary transition zone in two-phase model simulations. In the fully two-phase model, there is a capillary transition zone above the brine-saturated region over which the brine saturation decreases with increasing elevation. Our two-phase simulations show that the dissolution flux obtained by assuming a brine-saturated, single-phase porous region with a closed upper boundary is recovered in the limit of vanishing entry pressure and capillary transition zone. For typical finite entry pressures and capillary transition zone, however, convection currents penetrate into the two-phase region. As a result, this removes the mass transfer limitation of the diffusive boundary layer and enhances the convective dissolution flux of CO2 more than 3 times above the rate assuming single-phase conditions.« less

  12. Two-phase convective CO2 dissolution in saline aquifers

    DOE PAGESBeta

    Martinez, Mario J.; Hesse, Marc A.

    2016-01-01

    Geologic carbon storage in deep saline aquifers is a promising technology for reducing anthropogenic emissions into the atmosphere. Dissolution of injected CO2 into resident brines is one of the primary trapping mechanisms generally considered necessary to provide long-term storage security. Given that diffusion of CO2 in brine is woefully slow, convective dissolution, driven by a small increase in brine density with CO2 saturation, is considered to be the primary mechanism of dissolution trapping. Previous studies of convective dissolution have typically only considered the convective process in the single-phase region below the capillary transition zone and have either ignored the overlyingmore » two-phase region where dissolution actually takes place or replaced it with a virtual region with reduced or enhanced constant permeability. Our objective is to improve estimates of the long-term dissolution flux of CO2 into brine by including the capillary transition zone in two-phase model simulations. In the fully two-phase model, there is a capillary transition zone above the brine-saturated region over which the brine saturation decreases with increasing elevation. Our two-phase simulations show that the dissolution flux obtained by assuming a brine-saturated, single-phase porous region with a closed upper boundary is recovered in the limit of vanishing entry pressure and capillary transition zone. For typical finite entry pressures and capillary transition zone, however, convection currents penetrate into the two-phase region. As a result, this removes the mass transfer limitation of the diffusive boundary layer and enhances the convective dissolution flux of CO2 more than 3 times above the rate assuming single-phase conditions.« less

  13. The effect of fuel chemistry on UO2 dissolution

    NASA Astrophysics Data System (ADS)

    Casella, Amanda; Hanson, Brady; Miller, William

    2016-08-01

    The dissolution rate of both unirradiated UO2 and used nuclear fuel has been studied by numerous countries as part of the performance assessment of proposed geologic repositories. In the scenario of waste package failure and groundwater contact with the fuel, the effects of variables such as temperature, dissolved oxygen, and water and fuel chemistry on the dissolution rates of the fuel are necessary to provide a quantitative estimate of the potential release over geologic time frames. The primary objective of this research was to determine the influence these parameters, with primary focus on the fuel chemistry, have on the dissolution rate of unirradiated UO2 under oxidizing repository conditions and compare them to the rates predicted by current dissolution models. Both unirradiated UO2 and UO2 doped with varying concentrations of Gd2O3, to simulate used fuel composition after long time periods when radiolysis has minor contributions to dissolution, were examined. In general, a rise in temperature increased the dissolution rate of UO2 and had a larger effect on pure UO2 than on those doped with Gd2O3. Oxygen dependence was observed in the UO2 samples with no dopant and increased as the temperature rose; in the doped fuels less dependence was observed. The addition of gadolinia into the UO2 matrix resulted in a significant decrease in the dissolution rate. The matrix stabilization effect resulting from the dopant proved even more beneficial in lowering the dissolution rate at higher temperatures and dissolved O2 concentrations in the leachate where the rates would typically be elevated.

  14. Dissolution of olivine in basaltic liquids: experimental observations and applications.

    USGS Publications Warehouse

    Thornber, C.R.; Huebner, J.S.

    1985-01-01

    Rates of olivine dissolution in synthetic lunar basalt 77115 and a silica-enriched 77115 composition (Sil-77115) at superliquidus temperatures have been determined. Dissolution-rate data have been applied to the problem of the thermal history of fragment-laden impact-melt rocks of the lunar highlands. Textural and chemical criteria are discussed for the recognition of olivine resorption (and growth) phenomena in igneous rocks. -J.A.Z.

  15. Experimental results: Pilot plant calcine dissolution and liquid feed stability

    SciTech Connect

    Herbst, R.S.; Fryer, D.S.; Brewer, K.N.; Johnson, C.K.; Todd, T.A.

    1995-02-01

    The dissolution of simulated Idaho Chemical Processing Plant pilot plant calcines, containing none of the radioactive actinides, lanthanides or fission products, was examined to evaluate the solubility of calcine matrix materials in acidic media. This study was a necessary precursor to dissolution and optimization experiments with actual radionuclide-containing calcines. The importance of temperature, nitric acid concentration, ratio of acid volume to calcine mass, and time on the amount, as a weight percentage of calcine dissolved, was evaluated. These parameters were studied for several representative pilot plant calcine types: (1) Run No. 74 Zirconia calcine; (2) Run No. 17 Zirconia/Sodium calcine; (3) Run No. 64 Zirconia/Sodium calcine; (3) Run No. 1027 Alumina calcine; and (4) Run No. 20 Alumina/Zirconia/Sodium calcine. Statistically designed experiments with the different pilot plant calcines indicated the effect of the studied process variables on the amount of calcine dissolved decreases in the order: Acid/Calcine Ratio > Temperature > HNO{sub 3} Concentration > Dissolution Time. The following conditions are suitable to achieve greater than 90 wt. % dissolution of most Zr, Al, or Na blend calcines: (1) Maximum nitric acid concentration of 5M; (2) Minimum acid/calcine ratio of 10 mL acid/1 gram calcine; (3) Minimum dissolution temperature of 90{degrees}C; and (4) Minimum dissolution time of 30 minutes. The formation of calcium sulphate (CaSO{sub 4}) precipitates was observed in certain dissolved calcine solutions during the dissolution experiments. Consequently, a study was initiated to evaluate if and under what conditions the resulting dissolved calcine solutions would be unstable with regards to precipitate formation. The results indicate that precipitate formation in the calcine solutions prepared under the above proposed dissolution conditions are not anticipated.

  16. Dissolution kinetics of high-resolution novolac resists

    NASA Astrophysics Data System (ADS)

    Itoh, Katsuyuki; Yamanaka, Koji; Nozue, Hiroshi; Kasama, Kunihiko

    1991-06-01

    Dissolution kinetics, as well as the formation mechanism of a surface insoluble layer produced by dipping into TMAH (tetramethylammonium hydroxide) developer, have been investigated. In the previous paper, we mentioned that dissolution rate characteristics of high resolution novolac resist are clearly divided into three regions. To investigate this dissolution mechanism, we evaluated the temperature dependence of R (Dissolution rate) by changing the exposure dose, PAC (photoactive compound equals dissolution inhibitor) and the TMAH concentration. From Arrhenius Plots of these resist systems, it is considered that R is determined by two competitive reactions in the presence of TMAH; i.e., (a) the complex formation between PAC and novolac resin which produces dissolution inhibition effect, (b) TMAH induced deprotonation of phenolic hydroxy groups in novolac resin which accelerates the dissolution of the resist. Furthermore, we also describe the formation mechanism of a surface insoluble layer produced by dipping into a TMAH developer followed by water rinse, on the basis of the dissolution time of this layer (ts). The resist surface was also analyzed by using FT-IR (Fourier transform infrared spectroscopic measurement) and XPS (X-ray photoelectron spectroscopy). As a result, it was found that (a) water rinse is essential for the surface insoluble layer formation, (b) the ts value is not directly correlated with PAC accumulation in the resist surface and (c) the ts value becomes longer when the amount of penetrated TMAH into the resist increases. These results suggest that the surface insoluble layer is produced via water rinse of PAC-novolac complex described above.

  17. Two-phase convective CO2 dissolution in saline aquifers

    NASA Astrophysics Data System (ADS)

    Martinez, M. J.; Hesse, M. A.

    2016-01-01

    Geologic carbon storage in deep saline aquifers is a promising technology for reducing anthropogenic emissions into the atmosphere. Dissolution of injected CO2 into resident brines is one of the primary trapping mechanisms generally considered necessary to provide long-term storage security. Given that diffusion of CO2 in brine is woefully slow, convective dissolution, driven by a small increase in brine density with CO2 saturation, is considered to be the primary mechanism of dissolution trapping. Previous studies of convective dissolution have typically only considered the convective process in the single-phase region below the capillary transition zone and have either ignored the overlying two-phase region where dissolution actually takes place or replaced it with a virtual region with reduced or enhanced constant permeability. Our objective is to improve estimates of the long-term dissolution flux of CO2 into brine by including the capillary transition zone in two-phase model simulations. In the fully two-phase model, there is a capillary transition zone above the brine-saturated region over which the brine saturation decreases with increasing elevation. Our two-phase simulations show that the dissolution flux obtained by assuming a brine-saturated, single-phase porous region with a closed upper boundary is recovered in the limit of vanishing entry pressure and capillary transition zone. For typical finite entry pressures and capillary transition zone, however, convection currents penetrate into the two-phase region. This removes the mass transfer limitation of the diffusive boundary layer and enhances the convective dissolution flux of CO2 more than 3 times above the rate assuming single-phase conditions.

  18. Dissolution-passivation model for zirconium alloys in fluorinated media

    SciTech Connect

    Prono, J.; Caprani, A.; Jaszay, T.; Frayret, J.P.

    1992-12-31

    Considering the shape of the steady state current-potential curve, we proposed a dissolution-passivation model composed of five determining steps and we calculated the associated elementary rates. Two different compounds of tetravalent zirconium are involved in the formation of the surface film. The influence of temperature on the elementary rates allows us to consider the chemical dissolution as the slowest steps and to involve fluoride in the formation of the film in the vicinity of the corrosion potential.

  19. Mesoporous silica sub-micron spheres as drug dissolution enhancers: Influence of drug and matrix chemistry on functionality and stability.

    PubMed

    Brigo, Laura; Scomparin, Elisa; Galuppo, Marco; Capurso, Giovanni; Ferlin, Maria Grazia; Bello, Valentina; Realdon, Nicola; Brusatin, Giovanna; Morpurgo, Margherita

    2016-02-01

    Mesoporous silica particles prepared through a simplified Stöber method and low temperature solvent promoted surfactant removal are evaluated as dissolution enhancers for poorly soluble compounds, using a powerful anticancer agent belonging to pyrroloquinolinones as a model for anticancer oral therapy, and anti-inflammatory ibuprofen as a reference compound. Mesoporous powders composed of either pure silica or silica modified with aminopropyl residues are produced. The influence of material composition and drug chemical properties on drug loading capability and dissolution enhancement are studied. The two types of particles display similar size, surface area, porosity, erodibility, drug loading capability and stability. An up to 50% w/w drug loading is reached, showing correlation between drug concentration in adsorption medium and content in the final powder. Upon immersion in simulating body fluids, immediate drug dissolution occurred, allowing acceptor solutions to reach concentrations equal to or greater than drug saturation limits. The matrix composition influenced drug solution maximal concentration, complementing the dissolution enhancement generated by a mesoporous structure. This effect was found to depend on both matrix and drug chemical properties allowing us to hypothesise general prediction behaviour rules. PMID:26652411

  20. Enhancement of Dissolution Rate of Indomethacin: Using Liquisolid Compacts

    PubMed Central

    Saeedi, Majid; Akbari, Jafar; Morteza-Semnani, Katayoun; Enayati-Fard, Reza; Sar-Reshteh-dar, Shirin; Soleymani, Ala

    2011-01-01

    The potential of liquisolid systems to improve the dissolution properties of a water-insoluble agent (indomethacin) was the purpose of this survey. In this study, different formulations of liquisolid tablets using different co-solvents (non-volatile solvents) were prepared and the effect of several amounts of them on the dissolution behaviour of indomethacin was investigated. It is worth mentioning that the ratio of microcrystalline cellulose (carrier) to silica (coating powder material) was 20 in all formulations. To evaluate any interaction between indomethacin and the other components in liquisolid formulations, the differential scanning calorimeter (DSC) was used. The results showed that the liquisolid formulations exhibited significantly higher drug dissolution rates in comparison with directly compressed tablet. The enhanced rate of indomethacin dissolution derived from liquisolid tablets was probably due to an increase in wetting properties and surface area of drug particles available for dissolution. Moreover, it was indicated that the fraction of molecularly dispersed drug (FM) in the liquid medication of liquisolid systems was directly proportional to their indomethacin dissolution rate (DR). An attempt was made to correlate the percentage drug dissolved in 10 min with the solubility of indomethacin in PEG 200 and glycerin. In conclusion, the liquisolid compacts technique can be a promising alternative for the formulation of water insoluble drugs, such as indomethacin into rapid release tablets. PMID:24363677

  1. In situ calcium carbonate dissolution in the Pacific Ocean

    SciTech Connect

    Feely, R. A.; Sabine, Chris; Lee, K.; Millero, F. J.; Lamb, M. F.; Greeley, D.; Bullister, J.L.; Key, Robert; Peng, T.-H.; Kozyr, Alexander; Ono, Tsueno

    2002-01-01

    Over the past several years researchers have been working to synthesize the WOCE/ JGOFS global CO2 survey data to better understand carbon cycling processes in the oceans. The Pacific Ocean data set has over 35,000 sample locations with at least two carbon parameters, oxygen, nutrients, CFC tracers, and hydrographic parameters. In this paper we estimate the in situ CaCO3 dissolution rates in the Pacific Ocean water column. Calcium carbonate dissolution rates ranging from 0.01 1.1 mmol kg1 yr1 are observed in intermediate and deepwater beginning near the aragonite saturation horizon. In the North Pacific Intermediate Water between 400 and 800 m, CaCO3 dissolution rates are more than 7 times faster than observed in middle and deep water depths (average = 0.051 mmol kg1 yr1). The total amount of CaCO3 that is dissolved within the Pacific is determined by integrating excess alkalinity throughout the water column. The total inventory of CaCO3 added by particle dissolution in the Pacific Ocean, north of 40S, is 157 Pg C. This amounts to an average dissolution rate of approximately 0.31 Pg C yr1. This estimate is approximately 74% of the export production of CaCO3 estimated for the Pacific Ocean. These estimates should be considered to be upper limits for in situ carbonate dissolution in the Pacific Ocean, since a portion of the alkalinity increase results from inputs from sediments.

  2. Oxidative dissolution of silver nanoparticles: A new theoretical approach.

    PubMed

    Adamczyk, Zbigniew; Oćwieja, Magdalena; Mrowiec, Halina; Walas, Stanisław; Lupa, Dawid

    2016-05-01

    A general model of an oxidative dissolution of silver particle suspensions was developed that rigorously considers the bulk and surface solute transport. A two-step surface reaction scheme was proposed that comprises the formation of the silver oxide phase by direct oxidation and the acidic dissolution of this phase leading to silver ion release. By considering this, a complete set of equations is formulated describing oxygen and silver ion transport to and from particles' surfaces. These equations are solved in some limiting cases of nanoparticle dissolution in dilute suspensions. The obtained kinetic equations were used for the interpretation of experimental data pertinent to the dissolution kinetics of citrate-stabilized silver nanoparticles. In these kinetic measurements the role of pH and bulk suspension concentration was quantitatively evaluated by using the atomic absorption spectrometry (AAS). It was shown that the theoretical model adequately reflects the main features of the experimental results, especially the significant increase in the dissolution rate for lower pH. Also the presence of two kinetic regimes was quantitatively explained in terms of the decrease in the coverage of the fast dissolving oxide layer. The overall silver dissolution rate constants characterizing these two regimes were determined. PMID:26921758

  3. Enhanced CO2 Dissolution in Heterogeneous Porous Media

    NASA Astrophysics Data System (ADS)

    Daniels, K.; Neufeld, J. A.; Bickle, M. J.; Hallworth, M. A.

    2014-12-01

    Long-term and secure geological storage of CO2 through technologies such as Carbon Capture and Storage (CCS) within reservoirs is seen as a technological means to reduce anthropogenic CO2 emissions. The long-term viability of this technology is reliant on the structural and secondary trapping of supercritical CO2 within heterogeneous reservoirs. Secondary trapping, primarily through the dissolution of CO2 into ambient reservoir brine to produce a denser fluid, is capable of retaining CO2 in the subsurface and thus reducing the risks of storage. To model secondary trapping we need to understand how the flow of CO2 through heterogeneous reservoir rocks enhances dissolution of supercritical CO2 in reservoir brines. Here we experimentally investigate the dissolution of CO2 in reservoir brines in layered, heterogeneous geological formations. Using analogue experiments, designed to approximate an enhanced oil recovery (EOR) setting, the processes of mixing, dispersion and dissolution are examined. These are compared against test results from non-layered, homogeneous porous media experiments. We find that heterogeneities significantly enhance mixing, particularly between adjacent porous layers. During fluid propagation, pore-scale viscous fingers grow and retreat, thereby providing an increased surface area between the flow and the ambient reservoir fluid. This enhanced mixing is predicted to substantially increase the dissolution of CO2 in reservoir brines. Both permeability and viscosity differences are found to have a significant effect on the interface between the two fluids, and therefore the likely amount of dissolution of CO2.

  4. Observations of magnetite dissolution in poorly drained soils

    USGS Publications Warehouse

    Grimley, D.A.; Arruda, N.K.

    2007-01-01

    Dissolution of strongly magnetic minerals is a common and relatively rapid phenomenon in poorly drained soils of the central United States, resulting in low magnetic susceptibility (MS). Low Eh reducing conditions are primarily responsible for magnetic mineral dissolution; a process likely mediated by iron-reducing bacteria in the presence of soil organic matter. Based on transects across drainage sequences from nine sites, natural magnetic minerals (>5 ??m) extracted from surface soil consist of 54% ?? 18% magnetite, 21% ?? 11% titanomagnetite, and 17% ?? 14% ilmenite. Magnetite and titanomagnetite dissolution, assessed by scanning electron microscopy on a 0-to-3 scale, inversely correlates with surface soil MS (r = 0.53), a proxy for soil drainage at studied transects. Altered magnetite typically displays etch pits 5 ??m) include 26% ?? 18% anthropogenic fly ash that also exhibits greater dissolution in low MS soils (r = 0.38), indicating detectable alteration can occur within 150 years in low Eh soils. Laboratory induced reduction of magnetite, titanomagnetite, and magnetic fly ash, with a citrate-bicarbonate- dithionite solution, resulted in dissolution textures similar to those of in situ soil particles. Although experiments indicate that reductive dissolution of magnetite can occur abiotically under extreme conditions, bacteria likely play an important role in the natural environment. ?? 2007 Lippincott Williams & Wilkins, Inc.

  5. Boehmite Dissolution Studies Supporting High Level Waste Pretreatment - 9383

    SciTech Connect

    Peterson, Reid A.; Russell, Renee L.; Snow, Lanee A.

    2009-03-01

    Boehmite is present in significant quantities in several of the Hanford waste tanks. It has been proposed that the boehmite will be dissolved through caustic leaching in the Hanford Waste Treatment Plant currently under construction. Therefore, it is important to fully understand the nature of this dissolution so that the process can be deployed. This research determined the impact of primary control parameters on the boehmite dissolution rate. The impact of aluminate ion on the dissolution kinetics was determined. In addition, other parameters that impact boehmite dissolution, such as free hydroxide concentration and reaction temperature, were also assessed and used to develop a semi-empirical model of the boehmite dissolution process. The understanding derived from this work will be used as the basis to evaluate and improve the planned performance of the Hanford Waste Treatment plant. This work is the first in a series of programs aimed at demonstrating the Waste Treatment Plant dissolution process. This work will be used to develop a simulant of the boehmite-containing Hanford waste. That simulant will then be used in laboratory- and pilot-scale testing to demonstrate the Waste Treatment Plant pretreatment process in an integrated fashion.

  6. Ibuprofen-phospholipid solid dispersions: improved dissolution and gastric tolerance.

    PubMed

    Hussain, M Delwar; Saxena, Vipin; Brausch, James F; Talukder, Rahmat M

    2012-01-17

    Solid dispersions of ibuprofen with various phospholipids were prepared, and the effect of phospholipids on the in vitro dissolution and in vivo gastrointestinal toxicity of ibuprofen was evaluated. Most phospholipids improved the dissolution of ibuprofen; dimyristoylphosphatidyl-glycerol (DMPG) had the greatest effect. At 45 min, the extent of dissolution of ibuprofen from the ibuprofen-DMPG system (weight ratio 9:1) increased about 69% compared to ibuprofen alone; the initial rate of dissolution increased sevenfold. Increasing the DMPG content from 9:1 to 4:1 in this system did not significantly increase the rate and the extent of dissolution. X-ray diffraction and scanning electron micrograph indicated a smaller crystallite size of ibuprofen with fairly uniform distribution in the ibuprofen-DMPG solid dispersion. A small amount of carrier phospholipid significantly increases the rate and the extent of dissolution, which may increase the bioavailability of ibuprofen. The number of ulcers >0.5mm in size formed in the gastric mucosa of rats following ibuprofen, DMPG, DMPC and DPPC solid dispersions (ibuprofen and phospholipid weight ratio 4:1) were 8.6 ± 6.2, 3.9 ± 5.3, 5.3 ± 4.9 and 9.1 ± 7.4, respectively. Solid dispersion of ibuprofen with DMPG was significantly less irritating to the gastric mucosa than ibuprofen itself (one-way ANOVA, p<0.05). Solid dispersion of ibuprofen and DMPG decreases the gastric side effects of ibuprofen. PMID:22101290

  7. Miniaturization of powder dissolution measurement and estimation of particle size.

    PubMed

    Avdeef, Alex; Tsinman, Konstantin; Tsinman, Oksana; Sun, Na; Voloboy, Dmytro

    2009-11-01

    The objective was to investigate the applicability and limitations of an approach for estimating particle size from powder dissolution measurement using as little as 50 microg of sample in 1 ml of buffer solutions. The powder dissolution profiles of five sparingly-soluble drugs (hydrochlorothiazide, phenazopyridine hydrochloride, 2-naphthoic acid, indomethacin, and dipyridamole) were evaluated with a novel biexponential spherical particle equation and also the Wang-Flanagan spherical particle non-sink equation. The results were compared to particle sizing based on measured specific surface area by the Brunauer-Emmett-Teller (BET) method, and also based on Coulter counting. With the exception of hydrochlorothiazide, the model compounds indicated some agglomeration in the dissolution media. The dry-state specific surface area was larger than expected from either the Coulter method or the powder-dissolution data, especially for phenazopyridine hydrochloride. The particle radii estimated by the powder dissolution method ranged from 10 to 68 microm, with equilibrium solubilities spanning from 5 microg/ml (dipyridamole) to 911 microg/ml (hydrochlorothiazide). Powder dissolution data collected with the miniaturized apparatus can be used to determine particle size, with estimated values agreeing reasonably with those measured by the Coulter counter method. PMID:19937817

  8. Anodic dissolution of nickel in acidic chloride solutions

    NASA Astrophysics Data System (ADS)

    El Aal, E. E. Abd; Zakria, W.; Diab, A.; El Haleem, S. M. Abd

    2003-04-01

    The anodic dissolution of nickel was studied galvanostatically in hydrochloric acid solutions of various concentrations. The reaction orders of chloride ion and hydrogen ion concentrations were found to be 0.5 and 1.0, respectively. An anodic Tafel slope equal to 120 ± 10 mV · decade-1 was obtained. The dissolution rate of nickel at constant acid concentration was increased with stirring of the solution and increasing temperature. The activation energy, ΔH, for the anodic dissolution process was found to be 12 kcal · mol-1. The presence of oxygen in solutions assisted the passivation process. The effect of addition of aniline and some of its derivatives (o-, m-, and p-anisidine) as inhibitors on the dissolution kinetics of Ni in 1 M HCl was also investigated. These compounds inhibited the anodic dissolution of nickel without affecting the Tafel slope, indicating that the adsorption of such inhibitors could not interfere with the mechanism of metal dissolution.

  9. The Effects of Freshwater Dissolution on Coral Geochemistry and Morphology

    NASA Astrophysics Data System (ADS)

    Wiggins, E. B.; Cobb, K. M.; Sayani, H. R.

    2012-12-01

    The aragonite skeletons of massive reef-building corals provide an invaluable high-resolution archive of past climate variability. However, studies have repeatedly shown that alteration of the coral skeleton (diagenesis), occurring as secondary cements and/or dissolution, is fairly prevalent among both modern and fossil corals. While the effects of secondary cements on bulk coral geochemistry and morphology have been extensively documented, the impacts of dissolution remain relatively unconstrained. Given that aragonite is metastable and that most fossil corals are exposed to rainfall for long periods, it follows that dissolution-related artifacts in fossil coral paleoclimate records merit further study. To date, the only study on coral dissolution suggests that dissolution does not significantly impact the oxygen isotopic ratios (δ18O), but leads to an increase of up to +0.06mmol/mol in coral Sr/Ca (equivalent to sea-surface temperature (SST) cooling artifacts of -1.2°C using standard Sr/Ca paleo-temperature conversions) [Hendy et.al., 2007]. Here we investigate the effects of freshwater dissolution on coral geochemistry and morphology by exposing a 2.5cm x 5cm segment of a modern coral from Palmyra Island (6°N, 162°W) to a constant freshwater drip for one week in order to simulate the effects of rainfall. Scanning electron microscope (SEM) images and coral δ18O and Sr/Ca measurements were taken before and after the coral was dissolved to assess the impacts of dissolution. We observe that dissolution occurs both on the surface and within the coral skeleton. Surface coral dissolution results in a "bumpy" surface, while interior dissolution targets centers of calcification. In the heavily-dissolved portions of the coral, nearly 60% of the skeleton surface is dissolved. In these areas δ18O shows a significant decrease of -0.2-0.4‰, which would correspond to an SST increase of +1-2°C in paleotemperature [Epstein, 1953]. Due to the relatively large range of Sr

  10. Glass fiber dissolution in simulated lung fluid and measures needed to improve consistency and correspondence to in vivo dissolution.

    PubMed Central

    Mattson, S M

    1994-01-01

    The dissolution of a range of glass fibers including commercial glass and mineral wools has been studied using a modification of Gamble's solution in a flow system at pH 7.4 and 37 degrees C. Dissolution has been followed by weight loss, effluent analysis, and morphology change of fibers and bulk glass. Flow per glass surface area can strongly affect both dissolution rate and morphology due to the effect of the dissolution process on the fluid. Effluent pH is shown to be a guide for choice of optimum flow/area conditions. These conditions provide measurable concentrations of dissolved glass in the effluent while maintaining their concentrations below the point at which they significantly affect the dissolution process. SiO2 and Al2O3 vary widely in the extent to which they are involved in the leaching process, which removes alkalis, alkaline earths, and B2O3. This makes analysis of a single component in the effluent unsuitable as a means of comparing the dissolution rates of a wide range of compositions. PMID:7882963

  11. Development and evaluation of methods for starch dissolution using asymmetrical flow field-flow fractionation. Part II: Dissolution of amylose.

    PubMed

    Perez-Rea, Daysi; Bergenståhl, Björn; Nilsson, Lars

    2016-02-01

    In this paper, we investigate whether dissolution in water under autoclaving conditions (140 °C, 20 min) or in dimethyl sulfoxide, DMSO (100 °C, 1 h), is preferable for characterization of amylose. Two types of amylose, potato and maize, were dissolved either in water using an autoclave or in DMSO. On the aqueous solutions obtained, the extent of molecular dissolution of the sample (referred to as the dissolution yield) was determined by enzymatic analysis as well as the molecular properties, such as molar mass and root-mean-square radius, obtained with asymmetrical flow field-flow fractionation coupled to multi-angle light scattering and differential refractive index detection (AF4-MALS-dRI). The results showed that both dissolution methods are efficient at dissolving amylose. However, AF4-MALS-dRI analysis revealed substantial differences. Amylose aqueous solutions obtained by dissolution in DMSO were relatively stable over time, but the dissolution method in autoclave caused some degradation of the molecules, and their solutions display a high tendency to retrograde. PMID:26232931

  12. Development and evaluation of methods for starch dissolution using asymmetrical flow field-flow fractionation. Part I: Dissolution of amylopectin.

    PubMed

    Perez-Rea, Daysi; Bergenståhl, Björn; Nilsson, Lars

    2015-06-01

    We have investigated methods of starch dissolution with the aim of finding an optimum method to completely dissolve starch granules to form a molecularly dissolved starch solution without degradation of the polymers. Glycogen was used as a model molecule for amylopectin, to identify the dissolution conditions under which the degradation of the polymers was limited or not present. Dissolution was performed in water with temperatures up to 200 °C, facilitated by the use of heating in an autoclave or a microwave oven, or in dimethyl sulfoxide (DMSO) at 100 °C. Waxy maize starch was chosen due to its high content of amylopectin and very low content of amylose. The degree of starch dissolution under different conditions was determined enzymatically. The effect of different dissolution conditions on the molar mass and root-mean-square radius of the polymers was determined with asymmetrical flow field-flow fractionation coupled to multi-angle light scattering and differential refractive index (AF4-MALS-dRI) detectors under aqueous conditions. The results suggest that reliable and accurate size separation and characterization of amylopectin can be obtained by dissolution of starch granules in an aqueous environment at 140 °C by autoclaving or in DMSO at 100 °C. The results also clearly show an upper limit for heat treatment of starch, above which degradation cannot be avoided. PMID:25925852

  13. Ligand-independent pathway that controls stability of interferon alpha receptor

    SciTech Connect

    Liu Jianghuai; Plotnikov, Alexander; Banerjee, Anamika; Suresh Kumar, K.G.; Ragimbeau, Josiane; Marijanovic, Zrinka; Baker, Darren P.; Pellegrini, Sandra; Fuchs, Serge Y.

    2008-03-07

    Ligand-specific negative regulation of cytokine-induced signaling relies on down regulation of the cytokine receptors. Down regulation of the IFNAR1 sub-unit of the Type I interferon (IFN) receptor proceeds via lysosomal receptor proteolysis, which is triggered by ubiquitination that depends on IFNAR1 serine phosphorylation. While IFN-inducible phosphorylation, ubiquitination, and degradation requires the catalytic activity of the Tyk2 Janus kinase, here we found the ligand- and Tyk2-independent pathway that promotes IFNAR1 phosphorylation, ubiquitination, and degradation when IFNAR1 is expressed at high levels. A major cellular kinase activity that is responsible for IFNAR1 phosphorylation in vitro does not depend on either ligand or Tyk2 activity. Inhibition of ligand-independent IFNAR1 degradation suppresses cell proliferation. We discuss the signaling events that might lead to ubiquitination and degradation of IFNAR1 via ligand-dependent and independent pathways and their potential physiologic significance.

  14. Deciphering ligands' interaction with Cu and Cu2O nanocrystal surfaces by NMR solution tools.

    PubMed

    Glaria, Arnaud; Cure, Jérémy; Piettre, Kilian; Coppel, Yannick; Turrin, Cédric-Olivier; Chaudret, Bruno; Fau, Pierre

    2015-01-12

    The hydrogenolysis of [Cu2{(iPrN)2(CCH3)}2] in the presence of hexadecylamine (HDA) or tetradecylphosphonic acid (TDPA) in toluene leads to 6-9 nm copper nanocrystals. Solution NMR spectroscopy has been used to describe the nanoparticle surface chemistry during the dynamic phenomenon of air oxidation. The ligands are organized as multilayered shells around the nanoparticles. The shell of ligands is controlled by both their intermolecular interactions and their bonding strength on the nanocrystals. Under ambient atmosphere, the oxidation rate of colloidal copper nanocrystals closely relies on the chemical nature of the employed ligands (base or acid). Primary amine molecules behave as soft ligands for Cu atoms, but are even more strongly coordinated on surface Cu(I) sites, thus allowing a very efficient corrosion protection of the copper core. On the contrary, the TDPA ligands lead to a rapid oxidation rate of Cu nanoparticles and eventually to the re-dissolution of Cu(II) species at the expense of the nanocrystals. PMID:25394357

  15. Site specific polarization transfer from a hyperpolarized ligand of dihydrofolate reductase.

    PubMed

    Wang, Yunyi; Ragavan, Mukundan; Hilty, Christian

    2016-05-01

    Protein-ligand interaction is often characterized using polarization transfer by the intermolecular nuclear Overhauser effect (NOE). For such NOE experiments, hyperpolarization of nuclear spins presents the opportunity to increase the spin magnetization, which is transferred, by several orders of magnitude. Here, folic acid, a ligand of dihydrofolate reductase (DHFR), was hyperpolarized on (1)H spins using dissolution dynamic nuclear polarization (D-DNP). Mixing hyperpolarized ligand with protein resulted in observable increases in protein (1)H signal predominantly in the methyl group region of the spectra. Using (13)C single quantum selection in a series of one-dimensional spectra, the carbon chemical shift ranges of the corresponding methyl groups can be elucidated. Signals observed in these hyperpolarized spectra could be confirmed using 3D isotope filtered NOESY spectra, although the hyperpolarized spectra were obtained in single scans. By further correlating the signal intensities observed in the D-DNP experiments with the occurrence of short distances in the crystal structure of the protein-ligand complex, the observed methyl proton signals could be matched to the chemical shifts of six amino acids in the active site of DHFR-folic acid binary complex. These data demonstrate that (13)C chemical shift selection of protein resonances, combined with the intrinsic selectivity towards magnetization originating from the initially hyperpolarized spins, can be used for site specific characterization of protein-ligand interactions. PMID:27189223

  16. In vitro dissolution of uranium oxide by baboon alveolar macrophages

    SciTech Connect

    Poncy, J.L.; Dhilly, M.; Verry, M. ); Metivier, H. ); Masse, R. )

    1992-07-01

    In vitro cellular dissolution tests for insoluble forms of uranium oxide are technically difficult with conventional methodology using adherent alveolar macrophages. The limited number of cells per flask and the slow dissolution rate in a large volume of nutritive medium are obvious restricting factors. macrophages in suspension cannot be substituted because they represent different and poorly reproducible functional subtypes with regard to activation and enzyme secretion. Preliminary results on the dissolution of uranium oxide using immobilized alveolar macrophages are promising because large numbers of highly function macrophages can be cultured in a limited volume. Cells were obtained by bronchoalveolar lavages performed on baboons (Papio papio) and then immobilized after the phagocytosis of uranium octoxide (U[sub 3]O[sub 8]) particles in alginate beads linked with Ca[sup 2+]. The dissolution rate expressed as percentage of initial uranium content in cells was 0.039 [+-] 0.016%/day for particles with a count median geometric diameter of 3.84 [mu]m([sigma][sub g] = 1.84). A 2-fold increase in the dissolution rate was observed when the same number of particles was immobilized without macrophages. These results, obtained in vitro, suggest that the U[sub 3]O[sub g] preparation investigated should be assigned to inhalation class Y as recommended by the International Commission on Radiological Protection. Future experiments are intended to clarify this preliminary work and to examine the dissolution characteristics of other particles such as uranium dioxide. It is recommended that the dissolution rate should be measured over an interval of 3 weeks, which is compatible with the survival time of immobilized cells in culture and may reveal transformation states occurring with aging of the particles. 23 refs., 3 figs.

  17. In vitro dissolution of uranium oxide by baboon alveolar macrophages.

    PubMed

    Poncy, J L; Metivier, H; Dhilly, M; Verry, M; Masse, R

    1992-07-01

    In vitro cellular dissolution tests for insoluble forms of uranium oxide are technically difficult with conventional methodology using adherent alveolar macrophages. The limited number of cells per flask and the slow dissolution rate in a large volume of nutritive medium are obvious restricting factors. Macrophages in suspension cannot be substituted because they represent different and poorly reproducible functional subtypes with regard to activation and enzyme secretion. Preliminary results on the dissolution of uranium oxide using immobilized alveolar macrophages are promising because large numbers of highly functional macrophages can be cultured in a limited volume. Cells were obtained by bronchoalveolar lavages performed on baboons (Papio papio) and then immobilized after the phagocytosis of uranium octoxide (U3O8) particles in alginate beads linked with Ca2+. The dissolution rate expressed as percentage of initial uranium content in cells was 0.039 +/- 0.016%/day for particles with a count median geometric diameter of 3.84 microns(sigma g = 1.84). A 2-fold increase in the dissolution rate was observed when the same number of particles was immobilized without macrophages. These results, obtained in vitro, suggest that the U3O8 preparation investigated should be assigned to inhalation class Y as recommended by the International Commission on Radiological Protection. Future experiments are intended to clarify this preliminary work and to examine the dissolution characteristics of other particles such as uranium dioxide. It is recommended that the dissolution rate should be measured over an interval of 3 weeks, which is compatible with the survival time of immobilized cells in culture and may reveal transformation states occurring with aging of the particles. PMID:1396447

  18. In vitro dissolution of uranium oxide by baboon alveolar macrophages.

    PubMed Central

    Poncy, J L; Metivier, H; Dhilly, M; Verry, M; Masse, R

    1992-01-01

    In vitro cellular dissolution tests for insoluble forms of uranium oxide are technically difficult with conventional methodology using adherent alveolar macrophages. The limited number of cells per flask and the slow dissolution rate in a large volume of nutritive medium are obvious restricting factors. Macrophages in suspension cannot be substituted because they represent different and poorly reproducible functional subtypes with regard to activation and enzyme secretion. Preliminary results on the dissolution of uranium oxide using immobilized alveolar macrophages are promising because large numbers of highly functional macrophages can be cultured in a limited volume. Cells were obtained by bronchoalveolar lavages performed on baboons (Papio papio) and then immobilized after the phagocytosis of uranium octoxide (U3O8) particles in alginate beads linked with Ca2+. The dissolution rate expressed as percentage of initial uranium content in cells was 0.039 +/- 0.016%/day for particles with a count median geometric diameter of 3.84 microns(sigma g = 1.84). A 2-fold increase in the dissolution rate was observed when the same number of particles was immobilized without macrophages. These results, obtained in vitro, suggest that the U3O8 preparation investigated should be assigned to inhalation class Y as recommended by the International Commission on Radiological Protection. Future experiments are intended to clarify this preliminary work and to examine the dissolution characteristics of other particles such as uranium dioxide. It is recommended that the dissolution rate should be measured over an interval of 3 weeks, which is compatible with the survival time of immobilized cells in culture and may reveal transformation states occurring with aging of the particles. PMID:1396447

  19. The effect of additives on lime dissolution rates. Final report

    SciTech Connect

    Khang, S.J.

    1996-07-31

    Based on the previous years` studies concerning the efficiency of SO{sub 2} removal by spray dryers with high sulfur coal flue gas, the work for year five included investigations of lime dissolution rates at different slaking conditions and with the effect of additives. The prominent additives that have significant effects on lime dissolution rates were tested with the mini pilot spray drying absorber to see their effects on spray drying desulfurization applications. The mechanisms of these additive effects along with the properties of hygroscopic additives have been discussed and incorporated into the spray drying desulfurization model ``SPRAYMOD-M.`` Slaking conditions are very important factors in producing high quality lime slurry in spray drying desulfurization processes. At optimal slaking conditions, the slaked lime particles are very fine (3-5{mu}m) and the slaked lime has high BET surface areas which are beneficial to the desulfurization. The slaked lime dissolution rate experiments in our study are designed to determine how much lime can dissolve in a unit time if the initial lime surface area is kept constant. The purpose of the dissolution rate study for different additives is to find those effective additives that can enhance lime dissolution rates and to investigate the mechanisms of the dissolution rate enhancement properties for these additives. The applications of these additives on spray drying desulfurization are to further verify the theory that dissolution rate is a rate limiting step in the whole spray drying desulfurization process as well as to test the feasibility of these additives on enhancing SO{sub 2} removal in spray dryers.

  20. Simulation of in vitro dissolution behavior using DDDPlus™.

    PubMed

    Almukainzi, May; Okumu, Arthur; Wei, Hai; Löbenberg, Raimar

    2015-02-01

    Dissolution testing is a performance test for many dosage forms including tablets and capsules. The objective of this study was to evaluate if computer simulations can predict the in vitro dissolution of two model drugs for which different dissolution data were available. Published montelukast sodium and glyburide dissolution data was used for the simulations. Different pharmacopeial and biorelevant buffers, volumes, and rotations speeds were evaluated. Additionally, a pH change protocol was evaluated using these buffers. DDDPlus™ 3, Beta version (Simulation Plus, Inc.), was used to simulate the in vitro dissolution data. The simulated data were compared with the in vitro data. A regression coefficient between predicted and observed data was used to assess the simulations. The statistical analysis of Montelukast sodium showed that there was a significant correlation between the in vitro release data and the predicted data for all cases except for one buffer. For glyburide, there was also a significant correlation between the experimental data and the predicted data using single pH conditions. Using the dynamic pH protocol, a correlation was significant for one biorelevant media. The simulations showed that both in vitro drug releases were sensitive to solubility effects which confirmed their BCS class II category. Computer simulations of the in vitro release using DDDPlus™ have the potential to estimate the in vivo dissolution at an early stage in the drug development process. This might be used to choose the most appropriate dissolution condition to establish IVIVC and to develop biorelevant in vitro performance tests to capture critical product attributes for quality control procedures in quality by design environments. PMID:25409918

  1. What are Nuclear Receptor Ligands?

    PubMed Central

    Sladek, Frances M.

    2010-01-01

    Nuclear receptors (NRs) are a family of highly conserved transcription factors that regulate transcription in response to small lipophilic compounds. They play a role in every aspect of development, physiology and disease in humans. They are also ubiquitous in and unique to the animal kingdom suggesting that they may have played an important role in their evolution. In contrast to the classical endocrine receptors that originally defined the family, recent studies suggest that the first NRs might have been sensors of their environment, binding ligands that were external to the host organism. The purpose of this review is to provide a broad perspective on NR ligands and address the issue of exactly what constitutes a NR ligand from historical, biological and evolutionary perspectives. This discussion will lay the foundation for subsequent reviews in this issue as well as pose new questions for future investigation. PMID:20615454

  2. Why mercury prefers soft ligands

    SciTech Connect

    Riccardi, Demian M; Guo, Hao-Bo; Gu, Baohua; Parks, Jerry M; Summers, Anne; Miller, S; Liang, Liyuan; Smith, Jeremy C

    2013-01-01

    Mercury (Hg) is a major global pollutant arising from both natural and anthropogenic sources. Defining the factors that determine the relative affinities of different ligands for the mercuric ion, Hg2+, is critical to understanding its speciation, transformation, and bioaccumulation in the environment. Here, we use quantum chemistry to dissect the relative binding free energies for a series of inorganic anion complexes of Hg2+. Comparison of Hg2+ ligand interactions in the gaseous and aqueous phases shows that differences in interactions with a few, local water molecules led to a clear periodic trend within the chalcogenide and halide groups and resulted in the well-known experimentally observed preference of Hg2+ for soft ligands such as thiols. Our approach establishes a basis for understanding Hg speciation in the biosphere.

  3. Fluorescent Ligands for Adenosine Receptors

    PubMed Central

    Kozma, Eszter; Jayasekara, P Suresh; Squarcialupi, Lucia; Paoletta, Silvia; Moro, Stefano; Federico, Stephanie; Spalluto, Giampiero; Jacobson, Kenneth A.

    2012-01-01

    Interest is increasing in developing fluorescent ligands for characterization of adenosine receptors (ARs), which hold a promise of usefulness in the drug discovery process. The size of a strategically labeled AR ligand can be greatly increased after the attachment of a fluorophore. The choice of dye moiety (e.g. Alexa Fluor 488), attachment point and linker length can alter the selectivity and potency of the parent molecule. Fluorescent derivatives of adenosine agonists and antagonists (e.g. XAC and other heterocyclic antagonist scaffolds) have been synthesized and characterized pharmacologically. Some are useful AR probes for flow cytometry, fluorescence correlation spectroscopy, fluorescence microscopy, fluorescence polarization, fluorescence resonance energy transfer, and scanning confocal microscopy. Thus, the approach of fluorescent labeled GPCR ligands, including those for ARs, is a growing dynamic research field. PMID:23200243

  4. Molecular Recognition and Ligand Association

    NASA Astrophysics Data System (ADS)

    Baron, Riccardo; McCammon, J. Andrew

    2013-04-01

    We review recent developments in our understanding of molecular recognition and ligand association, focusing on two major viewpoints: (a) studies that highlight new physical insight into the molecular recognition process and the driving forces determining thermodynamic signatures of binding and (b) recent methodological advances in applications to protein-ligand binding. In particular, we highlight the challenges posed by compensating enthalpic and entropic terms, competing solute and solvent contributions, and the relevance of complex configurational ensembles comprising multiple protein, ligand, and solvent intermediate states. As more complete physics is taken into account, computational approaches increase their ability to complement experimental measurements, by providing a microscopic, dynamic view of ensemble-averaged experimental observables. Physics-based approaches are increasingly expanding their power in pharmacology applications.

  5. Multifunctional Ligands in Transition Metal Catalysis

    SciTech Connect

    Crabtree, Robert H

    2011-01-01

    Sophisticated ligands are now being designed that do far more than just fulfil their traditional spectator roles by binding to the metal and providing a sterically-defined binding pocket for the substrate in homogeneous transition metal catalysis. This Focus review emphasizes selected cases in which ligands carry additional functional groups that change the properties of the ligand as a result of an external stimulus or undergo catalytically-relevant ligand-based reactivity. These include proton responsive ligands capable of gaining or losing one or more protons, ligands having a hydrogen bonding function, electroresponsive ligands capable of gaining or losing one or more electrons, and photoresponsive ligands capable of undergoing a useful change of properties upon irradiation. Molecular recognition ligands and proton coupled electron transfer (PCET) are briefly discussed.

  6. Effect of synovial fluid, phosphate-buffered saline solution, and water on the dissolution and corrosion properties of CoCrMo alloys as used in orthopedic implants.

    PubMed

    Lewis, A C; Kilburn, M R; Papageorgiou, I; Allen, G C; Case, C P

    2005-06-15

    The corrosion and dissolution of high- and low-carbon CoCrMo alloys, as used in orthopedic joint replacements, were studied by immersing samples in phosphate-buffered saline (PBS), water, and synovial fluid at 37 degrees C for up to 35 days. Bulk properties were analyzed with a fine ion beam microscope. Surface analyses by X-ray photoelectron spectroscopy and Auger electron spectroscopy showed surprisingly that synovial fluid produced a thin oxide/hydroxide layer. Release of ions into solution from the alloy also followed an unexpected pattern where synovial fluid, of all the samples, had the highest Cr concentration but the lowest Co concentration. The presence of carbide inclusions in the alloy did not affect the corrosion or the dissolution mechanisms, although the carbides were a significant feature on the metal surface. Only one mechanism was recognized as controlling the thickness of the oxide/hydroxide interface. The analysis of the dissolved metal showed two mechanisms at work: (1) a protein film caused ligand-induced dissolution, increasing the Cr concentration in synovial fluid, and was explained by the equilibrium constants; (2) corrosion at the interface increased the Co in PBS. The effect of prepassivating the samples (ASTM F-86-01) did not always have the desired effect of reducing dissolution. The release of Cr into PBS increased after prepassivation. The metal-synovial fluid interface did not contain calcium phosphate as a deposit, typically found where samples are exposed to calcium rich bodily fluids. PMID:15900610

  7. Multidentate oligomeric ligands to enhance the biocompatibility of iron oxide and other metal nanoparticles

    NASA Astrophysics Data System (ADS)

    Wang, Wentao; Palui, Goutam; Ji, Xin; Aldeek, Fadi; Mattoussi, Hedi

    2014-03-01

    We prepared a set of multi-coordinating and reactive amphiphilic polymer ligands and used them for surface-functionalizing magnetic iron oxide nanoparticles. The amphiphilic oligomers were prepared by coupling (via one step nucleophilic addition) several dopamine anchoring groups, polyethylene glycol moieties and reactive groups onto a poly(isobutylene-alt-maleic anhydride) chain. The availability of several anchoring groups in the same ligand greatly enhances the ligand affinity to the nanoparticle surfaces, via multiplecoordination, while the hydrophilic and reactive groups promote colloidal stability in buffer media and allow subsequent conjugation to target biomolecules. The hydrophilic nanoparticles capped with these polymers maintain compact size and exhibit great long term colloidal stability.

  8. Biotite dissolution in brine at varied temperatures and CO2 pressures: its activation energy and potential CO2 intercalation.

    PubMed

    Hu, Yandi; Jun, Young-Shin

    2012-10-16

    For sustainable geologic CO(2) sequestration (GCS), it is important to understand the effects of temperature and CO(2) pressure on mica's dissolution and surface morphological changes under saline hydrothermal conditions. Batch experiments were conducted with biotite (Fe-end member mica) under conditions relevant to GCS sites (35-95 °C and 75-120 atm CO(2)), and 1 M NaCl solution was used to mimic the brine. With increasing temperature, a transition from incongruent to congruent dissolution of biotite was observed. The dissolution activation energy based on Si release was calculated to be 52 ± 5 kJ mol(-1). By comparison with N(2) experiments, we showed that CO(2) injection greatly enhanced biotite's dissolution and its surface morphology evolutions, such as crack formation and detachment of newly formed fibrous illite. For biotite's dissolution and morphological evolutions, the pH effects of CO(2) were differentiated from the effects of bicarbonate complexation and CO(2) intercalation. Bicarbonate complexation effects on ion release from biotite were found to be minor under our experimental conditions. On the other hand, the CO(2) molecules in brine could get into the biotite interlayer and cause enhanced swelling of the biotite interlayer and hence the observed promotion of biotite surface cracking. The cracking created more reactive surface area in contact with brine and thus enhanced the later ion release from biotite. These results provide new information for understanding CO(2)-brine-mica interactions in saline aquifers with varied temperatures and CO(2) pressures, which can be useful for GCS site selection and operations. PMID:22989382

  9. Dissolution behavior of plasma-sprayed hydroxyapatite coatings.

    PubMed

    Fazan, F; Marquis, P M

    2000-12-01

    The long-term stability of plasma-sprayed hydroxyapatite coatings is influenced by the dissolution behavior of the coating in in vivo conditions. Plasma-spraying generates a mixture of phases and this study has focused on how the balance of phases affects the in vitro dissolution behavior of the coatings in double distilled-deionized water and in tris-buffer solutions. The pH changes in double distilled-deionized water were monitored, whilst the pH value was maintained at 7.25 for the tris-buffer solution at 37 degrees C with 5% CO2 atmosphere. The phosphate and calcium ions released were measured using UV-Visible Spectrophotometer and Atomic Absorption Spectroscopy respectively. Changes in crystal and surface topology were also studied. The results indicate that the dissolution behavior of the coatings depends on several factors. The rate of release of phosphate ions was found to increase significantly for the tris-buffer solution compared to the deionized water, indicating that the presence of electrolyte constituents affects the dissolution behavior of the coatings. The Ca/P ratio in the tris-buffer solution is approximately three. Increases in the level of crystallinity of the coatings significantly decreased the dissolution rate and hence, the amount of phosphate ions released. The higher the percentage of crystallinity, the higher the stability of the coating under in vitro conditions. PMID:15348061

  10. Dissolution of coccolithophorid calcite by microzooplankton and copepod grazing

    NASA Astrophysics Data System (ADS)

    Antia, A. N.; Suffrian, K.; Holste, L.; Müller, M. N.; Nejstgaard, J. C.; Simonelli, P.; Carotenuto, Y.; Putzeys, S.

    2008-01-01

    Independent of the ongoing acidification of surface seawater, the majority of the calcium carbonate produced in the pelagial is dissolved by natural processes above the lysocline. We investigate to what extent grazing and passage of coccolithophorids through the guts of copepods and the food vacuoles of microzooplankton contribute to calcite dissolution. In laboratory experiments where the coccolithophorid Emiliania huxleyi was fed to the rotifer Brachionus plicatilis, the heterotrophic flagellate Oxyrrhis marina and the copepod Acartia tonsa, calcite dissolution rates of 45-55%, 37-53% and 5-22% of ingested calcite were found. We ascribe higher loss rates in microzooplankton food vacuoles as compared to copepod guts to the strongly acidic digestion and the individual packaging of algal cells. In further experiments, specific rates of calcification and calcite dissolution were also measured in natural populations during the PeECE III mesocosm study under differing ambient pCO2 concentrations. Microzooplankton grazing accounted for between 27 and 70% of the dynamic calcite stock being lost per day, with no measurable effect of CO2 treatment. These measured calcite dissolution rates indicate that dissolution of calcite in the guts of microzooplankton and copepods can account for the calcite losses calculated for the global ocean using budget and model estimates.

  11. Laboratory simulation of salt dissolution during waste removal

    SciTech Connect

    Wiersma, B.J.; Parish, W.R.

    1997-01-01

    Laboratory experiments were performed to support the field demonstration of improved techniques for salt dissolution in waste tanks at the Savannah River Site. The tests were designed to investigate three density driven techniques for salt dissolution: (1) Drain-Add-Sit-Remove, (2) Modified Density Gradient, and (3) Continuous Salt Mining. Salt dissolution was observed to be a very rapid process as salt solutions with densities between 1.38-1.4 were frequently removed. Slower addition and removal rates and locating the outlet line at deeper levels below the top of the saltcake provided the best contact between the dissolution water and the saltcake. It was observed that dissolution with 1 M sodium hydroxide solution resulted in salt solutions that were within the current inhibitor requirements for the prevention of stress corrosion cracking. This result was independent of the density driven technique. However, if inhibited water (0.01 M sodium hydroxide and 0.011 M sodium nitrite) was utilized, the salt solutions were frequently outside the inhibitor requirements. Corrosion testing at conditions similar to the environments expected during waste removal was recommended.

  12. On the effects of subsurface parameters on evaporite dissolution (Switzerland).

    PubMed

    Zidane, Ali; Zechner, Eric; Huggenberger, Peter; Younes, Anis

    2014-05-01

    Uncontrolled subsurface evaporite dissolution could lead to hazards such as land subsidence. Observed subsidences in a study area of Northwestern Switzerland were mainly due to subsurface dissolution (subrosion) of evaporites such as halite and gypsum. A set of 2D density driven flow simulations were evaluated along 1000 m long and 150 m deep 2D cross sections within the study area that is characterized by tectonic horst and graben structures. The simulations were conducted to study the effect of the different subsurface parameters that could affect the dissolution process. The heterogeneity of normal faults and its impact on the dissolution of evaporites is studied by considering several permeable faults that include non-permeable areas. The mixed finite element method (MFE) is used to solve the flow equation, coupled with the multipoint flux approximation (MPFA) and the discontinuous Galerkin method (DG) to solve the diffusion and the advection parts of the transport equation. Results show that the number of faults above the lower aquifer that contains the salt layer is considered as the most important factor that affects the dissolution compared to the other investigated parameters of thickness of the zone above the halite formation, a dynamic conductivity of the lower aquifer, and varying boundary conditions in the upper aquifer. PMID:24650646

  13. Effect of solution saturation state and temperature on diopside dissolution

    SciTech Connect

    Dixit, S; Carroll, S A

    2007-03-23

    Steady-state dissolution rates of diopside are measured as a function of solution saturation state using a titanium flow-through reactor at pH 7.5 and temperature ranging from 125 to 175 C. Diopside dissolved stoichiometrically under all experimental conditions and rates were not dependent on sample history. At each temperature, rates continuously decreased by two orders of magnitude as equilibrium was approached and did not exhibit a dissolution plateau of constant rates at high degrees of undersaturation. The variation of diopside dissolution rates with solution saturation can be described equally well with a ion exchange model based on transition state theory or pit nucleation model based on crystal growth/dissolution theory from 125 to 175 C. At 175 C, both models over predict dissolution rates by two orders of magnitude indicating that a secondary phase precipitated in the experiments. The ion exchange model assumes the formation of a Si-rich, Mg-deficient precursor complex. Lack of dependence of rates on steady-state aqueous calcium concentration supports the formation of such a complex, which is formed by exchange of protons for magnesium ions at the surface.

  14. Factors affecting the in vitro dissolution of cobalt oxide

    SciTech Connect

    Collier, C.G. ); Pearce, M.J.; Hodgson, A.; Ball, A. )

    1992-07-01

    In a recent interspecies comparison of the lung clearance of cobalt oxide ([sup 57]Co[sub 3]O[sub 4]), differences of up to 4-fold were found in the translocation rates of [sup 57]Co to blood between seven different animal species, including man. This study investigated some factors that could influence the dissolution of this material in vitro. The effect of bicarbonate and citrate concentrations (over physiological ranges) and medium pH on in vitro dissolution of [sup 57]Co from [sup 57]Co[sub 3]O[sub 4] particles was measured in a simple noncellular system. pH levels of 4.5, 6.1, and 7.2 were used to correspond to those in the alveolar macrophage lysosome, its cytoplasm, and the extracellular lung fluid. Measurements of the fractional dissolution rate were made weekly for 3 months. pH had the greatest effect on dissolution rates, with particles suspended in the lowest pH medium (4.5) dissolving at a significantly faster rate than at higher pH values. Increasing citrate concentrations resulted in slightly higher dissolution rates, but there was no effect of bicarbonate concentration. There was no evidence of synergism between the factors studied. 18 refs., 2 figs., 2 tabs.

  15. A new biorelevant dissolution method for orodispersible films.

    PubMed

    Krampe, Raphael; Sieber, Daniel; Pein-Hackelbusch, Miriam; Breitkreutz, Jörg

    2016-01-01

    Specific knowledge about the dissolution behavior under biorelevant conditions is of high interest for the rational development of orodispersible films (ODFs). As the conditions in the oral cavity strongly differ from those in the gastrointestinal tract and from those performed with the pharmacopoeial test setups, a biorelevant dissolution setup was developed in this work, considering the mechanical force of the tongue, the saliva flow, the small fluid volume and the saliva composition. Especially in the initial phase, dissolution profiles of KTP (ketoprofen) ODFs observed by the new method showed a slower drug release than obtained with setups based on conventional dissolution methods. 27.47% KTP release after 100s was detected using the new method, compared to 59.29-82.55% detected without considering the in vivo conditions. Furthermore, an influence of the simulated in vivo conditions on the dissolution profile was observed. By simulating either saliva flow or mechanical force, the KTP release after 100s was two to three times higher (18.78% and 14.18%) compared to the profiles, measured without considering one of the parameters (6.76%). Further studies have to show, whether obtained data are comparable to in vivo data to predict drug release profiles of ODFs in the oral cavity. PMID:26515261

  16. Kinetics of Carbon Dissolution of Coke in Molten Iron

    NASA Astrophysics Data System (ADS)

    Jang, Dongik; Kim, Yumkyum; Shin, Minsoo; Lee, Joonho

    2012-12-01

    The effect of temperature on the dissolution rate of carbon from coke in molten iron was investigated using a sampling technique in the temperature range of 1723 K to 1923 K (1450 °C to 1650 °C). The dissolution rate of carbon from coke in molten iron increased as the temperature increased. At 1923 K (1650 °C), the rate-determining step was the mass transfer of carbon in the boundary layer adjacent to the metal-carbon interface. At 1723 K (1450 °C), the rate-determining step changed from the mass transfer to the interfacial chemical reaction as the reaction proceeded. At 1823 K (1550 °C), both reaction steps affected the apparent reaction rates. Sulfur dissolution did not affect the carbon dissolution rates in molten iron, so it was considered that the sulfur adsorption at the metal/coke interface was not so significant. The apparent activation energy of the carbon dissolution of coke in molten iron was estimated to be 442 kJ/mol.

  17. Dissolution of magnetically marked tablets: investigations in a physical phantom.

    PubMed

    Biller, S; Domey, J; Fiedler, P; Holzhey, R; Richert, H; Haueisen, J

    2012-01-01

    Pharmacological research is strongly driven by maximizing the bioavailability of new pharmaceuticals. For orally applied drugs the bioavailability highly depends on the process of dissolution in the gastrointestinal tract and is affected by numerous physiological and environmental factors. Available techniques for in vivo monitoring of the dissolution process are very limited and not applicable for large studies. The technique of magnetic marker monitoring provides new prospects for these investigations. However, it is currently limited due to low fields common magnetic markers produce. Hence, only highly sensitive sensors are applicable. In this paper, we performed dissolution tests of novel markers in a physical phantom with magnetoresistive sensors in an unshielded environment. The markers were continuously localized and the movement through the phantom was tracked. By analyzing the changing magnetic moment of the markers we were able to monitor the progress of dissolution in the phantom. We conclude that our proposed phantom and tracking technique is an important step towards new systems for in vivo monitoring of pharmaceutical dissolution processes. PMID:23366328

  18. How good is cola for dissolution of gastric phytobezoars?

    PubMed Central

    Lee, Beom Jae; Park, Jong-Jae; Chun, Hoon Jai; Kim, Ji Hoon; Yeon, Jong Eun; Jeen, Yoon Tae; Kim, Jae Seon; Byun, Kwan Soo; Lee, Sang Woo; Choi, Jae Hyun; Kim, Chang Duck; Ryu, Ho Sang; Bak, Young-Tae

    2009-01-01

    AIM: To evaluate the efficacy of cola treatment for gastric phytobezoars, including diospyrobezoars. METHODS: A total of 17 patients (range: 48 to 78 years) with symptomatic gastric phytobezoars treated with cola and adjuvant endoscopic therapy were reviewed. Three liters of cola lavage (10 cases) or drink (7 cases) were initially used, and then endoscopic fragmentation was done for the remnant bezoars by using a lithotripsy basket or a polypectomy snare. The overall success of dissolving a gastric phytobezoars with using three liters of cola and the clinical and endoscopic findings were compared retrospectively between four cases of complete dissolution by using only cola and 13 cases of partial dissolution with cola. RESULTS: After 3 L of cola lavage or drinking, a complete dissolution of bezoars was achieved in four patients (23.5%), while 13 cases (76.5%) were only partially dissolved. Phytobezoars (4 of 6 cases) were observed more frequently than diospyrobezoars (0 of 11) in the group that underwent complete dissolution (P = 0.006). Gender, symptom duration, size of bezoar and method of cola administration were not significantly different between the two groups. Twelve of 13 patients with residual bezoars were completely treated with a combination of cola and endoscopic fragmentation. CONCLUSION: The rate of complete dissolution with three liters of cola was 23.5%, but no case of diospyrobezoar was completely dissolved using this method. However, pretreatment with cola may be helpful and facilitate endoscopic fragmentation of gastric phytobezoars. PMID:19437568

  19. Combinatorial localized dissolution analysis: Application to acid-induced dissolution of dental enamel and the effect of surface treatments.

    PubMed

    Parker, Alexander S; Al Botros, Rehab; Kinnear, Sophie L; Snowden, Michael E; McKelvey, Kim; Ashcroft, Alexander T; Carvell, Mel; Joiner, Andrew; Peruffo, Massimo; Philpotts, Carol; Unwin, Patrick R

    2016-08-15

    A combination of scanning electrochemical cell microscopy (SECCM) and atomic force microscopy (AFM) is used to quantitatively study the acid-induced dissolution of dental enamel. A micron-scale liquid meniscus formed at the end of a dual barrelled pipette, which constitutes the SECCM probe, is brought into contact with the enamel surface for a defined period. Dissolution occurs at the interface of the meniscus and the enamel surface, under conditions of well-defined mass transport, creating etch pits that are then analysed via AFM. This technique is applied to bovine dental enamel, and the effect of various treatments of the enamel surface on acid dissolution (1mM HNO3) is studied. The treatments investigated are zinc ions, fluoride ions and the two combined. A finite element method (FEM) simulation of SECCM mass transport and interfacial reactivity, allows the intrinsic rate constant for acid-induced dissolution to be quantitatively determined. The dissolution of enamel, in terms of Ca(2+) flux ( [Formula: see text] ), is first order with respect to the interfacial proton concentration and given by the following rate law: [Formula: see text] , with k0=0.099±0.008cms(-1). Treating the enamel with either fluoride or zinc ions slows the dissolution rate, although in this model system the partly protective barrier only extends around 10-20nm into the enamel surface, so that after a period of a few seconds dissolution of modified surfaces tends towards that of native enamel. A combination of both treatments exhibits the greatest protection to the enamel surface, but the effect is again transient. PMID:27209395

  20. Dissolution of Arsenic Minerals Mediated by Dissimilatory Arsenate Reducing Bacteria: Estimation of the Physiological Potential for Arsenic Mobilization

    PubMed Central

    Lukasz, Drewniak; Liwia, Rajpert; Aleksandra, Mantur; Aleksandra, Sklodowska

    2014-01-01

    The aim of this study was characterization of the isolated dissimilatory arsenate reducing bacteria in the context of their potential for arsenic removal from primary arsenic minerals through reductive dissolution. Four strains, Shewanella sp. OM1, Pseudomonas sp. OM2, Aeromonas sp. OM4, and Serratia sp. OM17, capable of anaerobic growth with As (V) reduction, were isolated from microbial mats from an ancient gold mine. All of the isolated strains: (i) produced siderophores that promote dissolution of minerals, (ii) were resistant to dissolved arsenic compounds, (iii) were able to use the dissolved arsenates as the terminal electron acceptor, and (iii) were able to use copper minerals containing arsenic minerals (e.g., enargite) as a respiratory substrate. Based on the results obtained in this study, we postulate that arsenic can be released from some As-bearing polymetallic minerals (such as copper ore concentrates or middlings) under reductive conditions by dissimilatory arsenate reducers in indirect processes. PMID:24724102

  1. Dissolution of arsenic minerals mediated by dissimilatory arsenate reducing bacteria: estimation of the physiological potential for arsenic mobilization.

    PubMed

    Lukasz, Drewniak; Liwia, Rajpert; Aleksandra, Mantur; Aleksandra, Sklodowska

    2014-01-01

    The aim of this study was characterization of the isolated dissimilatory arsenate reducing bacteria in the context of their potential for arsenic removal from primary arsenic minerals through reductive dissolution. Four strains, Shewanella sp. OM1, Pseudomonas sp. OM2, Aeromonas sp. OM4, and Serratia sp. OM17, capable of anaerobic growth with As (V) reduction, were isolated from microbial mats from an ancient gold mine. All of the isolated strains: (i) produced siderophores that promote dissolution of minerals, (ii) were resistant to dissolved arsenic compounds, (iii) were able to use the dissolved arsenates as the terminal electron acceptor, and (iii) were able to use copper minerals containing arsenic minerals (e.g., enargite) as a respiratory substrate. Based on the results obtained in this study, we postulate that arsenic can be released from some As-bearing polymetallic minerals (such as copper ore concentrates or middlings) under reductive conditions by dissimilatory arsenate reducers in indirect processes. PMID:24724102

  2. A porous silica rock ("tripoli") in the footwall of the Jurassic Úrkút manganese deposit, Hungary: composition, and origin through carbonate dissolution

    USGS Publications Warehouse

    Polgari, Marta; Szabo, Zoltan; Szabo-Drubina, Magda; Hein, James R.; Yeh, Hsueh-Wen

    2005-01-01

    The mineralogical, chemical, and isotopic compositions were determined for a white tripoli from the footwall of the Jurassic Úrkút Mn-oxide ore deposit in the Bakony Mountains, Hungary. The tripoli consists of quartz and chalcedony, with SiO2 contents up to 100 wt.%; consequently, trace-element contents are very low. Oxygen isotopes and quartz crystallinity indicate a low-temperature diagenetic origin for this deposit. The tripoli was formed by dissolution of the carbonate portion of the siliceous (sponge spicules) Isztimér Limestone. Dissolution of the carbonate was promoted by inorganic and organic acids generated during diagensis and left a framework composed of diagenetic silica that preserved the original volume of the limestone layer. The relative enrichment of silica and high porosity is the result of that carbonate dissolution. The silty texture of this highly friable rock is due to the structurally weak silica framework.

  3. Functional Short-Bite Ligands: Synthesis, Coordination Chemistry, and Applications of N-Functionalized Bis(diaryl/dialkylphosphino)amine-type Ligands.

    PubMed

    Fliedel, Christophe; Ghisolfi, Alessio; Braunstein, Pierre

    2016-08-24

    The aim of this review is to highlight how the diversity generated by N-substitution in the well-known short-bite ligand bis(diphenylphosphino)amine (DPPA) allows a fine-tuning of the ligand properties and offers a considerable scope for tailoring the properties and applications of their corresponding metal complexes. The various N-substituents include nitrogen-, oxygen-, phosphorus-, sulfur-, halogen-, and silicon-based functionalities and directly N-bound metals. Multiple DPPA-type ligands linked through an organic spacer and N-functionalized DRPA-type ligands, in which the PPh2 substituents are replaced by PR2 (R = alkyl, benzyl) groups, are also discussed. Owing to the considerable diversity of N-functionalized DPPA-type ligands available, the applications of their mono- and polynuclear metal complexes are very diverse and range from homogeneous catalysis with well-defined or in situ generated (pre)catalysts to heterogeneous catalysis and materials science. In particular, sustained interest for DPPA-type ligands has been motivated, at least in part, by their ability to promote selective ethylene tri- or tetramerization in combination with chromium. Ligands and metal complexes where the N-substituent is a pure hydrocarbon group (as opposed to N-functionalization) are outside the scope of this review. However, when possible, a comparison between the catalytic performances of N-functionalized systems with those of their N-substituted analogs will be provided. PMID:27456550

  4. Role of microbial iron reduction in the dissolution of iron hydroxysulfate minerals

    USGS Publications Warehouse

    Jones, E.J.P.; Nadeau, T.-L.; Voytek, M.A.; Landa, E.R.

    2006-01-01

    Iron-hydroxysulfate minerals can be important hosts for metals such as lead, mercury, copper, zinc, silver, chromium, arsenic, and selenium and for radionuclides such as 226Ra. These mineral-bound contaminants are considered immobilized under oxic conditions. However, when anoxic conditions develop, the activities of sulfate- or iron-reducing bacteria could result in mineral dissolution, releasing these bound contaminants. Reduction of structural sulfate in the iron-hydroxysulfate mineral jarosite by sulfate-reducing bacteria has previously been demonstrated. The primary objective of this work was to evaluate the potential for anaerobic dissolution of the iron-hydroxysulfate minerals jarosite and schwertmannite at neutral PH by iron-reducing bacteria. Mineral dissolution was tested using a long-term cultivar, Geobacter metallireducens strain GS-15, and a fresh isolate Geobacter sp. strain ENN1, previously undescribed. ENN1 was isolated from the discharge site of Shadle Mine, in the southern anthracite coalfield of Pennsylvania, where schwertmannite was the predominant iron-hydroxysulfate mineral. When jarosite from Elizabeth Mine (Vermont) was provided as the sole terminal electron acceptor, resting cells of both G. metallireducens and ENN1 were able to reduce structural Fe(III), releasing Fe+2, SO4-2, and K+ ions. A lithified jarosite sample from Utah was more resistant to microbial attack, but slow release of Fe+2 was observed. Neither bacterium released Fe+2 from poorly crystalline synthetic schwertmannite. Our results indicate that exposure of jarosite to iron-reducing conditions at neutral pH is likely to promote the mobility of hazardous constituents and should therefore be considered in evaluating waste disposal and/or reclamation options involving jarosite-bearing materials.

  5. Polypharmacology of dopamine receptor ligands.

    PubMed

    Butini, S; Nikolic, K; Kassel, S; Brückmann, H; Filipic, S; Agbaba, D; Gemma, S; Brogi, S; Brindisi, M; Campiani, G; Stark, H

    2016-07-01

    Most neurological diseases have a multifactorial nature and the number of molecular mechanisms discovered as underpinning these diseases is continuously evolving. The old concept of developing selective agents for a single target does not fit with the medical need of most neurological diseases. The development of designed multiple ligands holds great promises and appears as the next step in drug development for the treatment of these multifactorial diseases. Dopamine and its five receptor subtypes are intimately involved in numerous neurological disorders. Dopamine receptor ligands display a high degree of cross interactions with many other targets including G-protein coupled receptors, transporters, enzymes and ion channels. For brain disorders like Parkinsońs disease, schizophrenia and depression the dopaminergic system, being intertwined with many other signaling systems, plays a key role in pathogenesis and therapy. The concept of designed multiple ligands and polypharmacology, which perfectly meets the therapeutic needs for these brain disorders, is herein discussed as a general ligand-based concept while focusing on dopaminergic agents and receptor subtypes in particular. PMID:27234980

  6. Competition among flow, dissolution, and precipitation in porous media

    SciTech Connect

    Rege, S.D.; Fogler, H.S. . Dept. of Chemical Engineering)

    1989-07-01

    A theoretical and experimental study has been carried out on flow, dissolution, and precipitation in porous media. Flow experiments were performed on linear carbonate cores using acidic ferric chloride solutions. Dissolution of the carbonate by the acid causes an increase in the solution pH, thereby precipitating ferric hydroxide. This precipitate plugs up the pore throats in the medium and increases the resistance to fluid flow. Fluctuations in the permeability ratio were observed during core flood experiments, confirming the competition between channel formation due to dissolution and pore plugging due to precipitation. The evolution of the pore structure was characterized. A network model has also been developed to describe flow and reaction in porous media. The model was used to simulate the ferric chloride system, and pressure oscillations predicted by the model show identical trends to those observed experimentally. Additionally, the evolution of pores in the network were graphically represented.

  7. Chemistry and kinetics of calcite dissolution in passive treatment systems

    SciTech Connect

    Rose, A.W.

    1999-07-01

    Reaction of calcite with AMD is a key remediation process in anoxic limestone drains, (ALD), SAPS, and many wetlands, but predictions of effluent quality are currently based mainly on rules of thumb and prior experience. The PHREEQC computer program can be used to calculate the progress of this and similar reactions, and aid in understanding, design and evaluation of these systems. At pH values less than 5, calcite dissolution rates are strongly influenced by transport parameters such as flow velocity. Estimated calcite dissolution rates from ALD's and column experiments indicate little change in rate with pH, in contrast to published data for well stirred lab experiments. The dissolution rate is affected by concentration of SO{sub 4}, Fe, Al, Ca, P, and other trace solutes. The optimum contact time and sizing of ALD's will be dependent on these and possibly other parameters. Additional experiments are needed to evaluate these dependencies.

  8. High Level Waste System Impacts from Acid Dissolution of Sludge

    SciTech Connect

    KETUSKY, EDWARD

    2006-04-20

    This research evaluates the ability of OLI{copyright} equilibrium based software to forecast Savannah River Site High Level Waste system impacts from oxalic acid dissolution of Tank 1-15 sludge heels. Without further laboratory and field testing, only the use of oxalic acid can be considered plausible to support sludge heel dissolution on multiple tanks. Using OLI{copyright} and available test results, a dissolution model is constructed and validated. Material and energy balances, coupled with the model, identify potential safety concerns. Overpressurization and overheating are shown to be unlikely. Corrosion induced hydrogen could, however, overwhelm the tank ventilation. While pH adjustment can restore the minimal hydrogen generation, resultant precipitates will notably increase the sludge volume. OLI{copyright} is used to develop a flowsheet such that additional sludge vitrification canisters and other negative system impacts are minimized. Sensitivity analyses are used to assess the processability impacts from variations in the sludge/quantities of acids.

  9. Carbonate dissolution rates at the deep ocean floor

    NASA Astrophysics Data System (ADS)

    Boudreau, Bernard P.

    2013-02-01

    This paper reexamines experimental data on the seawater dissolution of CaCO3-bearing sediment beds to establish that the dependence of the calcite dissolution rate is linearly dependent on the calcite saturation state of the overlying water. This linearity is inherent to the original data and is not the result of an error in the solubility product for calcite. A comparison between these linear kinetics and the rate of solute transport across the benthic boundary layer further reveals that the overall rate of dissolution at ocean depths below the saturation horizon is controlled by boundary layer transfer. A carbonate mass-balance model for the sediment-water interface, which includes both kinetics and boundary layer effects, predictively reproduces the currently observed CaCO3 depth distribution for two test areas in the oceans. These findings allow important simplifications in modeling CO2 neutralization in the oceans.

  10. On the present and future of dissolution-DNP

    NASA Astrophysics Data System (ADS)

    Ardenkjaer-Larsen, Jan Henrik

    2016-03-01

    Dissolution-DNP is a method to create solutions of molecules with nuclear spin polarization close to unity. The many orders of magnitude signal enhancement have enabled many new applications, in particular in vivo MR metabolic imaging. The method relies on solid state dynamic nuclear polarization at low temperature followed by a dissolution to produce the room temperature solution of highly polarized spins. This work describes the present and future of dissolution-DNP in the mind of the author. The article describes some of the current trends in the field as well as outlines some of the areas where new ideas will make an impact. Most certainly, the future will take unpredicted directions, but hopefully the thoughts presented here will stimulate new ideas that can further advance the field.

  11. Dissolution and growth of spinel crystals in a borosilicate glass

    SciTech Connect

    Alton, Jesse; Plaisted, Trevor J.; Hrma, Pavel R. )

    2002-06-01

    The rate of dissolution and growth of settling crystals of spinel was measured optically in a borosilicate melt that was pre-heated at a temperature above liquidus to erase the effects of previous history. The Hixson-Crowell equation, which is based on Fick's first law, was used to determine mass-transfer coefficients (kH) for dissolution and growth; both were found to fit the same Arrhenius function of temperature (T). An attempt was made to estimate the diffusion coefficient (D) and the concentration-boundary-layer thickness (d). The calculated values of d compared well with experimental results and observations. The D vs. T function was similar to a literature function obtained for the dissolution of magnetite in sodium disilicate glass.

  12. Dissolution dynamics of thin films measured by optical reflectance

    NASA Astrophysics Data System (ADS)

    Punckt, Christian; Aksay, Ilhan A.

    2009-12-01

    Measuring the dissolution dynamics of thin films in situ both with spatial and temporal resolution can be a challenging task. Available methods such as scanning electrochemical microscopy rely on scanning the specimen and are intrinsically slow. We developed a characterization technique employing only an optical microscope, a digital charge coupled device camera, and a computer for image processing. It is capable of detecting dissolution rates of the order of nm/min and has a spatial and temporal resolution which is limited by the imaging and recording setup. We demonstrate the capabilities of our method by analyzing the electrochemical dissolution of copper thin films on gold substrates in a mild hydrochloric acid solution. Due to its simplicity, our technique can be implemented in any laboratory and can be applied to a variety of systems such as thin film sensors or passive coatings.

  13. A model for reaction-assisted polymer dissolution in LIGA.

    SciTech Connect

    Larson, Richard S.

    2004-05-01

    A new chemically-oriented mathematical model for the development step of the LIGA process is presented. The key assumption is that the developer can react with the polymeric resist material in order to increase the solubility of the latter, thereby partially overcoming the need to reduce the polymer size. The ease with which this reaction takes place is assumed to be determined by the number of side chain scissions that occur during the x-ray exposure phase of the process. The dynamics of the dissolution process are simulated by solving the reaction-diffusion equations for this three-component, two-phase system, the three species being the unreacted and reacted polymers and the solvent. The mass fluxes are described by the multicomponent diffusion (Stefan-Maxwell) equations, and the chemical potentials are assumed to be given by the Flory-Huggins theory. Sample calculations are used to determine the dependence of the dissolution rate on key system parameters such as the reaction rate constant, polymer size, solid-phase diffusivity, and Flory-Huggins interaction parameters. A simple photochemistry model is used to relate the reaction rate constant and the polymer size to the absorbed x-ray dose. The resulting formula for the dissolution rate as a function of dose and temperature is ?t to an extensive experimental data base in order to evaluate a set of unknown global parameters. The results suggest that reaction-assisted dissolution is very important at low doses and low temperatures, the solubility of the unreacted polymer being too small for it to be dissolved at an appreciable rate. However, at high doses or at higher temperatures, the solubility is such that the reaction is no longer needed, and dissolution can take place via the conventional route. These results provide an explanation for the observed dependences of both the dissolution rate and its activation energy on the absorbed dose.

  14. Principles of Calcite Dissolution in Human and Artificial Otoconia

    PubMed Central

    Walther, Leif Erik; Blödow, Alexander; Buder, Jana; Kniep, Rüdiger

    2014-01-01

    Human otoconia provide mechanical stimuli to deflect hair cells of the vestibular sensory epithelium for purposes of detecting linear acceleration and head tilts. During lifetime, the volume and number of otoconia are gradually reduced. In a process of degeneration morphological changes occur. Structural changes in human otoconia are assumed to cause vertigo and balance disorders such as benign paroxysmal positional vertigo (BPPV). The aim of this study was to investigate the main principles of morphological changes in human otoconia in dissolution experiments by exposure to hydrochloric acid, EDTA, demineralized water and completely purified water respectively. For comparison reasons artificial (biomimetic) otoconia (calcite gelatin nanocomposits) and natural calcite were used. Morphological changes were detected in time steps by the use of environmental scanning electron microscopy (ESEM). Under in vitro conditions three main dissolution mechanisms were identified as causing characteristic morphological changes of the specimen under consideration: pH drops in the acidic range, complex formation with calcium ions and changes of ion concentrations in the vicinity of otoconia. Shifts in pH cause a more uniform reduction of otoconia size (isotropic dissolution) whereas complexation reactions and changes of the ionic concentrations within the surrounding medium bring about preferred attacks at specific areas (anisotropic dissolution) of human and artificial otoconia. Owing to successive reduction of material, all the dissolution mechanisms finally produce fragments and remnants of otoconia. It can be assumed that the organic component of otoconia is not significantly attacked under the given conditions. Artificial otoconia serve as a suitable model system mimicking chemical attacks on biogenic specimens. The underlying principles of calcite dissolution under in vitro conditions may play a role in otoconia degeneration processes such as BPPV. PMID:25048115

  15. Selective Electrocatalytic Activity of Ligand Stabilized Copper Oxide Nanoparticles

    SciTech Connect

    Kauffman, Douglas R; Ohodnicki, Paul R; Kail, Brian W; Matranga, Christopher

    2011-01-01

    Ligand stabilization can influence the surface chemistry of Cu oxide nanoparticles (NPs) and provide unique product distributions for electrocatalytic methanol (MeOH) oxidation and CO{sub 2} reduction reactions. Oleic acid (OA) stabilized Cu{sub 2}O and CuO NPs promote the MeOH oxidation reaction with 88% and 99.97% selective HCOH formation, respectively. Alternatively, CO{sub 2} is the only reaction product detected for bulk Cu oxides and Cu oxide NPs with no ligands or weakly interacting ligands. We also demonstrate that OA stabilized Cu oxide NPs can reduce CO{sub 2} into CO with a {approx}1.7-fold increase in CO/H{sub 2} production ratios compared to bulk Cu oxides. The OA stabilized Cu oxide NPs also show 7.6 and 9.1-fold increases in CO/H{sub 2} production ratios compared to weakly stabilized and non-stabilized Cu oxide NPs, respectively. Our data illustrates that the presence and type of surface ligand can substantially influence the catalytic product selectivity of Cu oxide NPs.

  16. Effects of alteration product precipitation on glass dissolution

    SciTech Connect

    Strachan, Denis M.; Neeway, James J.

    2014-06-01

    Understanding the mechanisms that control the durability of nuclear waste glass is paramount if reliable models are to be constructed so that the glass dissolution rate in a given geological repository can be calculated. Presently, it is agreed that (boro)silicate glasses dissolve in water at a rate dependent on the solution concentration of orthosilicic acid (H4SiO4) with higher [H4SiO4] leading to lower dissolution rates. Once the reaction has slowed as a result of the buildup of H4SiO4, another increase in the rate has been observed that corresponds to the precipitation of certain silica-bearing alteration products. However, it has also been observed that the concentration of silica-bearing solution species does not significantly decrease, indicating saturation, while other glass tracer elements concentrations continue to increase, indicating that the glass is still dissolving. In this study, we have used the Geochemist’s Workbench code to investigate the relationship between glass dissolution rates and the precipitation rate of a representative zeolitic silica-bearing alteration product, analcime [Na(AlSi2O6)∙H2O]. To simplify the calculations, we suppressed all alteration products except analcime, gibbsite (Al(OH)3), and amorphous silica. The pseudo-equilibrium-constant matrix for amorphous silica was substituted for the glass pseudo-equilibrium-constant matrix because it has been shown that silicate glasses act as a silica-only solid with respect to kinetic considerations. In this article, we present the results of our calculations of the glass dissolution rate at different values for the analcime precipitation rate constant and the effects of varying the glass dissolution rate constant at a constant analcime precipitation rate constant. From the simulations we conclude, firstly, that the rate of glass dissolution is dependent on the kinetics of

  17. Illite Dissolution Rates and Equation (100 to 280 dec C)

    DOE Data Explorer

    Carroll, Susan

    2014-10-17

    The objective of this suite of experiments was to develop a useful kinetic dissolution expression for illite applicable over an expanded range of solution pH and temperature conditions representative of subsurface conditions in natural and/or engineered geothermal reservoirs. Using our new data, the resulting rate equation is dependent on both pH and temperature and utilizes two specific dissolution mechanisms (a “neutral” and a “basic” mechanism). The form of this rate equation should be easily incorporated into most existing reactive transport codes for to predict rock-water interactions in EGS shear zones.

  18. Experimental observations of dolomite dissolution in geologic carbon sequestration conditions

    NASA Astrophysics Data System (ADS)

    Luhmann, A. J.; Kong, X.; Tutolo, B. M.; Saar, M. O.; Seyfried, W. E.

    2013-12-01

    One sequestration scenario proposed to reduce CO2 emissions involves injecting CO2 into saline formations or hydrocarbon reservoirs, where dolomite frequently occurs. To better understand fluid-mineral interactions in these sequestration settings, we have conducted a series of single-pass, flow-through experiments on dolomite core samples with CO2-bearing brine. An important component of the experimental design was to maintain the fabric of the rock so as to more accurately simulate fluid flow in natural dolomite-bearing systems. Seven experiments were conducted at 100°C and a pore-fluid pressure of 150 bars with a fluid containing 1 molal NaCl and 0.6 molal dissolved CO2. Flow rates ranged from 0.01 to 1 ml/min. Each experiment was terminated before dissolution breakthrough, but permeability increased by approximately an order of magnitude for all experiments. In general, Ca and Mg concentrations were initially high, but then decreased with reaction progress. We hypothesize that time-dependent changes in fluid chemistry reflect reduction in reactive surface area. Fluid chemistry also indicates preferential removal of Ba, Mn, and Sr with respect to Ca and Mg. In the extreme case, 70% of the Ba was removed from one core, while only 3% of the Ca, Mg, or the entire core mass was removed by dissolution. Ongoing work is focused on identifying elemental distributions throughout the rock to better understand the dissolution process. With fluid chemistry and BET surface area, we model dissolution rate as a function of core length using reactive transport simulations and compare our whole rock, far from equilibrium dissolution rates with analogous data reported in the literature. Finally, X-ray computed tomography images enable reconstructions of dissolution patterns, and they are being used to explore the effect of pore space heterogeneity on flow path development. Geologic carbon sequestration in dolomite will produce significant dissolution at the brine/CO2 interface

  19. Spent fuel dissolution studies FY 1991 to 1994

    SciTech Connect

    Gray, W.J.; Wilson, C.N.

    1995-12-01

    Dissolution and transport as a result of groundwater flow are generally accepted as the primary mechanisms by which radionuclides from spent fuel placed in a geologic repository could be released to the biosphere. To help provide a source term for performance assessment calculations, dissolution studies on spent fuel and unirradiated uranium oxides have been conducted over the past few years at Pacific Northwest National Laboratory (PNNL) in support of the Yucca Mountain Site Characterization Project. This report describes work for fiscal years 1991 through 1994. The objectives of these studies and the associated conclusions, which were based on the limited number of tests conducted so far, are described in the following subsections.

  20. A contained sealed reflux dissolution apparatus for plutonium materials

    SciTech Connect

    Oldham, R.D.; Mitchell, W.G.; Leahy, C.K.; Narayanan, U.I.; Lewis, K.

    1991-12-01

    A containment apparatus has been designed and a procedure developed which permits the overnight operation in a tornado prone area of the sealed reflux dissolution system for the dissolution of hard-to-dissolve plutonium containing materials. A historical review of the development of the apparatus and the procedure used at the New Brunswick Laboratory is presented. The detailed operating procedure, the engineering drawings necessary to fabricate the apparatus, and the Safety Analysis Report containing a worst-case, single occurrence failure analysis are provided in the Appendices. 3 refs.

  1. Mesogenetic dissolution: Its role in porosity development in carbonate reservoirs

    SciTech Connect

    Mazzullo, S.J. ); Harris, P.M. )

    1992-05-01

    Models of porosity formation in carbonate rocks have stressed subaerial exposure and attendant shallow meteoric diagenesis. Porosity formation also occurs in deep-burial, or mesogenetic, settings as a result of dissolution enlargement of preexisting pores (porosity enhancement) and creation of new pore systems. Brines charged with organic acids, carbon dioxide, and/or hydrogen sulfide derived from organic matter diagenesis and thermochemical sulfate reduction are the likely fluids causing significant mesogenetic dissolution. Enhanced and newly created mesogenetic pore types can mimic pore types formed in shallow meteoric environments, and therefore, the mesogenetic origin of some porosity may go unrecognized.

  2. Biodegradation and dissolution of polyaromatic hydrocarbons by Stenotrophomonas sp.

    PubMed

    Tiwari, Bhagyashree; Manickam, N; Kumari, Smita; Tiwari, Akhilesh

    2016-09-01

    The aim of this work was to study the biodegradation capabilities of a locally isolated bacterium, Stenotrophomonas sp. strain IITR87 to degrade the polycyclic aromatic hydrocarbons and also check the preferential biodegradation of polycyclic aromatic hydrocarbons (PAHs). From preferential substrate degradation studies, it was found that Stenotrophomonas sp. strain IITR87 first utilized phenanthrene (three membered ring), followed by pyrene (four membered ring), then benzo[α]pyrene (five membered ring). Dissolution study of PAHs with surfactants, rhamnolipid and tritonX-100 showed that the dissolution of PAHs increased in the presence of surfactants. PMID:27342606

  3. Intramolecular Entropy and Size-Dependent Solution Properties of Nanocrystal-Ligands Complexes.

    PubMed

    Yang, Yu; Qin, Haiyan; Peng, Xiaogang

    2016-04-13

    CdSe-stearates nanocrystal-ligands complex as a whole possess strongly temperature- and size-dependent yet well-defined solubility in small organic solvents, which shows little solvent effects as long as the complexes remained intact. A quantitative thermodynamic model is developed to describe such solubility behavior, which differs fundamentally from conventional models for micron colloids. The model reveals that the conformation entropy of the n-alkanoate chain released in dissolution greatly stabilize the colloidal solution but the strong chain-chain interdigitation between adjacent particles in solid diminishes the solubility. These understandings result in "entropic ligands" (see full disclosure in another report (10.1021/acs.nanolett.6b00730)) as the universal means to battle processability challenges of colloidal nanocrystals. PMID:26923516

  4. Oral medication delivery in impaired swallowing: thickening liquid medications for safe swallowing alters dissolution characteristics.

    PubMed

    Manrique, Yady J; Sparkes, Arron M; Cichero, Julie A Y; Stokes, Jason R; Nissen, Lisa M; Steadman, Kathryn J

    2016-09-01

    Acetaminophen (paracetamol) is available in a wide range of oral formulations designed to meet the needs of the population across the age-spectrum, but for people with impaired swallowing, i.e. dysphagia, both solid and liquid medications can be difficult to swallow without modification. The effect of a commercial polysaccharide thickener, designed to be added to fluids to promote safe swallowing by dysphagic patients, on rheology and acetaminophen dissolution was tested using crushed immediate-release tablets in water, effervescent tablets in water, elixir and suspension. The inclusion of the thickener, comprised of xanthan gum and maltodextrin, had a considerable impact on dissolution; acetaminophen release from modified medications reached 12-50% in 30 min, which did not reflect the pharmacopeia specification for immediate release preparations. Flow curves reflect the high zero-shear viscosity and the apparent yield stress of the thickened products. The weak gel nature, in combination with high G' values compared to G'' (viscoelasticity) and high apparent yield stress, impact drug release. The restriction on drug release from these formulations is not influenced by the theoretical state of the drug (dissolved or dispersed), and the approach typically used in clinical practice (mixing crushed tablets into pre-prepared thickened fluid) cannot be improved by altering the order of incorporation or mixing method. PMID:26857812

  5. Dissolution behavior and early bone apposition of calcium phosphate-coated machined implants

    PubMed Central

    Hwang, Ji-Wan; Lee, Eun-Ung; Lee, Jung-Seok; Jung, Ui-Won; Lee, In-Seop

    2013-01-01

    Purpose Calcium phosphate (CaP)-coated implants promote osseointegration and survival rate. The aim of this study was to (1) analyze the dissolution behavior of the residual CaP particles of removed implants and (2) evaluate bone apposition of CaP-coated machined surface implants at the early healing phase. Methods Mandibular premolars were extracted from five dogs. After eight weeks, the implants were placed according to drilling protocols: a nonmobile implant (NI) group and rotational implant (RI) group. For CaP dissolution behavior analysis, 8 implants were removed after 0, 1, 2, and 4 weeks. The surface morphology and deposition of the coatings were observed. For bone apposition analysis, block sections were obtained after 1-, 2-, and 4-week healing periods and the specimens were analyzed. Results Calcium and phosphorus were detected in the implants that were removed immediately after insertion, and the other implants were composed mainly of titanium. There were no notable differences between the NI and RI groups in terms of the healing process. The bone-to-implant contact and bone density in the RI group showed a remarkable increase after 2 weeks of healing. Conclusions It can be speculated that the CaP coating dissolves early in the healing phase and chemically induces early bone formation regardless of the primary stability. PMID:24455442

  6. Efficient pseudo-enantiomeric carbohydrate olefin ligands.

    PubMed

    Grugel, Holger; Albrecht, Fabian; Minuth, Tobias; Boysen, Mike M K

    2012-07-20

    Highly efficient pseudo-enantiomeric olefin ligands were designed from D-glucose and D-galactose. These ligands yield consistently excellent levels of enantioselectivity in Rh(I)-catalyzed 1,4-additions of aryl- and alkenylboronic acids to achiral enones and high diastereoselectivity with chiral substrates. Contrary to established olefin ligands, they are obtained enantiomerically pure via short syntheses without racemic resolution steps, making them a valuable addition to the arsenal of chiral ligands with olefinic donor sites. PMID:22780685

  7. Kinetically controlled dissolution of UO{sub 2} (s) under oxidizing conditions. A combined dissolution-oxidation model

    SciTech Connect

    Casas, I.; Gimenez, J.; Marti, V.; Torrero, M.E.; De Pablo, J.

    1993-12-31

    The release of uranium from three samples of UO{sub 2} (s) with different particle sizes (100-300 {mu}m, 900-1000 {mu}m, pellet) has been studied as a function of time. In all cases, the same pH, ionic medium, temperature, and oxygen partial pressure were used. Two distinctive trends were observed in three cases, with a relatively fast initial uranium release followed, after 10-15 days, by a slower dissolution rate. The experiments were continued during 200 days; no change in the second dissolution rate was noticed. The uranium released as a function of time has been successfully fitted with a mathematical expression which combines an oxidation-dissolution mechanism.

  8. Revisiting classical silicate dissolution rate laws under hydrothermal conditions

    NASA Astrophysics Data System (ADS)

    Pollet-Villard, Marion; Daval, Damien; Saldi, Giuseppe; Knauss, Kevin; Wild, Bastien; Fritz, Bertrand

    2015-04-01

    In the context of geothermal energy, the relative intensities of primary mineral leaching and secondary mineral precipitation can affect porosity and permeability of the reservoir, thereby influencing its hydraulic performance and the efficiency of the geothermal power station. That is why the prediction of reaction kinetics of fluid/rock interactions represents a critical issue in this context. Moreover, in several geothermal systems such as the one of Soultz-sous-Forêts (Alsace, France), the circulation of aqueous fluids induces only modest modifications of their chemical composition. Therefore, fluid-rock interactions take place at close-to-equilibrium conditions, where the rate-affinity relations are poorly known and intensively debated [1]. To describe more precisely the dissolution processes, our strategy consists in investigating the dissolution of the main cleavages of K-spar minerals (one of the prevalent primary minerals in the reservoir of Soultz-sous-Forêts geothermal system) over a wide range of Gibbs free energy (ΔG) conditions. The aims are to decipher the impact of crystallographic orientation and microstructural surface modifications on the dissolution kinetics and to propose a relation between K-spar dissolution rate and ΔG. Our experimental work relies on a coupled approach which combines classical experiments of K-spar dissolution monitored by aqueous chemical analyses (ICP-AES) and innovative techniques of nm- to μm-scale characterization of solid surface (SEM, AFM, VSI) [2]. Our results confirm that K-spar dissolution is an anisotropic process: we measure a tenfold factor between the slowest and the fastest-dissolving surfaces. Moreover, the formation of etch pits on surfaces during their alteration has been evidenced on all of the different faces that have been studied. This complex evolution of the surface topography casts doubt of the relevance of a surface model based on shrinking particles and represents a possible cause of an

  9. The Role of Endogenous Epidermal Growth Factor Receptor Ligands in Mediating Corneal Epithelial Homeostasis

    PubMed Central

    Peterson, Joanne L.; Phelps, Eric D.; Doll, Mark A.; Schaal, Shlomit; Ceresa, Brian P.

    2014-01-01

    Purpose. To provide a comprehensive study of the biological role and therapeutic potential of six endogenous epidermal growth factor receptor (EGFR) ligands in corneal epithelial homeostasis. Methods. Kinetic analysis and dose response curves were performed by using in vitro and in vivo wound-healing assays. Biochemical assays were used to determine receptor expression and activity. Human tears were collected and quantitatively analyzed by multianalyte profiling for endogenous EGFR ligands. Results. Epidermal growth factor receptor ligands improved wound closure and activated EGFR, but betacellulin (BTC) was the most efficacious promoter of wound healing in vitro. In contrast, only epidermal growth factor (EGF) promoted wound healing in vivo. Human tears from 25 healthy individuals showed EGFR ligands at these average concentrations: EGF at 2053 ± 312.4 pg/mL, BTC at 207 ± 39.4 pg/mL, heparin-binding EGF at 44 ± 5.8 pg/mL, amphiregulin at 509 ± 28.8 pg/mL, transforming growth factor-α at 84 ± 19 pg/mL, and epiregulin at 52 ± 15 pg/mL. Conclusions. Under unwounded conditions, only EGF was present at concentrations near the ligand's Kd for the receptor, indicating it is the primary mediator of corneal epithelial homeostasis. Other ligands were present but at concentrations 11- to 7500-fold less their Kd, preventing significant ligand binding. Further, the high levels of EGF and its predicted binding preclude receptor occupancy by exogenous ligand and can explain the discrepancy between the in vitro and in vivo data. Therefore, therapeutic use of EGFR ligands may be unpredictable and impractical. PMID:24722692

  10. Evaluation of immunoglobulin adsorption on the hydrophobic charge-induction resins with different ligand densities and pore sizes.

    PubMed

    Lu, Hui-Li; Lin, Dong-Qiang; Gao, Dong; Yao, Shan-Jing

    2013-02-22

    Hydrophobic charge-induction chromatography (HCIC) is a novel technology for antibody purification. The ligand densities and pore properties of HCIC resins have significant effects on the separation behavior of protein, however, the understandings are quite limited. In the present work, new HCIC ligand, 2-mercapto-1-methylimidazole (MMI) was coupled to three agarose matrices with different pore sizes. A series of MMI resins with different ligand density and pore size was prepared by the control of ligand coupling. The adsorption isotherms and kinetics on the series of MMI resins were investigated with bovine serum immunoglobulin as the model IgG, and the effects of salt addition were studied. The Langmuir equation and pore diffusion model were used to fit the experimental data, and the influences of ligand density, pore size and salt addition on the saturated adsorption capacity, the dissociation constant and the effective diffusivity were discussed. It was found that the adsorption capacities and the effective pore diffusion coefficient increased with the increase of ligand density and pore size. The effects of salt addition on the adsorption behaviors were dependent on the ligand density. For low ligand density the IgG adsorption was salt-promoted, while the resins with high ligand density showed a salt-independent property. The results indicated that for a given protein the ligand density and pore size of HCIC resins should be optimized for improving the protein adsorption. PMID:23336945

  11. Combining quantum mechanical ligand conformation analysis and protein modeling to elucidate GPCR-ligand binding modes.

    PubMed

    Schultes, Sabine; Engelhardt, Harald; Roumen, Luc; Zuiderveld, Obbe P; Haaksma, Eric E J; de Esch, Iwan J P; Leurs, Rob; de Graaf, Chris

    2013-01-01

    SAR beyond protein-ligand interactions: By combining structure-affinity relationships, protein-ligand modeling studies, and quantum mechanical calculations, we show that ligand conformational energies and basicity play critical roles in ligand binding to the histamine H4 receptor, a GPCR that plays a key role in inflammation. PMID:23161844

  12. Ligand substitution behavior of Ru6(mu6-C)(CO)17 with unsaturated diphosphines: facile capping of a polyhedral face and photochemically promoted P C bond cleavage in the cluster Ru6(mu6-C)(CO)14(mu3-bpcd)

    SciTech Connect

    Kandala, Srikanth; Hammons, Casey; Watson, William H.; Wang, Xiaoping; Richmond, Michael G.

    2010-01-01

    The ligand substitution chemistry of the hexaruthenium cluster Ru-6(mu(6)-C)(CO)(17) (1) with several unsaturated diphosphine ligands has been investigated. Thermolysis of 1 with (Z)-Ph2PCH=CHPPh2 (dppen) furnishes the new cluster compounds Ru-5(mu(5)-C)(CO)(12)(mu(3)-dppen) (2), Ru-6(mu(6)-C)(CO)(14)(mu(3)-dppen) (3), and Ru-6(mu(6)-C)(CO)(12)(mu(3)-dppen)(mu-dppen) (4). Clusters 2 and 3 are also obtained when a mixture of 1 and dppen is treated with the oxidative-decarbonylation reagent Me3NO. Thermolysis or Me3NO activation of 1 in the presence of 4,5-bis(diphenylphosphino)-4-cyclopenten- 1,3-dione (bpcd) yields Ru-6(mu(6)-C)(CO)(14)(mu(3)-bpcd) (4) as the sole observable product. Near-UV irradiation of 4 leads to P-C bond cleavage and the formation of phosphido-bridged cluster Ru-6(mu(6)-C)(CO)(13)[mu(3)-C=C(PPh2)C(O)CH2C(O)](mu-PPh2) (6) in essentially quantitative yield. The reaction between 1 and the ligand 3,4-bis(diphenylphosphino)-5-methoxy-2(5H)-furanone (bmf) leads to the formation of Ru-6(mu(6)-C)(CO)(14)(mu(3)-bmf) (7), which exists as a single diastereomer in solution as shown by H-1 and P-31 NMR spectroscopy. The molecular structures and the binding mode of the ancillary diphosphine ligand(s) in 2-7 have all been established by X-ray diffraction analyses. The solid-state structure of 7 reveals that the chiral bmf ligand caps one of the metallic faces stereospecifically with the 5-methoxy moiety oriented distal or trans relative to the Ru-6 polyhedral core. The new substitution products are discussed relative to the products obtained from 1 and the related diphosphine ligands dppm, dppe, dppf, and dppbz.

  13. Ligand chain length conveys thermochromism.

    PubMed

    Ganguly, Mainak; Panigrahi, Sudipa; Chandrakumar, K R S; Sasmal, Anup Kumar; Pal, Anjali; Pal, Tarasankar

    2014-08-14

    Thermochromic properties of a series of non-ionic copper compounds have been reported. Herein, we demonstrate that Cu(II) ion with straight-chain primary amine (A) and alpha-linolenic (fatty acid, AL) co-jointly exhibit thermochromic properties. In the current case, we determined that thermochromism becomes ligand chain length-dependent and at least one of the ligands (A or AL) must be long chain. Thermochromism is attributed to a balanced competition between the fatty acids and amines for the copper(II) centre. The structure-property relationship of the non-ionic copper compounds Cu(AL)2(A)2 has been substantiated by various physical measurements along with detailed theoretical studies based on time-dependent density functional theory. It is presumed from our results that the compound would be a useful material for temperature-sensor applications. PMID:24943491

  14. Ligand regulation of a constitutively dimeric EGF receptor.

    PubMed

    Freed, Daniel M; Alvarado, Diego; Lemmon, Mark A

    2015-01-01

    Ligand-induced receptor dimerization has traditionally been viewed as the key event in transmembrane signalling by epidermal growth factor receptors (EGFRs). Here we show that the Caenorhabditis elegans EGFR orthologue LET-23 is constitutively dimeric, yet responds to its ligand LIN-3 without changing oligomerization state. SAXS and mutational analyses further reveal that the preformed dimer of the LET-23 extracellular region is mediated by its domain II dimerization arm and resembles other EGFR extracellular dimers seen in structural studies. Binding of LIN-3 induces only minor structural rearrangements in the LET-23 dimer to promote signalling. Our results therefore argue that EGFR can be regulated by allosteric changes within an existing receptor dimer--resembling signalling by insulin receptor family members, which share similar extracellular domain compositions but form covalent dimers. PMID:26060020

  15. Ligand regulation of a constitutively dimeric EGF receptor

    NASA Astrophysics Data System (ADS)

    Freed, Daniel M.; Alvarado, Diego; Lemmon, Mark A.

    2015-06-01

    Ligand-induced receptor dimerization has traditionally been viewed as the key event in transmembrane signalling by epidermal growth factor receptors (EGFRs). Here we show that the Caenorhabditis elegans EGFR orthologue LET-23 is constitutively dimeric, yet responds to its ligand LIN-3 without changing oligomerization state. SAXS and mutational analyses further reveal that the preformed dimer of the LET-23 extracellular region is mediated by its domain II dimerization arm and resembles other EGFR extracellular dimers seen in structural studies. Binding of LIN-3 induces only minor structural rearrangements in the LET-23 dimer to promote signalling. Our results therefore argue that EGFR can be regulated by allosteric changes within an existing receptor dimer--resembling signalling by insulin receptor family members, which share similar extracellular domain compositions but form covalent dimers.

  16. Hypocretin ligand deficiency in narcolepsy: recent basic and clinical insights.

    PubMed

    Ritchie, Cayde; Okuro, Masashi; Kanbayashi, Takashi; Nishino, Seiji

    2010-05-01

    Narcolepsy is a chronic sleep disorder characterized by excessive daytime sleepiness, cataplexy, hypnagogic hallucinations, and sleep paralysis. Both sporadic and familial forms exist in humans. Recently, the major pathophysiology of human narcolepsy was indicated, based on discovery, through animal study, of narcolepsy genes involved in the pathology of hypocretin/orexin ligand and its receptor. Hypocretin ligand deficiency is found in most patients with narcolepsy with cataplexy. This deficiency likely is the result of postnatal cell death of hypocretin neurons, and involvement of autoimmune mechanisms is suggested. Hypocretin deficiency also is found in symptomatic narcolepsy and excessive daytime sleepiness with neurologic conditions, including immune-mediated neurologic disorders. These findings have significant clinical relevance and promote understanding of hypocretin cell death mechanisms. Already, discoveries in humans have led to a new diagnostic test for narcolepsy. Currently, hypocretin replacement therapy has emerged as a promising therapeutic option, and experiments using gene therapy and cell transplantation are in progress. PMID:20425033

  17. Little Reason for Being: A Case of School District Dissolution.

    ERIC Educational Resources Information Center

    Ellis, Pam

    In 1980, Tonnelly Central School District became the first school district in New York State to be dissolved pursuant to Section 1505 of Education Law, marking the first use of dissolution and annexation as a means by which to address the programmatic and management problems encountered in the operation of a central school district. Problems faced…

  18. CHEMICALLY-ENHANCED DISSOLUTION AND MOBILIZATION OF RESIDUAL CONTAMINANTS

    EPA Science Inventory

    Pore-scale micromodels and a computer-controlled imaging system will be used to examine fluid dynamics and phase behavior during chemically-enhanced NAPL dissolution and mobilization. Mechanistic insights gained at this microscopic level will be used to help explain observations...

  19. Divorce and Union Dissolution: Reverberations over Three Generations

    ERIC Educational Resources Information Center

    Connidis, Ingrid Arnet

    2003-01-01

    High divorce rates over the past 40 years have affected multiple generations and have long-term consequences for family relationships. This article applies a life course perspective as it explores the reverberation of relationship dissolution beyond the nuclear family. Qualitative data from a study involving 86 adults from 10 three-generation…

  20. Liquisolid Tablets for Dissolution Enhancement of a Hypolipidemic Drug

    PubMed Central

    Patel, D. S.; Pipaliya, R. M.; Surti, Naazneen

    2015-01-01

    This investigation was aimed to improve the dissolution rate of the poorly soluble drug lovastatin, by formulating it as a liquisolid compact. Different liquisolid compacts were prepared using mathematical formulae to calculate the required quantities of powder and liquid ingredients to produce acceptably flowable and compressible admixture. Avicel PH 200, Cab-O-Sil, sodium starch glycolate and PEG 400 were employed as carrier, coating material, disintegrant and non-volatile liquid vehicle, respectively. The various drug to liquid and carrier to coating ratio were used to prepare liquisolid compacts. The formulated liquisolid tablets were evaluated for weight variation, hardness, drug content, friability and disintegration time. The in vitro release characteristics of the drug from tablets formulated by direct compression and liquisolid technique were compared in two different dissolution media. The tableting properties of the liquisolid compacts were within the acceptable limits and drug release rates were distinctly higher as compared to directly compressed tablets. The FTIR spectra showed no interaction between drug-excipient and disappearance of the characteristic absorption band of lovastatin in liquisolid formulations could be attributed to the formation of hydrogen bonding between the drug and liquid vehicle, which resulted in dissolution enhancement. Thus, the liquisolid technique was found to be a promising approach for improving the dissolution of a poorly soluble drug like lovastatin. PMID:26180274

  1. Students' Spontaneous Use of a Particulate Model for Dissolution.

    ERIC Educational Resources Information Center

    Selley, Nicholas J.

    2001-01-01

    Studies students aged 12 to 14 years (n=217) representing a wide ability range. Analyzes the responses of participants to the dissolution of a solid in both cold and warm water. Findings have implications for the teaching of all science theory but especially for conveying the purpose of models and the process of modeling. (Contains 29 references.)…

  2. Modification of fracture surfaces by dissolution. Part II

    SciTech Connect

    Johnson, B.

    1983-01-01

    This study focuses upon how and to what extent dissolution related fluid/rock interactions modify the morphology and roughness of surfaces on Sioux Quartzite. Dissolution experiments consisted of reacting small discs of Sioux Quartzite in sealed gold capsules containing either distilled water or 0.05 N to 4.0 N aqueous solutions of Na/sub 2/CO/sub 3/. Samples were reacted at 200/sup 0/C and 20 to 30 MPa fluid pressures for 2 to 5 days. Two markedly different starting surface textures were used: polished, optically flat surfaces and tensile fracture surfaces. An exploratory experiment also was performed to assess the occurrence of a pressure solution phenomenon on a polished quartzite surface at contact regions of indenting quartz sand grains. Scanning electron microscopy studies indicate progressive increases in the amount of dissolution produced significant changes of surface roughness for both initial surface textures. Surface roughness increased measurably, with the initially polished surfaces exhibiting the more dramatic changes. The pressure solution experiments did not produce definite results, but several surface features are suggestive of dissolution enhancement at load carrying contacts. 9 refs., 10 figs.

  3. 21 CFR 343.90 - Dissolution and drug release testing.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 5 2012-04-01 2012-04-01 false Dissolution and drug release testing. 343.90 Section 343.90 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) DRUGS FOR HUMAN USE INTERNAL ANALGESIC, ANTIPYRETIC, AND ANTIRHEUMATIC DRUG PRODUCTS FOR OVER-THE-COUNTER HUMAN USE Testing Procedures §...

  4. Dissolution and characterization of HEV NiMH batteries.

    PubMed

    Larsson, Kristian; Ekberg, Christian; Ødegaard-Jensen, Arvid

    2013-03-01

    Metal recovery is an essential part of the recycling of hybrid electric vehicle battery waste and the first step in a hydrometallurgical treatment is dissolution of the solid material. The properties of separated battery electrode materials were investigated. Focus was put on both the solid waste and then the dissolution behaviour. The cathode contains metallic nickel that remains undissolved when utilizing non-oxidizing conditions such as hydrochloric or sulphuric acid in combination with a low oxygen atmosphere. In these conditions the cathode active electrode material is fully dissolved. Not dissolving the nickel metal saves up to 37% of the acid consumption for the cathode electrode material. In the commonly used case of oxidizing conditions the nickel metal dissolves and a cobalt-rich phase remains undissolved from the cathode active material. For the anode material a complete and rapid dissolution can be achieved at mild conditions with hydrochloric, nitric or sulphuric acid. Optimal parameters for all cases of dissolution was pH 1 with a reaction time of approximately ≥ 20,000 s. PMID:22796014

  5. Coming Apart: A Model of the Marital Dissolution Decision.

    ERIC Educational Resources Information Center

    Edwards, John N.; Saunders, Janice M.

    1981-01-01

    Proposes a social-psychological model of the dissolution decision in marriage based on prior theoretical formulations. Sequential in character and emphasizing the duality of the marital relationship, the model modifies and refines previous theoretical efforts, and seeks to extend their explanatory power by incorporating various principles of…

  6. Liquisolid Tablets for Dissolution Enhancement of a Hypolipidemic Drug.

    PubMed

    Patel, D S; Pipaliya, R M; Surti, Naazneen

    2015-01-01

    This investigation was aimed to improve the dissolution rate of the poorly soluble drug lovastatin, by formulating it as a liquisolid compact. Different liquisolid compacts were prepared using mathematical formulae to calculate the required quantities of powder and liquid ingredients to produce acceptably flowable and compressible admixture. Avicel PH 200, Cab-O-Sil, sodium starch glycolate and PEG 400 were employed as carrier, coating material, disintegrant and non-volatile liquid vehicle, respectively. The various drug to liquid and carrier to coating ratio were used to prepare liquisolid compacts. The formulated liquisolid tablets were evaluated for weight variation, hardness, drug content, friability and disintegration time. The in vitro release characteristics of the drug from tablets formulated by direct compression and liquisolid technique were compared in two different dissolution media. The tableting properties of the liquisolid compacts were within the acceptable limits and drug release rates were distinctly higher as compared to directly compressed tablets. The FTIR spectra showed no interaction between drug-excipient and disappearance of the characteristic absorption band of lovastatin in liquisolid formulations could be attributed to the formation of hydrogen bonding between the drug and liquid vehicle, which resulted in dissolution enhancement. Thus, the liquisolid technique was found to be a promising approach for improving the dissolution of a poorly soluble drug like lovastatin. PMID:26180274

  7. Solubility and dissolution enhancement strategies: current understanding and recent trends.

    PubMed

    Jain, Shashank; Patel, Niketkumar; Lin, Senshang

    2015-06-01

    Identification of lead compounds with higher molecular weight and lower aqueous solubility has become increasingly prevalent with the advent of high throughput screening. Poor aqueous solubility of these lipophilic compounds can drastically affect the dissolution rate and subsequently the drug absorbed in the systemic circulation, imposing a significant burden of time and money during drug development process. Various pre-formulation and formulation strategies have been applied in the past that can improve the aqueous solubility of lipophilic compounds by manipulating either the crystal lattice properties or the activity coefficient of a solute in solution or both, if possible. However, despite various strategies available in the armor of formulation scientist, solubility issue still remains an overriding problem in the drug development process. It is perhaps due to the insufficient conceptual understanding of solubility and dissolution phenomenon that hinders the judgment in selecting suitable strategy for improving aqueous solubility and/or dissolution rate. This article, therefore, focuses on (i) revisiting the theoretical and mathematical concepts associated with solubility and dissolution, (ii) their application in making rationale decision for selecting suitable pre-formulation and formulation strategies and (iii) the relevant research performed in this field in past decade. PMID:25342479

  8. In vitro dissolution study of atorvastatin binary solid dispersion

    PubMed Central

    Jahan, Rahat; Islam, Md. Saiful; Tanwir, Ahmad; Chowdhury, Jakir Ahmed

    2013-01-01

    The aim of the present study was to improve the solubility and dissolution rate of atorvastatin (ATV), a slight water-soluble drug, by solid dispersion (SD) technique using a hydrophilic carrier Poloxamer 188 (POL188). Physical mixing (PM) and solvent evaporation (SE) method were used to prepare ATV-SD where different drug-carrier ratios were used. Prepared formulations were characterized in their solid state by solubility study; differential scanning calorimetry, scanning electron microscopy, and Fourier transform infrared spectroscopy which demonstrated changes in the formulations supporting the improved solubility. Percent content of POL188 in the SD matrix was found to play the pivotal role in the improvement of dissolution property of ATV. In case of PM, highest enhancement in drug release was found for 1:3 ratio (P < 0.05, ANOVA Single factor) whereas in case of SE, 3:0.5 ratio of ATV-POL188 resulted the maximum enhancement in ATV release (P < 0.05, ANOVA Single factor). Analysis of dissolution data of optimized formula indicated the best fitting with Peppas-Korsmeyer model and the drug release kinetics was fickian diffusion. In conclusion, binary SD prepared by both PM and SE technique using POL188 could be considered as a simple, efficient method to prepare ATV solid dispersions with significant improvement in the dissolution rate. PMID:23662278

  9. Modeling NAPL dissolution from pendular rings in idealized porous media

    EPA Science Inventory

    The rate of NAPL dissolution often governs the clean-up time for subsurface hazardous waste sites. Most formulations for estimating this rate are empirical and assume that the NAPL is the non-wetting fluid. However, field evidence suggests that some waste sites might be organic...

  10. Late Pleistocene carbonate dissolution in the Venezuela Basin, Caribbean Sea

    SciTech Connect

    Cofer-Shabica, N.B.; Peterson, L.C.

    1985-01-01

    Piston cores from water depths greater than 4000 m in the Venezuela Basin (Caribbean Sea) provide continuous late Pleistocene records of carbonate dissolution and accumulation. The authors examination of multiple dissolution indices indicate that, at least for the last 150,000 years, dissolution of carbonate in the Venezuela Basin has been more intense during interglacial than glacial periods, a pattern opposite to more general observations from the deep Atlantic and Gulf of Mexico. By virtue of its shallow sill depth (1815 m), the Venezuela Basin is relatively isolated from the mainstream of Atlantic thermohaline circulation, and presently is filled with homogeneous, relatively warm (3.8/sup 0/C) waters primarily derived from Upper North Atlantic Deep Water. During the last glacial, the enhanced preservation of carbonate in the Venezuela Basin suggests the presence of a less corrosive, more oxygenated water mass in the Atlantic near sill depth. However, this simple interpretations is potentially complicated by past changes in the rain of biogenic materials from surface waters to the deep basin in what must be an essentially closed system below sill depth. Their observations of increased interglacial dissolution may help to explain previously noted discrepancies in the local glacial to interglacial amplitude of delta/sup 18/O variations recorded by coccoliths and planktonic foraminifera.

  11. The dissolution of metallic zinc in D2EHPA

    SciTech Connect

    Chia, L.M.; Neira, M.P.; O`Keefe, T.J.

    1995-07-01

    The direct dissolution of zinc in an organic solution of di-(2-ethylhexyl) phosphoric acid (D2EHPA) and kerosene was studied. The objective was to gain a better understanding of the fundamentals involved in the anodic step of the galvanic stripping process. Results showed that metallic zinc does dissolve spontaneously at ambient temperature by an electrochemical mechanism and the presence of additional oxygen activated the process. When oxygen was removed by prior nitrogen sparging, dissolution did not occur indicating a depolarizing cathodic reaction is necessary. The concentration of water in the organic also affected the rate of dissolution. A factorially designed experiment was made using four variables at two levels selected by evaluating results from previous screening tests. D2EHPA concentration, surface area and agitation were all found to be significant for the values chosen. Temperature was less significant and it was found that zinc dissolution is probably a diffusion or mixed controlled process, as indicated by the calculated activation energy of 6 kcal/mole.

  12. An evaluation of cellular automata applied to ganglia dissolution

    NASA Astrophysics Data System (ADS)

    Johns, M. L.; Gladden, L. F.

    2002-12-01

    The ability of a three-dimensional (3-D) cellular automaton (CA) approach to describe or mimic the dissolution of entrapped octanol ganglia, trapped in a porous media, into a mobile aqueous phase has been directly assessed using detailed 3-D visualizations of the dissolution process, as provided by magnetic resonance imaging (MRI). In the 3-D CA, both time and space are made discrete with the state of each geometric site being updated after each time increment according to the state of all neighboring sites. Good agreement is produced by a direct 3-D comparison of the CA results with the corresponding images of the dissolving ganglia. These experimental images are also supplemented by 3-D velocity maps of the mobile aqueous phase produced using either MRI or by a lattice-Boltzmann simulation. The velocity maps are used to validate the assumption that a consideration of the local velocity field is essential for an accurate description of the ganglia dissolution process. Based on this analysis, an appropriate length scale is proposed for the region, required to be considered in the respective vicinity of each ganglion, when describing their dissolution using a CA approach.

  13. Complete dissolution of trichloroethylene in saturated porous media

    SciTech Connect

    Imhoff, P.T.; Arthur, M.H.; Miller, C.T.

    1998-08-15

    Porous media containing trichloroethylene (TCE) trapped at residual saturation in otherwise water-saturated porous media were flushed with water to asses the dissolution rate of TCE as TCE volumetric fractions approached zero. Careful attention to column design and experimental methods limited the effect of column materials on effluent concentrations. Effluent concentration measurements during TCE dissolution are presented for a glass bead porous medium, a mixed sand, and a treated soil. Effluent concentrations were measured as they decreased below 5 {micro}g/L, the maximum allowable contaminant level, in the glass bead and mixed sand media. Effluent concentrations from columns packed with treated soil were measured down to 20 {micro}g/L. Solvent extraction of the treated soil after the dissolution experiments revealed that extremely small quantities of TCE were retained in this medium. Results from parallel experiments on columns exposed to only aqueous TCE suggest that TCE remaining in the treated soil columns was sorbed to the porous medium. Existing power-law models were capable of describing TCE dissolution in these media, if the exponent on the TCE volume fraction was modified appropriately.

  14. FY 2000 Saltcake Dissolution and Feed Stability Workshop

    SciTech Connect

    Hunt, R.D.; McGinnis, C.P.; Weber, C.F.; Welch, T.D.; Jewett, J.R.

    2000-07-31

    The Tanks Focus Area (TFA) continues to work closely with the Office of River Protection (ORP) to better understand the chemistry involved with the retrieval, transport, and pretreatment of nuclear wastes at Hanford. Since a private contractor is currently responsible for the pretreatment and immobilization activities in this remediation effort, the TFA has concentrated on saltcake dissolution and waste transport at the request of the ORP. Researchers at Hanford have performed a series of dissolution experiments on actual saltcake samples. Staff members at Mississippi State University (MSU) continue to model the dissolution results with the Environmental Simulation Program (ESP), which is used extensively by ORP personnel. Several ways to improve the predictive capabilities of the ESP were identified. Since several transfer lines at Hanford have become plugged, TFA tasks at AEA Technologies, Florida International University (FIU), MSU, and Oak Ridge National Laboratory (ORNL) are investigating the behavior of the supernatants and slurries during transport. A combination of experimental and theoretical techniques is used to study the transport chemistry. This effort is expected to develop process control tools for waste transfer. The results from these TFA tasks were presented to ORP personnel during the FY 2000 Saltcake Dissolution and Feed Stability Workshop, which was held on May 16-17 in Richland, Washington. The minutes from this workshop are provided in this report.

  15. Adolescent Sexuality and the Risk of Marital Dissolution

    ERIC Educational Resources Information Center

    Paik, Anthony

    2011-01-01

    This research investigates whether first sexual intercourse during adolescence is associated with increased risk of first marriage dissolution and tests whether the results are consistent with causal or selection explanations. Drawing on a sample of 3,793 ever-married women from the 2002 National Survey of Family Growth, this study estimated…

  16. Extensive dissolution of live pteropods in the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Bednaršek, N.; Tarling, G. A.; Bakker, D. C. E.; Fielding, S.; Jones, E. M.; Venables, H. J.; Ward, P.; Kuzirian, A.; Lézé, B.; Feely, R. A.; Murphy, E. J.

    2012-12-01

    The carbonate chemistry of the surface ocean is rapidly changing with ocean acidification, a result of human activities. In the upper layers of the Southern Ocean, aragonite--a metastable form of calcium carbonate with rapid dissolution kinetics--may become undersaturated by 2050 (ref. ). Aragonite undersaturation is likely to affect aragonite-shelled organisms, which can dominate surface water communities in polar regions. Here we present analyses of specimens of the pteropod Limacina helicina antarctica that were extracted live from the Southern Ocean early in 2008. We sampled from the top 200m of the water column, where aragonite saturation levels were around 1, as upwelled deep water is mixed with surface water containing anthropogenic CO2. Comparing the shell structure with samples from aragonite-supersaturated regions elsewhere under a scanning electron microscope, we found severe levels of shell dissolution in the undersaturated region alone. According to laboratory incubations of intact samples with a range of aragonite saturation levels, eight days of incubation in aragonite saturation levels of 0.94-1.12 produces equivalent levels of dissolution. As deep-water upwelling and CO2 absorption by surface waters is likely to increase as a result of human activities, we conclude that upper ocean regions where aragonite-shelled organisms are affected by dissolution are likely to expand.

  17. Factors influencing dissolution of carbonaceous materials in liquid iron

    SciTech Connect

    Sun, H.P.

    2005-12-01

    Carbon dissolution into liquid iron was investigated by a kinetic model assuming the rate is limited by interfacial carbon dissociation and mass transfer in the liquid iron. The rate influencing factors and the inter-relations among them were discussed with the aid of the kinetic model.

  18. Solar Radiation Management and Olivine Dissolution Methods in Climate Engineering

    NASA Astrophysics Data System (ADS)

    Kone, S.

    2014-12-01

    An overview of solar radiation management and olivine dissolution methods allows to discuss, comparatively, the benefits and consequences of these two geoengineering techniques. The combination of those two techniques allows to concomitantly act on the two main agents intervening in global warming: solar radiation and carbon dioxide. The earth surface temperature increases due mainly to carbon dioxide (a greenhouse gas) that keeps the solar radiation and causes the global warming. Two complementary methods to mitigate climate change are overviewed: SRM method, which uses injected aerosols, aims to reduce the amount of the inbound solar radiation in atmosphere; and olivine dissolution in water, a key chemical reaction envisaged in climate engineering , aiming to reduce the amount of the carbon dioxide in extracting it from atmosphere. The SRM method works on scenarios of solar radiation decrease and the olivine dissolution method works as a carbon dioxide sequestration method. Olivine dissolution in water impacts negatively on the pH of rivers but positively in counteracting ocean acidification and in transporting the silica in ocean, which has benefits for diatom shell formation.

  19. Pilot-scale tests of HEME and HEPA dissolution process

    SciTech Connect

    Qureshi, Z.H.; Strege, D.K.

    1996-12-31

    A series of pilot-scale demonstration tests for the dissolution of High Efficiency Mist Eliminators (BEME`s) and High Efficiency Particulate Airfilters (BEPA) were performed on a 1/5th linear scale. These filters are to be used in the Defense Waste Processing Facility (DWPF) to decontaminate the effluents from the off-gases generated during the feed preparation process and vitrification. When removed, these radioactively contaminated filters will be dissolved using caustic solutions. As a result of these tests, a simple dissolution process was developed. In this process, the contaminated filter is first immersed in boiling 5% caustic solution for 24 hours and then water is sprayed on the filter. These steps break down the filter first chemically and then mechanically. The metal cage is rinsed and considered low level waste. The dissolved filter is pumpable and mixed with high level waste. Compared to earlier dissolution studies using caustic-acid-caustic solutions, the proposed method represents a 66% savings in cycle time and amount of liquid waste generated. This paper provides the details of filter mockups and results of the dissolution tests.

  20. Dissolution of lime into synthetic coal ash slags

    SciTech Connect

    Elliott, L.; Wang, Shen Mao; Wall, T.; Lucas, J.

    1996-12-31

    One of the alternate processes presently being investigated to produce electrical power from coal is Integrated Gasification Combined Cycle (IGCC). The ash that remains when the coal is gasified in this process, is removed by granulating the molten ash at 1400 - 1500{degrees}C, To reduce the melting temperature of the coal ash to this level, a flux, usually limestone, is added with the cow to the gasifier. The rate of dissolution of the flux is uncertain. This paper reports the investigation of the rate of time dissolution into synthetic coal ashes, consisting of SiO{sub 2}, Al{sub 2}O{sub 3} and CaO. Results previously reported have shown that the free dissolution of fine particles (50-200 {mu}m) is mass transfer controlled. To investigate forced dissolution, a high temperature viscometer was used to rotate a cylinder of lime in the molten slag for a given period. At temperatures between 1450{degrees}C and 1656{degrees}C, reaction products of 3CaO.SiO{sub 2}/3CaOAl{sub 2}O{sub 3}, 2CaO.SiO{sub 2}/3CaO.Al{sub 2}O{sub 3}/12CaO,7Al{sub 2}O{sub 3} form around the lime pellet. The concentration gradient involved in the mass transfer was defined, and initial studies of the diffusion coefficients were completed.

  1. Size effects in MgO cube dissolution.

    PubMed

    Baumann, Stefan O; Schneider, Johannes; Sternig, Andreas; Thomele, Daniel; Stankic, Slavica; Berger, Thomas; Grönbeck, Henrik; Diwald, Oliver

    2015-03-10

    Stability parameters and dissolution behavior of engineered nanomaterials in aqueous systems are critical to assess their functionality and fate under environmental conditions. Using scanning electron microscopy, transmission electron microscopy, and X-ray diffraction, we investigated the stability of cubic MgO particles in water. MgO dissolution proceeding via water dissociation at the oxide surface, disintegration of Mg(2+)-O(2-) surface elements, and their subsequent solvation ultimately leads to precipitation of Mg(OH)2 nanosheets. At a pH ≥ 10, MgO nanocubes with a size distribution below 10 nm quantitatively dissolve within few minutes and convert into Mg(OH)2 nanosheets. This effect is different from MgO cubes originating from magnesium combustion in air. With a size distribution in the range 10 nm ≤ d ≤ 1000 nm they dissolve with a significantly smaller dissolution rate in water. On these particles water induced etching generates (110) faces which, above a certain face area, dissolve at a rate equal to that of (100) planes.1 The delayed solubility of microcrystalline MgO is attributed to surface hydroxide induced self-inhibition effects occurring at the (100) and (110) microplanes. The present work underlines the importance of morphology evolution and surface faceting of engineered nanomaterials particles during their dissolution. PMID:25668706

  2. Premarital Cohabitation and Marital Dissolution: An Examination of Recent Marriages

    ERIC Educational Resources Information Center

    Manning, Wendy D.; Cohen, Jessica A.

    2012-01-01

    An ongoing question remains for family researchers: Why does a positive association between cohabitation and marital dissolution exist when one of the primary reasons to cohabit is to test relationship compatibility? Drawing on recently collected data from the 2006-2008 National Survey of Family Growth, the authors examined whether premarital…

  3. Surface sediment characteristics and tower karst dissolution, Guilin, southern China

    NASA Astrophysics Data System (ADS)

    Tang, Tao

    2003-01-01

    Dissolution of extensive outcrops of limestone and dolostone in humid tropical and subtropical southern China produced numerous caves and residual hills that are referred as tower karst. This study identifies and relates the physical and chemical characteristics of the surface sediment with the limestone bedrock in Guilin to assess the influence of the limestone dissolution process on sediment composition. The results of this study indicated that (i) both limestone and dolostone of the region are very pure (99.5% and 98.5% of CaCO 3 and MgCO 3, respectively); (ii) the material composition of limestone and dolostone is different from that of soil and sediment of the region: constituents of surface sediments are highly related with the clastic sedimentary rocks, such as the mudstone, but show negative correlation with limestone and dolostone; (iii) the limestone formations are highly resistant to physical weathering and disintegration; their durability versus physical weathering and their high susceptibility to chemical dissolution account for why residual towers can form and persist; (iv) a dual-zone environmental structure exists vertically downward from the surface in Guilin: the zone of unconsolidated clastic sediments that is predominantly acidic, and the zone of karstified limestone that is predominantly basic. The evidence suggests that the environment and processes differ in these two zones. The chemical dissolution of limestone that formed tower karst of the region is not mainly responsible for the accumulation of clastic sediment on the surface.

  4. Dissolution kinetics of a sintered molybdenum coating applied on ceramics

    SciTech Connect

    Kuz`ko, V.S.

    1994-11-01

    Using weighing and corrosion diagrams, the etching parameters are determined for a sintered M-21 molybdenum coating applied to VK 94-1 vacuum-tight ceramics. Dissolution of M-21 in an alkaline solution of potassium hexacyanoferrate(III) can be treated as a corrosion process proceeding with kinetic control.

  5. Impact of fillers on dissolution kinetic of fenofibrate dry foams.

    PubMed

    Lenz, Elisabeth; Sprunk, Angela; Kleinebudde, Peter; Page, Susanne

    2015-01-01

    Dry foam technology reveals the opportunity to improve the dissolution behavior of poorly soluble drugs tending to agglomeration due to micronization. In this study, the impact of fillers on the manufacturability, the properties of dry foams and granules as well as the dissolution kinetics of dry foam tablets was investigated using fenofibrate as a model compound. Different maltodextrins and dried glucose syrups, a maltodextrin-phosphatidylcholine complex, isomalt and a 1:1 mixture of mannitol/glucose syrup were used as filler. Within the group of maltodextrins and glucose syrups, the influences of dextrose equivalent (DE), particle morphology and botanical source of starch were investigated. Comparable macroscopic foam structures were obtained with maltodextrins and glucose syrups whereas different foam morphologies were obtained for the other fillers tested. Regarding the maltodextrins and glucose syrups, different physicochemical and particle properties had a minor impact on granule characteristics and tablet dissolution. Using the maltodextrin-phosphatidylcholine complex resulted in a low specific surface area of the granules and a slow tablet dissolution caused by a slow disintegration. In contrast, a high specific surface area and a fast release were obtained with isomalt and glucose syrup/mannitol mixture indicating that high soluble low molecular weight fillers enable the development of fast dissolving dry foam tablets. PMID:24901031

  6. Percolation model for selective dissolution of multi-component glasses

    SciTech Connect

    Kale, R.P.; Brinker, C.J.

    1995-03-01

    A percolation model is developed which accounts for most known features of the process of porous glass membrane preparation by selective dissolution of multi-component glasses. The model is founded within tile framework of the classical percolation theory, wherein the components of a glass are represented by random sites on a suitable lattice. Computer simulation is used to mirror the generation of a porous structure during the dissolution process, reproducing many of the features associated with the phenomenon. Simulation results evaluate the effect of the initial composition of the glass on the kinetics of the leaching process as well as the morphology of the generated porous structure. The percolation model establishes the porous structure as a percolating cluster of unreachable constituents in the glass. The simulation algorithm incorporates removal of both, the accessible leachable components in the glass as well as the independent clusters of unreachable components not attached to the percolating cluster. The dissolution process thus becomes limited by the conventional site percolation thresholds of the unreachable components (which restricts the formation of the porous network), as well as the leachable components (which restricts the accessibility of the solvating medium into the glass). The simulation results delineate the range of compositional variations for successful porous glass preparation and predict the variation of porosity, surface area, dissolution rates and effluent composition with initial composition and time. Results compared well with experimental studies and improved upon similar models attempted in die past.

  7. Adolescents' Explanations for Romantic Dissolutions: A Developmental Perspective

    ERIC Educational Resources Information Center

    Connolly, Jennifer; McIsaac, Caroline

    2009-01-01

    Our objective was to examine the prevalence and developmental significance of romantic break-ups in adolescence, a relatively unexplored area of study. We examined their occurrence in a sample of 910 adolescents, first noting the frequency of these events across age, gender, and romantic experience, and then analyzing the dissolution explanations…

  8. Mg(+)-ligand binding energies

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Partridge, Harry

    1991-01-01

    Ab initio calculations are used to optimize the structures and determine the binding energies of Mg(+) to a series of ligands. Mg(+) bonds electrostatically with benzene, acetone, H2, CO, and NH3 and a self-consistent-field treatment gives a good description of the bonding. The bonding in MgCN(+) and MgCH3(+) is largely covalent and a correlated treatment is required.

  9. Unusual ligand coordination for cesium

    SciTech Connect

    Bryan, J.C.; Kavallieratos, K.; Sachleben, R.A.

    2000-04-03

    When complexed by tetrabenzo-24-crown-8, the cesium ion can accommodate unprecedented ligation. The structures of the complexes are presented. These structures are the first reported examples of linear {eta}{sup 2}-acetonitrile coordination to any metal ion and the first structures illustrating {eta}{sup 2}-acetonitrile and dichloromethane ligation to an alkali metal ion. Possible steric and electronic origins of these unusual metal-ligand interactions are discussed.

  10. Presentation of Ligands on Hydroxylapatite

    NASA Technical Reports Server (NTRS)

    Chu, Barbara C. F.; Orgel, Leslie E.

    1997-01-01

    Conjugates of biotin with the decamer of glutamic acid (glu(sub 10)) and the trimer of D,L-2-amino-5-phosphonovaleric acid (I) have been synthesized, and it has been shown that they mediate the binding of avidin to hydroxylapatite. In a similar way a conjugate of methotrexate with glu(sub 10) mediates the binding of dihydrofolate reductase to the mineral. The presentation of ligands on the hydroxylapatite component of bone may find applications in clinical medicine.

  11. A Model for Dissolution of Lime in Steelmaking Slags

    NASA Astrophysics Data System (ADS)

    Sarkar, Rahul; Roy, Ushasi; Ghosh, Dinabandhu

    2016-04-01

    In a previous study by Sarkar et al. (Metall. Mater. Trans. B 46B:961 2015), a dynamic model of the LD steelmaking was developed. The prediction of the previous model (Sarkar et al. in Metall. Mater. Trans. B 46B:961 2015) for the bath (metal) composition matched well with the plant data (Cicutti et al. in Proceedings of 6th International Conference on Molten Slags, Fluxes and Salts, Stockholm City, 2000). However, with respect to the slag composition, the prediction was not satisfactory. The current study aims to improve upon the previous model Sarkar et al. (Metall. Mater. Trans. B 46B:961 2015) by incorporating a lime dissolution submodel into the earlier one. From the industrial point of view, the understanding of the lime dissolution kinetics is important to meet the ever-increasing demand of producing low-P steel at a low basicity. In the current study, three-step kinetics for the lime dissolution is hypothesized on the assumption that a solid layer of 2CaO·SiO2 should form around the unreacted core of the lime. From the available experimental data, it seems improbable that the observed kinetics should be controlled singly by any one kinetic step. Accordingly, a general, mixed control model has been proposed to calculate the dissolution rate of the lime under varying slag compositions and temperatures. First, the rate equation for each of the three rate-controlling steps has been derived, for three different lime geometries. Next, the rate equation for the mixed control kinetics has been derived and solved to find the dissolution rate. The model predictions have been validated by means of the experimental data available in the literature. In addition, the effects of the process conditions on the dissolution rate have been studied, and compared with the experimental results wherever possible. Incorporation of this submodel into the earlier global model (Sarkar et al. in Metall. Mater. Trans. B 46B:961 2015) enables the prediction of the lime dissolution rate

  12. Quartz dissolution: Negative crystal experiments and a rate law

    NASA Astrophysics Data System (ADS)

    Gratz, Andrew J.; Bird, Peter

    1993-03-01

    The negative crystal method is used to extend the range of measured quartz dissolution rates as a function of temperature and pOH, extent of saturation, and ionic strength. The activation energy is constant for pOH = 1 to 4, and rate decreases linearly with saturation, indicating a precipitation reaction that is first order in silicic acid. Dissolution is slowed by Ca and Mg ions; the effect of Ca is strongest on the unit rhombohedra. A simple rate law based on surface charging is proposed and shown to fit the data. Only a reaction in which the activated complex is negatively charged is consistent with rate measurements. Some constraints on fundamental kinetic parameters are inferred. Data for all materials (single crystals and powders) can be fit by the single rate law < Rdiss> = G· A0· T· S·exp(- Ediss/ RT), S = I0.3 · {0.095 · aoH- -0.5+ 1} -1, G = 1 for rough faces while G = Y · exp(- ΔEinter/ RT) for smooth faces, A0 = 6.64 · 10 -3ms s-1K-1, where = limiting dissolution rate in m/s, S is the surface charge, aOH- is the molal hydroxide activity relative to an infinitely dilute solution at STP, I is the ionic strength, T is the temperature, ΔEinter is the energy of interaction ( 6 kJ/mol) causing step formation on the crystal surface, Ediss is the activation energy of dissolution of 78.6 kJ/mol, and Y is a face constant equal to 1 for the prism and 1.63 or 1.87 for the positive and negative unit rhombs, respectively. The available data in the literature suggests G = 1 to 9.5 for various other crystal directions, G = 2-4 for powders with optically estimated areas, while G = 0.1-0.3 describes powders with BET-determined areas. This equation applies over a wide range of conditions: 25-300°C, ionic strength 0.003-0.1 m, and any pOH below the point of zero charge of quartz; a similar equation applies to growth. Dissolution mechanisms for defective crystals are discussed and may result in dissolution rate enhancements of 2X. The observation that

  13. A Model for Dissolution of Lime in Steelmaking Slags

    NASA Astrophysics Data System (ADS)

    Sarkar, Rahul; Roy, Ushasi; Ghosh, Dinabandhu

    2016-08-01

    In a previous study by Sarkar et al. (Metall. Mater. Trans. B 46B:961 2015), a dynamic model of the LD steelmaking was developed. The prediction of the previous model (Sarkar et al. in Metall. Mater. Trans. B 46B:961 2015) for the bath (metal) composition matched well with the plant data (Cicutti et al. in Proceedings of 6th International Conference on Molten Slags, Fluxes and Salts, Stockholm City, 2000). However, with respect to the slag composition, the prediction was not satisfactory. The current study aims to improve upon the previous model Sarkar et al. (Metall. Mater. Trans. B 46B:961 2015) by incorporating a lime dissolution submodel into the earlier one. From the industrial point of view, the understanding of the lime dissolution kinetics is important to meet the ever-increasing demand of producing low-P steel at a low basicity. In the current study, three-step kinetics for the lime dissolution is hypothesized on the assumption that a solid layer of 2CaO·SiO2 should form around the unreacted core of the lime. From the available experimental data, it seems improbable that the observed kinetics should be controlled singly by any one kinetic step. Accordingly, a general, mixed control model has been proposed to calculate the dissolution rate of the lime under varying slag compositions and temperatures. First, the rate equation for each of the three rate-controlling steps has been derived, for three different lime geometries. Next, the rate equation for the mixed control kinetics has been derived and solved to find the dissolution rate. The model predictions have been validated by means of the experimental data available in the literature. In addition, the effects of the process conditions on the dissolution rate have been studied, and compared with the experimental results wherever possible. Incorporation of this submodel into the earlier global model (Sarkar et al. in Metall. Mater. Trans. B 46B:961 2015) enables the prediction of the lime dissolution rate

  14. Absolute Ligand Discrimination by Dimeric Signaling Receptors.

    PubMed

    Fathi, Sepehr; Nayak, Chitra R; Feld, Jordan J; Zilman, Anton G

    2016-09-01

    Many signaling pathways act through shared components, where different ligand molecules bind the same receptors or activate overlapping sets of response regulators downstream. Nevertheless, different ligands acting through cross-wired pathways often lead to different outcomes in terms of the target cell behavior and function. Although a number of mechanisms have been proposed, it still largely remains unclear how cells can reliably discriminate different molecular ligands under such circumstances. Here we show that signaling via ligand-induced receptor dimerization-a very common motif in cellular signaling-naturally incorporates a mechanism for the discrimination of ligands acting through the same receptor. PMID:27602720

  15. A Novel Approach to Experimental Studies of Mineral Dissolution Kinetics

    SciTech Connect

    Chen Zhu

    2006-08-31

    Currently, DOE is conducting pilot CO{sub 2} injection tests to evaluate the concept of geological sequestration. One strategy that potentially enhances CO{sub 2} solubility and reduces the risk of CO{sub 2} leak back to the surface is dissolution of indigenous minerals in the geological formation and precipitation of secondary carbonate phases, which increases the brine pH and immobilizes CO{sub 2}. Clearly, the rates at which these dissolution and precipitation reactions occur directly determine the efficiency of this strategy. However, one of the fundamental problems in modern geochemistry is the persistent two to five orders of magnitude discrepancy between laboratory measured and field derived feldspar dissolution rates. To date, there is no real guidance as to how to predict silicate reaction rates for use in quantitative models. Current models for assessment of geological carbon sequestration have generally opted to use laboratory rates, in spite of the dearth of such data for compositionally complex systems, and the persistent disconnect between laboratory and field applications. Therefore, a firm scientific basis for predicting silicate reaction kinetics in CO2 injected geological formations is urgently needed to assure the reliability of the geochemical models used for the assessments of carbon sequestration strategies. The funded experimental and theoretical study attempts to resolve this outstanding scientific issue by novel experimental design and theoretical interpretation to measure silicate dissolution rates and iron carbonate precipitation rates at conditions pertinent to geological carbon sequestration. In the second year of the project, we completed CO{sub 2}-Navajo sandstone interaction batch and flow-through experiments and a Navajo sandstone dissolution experiment without the presence of CO{sub 2} at 200 C and 250-300 bars, and initiated dawsonite dissolution and solubility experiments. We also performed additional 5-day experiments at the

  16. Tumor Targeting via Integrin Ligands

    PubMed Central

    Marelli, Udaya Kiran; Rechenmacher, Florian; Sobahi, Tariq Rashad Ali; Mas-Moruno, Carlos; Kessler, Horst

    2013-01-01

    Selective and targeted delivery of drugs to tumors is a major challenge for an effective cancer therapy and also to overcome the side-effects associated with current treatments. Overexpression of various receptors on tumor cells is a characteristic structural and biochemical aspect of tumors and distinguishes them from physiologically normal cells. This abnormal feature is therefore suitable for selectively directing anticancer molecules to tumors by using ligands that can preferentially recognize such receptors. Several subtypes of integrin receptors that are crucial for cell adhesion, cell signaling, cell viability, and motility have been shown to have an upregulated expression on cancer cells. Thus, ligands that recognize specific integrin subtypes represent excellent candidates to be conjugated to drugs or drug carrier systems and be targeted to tumors. In this regard, integrins recognizing the RGD cell adhesive sequence have been extensively targeted for tumor-specific drug delivery. Here we review key recent examples on the presentation of RGD-based integrin ligands by means of distinct drug-delivery systems, and discuss the prospects of such therapies to specifically target tumor cells. PMID:24010121

  17. Effects of Bacillus subtilis endospore surface reactivity on the rate of forsterite dissolution

    NASA Astrophysics Data System (ADS)

    Harrold, Z.; Gorman-Lewis, D.

    2013-12-01

    Primary mineral dissolution products, such as silica (Si), calcium (Ca) and magnesium (Mg), play an important role in numerous biologic and geochemical cycles including microbial metabolism, plant growth and secondary mineral precipitation. The flux of these and other dissolution products into the environment is largely controlled by the rate of primary silicate mineral dissolution. Bacteria, a ubiquitous component in water-rock systems, are known to facilitate mineral dissolution and may play a substantial role in determining the overall flux of dissolution products into the environment. Bacterial cell walls are complex and highly reactive organic surfaces that can affect mineral dissolution rates directly through microbe-mineral adsorption or indirectly by complexing dissolution products. The effect of bacterial surface adsorption on chemical weathering rates may even outweigh the influence of active processes in environments where a high proportion of cells are metabolically dormant or cell metabolism is slow. Complications associated with eliminating or accounting for ongoing metabolic processes in long-term dissolution studies have made it challenging to isolate the influence of cell wall interactions on mineral dissolution rates. We utilized Bacillus subtilis endospores, a robust and metabolically dormant cell type, to isolate and quantify the effects of bacterial surface reactivity on forsterite (Mg2SiO4) dissolution rates. We measured the influence of both direct and indirect microbe-mineral interactions on forsterite dissolution. Indirect pathways were isolated using dialysis tubing to prevent mineral-microbe contact while allowing free exchange of dissolved mineral products and endospore-ion adsorption. Homogenous experimental assays allowed both direct microbe-mineral and indirect microbe-ion interactions to affect forsterite dissolution rates. Dissolution rates were calculated based on silica concentrations and zero-order dissolution kinetics

  18. Dissolution studies of hydroxyapatite and glass-reinforced hydroxyapatite ceramics

    SciTech Connect

    Queiroz, A.C.; Santos, J.D.; Monteiro, F.J.; Prado da Silva, M.H

    2003-03-15

    In the continuous agitation assays, glass-reinforced hydroxyapatite (GR-HA) was shown to form a calcium phosphate (CaP) layer, but hydroxyapatite (HA) only formed dispersed precipitates. The formation of this layer was first detected on the GR-HA with a 7.5% glass addition (7.5 GR-HA) after only 3 days of immersion in simulated body fluid (SBF). The time required for layer formation decreased as the amount of glass added to the HA increased. The dissolution rate of the materials followed a similar pattern, i.e. the dissolution rate for GR-HA was higher than for HA, and increased with the addition of glass. The immersion of 7.5 GR-HA in water showed almost linear dissolution kinetics over the immersion periods (3, 7, 15, 30 and 60 days). The concentration of calcium ions in solution and the scanning electron microscopy (SEM) analysis of the 7.5 GR-HA specimens immersed in water and in SBF revealed a clear competition between the material dissolution and the precipitation of a CaP phase. Fourier transformed infrared spectroscopy with alternated total reflectance (FTIR-ATR) analysis indicated that the CaP phase that formed during longer immersion times (30 and 60 days) could be a carbonate-substituted CaP precipitate. As expected from previous work, the GR-HA behavior in terms of its in vitro bioactivity is higher than HA because a homogeneous CaP layer is formed and the precipitation occurs faster. From the dissolution test and in accordance with the chemical composition of the samples, GR-HA was more soluble than HA.

  19. Test Objectives for the Saltcake Dissolution Retrieval Demonstration

    SciTech Connect

    DEFIGH PRICE, C.

    2000-09-22

    This document describes the objectives the Saltcake Dissolution Retrieval Demonstration. The near term strategy for single-shell tank waste retrieval activities has shifted from focusing on maximizing the number of tanks entered for retrieval (regardless of waste volume or content) to a focus on scheduling the retrieval of wastes from those single-shell tanks with a high volume of contaminants of concern. These contaminants are defined as mobile, long-lived radionuclides that have a potential of reaching the groundwater and the Columbia River. This strategy also focuses on the performance of key retrieval technology demonstrations, including the Saltcake Dissolution Retrieval Demonstration, in a variety of waste forms and tank farm locations to establish a technical basis for future work. The work scope will also focus on the performance of risk assessment, retrieval performance evaluations (RPE) and incorporating vadose zone characterization data on a tank-by-tank basis, and on updating tank farm closure/post closure work plans. The deployment of a retrieval technology other than Past-Practice Sluicing (PPS) allows determination of limits of technical capabilities, as well as, providing a solid planning basis for future SST retrievals. This saltcake dissolution technology deployment test will determine if saltcake dissolution is a viable retrieval option for SST retrieval. CH2M Hill Hanford Group (CHG) recognizes the SST retrieval mission is key to the success of the River Protection Project (RPP) and the overall completion of the Hanford Site cleanup. The objectives outlined in this document will be incorporated into and used to develop the test and evaluation plan for saltcake dissolution retrievals. The test and evaluation plan will be developed in fiscal year 2001.

  20. Ligand identification using electron-density mapcorrelations

    SciTech Connect

    Terwilliger, Thomas C.; Adams, Paul D.; Moriarty, Nigel W.; Cohn,Judith D.

    2006-12-01

    A procedure for the identification of ligands bound incrystal structuresof macromolecules is described. Two characteristics ofthe density corresponding to a ligand are used in the identificationprocedure. One is the correlation of the ligand density with each of aset of test ligands after optimization of the fit of that ligand to thedensity. The other is the correlation of a fingerprint of the densitywith the fingerprint of model density for each possible ligand. Thefingerprints consist of an ordered list of correlations of each the testligands with the density. The two characteristics are scored using aZ-score approach in which the correlations are normalized to the mean andstandard deviation of correlations found for a variety of mismatchedligand-density pairs, so that the Z scores are related to the probabilityof observing a particular value of the correlation by chance. Theprocedure was tested with a set of 200 of the most commonly found ligandsin the Protein Data Bank, collectively representing 57 percent of allligands in the Protein Data Bank. Using a combination of these twocharacteristics of ligand density, ranked lists of ligand identificationswere made for representative (F-o-F-c) exp(i phi(c)) difference densityfrom entries in the Protein Data Bank. In 48 percent of the 200 cases,the correct ligand was at the top of the ranked list of ligands. Thisapproach may be useful in identification of unknown ligands in newmacromolecular structures as well as in the identification of whichligands in a mixture have bound to a macromolecule.

  1. Dissolution rates of coals and graphite in Fe-C-S melts in direct ironmaking: Influence of melt carbon and sulfur on carbon dissolution

    NASA Astrophysics Data System (ADS)

    Wu, C.; Sahajwalla, V.

    2000-04-01

    Carbon dissolution from graphite and coals was investigated by using a carburizer cover technique in an induction furnace. The intent of the study was to investigate the influence of factors governing the rate of carbon dissolution from carbonaceous materials, especially coals, into Fe-C-S melts. The factors studied were the initial melt carbon and sulfur concentrations and the wettability between carbonaceous materials and the melt. It was found that graphite dissolves markedly faster than coal. The rate of carbon dissolution from graphite could be decreased by increasing the sulfur in the melt. Also, poor wetting could retard the rate of carbon dissolution by reducing the surface area for mass transfer. Carbon dissolution from graphite is controlled by mass transfer in the liquid boundary layer adjacent to the solid/liquid interface. The rate of carbon dissolution from coal is more sensitive to the molten iron composition. A higher initial melt carbon and sulfur content retards the rate of carbon dissolution from coal more significantly than from graphite. However, the rate constant of coal char dissolution does not show a strong dependence on the wettability. Carbon dissolution from coals is most likely governed by a mixed-control mechanism that includes liquid-side mass transfer. The mechanisms underlying the influence of bath sulfur on carbon dissolution from graphite and coals are discussed.

  2. Nanosuspensions Containing Oridonin/HP-β-Cyclodextrin Inclusion Complexes for Oral Bioavailability Enhancement via Improved Dissolution and Permeability.

    PubMed

    Zhang, Xingwang; Zhang, Tianpeng; Lan, Yali; Wu, Baojian; Shi, Zhihai

    2016-04-01

    Chemotherapy via oral route of anticancer drugs offers much convenience and compliance to patients. However, oral chemotherapy has been challenged by limited absorption due to poor drug solubility and intestinal efflux. In this study, we aimed to develop a nanosuspension formulation of oridonin (Odn) using its cyclodextrin inclusion complexes to enhance oral bioavailability. Nanosuspensions containing Odn/2 hydroxypropyl-β-cyclodextrin inclusion complexes (Odn-CICs) were prepared by a solvent evaporation followed by wet media milling technique. The nanosuspensions were characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and dissolution. The resulting nanosuspensions were approximately 313.8 nm in particle size and presented a microcrystal morphology. Nanosuspensions loading Odn-CICs dramatically enhanced the dissolution of Odn. Further, the intestinal effective permeability of Odn was markedly enhanced in the presence of 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) and poloxamer. Bioavailability studies showed that nanosuspensions with Odn-CICs can significantly promote the oral absorption of Odn with a relative bioavailability of 213.99% (Odn suspensions as reference). Odn itself possesses a moderate permeability and marginal intestinal metabolism. Thus, the enhanced bioavailability for Odn-CIC nanosuspensions can be attributed to improved dissolution and permeability by interaction with absorptive epithelia and anti-drug efflux. Nanosuspensions prepared from inclusion complexes may be a promising approach for the oral delivery of anticancer agents. PMID:26187778

  3. Repassivation behavior of 316L stainless steel in borate buffer solution: Kinetics analysis of anodic dissolution and film formation

    NASA Astrophysics Data System (ADS)

    Xu, Haisong; Sun, Dongbai; Yu, Hongying

    2015-12-01

    The repassivation behavior of metals or alloys after oxide film damage determines the development of local corrosion and corrosion resistance. In this work, the repassivation kinetics of 316L stainless steel (316L SS) are investigated in borate buffer solution (pH 9.1) by using the abrading electrode technique. The current densities flowing from bare 316L SS surface are measured by potentiostatic method and analyzed to characterize repassivation kinetics. The initial stages of current decay (t < 500 ms) are discussed according to a film growth model, which describes the initial current transient should be divided into substrate dissolution current and passive film formation current based on Avrami kinetics. Then the two independent components are analyzed individually. The film formation rate and the thickness of film are compared in different applied potential. It is shown that anodic dissolution dominates the repassivation for a short time during the early times, and a higher applied potential will promote the anodic dissolution of metal. The film growth rate increases slightly with increasing in potential. Correspondingly, increase in applied potential from 0 VSCE to 0.8 VSCE results in thicker monolayer, which covers the whole bare surface at the time of θ = 1. The electric field strengths through the thin passive film could reach 3.97 × 106 V cm-1.

  4. Revealing a steroid receptor ligand as a unique PPAR[gamma] agonist

    SciTech Connect

    Lin, Shengchen; Han, Ying; Shi, Yuzhe; Rong, Hui; Zheng, Songyang; Jin, Shikan; Lin, Shu-Yong; Lin, Sheng-Cai; Li, Yong

    2012-06-28

    Peroxisome proliferator-activated receptor gamma (PPAR{gamma}) regulates metabolic homeostasis and is a molecular target for anti-diabetic drugs. We report here the identification of a steroid receptor ligand, RU-486, as an unexpected PPAR{gamma} agonist, thereby uncovering a novel signaling route for this steroid drug. Similar to rosiglitazone, RU-486 modulates the expression of key PPAR{gamma} target genes and promotes adipocyte differentiation, but with a lower adipogenic activity. Structural and functional studies of receptor-ligand interactions reveal the molecular basis for a unique binding mode for RU-486 in the PPAR{gamma} ligand-binding pocket with distinctive properties and epitopes, providing the molecular mechanisms for the discrimination of RU-486 from thiazolidinediones (TZDs) drugs. Our findings together indicate that steroid compounds may represent an alternative approach for designing non-TZD PPAR{gamma} ligands in the treatment of insulin resistance.

  5. Colloidal metal oxide nanocrystal catalysis by sustained chemically driven ligand displacement

    NASA Astrophysics Data System (ADS)

    de Roo, Jonathan; van Driessche, Isabel; Martins, José C.; Hens, Zeger

    2016-05-01

    Surface chemistry is a key enabler for colloidal nanocrystal applications. In this respect, metal oxide nanocrystals (NCs) stand out from other NCs as carboxylic acid ligands adsorb on their surface by dissociation to carboxylates and protons, the latter proving essential in electron transfer reactions. Here, we show that this binding motif sets the stage for chemically driven ligand displacement where the binding of amines or alcohols to HfO2 NCs is promoted by the conversion of a bound carboxylic acid into a non-coordinating amide or ester. Furthermore, the sustained ligand displacement, following the addition of excess carboxylic acid, provides a catalytic pathway for ester formation, whereas the addition of esters leads to NC-catalysed transesterification. Because sustained, chemically driven ligand displacement leaves the NCs--including their surface composition--unchanged and preserves colloidal stability, metal oxide nanocrystals are thus turned into effective nanocatalysts that bypass the tradeoff between colloidal stability and catalytic activity.

  6. Programmable Multivalent Display of Receptor Ligands using Peptide Nucleic Acid Nanoscaffolds

    PubMed Central

    Englund, Ethan A.; Wang, Deyun; Fujigaki, Hidetsugu; Sakai, Hiroyasu; Micklitsch, Christopher M.; Ghirlando, Rodolfo; Martin-Manso, Gema; Pendrak, Michael L.; Roberts, David D.; Durell, Stewart R.; Appella, Daniel H.

    2012-01-01

    Multivalent effects dictate the binding affinity of multiple ligands on one molecular entity to receptors. Integrins are receptors that mediate cell attachment through multivalent binding to peptide sequences within the extracellular matrix, and overexpression promotes the metastasis of some cancers. Multivalent display of integrin antagonists enhances their efficacy, but current scaffolds have limited ranges and precision for the display of ligands. Here we present an approach to study multivalent effects across wide ranges of ligand number, density, and three-dimensional arrangement. Using L-lysine γ-substituted peptide nucleic acids, the multivalent effects of an integrin antagonist were examined over a range of 1 to 45 ligands. The optimal construct improves the inhibitory activity of the antagonist by two orders of magnitude against the binding of melanoma cells to the extracellular matrix in both in vitro and in vivo models. PMID:22233624

  7. Parameterization of phosphine ligands reveals mechanistic pathways and predicts reaction outcomes.

    PubMed

    Niemeyer, Zachary L; Milo, Anat; Hickey, David P; Sigman, Matthew S

    2016-06-01

    The mechanistic foundation behind the identity of a phosphine ligand that best promotes a desired reaction outcome is often non-intuitive, and thus has been addressed in numerous experimental and theoretical studies. In this work, multivariate correlations of reaction outcomes using 38 different phosphine ligands were combined with classic potentiometric analyses to study a Suzuki reaction, for which the site selectivity of oxidative addition is highly dependent on the nature of the phosphine. These studies shed light on the generality of hypotheses regarding the structural influence of different classes of phosphine ligands on the reaction mechanism(s), and deliver a methodology that should prove useful in future studies of phosphine ligands. PMID:27219707

  8. Colloidal metal oxide nanocrystal catalysis by sustained chemically driven ligand displacement.

    PubMed

    De Roo, Jonathan; Van Driessche, Isabel; Martins, José C; Hens, Zeger

    2016-05-01

    Surface chemistry is a key enabler for colloidal nanocrystal applications. In this respect, metal oxide nanocrystals (NCs) stand out from other NCs as carboxylic acid ligands adsorb on their surface by dissociation to carboxylates and protons, the latter proving essential in electron transfer reactions. Here, we show that this binding motif sets the stage for chemically driven ligand displacement where the binding of amines or alcohols to HfO2 NCs is promoted by the conversion of a bound carboxylic acid into a non-coordinating amide or ester. Furthermore, the sustained ligand displacement, following the addition of excess carboxylic acid, provides a catalytic pathway for ester formation, whereas the addition of esters leads to NC-catalysed transesterification. Because sustained, chemically driven ligand displacement leaves the NCs-including their surface composition-unchanged and preserves colloidal stability, metal oxide nanocrystals are thus turned into effective nanocatalysts that bypass the tradeoff between colloidal stability and catalytic activity. PMID:26808460

  9. Multi-ligand functionalized particle design for cell targeting and drug delivery.

    PubMed

    Yoon, Jung Hyun; Kim, Dae Kyung; Na, Miso; Lee, Sei Young

    2016-06-01

    Particle-based delivery systems encompass some of the most promising techniques for therapeutic drug delivery. In particular, multi-functional nanovector systems permit diverse functions such as efficient drug/imaging agent loading and unloading and increased target specificity. To enhance the efficiency of delivery systems, particle size and shape can be altered and specific ligands can be conjugated to the particles to promote interactions with receptors expressed on target cells. Moreover, to maximize efficiency and specificity, multiple types of ligands can be conjugated to the particle surface. To analyze the multi-ligand-receptor mediated adhesion process, we developed a stochastic model considering diverse biophysical parameters, including non-specific interactions, ligand-receptor specific interactions, kinetic affinity between ligand and receptor, hydrodynamic force and particle size. The results demonstrate that limited contact area restricts the probability of adhesion such that multiple ligand-receptor pairs do not always show enhanced adhesion characteristics. To optimize the effect of multiple ligand-receptor pairs, biophysical parameters must be considered. PMID:27100957

  10. Automatic generation of bioinformatics tools for predicting protein–ligand binding sites

    PubMed Central

    Banno, Masaki; Ueki, Kokoro; Saad, Gul; Shimizu, Kentaro

    2016-01-01

    Motivation: Predictive tools that model protein–ligand binding on demand are needed to promote ligand research in an innovative drug-design environment. However, it takes considerable time and effort to develop predictive tools that can be applied to individual ligands. An automated production pipeline that can rapidly and efficiently develop user-friendly protein–ligand binding predictive tools would be useful. Results: We developed a system for automatically generating protein–ligand binding predictions. Implementation of this system in a pipeline of Semantic Web technique-based web tools will allow users to specify a ligand and receive the tool within 0.5–1 day. We demonstrated high prediction accuracy for three machine learning algorithms and eight ligands. Availability and implementation: The source code and web application are freely available for download at http://utprot.net. They are implemented in Python and supported on Linux. Contact: shimizu@bi.a.u-tokyo.ac.jp Supplementary information: Supplementary data are available at Bioinformatics online. PMID:26545824

  11. Carbonate mineral dissolution kinetics in high pressure experiments

    NASA Astrophysics Data System (ADS)

    Dethlefsen, F.; Dörr, C.; Schäfer, D.; Ebert, M.

    2012-04-01

    The potential CO2 reservoirs in the North German Basin are overlain by a series of Mesozoic barrier rocks and aquifers and finally mostly by Tertiary and Quaternary close-to-surface aquifers. The unexpected rise of stored CO2 from its reservoir into close-to-surface aquifer systems, perhaps through a broken well casing, may pose a threat to groundwater quality because of the acidifying effect of CO2 dissolution in water. The consequences may be further worsening of the groundwater quality due to the mobilization of heavy metals. Buffer mechanisms counteracting the acidification are for instance the dissolution of carbonates. Carbonate dissolution kinetics is comparably fast and carbonates can be abundant in close-to-surface aquifers. The disadvantages of batch experiments compared to column experiments in order to determine rate constants are well known and have for instance been described by v. GRINSVEN and RIEMSDIJK (1992). Therefore, we have designed, developed, tested, and used a high-pressure laboratory column system to simulate aquifer conditions in a flow through setup within the CO2-MoPa project. The calcite dissolution kinetics was determined for CO2-pressures of 6, 10, and 50 bars. The results were evaluated by using the PHREEQC code with a 1-D reactive transport model, applying a LASAGA (1984) -type kinetic dissolution equation (PALANDRI and KHARAKA, 2004; eq. 7). While PALANDRI and KHARAKA (2004) gave calcite dissolution rate constants originating from batch experiments of log kacid = -0.3 and log kneutral = -5.81, the data of the column experiment were best fitted using log kacid = -2.3 and log kneutral = -7.81, so that the rate constants fitted using the lab experiment applying 50 bars pCO2 were approximately 100 times lower than according to the literature data. Rate constants of experiments performed at less CO2 pressure (pCO2 = 6 bars: log kacid = -1.78; log kneutral = -7.29) were only 30 times lower than literature data. These discrepancies in the

  12. EVALUATION OF LOW TEMPERATURE ALUMINUM DISSOLUTION IN TANK 51

    SciTech Connect

    Pike, J

    2008-09-04

    Liquid Waste Organization (LWO) identified aluminum dissolution as a method to mitigate the effect of having about 50% more solids in High Level Waste (HLW) sludge than previously planned. Previous aluminum dissolution performed in a HLW tank in 1982 was performed at approximately 85 C for 5 days, which became the baseline aluminum dissolution process. LWO initiated a project to modify a waste tank to meet these requirements. Subsequent to an alternative evaluation, LWO management identified an opportunity to perform aluminum dissolution on sludge destined for Sludge Batch 5, but within a limited window that would not allow time for any modifications for tank heating. A variation of the baseline process, dubbed Low Temperature Aluminum Dissolution (LTAD), was developed based on the constraint of available energy input in Tank 51 and the window of opportunity, but was not constrained to a minimum extent of dissolution, i.e. dissolve as much aluminum as possible within the time available. This process was intended to operate between 55 and 70 C, but for a significantly longer time than the baseline process. LTAD proceeded in parallel with the baseline project. The preliminary evaluation at the completion of LTAD focused on the material balance and extent of the aluminum dissolved. The range of values of extent of dissolution, 56% to 64%, resulted from the variation in liquid phase sample data available at the time. Additional solid phase data is available from a sample taken after LTAD to refine this range. This report provides additional detailed evaluation of the LTAD process based on analytical and field data and includes: a summary of the process chronology; a determination of an acceptable blending strategy for the aluminum-laden supernate stored in Tank 11; an update to the determination of aluminum dissolved using more complete sample results; a determination of the effect of LTAD on uranium, plutonium, and other metals; a determination of the rate of heat

  13. Dissolution on Titan and on Earth: Towards the age of Titan's karstic landscapes

    NASA Astrophysics Data System (ADS)

    Cornet, T.; Cordier, D.; Le Bahers, T.; Bourgeois, O.; Fleurant, C.; Le Mouélic, S.; Altobelli, N.

    2015-10-01

    The morphology of Titan's lacustrine depressions led to comparisons with terrestrial depressions developed by karstic dissolution. We tested this hypothesis by computing dissolution rates of Titan's solids in liquid methane. We inferred from these rates the timescales needed to create dissolution landforms of a given depth. Dissolution would be a very efficient geological process to shape Titan's surface, on timescales generally shorter than 100 Myrs, consistent with the youth of Titan's surface (<1 Gyr).

  14. Promoting Models

    NASA Astrophysics Data System (ADS)

    Li, Qin; Zhao, Yongxin; Wu, Xiaofeng; Liu, Si

    There can be multitudinous models specifying aspects of the same system. Each model has a bias towards one aspect. These models often override in specific aspects though they have different expressions. A specification written in one model can be refined by introducing additional information from other models. The paper proposes a concept of promoting models which is a methodology to obtain refinements with support from cooperating models. It refines a primary model by integrating the information from a secondary model. The promotion principle is not merely an academic point, but also a reliable and robust engineering technique which can be used to develop software and hardware systems. It can also check the consistency between two specifications from different models. A case of modeling a simple online shopping system with the cooperation of the guarded design model and CSP model illustrates the practicability of the promotion principle.

  15. UV and sunlight driven photoligation of quantum dots: understanding the photochemical transformation of the ligands.

    PubMed

    Aldeek, Fadi; Hawkins, Dana; Palomo, Valle; Safi, Malak; Palui, Goutam; Dawson, Philip E; Alabugin, Igor; Mattoussi, Hedi

    2015-02-25

    We have recently reported that photoinduced ligation of ZnS-overcoated quantum dots (QDs) offers a promising strategy to promote the phase transfer of these materials to polar and aqueous media using multidentate lipoic acid (LA)-modified ligands. In this study we investigate the importance of the underlying parameters that control this process, in particular, whether or not photoexcited QDs play a direct role in the photoinduced ligation. We find that irradiation of the ligand alone prior to mixing with hydrophobic QDs is sufficient to promote ligand exchange. Furthermore, photoligation onto QDs can also be carried out simply by using sunlight. Combining the use of Ellman's test with matrix-assisted laser desorption/ionization and electrospray ionization mass spectrometry, we probe the nature of the photochemical transformation of the ligands. We find that irradiation (using either a UV photoreactor or sunlight) alters the nature of the disulfide groups in the lipoic acid, yielding a different product mixture than what is observed for chemically reduced ligands. Irradiation of the ligand in solution generates a mixture of monomeric and oligomeric compounds. Ligation onto the QDs selectively favors oligomers, presumably due to their higher coordination onto the metal-rich QD surfaces. We also show that photoligation using mixed ligands allows the preparation of reactive nanocrystals. The resulting QDs are coupled to proteins and peptides and tested for cellular staining. This optically controlled ligation of QDs combined with the availability of a variety of multidentate and multifunctional LA-modified ligands open new opportunities for developing fluorescent platforms with great promises for use in imaging and sensor design. PMID:25612193

  16. Canonical and non-canonical Notch ligands

    PubMed Central

    D’SOUZA, BRENDAN; MELOTY-KAPELLA, LAURENCE; WEINMASTER, GERRY

    2015-01-01

    Notch signaling induced by canonical Notch ligands is critical for normal embryonic development and tissue homeostasis through the regulation of a variety of cell fate decisions and cellular processes. Activation of Notch signaling is normally tightly controlled by direct interactions with ligand-expressing cells and dysregulated Notch signaling is associated with developmental abnormalities and cancer. While canonical Notch ligands are responsible for the majority of Notch signaling, a diverse group of structurally unrelated non-canonical ligands has also been identified that activate Notch and likely contribute to the pleiotropic effects of Notch signaling. Soluble forms of both canonical and non-canonical ligands have been isolated, some of which block Notch signaling and could serve as natural inhibitors of this pathway. Ligand activity can also be indirectly regulated by other signaling pathways at the level of ligand expression, serving to spatio-temporally compartmentalize Notch signaling activity and integrate Notch signaling into a molecular network that orchestrates developmental events. Here, we review the molecular mechanisms underlying the dual role of Notch ligands as activators and inhibitors of Notch signaling. Additionally, evidence that Notch ligands function independent of Notch are presented. We also discuss how ligand post-translational modification, endocytosis, proteolysis and spatio-temporal expression regulate their signaling activity. PMID:20816393

  17. Conformational readout of RNA by small ligands

    PubMed Central

    Kligun, Efrat; Mandel-Gutfreund, Yael

    2013-01-01

    RNA molecules have highly versatile structures that can fold into myriad conformations, providing many potential pockets for binding small molecules. The increasing number of available RNA structures, in complex with proteins, small ligands and in free form, enables the design of new therapeutically useful RNA-binding ligands. Here we studied RNA ligand complexes from 10 RNA groups extracted from the protein data bank (PDB), including adaptive and non-adaptive complexes. We analyzed the chemical, physical, structural and conformational properties of binding pockets around the ligand. Comparing the properties of ligand-binding pockets to the properties of computed pockets extracted from all available RNA structures and RNA-protein interfaces, revealed that ligand-binding pockets, mainly the adaptive pockets, are characterized by unique properties, specifically enriched in rare conformations of the nucleobase and the sugar pucker. Further, we demonstrate that nucleotides possessing the rare conformations are preferentially involved in direct interactions with the ligand. Overall, based on our comprehensive analysis of RNA-ligand complexes, we suggest that the unique conformations adopted by RNA nucleotides play an important role in RNA recognition by small ligands. We term the recognition of a binding site by a ligand via the unique RNA conformations “RNA conformational readout.” We propose that “conformational readout” is a general way by which RNA binding pockets are recognized and selected from an ensemble of different RNA states. PMID:23618839

  18. Ligand placement based on prior structures: the guided ligand-replacement method

    SciTech Connect

    Klei, Herbert E.; Moriarty, Nigel W. Echols, Nathaniel; Terwilliger, Thomas C.; Baldwin, Eric T.; Pokross, Matt; Posy, Shana; Adams, Paul D.

    2014-01-01

    A new module, Guided Ligand Replacement (GLR), has been developed in Phenix to increase the ease and success rate of ligand placement when prior protein-ligand complexes are available. The process of iterative structure-based drug design involves the X-ray crystal structure determination of upwards of 100 ligands with the same general scaffold (i.e. chemotype) complexed with very similar, if not identical, protein targets. In conjunction with insights from computational models and assays, this collection of crystal structures is analyzed to improve potency, to achieve better selectivity and to reduce liabilities such as absorption, distribution, metabolism, excretion and toxicology. Current methods for modeling ligands into electron-density maps typically do not utilize information on how similar ligands bound in related structures. Even if the electron density is of sufficient quality and resolution to allow de novo placement, the process can take considerable time as the size, complexity and torsional degrees of freedom of the ligands increase. A new module, Guided Ligand Replacement (GLR), was developed in Phenix to increase the ease and success rate of ligand placement when prior protein–ligand complexes are available. At the heart of GLR is an algorithm based on graph theory that associates atoms in the target ligand with analogous atoms in the reference ligand. Based on this correspondence, a set of coordinates is generated for the target ligand. GLR is especially useful in two situations: (i) modeling a series of large, flexible, complicated or macrocyclic ligands in successive structures and (ii) modeling ligands as part of a refinement pipeline that can automatically select a reference structure. Even in those cases for which no reference structure is available, if there are multiple copies of the bound ligand per asymmetric unit GLR offers an efficient way to complete the model after the first ligand has been placed. In all of these applications, GLR

  19. Experimental results of calcine dissolution studies performed during FY-94,95

    SciTech Connect

    Brewer, K.N.; Olson, A.L.; Roesener, W.S.; Tonso, J.L.

    1997-09-01

    Calcine dissolution studies were performed in FY-94,95 in order to extend the knowledge of dissolution and to obtain information necessary for scale-up design and operation. Experiments reported in this document were performed with non-radioactive and actual calcines to generate qualitative data regarding: (a) calcine dissolution rates, (b) undissolved solids settling characteristics, (c) undissolved solids heel formation, and (d) chemical treatments for undissolved solids heel dissolution. The goal of this work was to achieve complete calcine dissolution, or to determine conditions that would result in the maximum calcine dissolution. Small scale laboratory experiments (test-tube dissolutions) and a bench scale dissolver set-up were used in the effort. Results from this work show the bulk of the undissolved solids to settle at a rate of >9 inches per second when the baseline dissolution parameters are used. Baseline dissolution parameters were 100 grams of calcine being dissolved in 1 L of 5 M HNO{sub 3} at > 90 C while the solution is being vigorously and constantly mixed. This work also verified that dissolution is most complete when performed with aggressive mixing. Sequential dissolutions performed with non-radioactive and actual calcine indicate that little undissolved solids heel build-up is expected, and this small heel can be further dissolved by increasing the dissolution time or by adding fresh nitric acid.

  20. Nonaqueous Phase Liquid Dissolution in Porous Media: Multi-Scale Effects of Multi-Component Dissolution Kinetics on Cleanup Time

    SciTech Connect

    McNab, W; Ezzedine, S; Detwiler, R

    2007-02-26

    Industrial organic solvents such as trichloroethylene (TCE) and tetrachloroethylene (PCE) constitute a principal class of groundwater contaminants. Cleanup of groundwater plume source areas associated with these compounds is problematic, in part, because the compounds often exist in the subsurface as dense nonaqueous phase liquids (DNAPLs). Ganglia (or 'blobs') of DNAPL serve as persistent sources of contaminants that are difficult to locate and remediate (e.g. Fenwick and Blunt, 1998). Current understanding of the physical and chemical processes associated with dissolution of DNAPLs in the subsurface is incomplete and yet is critical for evaluating long-term behavior of contaminant migration, groundwater cleanup, and the efficacy of source area cleanup technologies. As such, a goal of this project has been to contribute to this critical understanding by investigating the multi-phase, multi-component physics of DNAPL dissolution using state-of-the-art experimental and computational techniques. Through this research, we have explored efficient and accurate conceptual and numerical models for source area contaminant transport that can be used to better inform the modeling of source area contaminants, including those at the LLNL Superfund sites, to re-evaluate existing remediation technologies, and to inspire or develop new remediation strategies. The problem of DNAPL dissolution in natural porous media must be viewed in the context of several scales (Khachikian and Harmon, 2000), including the microscopic level at which capillary forces, viscous forces, and gravity/buoyancy forces are manifested at the scale of individual pores (Wilson and Conrad, 1984; Chatzis et al., 1988), the mesoscale where dissolution rates are strongly influenced by the local hydrodynamics, and the field-scale. Historically, the physico-chemical processes associated with DNAPL dissolution have been addressed through the use of lumped mass transfer coefficients which attempt to quantify the

  1. Platelets enhance neutrophil transendothelial migration via P-selectin glycoprotein ligand-1

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Platelets are increasingly recognized as important for inflammation in addition to thrombosis. Platelets promote the adhesion of neutrophils [polymorphonuclear neutrophils (PMNs)] to the endothelium; P-selectin and P-selectin glycoprotein ligand (PSGL)-1 have been suggested to participate in these i...

  2. Biological Impact of Bioactive Glasses and Their Dissolution Products.

    PubMed

    Hoppe, Alexander; Boccaccini, Aldo R

    2015-01-01

    For many years, bioactive glasses (BGs) have been widely considered for bone tissue engineering applications due to their ability to bond to hard as well as soft tissue (a property termed bioactivity) and for their stimulating effects on bone formation. Ionic dissolution products released during the degradation of the BG matrix induce osteogenic gene expression leading to enhanced bone regeneration. Recently, adding bioactive metallic ions (e.g. boron, copper, cobalt, silver, zinc and strontium) to silicate (or phosphate and borate) glasses has emerged as a promising route for developing novel BG formulations with specific therapeutic functionalities, including antibacterial, angiogenic and osteogenic properties. The degradation behaviour of BGs can be tailored by adjusting the glass chemistry making these glass matrices potential carrier systems for controlled therapeutic ion release. This book chapter summarises the fundamental aspects of the effect of ionic dissolution products from BGs on osteogenesis and angiogenesis, whilst discussing novel BG compositions with controlled therapeutic ion release. PMID:26201273

  3. CO2 dissolution in water using long serpentine microchannels

    PubMed Central

    Cubaud, Thomas; Sauzade, Martin; Sun, Ruopeng

    2012-01-01

    The evolution of carbon dioxide bubbles dissolving in water is experimentally examined using long microchannels. We study the coupling between bubble hydrodynamics and dissolution in confined geometries. The gas impregnation process in liquid produces significant flow rearrangements. Depending on the initial volumetric liquid fraction, three operating regimes are identified, namely saturating, coalescing, and dissolving. The morphological and dynamical transition from segmented to dilute bubbly flows is investigated. Tracking individual bubbles along the flow direction is used to calculate the temporal evolution of the liquid volumetric fraction and the average flow velocity near reference bubbles over long distances. This method allows us to empirically establish the functional relationship between bubble size and velocity. Finally, we examine the implication of this relationship during the coalescing flow regime, which limits the efficiency of the dissolution process. PMID:22655006

  4. Rate limitations of lime dissolution into coal ash slag

    SciTech Connect

    L.K. Elliott; John A. Lucas; Jim Happ; John Patterson; Harry Hurst; Terry F. Wall

    2008-11-15

    The rate-limiting mechanisms of lime dissolution from a solid pellet into coal ash slag and synthetic slag was investigated using an experiment involving a rotating cylinder of lime in a liquid slag bath at temperatures of 1450-1650{degree}C. Scanning electron microscopy (SEM) analysis of the slag composition around the lime cylinder was used to determine the nature of the boundary layer surrounding the pellet and the calcium concentration profile. Predictions using shrinking core models of a cylindrical pellet were compared to experimental results, suggesting that diffusion through the slag boundary layer and the change of the phase of lime from solid to liquid in the boundary layer combine to limit the process. These results indicate that a combination of controlling steps: diffusion through the boundary layer and the phase change of lime from solid to liquid, must be considered when predicting lime dissolution rates. 24 refs., 5 figs., 3 tabs.

  5. Model of heterogeneous material dissolution in simulated biological fluid

    NASA Astrophysics Data System (ADS)

    Knyazeva, A. G.; Gutmanas, E. Y.

    2015-11-01

    In orthopedic research, increasing attention is being paid to bioresorbable/biodegradable implants as an alternative to permanent metallic bone healing devices. Biodegradable metal based implants possessing high strength and ductility potentially can be used in load bearing sites. Biodegradable Mg and Fe are ductile and Fe possess high strength, but Mg degrades too fast and Fe degrades too slow, Ag is a noble metal and should cause galvanic corrosion of the more active metallic iron - thus, corrosion of Fe can be increased. Nanostructuring should results in higher strength and can result in higher rate of dissolution/degradation from grain boundaries. In this work, a simple dissolution model of heterogeneous three phase nanocomposite material is considered - two phases being metal Fe and Ag and the third - nanopores. Analytical solution for the model is presented. Calculations demonstrate that the changes in the relative amount of each phase depend on mass exchange and diffusion coefficients. Theoretical results agree with preliminary experimental results.

  6. Spiking Neural P Systems with Neuron Division and Dissolution.

    PubMed

    Zhao, Yuzhen; Liu, Xiyu; Wang, Wenping

    2016-01-01

    Spiking neural P systems are a new candidate in spiking neural network models. By using neuron division and budding, such systems can generate/produce exponential working space in linear computational steps, thus provide a way to solve computational hard problems in feasible (linear or polynomial) time with a "time-space trade-off" strategy. In this work, a new mechanism called neuron dissolution is introduced, by which redundant neurons produced during the computation can be removed. As applications, uniform solutions to two NP-hard problems: SAT problem and Subset Sum problem are constructed in linear time, working in a deterministic way. The neuron dissolution strategy is used to eliminate invalid solutions, and all answers to these two problems are encoded as indices of output neurons. Our results improve the one obtained in Science China Information Sciences, 2011, 1596-1607 by Pan et al. PMID:27627104

  7. Dissolution Kinetics of Solids: Application with Spherical Candy

    NASA Astrophysics Data System (ADS)

    Beauchamp, Guy

    2001-04-01

    This economical and safe kinetics experiment involves the rate of dissolution of a spherical candy in water. The 2/3 order with respect to the measured mass gives students a practical example of a non-integer order usually only encountered in textbooks in free radical processes. Insight is given to the fact that in a dissolving solid sphere, the radius recedes at constant speed. This experiment also may be useful as an introduction to the concepts of solubility and diffusion in a general chemistry course. Temperature dependence on dissolution rate constants revealed an energy of activation of 23 kJ/mol (±1 kJ/mol) for different hard candies.

  8. Surface engineering of bismuth nanocrystals to counter dissolution.

    PubMed

    Chakravarty, Shatadru; Unold, Jason; Shuboni-Mulligan, Dorela D; Blanco-Fernandez, Barbara; Shapiro, Erik M

    2016-07-21

    Rapid dissolution of Bi Nanocrystals (NCs) in lysosomal conditions results in poor biocompatibility. We report that an in situ surface coating of Bi nanocrystals with Ganex® V216, a cosmetic dispersant, limits its dissolution under physiological conditions. These Bi Ganex (BiG) NCs are readily encapsulated in FDA approved polymer poly(dl-lactic-co-glycolic acid) (PLGA) by an oil-in-water emulsion technique and also undergo facile SiO2 coating. BiG NCs in BiG@PLGA and BiG@SiO2 nanoparticles dissolve slowly under physiological conditions and exhibit excellent biocompatibility, as opposed to uncoated Bi NCs. Finally, these Bi nanoconstructs are shown to be strong CT CAs, even at relatively low Bi concentrations. PMID:27356280

  9. Dissolution of alkaline earth sulfates in the presence of montmorillonite

    USGS Publications Warehouse

    Eberl, D.D.; Landa, E.R.

    1985-01-01

    In a study of the effect of montmorillonite on the dissolution of BaSO4 (barite), SrSO4 (celestite), and 226Ra from U mill tailings, it was found that: (1) More of these substances dissolve in an aqueous system that contains montmorillonite than dissolve in a similar system without clay, due to the ion exchange properties of the clay; (2) Na-montmorillonite is more effective in aiding dissolution than is Ca-montmorillonite; (3) the amount of Ra that moves from mill tailings to an exchanger increases as solution sulfate activity decreases. Leaching experiments suggest that 226Ra from H2SO4-circuit U mill tailings from Edgemont, South Dakota, is not present as pure Ra sulfate or as an impurity in anhydrite or gypsum; it is less soluble, and probably occurs as a trace constituent in barite.

  10. Bubble dissolution physics and the treatment of decompression sickness

    SciTech Connect

    Kunkle, T.D.; Beckman, E.L.

    1983-03-01

    The treatment of decompression sickness often involves both recompressing the victim and administering hyperbaric oxygen in the hope of more rapidly dissolving the bubbles which cause this malady. Although many hundreds of such treatments are conducted each year in the United States alone, the underlying physical principles governing the dissolution of such bubbles are not well understood and only empirically tested. In this paper, we present a mathematical theory of bubble dissolution that is verified by comparison with laboratory experiments. This theory suggests that the commonly employed treatment techniques would be only marginally effective, and that in many situations the bubbles that cause the disease cannot be adequately dissolved using existing techniques and facilities.

  11. Dissolution of Spent Nuclear Fuel in Carbonate-Peroxide Solution

    SciTech Connect

    Soderquist, Chuck Z.; Hanson, Brady D.

    2010-01-31

    This study shows that spent UO2 fuel can be completely dissolved in a carbonate-peroxide solution apparently without attacking the metallic Mo-Tc-Ru-Rh-Pd fission product phase. Samples of spent nuclear fuel were pulverized and sieved to a uniform size, then duplicate aliquots were weighed into beakers for analysis. One set was dissolved in near-boiling 10M nitric acid, and the other set was dissolved in a solution of ammonium carbonate and hydrogen peroxide at room temperature. All the resulting fuel solutions were then analyzed for Sr-90, Tc-99, Cs-137, plutonium, and Am-241. For all the samples, the concentrations of Cs-137, Sr-90, plutonium, and Am-241 were the same for both the nitric acid dissolution and the ammonium carbonate-hydrogen peroxide dissolution, but the technetium concentration of the ammonium carbonate-hydrogen peroxide fuel solution was only about 25% of the same fuels dissolved in hot nitric acid.

  12. Toward a universal resist dissolution model for lithography simulation

    NASA Astrophysics Data System (ADS)

    Robertson, Stewart A.; Mack, Chris A.; Maslow, Mark J.

    2001-04-01

    In lithography simulation dissolution rate equations are used to map development rate to the resist latent image. This work examines the quality of fit of four rate equations to experimental dissolution data for a wide variety of different resists ranging from medium contrast i-line novolak/DNQ materials to the state-of-the-art 248nm and 193nm chemically amplified photoresists. Three of the rate equations are routinely used for modeling: the Mack rate equation, the Enhanced Mack rate equation, and the Notch rate equation. The fourth is the recently developed Enhanced Notch model. Although each class of photoresist can be fitted reasonably well by one of the conventional rate equations, the Enhanced Notch model yields the best fit to the experimental data in all cases.

  13. Studies of thermal dissolution of RDX in TNT melt

    NASA Astrophysics Data System (ADS)

    Suvorova, Natalya; Hamilton, Virginia; Oschwald, David; Smilowitz, Laura; Henson, Bryan

    2015-06-01

    The thermal response of energetic materials is studied due to its importance in issues of material safety and surety. Secondary high explosives which melt before they thermally decompose present challenging systems to model due to the addition of material flow. Composition B is a particularly challenging system due to its multiphase nature with a low melt component (TNT) and a high melt component (RDX). The dissolution of RDX crystals in molten TNT at the temperature below RDX melting point has been investigated using hot stage microscopy and Raman spectroscopy. In this paper, we will present data on the dissolution rate of RDX crystals in molten TNT as a function of temperature above the TNT melt.

  14. Pretreatment of rice hulls by ionic liquid dissolution.

    PubMed

    Lynam, Joan G; Reza, M Toufiq; Vasquez, Victor R; Coronella, Charles J

    2012-06-01

    As a highly available waste product, rice hulls could be a starting block in replacing liquid fossil fuels. However, their silica covering can make further use difficult. This preliminary study investigates effects of dissolving rice hulls in the ionic liquids 1-ethyl-3-methylimidazolium acetate (EMIM Ac), 1-hexyl-3-methylimidazolium chloride, (HMIM Cl), and 1-allyl-3-methylimidazolium chloride (AMIM Cl), and what lignocellulosic components can be precipitated from the used ionic liquid with water and ethanol. EMIM Ac dissolution at 110 °C for 8 h was found to completely remove lignin from rice hulls, while ethanol was capable of precipitating lignin out of the used EMIM Ac. With 8h dissolution at 110 °C using HMIM Cl, approximately 20% of the cellulose in the rice hull sample can be precipitated out using water as co-solvent, while more than 60% of the hemicellulose can be precipitated with ethanol. PMID:22446050

  15. Dissolution of metal and metal oxide nanoparticles in aqueous media.

    PubMed

    Odzak, Niksa; Kistler, David; Behra, Renata; Sigg, Laura

    2014-08-01

    The dissolution of Ag (citrate, gelatin, polyvinylpyrrolidone and chitosan coated), ZnO, CuO and carbon coated Cu nanoparticles (with two nominal sizes each) has been studied in artificial aqueous media, similar in chemistry to environmental waters, for up to 19 days. The dissolved fraction was determined using DGT (Diffusion Gradients in Thin films), dialysis membrane (DM) and ultrafiltration (UF). Relatively small fractions of Ag nanoparticles dissolved, whereas ZnO dissolved nearly completely within few hours. Cu and CuO dissolved as a function of pH. Using DGT, less dissolved Ag was measured compared to UF and DM, likely due to differences in diffusion of organic complexes. Similar dissolved metal concentrations of ZnO, Cu and CuO nanoparticles were determined using DGT and UF, but lower using DM. The results indicate that there is a need to apply complementary techniques to precisely determine dissolution of nanoparticles in aqueous media. PMID:24832924

  16. Expeditious dissolution dynamic nuclear polarization without glassing agents.

    PubMed

    Lama, Bimala; Collins, James H P; Downes, Daniel; Smith, Adam N; Long, Joanna R

    2016-03-01

    The hyperpolarization of metabolic substrates at low temperature using dynamic nuclear polarization (DNP), followed by rapid dissolution and injection into an MRSI or NMR system, allows in vitro or in vivo observation and tracking of biochemical reactions and metabolites in real time. This article describes an elegant approach to sample preparation which is broadly applicable for the rapid polarization of aqueous small-molecule substrate solutions and obviates the need for glassing agents. We demonstrate its utility for solutions of sodium acetate, pyruvate and butyrate. The polarization behavior of substrates prepared using rapid freezing without glassing agents enabled a 1.5-3-fold time savings in polarization buildup, whilst removing the need for toxic glassing agents used as standard for dissolution DNP. The achievable polarization with fully aqueous substrate solutions was equal to that observed using standard approaches and glassing agents. Copyright © 2016 John Wiley & Sons, Ltd. PMID:26915792

  17. Promoting Health.

    ERIC Educational Resources Information Center

    Mechanic, David

    1990-01-01

    Argues that culture change or modification of the social structure is necessary for effective health promotion because health behavior is closely tied to basic group structures and processes. Examines the health attitudes of Mormons, low income and minority groups, and developing Islamic nations, emphasizing attitudes towards education and women.…

  18. Lithologic controls on morphology of pressure-dissolution surfaces (stylolites and dissolution seams) in Paleozoic carbonate rocks from the mideastern United States

    SciTech Connect

    Railsback, L.B. )

    1993-05-01

    Examination of pressure-dissolution surfaces (stylolites and dissolution seams) in carbonate rocks from the mideastern US demonstrates that the morphology of these surfaces varies with rock fabric. In limestones, pressure dissolution causes suturing of intergranular contacts at the microscopic scale and formation of macroscopic pressure-dissolution surfaces. Pressure dissolution thus modifies limestone fabric, and it contributes to destruction of porosity in two ways, by eliminating intergranular space at sites of dissolution and by providing cement to fill pores elsewhere. In addition to these petrologic effects, pressure-dissolution surfaces (1) can generate bedding planes, (2) can account for significant thicknesses of lost section in stratigraphic reconstructions, and (3) can be of economic significance by modifying reservoir properties, by serving as barriers to petroleum migration, and by acting as seals for reservoirs. This paper examines lithologic controls on morphology of stylolites and dissolution seams in relatively undeformed carbonate rocks. It thus addresses many of the same problems on which Buxton and Sibley (1981) focused, but it quantifies, rather than categorizes, morphology of pressure-dissolution surfaces, and examines a more general sample suite from the mideastern US.

  19. A universal rule for organic ligand exchange.

    PubMed

    You, Hongjun; Wang, Wenjin; Yang, Shengchun

    2014-11-12

    Most synthetic routes to high-quality nanocrystals with tunable morphologies predominantly employ long hydro-carbon molecules as ligands, which are detrimental for electronic and catalytic applications. Here, a rule is found that the adsorption energy of an organic ligand is related to its carbon-chain length. Using the density functional theory method, the adsorption energies of some commonly used ligand molecules with different carbon-chain lengths are calculated, including carboxylate, hydroxyl, and amine molecules adsorbed on metal or metal oxide crystal surface. The results indicate that the adsorption energy of the ligand molecule with a long carbon chain is weaker than that of a smaller molecule with same functional group. This rule provides a theoretical support for a new kind of ligand exchange method in which large organic ligand molecules can be exchanged by small molecules with same functional group to improve the catalytic properties. PMID:25335915

  20. Unravelling the relationship between degree of disorder and the dissolution behavior of milled glibenclamide.

    PubMed

    Mah, Pei T; Laaksonen, Timo; Rades, Thomas; Aaltonen, Jaakko; Peltonen, Leena; Strachan, Clare J

    2014-01-01

    Milling is an attractive method to prepare amorphous formulations as it does not require the use of solvents and is suitable for thermolabile drugs. One of the key critical quality attributes of milled amorphous formulations is their dissolution behavior. However, there are limited studies that have investigated the relationship between degree of disorder induced by milling and dissolution behavior. The main aim of this study was to identify the analytical technique used to characterize degree of disorder that correlates best with the recrystallization behavior during dissolution of milled glibenclamide samples. Solid state and surface changes during dissolution of milled glibenclamide samples were monitored in order to elucidate the processes that influence the dissolution behavior of milled glibenclamide samples. Glibenclamide was ball milled for different durations and analyzed using X-ray powder diffractometry (XRPD), Raman spectroscopy and differential scanning calorimetry (DSC). Recrystallization during dissolution of the milled amorphous materials was investigated using an in situ Raman setup. SEM was used to monitor the surfaces of the compacts during dissolution. XRPD, Raman spectroscopy and DSC indicated that glibenclamide was fully amorphous after milling for 30, 60, and 120 min, respectively. 'DSC amorphous' (i.e. fully amorphous according to the onset of crystallization obtained from DSC) glibenclamide samples experienced negligible recrystallization which had no effect on the dissolution profiles. Samples that were not 'DSC amorphous' experienced recrystallization which resulted in a decrease in dissolution rate. Unexpected elevated dissolution rate was observed initially during dissolution for samples milled for 15 to 45 min, and this was related to particle loss from surfaces of the disks during dissolution. In conclusion, the onset of crystallization obtained from DSC best predicts the recrystallization of glibenclamide during dissolution