Science.gov

Sample records for dilute salt solutions

  1. Dilute solution properties of Prunus armeniaca gum exudates: Influence of temperature, salt, and sugar.

    PubMed

    Fathi, Morteza; Mohebbi, Mohebbat; Koocheki, Arash; Hesarinejad, Mohammad Ali

    2017-03-01

    The aim of the current paper was to investigate the effect of different temperatures, salts and sugars on dilute solution properties of Prunus armeniaca gum exudates (PAGE) as a starting point to evaluate the potential utilization of this novel source of hydrocolloids in food and pharmaceutical systems. Berry number and the slope of master curve indicated that PAGE samples in all evaluated conditions were in dilute domain without coil overlapping and entanglement. Furthermore, the slope power law model also demonstrated that the molecular conformation of PAGE in all tested temperatures was close to rode-like. On the other hand, PAGE samples had random coil conformation in the presence of sugars and ions studied. Activation energy and chain flexibility of PAGE were found to be 0.83×10(7) (J/kg) and 997.3, respectively. This result revealed that temperature has a slight effect on intrinsic viscosity of PAGE solution, implying this gum can be introduced as a promising ingredient in food formulation that need to high stability against temperature. The data obtained in the present study and results thereof can be useful when considering the effect of additives generally used in food products and/or processing parameters like temperature in food systems. Copyright © 2016. Published by Elsevier B.V.

  2. Thermodynamics of Dilute Solutions.

    ERIC Educational Resources Information Center

    Jancso, Gabor; Fenby, David V.

    1983-01-01

    Discusses principles and definitions related to the thermodynamics of dilute solutions. Topics considered include dilute solution, Gibbs-Duhem equation, reference systems (pure gases and gaseous mixtures, liquid mixtures, dilute solutions), real dilute solutions (focusing on solute and solvent), terminology, standard states, and reference systems.…

  3. Mechanism of Pitting Corrosion Prevention by Nitrite in Carbon Steel Exposed to Dilute Salt Solutions

    SciTech Connect

    Zapp, P.E.

    2002-05-02

    The overall goal of this project was to develop a detailed understanding of the role of nitrite in preventing the breakdown of protective oxide on steel and on the onset of pitting, by considering the interactions of the oxidation and reduction reactions that may occur in alkaline salt solutions.

  4. Workman-Reynolds freezing potential measurements between ice and dilute salt solutions for single ice crystal faces.

    PubMed

    Wilson, P W; Haymet, A D J

    2008-09-18

    Workman-Reynolds freezing potentials have been measured for the first time across the interface between single crystals of ice 1h and dilute electrolyte solutions. The measured electric potential is a strictly nonequilibrium phenomenon and a function of the concentration of salt, freezing rate, orientation of the ice crystal, and time. When all these factors are controlled, the voltage is reproducible to the extent expected with ice growth experiments. Zero voltage is obtained with no growth or melting. For rapidly grown ice 1h basal plane in contact with a solution of 10 (-4) M NaCl the maximum voltage exceeds 30 V and decreases to zero at both high and low salt concentrations. These single-crystal experiments explain much of the data captured on this remarkable phenomenon since 1948.

  5. Silica Polymerization from Supersaturated Dilute Aqueous Solutions in the Presence of Alkaline Earth Salts.

    PubMed

    Kley, M; Kempter, A; Boyko, V; Huber, K

    2017-06-20

    The early stages of silica polymerization in aqueous solution proceed according to a mechanism based on three steps: nucleation, particle growth, and agglomeration of the particles. Application of time-resolved static and dynamic light scattering as a powerful in situ technique in combination with spectrophotometric analysis of the monomer consumption based on the molybdenum blue method was carried out to further investigate this 3-step process. Experiments were carried out at four different initial silicic acid contents covering a range between 350 and 750 ppm in the presence of either 10 mM NaCl or 5 mM of a mixture of CaCl2 and MgCl2. The process in all cases was initiated with a drop of pH to 7. Addition of the salts made possible an analysis of the impact of an electrolyte on the process. Independent of the presence or absence of salt, particle growth in step two proceeded as a monomer-addition process without being interfered significantly by Ostwald-ripening. The growing particles were compact with a homogeneous density. The size of the particles approached final values between 5 and 20 nm with the actual value increasing with decreasing initial silicic acid content. Above a certain concentration of initial silica content, which depends on the level of added salt, particle-particle interactions caused agglomeration. The presence of electrolyte shifted this level from ∼2000 ppm to a range between 500 and 750 ppm. The resulting agglomerates had a fractal dimension of 2. Independent of the conditions, particle growth could be described with a simple nucleation and growth model.

  6. Study of quantitative interactions of potato and corn starch granules with ions in diluted solutions of heavy metal salts.

    PubMed

    Szymońska, Joanna; Molenda, Marcin; Wieczorek, Jerzy

    2015-12-10

    Interactions of potato and corn starch granules with ions in diluted solutions of silver, lead, copper or iron salts were investigated. It was shown experimentally that granules accumulated the cations in amounts depending on the granule structure and water content as well as a type of both metal and counter-ions present in solution. Potato starch retained almost three times more cations compared to corn starch what was proportional to the total phosphorous content in these starches. Quantity of milligrams of cations bound by 1g of starch was inversely correlated with the cation hydration. Ag(+), Pb(2+) and Cu(2+) were connected in stoichiometric amounts of moles to semicrystalline and amorphous parts of the granules. Fe(3+) ions were accumulated in higher than stoichiometric quantities mainly in granule amorphous regions. Metal ions penetrated into granules together with anions except nitrates which remained on surface of potato starch granules. Cations facilitated the starch thermal decomposition in accordance with values of their standard redox potentials. Nitrates supported this process only in the presence of base metal cations.

  7. Mechanism of Pitting Corrosion Prevention by Nitrite in Carbon Steel Exposed to Dilute Salt Solutions

    SciTech Connect

    Philip E. Zapp; John W. Van Zee

    2002-02-01

    The research has developed a broad fundamental understanding of the inhibition action of nitrite ions in preventing nitrate pitting corrosion of carbon steel tanks containing high-level radioactive waste. This fundamental understanding can be applied to specific situations during waste removal for permanent disposition and waste tank closure to ensure that the tanks are maintained safely. The results of the research provide the insight necessary to develop solutions that prevent further degradation.

  8. Scale-up of osmotic membrane bioreactors by modeling salt accumulation and draw solution dilution using hollow-fiber membrane characteristics and operation conditions.

    PubMed

    Kim, Suhan

    2014-08-01

    A full-scale osmotic membrane bioreactor (OMBR) model was developed to simulate salt accumulation, draw solution (DS) dilution, and water flux over the hollow-fiber membrane length. The model uses the OMBR design parameters, DS properties, and forward osmosis (FO) membrane characteristics obtained from lab-scale tests. The modeling results revealed a tremendous water flux decline (10→0.82LMH) and short solids retention time (SRT: 5days) due to salt accumulation and DS dilution when OMBR is scaled up using commercially available DS and FO membrane. Simulated water flux is a result of interplay among reverse salt flux, internal and external concentration polarization (ICP and ECP). ECP adversely impacts water flux considerably in full-scale OMBR although it is often ignored in previous works. The OMBR model makes it possible to select better DS properties (higher flow rate and salt concentration) and FO membranes with higher water flux propensity in full-scale operation. Copyright © 2014 Elsevier Ltd. All rights reserved.

  9. Making and diluting stock solutions.

    PubMed

    Adams, Dany Spencer

    2008-05-01

    INTRODUCTIONFor particular experiments, certain solutions are used frequently and are therefore made up in large quantities. To minimize the volume actually occupied by these solutions, they are often made at a higher concentration than that which will be used. These concentrated solutions are referred to as stock solutions. Stock solutions save time in addition to space; when you need a solution of a given concentration, you need only dilute the stock rather than starting from scratch. This article describes the steps necessary to make and dilute stock solutions appropriately.

  10. Dilute acid/metal salt hydrolysis of lignocellulosics

    DOEpatents

    Nguyen, Quang A.; Tucker, Melvin P.

    2002-01-01

    A modified dilute acid method of hydrolyzing the cellulose and hemicellulose in lignocellulosic material under conditions to obtain higher overall fermentable sugar yields than is obtainable using dilute acid alone, comprising: impregnating a lignocellulosic feedstock with a mixture of an amount of aqueous solution of a dilute acid catalyst and a metal salt catalyst sufficient to provide higher overall fermentable sugar yields than is obtainable when hydrolyzing with dilute acid alone; loading the impregnated lignocellulosic feedstock into a reactor and heating for a sufficient period of time to hydrolyze substantially all of the hemicellulose and greater than 45% of the cellulose to water soluble sugars; and recovering the water soluble sugars.

  11. Effective charge measurements reveal selective and preferential accumulation of anions, but not cations, at the protein surface in dilute salt solutions

    PubMed Central

    Gokarn, Yatin R; Fesinmeyer, R Matthew; Saluja, Atul; Razinkov, Vladimir; Chase, Susan F; Laue, Thomas M; Brems, David N

    2011-01-01

    Specific-ion effects are ubiquitous in nature; however, their underlying mechanisms remain elusive. Although Hofmeister-ion effects on proteins are observed at higher (>0.3M) salt concentrations, in dilute (<0.1M) salt solutions nonspecific electrostatic screening is considered to be dominant. Here, using effective charge (Q*) measurements of hen-egg white lysozyme (HEWL) as a direct and differential measure of ion-association, we experimentally show that anions selectively and preferentially accumulate at the protein surface even at low (<100 mM) salt concentrations. At a given ion normality (50 mN), the HEWL Q* was dependent on anion, but not cation (Li+, Na+, K+, Rb+, Cs+, GdnH+, and Ca2+), identity. The Q* decreased in the order F− > Cl− > Br− > NO3− ∼ I− > SCN− > ClO4− ≫ SO42−, demonstrating progressively greater binding of the monovalent anions to HEWL and also show that the SO42− anion, despite being strongly hydrated, interacts directly with the HEWL surface. Under our experimental conditions, we observe a remarkable asymmetry between anions and cations in their interactions with the HEWL surface. PMID:21432935

  12. Dynamics of dilute solutions of poly(aspartic acid) and its sodium salt elucidated from atomistic molecular dynamics simulations with explicit water.

    PubMed

    Ramachandran, Sanoop; Katha, Anki Reddy; Kolake, Subramanya Mayya; Jung, Bokyung; Han, Sungsoo

    2013-11-07

    The use of forward osmosis (FO) process for seawater desalination has attracted tremendous interest in recent years. Besides the manufacture of suitable membranes, the major technical challenge in the efficient deployment of the FO technology lies in the development of a suitable "draw solute". Owing to its inherent advantages, poly(aspartic acid) has arisen to be an attractive candidate for this purpose. However, an investigation of its molecular level properties has not been studied in detail. In this paper, the dynamics of poly(aspartic acid) and its sodium salt in the dilute concentration regime have been reported. The quantification of the polymer conformational properties, its solvation behavior, and the counterion dynamics are studied. The neutral polymer shows a preferentially coiled structure whereas the fully ionized polymer has an extended structure. Upon comparing with poly(acrylic acid) polymer, another polymer which has been used as a draw solute, poly(aspartic acid) forms more number of hydrogen bonds as well as fewer ion pairs.

  13. Statistical mechanics of sum frequency generation spectroscopy for the liquid-vapor interface of dilute aqueous salt solutions

    NASA Astrophysics Data System (ADS)

    Noah-Vanhoucke, Joyce; Smith, Jared D.; Geissler, Phillip L.

    2009-02-01

    We demonstrate a theoretical description of vibrational sum frequency generation (SFG) at the boundary of aqueous electrolyte solutions. This approach identifies and exploits a simple relationship between SFG lineshapes and the statistics of molecular orientation and electric field. Our computer simulations indicate that orientational averages governing SFG susceptibility do not manifest ion-specific shifts in local electric field, but instead, ion-induced polarization of subsurface layers. Counterbalancing effects are obtained for monovalent anions and cations at the same depth. Ions held at different depths induce an imbalanced polarization, suggesting that ion-specific effects can arise from weak, long-ranged influence on solvent organization.

  14. The transition from dilute electrolyte aqueous solution to molten salt in geologic fluids: evidence from calcite solubility measurement in Na-halide solutions at 8 kbar and 700 °C

    NASA Astrophysics Data System (ADS)

    Galvez, M.; Manning, C. E.

    2014-12-01

    Fluids are major agents of mass and heat transport in the Earth crust and in subduction zones. Fluid inclusions, metasomatic field relations and experimental evidence suggest that these fluids can contain important ligands, including halogens, sulfates, sulfides, etc. The ligands participate in the complexation of rock-forming elements during mineral dissolution to high-T and P. Although models of high- element metasomatism typically assume that H2O dominates the fluid's solvent properties, however, H2O may be a relatively minor component in the high-PT brines that are increasingly recognized in the lower crust and mantle. Understanding the evolution of solubility mechanisms as fluids change from dilute aqueous solutions to salt-rich brines is hindered by the absence of experimental investigation of this transition. To address this problem, we conducted experiments on the solubility of calcite in sodium-halide solutions at 8 kbar and 700 °C using hydrothermal piston-cylinder weight-loss methods. Investigated salts were NaL , where L=F, Cl, Br, I, at concentrations ranging from 0.15 molal to 20 molal (XNaL ~ 0.3). At these conditions, the fluid is a single supercritical fluid phase . Run durations were 4 to 20 hours. Results demonstrate systematic trends with ligand ionic size, and locate a major mechanistic transition in the vicinity of XNaL~ 0.1 for all calcite-H2O-NaL systems. At lower than this critical composition (Xcrit), calcite solubility displays a pronounced concave shape indicating involvement of water during the dissolution process. At XNaL> Xcrit , the shape becomes convex with no apparent effect of decreased H2O activity in the fluid. The solubility patterns suggest that the solvent properties are dominated by those of H2O at XNaL< Xcrit, but at XNaL> Xcrit, H2O is a solute in a solution behaving as a molten salt. Geological evidence suggests that salt concentrations may reach values similar to or greater than Xcrit in a range of metamorphic and

  15. Nematic ordering in dilute solutions of rodlike polyelectrolytes

    NASA Astrophysics Data System (ADS)

    Potemkin, Igor I.; Khokhlov, Alexei R.

    2004-06-01

    Quantitative theory of orientational behavior of rodlike polyelectrolytes in dilute solution is developed. We find that in salt-free solutions many-body Coulomb interactions between macro- and counterions favor nematic ordering. It is shown that the orientationally isotropic phase of the solution becomes unstable toward nematic ordering at polymer concentration smaller than the overlap concentration. Our predictions are consistent with experimental observations for synthetic polyelectrolytes poly(p-phenylene)sulfonates in aqueous solutions.

  16. Ammonia Solubility in High Concentration Salt Solutions

    SciTech Connect

    HEDENGREN, D.C.

    2000-02-01

    Solubility data for ammonia in water and various dilute solutions are abundant in the literature. However, there is a noticeable lack of ammonia solubility data for high salt, basic solutions of various mixtures of salts including those found in many of the Hanford Washington underground waste tanks. As a result, models based on solubility data for dilute salt solutions have been used to extrapolate to high salt solutions. These significant extrapolations need to be checked against actual laboratory data. Some indirect vapor measurements have been made. A more direct approach is to determine the ratio of solubility of ammonia in water to its solubility in high salt solutions. In various experiments, pairs of solutions, one of which is water and the other a high salt solution, are allowed to come to equilibrium with a common ammonia vapor pressure. The ratio of concentrations of ammonia in the two solutions is equal to the ratio of the respective ammonia solubilities (Henry's Law constants) at a given temperature. This information can then be used to refine the models that predict vapor space compositions of ammonia. Ammonia at Hanford is of concern because of its toxicity in the environment and its contribution to the flammability of vapor space gas mixtures in waste tanks.

  17. Equilibrium sedimentation profile of dilute, salt-free charged colloids.

    PubMed

    Wang, Tzu-Yu; Li, Hsien-Tsung; Sheng, Yu-Jane; Tsao, Heng-Kwong

    2008-11-28

    The sedimentation profile of a dilute colloidal solution follows the barometric distribution owing to the balance between gravitational force and thermal fluctuation. However, the electrostatic interactions may lead to significant deviation even in the low volume fraction limit (e.g., 10(-5)). On the basis of Monte Carlo simulations for a dilute, salt-free colloidal dispersion, five regimes can be identified through the resulting colloidal sedimentation profile and the counterion distribution. The electrostatic interactions depends on the Coulomb strength E(c) defined as the ratio of the Bjerrum length to the colloid size. At weak colloid-ion attractions (small E(c)), counterions tend to distribute uniformly in the container. However, both barometric and inflated profiles of colloids can be observed. On the contrary, at strong colloid-ion attraction (large E(c)), counterions accumulate in the vicinity of the colloids. Significant counterion condensation effectively decreases the strength of colloid-colloid repulsion and barometric profile of colloids can be obtained as well. As a result, the sedimentation profile and counterion distribution are indicative of the strength of effective colloid-colloid and colloid-ion interactions. It is also found that local electroneutrality condition is generally not satisfied and charge separation (or internal electric field) is neither a sufficient nor necessary condition for nonbarometric distributions.

  18. Neutron scattering study of dilute supercritical solutions

    SciTech Connect

    Cochran, H.D.; Wignall, G.D.; Shah, V.M.; Londono, J.D.; Bienkowski, P.R.

    1994-10-01

    Dilute solutions in supercritical solvents exhibit interesting microstructures that are related to their dramatic macroscopic behavior. In typical attractive solutions, solutes are believed to be surrounded by clusters of solvent molecules, and solute molecules are believed to congregate in the vicinity of one another. Repulsive solutions, on the other hand, exhibit a local region of reduced solvent density around the solute with solute-solute congregation. Such microstructures influence solubility, partial molar volume, reaction kinetics, and many other properties. We have undertaken to observe these interesting microstructures directly by neutron scattering experiments on dilute noble gas systems including Ar. The three partial structure factors for such systems and the corresponding pair correlation functions can be determined by using the isotope substitution technique. The systems studied are uniquely suited for our objectives because of the large coherent neutron scattering length of the isotope {sup 36}Ar and because of the accurate potential energy functions that are available for use in molecular simulations and theoretical calculations to be compared with the scattering results. We will describe our experiment, the unique apparatus we have built for it, and the neutron scattering results from our initial allocations of beam time. We will also describe planned scattering experiments to follow those with noble gases, including study of long-chain molecules in supercritical solvents. Such studies will involve hydrocarbon mixtures with and without deuteration to provide contrast.

  19. Dynamic scaling of dilute polymer solutions

    SciTech Connect

    Marqusee, J.A.; Deutch, J.M.

    1981-04-15

    Dynamic scaling relations are presented for the diffusion coefficient and intrinsic viscosity of dilute polymer solutions in D dimensions. The functional integration description of Adler and Freed is used with the correct D-dimensional hydrodynamic interaction and assumptions of power law dependence to obtain the scaling relations. Recursion relations for the exponents are determined in the asymptotic region of large N by an interdimensional scaling argument. 19 references.

  20. Low shear viscosity of dilute polymer solutions

    SciTech Connect

    Chiou, C.S.; Gordon, R.J.

    1980-09-01

    A modification of a viscometer originally proposed by Zimm and Crothers is studied, which may be used to measure ultra low shear viscosity for highly dilute polymer solutions. This may provide useful information on polymer coil dimensions and relaxation time. Use of the low shear viscosity data leads to large value of relaxation time induced by polymer addition to a concentration of only 2 to 3 ppM by wt. This finding is consistent with the marked viscoelastic effects exhibited by these solutions.

  1. Electrochromic Salts, Solutions, and Devices

    DOEpatents

    Burrell, Anthony K.; Warner, Benjamin P.; McClesky, T. Mark

    2008-10-14

    Electrochromic salts. Electrochromic salts of dicationic viologens such as methyl viologen and benzyl viologen associated with anions selected from bis(trifluoromethylsulfonyl)imide, bis(perfluoroethylsulfonyl)imide, and tris(trifluoromethylsulfonyl)methide are produced by metathesis with the corresponding viologen dihalide. They are highly soluble in molten quarternary ammonium salts and together with a suitable reductant provide electrolyte solutions that are used in electrochromic windows.

  2. Electrochromic Salts, Solutions, and Devices

    DOEpatents

    Burrell, Anthony K.; Warner, Benjamin P.; McClesky, T. Mark

    2008-11-11

    Electrochromic salts. Electrochromic salts of dicationic viologens such as methyl viologen and benzyl viologen associated with anions selected from bis(trifluoromethylsulfonyl)imide, bis(perfluoroethylsulfonyl)imide, and tris(trifluoromethylsulfonyl)methide are produced by metathesis with the corresponding viologen dihalide. They are highly soluble in molten quarternary ammonium salts and together with a suitable reductant provide electrolyte solutions that are used in electrochromic windows.

  3. Electrochromic salts, solutions, and devices

    DOEpatents

    Burrell, Anthony K.; Warner, Benjamin P.; McClesky,7,064,212 T. Mark

    2006-06-20

    Electrochromic salts. Electrochromic salts of dicationic viologens such as methyl viologen and benzyl viologen associated with anions selected from bis(trifluoromethylsulfonyl)imide, bis(perfluoroethylsulfonyl)imide, and tris(trifluoromethylsulfonyl)methide are produced by metathesis with the corresponding viologen dihalide. They are highly soluble in molten quarternary ammonium salts and together with a suitable reductant provide electrolyte solutions that are used in electrochromic windows.

  4. Random bilayer phases of dilute surfactant solutions

    NASA Astrophysics Data System (ADS)

    Cates, M. E.; Roux, D.

    1990-12-01

    Surfactant molecules in dilute solution may aggregate reversibly into extended structures. For suitably chosen molecules, the preferred packing involves a locally flat bilayer which tends to wander entropically at large distances. At low temperatures (and/or high concentrations) the system forms a stack of flat sheets with one-dimensional quasi-long range order (a smectic liquid crystal), but at high temperatures or low concentrations, the stack can melt into a random surface structure that resembles a multiply connected labyrinth or 'sponge' of bilayer in a sea of solvent. Recent theoretical and experimental progress in understanding the properties of the sponge is reviewed. The authors argue that the sponge phase may provide a good system for the study of various liquid-state critical phenomena.

  5. Protein aggregation in salt solutions

    PubMed Central

    Kastelic, Miha; Kalyuzhnyi, Yurij V.; Hribar-Lee, Barbara; Dill, Ken A.; Vlachy, Vojko

    2015-01-01

    Protein aggregation is broadly important in diseases and in formulations of biological drugs. Here, we develop a theoretical model for reversible protein–protein aggregation in salt solutions. We treat proteins as hard spheres having square-well-energy binding sites, using Wertheim’s thermodynamic perturbation theory. The necessary condition required for such modeling to be realistic is that proteins in solution during the experiment remain in their compact form. Within this limitation our model gives accurate liquid–liquid coexistence curves for lysozyme and γ IIIa-crystallin solutions in respective buffers. It provides good fits to the cloud-point curves of lysozyme in buffer–salt mixtures as a function of the type and concentration of salt. It than predicts full coexistence curves, osmotic compressibilities, and second virial coefficients under such conditions. This treatment may also be relevant to protein crystallization. PMID:25964322

  6. Hydrodynamic behavior and dilute solution properties of Ulva fasciata algae polysaccharide.

    PubMed

    Shao, Ping; Zhu, Yueqiong; Qin, Minpu; Fang, Zhongxiang; Sun, Peilong

    2015-12-10

    Hydrodynamic behavior and dilute solution properties of Ulva fasciata polysaccharides (UFP) were investigated. Experimental results indicated that the variation of hydrodynamic behavior of UFP was affected by the type and concentration of salts. The specific viscosity of UFP in water increased with its increasing concentration. The slopes of the double logarithmic plots in the dilute and semi-dilute solutions were 0.86 and 1.99, respectively. The molecular conformation could be semi-flexible like. Huggins plots of UFP solutions in the presence of salts including Na(+), K(+), Mg(2+) and Ca(2+) showed that the hydrodynamic behavior of the UFP was strongly affected by the types and strength of salt ion. The stiffness parameter of UFP solution was 0.1149, higher than that of other reported polysaccharides, indicating that it could tolerate high salt concentration. Dynamic rheological results suggested that 0.5% UFP solution was a typical characteristic of polymer solution in the dilute region. This work provided some valuable and fundamental information in understanding the physicochemical properties of UFP solution. Copyright © 2015 Elsevier Ltd. All rights reserved.

  7. Ionic liquids behave as dilute electrolyte solutions

    PubMed Central

    Gebbie, Matthew A.; Valtiner, Markus; Banquy, Xavier; Fox, Eric T.; Henderson, Wesley A.; Israelachvili, Jacob N.

    2013-01-01

    We combine direct surface force measurements with thermodynamic arguments to demonstrate that pure ionic liquids are expected to behave as dilute weak electrolyte solutions, with typical effective dissociated ion concentrations of less than 0.1% at room temperature. We performed equilibrium force–distance measurements across the common ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C4mim][NTf2]) using a surface forces apparatus with in situ electrochemical control and quantitatively modeled these measurements using the van der Waals and electrostatic double-layer forces of the Derjaguin–Landau–Verwey–Overbeek theory with an additive repulsive steric (entropic) ion–surface binding force. Our results indicate that ionic liquids screen charged surfaces through the formation of both bound (Stern) and diffuse electric double layers, where the diffuse double layer is comprised of effectively dissociated ionic liquid ions. Additionally, we used the energetics of thermally dissociating ions in a dielectric medium to quantitatively predict the equilibrium for the effective dissociation reaction of [C4mim][NTf2] ions, in excellent agreement with the measured Debye length. Our results clearly demonstrate that, outside of the bound double layer, most of the ions in [C4mim][NTf2] are not effectively dissociated and thus do not contribute to electrostatic screening. We also provide a general, molecular-scale framework for designing ionic liquids with significantly increased dissociated charge densities via judiciously balancing ion pair interactions with bulk dielectric properties. Our results clear up several inconsistencies that have hampered scientific progress in this important area and guide the rational design of unique, high–free-ion density ionic liquids and ionic liquid blends. PMID:23716690

  8. Ionic liquids behave as dilute electrolyte solutions.

    PubMed

    Gebbie, Matthew A; Valtiner, Markus; Banquy, Xavier; Fox, Eric T; Henderson, Wesley A; Israelachvili, Jacob N

    2013-06-11

    We combine direct surface force measurements with thermodynamic arguments to demonstrate that pure ionic liquids are expected to behave as dilute weak electrolyte solutions, with typical effective dissociated ion concentrations of less than 0.1% at room temperature. We performed equilibrium force-distance measurements across the common ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C4mim][NTf2]) using a surface forces apparatus with in situ electrochemical control and quantitatively modeled these measurements using the van der Waals and electrostatic double-layer forces of the Derjaguin-Landau-Verwey-Overbeek theory with an additive repulsive steric (entropic) ion-surface binding force. Our results indicate that ionic liquids screen charged surfaces through the formation of both bound (Stern) and diffuse electric double layers, where the diffuse double layer is comprised of effectively dissociated ionic liquid ions. Additionally, we used the energetics of thermally dissociating ions in a dielectric medium to quantitatively predict the equilibrium for the effective dissociation reaction of [C4mim][NTf2] ions, in excellent agreement with the measured Debye length. Our results clearly demonstrate that, outside of the bound double layer, most of the ions in [C4mim][NTf2] are not effectively dissociated and thus do not contribute to electrostatic screening. We also provide a general, molecular-scale framework for designing ionic liquids with significantly increased dissociated charge densities via judiciously balancing ion pair interactions with bulk dielectric properties. Our results clear up several inconsistencies that have hampered scientific progress in this important area and guide the rational design of unique, high-free-ion density ionic liquids and ionic liquid blends.

  9. A modified Lowry protein test for dilute protein solutions

    Treesearch

    Garold F. Gregory; Keith F. Jensen

    1971-01-01

    A modified Lowry protein test for dilute protein solutions modified Lowry protein test was compared with the standard Lowry protein test. The modified test was found to give estimates of protein concentration that were as good as the standard test and has the advange that proteins can be measured in very dilute solutions.

  10. [Formation of oxalate in oxaliplatin injection diluted with infusion solutions].

    PubMed

    Eto, Seiji; Yamamoto, Kie; Shimazu, Kounosuke; Sugiura, Toshimune; Baba, Kaori; Sato, Ayaka; Goromaru, Takeshi; Hagiwara, Yoshiaki; Hara, Keiko; Shinohara, Yoshitake; Takahashi, Kojiro

    2014-01-01

    Oxaliplatin use can cause acute peripheral neuropathy characterized by sensory paresthesias, which are markedly exacerbated by exposure to cold temperatures, and is a dose-limiting factor in the treatment of colorectal cancer.Oxalate is eliminated in a series of nonenzymatic conversions of oxaliplatin in infusion solutions or biological fluids.Elimination of oxalate from oxaliplatin has been suggested as one of the reasons for the development of acute neuropathy.In this study, we developed a high-performance liquid chromatography(HPLC)-based method to detect oxalate formation, and investigated the time dependent formation of oxalate in oxaliplatin diluted with infusion solutions.The results obtained showed that the amount of oxalate in the solution corresponded to 1.6% of oxaliplatin 8 h after oxaliplatin dilution with a 5% glucose solution. On the other hand, oxalate formation from oxaliplatin diluted with a saline solution was ten-fold higher than that from oxaliplatin diluted with the 5% glucose solution.Most patients who were intravenously injected with oxaliplatin experienced venous pain.As a preventive measure against venous pain, dexamethasone was added to the oxaliplatin injection.We measured the amount of oxalate formed in the dexamethasone-containing oxaliplatin injection diluted with a 5% glucose solution.The amount of oxalate formed when dexamethasone was added did not differ significantly from that formed when dexamethasone was not added.Thus, there are no clinical problems associated with the stability of oxaliplatin solutions.

  11. Terahertz absorption of dilute aqueous solutions.

    PubMed

    Heyden, Matthias; Tobias, Douglas J; Matyushov, Dmitry V

    2012-12-21

    Absorption of terahertz (THz) radiation by aqueous solutions of large solutes reports on the polarization response of their hydration shells. This is because the dipolar relaxation of the solute is dynamically frozen at these frequencies, and most of the solute-induced absorption changes, apart from the expulsion of water, are caused by interfacial water. We propose a model expressing the dipolar response of solutions in terms of a single parameter, the interface dipole moment induced in the interfacial water by electromagnetic radiation. We apply this concept to experimental THz absorption of hydrated sugars, amino acids, and proteins. None of the solutes studied here follow the expectations of dielectric theories, which predict a negative projection of the interface dipole on the external electric field. We find that this prediction is not able to describe the available experimental data, which instead suggests a nearly zero interface dipole for sugars and a more diverse pattern for amino acids. Hydrophobic amino acids, similarly to sugars, give rise to near zero interface dipoles, while strongly hydrophilic ones are best described by a positive projection of the interface dipole on the external field. The sign of the interface dipole is connected to the slope of the absorption coefficient with the solute concentration. A positive slope, implying an increase in the solution polarity relative to water, mirrors results frequently reported for protein solutions. We therefore use molecular dynamics simulations of hydrated glucose and lambda repressor protein to calculate the interface dipole moments of these solutes and the concentration dependence of the THz absorption. The absorption at THz frequencies increases with increasing solute concentration in both cases, implying a higher polarity of the solution compared to bulk water. The structure of the hydration layer, extracted from simulations, is qualitatively similar in both cases, with spatial correlations

  12. Dynamic dissolution of halite rock during flow of diluted saline solutions

    NASA Astrophysics Data System (ADS)

    Weisbrod, N.; Alon-Mordish, C.; Yechieli, Y.

    2010-12-01

    Continuous recession of the Dead Sea (DS) water level influences the location of the underground interface between fresh aquifer water and DS water (DSW). As the interface moves, salt layers are exposed to and potentially dissolved by dilute solutions. This process has resulted in the formation of hundreds of sinkholes along the DS shore during the last decade. Very little is known about the dynamics of salt dissolution during flow of dilute saline solution. Patterns and kinetics of halite dissolution were examined during the flow of unsaturated DSW solutions in a series of laboratory experiments. Flow experiments were carried out in natural halite cores taken from boreholes drilled along the DS shore (15-30 m deep). First, the permeability of the core was determined using 100% DSW. Next, 100% DSW was replaced by diluted DSW and changes in permeability and flow were studied. Dissolution patterns were monitored by digital camera and computerized tomography (CT). The mass of NaCl dissolved from the core was determined based on outlet solution density. In one set of experiments, a 2-mm wide channel was drilled through the length of the entire core prior to flow to study dissolution along a preexisting channel. Our results show that above a critical flow velocity (0.01ml/min), dissolution developed along preferential pathways and formed distinct channels. The channel structure related to the halite properties and internal heterogeneities. Under flow velocity less than 0.01 ml/min, dissolution developed as a propagating front. At these low velocities, salt reprecipitation in pores often resulted in clogging and cessation of flow through the salt core. The effect of solution density on the dissolution pattern was also found to be important, as more channels developed upward due to gravitational fractionation. In summary, our results suggest that dissolution through massive salt layers will occur in very specific locations where resistance to flow is at a minimum. These

  13. Dilute Bicellar Solutions for Structural NMR Work

    NASA Astrophysics Data System (ADS)

    Struppe, Jochem; Vold, Regitze R.

    1998-12-01

    Deuterium NMR spectroscopy has been employed to characterize the concentration dependence of orientational order in DMPC/DHPC bicellar solutions with molar ratiosq= [DMPC]/[DHPC] = 3.3, 2.7, and 2.3. The stability of a discotic nematic phase can, in general, be predicted from a simple Onsager picture involving the size and concentration of the mesogenic unit, but for the bicellar solutions this model is not adequate. Specifically, macroscopic alignment is observed at total lipid concentrations well below that, 1-10% (w/w) predicted by Onsager's model. Thus the discotic nematic phase is stable to ≈3-5% (w/w) forq= 3.3-2.3, and the bicellar order is highest just before phase separation occurs at the minimum total phospholipid concentration. This implies the presence of a DHPCbic⇄ DHPCsolequilibrium in establishing bicellar size, thereby extending the range of concentrations for which alignment occurs. Bicellar morphology has been verified for a wide range of concentrations, temperatures, andq-values, but as viscosity measurements demonstrate, major morphological changes take place as the temperature is reduced below 30°C.

  14. Radiolysis of paracetamol in dilute aqueous solution

    NASA Astrophysics Data System (ADS)

    Szabó, László; Tóth, Tünde; Homlok, Renáta; Takács, Erzsébet; Wojnárovits, László

    2012-09-01

    Using radiolytic experiments hydroxyl radical (main reactant in advanced oxidation processes) was shown to effectively destroy paracetamol molecules. The basic reaction is attachment to the ring. The hydroxy-cyclohexadienyl radical produced in the further reactions may transform to hydroxylated paracetamol derivatives or to quinone type molecules and acetamide. The initial efficiency of aromatic ring destruction in the absence of dissolved O2 is c.a. 10%. The efficiency is 2-3 times higher in the presence of O2 due to its reaction with intermediate hydroxy-cyclohexadienyl radical and the subsequent ring destruction reactions through peroxi radical. Upon irradiation the toxicity of solutions at low doses increases with the dose and then at higher doses it decreases. This is due to formation of compounds with higher toxicity than paracetamol (e.g. acetamide, hidroquinone). These products, however, are highly sensitive to irradiation and degrade easily.

  15. SEPARATION OF INORGANIC SALTS FROM ORGANIC SOLUTIONS

    DOEpatents

    Katzin, L.I.; Sullivan, J.C.

    1958-06-24

    A process is described for recovering the nitrates of uranium and plutonium from solution in oxygen-containing organic solvents such as ketones or ethers. The solution of such salts dissolved in an oxygen-containing organic compound is contacted with an ion exchange resin whereby sorption of the entire salt on the resin takes place and then the salt-depleted liquid and the resin are separated from each other. The reaction seems to be based on an anion formation of the entire salt by complexing with the anion of the resin. Strong base or quaternary ammonium type resins can be used successfully in this process.

  16. Salting-out and Salting-in in Polyelectrolyte Solutions

    NASA Astrophysics Data System (ADS)

    Zhang, Pengfei; Wu, Jianzhong; Wang, Zhen-Gang

    The phase behavior of polyelectrolyte (PE) solutions is governed by complicated interplay involving the mixing entropy, excluded volume, chain connectivity, and electrostatic interactions. Here we study the phase behavior of PE solutions in both salt-free condition and with added salt using a liquid-state (LS) theory based thermodynamic model. The LS model accounts or the hard-core repulsion by the Canahan-Starling equation of state, correlations due to chain connectivity by the first-order thermodynamic perturbation theory, and electrostatic correlations by the mean-spherical approximation. In comparison to the prediction from the well-known Voorn-Overbeek theory, the LS model predicts loop-type binodal curves in the salt-PE concentration diagram at temperatures slightly above the critical temperature of PE solution in salt-free case, consistent with the experimental study. The phase separated region shrinks with increasing temperature. Three scenarios of salting-out and salting-in phenomenon are predicted with addition of salts based, depending on the PE concentration.

  17. Electrolysis of dilute sodium chloride solution in a diaphragm cell

    SciTech Connect

    Kubasov, V.L.; Ivanter, I.A.; Druzhinin, E.A.; Vorob'eva, V.B.

    1986-02-10

    In some cases, as in the production of iodine and bromine, dilute solutions of sodium chloride remain unutilized. In view of the existence of large amounts of unutilized spent sodium chloride solutions and their harmful effect when discharged into the environment, it is desirable to develop a process for production of chlorine and alkali with high current efficiencies, satisfying industrial requirements, from dilute sodium chloride solutions. The authors have therefore studied electrolysis of solutions containing 160 and 180 kg/m/sup 3/ of sodium chloride, having pH of 11.0-11.5, close in composition to solutions from the Cheleken chemical factory. The chlorine and alkali current efficiencies and the compositions of the anolyte, catholyte, and anode gas were determined.

  18. Stability of dilute oral morphine solution for neonatal abstinence syndrome.

    PubMed

    Sauberan, Jason; Rossi, Steven; Kim, Jae H

    2013-01-01

    Oral morphine is a recommended option for the treatment of neonatal abstinence syndrome (NAS). Commercially available oral morphine solution products in the United States are not formulated in concentrations appropriate for use in neonates. To test the stability of a diluted oral morphine solution for treatment of NAS. Ethanol-free morphine 2 mg/mL oral solution was diluted to 0.4 mg/mL with sterile water and stored in a light protected container at room temperature (20°C-25°C). The change in morphine concentration over time was measured by liquid chromatography mass spectrometry with simultaneous ultraviolet diode array detection. : The test morphine solution retained 107% of its original concentration after 60 days. Extemporaneously prepared 0.4 mg/mL oral morphine solution is suitable for use in the treatment of NAS as a potentially safer alternative to opium-containing agents.

  19. Motor-mediated microtubule self-organization in dilute and semi-dilute filament solutions.

    SciTech Connect

    Swaminathan, S.; Ziebert, F.; Aranson, I. S.; Karpeev, D.

    2011-01-01

    We study molecular motor-induced microtubule self-organization in dilute and semi-dilute filament solutions. In the dilute case, we use a probabilistic model of microtubule interaction via molecular motors to investigate microtubule bundle dynamics. Microtubules are modeled as polar rods interacting through fully inelastic, binary collisions. Our model indicates that initially disordered systems of interacting rods exhibit an orientational instability resulting in spontaneous ordering. We study the existence and dynamic interaction of microtubule bundles analytically and numerically. Our results reveal a long term attraction and coalescing of bundles indicating a clear coarsening in the system; microtubule bundles concentrate into fewer orientations on a slow logarithmic time scale. In semi-dilute filament solutions, multiple motors can bind a filament to several others and, for a critical motor density, induce a transition to an ordered phase with a nonzero mean orientation. Motors attach to a pair of filaments and walk along the pair bringing them into closer alignment. We develop a spatially homogenous, mean-field theory that explicitly accounts for a force-dependent detachment rate of motors, which in turn affects the mean and the fluctuations of the net force acting on a filament. We show that the transition to the oriented state can be both continuous and discontinuous when the force-dependent detachment of motors is important.

  20. Reusable chelating resins concentrate metal ions from highly dilute solutions

    NASA Technical Reports Server (NTRS)

    Bauman, A. J.; Weetal, H. H.; Weliky, N.

    1966-01-01

    Column chromatographic method uses new metal chelating resins for recovering heavy-metal ions from highly dilute solutions. The absorbed heavy-metal cations may be removed from the chelating resins by acid or base washes. The resins are reusable after the washes are completed.

  1. Reverse osmosis separation of radium from dilute aqueous solutions

    SciTech Connect

    Subramanian, K.S.; Sastri, V.S.

    1980-03-01

    Porous cellulose acetate membranes obtained from Osmonics Inc. were characterized in terms of pure water permeability constant, solute transport parameter, and mass transfer coefficient with aqueous sodium chloride solution as the reference system. Reverse osmosis separation behavior of radium-226 as nitrate, chloride, and sulfate salts was studied. Reverse osmosis method of removing radium-226 from aqueous solutions has been compared with other methods, and it has been shown to be one of the best methods for alleviating radium contamination problems.

  2. Coordination chemistry in fused-salt solutions

    NASA Technical Reports Server (NTRS)

    Gruen, D. M.

    1969-01-01

    Spectrophotometric work on structural determinations with fused-salt solutions is reviewed. Constraints placed on the method, as well as interpretation of the spectra, are discussed with parallels drawn to aqueous spectrophotometric curves of the same materials.

  3. Process of concentrating ethanol from dilute aqueous solutions thereof

    DOEpatents

    Oulman, C.S.; Chriswell, C.D.

    1981-07-07

    Relatively dilute aqueous solutions of ethanol are concentrated by passage through a bed of a crystalline silica polymorph, such as silicalite, to adsorb the ethanol with residual dilute feed in contact with the bed, which is displaced by passing concentrated aqueous ethanol through the bed without displacing the adsorbed ethanol. A product concentrate is then obtained by removing the adsorbed ethanol from the bed together with at least a portion of the concentrated aqueous ethanol used as the displacer liquid. This process permits ethanol to be concentrated from dilute fermentation beers, which may contain from 6 to 10% ethanol, to obtain a concentrate product at very low energy cost having an ethanol concentration in excess of 95%, such as a concentration of from 98 to 99.5%. 5 figs.

  4. Process of concentrating ethanol from dilute aqueous solutions thereof

    DOEpatents

    Oulman, Charles S. [Ames, IA; Chriswell, Colin D. [Slater, IA

    1981-07-07

    Relatively dilute aqueous solutions of ethanol are concentrated by passage through a bed of a crystalline silica polymorph, such as silicalite, to adsorb the ethanol with residual dilute feed in contact with the bed, which is displaced by passing concentrated aqueous ethanol through the bed without displacing the adsorbed ethanol. A product concentrate is then obtained by removing the adsorbed ethanol from the bed together with at least a portion of the concentrated aqueous ethanol used as the displacer liquid. This process permits ethanol to be concentrated from dilute fermentation beers, which may contain from 6 to 10% ethanol, to obtain a concentrate product at very low energy cost having an ethanol concentration in excess of 95%, such as a concentration of from 98 to 99.5%.

  5. Separation and concentration of lower alcohols from dilute aqueous solutions

    DOEpatents

    Moore, Raymond H.; Eakin, David E.; Baker, Eddie G.; Hallen, Richard T.

    1991-01-01

    A process for producing, from a dilute aqueous solution of a lower (C.sub.1 -C.sub.5) alcohol, a concentrated liquid solution of the alcohol in an aromatic organic solvent is disclosed. Most of the water is removed from the dilute aqueous solution of alcohol by chilling sufficiently to form ice crystals. Simultaneously, the remaining liquid is extracted at substantially the same low temperature with a liquid organic solvent that is substantially immiscible in aqueous liquids and has an affinity for the alcohol at that temperature, causing the alcohol to transfer to the organic phase. After separating the organic liquid from the ice crystals, the organic liquid can be distilled to enrich the concentration of alcohol therein. Ethanol so separated from water and concentrated in an organic solvent such as toluene is useful as an anti-knock additive for gasoline.

  6. Dilute nitric or nitrous acid solution containing halide ions as effective media for pure gold dissolution.

    PubMed

    Hojo, Masashi; Yamamoto, Masahiko; Okamura, Kei

    2015-08-14

    The greatly enhanced oxidation ability of dilute aqueous nitric acid (0.10-2.0 mol L(-1)) containing bromide and iodide salts as well as chloride salts has been examined based on the dissolution kinetics of pure gold at 30-60 °C. It has been found that bromide salts are more effective than chloride salts in gaining the ability of dissolving gold in dilute aqueous nitric acid solution. At 60 °C, a piece of gold-wire (ca. 20 mg) is dissolved in 20 mL of as low as 0.10 mol L(-1) HNO3 solution containing 1.0-5.0 mol L(-1) NaBr and the dissolution rate constant, log(k/s(-1)), increases linearly (from -5.78 to -4.52) with the increasing NaBr concentration. The addition of organic solvents, such as acetonitrile and acetic acid, causes acceleration of gold dissolution in LiBr and NaBr solutions. With increasing MeCN contents, for instance, the log(k/s(-1)) value of 0.10 mol L(-1) HNO3 solution containing 2.0 mol L(-1) NaBr increases linearly from -5.30 to -4.61 at 30% (v/v) MeCN. The bromide salts affect the gold dissolution rate constant in the order of KBr < NaBr < LiBr < CaBr2. With increasing NaI concentration (0.20-3.0 mol L(-1)), some acceleration in log(k/s(-1)) of 0.50 or 1.0 mol L(-1) HNO3 solution has been observed; however, the slope of acceleration as the function of NaI concentration is much smaller than that of NaCl or NaBr. The gold dissolution ability has been examined also for nitrous acid containing chloride and bromide ions at 35 °C. The NaNO2 solution containing twice or more amounts of HX (X = Cl, Br) gives the maximum efficiency for gold dissolution, according to the log(k/s(-1)) values of the mixed solutions of NaNO2 (0.10-2.0 mol L(-1)) and HX of various concentrations. The influence of oxidation by dilute nitric and nitrous acids on the gold dissolution is discussed from the standpoint of the redox potentials in "modified" aqueous solutions and not of the changes in the activity coefficients of ions.

  7. High-throughput ab-initio dilute solute diffusion database

    PubMed Central

    Wu, Henry; Mayeshiba, Tam; Morgan, Dane

    2016-01-01

    We demonstrate automated generation of diffusion databases from high-throughput density functional theory (DFT) calculations. A total of more than 230 dilute solute diffusion systems in Mg, Al, Cu, Ni, Pd, and Pt host lattices have been determined using multi-frequency diffusion models. We apply a correction method for solute diffusion in alloys using experimental and simulated values of host self-diffusivity. We find good agreement with experimental solute diffusion data, obtaining a weighted activation barrier RMS error of 0.176 eV when excluding magnetic solutes in non-magnetic alloys. The compiled database is the largest collection of consistently calculated ab-initio solute diffusion data in the world. PMID:27434308

  8. High-throughput ab-initio dilute solute diffusion database

    NASA Astrophysics Data System (ADS)

    Wu, Henry; Mayeshiba, Tam; Morgan, Dane

    2016-07-01

    We demonstrate automated generation of diffusion databases from high-throughput density functional theory (DFT) calculations. A total of more than 230 dilute solute diffusion systems in Mg, Al, Cu, Ni, Pd, and Pt host lattices have been determined using multi-frequency diffusion models. We apply a correction method for solute diffusion in alloys using experimental and simulated values of host self-diffusivity. We find good agreement with experimental solute diffusion data, obtaining a weighted activation barrier RMS error of 0.176 eV when excluding magnetic solutes in non-magnetic alloys. The compiled database is the largest collection of consistently calculated ab-initio solute diffusion data in the world.

  9. Chondroitin Sulfate in Solution: Effects of Mono- and Divalent Salts

    PubMed Central

    Horkay, Ferenc; Basser, Peter J.; Hecht, Anne-Marie; Geissler, Erik

    2013-01-01

    Chondroitin sulphate (CS) is a linear sulfated polysaccharide found in cartilage and other tissues in the body. Small angle neutron scattering (SANS) and dynamic light scattering (DLS) measurements are made on semi-dilute CS solutions to determine ion induced changes in the local order of the CS chains and in their dynamic properties. In salt-free CS solutions SANS detects the correlation peak due to local ordering between adjacent chains in which the characteristic interchain distance is d ≈ 57 Å. In both monovalent and divalent salts (NaCl and CaCl2) aligned linear regions are distinguishable corresponding to distance scales ranging from the length of the monomer unit (8 Å) to about 1000 Å. With increasing calcium ion concentration, the scattering intensity increases. Even in the presence of 200 mM CaCl2, however, neither phase separation nor cross-linking occurs. DLS in the CS solutions reveals two characteristic relaxation modes, the fast mode corresponding to the thermal concentration fluctuations. The collective diffusion coefficient D decreases with increasing calcium ion concentration and exhibits a power law function of the single variable c/J, where c is the CS concentration and J is the ionic strength of the salt in the solution. This result implies that the effect of the sodium and calcium ions on the dynamic properties of CS solutions is fully accounted for by the ionic strength. PMID:23814316

  10. Stability of dilute solutions of uranium, lead, and thorium ions

    USGS Publications Warehouse

    Milkey, R.G.

    1954-01-01

    Standard solutions and samples containing a few micrograms of metallic ions per milliliter are frequently used in determination of trace elements. It is important to know whether the concentrations of such solutions remain constant from day to day. The stability of dilute solutions of three metallic ions-uranium, lead, and thorium-has been investigated. Solutions containing concentrations of metallic ions, ranging from 1000 to 0.1 ?? per milliliter, were allowed to stand for approximately 2.5 months, and then the metallic ion content of those solutions that had lost strength was determined. Both adsorption and hydrolysis variously influenced the solute loss, but the minimum pH at which loss of concentration of lead and uranium occurred seemed to coincide with the pH at which the hydrolyzed metal ions began to precipitate. No increase in the stability of the solutions was obtained by substituting polyethylene containers for borosilicate glass. The solutions that lost strength could not be restored promptly to the original concentration by manual means, such as shaking them vigorously for several minutes.

  11. Preparation of sugar-salt solutions.

    PubMed

    de Zoysa, I; Kirkwood, B; Feachem, R; Lindsay-Smith, E

    1984-01-01

    Correct measurement techniques are essential for the preparation of oral rehydration solutions but dangerous or ineffective solutions may also result from the inherent variability of the method and ingredients. This paper describes an experimental study conducted in Zimbabwe to compare the reliability of three methods for measuring sugar and salt in a 750 ml bottle of water: (i) 6 level teaspoons of sugar and half a level teaspoon of salt, (ii) 3 heaped teaspoons of sugar and half a level teaspoon of salt and (iii) 3 level measures of sugar and salt with a double-ended spoon. The teaspoon and 750 ml bottle methods produced reliable results. Heaped teaspoons of sugar gave more reproducible sucrose concentrations than level teaspoons . The double-ended spoon was not more reliable and gave disquietingly high sodium concentrations with refined salt. Under field conditions the level teaspoon method gave more variable results but still within acceptable limits. It is concluded that a domestic teaspoon and a standard 750 ml bottle can be recommended for the preparation of home-based oral rehydration solutions in rural Zimbabwe.

  12. Improving accuracy and reproducibility of vibrational spectra for diluted solutions.

    PubMed

    Kojić, Dušan; Tsenkova, Roumiana; Yasui, Masato

    2017-02-22

    In what appears to be a trivial operation in which the averaged spectrum of solvent is subtracted from the spectra of solutions, can be a misleading step in improving reproducibility of vibrational spectra. Near-infrared spectra of pure water and glycine solutions were used to quantify instrumental and spectral variations, and examine its influence on the reproducibility of difference spectra over a wide concentration range. Significant improvements were observed (fourfold), in comparison with the most commonly applied technique that uses an averaged spectrum of solvent. We propose a new technique, in which subtraction of the closest spectrum of solvent involves calculating the smallest area under the subtracted curve, to extract the optimal outcome. These results reveal that, contrary to common practice, reproducibility for spectra of diluted solutions can bypass even instrumental baseline shifts and render results that are limited only by the noise originating from the instrument's sensor. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. Monte Carlo Simulation of Aqueous Dilute Solutions of Polyhydric Alcohols

    NASA Astrophysics Data System (ADS)

    Lilly, Arnys Clifton, Jr.

    In order to investigate the details of hydrogen bonding and solution molecular conformation of complex alcohols in water, isobaric-isothermal Monte Carlo simulations were carried out on several systems. The solutes investigated were ethanol, ethylene glycol, 1,2-propylene glycol, 1,3 -propylene glycol and glycerol. In addition, propane, which does not hydrogen bond but does form water hydrates, was simulated in aqueous solution. The complex alcohol-water systems are very nonideal in their behavior as a function of solute concentration down to very dilute solutions. The water model employed was TIP4P water^1 and the intermolecular potentials employed are of the Jorgensen type^2 in which the interactions between the molecules are represented by interaction sites usually located on nuclei. The interactions are represented by a sum of Coulomb and Lennard-Jones terms between all intermolecular pairs of sites. Intramolecular rotations in the solute are modeled by torsional potential energy functions taken from ethanol, 1-propanol and 2-propanol for C-O and C-C bond rotations. Quasi-component pair correlation functions were used to analyze the hydrogen bonding. Hydrogen bonds were classified as proton acceptor and proton donor bonds by analyzing the nearest neighbor pair correlation function between hydroxyl oxygen and hydrogen and between solvent-water hydrogen and oxygen. The results obtained for partial molar heats of solution are more negative than experimental values by 3.0 to 14 kcal/mol. In solution, all solutes reached a contracted molecular geometry with the OH groups generally on one side of the molecule. There is a tendency for the solute OH groups to hydrogen bond with water, with more proton acceptor bonds than proton donor bonds. The water -solute binding energies correlate with experimental measurements of the water-binding properties of the solute. ftn ^1Jorgensen, W. L. et al, J. Chem. Phys., 79, 926 (1983). ^2Jorgensen, W. L., J. Phys Chem., 87, 5304

  14. Hormetic effects of extremely diluted solutions on gene expression.

    PubMed

    Dei, Andrea; Bernardini, Simonetta

    2015-04-01

    This paper summarizes the results of investigations showing how molecular biological tools, such as DNA-microarrays, can provide useful suggestions about the behaviour of human organisms treated with microamounts of drugs or homeopathic medicines. The results reviewed here suggest firstly that the action of drugs is not quenched by ultra-high dilution and proceeds through modulation of gene expressions. The efficacy of drug solutions seems to be maintained in ultra-highly diluted preparations, a fact which constitutes a challenge to the dogma of quantization of matter. The second and more important result is that the different gene expression profiles of cell systems treated with the same drugs at different dilutions suggest the existence of hormetic mechanisms. The gene expression profiles of cells treated with copper(II) sulfate, Gelsemium sempervirens and Apis mellifica, are characterized by the same common denominator of the concentration-dependent inversion of gene expression, which can justify at a molecular level the concept of simile adopted in homeopathy. The main conclusion we draw from these results is that these procedures provide new kinds of information and a tool for disclosing the mechanisms involved in hormetic effects. The application of these effects to modern medicine may allow researchers to conceive unprecedented therapeutic applications or to optimize the currently used ones in the framework of a low-dose pharmacology based on a reliable experimental platform. Copyright © 2015 The Faculty of Homeopathy. Published by Elsevier Ltd. All rights reserved.

  15. Room-Temperature Tensile Behavior of Oriented Tungsten Single Crystals with Rhenium in Dilute Solid Solution

    DTIC Science & Technology

    1966-01-01

    SINGLE CRYSTALS WITH RHENIUM IN DILUTE SOLID SOLUTION Sby M. Garfinkle Lewis Research Center Cleveland, Ohio 20060516196 NATIONAL AERONAUTICS AND...WITH RHENIUM IN DILUTE SOLID SOLUTION By M. Garfinkle Lewis Research Center Cleveland, Ohio NATIONAL AERONAUTICS AND SPACE ADMINISTRATION For sale by...ORIENTED TUNGSTEN SINGLE CRYSTALS WITH RHENIUM IN DILUTE SOLID SOLUTION * by M. Garfinkle Lewis Research Center SUMMARY Tungsten single crystals

  16. Salting-in and salting-out of water-soluble polymers in aqueous salt solutions.

    PubMed

    Sadeghi, Rahmat; Jahani, Farahnaz

    2012-05-03

    To obtain further experimental evidence for the mechanisms of the salting effect produced by the addition of salting-out or sating-in inducing electrolytes to aqueous solutions of water-soluble polymers, systematic studies on the vapor-liquid equilibria and liquid-liquid equilibria of aqueous solutions of several polymers are performed in the presence of a large series of electrolytes. Polymers are polyethylene glycol 400 (PEG400), polyethylene glycol dimethyl ether 250 (PEGDME250), polyethylene glycol dimethyl ether 2000 (PEGDME2000), and polypropylene glycol 400 (PPG400), and the investigated electrolytes are KCl, NH(4)Cl, MgCl(2), (CH(3))(4)NCl, NaCl, NaNO(3), Na(2)CO(3), Na(2)SO(4), and Na(3)Cit (tri-sodium citrate). Aqueous solutions of PPG400 form aqueous two-phase systems with all the investigated salts; however, other investigated polymers form aqueous two-phase systems only with Na(2)CO(3), Na(2)SO(4), and Na(3)Cit. A relation was found between the salting-out or sating-in effects of electrolyte on the polymer aqueous solutions and the slopes of the constant water activity lines of ternary polymer-salt aqueous solutions, so that, in the case of the salting-out effect, the constant water activity lines had a concave slope, but in the case of the salting-in effects, the constant water activity lines had a convex slope. The effect of temperature, anion of electrolyte, cation of electrolyte, and type and molar mass of polymers were studied and the results interpreted in terms of the solute-water and solute-solute interactions. The salting-out effect results from the formation of ion (specially anion)-water hydration complexes, which, in turn, decreases hydration, and hence, the solubility of the polymer and the salting-in effect results from a direct binding of the cations to the ether oxygens of the polymers.

  17. Degradation of Sodium-Polyacrylate in Dilute Aqueous Solution

    NASA Astrophysics Data System (ADS)

    Saita, Takao

    1980-12-01

    It is shown using a capillary viscometer that the viscosity of a dilute aqueous solution of sodium-polyacrylate at 20°C decreases gradually for each flow time measurement and also decreases with the time of rest. Assuming that the polymer degradation is caused by shearing stress and oxidation, their effects are discussed with the data obtained using a closed-type capillary viscometer derived for this investigation. It is proved from the results that rupture of the Na-PAA molecule is caused by mechanochemical degradation, and also photo-degradation under the usual illumination and sunlight in a laboratory.

  18. Oscillations in a Linearly Stratified Salt Solution

    ERIC Educational Resources Information Center

    Heavers, Richard M.

    2007-01-01

    Our physics students like to watch a ball bouncing underwater. They do this by dropping a weighted plastic ball into a 1000-ml cylinder filled with a linearly stratified salt-water solution at room temperature. The ball oscillates and comes to rest at about mid-depth. Its motion is analogous to the damped vertical oscillations of a mass hanging…

  19. Oscillations in a Linearly Stratified Salt Solution

    ERIC Educational Resources Information Center

    Heavers, Richard M.

    2007-01-01

    Our physics students like to watch a ball bouncing underwater. They do this by dropping a weighted plastic ball into a 1000-ml cylinder filled with a linearly stratified salt-water solution at room temperature. The ball oscillates and comes to rest at about mid-depth. Its motion is analogous to the damped vertical oscillations of a mass hanging…

  20. Geophysical methods to support correct water sampling locations for salt dilution gauging

    NASA Astrophysics Data System (ADS)

    Comina, C.; Lasagna, M.; De Luca, D. A.; Sambuelli, L.

    2014-08-01

    To improve water management design, particularly in irrigation areas, it is important to evaluate the baseline state of the water resources, including canal discharge. Salt dilution gauging is a traditional and well-documented technique in this respect. The complete mixing of salt used for dilution gauging is required; this condition is difficult to test or verify and, if not fulfilled, is the largest source of uncertainty in the discharge calculation. In this paper, a geophysical technique (FERT, fast electrical resistivity tomography) is proposed for imaging the distribution of the salt plume used for dilution gauging at every point along a sampling cross section. With this imaging, complete mixing can be verified. If the mixing is not complete, the image created by FERT can also provide a possible guidance for selecting water-sampling locations in the sampling cross section. A water multi-sampling system prototype aimed to potentially take into account concentration variability is also proposed and tested. The results reported in the paper show that FERT provides a three-dimensional image of the dissolved salt plume and that this can potentially help in the selection of water sampling points.

  1. Molecular dynamics of a dilute solution of hydrogen in palladium

    NASA Astrophysics Data System (ADS)

    Pratt, Lawrence R.; Eckert, J.

    1989-06-01

    Molecular-dynamics results on a dilute solution of H in Pd are presented and compared with available incoherent inelastic neutron-scattering results. The embedded-atom model adopted here does a good job of describing the H-Pd atomic forces probed by incoherent inelastic neutron scattering. The time correlation functions associated with the computed spectra are strongly damped and indicative of the anharmonicity that has been suggested as the principal contribution to the anomalous isotope dependence of the superconducting transition temperature in PdH. These results highlight the fact that the H-atom vibrations in Pd-H solutions are low-frequency, large-amplitude vibrations relative to vibrations of H atoms in usual covalent interactions. The rms displacement of the H atom from its mean position in the center of the Pd octahedron compares favorably with the available neutron-diffraction results.

  2. Degradation of Sodium-Polyacrylate in Dilute Aqueous Solution, II

    NASA Astrophysics Data System (ADS)

    Saita, Takao; Matumura, On

    1983-08-01

    It has been found that Na-PAA molecules in dilute aqueous solution are degraded by shearing stress, oxidation and photolysis during usual viscosity measurements with a capillary viscometer. The results of previous viscosity measurements, mainly about the mechanochemical degradation in air and in air-free conditions, showed that the degradation rate increases with increasing shear stress, and with decreasing polymer concentration. In this work, the effects of the molecular weight and temperature on the degradation rate are measured using a capillary viscometer in air, and the photodegradation of Na-PAA and PAA in aqueous solution irradiated with UV light are studied by viscosity measurements in air, and by UV absorption and ESR methods. The results show that the degradation of molecules is enhanced by an increase in the molecular weight and strongly accelerated by a rise in temperature and by UV irradiation, and is accompanied by free-radical chain reactions.

  3. Reactions of gaseous, elemental mercury with dilute halogen solutions

    SciTech Connect

    Mendelsohn, M.H.; Livengood, C.D.

    1996-07-01

    Of the trace elements known to exist in fossil fuels, mercury (Hg) has emerged as one of the greatest concerns. Mercury has been found to be emitted from combustion in at least two different chemical forms: elemental Hg and oxidized Hg compounds. Precise identification of the oxidized compounds emitted has not been accomplished to date. However, most workers in this field assume that mercuric chloride should be the predominant oxidized species. Mercuric chloride should be readily removed in a wet scrubber system because of its relatively high solubility in water. However, it has been presumed, and we have shown, that elemental Hg will pass through a wet scrubber system with little or no removal being effected. Therefore, it is important, in order to obtain a high total Hg removal, to study methods that might result in a removal of gaseous, elemental Hg from a flue-gas stream. In this regard, we have been studying the effect of dilute halogen-containing solutions on elemental Hg in gas streams of various compositions. In particular, the results of passing Hg through bubblers containing solutions of iodine, chlorine, and chloric acid are described. Mercury found in the bubbler solutions is an indication of the extent of reaction (oxidation) of elemental Hg with the halogen species, since we have found very little Hg transferred to the liquid phase when only distilled water is used in the bubblers. Results using commercial iodine, sodium hypochlorite, and NOXSORB (sup TM) solutions are presented and discussed.

  4. The study on pervaporation behaviors of dilute organic solution through PDMS/PTFE composite membrane.

    PubMed

    Zhang, Wei-dong; Sun, Wei; Yang, Jing; Ren, Zhong-qi

    2010-01-01

    As an energy-efficient alternative to distillation, pervaporation has been widely combined with fermentation to remove organic compounds from their dilute solutions in a fermentation broth. In this work, the organic permselective composite membrane is prepared by coating polydimethylsiloxane (PDMS) cross-linked with n-heptane on the substrate of polytetrafluoroethylene(PTFE) membrane. The separation behavior is studied in different dilute organic solutions, which include acetone dilute solution, butanone dilute solution, cyclohexanone dilute solution, ethanol dilute solution, isopropanol dilute solution, n-butyl alcohol dilute solution, acetic acid dilute solution, and ethyl acetate dilute solution. Most of these solutions are main reaction products or by-products from fermentation process. The effects of solubility of organics in the membrane, molecular weight, and polarity of the organics on the pervaporation performance are investigated. The effects of operating temperature and organic concentration in the feed solutions on the performance of composite membrane are studied as well. The experimental results show that molecular volume has less influence than solubility and molecular polarity for these organic solvent. The selectivity of PDMS membrane to ethyl acetate is relative high due to good solubility and diffusion of ethyl acetate molecules in polymer.

  5. THE ROLE OF ELECTRON CONFIGURATION ON PROPERTIES IN DILUTE SOLID SOLUTION ALLOYS

    DTIC Science & Technology

    THE ROLE OF ELECTRON CONFIGURATION ON THE PROPERTIES OF DILUTE SOLID SOLUTION ALLOYS IS DISCUSSED IN TERMS OF THE EFFECT OF DILUTE IMPURITIES ON THE RECRYSTALLIZATION CHARACTERISTICS OF PURE METALLIC ELEMENTS.

  6. Reaction of trace mercury in natural gas with dilute polysulfide solutions in a packed column

    SciTech Connect

    Not Available

    1991-12-01

    This paper reports that the natural gas produced around the world can contain traces of mercury which have to be removed. It is difficult to purify gas to desired mercury levels using conventional techniques. By scrubbing with dilute polysulfide solution, the residual mercury in the gas can be removed from about 0.1 to below 0.01 ppb, a reduction of 90%. In this system, the gas is passed through a packed tower wetted with a solution containing 3 ppm of polysulfide salt. Stainless steel packings are effective for this application. In addition to promoting gas-liquid contact, the stainless steel packings adsorb and concentrate polysulfides which react with Hg in the gas to form insoluble HgS, and thus remove Hg from the gas.

  7. Ionizing radiation induced degradation of monuron in dilute aqueous solution

    NASA Astrophysics Data System (ADS)

    Kovács, Krisztina; He, Shijun; Míle, Viktória; Földes, Tamás; Pápai, Imre; Takács, Erzsébet; Wojnárovits, László

    2016-07-01

    The decomposition of monuron was investigated in dilute aqueous solutions using pulse radiolysis and γ-radiolysis in order to identify the intermediates and final products. The main reaction takes place between monuron and the hydroxyl radicals yielding hydroxycyclohexadienyl type radicals with a second order rate constant of (7.4±0.2)×109 mol-1 dm3 s-1. In •OH reactions, the aminyl and phenoxyl radicals may also form. Dechlorination was observed in both hydroxyl radical and hydrated electron reactions. The •OH induced dechlorination reactions are suggested to occur through OH substitution or phenoxyl radical formation. The rate of oxidation is very high in the presence of dissolved oxygen. Some of the results are also supported by quantum chemical calculations.

  8. Long-lived submicrometric bubbles in very diluted alkali halide water solutions.

    PubMed

    Duval, Eugène; Adichtchev, Sergey; Sirotkin, Sergey; Mermet, Alain

    2012-03-28

    Solutions of LiCl and of NaCl in ultrapure water were studied through Rayleigh/Brillouin scattering as a function of the concentration (molarity, M) of dissolved salt from 0.2 M to extremely low concentration (2 × 10(-17) M). The Landau-Placzek ratio, R/B, of the Rayleigh scattering intensity over the total Brillouin was measured thanks to the dynamically controlled stability of the used Fabry-Perot interferometer. It was observed that the R/B ratio follows two stages as a function of increasing dilution rate: after a strong decrease between 0.2 M and 2 × 10(-5) M, it increases to reach a maximum between 10(-9) M and 10(-16) M. The first stage corresponds to the decrease of the Rayleigh scattering by the ion concentration fluctuations with the decrease of salt concentration. The second stage, at lower concentrations, is consistent with the increase of the Rayleigh scattering by long-lived sub-microscopic bubbles with the decrease of ion concentration. The origin of these sub-microscopic bubbles is the shaking of the solutions, which was carried out after each centesimal dilution. The very long lifetime of the sub-microscopic bubbles and the effects of aging originate in the electric charge of bubbles. The increase of R/B with the decrease of the low salt concentration corresponds to the increase of the sub-microscopic bubble size with the decrease of concentration, which is imposed by the bubble stability due to the covering of the surface bubble by negative ions.

  9. Method for preparing salt solutions having desired properties

    DOEpatents

    Ally, Moonis R.; Braunstein, Jerry

    1994-01-01

    The specification discloses a method for preparing salt solutions which exhibit desired thermodynamic properties. The method enables prediction of the value of the thermodynamic properties for single and multiple salt solutions over a wide range of conditions from activity data and constants which are independent of concentration and temperature. A particular application of the invention is in the control of salt solutions in a process to provide a salt solution which exhibits the desired properties.

  10. Chlorate salts and solutions on Mars

    NASA Astrophysics Data System (ADS)

    Hanley, Jennifer; Chevrier, Vincent F.; Berget, Deanna J.; Adams, Robert D.

    2012-04-01

    Chlorate (ClO3-) is an intermediate oxidation species between chloride (Cl-) and perchlorate (ClO4-), both of which were found at the landing site by the Wet Chemistry Lab (WCL). The chlorate ion is almost as stable as perchlorate, and appears to be associated with perchlorate in most terrestrial reservoirs (e.g. Atacama and Antarctica). It is possible that chlorate contributed to the ion sensor response on the WCL, yet was masked by the strong perchlorate signal. However, very little is known about chlorate salts and their effect on the stability of water. We performed evaporation rate experiments in our Mars simulation chamber, which enabled us to determine the activity of water for various concentrations. From this we constructed solubility diagrams for NaClO3, KClO3, Mg(ClO3)2 and Ca(ClO3)2, and determined the Pitzer parameters for each salt. Chlorate salt eutectic temperatures range from 270 K (KClO3) to 204 K (Mg(ClO3)2). Modeling the addition of chlorate to the initial WCL solutions shows that it precipitates in concentrations comparable to other common salts, such as gypsum and epsomite, and implies that chlorates may play an important role in the wet chemistry on Mars.

  11. Dilute-solution Structure of Charged Arborescent Graft Polymer

    SciTech Connect

    Yun, Seok; Briber, R M; Kee, R. Andrew; Gauthier, Mario

    2006-01-01

    The solutions of charged G1 arborescent polystyrene-graft-poly(2-vinylpyridine) copolymers in methanol-d4 and D{sub 2}O were investigated over a dilute concentration range {phi} = 0.005-0.05 ({phi}: mass fraction) using small-angle neutron scattering (SANS). Upon addition of acid (HCl) arborescent graft polymers became charged and a peak appeared in SANS data. The interparticle distance (d{sub exp}) calculated from a peak position corresponded to the expected value (d{sub uni}) for a uniform particle distribution. This indicates the formation of liquid-like ordering due to long-range Coulombic repulsions. The smaller dielectric constant of methanol-d4 resulted in long-range electrostatic repulsions persisting to lower polymer concentration than in D{sub 2}O. The slow mode scattering was observed by dynamic light scattering measurements for the same polymer solutions, indicating the presence of structural inhomogeneity in the solutions. Both the peak and slow mode disappeared by addition of NaCl or excess HCl into the solutions due to the screening of electrostatic interactions. The G1 polymer grafted with longer P2VP chains (M{sub w} {approx} 30,000 versus 5000 g mol) formed a gel on addition of HCl. This result reveals that molecular expansion is more significant for arborescent polymers with longer (M{sub w} {approx} 30,000) linear polyelectrolyte branches, resulting in gelation for {phi} > 0.01. Upon addition of NaCl or excess HCl a gel transformed back to a liquid resulted from the screening of electrostatic interactions.

  12. Conductivity and electrophoretic mobility of dilute ionic solutions.

    PubMed

    Allison, Stuart; Wu, Hengfu; Twahir, Umar; Pei, Hongxia

    2010-12-01

    Two complementary continuum theories of electrokinetic transport are examined with particular emphasis on the equivalent conductance of binary electrolytes. The "small ion" model [R.M. Fuoss, L. Onsager, J. Phys. Chem. 61 (1957) 668] and "large ion" model [R.W. O'Brien, L.R. White, J. Chem. Soc. Faraday Trans. 2 (74) (1978) 1607] are both discussed and the "large ion" model is generalized to include an ion exclusion distance and to account in a simple but approximate way for the Brownian motion of all ions present. In addition, the "large ion" model is modified to treat "slip" hydrodynamic boundary conditions in addition to the standard "stick" boundary condition. Both models are applied to the equivalent conductance of dilute KCl, MgCl(2), and LaCl(3) solutions and both are able to reproduce experimental conductances to within an accuracy of several tenths of a percent. Despite fundamental differences in the "small ion" and "large ion" theories, they both work equally well in this application. In addition, both "stick-large ion" and "slip-large ion" models are equally capable of accounting for the equivalent conductances of the three electrolyte solutions.

  13. UV photolysis of perfluorooctanoic acid (PFOA) in dilute aqueous solution.

    PubMed

    Giri, R R; Ozaki, H; Morigaki, T; Taniguchi, S; Takanami, R

    2011-01-01

    Perfluorooctanoic acid (PFOA) is very persistent in the environment and widely detected in the water environment. Only some advanced methods with extreme reaction conditions are shown to be capable of degrading the compound efficiently, and almost all the earlier investigations used very high PFOA concentrations. The compound is detected normally at very low concentrations in the water environment, while mild reaction conditions for its degradation are preferable. This article aimed to elucidate photodegradation of PFOA in dilute aqueous solutions by combined UV wavelengths (185 nm+254 nm) and 254 nm using a newly designed UV jacket. PFOA degradation was greatly enhanced with the combined wavelengths with almost one hundred percent PFOA removals in four-hour reaction. The removals were well described by the first-order reaction kinetic. The removal efficiencies and rate values significantly decreased with smaller initial PFOA concentrations. But defluorination was greatly enhanced with smaller PFOA concentrations possibly due to accelerated decomposition of fluorinated intermediates of PFOA. Formic acid and acetic acid were two tentatively identified intermediates of PFOA photolysis while the former was a major intermediate predominantly controlling solution pH during the oxidation. The results demonstrated that PFOA photolysis by the combined wavelengths with mild reaction conditions can be greatly enhanced by proper design of UV jacket and reactor system.

  14. Nonequilibrium thermodynamics of dilute polymer solutions in flow

    SciTech Connect

    Latinwo, Folarin; Hsiao, Kai-Wen; Schroeder, Charles M.

    2014-11-07

    Modern materials processing applications and technologies often occur far from equilibrium. To this end, the processing of complex materials such as polymer melts and nanocomposites generally occurs under strong deformations and flows, conditions under which equilibrium thermodynamics does not apply. As a result, the ability to determine the nonequilibrium thermodynamic properties of polymeric materials from measurable quantities such as heat and work is a major challenge in the field. Here, we use work relations to show that nonequilibrium thermodynamic quantities such as free energy and entropy can be determined for dilute polymer solutions in flow. In this way, we determine the thermodynamic properties of DNA molecules in strong flows using a combination of simulations, kinetic theory, and single molecule experiments. We show that it is possible to calculate polymer relaxation timescales purely from polymer stretching dynamics in flow. We further observe a thermodynamic equivalence between nonequilibrium and equilibrium steady-states for polymeric systems. In this way, our results provide an improved understanding of the energetics of flowing polymer solutions.

  15. Nonequilibrium thermodynamics of dilute polymer solutions in flow.

    PubMed

    Latinwo, Folarin; Hsiao, Kai-Wen; Schroeder, Charles M

    2014-11-07

    Modern materials processing applications and technologies often occur far from equilibrium. To this end, the processing of complex materials such as polymer melts and nanocomposites generally occurs under strong deformations and flows, conditions under which equilibrium thermodynamics does not apply. As a result, the ability to determine the nonequilibrium thermodynamic properties of polymeric materials from measurable quantities such as heat and work is a major challenge in the field. Here, we use work relations to show that nonequilibrium thermodynamic quantities such as free energy and entropy can be determined for dilute polymer solutions in flow. In this way, we determine the thermodynamic properties of DNA molecules in strong flows using a combination of simulations, kinetic theory, and single molecule experiments. We show that it is possible to calculate polymer relaxation timescales purely from polymer stretching dynamics in flow. We further observe a thermodynamic equivalence between nonequilibrium and equilibrium steady-states for polymeric systems. In this way, our results provide an improved understanding of the energetics of flowing polymer solutions.

  16. Hydration patterns and salting effects in sodium chloride solution.

    PubMed

    Li, Weifeng; Mu, Yuguang

    2011-10-07

    The salting effects of 2M sodium chloride electrolyte are studied based on a series of model solutes with properties ranging from hydrophobic to hydrophilic. Generally, hydrophobic solutes will be salted out and hydrophilic solutes will be salted in by NaCl solution. The solvation free energy changes are highly correlated with Kirkwood-Buff integrals. The underlying mechanism resorts to the preferential binding of ions and water to solutes. Our results demonstrate that the salting effect not only depends on the salt's position in Hofmeister series, but also on the solutes' specifics. Taking the hydration free energies of solutes and ions as independent variables, a schematic diagram of salting effects is suggested. The resolved multifaceted salting effects rely on the sensitive balance of the tripartite interaction among solutes, ions, and water.

  17. Hydration patterns and salting effects in sodium chloride solution

    NASA Astrophysics Data System (ADS)

    Li, Weifeng; Mu, Yuguang

    2011-10-01

    The salting effects of 2M sodium chloride electrolyte are studied based on a series of model solutes with properties ranging from hydrophobic to hydrophilic. Generally, hydrophobic solutes will be salted out and hydrophilic solutes will be salted in by NaCl solution. The solvation free energy changes are highly correlated with Kirkwood-Buff integrals. The underlying mechanism resorts to the preferential binding of ions and water to solutes. Our results demonstrate that the salting effect not only depends on the salt's position in Hofmeister series, but also on the solutes' specifics. Taking the hydration free energies of solutes and ions as independent variables, a schematic diagram of salting effects is suggested. The resolved multifaceted salting effects rely on the sensitive balance of the tripartite interaction among solutes, ions, and water.

  18. Organic ionic salt draw solutions for osmotic membrane bioreactors.

    PubMed

    Bowden, Katie S; Achilli, Andrea; Childress, Amy E

    2012-10-01

    This investigation evaluates the use of organic ionic salt solutions as draw solutions for specific use in osmotic membrane bioreactors. Also, this investigation presents a simple method for determining the diffusion coefficient of ionic salt solutions using only a characterized membrane. A selection of organic ionic draw solutions underwent a desktop screening process before being tested in the laboratory and evaluated for performance using specific salt flux (reverse salt flux per unit water flux), biodegradation potential, and replenishment cost. Two of the salts were found to have specific salt fluxes three to six times lower than two commonly used inorganic draw solutions, NaCl and MgCl(2). All of the salts tested have organic anions with the potential to degrade in the bioreactor as a carbon source and aid in nutrient removal. Results demonstrate the potential benefits of organic ionic salt draw solutions over currently implemented inorganics in osmotic membrane bioreactor systems. Copyright © 2012 Elsevier Ltd. All rights reserved.

  19. Chitosan sorbents for platinum sorption from dilute solutions

    SciTech Connect

    Guibal, E.; Larkin, A.; Vincent, T.; Tobin, J.M.

    1999-10-01

    Chitosan has proved efficient at removing platinum in dilute effluents. The maximum uptake capacity reaches 300 mg/g (almost 1.5 mmol/g). The optimum pH for sorption is pH 2. A glutaraldehyde cross-linking pretreatment is necessary to stabilize the biopolymer in acidic solutions. Sorption isotherms have been studied as a function of pH, sorbent particle size, and the cross-linking ratio. Surprisingly, the extent of the cross-linking (determined by the concentration of the cross-linking agent in the treatment bath) has no significant influence on uptake capacity. Competitor anions such as chloride or nitrate induce a large decrease in the sorption efficiency. Sorption kinetics show also that uptake rate is not significantly changed by increasing either the cross-linking ratio or the particle size of the sorbent. Mass transfer rates are significantly affected by the initial platinum concentration and by the conditioning of the biopolymer. Gel-bead conditioning appears to reduce the sorption rate. While for molybdate and vanadate ions, mass transfer was governed by intraparticle mass transfer, for platinum, both external and intraparticle diffusion control the uptake rate. In contrast with the former ions, platinum does not form polynuclear hydrolyzed species, which are responsible for steric hindrance of diffusion into the polymer network.

  20. Structure Formation in Semi-Dilute Polymer Solution during Electrospinning

    NASA Astrophysics Data System (ADS)

    Zussman, Eyal; Paley, Yakov; Arinstein, Arkadii; Shuster, Kim

    2012-02-01

    In our recent work it was shown that longitudinal stretching of electrospun highly entangled semi-dilute polymer solution caused by jet hydrodynamic forces, transforms the topological network to an almost fully-stretched state within less than 1 mm from the jet start (PRE, 2011). Further evolution of the polymer network is related to a disentanglement of polymer chains and transformation of the topological network structure. As was sown by Malkin et al., (Rheol. Acta, 2011) high deformation rate of a topological polymer network, results in reptations of macromolecules caused by uncompensated local forces, whereas Brownian motion effect is negligible. Based on this conclusion, we examine the disentanglement process, using a mechanical pulley-block system assembled from multiple pulleys suspended by elastic springs, and taut string connecting two blocks. Each pulley corresponds to a topological knot; the taut string corresponds to a reptated chain; the springs correspond to surrounded polymer chains; and the blocks correspond to local deformation force. It turned out that the system is sensitive to system parameters. The pulleys can approach each other and the string stops to move. Such a behavior corresponds to formation of bundle of knots of entangled chains. In other conditions, the string continuously moves while the pulleys did not approach each other which corresponds to disentanglement of polymer chains. These experiments clarify the disentanglement kinetics in rapid-deformed polymer system.

  1. SOLUTION MINING IN SALT DOMES OF THE GULF COAST EMBAYMENT

    SciTech Connect

    Griswold, G. B.

    1981-02-01

    Following a description of salt resources in the salt domes of the gulf coast embayment, mining, particularly solution mining, is described. A scenario is constructed which could lead to release of radioactive waste stored in a salt dome via inadvertent solution mining and the consequences of this scenario are analyzed.

  2. Coalescence of silver clusters by immersion in diluted HF solution

    SciTech Connect

    Milazzo, R. G.; Mio, A. M.; D’Arrigo, G.; Spinella, C.; Grimaldi, M. G.; Rimini, E.

    2015-07-14

    The galvanic displacement deposition of silver on H-terminated Si (100) in the time scale of seconds is instantaneous and characterized by a cluster density of 10{sup 11}-10{sup 12} cm{sup −2}. The amount of deposited Ag follows a t{sup 1/2} dependence in agreement with a Cottrell diffusion limited mechanism. At the same time, during the deposition, the cluster density reduces by a factor 5. This behavior is in contrast with the assumption of immobile clusters. We show in the present work that coalescence and aggregation occur also in the samples immersed in the diluted hydrofluoric acid (HF) solution without the presence of Ag{sup +}. Clusters agglomerate according to a process of dynamic coalescence, typical of colloids, followed by atomic redistribution at the contact regions with the generation of multiple internal twins and stacking-faults. The normalized size distributions in terms of r/r{sub mean} follow also the prediction of the Smoluchowski ripening mechanism. No variation of the cluster density occurs for samples immersed in pure H{sub 2}O solution. The different behavior might be associated to the strong attraction of clusters to oxide-terminated Si surface in presence of water. The silver clusters are instead weakly bound to hydrophobic H-terminated Si in presence of HF. HF causes then the detachment of clusters and a random movement on the silicon surface with mobility of about 10{sup −13} cm{sup 2}/s. Attractive interaction (probably van der Waals) among particles promotes coarsening.

  3. Solubility of pllutonium in alkaline salt solutions

    SciTech Connect

    Hobbs, D.T.; Edwards, T.B.

    1993-02-26

    Plutonium solubility data from several studies have been evaluated. For each data set, a predictive model has been developed where appropriate. In addition, a statistical model and corresponding prediction intervals for plutonium solubility as a quadratic function of the hydroxide concentration have been developed. Because of the wide range of solution compositions, the solubility of plutonium can vary by as much as three orders of magnitude for any given hydroxide concentration and still remain within the prediction interval. Any nuclear safety assessments that depend on the maximum amount of plutonium dissolved in alkaline salt solutions should use concentrations at least as great as the upper prediction limits developed in this study. To increase the confidence in the prediction model, it is recommended that additional solubility tests be conducted at low hydroxide concentrations and with all of the other solution components involved. To validate the model for application to actual waste solutions, it is recommended that the plutonium solubilities in actual waste solutions be determined and compared to the values predicted by the quadratic model.

  4. Dilution

    PubMed Central

    Lavie, Nilli; Torralbo, Ana

    2010-01-01

    Load theory of attention proposes that distractor processing is reduced in tasks with high perceptual load that exhaust attentional capacity within task-relevant processing. In contrast, tasks of low perceptual load leave spare capacity that spills over, resulting in the perception of task-irrelevant, potentially distracting stimuli. Tsal and Benoni (2010) find that distractor response competition effects can be reduced under conditions with a high search set size but low perceptual load (due to a singleton color target). They claim that the usual effect of search set size on distractor processing is not due to attentional load but instead attribute this to lower level visual interference. Here, we propose an account for their findings within load theory. We argue that in tasks of low perceptual load but high set size, an irrelevant distractor competes with the search nontargets for remaining capacity. Thus, distractor processing is reduced under conditions in which the search nontargets receive the spillover of capacity instead of the irrelevant distractor. We report a new experiment testing this prediction. Our new results demonstrate that, when peripheral distractor processing is reduced, it is the search nontargets nearest to the target that are perceived instead. Our findings provide new evidence for the spare capacity spillover hypothesis made by load theory and rule out accounts in terms of lower level visual interference (or mere “dilution”) for cases of reduced distractor processing under low load in displays of high set size. We also discuss additional evidence that discounts the viability of Tsal and Benoni's dilution account as an alternative to perceptual load. PMID:21133554

  5. Selective monovalent cation association and exchange around Keplerate polyoxometalate macroanions in dilute aqueous solutions.

    PubMed

    Pigga, Joseph M; Teprovich, Joseph A; Flowers, Robert A; Antonio, Mark R; Liu, Tianbo

    2010-06-15

    The interaction between water-soluble Keplerate polyoxometalate {Mo(72)Fe(30)} macroions and small countercations is explored by laser light scattering, anomalous small-angle X-ray scattering (ASAXS), and isothermal titration calorimetry (ITC) techniques. The macroions are found to be able to select the type of associated counterions based upon the counterions' valence state and hydrated size, when multiple types of additional cations are present in solution (even among different monovalent cations). The preference goes to the cations with higher valences or smaller hydrated sizes if the valences are identical. This counterion exchange process changes the magnitude of the macroion-counterion interaction and, thus, is reflected in the dimension of the self-assembled {Mo(72)Fe(30)} blackberry supramolecular structures. The hydrophilic macroions exhibit a competitive recognition of various monovalent counterions in dilute solutions. A critical salt concentration (CSC) for each type of cation exists for the blackberry formation of {Mo(72)Fe(30)} macroions, above which the blackberry size increases significantly with the increasing total ionic strength in solution. The CSC values are much smaller for cations with higher valences and also decrease with the cations' hydrated size for various monovalent cations. The change of blackberry size corresponding to the change of ionic strength in solution is reversible.

  6. Separation processes using expulsion from dilute supercritical solutions

    DOEpatents

    Cochran, H.D. Jr.

    1993-04-20

    A process is described for separating isotopes as well as other mixtures by utilizing the behavior of dilute repulsive or weakly attractive elements of the mixtures as the critical point of the solvent is approached.

  7. Separation processes using expulsion from dilute supercritical solutions

    DOEpatents

    Cochran, Jr., Henry D.

    1993-01-01

    A process for separating isotopes as well as other mixtures by utilizing the behavior of dilute repulsive or weakly attractive elements of the mixtures as the critical point of the solvent is approached.

  8. Opalescence in monoclonal antibody solutions and its correlation with intermolecular interactions in dilute and concentrated solutions.

    PubMed

    Raut, Ashlesha S; Kalonia, Devendra S

    2015-04-01

    Opalescence indicates physical instability of a formulation because of the presence of aggregates or liquid-liquid phase separation in solution and has been reported for monoclonal antibody (mAb) formulations. Increased solution opalescence can be attributed to attractive protein-protein interactions (PPIs). Techniques including light scattering, AUC, or membrane osmometry are routinely employed to measure PPIs in dilute solutions, whereas opalescence is seen at relatively higher concentrations, where both long- and short-range forces contribute to overall PPIs. The mAb molecule studied here shows a unique property of high opalescence because of liquid-liquid phase separation. In this study, opalescence measurements are correlated to PPIs measured in diluted and concentrated solutions using light scattering (kD ) and high-frequency rheology (G'), respectively. Charges on the molecules were calculated using zeta potential measurements. Results indicate that high opalescence and phase separation are a result of the attractive interactions in solution; however, the presence of attractive interactions do not always imply phase separation. Temperature dependence of opalescence suggests that thermodynamic contribution to opalescence is significant and Tcloud can be utilized as a potential tool to assess attractive interactions in solution.

  9. Collapse of sodium polyacrylate chains in calcium salt solutions

    NASA Astrophysics Data System (ADS)

    Schweins, R.; Huber, K.

    The sodium salt of polyacrylic acid (NaPA) precipitates in the presence of Ca^{2+}-ions. This phase behaviour can be represented by a phase diagram where the critical NaPA concentration is plotted versus the critical Ca^{2+} concentration resulting in a straight line as a phase boundary. The location of this phase boundary is influenced by the presence of an inert monovalent salt like NaCl. The present contribution focuses on the coil dimensions of NaPA chains in dilute aqueous solution corresponding to the one phase region of such a phase diagram. A variety of parameters with which the size and shape of the polyelectrolyte chains can be modulated are revealed. Approaching the phase boundary by decreasing the NaPA concentration at a constant Ca^{2+} content leads to a collapse of the NaPA chains. Combined static and dynamic light scattering suggests a compact spherical shape as the final state of this transition, both in 0.1 M NaCl and in 0.01 M NaCl. In the lower NaCl concentration, indication is presented for the existence of a cigar or pearl necklace like intermediate. Most strikingly, the collapsed chains can be reexpanded by increasing the concentration of inert NaCl at constant content of NaPA and Ca^{2+}. Clearly, excessive Na+-ions displace the Ca^{2+}-ions from the NaPA chains.

  10. Adaptive resolution simulation of salt solutions

    NASA Astrophysics Data System (ADS)

    Bevc, Staš; Junghans, Christoph; Kremer, Kurt; Praprotnik, Matej

    2013-10-01

    We present an adaptive resolution simulation of aqueous salt (NaCl) solutions at ambient conditions using the adaptive resolution scheme. Our multiscale approach concurrently couples the atomistic and coarse-grained models of the aqueous NaCl, where water molecules and ions change their resolution while moving from one resolution domain to the other. We employ standard extended simple point charge (SPC/E) and simple point charge (SPC) water models in combination with AMBER and GROMOS force fields for ion interactions in the atomistic domain. Electrostatics in our model are described by the generalized reaction field method. The effective interactions for water-water and water-ion interactions in the coarse-grained model are derived using structure-based coarse-graining approach while the Coulomb interactions between ions are appropriately screened. To ensure an even distribution of water molecules and ions across the simulation box we employ thermodynamic forces. We demonstrate that the equilibrium structural, e.g. radial distribution functions and density distributions of all the species, and dynamical properties are correctly reproduced by our adaptive resolution method. Our multiscale approach, which is general and can be used for any classical non-polarizable force-field and/or types of ions, will significantly speed up biomolecular simulation involving aqueous salt.

  11. Ion aggregation in high salt solutions. III. Computational vibrational spectroscopy of HDO in aqueous salt solutions

    SciTech Connect

    Choi, Jun-Ho; Lim, Sohee; Chon, Bonghwan; Cho, Minhaeng; Kim, Heejae; Kim, Seongheun

    2015-05-28

    The vibrational frequency, frequency fluctuation dynamics, and transition dipole moment of the O—D stretch mode of HDO molecule in aqueous solutions are strongly dependent on its local electrostatic environment and hydrogen-bond network structure. Therefore, the time-resolved vibrational spectroscopy the O—D stretch mode has been particularly used to investigate specific ion effects on water structure. Despite prolonged efforts to understand the interplay of O—D vibrational dynamics with local water hydrogen-bond network and ion aggregate structures in high salt solutions, still there exists a gap between theory and experiment due to a lack of quantitative model for accurately describing O—D stretch frequency in high salt solutions. To fill this gap, we have performed numerical simulations of Raman scattering and IR absorption spectra of the O—D stretch mode of HDO in highly concentrated NaCl and KSCN solutions and compared them with experimental results. Carrying out extensive quantum chemistry calculations on not only water clusters but also ion-water clusters, we first developed a distributed vibrational solvatochromic charge model for the O—D stretch mode in aqueous salt solutions. Furthermore, the non-Condon effect on the vibrational transition dipole moment of the O—D stretch mode was fully taken into consideration with the charge response kernel that is non-local polarizability density. From the fluctuating O—D stretch mode frequencies and transition dipole vectors obtained from the molecular dynamics simulations, the O—D stretch Raman scattering and IR absorption spectra of HDO in salt solutions could be calculated. The polarization effect on the transition dipole vector of the O—D stretch mode is shown to be important and the asymmetric line shapes of the O—D stretch Raman scattering and IR absorption spectra of HDO especially in highly concentrated NaCl and KSCN solutions are in quantitative agreement with experimental results. We

  12. The electrochemistry of SIMFUEL in dilute alkaline hydrogen peroxide solutions

    NASA Astrophysics Data System (ADS)

    Goldik, Jon

    The work described in this thesis is a study of the electrochemistry of SIMFUEL (SIMulated nuclear FUEL) in dilute, alkaline hydrogen peroxide solutions. In the first set of experiments, the reaction of H2O 2 on SIMFUEL electrodes was studied electrochemically and under open circuit conditions in 0.1 mol L-1 NaCl solutions at pH 9.8. The composition of the oxidized UO2 surface was determined by X-ray photoelectron spectroscopy. Hydrogen peroxide reduction was found to be catalyzed by the formation of a mixed UIV/UV (UO 2+x) surface layer, but to be blocked by the accumulation of UVI species (UO3· yH2O or adsorbed (UO2)2+) on the electrode surface. The formation of this UVI layer blocks both H2O2 reduction and oxidation, thereby inhibiting the potentially rapid H2O2 decomposition reaction to H2O and O2. Decomposition is found to proceed at a rate controlled by the desorption of the adsorbed (UO2)2+ or reduction of adsorbed O2 species. Reduction of (O2) ads is coupled to the slow oxidative dissolution of UO2 and formation of a corrosion product deposit of UO3· yH2O. In the second series of experiments, the electrochemical reduction of hydrogen peroxide on SIMFUEL was studied using the steady-state polarization technique. Kinetic parameters for the reaction, such as Tafel slopes and reaction orders, were determined. The results were interpreted in terms of a chemical-electrochemical mechanism involving UIV/UV donor-acceptor reduction sites. The large values of the Tafel slopes and the fractional reaction orders with respect to H2O2 can be understood in terms of the potential-dependent surface coverage of active sites, similar to that observed in the reduction of hydrogen peroxide on oxidized copper surfaces. The effects of pH over the range 10-13 were also investigated. The H2O 2 reduction currents were nearly independent of pH in the range 10-11, but were slowed at more alkaline values. The change in pH dependence appears to be related to the acid-base properties

  13. An expression of uncertainty in calibration using stepwise or separate dilution of a stock solution.

    PubMed

    Hayashi, Yuzuru; Matsuda, Rieko

    2006-06-01

    The traditional method for linear calibration can estimate the confidence intervals of calibration lines from a set of experimental data for a single calibration line. However, the following situations, often encountered in laboratories, are out of reach of the method, since the concentrations of the standard solutions are not independent of each other: (A) a standard solution is diluted from a more concentrated one in a stepwise way (stepwise dilution); (B) every standard solution for a calibration experiment is prepared from a stock solution, but the stock solution is newly prepared for each calibration (separate dilution with the variable concentration of the stock solution). This paper puts forward a theory to calculate the confidence intervals of calibration lines in the above situations. Analyses made up of sample weighing, dilution, HPLC measurement and calibration with the linear least-squares fitting are taken as examples. The proposed theory is numerically compared to the traditional method.

  14. Imidazolium salt ion pairs in solution.

    PubMed

    Stassen, Hubert K; Ludwig, Ralf; Wulf, Alexander; Dupont, Jairton

    2015-06-01

    The formation, stabilisation and reactivity of contact ion pairs of non-protic imidazolium ionic liquids (ILs) in solution are conceptualized in light of selected experimental evidence as well theoretical calculations reported mainly in the last ten years. Electric conductivity, NMR, ESI-MS and IR data as well as theoretical calculations support not only the formation of contact ion pairs in solution, but also the presence of larger ionic and neutral aggregates even when dissolved in solvents with relatively high dielectric constants, such as acetonitrile and DMSO. The presence of larger imidazolium supramolecular aggregates is favoured at higher salt concentrations in solvents of low dielectric constant for ILs that contain shorter N-alkyl side chains associated with anions of low coordination ability. The stability and reactivity of neutral contact species are also dependent on the nature of the anion, imidazolium substituents, and are more abundant in ILs containing strong coordinating anions, in particular those that can form charge transfer complexes with the imidazolium cation. Finally, some ILs display reactivities as contact ion pairs rather than solvent-separated ions.

  15. Production of furfural from xylose at atmospheric pressure by dilute sulfuric acid and inorganic salts.

    PubMed

    Rong, Chunguang; Ding, Xuefeng; Zhu, Yanchao; Li, Ying; Wang, Lili; Qu, Yuning; Ma, Xiaoyu; Wang, Zichen

    2012-03-01

    In this paper, the dehydration of xylose to furfural was carried out under atmospheric pressure and at the boiling temperature of a biphasic mixture of toluene and an aqueous solution of xylose, with sulfuric acid as catalyst plus an inorganic salt (NaCl or FeCl(3)) as promoter. The best yield of furfural was 83% under the following conditions: 150 mL of toluene and 10 mL of aqueous solution of 10% xylose (w/w), 10% H(2)SO(4) (w/w), 2.4g NaCl , and heating for 5h. FeCl(3) as promoter was found to be more efficient than NaCl. The addition of DMSO to the aqueous phase in the absence of an inorganic salt was shown to improve the yield of furfural.

  16. Solubility of plutonium and uranium in alkaline salt solutions

    SciTech Connect

    Hobbs, D.T.; Edwards, T.B.; Fleischman, S.D.

    1993-02-12

    The solubility of plutonium and uranium in alkaline salt solutions, which will be processed in the In-Tank Precipitation (ITP) process, was investigated to screen for significant factors and interactions among the factors comprising the salt solutions. The factors included in the study were hydroxide, nitrate, nitrite, aluminate, sulfate, carbonate, and temperature. Over the range of factor concentrations studied, the level of hydroxide in the solution is not sufficient alone to predict the resulting concentration of plutonium and uranium in the solution. Other constituents of the salt solution play an important role in determining the amount of plutonium and uranium in solution. Statistical models predicting the plutonium and uranium concentrations over the range of salt solutions investigated are provided.

  17. Heat-induced formation of myosin oligomer-soluble filament complex in high-salt solution.

    PubMed

    Shimada, Masato; Takai, Eisuke; Ejima, Daisuke; Arakawa, Tsutomu; Shiraki, Kentaro

    2015-02-01

    Heat-induced aggregation of myosin into an elastic gel plays an important role in the water-holding capacity and texture of meat products. Here, we investigated thermal aggregation of porcine myosin in high-salt solution over a wide temperature range by dynamic light scattering experiments. The myosin samples were readily dissolved in 1.0 M NaCl at 25 °C followed by dilution into various salt concentrations. The diluted solutions consistently contained both myosin monomers and soluble filaments. The filament size decreased with increasing salt concentration and temperature. High temperatures above Tm led to at least partial dissociation of soluble filaments and thermal unfolding, resulting in the formation of soluble oligomers and binding to the persistently present soluble filaments. Such a complex formation between the oligomers and filaments has never been observed. Our results provide new insight into the heat-induced myosin gelation in high-salt solution. Copyright © 2014 Elsevier B.V. All rights reserved.

  18. Use of bioadsorbents for removing dissolved metals from dilute solutions

    SciTech Connect

    Watson, J.S.; Scott, C.D. )

    1988-01-01

    Certain microorganisms and other biological materials are able to absorb different metal ions, and this capability can be used to recovery metals from dilute sources or to remove trace impurities from wastewaters. Incorporation of the biosorbent into cross-linked gelatin beads permits them to be used in packed beds where high removal efficiencies can be obtained. Removal of strontium, an important contaminant in radioactive wastewaters, is a significant problem, and selected biosorbents immobilized in gel beds have been shown to have a significant affinity for strontium. Adsorption column performance and the roles of both the gel material and incorporated microorganisms are described.

  19. Pattern Formation in Drying Drops of Polyelectrolyte - Salt Solutions

    NASA Astrophysics Data System (ADS)

    Kaya, Deniz; Belyi, Vladimir A.

    2005-03-01

    We use optical microscopy, AFM, and SEM to investigate salt patterns formed during evaporation of aqueous solutions of sodium poly(styrene sulfonate) and sodium chloride (NaPSS/NaCl). Observed patterns exhibit significantly larger variety than in the simple "drying coffee drop" experiments. We find that varying the concentration ratios of polyelectrolyte/salt solutions leads to formation of qualitatively different patterns, including radially grown salt deposits, concentric rings of salt and other structures. Our results indicate that these patterns are also sensitive to evaporation rate of the droplet. However molecular weight of the polymer appears to have little to no effect on the observed patterns.

  20. Volatile release from aqueous solutions under dynamic headspace dilution conditions.

    PubMed

    Marin, M; Baek, I; Taylor, A J

    1999-11-01

    Static equilibrium was established between the gas phase (headspace) and an unstirred aqueous phase in a sealed vessel. The headspace was then diluted with air to mimic the situation when a container of food is opened and the volatiles are diluted by the surrounding air. Because this first volatile signal can influence overall flavor perception, the parameters controlling volatile release under these conditions are of interest. A mechanistic model was developed and validated experimentally. Release of compounds depended on the air-water partition coefficient (K(aw)) and the mass transport in both phases. For compounds with K(aw) values <10(-)(3), K(aw) was the factor determining release rate. When K(aw) was >10(-)(3), mass transport in the gas phase became significant and the Reynolds number played a role. Because release from packaged foods occurs at low Reynolds numbers, whereas most experiments are conducted at medium to high Reynolds numbers, the experimentally defined profile may not reflect the real situation.

  1. Nanoassociate formation in highly diluted water solutions of potassium phenosan with and without permalloy shielding.

    PubMed

    Konovalov, Alexander; Ryzhkina, Irina; Maltzeva, Elena; Murtazina, Lyaisan; Kiseleva, Yuliya; Kasparov, Valery; Palmina, Nadezhda

    2015-01-01

    Diluted water solutions of anti-oxidant potassium phenosan, kept before explorations in "usual" conditions and in conditions of "permalloy container", i.e. shielding of solution from the influence of external low-frequency electromagnetic and/or geomagnetic fields, were studied. It is shown that in solutions kept in shielded conditions in the area of high dilution with a concentration of solutions lower than "threshold", nanoobjects called "nanoassociates", are not formed, and anomalous physicochemical and biological properties observed in solutions kept in "usual" conditions, are not found. We conclude that anomalous physicochemical and biological properties of highly diluted water solutions of potassium phenosan made under "usual" conditions are determined by "nanoassociates", in which an external low-frequency electromagnetic and/or geomagnetic field is a necessary condition of the formation.

  2. [Structure and Activity of Fungal Lipases in Bile Salt Solutions].

    PubMed

    Bogdanova, L R; Bakirova, D R; Valiullina, Yu A; Idiyatullin, B Z; Faizullin, D A; Zueva, O S; Zuev, Yu F

    2016-01-01

    The changes in structure and catalytic properties of fungal lipases (Candida rugosa, Rhizomucor miehei, Mucor javanicus) were investigated in micellar solutions of bile salts that differ in hydrophilic-lypophilic balance and reaction medium properties. The methods of circular dichroism and tryptophan fluorescence were applied to estimate the changes in peptide structure within complexes with bile salt micelles. Bile salts do not exert a significant influence on the structure of the enzymes under study: in Rh. miehei and M. javanicus lipases the alpha helix content slightly decreased, the influence of bile salts on the C. rugosa structure was not revealed. Despite negligible structural modifications in the enzymes, in bile salt solutions a considerable change in their catalytic properties was observed: an abrupt decrease in catalytic effectiveness. Substrate-bile salts micelles complex formation was demonstrated by the NMR self-diffusion method. The model of a regulation of fungal lipase activity was proposed.

  3. Radiation induced degradation of ketoprofen in dilute aqueous solution

    NASA Astrophysics Data System (ADS)

    Illés, Erzsébet; Takács, Erzsébet; Dombi, András; Gajda-Schrantz, Krisztina; Gonter, Katalin; Wojnárovits, László

    2012-09-01

    The intermediates and final products of ketoprofen degradation were investigated in 0.4 mmol dm-3 solution by pulse radiolysis and gamma radiolysis. For observation of final products UV-vis spectrophotometry and HPLC separation with diode array detection were used, and for identification MS was used. The reactions of •OH lead to hydroxycyclohexadienyl type radical intermediates, in their further reactions hydroxylated derivatives of ketoprofen form as final products. The hydrated electron is scavenged by the carbonyl oxygen and the electron adduct protonates to ketyl radical •OH is more effective in decomposing ketoprofen than hydrated electron. Chemical oxygen demand and total organic carbon content measurements on irradiated aerated solutions showed that using irradiation technology ketoprofen can be mineralised. The initial toxicity of the solution monitored by the Daphnia magna test steadily decreases with irradiation. Using 5 kGy dose no toxicity of the solution was detected with this test.

  4. Conformation of ionizable poly Para phenylene ethynylene in dilute solutions

    DOE PAGES

    Wijesinghe, Sidath; Maskey, Sabina; Perahia, Dvora; ...

    2015-11-03

    The conformation of dinonyl poly para phenylene ethynylenes (PPEs) with carboxylate side chains, equilibrated in solvents of different quality is studied using molecular dynamics simulations. PPEs are of interest because of their tunable electro-optical properties, chemical diversity, and functionality which are essential in wide range of applications. The polymer conformation determines the conjugation length and their assembly mode and affects electro-optical properties which are critical in their current and potential uses. The current study investigates the effect of carboxylate fraction on PPEs side chains on the conformation of chains in the dilute limit, in solvents of different quality. The dinonylmore » PPE chains are modeled atomistically, where the solvents are modeled both implicitly and explicitly. Dinonyl PPEs maintained a stretched out conformation up to a carboxylate fraction f of 0.7 in all solvents studied. The nonyl side chains are extended and oriented away from the PPE backbone in toluene and in implicit good solvent whereas in water and implicit poor solvent, the nonyl side chains are collapsed towards the PPE backbone. Thus, rotation around the aromatic ring is fast and no long range correlations are seen within the backbone.« less

  5. A theoretical framework for modeling dilution enhancement of non-reactive solutes in heterogeneous porous media.

    PubMed

    de Barros, F P J; Fiori, A; Boso, F; Bellin, A

    2015-01-01

    Spatial heterogeneity of the hydraulic properties of geological porous formations leads to erratically shaped solute clouds, thus increasing the edge area of the solute body and augmenting the dilution rate. In this study, we provide a theoretical framework to quantify dilution of a non-reactive solute within a steady state flow as affected by the spatial variability of the hydraulic conductivity. Embracing the Lagrangian concentration framework, we obtain explicit semi-analytical expressions for the dilution index as a function of the structural parameters of the random hydraulic conductivity field, under the assumptions of uniform-in-the-average flow, small injection source and weak-to-mild heterogeneity. Results show how the dilution enhancement of the solute cloud is strongly dependent on both the statistical anisotropy ratio and the heterogeneity level of the porous medium. The explicit semi-analytical solution also captures the temporal evolution of the dilution rate; for the early- and late-time limits, the proposed solution recovers previous results from the literature, while at intermediate times it reflects the increasing interplay between large-scale advection and local-scale dispersion. The performance of the theoretical framework is verified with high resolution numerical results and successfully tested against the Cape Cod field data.

  6. Solute dilution at the Borden and Cape Cod groundwater tracer tests

    USGS Publications Warehouse

    Thierrin, Joseph; Kitanidis, Peter K.

    1994-01-01

    This study presents an analysis of the rate of dilution of a conservative nonreactive tracer in two well-known field experiments: The Borden (Ontario, Canada) experiment and the Cape Cod (Massachusetts) experiment. In evaluating the dilution of injected sodium bromide, in addition to computing the second spatial moments, we have used the dilution index and the reactor ratio. The dilution index is a measure of the formation volume occupied by the solute plume, and the reactor ratio is a shape factor, which measures how stretched and deformed the plume is. Unlike the second moments, which may go up or down during an experiment, the dilution index should increase monotonically. The results for both plumes were quite similar. After an initial period the dilution index increased linearly with time, which is macroscopically equivalent to transport in two-dimensional uniform flow. The reactor ratio was relatively constant during the period of the experiments. Their values, about 0.72 for the Borden test and 0.63 for the Cape Cod test, indicate that the Cape Cod plume was more stretched and deformed than the Borden plume. The maximum concentration, which is an alternative to the dilution index for quantifying dilution, was found to be more erratic and more susceptible to sampling error.

  7. Extraction of ethylene glycol from aqueous salt solutions

    NASA Astrophysics Data System (ADS)

    Butyrskaya, E. V.; Belyakova, N. V.; Rozhkova, M. V.; Nechaeva, L. S.

    2012-11-01

    A method is proposed for extracting ethylene glycol from aqueous salt solutions by dialysis through ion-exchange membranes, based on the Donnan exclusion of the electrolyte. Dialysis is performed in the continuous and batch modes. It is found that the batch mode of dialysis is more effective for extracting ethylene glycol from its aqueous salt solutions. The effect of the ionic form of the membrane on ethylene glycol fluxes is explained through computer simulation.

  8. Microfluidics Meets Dilute Solution Viscometry: An Undergraduate Laboratory to Determine Polymer Molecular Weight Using a Microviscometer

    ERIC Educational Resources Information Center

    Pety, Stephen J.; Lu, Hang; Thio, Yonathan S.

    2011-01-01

    This paper describes a student laboratory experiment to determine the molecular weight of a polymer sample by measuring the viscosity of dilute polymer solutions in a PDMS microfluidic viscometer. Sample data are given for aqueous solutions of poly(ethylene oxide) (PEO). A demonstration of shear thinning behavior using the microviscometer is…

  9. Microfluidics Meets Dilute Solution Viscometry: An Undergraduate Laboratory to Determine Polymer Molecular Weight Using a Microviscometer

    ERIC Educational Resources Information Center

    Pety, Stephen J.; Lu, Hang; Thio, Yonathan S.

    2011-01-01

    This paper describes a student laboratory experiment to determine the molecular weight of a polymer sample by measuring the viscosity of dilute polymer solutions in a PDMS microfluidic viscometer. Sample data are given for aqueous solutions of poly(ethylene oxide) (PEO). A demonstration of shear thinning behavior using the microviscometer is…

  10. The grand partition function of dilute biregular solutions

    NASA Astrophysics Data System (ADS)

    Nagamori, Meguru; Ito, Kimihisa; Tokuda, Motonori

    1994-10-01

    It has been demonstrated that the grand partition function (GPF) of biregular solutions contains in one single equation such thermodynamic principles as Henry's law, Raoult's law, the Gibbs-Duhem relation, Raoultian activity coefficients and their finite power series, Wagner's rec-iprocity, Schenck-Frohberg-Steinmetz's interchange, Lupis-Elliott's additivity, Mori-Morooka's disparity, and Darken's quadratic formalism. The logarithm of the Raoultian activity coefficient of species i, In γi should not be expressed by the Taylor series expansion, lest its truncation infringe the Gibbs-Duhem equation. The GPF methodology establishes that In γi, is not a vector but a scalar point function, free from any path dependence. While Darken's quadratic formalism employs three parameters to describe a ternary solution, the present biregularity approximation offers an alternative using seven empirical parameters, in case better accuracy is needed.

  11. Adsorption of citric acid from dilute aqueous solutions by hydroxyapatite.

    PubMed

    Vega, Enrique D; Narda, Griselda E; Ferretti, Ferdinando H

    2003-12-01

    The role of citric acid in the demineralization of dental enamel, which is mainly constituted by hydroxyapatite, is important for periodontal regeneration and in the conditioning of enamel or dentin for bonding restorative resins. The adsorption of citric acid from aqueous solutions onto synthetic hydroxyapatite at 278, 288, 298, and 308 K and pH 4.8 has been studied by means of UV spectroscopy. The adsorption reaction, which takes place by an interaction between phosphate groups and citrate anions at the solid-solution interface, yields an adsorbate-adsorbent complex of high stability. The adsorption isotherms fit the Langmuirian shape. The proposed adsorption model, where citrate species interact in a bidentate manner (one citrate ion links two phosphate sites), is coherent with the experimental data. The activation standard heat and activation standard entropy were calculated. All the thermodynamic and kinetic parameters were in concordance with the adsorption reaction proposed in this work.

  12. Optical and Rheological Properties of a Semi-Diluted Equimolar Solution of Cetyltrimethylammonium Bromide and Potassium Bromide

    NASA Astrophysics Data System (ADS)

    Decruppe, J. P.; Cappelaere, E.; Cressely, R.

    1997-02-01

    We report in this paper the results of rheological and optical experiments performed on a semi-diluted viscoelastic solution of cetyltrimethylammonium bromide (CTAB) in water with sodium bromide at a concentration of 0.3 M l^{-1} in surfactant and salt. This concentration in surfactant is much smaller than the concentration which gives a nematic phase at rest. The solution behaves like a Maxwell fluid with a single relaxation time. When submitted to a shear flow, this solution shows a behaviour typical of a system undergoing a phase transition. When observed between crossed polarizer and analyzer, the gap of the Couette cell appears divided in two bands the optical properties of which are different; in rheology, the curves σ(dot{γ}) are also characteristic of these systems where the shear stress presents a plateau extending between two critical values, dot{γ}_{1c}, and dot{γ}_{2c} of the shear rate. We finally compare the results with previous experiments performed on a concentrated solution of CTAB containing no salt.

  13. Form and stability of aluminum hydroxide complexes in dilute solution

    USGS Publications Warehouse

    Hem, John David; Roberson, Charles Elmer

    1967-01-01

    Laboratory studies of solutions 4.53 x 10 -4 to 4.5 x 10 -5 molal (12.2-1.2 ppm) in aluminum, in 0.01 molal sodium perchlorate, were conducted to obtain information as to the probable behavior of aluminum in natural water. When the solutions were brought to pH 7.5-9.5 and allowed to stand for 24 hours, a precipitate was obtained which was virtually amorphous as shown by X-rays, and which had a solubility equivalent to that of boehmite. This precipitate had a hydrolysis constant (*Ks4) of 1.93 x 10 -13a. When solutions were allowed to stead at this pH range for 10 days, their precipitates gave the X-ray pattern of bayerite (*Ks4 = 1.11 > (10- 4). These hydrolysis constants were obtained at 25?C. and corrected to zero ionic strength and are in close agreement with other published values. The predominant dissolved form in this pH range is Al(OH) -4. Below neutral pH (7.0) the dissolved aluminum species consist of octahedral units in which each aluminum ion is surrounded by six water molecules or hydroxide ions. Single units such as Al(OH2)6 + 3 and AlOH(OH2)5+2 are most abundant below pH 5.0, and where the molar ratio (r) of combined hydroxide to total dissolved aluminum is low. When r is greater than 1.0, polymerization of the octahedral units occurs. When r is between 2.0 and 3.0, solutions aged for 10 days or more contained colloidal particles between 0.10 and 0.45 ? in diameter. Particles whose diameters were greater than 0.10 ? were identified by X-ray diffraction as gibbsite. Particles smaller than 0.10 ? were also present and were shown by means of the electron microscope to have a hexagonal crystal pattern. Structured material consisting of sheets of coalesced six-membered rings of aluminum ions held together by double OH bridges has a distinctive kinetic behavior. This property was used to determine amounts of polymerized material in solutions having r between 1.0 and 3.0 after aging times ranging from a few hours to more than 4 months. Aging increased the

  14. Photochemical dehydrogenation of ethanol in dilute aqueous solution

    NASA Astrophysics Data System (ADS)

    Handman, J.; Harriman, A.; Porter, G.

    1984-02-01

    The cyclic photodissociation of water has not yet been achieved in a homogeneous solution using visible light. The replacement of the sacrificial electron donor with such waste materials as sulfide is suggested as a method for improving homogeneous systems. Attention is given to the efficient photogeneration of H2 by means of a system that employs a low grade fermentation product, aqueous ethanol, as electron donor. The photoproduction of H2 is coupled to the oxidation of the ethanol by means of NADH/alcohol dehydrogenase as a relay.

  15. Effect of ice growth rate on the measured Workman-Reynolds freezing potential between ice and dilute NaCl solutions.

    PubMed

    Wilson, P W; Haymet, A D J

    2010-10-07

    Workman-Reynolds freezing potentials have been measured across the interface between ice and dilute NaCl solutions as a function of ice growth rate for three salt concentrations. Growth rates of up to 40 μm·s(-1) are used, and it is found that the measured voltage peaks at rates of ∼25 μm·s(-1). Our initial results indicate that the freezing potential can be used as a probe into various aspects of the DC electrical resistance of ice as a function of variables such as salt concentration.

  16. Adsorption of organic acids from dilute aqueous solution onto activated carbon

    SciTech Connect

    Wang, S.W.

    1980-06-01

    The radioisotope technique was used to study the removal of organic acid contaminants from dilute aqueous solutions onto activated carbon. Acetic acid, propionic acid, n-butyric acid, n-hexanoic acid and n-heptanoic acid were studied at 278, 298, and 313/sup 0/K. Three bi-solute acid mixtures (acetic and propionic acids, acetic and butanoic acids, and propionic and butanoic acids) were studied at 278 and 298/sup 0/K. Isotherms of the single-solute systems were obtained at three different temperatures in the very dilute concentration region (less than 1% by weight). These data are very important in the prediction of bi-solute equilibrium data. A Polanyi-based competitive adsorption potential theory was used to predict the bi-solute equilibrium uptakes. Average errors between calculated and experimental data ranges from 4% to 14%. It was found that the competitive adsorption potential theory gives slightly better results than the ideal adsorbed solution theory.

  17. Hydration of Kr(aq) in dilute and concentrated solutions

    SciTech Connect

    Chaudhari, Mangesh I.; Sabo, Dubravko; Pratt, Lawrence R.; Rempe, Susan B.

    2014-10-13

    Molecular dynamics simulations of water with both multi-Kr and single Kr atomic solutes are carried out to implement quasi-chemical theory evaluation of the hydration free energy of Kr(aq). This approach obtains free energy differences reflecting Kr–Kr interactions at higher concentrations. Those differences are negative changes in hydration free energies with increasing concentrations at constant pressure. The changes are due to a slight reduction of packing contributions in the higher concentration case. The observed Kr–Kr distributions, analyzed with the extrapolation procedure of Krüger et al., yield a modestly attractive osmotic second virial coefficient, B2 ≈ -60 cm3/mol. Moreover, the thermodynamic analysis interconnecting these two approaches shows that they are closely consistent with each other, providing support for both approaches.

  18. Hydration of Kr(aq) in Dilute and Concentrated Solutions.

    PubMed

    Chaudhari, Mangesh I; Sabo, Dubravko; Pratt, Lawrence R; Rempe, Susan B

    2015-07-23

    Molecular dynamics simulations of water with both multi-Kr and single Kr atomic solutes are carried out to implement quasi-chemical theory evaluation of the hydration free energy of Kr(aq). This approach obtains free energy differences reflecting Kr-Kr interactions at higher concentrations. Those differences are negative changes in hydration free energies with increasing concentrations at constant pressure. The changes are due to a slight reduction of packing contributions in the higher concentration case. The observed Kr-Kr distributions, analyzed with the extrapolation procedure of Krüger et al., yield a modestly attractive osmotic second virial coefficient, B2 ≈ -60 cm(3)/mol. The thermodynamic analysis interconnecting these two approaches shows that they are closely consistent with each other, providing support for both approaches.

  19. Hydration of Kr(aq) in dilute and concentrated solutions

    DOE PAGES

    Chaudhari, Mangesh I.; Sabo, Dubravko; Pratt, Lawrence R.; ...

    2014-10-13

    Molecular dynamics simulations of water with both multi-Kr and single Kr atomic solutes are carried out to implement quasi-chemical theory evaluation of the hydration free energy of Kr(aq). This approach obtains free energy differences reflecting Kr–Kr interactions at higher concentrations. Those differences are negative changes in hydration free energies with increasing concentrations at constant pressure. The changes are due to a slight reduction of packing contributions in the higher concentration case. The observed Kr–Kr distributions, analyzed with the extrapolation procedure of Krüger et al., yield a modestly attractive osmotic second virial coefficient, B2 ≈ -60 cm3/mol. Moreover, the thermodynamic analysismore » interconnecting these two approaches shows that they are closely consistent with each other, providing support for both approaches.« less

  20. Biosorption of heavy metals and uranium from dilute solutions

    SciTech Connect

    Schneider, I.A.H.; Misra, M.; Smith, R.W.

    1995-08-01

    Eichhornia crassipes approaches being a scourge in many parts of the world, choking waterways and hindering transport upon them. At the same time it is known to readily abstract heavy metal ions from water and, thus, aids in the removal of heavy metals found in such waters. This paper considers the possibility of using specific parts of the plant as an inexpensive adsorbent for the removal of heavy metals from contaminated chemical and mining industry waste waters. In particular the root of the plant was found to be an excellent accumulator of heavy metal ions including uranium from solution. It is also suggested that dried roots of the plant might be placed in simple bags and used in a very low cost metal ion removal system.

  1. Stability of Diluted Adenosine Solutions in Polyolefin Infusion Bags

    PubMed Central

    Almagambetova, Elise; Hutchinson, David; Blais, Danielle M.; Zhao, Fang

    2013-01-01

    Background: Intravenous or intracoronary adenosine is used in the cardiac catherization lab to achieve maximal coronary blood flow and determine fractional flow reserve. Objective: To determine the stability of adenosine 10 and 50 µg/mL in either 0.9% sodium chloride injection or 5% dextrose injection in polyolefin infusion bags stored at 2 temperatures, refrigeration (2°C-8°C) or controlled room temperature (20°C-25°C). Methods: Adenosine 10 µg/mL and 50 µg/mL solutions were prepared in 50 mL polyolefin infusion bags containing 0.9% sodium chloride injection or 5% dextrose injection and stored at controlled room temperature or under refrigeration. Each combination of concentration, diluent, and storage was prepared in triplicate. Samples were assayed using stability-indicating, reversed-phase high-performance liquid chromatography immediately at time 0 and at 24 hours, 48 hours, 7 days, and 14 days. Stability was defined as retaining 90% to 110% of the initial adenosine concentration. The samples were also visually inspected against a light background for clarity, color, and the presence of particulate matter. Results: After 14 days, all samples retained 99% to 101% of the initial adenosine concentration. No considerable change in pH or visual appearance was noted. The stability data indicated no significant loss of drug due to chemical degradation or physical interactions during storage. Conclusion: Adenosine solutions of 10 and 50 µg/mL were stable for at least 14 days in 50 mL polyolefin infusion bags of 0.9% sodium chloride injection or 5% dextrose injection stored at controlled room temperature and refrigerated conditions. PMID:24421510

  2. A new class of draw solutions for minimizing reverse salt flux to improve forward osmosis desalination.

    PubMed

    Nguyen, Hau Thi; Nguyen, Nguyen Cong; Chen, Shiao-Shing; Ngo, Huu Hao; Guo, Wenshan; Li, Chi-Wang

    2015-12-15

    The applications of forward osmosis (FO) have been hindered because of the lack of an optimal draw solution. The reverse salt flux from the draw solution not only reduces the water flux but also increases the cost of draw solute replenishment. Therefore, in this study, Tergitol NP7 and NP9 with a long straight carbon chain and low critical micelle concentration (CMC) were coupled with highly charged ethylenediaminetetraacetic acid (EDTA) as an innovative draw solution to minimize reverse salt diffusion in FO for the first time. The results showed that the lowest reverse salt flux of 0.067 GMH was observed when 0.1M EDTA-2Na coupled with 15mM NP7 was used as a draw solution and deionized water was used as a feed solution in FO mode (active layer facing with the feed solution). This is due to the hydrophobic interaction between the tails of NP7 and the FO membrane, thus creating layers on the membrane surface and constricting the FO membrane pores. Moreover, 1M EDTA-2Na coupled with 15mM NP7 is promising as an optimal draw solution for brackish water and sea water desalination. Average water fluxes of 7.68, 6.78, and 5.95 LMH were achieved when brackish water was used as a feed solution (5, 10, and 20g/L NaCl), and an average water flux of 3.81 LMH was achieved when sea water was used as a feed solution (35g/L NaCl). The diluted draw solution was recovered using a nanofiltration (NF-TS80) membrane with a high efficiency of 95% because of the high charge and large size of the draw solution. Copyright © 2015 Elsevier B.V. All rights reserved.

  3. Dynamics of single semiflexible polymers in dilute solution.

    PubMed

    Nikoubashman, Arash; Milchev, Andrey; Binder, Kurt

    2016-12-21

    We study the dynamics of a single semiflexible chain in solution using computer simulations, where we systematically investigate the effect of excluded volume, chain stiffness, and hydrodynamic interactions. We achieve excellent agreement with previous theoretical considerations, but find that the crossover from the time τb, up to which free ballistic motion of the monomers describes the chain dynamics, to the times W(-1) or τ0, where anomalous monomer diffusion described by Rouse-type and Zimm-type models sets in, requires two decades of time. While in the limit of fully flexible chains the visibility of the anomalous diffusion behavior is thus rather restricted, the t(3/4) power law predicted for stiff chains without hydrodynamic interactions is verified. Including hydrodynamics, evidence for the predicted [tln(t)](3/4) behavior is obtained. Similar good agreement with previous theoretical predictions is found for the decay of the bond autocorrelation functions and the end-to-end vector correlation. Finally, several predictions on the variation of characteristic relaxation times with persistence length describing the chain stiffness are tested.

  4. Spectrofluorimetric determination of trace aluminum in diluted hemodialysis solutions

    NASA Astrophysics Data System (ADS)

    Gündüz, S. Beniz; Küçükkolbaşý, Semahat; Atakol, Orhan; Kýlýç, Esma

    2005-03-01

    In this study, a spectrofluorimetric method has been developed for the determination of aluminum based on the formation of an aluminum complex with N, N'-disalicylidene-1,3-diamino-2-hydroxypropane (DSAHP). The most suitable pH, solvent medium, complex formation time, Schiff base concentration and temperature were determined. The excitation and emission wavelengths were 270 and 437 nm, respectively, in which the DSAHP-Al complex gave the maximum flurescence intensity at pH 3.0 and 6.0 in 50% dioxan-50% water medium. Under these conditions, calibration curves were obtained in three different linear limits, and was found that aluminum could be detected within the concentration limit of 0-10.0 μM and the lowest detection limit being 0.27 ng ml -1. The stochiometry of the DSAHP-Al complex was also determined spectrofluorimetrically under optimal conditions and the molar ratio of DSAHP-Al was calculated as 2:1. Using the developed method, aluminum was detected in hemodialysis solutions, and the results obtained were similar and comparable with those obtained using the method described in the British Pharmacopoeia within 95% confidence limits. This method can be used successfully for the routine determination of aluminum because it is quick, requires less amount of reactives, is sensitive, reliable and reproducible.

  5. Dynamics of single semiflexible polymers in dilute solution

    NASA Astrophysics Data System (ADS)

    Nikoubashman, Arash; Milchev, Andrey; Binder, Kurt

    2016-12-01

    We study the dynamics of a single semiflexible chain in solution using computer simulations, where we systematically investigate the effect of excluded volume, chain stiffness, and hydrodynamic interactions. We achieve excellent agreement with previous theoretical considerations, but find that the crossover from the time τb, up to which free ballistic motion of the monomers describes the chain dynamics, to the times W-1 or τ0, where anomalous monomer diffusion described by Rouse-type and Zimm-type models sets in, requires two decades of time. While in the limit of fully flexible chains the visibility of the anomalous diffusion behavior is thus rather restricted, the t3/4 power law predicted for stiff chains without hydrodynamic interactions is verified. Including hydrodynamics, evidence for the predicted [tln (t ) ] 3 /4 behavior is obtained. Similar good agreement with previous theoretical predictions is found for the decay of the bond autocorrelation functions and the end-to-end vector correlation. Finally, several predictions on the variation of characteristic relaxation times with persistence length describing the chain stiffness are tested.

  6. METHOD AND APPARATUS FOR CALCINING SALT SOLUTIONS

    DOEpatents

    Lawroski, S.; Jonke, A.A.; Taecker, R.G.

    1961-10-31

    A method is given for converting uranyl nitrate solution into solid UO/ sub 3/, The solution is sprayed horizontally into a fluidized bed of UO/sub 3/ particles at 310 to 350 deg C by a nozzle of the coaxial air jet type at about 26 psig, Under these conditions the desired conversion takes place, and caking in the bed is avoided.

  7. Effects of coprecipitation on uranium and plutonium concentrations in alkaline salt solutions

    SciTech Connect

    Hobbs, D.T.

    1997-03-19

    The chemistry of uranium and plutonium in conjunction with the storage, retrieval and treatment of high-level nuclear waste (HLW) has been the subject of increasing scrutiny due to concerns with nuclear criticality safety. Previous studies focused on determining the solubilities of plutonium and uranium in alkaline salt solutions that encompass the compositions present during storage and evaporation of fresh and aged. Recent studies extend the chemistry to include the effects of coprecipitation on the liquid phase concentrations of plutonium and uranium. Particle size, morphology and identification of crystalline phases in the precipitated solids as well as the plutonium and uranium dissolution characteristics upon dilution of the liquid phases were also determined.

  8. Protein–Protein Interactions in Dilute to Concentrated Solutions: α-Chymotrypsinogen in Acidic Conditions

    PubMed Central

    2015-01-01

    Protein–protein interactions were investigated for α-chymotrypsinogen by static and dynamic light scattering (SLS and DLS, respectively), as well as small-angle neutron scattering (SANS), as a function of protein and salt concentration at acidic conditions. Net protein–protein interactions were probed via the Kirkwood–Buff integral G22 and the static structure factor S(q) from SLS and SANS data. G22 was obtained by regressing the Rayleigh ratio versus protein concentration with a local Taylor series approach, which does not require one to assume the underlying form or nature of intermolecular interactions. In addition, G22 and S(q) were further analyzed by traditional methods involving fits to effective interaction potentials. Although the fitted model parameters were not always physically realistic, the numerical values for G22 and S(q → 0) were in good agreement from SLS and SANS as a function of protein concentration. In the dilute regime, fitted G22 values agreed with those obtained via the osmotic second virial coefficient B22 and showed that electrostatic interactions are the dominant contribution for colloidal interactions in α-chymotrypsinogen solutions. However, as protein concentration increases, the strength of protein–protein interactions decreases, with a more pronounced decrease at low salt concentrations. The results are consistent with an effective “crowding” or excluded volume contribution to G22 due to the long-ranged electrostatic repulsions that are prominent even at the moderate range of protein concentrations used here (<40 g/L). These apparent crowding effects were confirmed and quantified by assessing the hydrodynamic factor H(q → 0), which is obtained by combining measurements of the collective diffusion coefficient from DLS data with measurements of S(q → 0). H(q → 0) was significantly less than that for a corresponding hard-sphere system and showed that hydrodynamic nonidealities can lead to qualitatively incorrect

  9. Optimization of salt concentration in PEG-based crystallization solutions.

    PubMed

    Yamanaka, Mari; Inaka, Koji; Furubayashi, Naoki; Matsushima, Masaaki; Takahashi, Sachiko; Tanaka, Hiroaki; Sano, Satoshi; Sato, Masaru; Kobayashi, Tomoyuki; Tanaka, Tetsuo

    2011-01-01

    Although polyethylene glycol (PEG) is the most widely used precipitant in protein crystallization, the concentration of co-existing salt in the solution has not been well discussed. To determine the optimum salt concentration range, several kinds of protein were crystallized in a 30% PEG 4000 solution at various NaCl concentrations with various pH levels. It was found that, if crystallization occurred, the lowest effective salt concentration depended on the pH of the protein solution and the pI of the protein molecule; that is, higher salt concentrations were required for crystal growth if the difference between pH and pI was increasing. The linear relationship between the charge density of the protein and the ionic strength of the crystallization solution was further verified. These results suggested that the lowest effective concentration of salt in a crystallization solution can be predicted before performing a crystallization experiment. Our results can be a tip for tuning crystallization conditions by the vapor-diffusion method.

  10. SWELLING OF ERYTHROCYTES IN SOLUTIONS OF AMMONIUM SALTS

    PubMed Central

    Schiödt, E.

    1933-01-01

    Two rather simple equations have been derived, which make it possible to express in a single number the result of a series of determinations of the volume of erythrocytes swelling in solutions of ammonium salts. In all experiments made with several combinations of different concentrations of permeating and non-permeating salts, the curves calculated from the equations have covered the points found by experiment. PMID:19872754

  11. Brine rejection from freezing salt solutions: a molecular dynamics study.

    PubMed

    Vrbka, Lubos; Jungwirth, Pavel

    2005-09-30

    The atmospherically and technologically very important process of brine rejection from freezing salt solutions is investigated with atomic resolution using molecular dynamics simulations. The present calculations allow us to follow the motion of each water molecule and salt ion and to propose a microscopic mechanism of brine rejection, in which a fluctuation (reduction) of the ion density in the vicinity of the ice front is followed by the growth of a new ice layer. The presence of salt slows down the freezing process, which leads to the formation of an almost neat ice next to a disordered brine layer.

  12. Counterion adsorption theory of dilute polyelectrolyte solutions: apparent molecular weight, second virial coefficient, and intermolecular structure factor.

    PubMed

    Muthukumar, M

    2012-07-21

    Polyelectrolyte chains are well known to be strongly correlated even in extremely dilute solutions in the absence of additional strong electrolytes. Such correlations result in severe difficulties in interpreting light scattering measurements in the determination of the molecular weight, radius of gyration, and the second virial coefficient of charged macromolecules at lower ionic strengths from added strong electrolytes. By accounting for charge-regularization of the polyelectrolyte by the counterions, we present a theory of the apparent molecular weight, second virial coefficient, and the intermolecular structure factor in dilute polyelectrolyte solutions in terms of concentrations of the polymer and the added strong electrolyte. The counterion adsorption of the polyelectrolyte chains to differing levels at different concentrations of the strong electrolyte can lead to even an order of magnitude discrepancy in the molecular weight inferred from light scattering measurements. Based on counterion-mediated charge regularization, the second virial coefficient of the polyelectrolyte and the interchain structure factor are derived self-consistently. The effect of the interchain correlations, dominating at lower salt concentrations, on the inference of the radius of gyration and on molecular weight is derived. Conditions for the onset of nonmonotonic scattering wave vector dependence of scattered intensity upon lowering the electrolyte concentration and interpretation of the apparent radius of gyration are derived in terms of the counterion adsorption mechanism.

  13. Translating Thermal Response of Triblock Copolymer Assemblies in Dilute Solution to Macroscopic Gelation and Phase Separation

    SciTech Connect

    Sun, Zhe; Tian, Ye; Hom, Wendy L.; Gang, Oleg; Bhatia, Surita R.; Grubbs, Robert B.

    2016-12-28

    The thermal response of semi-dilute solutions (5 w/w%) of two amphiphilic thermoresponsive poly(ethylene oxide)-b-poly(N,N-diethylacrylamide)-b-poly(N,N-dibutylacrylamide) (PEO45-PDEAmx-PDBAm12) triblock copolymers, which differ only in the size of the central responsive block, in water was examined in this paper. Aqueous PEO45-PDEAm41-PDBAm12 solutions, which undergo a thermally induced sphere-to-worm transition in dilute solution, were found to reversibly form soft (G'≈10 Pa) free-standing physical gels after 10 min at 55 °C. PEO45-PDEAm89-PDBAm12 copolymer solutions, which undergo a thermally induced transition from spheres to large compound micelles (LCM) in dilute solution, underwent phase separation after heating at 55 °C for 10 min owing to sedimentation of LCMs. The reversibility of LCM formation was investigated as a non-specific method for removal of a water-soluble dye from aqueous solution. Finally, the composition and size of the central responsive block in these polymers dictate the microscopic and macroscopic response of the polymer solutions as well as the rates of transition between assemblies.

  14. Translating Thermal Response of Triblock Copolymer Assemblies in Dilute Solution to Macroscopic Gelation and Phase Separation

    DOE PAGES

    Sun, Zhe; Tian, Ye; Hom, Wendy L.; ...

    2016-12-28

    The thermal response of semi-dilute solutions (5 w/w%) of two amphiphilic thermoresponsive poly(ethylene oxide)-b-poly(N,N-diethylacrylamide)-b-poly(N,N-dibutylacrylamide) (PEO45-PDEAmx-PDBAm12) triblock copolymers, which differ only in the size of the central responsive block, in water was examined in this paper. Aqueous PEO45-PDEAm41-PDBAm12 solutions, which undergo a thermally induced sphere-to-worm transition in dilute solution, were found to reversibly form soft (G'≈10 Pa) free-standing physical gels after 10 min at 55 °C. PEO45-PDEAm89-PDBAm12 copolymer solutions, which undergo a thermally induced transition from spheres to large compound micelles (LCM) in dilute solution, underwent phase separation after heating at 55 °C for 10 min owing to sedimentation of LCMs.more » The reversibility of LCM formation was investigated as a non-specific method for removal of a water-soluble dye from aqueous solution. Finally, the composition and size of the central responsive block in these polymers dictate the microscopic and macroscopic response of the polymer solutions as well as the rates of transition between assemblies.« less

  15. Thermally induced suppression of interchain interactions in dilute aqueous solutions of conjugated polyelectrolyte rotaxanes and their analogues

    NASA Astrophysics Data System (ADS)

    Tregnago, Giulia; Afshar, Ali; McDonnell, Shane O.; Anderson, Harry L.; Cacialli, Franco

    2017-08-01

    We use steady-state and nanosecond time-resolved photoluminescence spectroscopy to investigate the evolution of packing interactions in dilute solutions of a sulfonated poly(diphenylenevinylene) lithium salt and its cyclodextrin-threaded polyrotaxanes as a function of the threading ratio (TR) when increasing the temperature from 10 to 40 °C. Contrary to the expectation of a temperature-induced increase of packing and aggregation, supported by previous Raman studies identifying a temperature-induced reduction in the inter-phenyl torsion angles, we find clear spectral (photoluminescence blue-shift and narrowing) and dynamic (shorter lifetimes and reduced weight of the long-lived components) signatures of a reduction of interchain interactions for the polyelectrolytes at higher temperatures with TR up to 1.3.

  16. Forces between hydrophobic solids in concentrated aqueous salt solution.

    PubMed

    Mastropietro, Dean J; Ducker, William A

    2012-03-09

    Much research has focused on the discovery and description of long-ranged forces between hydrophobic solids immersed in water. Here we show that the force between high contact-angle solids in concentrated salt solution (1 M KCl) agrees very well with van der Waals forces calculated from Lifshitz theory for separations greater than 5 nm. The hydrophobic solids are octadecyltrichlorosilane-coated glass, with an advancing contact angle of 108°. Thus, in 1 M salt solution, it is unnecessary to invoke the presence of a hydrophobic force at separations greater than 5 nm. Through measurement in salt solution, we avoid the necessity of accounting for large electrostatic forces that frequently occur in pure water and may obscure resolution of other forces.

  17. Improved cryopreservation by diluted vitrification solution with supercooling-facilitating flavonol glycoside.

    PubMed

    Kami, Daisuke; Kasuga, Jun; Arakawa, Keita; Fujikawa, Seizo

    2008-12-01

    The effect of kaempferol-7-O-glucoside (KF7G), one of the supercooling-facilitating flavonol glycosides which was originally found in deep supercooling xylem parenchyma cells of the katsura tree and was found to exhibit the highest level of supercooling-facilitating activity among reported substances, was examined for successful cryopreservation by vitrification procedures, with the aim of determining the possibility of using diluted vitrification solution (VS) to reduce cryoprotectant toxicity and also to inhibit nucleation at practical cooling and rewarming by the effect of supplemental KF7G. Examination was performed using shoot apices of cranberry and plant vitrification solution 2 (PVS2) with dilution. Vitrification procedures using the original concentration (100%) of PVS2 caused serious injury during treatment with PVS2 and resulted in no regrowth after cooling and rewarming (cryopreservation). Dilution of the concentration of PVS2 to 75% or 50% (with the same proportions of constituents) significantly reduced injury by PVS2 treatment, but regrowth was poor after cryopreservation. It is thought that dilution of PVS2 reduced injury by cryoprotectant toxicity, but such dilution caused nucleation during cooling and/or rewarming, resulting in poor survival. On the other hand, addition of 0.5mg/ml (0.05% w/v) KF7G to the diluted PVS2 resulted in significantly (p<0.05) higher regrowth rates after cryopreservation. It is thought that addition of supercooling-facilitating KF7G induced vitrification even in diluted PVS2 probably due to inhibition of ice nucleation during cooling and rewarming and consequently resulted in higher regrowth. The results of the present study indicate the possibility that concentrations of routinely used VSs can be reduced by adding supercooling-facilitating KF7G, by which more successful cryopreservation might be achieved for a wide variety of biological materials.

  18. Infrared spectroscopy of aqueous ionic salt solutions at low concentrations

    NASA Astrophysics Data System (ADS)

    Max, Jean-Joseph; Gessinger, Véronique; van Driessche, Caroline; Larouche, Pascal; Chapados, Camille

    2007-05-01

    The analysis by infrared spectroscopy of aqueous solutions of the binary inorganic salts NaI and NaCl and the ternary salts CaCl2 and BaCl2 at concentrations from 1000to2mM was carried out to complement a previous study done at higher concentrations on nine binary salts (alkali halides) and one ternary salt (MgCl2) [J.-J. Max and C. Chapados, J. Chem. Phys. 115, 2664 (2001)]. These salts are completely ionized in aqueous solutions, forming monoatomic species that do not absorb IR but that perturb the surrounding water, modifying its spectrum. The factor analysis of the spectra revealed that all these salt solutions were composed of two water types: pure water and salt solvated water. The authors obtained pure salt solvated water spectra for all the salts using an extrapolation technique. The water types obtained are constant for the binary and ternary salts down to 2mM. For the binary salts, we determine that 5.0 and 4.0 water molecules are solvated to the Na +-Cl- and Na+-I- ion pairs, respectively. These numbers are the same as that obtained at higher concentrations. For the new ternary salts, we find that 6.0 and 8.0 water molecules are solvated to Ca++-(Cl-)2 and Ba++-(Cl-)2 ion pairs, respectively. These numbers are higher than the four water molecules solvated to Mg++-(Cl-)2 ion pairs determined previously, but show a progression that follows their atomic numbers. These results constitute new experimental results on "simple" systems whose molecular organization is still a matter of debate. The IR method that probes the system at the molecular level is a method different than the macroscopic ones that give the activity coefficients. The IR gives direct observation at the molecular level of the strong ion-water interactions that are often neglected and its water structure not considered in macroscopic methods. The present results and their analysis together with those obtained by other methods will facilitate the determination of the organization of these

  19. Cholesterol crystallization from a dilute bile salt-rich model bile

    NASA Astrophysics Data System (ADS)

    Konikoff, Fred M.; Carey, Martin C.

    1994-11-01

    In earlier work we showed that cholesterol monohydrate crystallization from model and native biles can involve filamentous cholesterol crystals, and other metastable intermediates which are covered by a layer of phosphatidylcholine (lecithin) molecules [Konikoff et al., J. Clin. Invest. 90 (1992) 1155]. The aim of the present study was to isolate the initial filamentous cholesterol crystals by density gradient centrifugation and microfiltration and to sequentially monitor their transformations into equilibrium plates within the mother liquor composed of a dilute (1.2 g/dl) bile salt-rich model bile (cholesterol/egg yolk lecithin/sodium taurocholate, 1.7/0.8/97.5 mol%). When assayed by dual radiolabeling at 37°C, total precipitated cholesterol in bile increased from zero at 2-4 h of incubation to 43% at 24 h, reaching a stable value by 48 h when 36% of total cholesterol had crystallized. Isopycnic sucrose density gradient centrifugation at 20°C separated early filamentous crystals from plate-like crystals and revealed densities compatible with anhydrous cholesterol (1.029 g/ml) and cholesterol monohydrate (1.048 g/ml), respectively. Rapid (1 h) density gradient centrifugation carried-out in time-lapse sequence disclosed that cholesterol crystallization involved initially low-density (1.01-1.03 g/ml) filamentous crystals, which reached a maximal concentration at 24 h and disappeared gradually by 156 h of incubation. Concomitantly, the concentrations of high-density (1.04-1.06 g/ml) plate-like cholesterol crystals increased reciprocally throughout the crystallization process suggesting a precursor-product relationship. Rates of crystal filament formation and transitions to thermodynamically stable plates accelerated curvilinearly with increases in temperature from 4 to 60°C, but the crystallization process per se remained unchanged. We conclude that metastable intermediate crystals during cholesterol precipitation from bile may involve either low-density anhydrous

  20. Protein diffusiophoresis and salt osmotic diffusion in aqueous solutions.

    PubMed

    Annunziata, Onofrio; Buzatu, Daniela; Albright, John G

    2012-10-25

    Diffusion of a solute can be induced by the concentration gradient of another solute in solution. This transport mechanism is known as cross-diffusion. We have investigated cross-diffusion in a ternary protein-salt-water system. Specifically, we measured the two cross-diffusion coefficients for the lysozyme-NaCl-water system at 25 °C and pH 4.5 as a function of protein and salt concentrations by Rayleigh interferometry. One cross-diffusion coefficient characterizes salt osmotic diffusion induced by a protein concentration gradient, and is related to protein-salt thermodynamic interactions as described by the theories of Donnan membrane equilibrium and protein preferential hydration. The other cross-diffusion coefficient characterizes protein diffusiophoresis induced by a salt concentration gradient, and is described as the difference between a preferential-interaction coefficient and a transport parameter. We first relate our experimental results to the protein net charge and the thermodynamic excess of water near the protein surface. We then extract the Stefan-Maxwell diffusion coefficient describing protein-salt interactions in water. We find that the value of this coefficient is negative, contrary to the friction interpretation of Stefan-Maxwell equations. This result is explained by considering protein hydration. Finally, protein diffusiophoresis is quantitatively examined by considering electrophoretic and hydration effects on protein migration and utilized to accurately estimate lysozyme electrophoretic mobility. To our knowledge, this is the first time that protein diffusiophoresis has been experimentally characterized and a protein-salt Stefan-Maxwell diffusion coefficient reported. This work represents a significant contribution for understanding and modeling the effect of concentration gradients in protein-salt aqueous systems relevant to diffusion-based mass-transfer technologies and transport in living systems.

  1. FREEZING POINTS OF ANTI-COAGULANT SALT SOLUTIONS.

    PubMed

    Hitchcock, D I; Dougan, R B

    1935-03-20

    By a method involving equilibration of ice and solution, and analysis of the solution, freezing point depressions of solutions of sodium citrate, oxalate, and fluoride have been determined over the range Delta = 0.45 to 0.65 degrees C. Determinations with sodium chloride solutions have confirmed the accuracy of the method. In each case the freezing point depression is given, within 0.002 degrees C., as a linear function of the concentration. By the use of these linear equations it is possible to prepare a solution of any of these four salts isotonic with a given biological fluid of known freezing point, provided the latter falls within the range studied.

  2. A conductance study of guanidinium chloride, thiocyanate, sulfate, and carbonate in dilute aqueous solutions: ion-association and carbonate hydrolysis effects.

    PubMed

    Hunger, Johannes; Neueder, Roland; Buchner, Richard; Apelblat, Alexander

    2013-01-17

    We study the conductance of dilute aqueous solutions for a series of guandinium salts at 298.15 K. The experimental molar conductivities were analyzed within the framework of the Quint-Viallard theory in combination with Debye-Hückel activity coefficients. From this analysis, we find no evidence for significant ion association in aqueous solutions of guanidinium chloride (GdmCl) and guanidinium thiocyanate (GdmSCN), and the molar conductivity of these electrolytes can be modeled assuming a complete dissociation. The limiting ionic conductivity of the guanidinium ion (Gdm(+)) is accurately determined to λ(Gdm(+)) = 51.45 ± 0.10 S cm(2) mol(-1). For the bivalent salts guanidinium sulfate (Gdm(2)SO(4)) and guanidinium carbonate (Gdm(2)CO(3)), the molar conductivities show small deviations from ideal (fully dissociated electrolyte) behavior, which are related to weak ion association in solution. Furthermore, for solutions of Gdm(2)CO(3), the hydrolysis of the carbonate anion leads to distinctively increased molar conductivities at high dilutions. The observed ion association is rather weak for all studied electrolytes and cannot explain the different protein denaturing activities of the studied guanidinium salts, as has been proposed previously.

  3. Aggregation behavior of bile salts in aqueous solution.

    PubMed

    Coello, A; Meijide, F; Núñez, E R; Tato, J V

    1996-01-01

    Freezing point depression, delta T/k, and pNa are measured and analyzed for aqueous solutions of trihydroxy (NaTC) and dihydroxy (NaDC and NaTDC) bile salts. The results show the existence of break points in the plot of delta T/k vs molality at 0.018, 0.013, and 0.007 m, respectively, in good agreement with previous published critical micelle concentration values. Above the break point bile salts form aggregates with average aggregation numbers of 2.59 +/- 0.12 (NaTC), 5.82 +/- 0.04 (NaDC), and 5.42 +/- 0.47 (NaTDC). Fractions of bound counterions are also deduced, being close to 0.3 for the three bile salts studied. This indicates that only one counterion is bound for every three monomers in the aggregate. The different structural models published for the bile salt aggregates are discussed.

  4. Technical bases for the salt processing cell dilution strategy for the low nitrite process

    SciTech Connect

    Young, S.R.

    1992-10-22

    This document recommends an interim dilution strategy for the low nitrite precipitate hydrolysis process. A minimum carbon dioxide purge rate of 27 scan during feeding and for 15 minutes after feeding and a maximum precipitate slurry feed rate of 36 gpm are recommended. These recommendations provide an interim dilution strategy that will provide for the start of cold chemical runs and until additional offgas data is collected from the PHEF (Precipitate Hydrolysis Experimental Facility).

  5. [Determination of Chloride Salt Solution by NIR Spectroscopy].

    PubMed

    Zhang, Bin; Chen, Jian-hong; Jiao, Ming-xing

    2015-07-01

    Determination of chloride salt solution by near infrared spectrum plays a very important role in Biomedicine. The near infrared spectrum analysis of Sodium chloride, potassium chloride, calcium chloride aqueous solution shows that the concentration change of chloride salt can affect hydrogen bond, resulting in the variation of near infrared spectrum of water. The temperature influence on NIR spectrum has been decreased by choosing reasonable wavelength range and the wavelength where the temperature effects are zero (isosbestic point). Chlorine salt prediction model was established based on partial least squares method and used for predicting the concentration of the chlorine ion. The impact on near infrared spectrum of the cation ionic radius, the number of ionic charge, the complex effect of ionic in water has also discussed in this article and the reason of every factor are analysed. Experimental results show that the temperature and concentration will affect the near-infrared spectrum of the solution, It is found that the effect of temperature plays the dominant role at low concentrations of chlorine salt; rather, the ionic dominates at high concentration. Chloride complexes are formed in aqueous solution, It has an effect on hydrogen bond of water combining with the cations in chlorine salt solution, Comparing different chloride solutions at the same concentration, the destruction effects of chloride complexes and catnions on the hydrogen bond of water increases in the sequences: CaCl2 >NaCl>KC. The modeling result shows that the determination coefficients (R2) = 99.97%, the root mean square error of cross validation (RM- SECV) = 4.51, and the residual prediction deviation (RPD) = 62.7, it meets the daily requirements of biochemical detection accuracy.

  6. Properties of alkali-halide salt solutions about polarizable nanoparticle solutes for different ion models.

    PubMed

    Wynveen, Aaron; Bresme, Fernando

    2010-10-14

    We investigate the distributions of various salts about large hydrophobic polarizable solutes in aqueous electrolyte solutions. The solutes are modeled as nanometer-sized cylindrical objects, a scale relevant to biomolecules and nanomaterials, and particularly high aspect ratio nanoparticles. Interactions, including image charge forces arising from the finite polarizability of the solute, between explicit solvent/ions and the solute are computed explicitly using a molecular dynamics simulation methodology we have recently introduced. Comparisons are made between several salt species and different models of the force fields for each ionic component of the salt. We find evidence that both small cations, Li(+), and large anions, I(-), adsorb at hydrophobic interfaces. Our results indicate that the ion structure about the solute is strongly dependent on the force field investigated, suggesting that ion selectivity is quite sensitive to the respective parameters defining the ion's size and binding energy as well as to the polarizability of the solute.

  7. 21 CFR 864.2875 - Balanced salt solutions or formulations.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Balanced salt solutions or formulations. 864.2875 Section 864.2875 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Cell And Tissue Culture Products §...

  8. Boiling characteristics of dilute polymer solutions and implications for the suppression of vapor explosions

    SciTech Connect

    Bang, K.H.; Kim, M.H.

    1995-09-01

    Quenching experiments of hot solid spheres in dilute aqueous solutions of polyethylene oxide polymer have been conducted for the purpose of investigating the physical mechanisms of the suppression of vapor explosions in this polymer solutions. Two spheres of 22.2mm and 9.5mm-diameter were tested in the polymer solutions of various concentrations at 30{degrees}C. Minimum film boiling temperature ({Delta}T{sub MFB}) in this highly-subcooled liquid rapidly decreased from over 700{degrees}c for pure water to about 150{degrees}C as the polymer concentration was increased up to 300ppm for 22.2mm sphere, and it decreased to 350{degrees}C for 9.5mm sphere. This rapid reduction of minimum film boiling temperature in the PEO aqueous solutions can explain its ability of the suppression of spontaneous vapor explosions. The ability of suppression of vapor explosions by dilute polyethylene oxide solutions against an external trigger pressure was tested by dropping molten tin into the polymer solutions at 25{degrees}C. It was observed that in 50ppm solutions more mass fragmented than in pure water, but produced weaker explosion pressures. The explosion was completely suppressed in 300ppm solutions with the external trigger. The debris size distributions of fine fragments smaller than 0.7mm were shown almost identical regardless of the polymer concentrations.

  9. Dilution Confusion: Conventions for Defining a Dilution

    ERIC Educational Resources Information Center

    Fishel, Laurence A.

    2010-01-01

    Two conventions for preparing dilutions are used in clinical laboratories. The first convention defines an "a:b" dilution as "a" volumes of solution A plus "b" volumes of solution B. The second convention defines an "a:b" dilution as "a" volumes of solution A diluted into a final volume of "b". Use of the incorrect dilution convention could affect…

  10. Dilution Confusion: Conventions for Defining a Dilution

    ERIC Educational Resources Information Center

    Fishel, Laurence A.

    2010-01-01

    Two conventions for preparing dilutions are used in clinical laboratories. The first convention defines an "a:b" dilution as "a" volumes of solution A plus "b" volumes of solution B. The second convention defines an "a:b" dilution as "a" volumes of solution A diluted into a final volume of "b". Use of the incorrect dilution convention could affect…

  11. The cluster structure of dilute aqueous-alcoholic solutions and molecular light scattering in them

    NASA Astrophysics Data System (ADS)

    Malomuzh, N. P.; Slinchak, E. L.

    2007-11-01

    The structures, equations of state, and character of fluctuations of dilute water-glycerol solutions are discussed. Two or three glycerol and about ten water molecules were found to form a fairly stable molecular complex. We call this complex elementary cluster (pseudoparticle). In a certain region of state parameters, the system could be considered a solution of pseudoparticles (clusters). Its properties were modeled by the van der Waals equation. The character of interactions between clusters was analyzed. An anomalous increase in concentration and molecular light scattering fluctuations was caused by the approach to the solution “pseudospinodal.” The experimental data were found to be in quite satisfactory agreement with theoretical estimates.

  12. Pretreatment of rice straw using a butanone or an acetaldehyde dilute solution explosion for producing ethanol.

    PubMed

    Zhang, Jian; Zhang, Wen-Xue; Yang, Jian; Liu, Yue-Hong; Zhong, Xia; Wu, Zheng-Yun; Kida, Kenji; Deng, Yu

    2012-04-01

    Ethanol conversion from rice straw using butanone and acetaldehyde dilute solution explosions was evaluated based on the optimization of pure water explosion. To decrease residual inhibitor content, the exploded slurry was dried and investigated at different temperature. Using a 0.9-mol/L butanone solution explosion, with the explosion pressure set at 3.1 MPa, the residence time at 7 min, the dried rice straw-to-water ratio at 1:3 (w/w), and the exploded slurry drying temperuture at 90 °C for 8 h, the yields of total sugar, glucose, and xylose were 85%, 88%, 82% (w/w), respectively, and the ethanol productivity was 26.0 g/100 g rice straw dry matter. Moreover, 0.5-mol/L acetaldehyde dilute solution explosion improved the efficiency of enzymatic hydrolysis (EH) and simultaneous saccharification and co-fermentation (SSCF), and the residual inhibitors had negligible effects on EH and SSCF after detoxification by drying. The results suggested that compared with pure water explosions, the use of butanone and of acetaldehyde dilute solution explosions lowered the explosive temperature and improved the sugar yield, although relative crystallinity of the rice straw dry matter was increased after the explosion.

  13. Long-term stability study of clofarabine injection concentrate and diluted clofarabine infusion solutions.

    PubMed

    Kaiser, Jeanette; Krämer, Irene

    2012-06-01

    The aim of this study was to investigate the physicochemical stability of clofarabine (CAFdA) injection concentrate and ready-to-use CAFdA infusion solutions over a prolonged period of 28 days. To determine the stability of CAFdA infusion solutions, the injection concentrate (Evoltra®, 1 mg/mL, Genzyme) was diluted either with 0.9% sodium chloride or 5% glucose infusion solution. The resulting concentrations of 0.2 mg/mL or 0.6 mg/mL, respectively, were chosen to represent the lower and upper limit of the ordinary concentration range. Test solutions were stored under refrigeration (2-8°C) or at room temperature either light protected or exposed to light. CAFdA concentrations and pH values were determined at different time intervals throughout a 28-day storage period. Compatibility of diluted CAFdA infusion solutions (0.1-0.4 mg/mL) with different container materials (polyvinyl chloride (PVC), glass, and polypropylene/polyethylene (PP/PE)) was tested over a 48-h storage period. CAFdA concentrations were measured by a stability-indicating reversed phase high-performance liquid chromatography (HPLC) assay with ultraviolet detection. CAFdA injection concentrate and CAFdA infusion solutions remained physicochemically stable (>90% CAFdA) for 4 weeks. Results are independent of storage conditions, drug concentrations (0.2, 0.6, and 1.0 mg/mL) and diluents (0.9% sodium chloride, 5% glucose infusion solution). Adsorption of CAFdA to container material can be excluded. CAFdA injection concentrate and diluted infusion solutions in commonly used vehicles are stable for at least 28 days either refrigerated or at room temperature. Physicochemical stability favors pharmacy-based centralized preparation. Due to microbiological reasons, strict aseptic handling and storage of the products under refrigeration is recommended.

  14. Taste does not determine daily intake of dilute sugar solutions in mice

    PubMed Central

    Beltran, F.; Benton, L.; Cheng, S.; Gieseke, J.; Gillman, J.; Spain, H. N.

    2010-01-01

    When a rodent licks a sweet-tasting solution, taste circuits in the central nervous system that facilitate stimulus identification, motivate intake, and prepare the body for digestion are activated. Here, we asked whether taste also determines daily intake of sugar solutions in C57BL/6 mice. We tested several dilute concentrations of glucose (167, 250, and 333 mM) and fructose (167, 250, and 333 mM). In addition, we tested saccharin (38 mM), alone and in binary mixture with each of the sugar concentrations, to manipulate sweet taste intensity while holding caloric value constant. In experiment 1, we measured taste responsiveness to the sweetener solutions in two ways: chorda tympani nerve responses and short-term lick tests. For both measures, the mice exhibited the following relative magnitude of responsiveness: binary mixtures > saccharin > individual sugars. In experiment 2, we asked whether the taste measures reliably predicted daily intake of the sweetener solutions. No such relationship was observed. The glucose solutions elicited weak taste responses but high daily intakes, whereas the fructose solutions elicited weak taste responses and low daily intakes. On the other hand, the saccharin + glucose solutions elicited strong taste responses and high daily intakes, while the saccharin + fructose solutions elicited strong taste responses but low daily intakes. Overall, we found that 1) daily intake of the sweetener solutions varied independently of the magnitude of the taste responses and 2) the solutions containing glucose stimulated substantially higher daily intakes than did the solutions containing isomolar concentrations of fructose. Given prior work demonstrating greater postoral stimulation of feeding by glucose than fructose, we propose that the magnitude of postoral nutritive stimulation plays a more important role than does taste in determining daily intake of dilute sugar solutions. PMID:20702804

  15. Modification of FGD gypsum in hydrothermal mixed salt solution.

    PubMed

    Wu, Xiao-Qin; Wu, Zhong-Biao

    2006-01-01

    A novel utilization way of the sludge from wet calcium-based flue gas desulfurization (FGD) processes has been developed in this paper. This study focused on the conversion of the FGD gypsum into alpha-hemihydrate calcium sulfate by a hydrothermal salt solution method at atmospheric pressure. Experimental study has been carried out in a batch reactor. Qualitative and quantitative analyses were made by DSC/TG thermal analysis, SEM, XRD, metalloscope and chemical analysis. The experimental results showed that the modification of FGD gypsum was controlled by the dissolution and recrystallization mechanisms. With the introduction of FGD gypsum the salt solution was supersaturated, then crystal nucleus of alpha-hemihydrate calcium sulfate were produced in the solution. With the submicroscopic structure of FGD gypsum crystal changed, the crystal nucleus grew up into alpha-hemihydrate calcium sulfate crystals. Thus, the modification of FGD gypsum was fulfilled.

  16. Removal of transition metals from dilute aqueous solution by carboxylic acid group containing absorbent polymers

    USDA-ARS?s Scientific Manuscript database

    A new carboxylic acid group containing resin with cation exchange capacity, 12.67 meq/g has been used to remove Cu2+, Co2+ and Ni2+ ions from dilute aqueous solution. The resin has Cu2+, Co2+ and Ni2+ removal capacity, 216 mg/g, 154 mg/g and 180 mg/g, respectively. The selectivity of the resin to ...

  17. Studies of 6Li-NMR properties in different salt solutions in low magnetic fields

    NASA Astrophysics Data System (ADS)

    Gordji-Nejad, A.; Colell, J.; Glöggler, S.; Blümich, B.; Appelt, S.

    2012-01-01

    In this article we report the longitudinal relaxation times ( T1) of various 6Li salts ( 6LiI, 6LiCl and 6LiNO 3) in D 2O and H 2O, measured in low magnetic fields ( B0 = 3.5 mT). This investigation serves the purpose of clarifying the relaxation behavior of different 6Li solutions and different concentrations. The measurement were undertaken to establish a framework for future applications of hyperpolarized 6Li in medical imaging, biological studies and investigations of lithium ion batteries. Time will pass during the transport of hyperpolarized lithium ions to the sample, which leads to a polarization loss. In order to store polarization as long as possible, it is necessary to examine which 6Li salt solution has the longest relaxation time T1. Longitudinal relaxation times of 6Li salts in D 2O and H 2O were investigated as a function of concentration and the most extended T1 was found for 6LiI in D 2O and H 2O. In agreement with the theory the relaxation time T1 of all 6Li salts increase with decreasing concentration. In the case of 6LiI in H 2O an inverse behavior was observed. We assume that the prolonged T1 times occur due to formation of 6LiOH upon the solution of 6LiI in H 2O, which settles as a precipitate. By diluting the solution, the precipitate continuously dissolves and approaches T1 of 6LiOH ( T1 ˜ 28 s), leading to a shorter T1 relaxation time.

  18. Transport in very dilute solutions of 3He in superfluid 4He

    NASA Astrophysics Data System (ADS)

    Baym, Gordon; Beck, D. H.; Pethick, C. J.

    2013-07-01

    Motivated by a proposed experimental search for the electric dipole moment of the neutron (nEDM) utilizing neutron-3He capture in a dilute solution of 3He in superfluid 4He, we derive the transport properties of dilute solutions in the regime where the 3He are classically distributed and rapid 3He-3He scatterings keep the 3He in equilibrium. Our microscopic framework takes into account phonon-phonon, phonon-3He, and 3He-3He scatterings. We then apply these calculations to measurements by Rosenbaum [J. Low Temp. Phys.JLTPAC0022-229110.1007/BF00655864 16, 131 (1974)] and by Lamoreaux [Europhys. Lett.EULEEJ0295-507510.1209/epl/i2002-00408-4 58, 718 (2002)] of dilute solutions in the presence of a heat flow. We find satisfactory agreement of theory with the data, serving to confirm our understanding of the microscopics of the helium in the future nEDM experiment.

  19. Photoionization of Sodium Salt Solutions in a Liquid Jet

    SciTech Connect

    Grieves, G. A.; Petrik, Nikolay G.; Herring-Captain, J.; Olanrewaju, B.; Aleksandrov, A.; Tonkyn, Russell G.; Barlow, Stephan E.; Kimmel, Gregory A.; Orlando, Thomas M.

    2008-06-05

    A liquid microjet was employed to examine the gas/liquid interface of aqueous sodium halide (Na+X-, X=Cl, Br, I) salt solutions. Laser excitation at 193 nm produced and removed cations of the form H+(H2O)n and Na+(H2O)m from liquid jet surfaces containing either NaCl, NaBr or NaI. The protonated water cluster yield varied inversely with increasing salt concentration, while the solvated sodium ion cluster yield varied by anion type. The distribution of H+(H2O)n at low salt concentration is identical to that observed from low-energy electron irradiated amorphous ice and the production of these clusters can be accounted for using a localized ionization/Coulomb expulsion model. Production of Na+(H2O)m is not accounted for by this model but requires ionization of solvation shell waters and a contact ion/Coulomb expulsion mechanism. The reduced yields of Na+(H2O)m from high concentration (10-2 and 10-1 M) NaBr and NaI solutions indicate a propensity for Br- and I- at the solution surfaces and interfaces. This is supported by the observation of multiphoton induced production and desorption of Br+ and I+ from the 10-2 and 10-1 M solution surfaces.

  20. Centrifugal separation for miscible solutions: Fundamentals and applications to separation of molten salt nuclear material

    SciTech Connect

    Ning Li; Camassa, R.; Ecke, R.E.

    1995-10-01

    The authors report on the physical separation of dilute solutions using centrifugal techniques. They use numerical simulations of the diffusion and sedimentation dynamics of centrifugation to model the approach to an equilibrium concentration profile. They verify experimentally the equilibrium profiles for aqueous solutions of different salts under rotation at 25000 rpm corresponding to centrifugal accelerations of about 57,000 g and 75,000 g in two different commercial centrifuges. These measurements provide ratios of sedimentation and diffusion coefficients. The authors show experimental results for the dynamics of separation that confirm the predictions of the theoretical model. They also measure the mass diffusion coefficient for several solutions. Although the relaxation to equilibrium is long, they have determined a method for efficiently extracting enriched components from a ternary mixture based on fast dynamics at early times. These dynamics are modeled in numerical simulations with realistic fluid parameters. Based on these studies the authors show that a multistage centrifugal separation process could provide efficient physical separation of actinides and fission products from a molten-salt solution in proposed transmutation/energy-production systems. The authors consider technical issues in the design of such a separation system.

  1. THE INACTIVATION OF DILUTE SOLUTIONS OF CRYSTALLINE TRYPSIN BY X-RADIATION

    PubMed Central

    McDonald, Margaret R.

    1954-01-01

    The activity of dilute solutions of crystalline trypsin is destroyed by x-rays. The inactivation is an exponential function of the radiation dose. The reaction yield of inactivation is independent of the intensity at which the radiation is delivered or the quality of the x-rays. The reaction yield increases with increasing concentration of trypsin, varying from 0.06 to 0.7 micromoles per liter per 1000 r for trypsin solutions ranging from 1 x 10–7 to 2 x 10–4 M. PMID:13192318

  2. Capillary electrophoretic separation of DNA restriction fragments using dilute polymer solutions

    SciTech Connect

    Braun, B.; Blanch, W.; Prausnitz, J.M.

    1997-02-01

    Because the mechanism of DNA separation in capillary electrophoresis is not well understood, selection of polymers is a {open_quotes}trial-and-error{close_quotes} procedure. We investigated dilute-solution DNA separations by capillary electrophoresis using solutions of four polymers that differ in size, shape and stiffness. Hydroxyethylcellulose of high molecular weight provides excellent separation of large DNA fragments (2027 bp - 23130 bp). Polyvinylpyrrolidone separates DNA from 72 bp to 23 kbp and star-(polyethylene oxide), like linear poly (ethylene oxide), provides separation of fragments up to 1353 bp.

  3. Economic evaluation of preconcentration in production of ethanol from dilute sugar solutions.

    PubMed

    Zacchi, G; Axelsson, A

    1989-06-20

    The economic feasibility of preconcentrating dilute sugar solutions prior to fermentation is investigated. Two methods, evaporation and reverse osmosis, are compared. A computer program to determine the optimal preconcentration conditions for glucose solutions of 1.5-16 wt% has been developed. It was used to compute the fractional cost for labor and maintenance, preconcentration, fermentation, and distillation. Preconcentration with evaporation resulted in a higher total cost, compared with no preconcentration, for all cases studied, although a six-effect unit was used. Reverse osmosis was found to be economically feasible for preconcentration to about 5-10 wt % depending on the concentration of the feed.

  4. Fabrication of CPA Salt Pill with Circulating Solution Method

    NASA Astrophysics Data System (ADS)

    Hoshino, A.; Tokoi, K.; Ishisaki, Y.; Shinozaki, K.; McCammon, D.

    2008-05-01

    We report results on fabrication of a Chromium Potassium Alum (CPA) salt pill. CPA is a typical paramagnetic salt used as refrigerant of Adiabatic Demagnetization Refrigerator (ADR) because of its low Curie point, 4 11 mK. We made an test model of CPA salt pill by fast crystallizing method, namely circulating solution between 36°C and 15°C. The crystallizing rate was 0.5 g h-1, and 40 g of CPA crystal was obtained inside a stainless steel cylinder equipped with 160 copper wires. The cooling test was operated utilizing a commercial ADR system. We attached three thermometers and four heaters to the salt pill, in order to measure thermal conductance among different parts of the pill. It is confirmed that our salt pill was cooled down from B/ T=4 T/2 K to 64 mK at zero magnetic field. We suspect the cause of limiting the cooling temperature in the present level to be the dehydration of CPA, non-uniformity of magnetic field, and stainless steel of the pill which has large heat capacity below 0.1 K.

  5. NEUTRON RADIOGRAPHY MEASUREMENT OF SALT SOLUTION ABSORPTION IN MORTAR.

    PubMed

    Lucero, Catherine L; Spragg, Robert P; Bentz, Dale P; Hussey, Daniel S; Jacobson, David L; Weiss, W Jason

    2017-01-01

    Some concrete pavements in the US have recently exhibited premature joint deterioration. It is hypothesized that one component of this damage can be attributed to a reaction that occurs when salt-laden water is absorbed in the concrete and reacts with the matrix. This study examines the absorption of CaCl2 solution in mortar via neutron imaging. Mortar specimens were prepared with water to cement ratios, (w/c), of 0.36, 0.42 and 0.50 by mass and exposed to chloride solutions with concentrations ranging from 0 % to 29.8 % by mass. Depth of fluid penetration and moisture content along the specimen length were determined for 96 h after exposure. At high salt concentration (29.8 %), the sorption rate decreased by over 80 % in all samples. Along with changes in surface tension and viscosity, CaCl2 reacts with the cement paste to produce products (Friedel's salt, Kuzel's salt, or calcium oxychloride) that block pores and reduce absorption.

  6. An overview of the performance of the COSMO-RS approach in predicting the activity coefficients of molecular solutes in ionic liquids and derived properties at infinite dilution.

    PubMed

    Paduszyński, Kamil

    2017-05-17

    This paper reports a comprehensive evaluation of the conductor-like screening model for real solvents (COSMO-RS) in predicting infinite dilution activity coefficients (γ(∞)) of molecular solutes in ionic liquids (ILs). In particular, comparative analysis of two quantum chemical levels of calculations used in the COSMO part of COSMO-RS, namely, TZVP-COSMO and TZVPD-FINE, is presented and discussed. The final assessment of the model performance is established based on a comparison of its predictions with the experimental data pool consisting of 41 868 data points extracted form 182 references, covering 233 ILs (including salts belonging to 12 different cationic families) and 150 molecular solutes (including a great variety of non-polar, polar and self-associating organic compounds and water) combined with 8554 distinct binary systems. The impact of the chemical family of both IL and molecular solute on the accuracy of the COSMO-RS predictions is analyzed in terms of both quantitative and qualitative measures. Relevant thermodynamic properties derived from γ(∞), namely, infinite dilution partial excess enthalpy of mixing and infinite dilution selectivity are considered and their values obtained from experimental and COSMO-RS predicted γ(∞) data are confronted. Finally, the impact of the molecular conformation of cations/anions/solutes on the quality of predictions is demonstrated based on some representative systems.

  7. Effective potentials of Hofmeister salts in aqueous solution

    NASA Astrophysics Data System (ADS)

    Marquina-Carmona, M. A.; Hernández-Contreras, M.

    2017-01-01

    The effective pair interaction potentials of monovalent halide anions and alkali cations in bulk solution of a molecular solvent model were determined using atomistic simulations. These properties result from the microstructure of the ionic liquid which is the main ingredient in the hypernetted chain approach of liquid theory. We used an optimized set of Lennard-Jones parameters that are thermodynamically reliable for bulk phases of the Hofmeister salts.

  8. Modeling Sucrose Hydrolysis in Dilute Sulfuric Acid Solutions at Pretreatment Conditions for Lignocellulosic Biomass

    SciTech Connect

    Bower, S.; Wickramasinghe, R.; Nagle, N. J.; Schell, D. J.

    2008-01-01

    Agricultural and herbaceous feedstocks may contain appreciable levels of sucrose. The goal of this study was to evaluate the survivability of sucrose and its hydrolysis products, fructose and glucose, during dilute sulfuric acid processing at conditions typically used to pretreat lignocellulose biomass. Solutions containing 25 g/l sucrose with 0.1-2.0% (w/w) sulfuric acid concentrations were treated at temperatures of 160-200 C for 3-12 min. Sucrose was observed to completely hydrolyze at all treatment conditions. However, appreciable concentrations of fructose and glucose were detected and glucose was found to be significantly more stable than fructose. Different mathematical approaches were used to fit the kinetic parameters for acid-catalyzed thermal degradation of these sugars. Since both sugars may survive dilute acid pretreatment, they could provide an additional carbon source for production of ethanol and other bio-based products.

  9. Recovery of uranium from dilute solution using liquid emulsion membrane system

    SciTech Connect

    Mukhopadhyay, S.; Ghosh, S.K.; Juvekar, V.A.

    2008-07-01

    The liquid emulsion membrane (LEM) technique has great potential for application in the nuclear industry for large interfacial area, low consumption of organics, and high recovery from dilute streams. A LEM system composed DEHPA-kerosene-SPAN80-HNO{sub 3} has been developed for recovery of uranium from dilute nitrate solution, which gives 98% extraction and 88% stripping in a single stage. An attempt has been made to understand the mechanism of the LEM process, in which phenomena like per-traction, occlusion, swelling, and leakage occur simultaneously. The effect of various parameters on these phenomena has been described with a mathematical model, which is able to explain the experimental findings. (authors)

  10. The 'Memory of Water': an almost deciphered enigma. Dissipative structures in extremely dilute aqueous solutions.

    PubMed

    Elia, V; Napoli, E; Germano, R

    2007-07-01

    In the last decade, we have investigated from the physicochemical point of view, whether water prepared by the procedures of homeopathic medicine (leading inexorably to systems without any molecule different from the solvent) results in water different from the initial water? The answer, unexpectedly, but strongly supported by many experimental results is positive. We used well-established physicochemical techniques: flux calorimetry, conductometry, pHmetry and galvanic cell electrodes potential. Unexpectedly the physicochemical parameters evolve in time. The water solvent exhibits large changes in measurable physicochemical properties as a function of its history, the solute previously dissolved, and time. In particular we found evidence of two new phenomena, both totally unpredicted, in homeopathic dilutions: the presence of a maximum in the measured physicochemical parameters vs sample age, and their dependence on the volume in which the dilution is stored. These new experimental results strongly suggest the presence of an extended and 'ordered' dynamics involving liquid water molecules.

  11. The chemistry of drying an aqueous solution of salts.

    PubMed

    Takenaka, Norimichi; Takayama, Kayoko; Ojiro, Naofumi; Shimazaki, Wataru; Ohira, Kingo; Soda, Hiroyuki; Suzue, Takahiko; Sadanaga, Yasuhiro; Bandow, Hiroshi; Maeda, Yasuaki

    2009-11-05

    The fate of salts in drying aqueous solution was investigated. In the drying of acidic solutions, weak acid ions and chloride ions combine with protons and evaporate, depending on the proton concentration. In the drying of alkaline solutions, weak acid ions evaporate or remain as salts depending on the ratio of the concentrations of excess nonvolatile cations (the difference between concentrations of nonvolatile cation and nonvolatile anion) to volatile anions defined as DeltaCA. Under neutral and alkaline conditions, the fate of nitrite depends not only on DeltaCA but also on the drying speed. Nitrite is converted to N2, which is formed by reacting nitrite with ammonium (denitrification), NO and NO2, HONO and salts. In urban areas, nitrite and ammonium can appear in high concentrations in dew. HONO in the atmosphere affects the ozone concentration, but dew formation decreases the concentration of HONO. If chemical denitrification occurs, nitrogen species will decrease in the environment, and as a result, the ozone concentration could decrease. Ozone levels show an ozone depression when dew formed, and a Box model simulation showed an ozone depression by decreasing HONO levels.

  12. Formulation and make-up of simulate dilute water, low ionic content aqueous solution

    SciTech Connect

    Gdowski, G.

    1997-04-04

    This procedure describes the formulation and make-up of Simulated Dilute Water (SOW), a low-ionic-content water to be used for Activity E-20-50, Long-Term Corrosion Studies. This water has an ionic content which is nominally a factor of ten higher than that of representative waters at or near Yucca Mountain. Representative waters were chosen as J-13 well water [Harrar, 1990] and perched water at Yucca Mountain [Glassley, 1996]. J-13 well water is obtained from ground water that is in contact with the Topopah Spring tuff, which is the repository horizon rock. The perched water is located in the Topopah Spring tuff, but below the repository horizon and above the water table. A nominal times ten higher ionic content was chosen to simulate the effect of ionic concentrating due to elevated temperature water flowing through fractures where salts and minerals have been deposited due to evaporation and boiling.

  13. SODIUM ALUMINOSILICATE FOULING AND CLEANING OF DECONTAMINATED SALT SOLUTION COALESCERS

    SciTech Connect

    Poirier, M; Thomas Peters, T; Fernando Fondeur, F; Samuel Fink, S

    2008-10-28

    During initial non-radioactive operations at the Modular Caustic Side Solvent Extraction Unit (MCU), the pressure drop across the decontaminated salt solution coalescer reached {approx}10 psi while processing {approx}1250 gallons of salt solution, indicating possible fouling or plugging of the coalescer. An analysis of the feed solution and the 'plugged coalescer' concluded that the plugging was due to sodium aluminosilicate solids. MCU personnel requested Savannah River National Laboratory (SRNL) to investigate the formation of the sodium aluminosilicate solids (NAS) and the impact of the solids on the decontaminated salt solution coalescer. Researchers performed developmental testing of the cleaning protocols with a bench-scale coalescer container 1-inch long segments of a new coalescer element fouled using simulant solution. In addition, the authors obtained a 'plugged' Decontaminated Salt Solution coalescer from non-radioactive testing in the MCU and cleaned it according to the proposed cleaning procedure. Conclusions from this testing include the following: (1) Testing with the bench-scale coalescer showed an increase in pressure drop from solid particles, but the increase was not as large as observed at MCU. (2) Cleaning the bench-scale coalescer with nitric acid reduced the pressure drop and removed a large amount of solid particles (11 g of bayerite if all aluminum is present in that form or 23 g of sodium aluminosilicate if all silicon is present in that form). (3) Based on analysis of the cleaning solutions from bench-scale test, the 'dirt capacity' of a 40 inch coalescer for the NAS solids tested is calculated as 450-950 grams. (4) Cleaning the full-scale coalescer with nitric acid reduced the pressure drop and removed a large amount of solid particles (60 g of aluminum and 5 g of silicon). (5) Piping holdup in the full-scale coalescer system caused the pH to differ from the target value. Comparable hold-up in the facility could lead to less effective

  14. Scaling Equations for a Biopolymer in Salt Solution

    NASA Astrophysics Data System (ADS)

    Geissler, Erik; Hecht, Anne-Marie; Horkay, Ferenc

    2007-12-01

    The effect of the simultaneous presence of monovalent and divalent cations on the thermodynamics of polyelectrolyte solutions is an incompletely solved problem. In physiological conditions, combinations of these ions affect structure formation in biopolymer systems. Dynamic light scattering measurements of the collective diffusion coefficient D and the osmotic compressibility of semidilute hyaluronan solutions containing different ratios of sodium and calcium ions are compared with simple polyelectrolyte models. Scaling relationships are proposed in terms of polymer concentration and ionic strength J of the added salt. Differences in the effects of sodium and calcium ions are found to be expressed only through J.

  15. Tenecteplase: stability and bioactivity of thawed or diluted solutions used in peripheral thrombolysis.

    PubMed

    Semba, Charles P; Weck, Suzanne; Razavi, Mahmood K; Tuomi, Lisa; Patapoff, Thomas

    2003-04-01

    Tenecteplase (TNK; TNKase) is a third-generation plasminogen activator approved for acute myocardial infarction with an enhanced safety profile compared to alteplase. The stability and bioactivity of reconstituted frozen/thawed and diluted tenecteplase solutions used in noncoronary peripheral thrombolysis was determined. Lyophilized TNK was freshly reconstituted in sterile water (5 mg/mL) and used as control. In freeze/thaw studies, reconstituted TNK aliquots were stored frozen for 4 weeks at -20 degrees C, thawed at ambient temperature, and assayed with and without an additional freeze/thaw cycle. Additional freshly reconstituted TNK aliquots were assayed after six freeze/thaw cycles when frozen at two separate temperatures (-20 degrees and -70 degrees C) and thawed at 2-8 degrees C or ambient temperature. In dilution studies, reconstituted TNK was diluted in 500-mL commercially available normal saline solution bags to concentrations of 0.01, 0.02, and 0.05 mg/mL. Samples were assayed after 0, 8, and 24 hours at ambient temperature. Optical clarity, pH, protein concentration, particle counts, and in-vitro clot-lysis assays were performed. Protein monomer (%), single-chain protein (%), and particle counts were performed in freeze/thaw studies. Frozen/thawed TNK aliquots met all specifications as freshly reconstituted product. For dilution studies (0.01, 0.02, and 0.05 mg/mL), the recovered protein retained 83%-100% bioactivity after 24 hours. The recovered protein rates over the course of 24 hours (relative to target concentration) were 70%-75%, 80%-85%, and 94%-95% at 0.01, 0.02, and 0.05 mg/mL, respectively. Assayed solutions were clear/colorless at all concentrations and time points. TNK is fully active after reconstitution and freezing/thawing. TNK dilutions used in clinical practice (0.01-0.05 mg/mL) demonstrated retention of biologic activity at 24 hours without precipitates.

  16. Geotechnical factors and guidelines for storage of compressed air in solution-mined salt cavities

    NASA Astrophysics Data System (ADS)

    Allen, R. D.; Doherty, T. J.; Thoms, R. L.

    1982-05-01

    The state of knowledge about utilization of solution mined salt cavities for CAES including laboratory experiments, numerical modeling, field characterization, solution mining experience, and operating parameters is outlined. Topics evaluated include: cavern geometry and size; long term creep and creep rupture of rock salt; effects of pressure and temperature loading rates; low frequency fatigue; progressive deterioration of salt fabric with possible air penetration; cavern monitoring methods; and salt properties at nonambient conditions. The only CAES operational facility in the world uses two solution mined salt cavern for air storage and is operating successfully. Stability critera for solution mined salt caverns.

  17. Precipitation of oppositely charged polyelectrolytes in salt solutions.

    PubMed

    Kudlay, Alexander; Olvera de la Cruz, Monica

    2004-01-01

    We study phase separation in symmetric solutions of weakly charged flexible chains of opposite sign. Precipitation is caused by effective attractions due to charge fluctuations and by short-range attractions between monomers. The contribution from charge fluctuations is computed within the random phase approximation (RPA), which takes into account the connectivity of charges in the polyions. The impenetrability of the ions is accounted for by using a modified Coulomb potential in the RPA. In good solvent conditions the precipitate monotonically swells and eventually dissolves upon addition of salt. However, near the theta-solvent condition, but still in the good solvent, the precipitate can be stable at any salt concentration. Moreover, the density of the precipitate after initial decrease can increase with addition of salt. This effect is a result of redistribution of salt between the precipitate and the supernatant, which is due to an interplay of electrostatic and hardcore interactions. For not too weakly charged polyions the precipitate properties become strongly dependent on temperature even in good solvent conditions.

  18. Dilute solution properties of canary seed (Phalaris canariensis) starch in comparison to wheat starch.

    PubMed

    Irani, Mahdi; Razavi, Seyed M A; Abdel-Aal, El-Sayed M; Hucl, Pierre; Patterson, Carol Ann

    2016-06-01

    Dilute solution properties of an unknown starch are important to understand its performance and applications in food and non-food industries. In this paper, rheological and molecular properties (intrinsic viscosity, molecular weight, shape factor, voluminosity, conformation and coil overlap parameters) of the starches from two hairless canary seed varieties (CO5041 & CDC Maria) developed for food use were evaluated in the dilute regime (Starch dispersions in DMSO (0.5g/dl)) and compared with wheat starch (WS). The results showed that Higiro model is the best among five applied models for intrinsic viscosity determination of canary seed starch (CSS) and WS on the basis of coefficient of determination (R(2)) and root mean square error (RMSE). WS sample showed higher intrinsic viscosity value (1.670dl/g) in comparison to CSS samples (1.325-1.397dl/g). Berry number and the slope of master curve demonstrated that CSS and WS samples were in dilute domain without entanglement occurrence. The shape factor suggested spherical and ellipsoidal structure for CO5041 starch and ellipsoidal for CDC Maria starch and WS. The molecular weight, coil radius and coil volume of CSSs were smaller than WS. The behavior and molecular characterization of canary seed starch showed its unique properties compared with wheat starch.

  19. An investigation of the critical liquid-vapor properties of dilute KCl solutions

    USGS Publications Warehouse

    Potter, R.W.; Babcock, R.S.; Czamanske, G.K.

    1976-01-01

    The three parameters that define the critical point, temperature, pressure, and volume have been experimentally determined by means of filling studies in a platinum-lined system for five KCl solutions ranging from 0.006 to 0.568 m. The platinum-lined vessels were used to overcome the problems with corrosion experienced by earlier workers. The critical temperature (tc), pressure (Pc), and volume (Vc) were found to fit the equations {Mathematical expression} from infinite dilution to 1.0 m. ?? 1976 Plenum Publishing Corporation.

  20. The dissolution of quartz in dilute aqueous solutions of organic acids at 25 degree C

    SciTech Connect

    Bennett, P.C.; Melcer, M.E.; Siegel, D.I.; Hassett, J.P. )

    1988-06-01

    The dissolution of quartz in dilute aqueous solutions of organic acids at 25{degree}C and standard pressure was investigated by the batch dissolution method. The bulk dissolution rate of quartz in 20 mmole/Kg citrate solutions at pH 7 was 8 to 10 times faster than that in pure water. After 1750 hours the concentration of dissolved silica in the citrate solution was 167 {mu}mole/Kg compared to 50 {mu}mole/Kg in water and a 20 mmole/Kg solution of acetate at pH 7. Solutions of salicylic, oxalic, and humic acids also accelerated the dissolution of quartz in aqueous solution at pH 7. The rate of dissolution in organic acids decreased sharply with decreasing pH. The possibility of a silica-organic acid complex was investigated using UV-difference spectroscopy. Results suggest that dissolved silica is complexed by citrate, oxalate and pyruvate at pH 7 by an electron-donor acceptor complex, whereas no complexation occurs between silica and acetate, lactate, malonate, or succinate. Three models are proposed for the solution and surface complexation of silica by organic acid which result in the accelerated dissolution and increased solubility of quartz in organic rich water.

  1. The dissolution of quartz in dilute aqueous solutions of organic acids at 25°C

    USGS Publications Warehouse

    Bennett, P.C.; Melcer, M.E.; Siegel, D.I.; Hassett, J.P.

    1988-01-01

    The dissolution of quartz in dilute aqueous solutions of organic acids at 25° and standard pressure was investigated by the batch dissolution method. The bulk dissolution rate of quartz in 20 mmole/Kg citrate solutions at pH 7 was 8 to 10 times faster than that in pure water. After 1750 hours the concentration of dissolved silica in the citrate solution was 167 μmole/Kg compared to 50 μmole/Kg in water and a 20 mmole/Kg solution of acetate at pH 7. Solutions of salicylic, oxalic, and humic acids also accelerated the dissolution of quartz in aqueous solution at pH 7. The rate of dissolution in organic acids decreased sharply with decreasing pH.The possibility of a silica-organic acid complex was investigated using UV-difference spectroscopy. Results suggest that dissolved silica is complexed by citrate, oxalate and pyruvate at pH 7 by an electron-donor acceptor complex, whereas no complexation occurs between silica and acetate, lactate, malonate, or succinate. Three models are proposed for the solution and surface complexation of silica by organic acid anions which result in the accelerated dissolution and increased solubility of quartz in organic rich water.

  2. Characterizing Soy Sauce Moromi Manufactured by High-Salt Dilute-State and Low-Salt Solid-State Fermentation Using Multiphase Analyzing Methods.

    PubMed

    Zhang, Liqiang; Zhou, Rongqing; Cui, Ruiying; Huang, Jun; Wu, Chongde

    2016-10-14

    Present study was to characterize the physiochemical properties, free amino acids (FAAs), volatiles and microbial communities of various moromi, respectively sampled from different stages of high-salt dilute-state (HSDS) and low-salt solid-state (LSSS) fermentation, using multiphase analyzing methods. Phospholipid fatty acids (PLFA) analysis indicated that Gram-positive bacteria were dominant bacteria and fungi were principal microbes. For DGGE analysis, dominant microbes in moromi were mainly fell into Weissella, Tetragenococcus, Candida, Pichia, and Zygosaccharomyces. During fermentation, the dominant microbes shifted from nonhalophilic and less acid-tolerant species to halophilic and acid-tolerant species. Total of 15 FAAs and 44 volatiles were identified in moromi, mainly Glu, Asp, Tyr, and acids, alcohols, esters, aldehydes, respectively. Odor activity values analysis suggested that the final moromi of LSSS fermentation had more complicated odors than that of HSDS fermentation. Conclusively, technological parameters, microbial communities, raw materials and fermentation process may result in the discrepancy of HSDS and LSSS moromi.

  3. Solvent effect induced solute damage in an organic inner salt.

    PubMed

    Shui, Min; Jin, Xiao; Li, Zhongguo; Yang, Junyi; Shi, Guang; Zhang, Xueru; Wang, Yuxiao; Yang, Kun; Wei, Tai-huei; Song, Yinglin

    2010-12-20

    Nonlinear absorption of a newly synthesized organic inner salt Ge-150 dissolved in four different solvents (DMF, DMSO, acetonitrile and acetone) is investigated by the Z-scan technique with both nanosecond and picosecond pulses. When pulse energy surpasses a threshold and pulse-to-pulse separation is shorter than a characteristic time, all the four solutions show absorption weakening induced by cross-pulse effects in the picosecond regime. However, only two of them (Ge-150 dissolved in DMF and DMSO) show this weakening in the nanosecond regime. By conducting a simple verification experiment, we verify this absorption weakening is induced by solute damage related to solvent effect rather than solute migration. A simple theoretical model is proposed to interpret the experimental phenomenon.

  4. Simulation of osmotic pressure in concentrated aqueous salt solutions.

    SciTech Connect

    Luo, Y.; Roux, B.; Univ. of Chicago

    2010-01-01

    Accurate force fields are critical for meaningful simulation studies of highly concentrated electrolytes. The ion models that are widely used in biomolecular simulations do not necessarily reproduce the correct behavior at finite concentrations. In principle, the osmotic pressure is a key thermodynamic property that could be used to test and refine force field parameters for concentrated solutions. Here we describe a novel, simple, and practical method to compute the osmotic pressure directly from molecular dynamics (MD) simulation of concentrated aqueous solutions by introducing an idealized semipermeable membrane. Simple models for Na+, K+, and Cl- are tested and calibrated to accurately reproduce the experimental osmotic pressure at high salt concentration, up to the solubility limit of 4-5 M. The methodology is general and can be extended to any type of solute as well as nonadditive polarizable force fields.

  5. Single chains of strong polyelectrolytes in aqueous solutions at extreme dilution: Conformation and counterion distribution

    NASA Astrophysics Data System (ADS)

    Xu, Guofeng; Luo, Shuangjiang; Yang, Qingbo; Yang, Jingfa; Zhao, Jiang

    2016-10-01

    The molecular conformation of two typical polyelectrolytes, sodium polystyrene sulfonate (NaPSS) and quarternized poly-4-vinylpyridine (QP4VP), was studied in aqueous solutions without salt addition at the single molecular level. By fluorescence correlation spectroscopy, the hydrodynamic radius (Rh) of NaPSS and QP4VP with the molecular weight ranging more than one order of magnitude was measured. The scaling analysis of Rh exhibits scaling exponent of 0.70 and 0.86 for NaPSS and QP4VP in solutions without added salts, respectively, showing the conformation is much more expanded than random coil. Numerical fittings using the model of diffusion of a rod molecule agree with the data well, indicating that the polyelectrolyte chains take the rod-like conformation under the condition without salt addition. Further investigations by determining the electric potential of single PSS- chains using the photon counting histogram technique demonstrate the enhanced counterion adsorption to the charged chain at higher molecular weight.

  6. Solution behaviors and microstructures of PNIPAm-P123-PNIPAm pentablock terpolymers in dilute and concentrated aqueous solutions.

    PubMed

    Lu, Yanping; Chen, Tongquan; Mei, Aixiong; Chen, Tianyou; Ding, Yanwei; Zhang, Xinghong; Xu, Junting; Fan, Zhiqiang; Du, Binyang

    2013-06-07

    The solution behaviors and microstructures of poly(N-isopropylacrylamide)x-poly(ethylene oxide)20-poly(propylene oxide)70-poly(ethylene oxide)20-poly(N-isopropylacrylamide)x (PNIPAmx-PEO20-PPO70-PEO20-PNIPAmx or PNIPAmx-P123-PNIPAmx) pentablock terpolymers with various PNIPAm block lengths in dilute and concentrated aqueous solutions were investigated by micro-differential scanning calorimetry (micro-DSC), static and dynamic light scattering (SLS & DLS), and synchrotron small angle X-ray scattering (SAXS). Two lower critical solution temperatures (LCSTs) were observed for PNIPAmx-P123-PNIPAmx pentablock terpolymers in dilute solutions, which corresponded to LCSTs of PPO and PNIPAm blocks, respectively. The LCST of PPO block shifted from 24.4 °C to 29 °C when the length x of PNIPAm block increased from 10 to 97. The LCST of PNIPAm is around 34.5 °C-35.3 °C and less dependent on the block length x. The PNIPAmx-P123-PNIPAmx pentablock terpolymers formed "associate" structures and micelles with hydrophobic PNIPAm and PPO blocks as cores and soluble PEO blocks as coronas in dilute aqueous solutions at 20 °C and 40 °C, respectively, regardless of the relative lengths of PNIPAm, PPO and PEO blocks. The size of "associate" structures of PNIPAmx-P123-PNIPAmx pentablock terpolymers at 20 °C increased with increasing the length of PNIPAm block. The microstructures of PNIPAmx-P123-PNIPAmx hydrogels formed in concentrated aqueous solutions (40 wt%) were strongly dependent on the environmental temperatures and relative lengths of PNIPAm, PPO and PEO blocks as revealed by SAXS. Increasing the length of PNIPAm block weakened the order structures of PNIPAmx-P123-PNIPAmx hydrogels. The microstructures of PNIPAmx-P123-PNIPAmx hydrogels changed from mixed fcc and hex structures for PNIPAm10-P123-PNIPAm10 to isotropic structure for PNIPAm97-P123-PNIPAm97. Increasing temperature led to the transition from mixed hex and fcc structure to pure hex structure for PNIPAm10-P123-PNIPAm

  7. Ionic contribution to the viscosity of dilute electrolyte solutions: Towards a microscopic theory

    NASA Astrophysics Data System (ADS)

    Chandra, Amalendu; Bagchi, Biman

    2000-08-01

    The concentration dependence of viscosity of an electrolyte solution has remained largely an ill-understood problem of solution chemistry. Here we present a microscopic study of the problem aimed at removing this lacuna. A new microscopic expression for the ionic contribution to the viscosity of an electrolyte solution has been derived which expresses it in terms of the static and dynamic structure factors of the charge and the number densities of the electrolyte solution. This ionic contribution becomes the excess viscosity for extremely dilute solutions. The celebrated expression of Falkenhagen follows exactly from the microscopic expression in the limit of very low ion concentration. The present theory is a self-consistent theory which also includes the concentration dependence of the electrolyte friction on the ions. Numerical results reveal that the viscosity of a solution at finite concentration can be very different from that given by the Falkenhagen expression. The present theory predicts a stronger increase of viscosity with increase of ion concentration, especially for ions of higher valence which is in qualitative agreement with experimental results. The theory suggests that, for viscosity, the molecular nature of the ion-solvent interactions could be important even at very low ion concentration.

  8. Synergistic solubilization of porcine myosin in physiological salt solution by arginine.

    PubMed

    Takai, Eisuke; Yoshizawa, Shunsuke; Ejima, Daisuke; Arakawa, Tsutomu; Shiraki, Kentaro

    2013-11-01

    Myosin is an important protein resource for food industries and has a bipolar filamentous structure that is composed of subfilaments that occur in vivo. It has been shown that a high ionic strength is required to prevent myosin from forming filamentous structures and to solubilize the protein in aqueous solution. In the presence of 100-200 mM NaCl, 50 mM arginine was more effective than other additives tested, including NaCl, in myosin solubilization. Before reaching equilibrium solubility, the myosin solution was initially supersaturated upon the dilution of a stock myosin solution in 1 M NaCl into the test solvents. Arginine slowed the process of equilibration and stabilized the supersaturated solution more effectively than other additives. No structural changes in myosin caused by arginine were observed, which indicated that arginine enhanced the solubility of myosin in a physiological salt solution without affecting the structure. Copyright © 2013 Elsevier B.V. All rights reserved.

  9. Synthesis and Application of Organic Phosphonate Salts as Draw Solutes in Forward Osmosis for Oil-Water Separation.

    PubMed

    Long, Qingwu; Shen, Liang; Chen, Rongbiao; Huang, Jiaqi; Xiong, Shu; Wang, Yan

    2016-11-01

    The development of suitable draw solution in forward osmosis (FO) process has attracted the growing attention for water treatment purpose. In this study, a series of organic phosphonate salts (OPSs) are synthesized by one-step Mannich-like reaction, confirmed by FTIR and NMR characterizations, and applied as novel draw solutes in FO applications. Their solution properties including osmotic pressures and viscosities, as well as their FO performance as a function of the solution concentration are investigated systematically. In FO process, a higher water flux of 47-54 LMH and a negligible reverse solute flux can be achieved in the PRO (AL-DS) mode (active layer faces the draw solution) using a homemade thin-film composite membrane (PSF-TFC) and deionized water as the feed solution. Among all OPS draw solutes, the tetraethylenepentamine heptakis(methylphosphonic) sodium salt (TPHMP-Na) exhibits the best FO flux at 0.5 mol/kg concentration, which is further applied for the separation of emulsified oil-water mixture. The recovery of diluted OPS solutions is carried out via a nanofiltration (NF) system with a rejection above 92%. The aforementioned features show the great potential of OPS compounds as a novel class of draw solutes for FO applications.

  10. Blending Of Radioactive Salt Solutions In Million Gallon Tanks

    SciTech Connect

    Leishear, Robert A.; Lee, Si Y.; Fowley, Mark D.; Poirier, Michael R.

    2012-12-10

    Research was completed at Savannah River National Laboratory (SRNL) to investigate processes related to the blending of radioactive, liquid waste, salt solutions in 4920 cubic meter, 25.9 meter diameter storage tanks. One process was the blending of large salt solution batches (up to 1135 ? 3028 cubic meters), using submerged centrifugal pumps. A second process was the disturbance of a settled layer of solids, or sludge, on the tank bottom. And a third investigated process was the settling rate of sludge solids if suspended into slurries by the blending pump. To investigate these processes, experiments, CFD models (computational fluid dynamics), and theory were applied. Experiments were performed using simulated, non-radioactive, salt solutions referred to as supernates, and a layer of settled solids referred to as sludge. Blending experiments were performed in a 2.44 meter diameter pilot scale tank, and flow rate measurements and settling tests were performed at both pilot scale and full scale. A summary of the research is presented here to demonstrate the adage that, ?One good experiment fixes a lot of good theory?. Experimental testing was required to benchmark CFD models, or the models would have been incorrectly used. In fact, CFD safety factors were established by this research to predict full-scale blending performance. CFD models were used to determine pump design requirements, predict blending times, and cut costs several million dollars by reducing the number of required blending pumps. This research contributed to DOE missions to permanently close the remaining 47 of 51 SRS waste storage tanks.

  11. Blending of Radioactive Salt Solutions in Million Gallon Tanks - 13002

    SciTech Connect

    Leishear, Robert A.; Lee, Si Y.; Fowley, Mark D.; Poirier, Michael R.

    2013-07-01

    Research was completed at Savannah River National Laboratory (SRNL) to investigate processes related to the blending of radioactive, liquid waste, salt solutions in 4920 cubic meter, 25.9 meter diameter storage tanks. One process was the blending of large salt solution batches (up to 1135 - 3028 cubic meters), using submerged centrifugal pumps. A second process was the disturbance of a settled layer of solids, or sludge, on the tank bottom. And a third investigated process was the settling rate of sludge solids if suspended into slurries by the blending pump. To investigate these processes, experiments, CFD models (computational fluid dynamics), and theory were applied. Experiments were performed using simulated, non-radioactive, salt solutions referred to as supernates, and a layer of settled solids referred to as sludge. Blending experiments were performed in a 2.44 meter diameter pilot scale tank, and flow rate measurements and settling tests were performed at both pilot scale and full scale. A summary of the research is presented here to demonstrate the adage that, 'One good experiment fixes a lot of good theory'. Experimental testing was required to benchmark CFD models, or the models would have been incorrectly used. In fact, CFD safety factors were established by this research to predict full-scale blending performance. CFD models were used to determine pump design requirements, predict blending times, and cut costs several million dollars by reducing the number of required blending pumps. This research contributed to DOE missions to permanently close the remaining 47 of 51 SRS waste storage tanks. (authors)

  12. Influence of deacetylation on the rheological properties of xanthan-guar interactions in dilute aqueous solutions.

    PubMed

    Khouryieh, H A; Herald, T J; Aramouni, F; Bean, S; Alavi, S

    2007-04-01

    An oscillating capillary rheometer was used to investigate the effects of xanthan deacetylation on the viscoelastic properties and intrinsic viscosity of xanthan and guar mixtures in dilute aqueous solutions. Deacetylated xanthan exhibited a stronger synergistic interaction with guar than native xanthan did due to the destabilized helical structure and increased chain flexibility of the deacetylated xanthan. No gels were observed for all xanthan-guar mixtures. Native xanthan-guar mixtures exhibited a liquid-like behavior, whereas deacetylated xanthan-guar mixtures exhibited a gel-like behavior. The relative viscosity and elasticity of deacetylated xanthan-guar mixtures were much stronger than those for native xanthan-guar mixtures. The intrinsic viscosities of deacetylated xanthan-guar mixtures were higher than the calculated values assuming no interaction, whereas the intrinsic viscosities of native xanthan-guar mixtures were lower than the calculated values assuming no interaction, demonstrating that intermolecular binding occurred between the disordered segments of xanthan and guar gum in dilute aqueous solutions.

  13. Spin Transport in Dilute, Spin-Polarized Solutions of Helium-Three in Helium-Four

    NASA Astrophysics Data System (ADS)

    McAllaster, Donald R.

    1992-01-01

    We have investigated ^3He spin diffusion in two dilute solutions of ^3 He in ^4He, with atomic fraction x^3=1.82times 10^{-3} and 6.26 times 10 ^{-4}, spin-polarized by an 8 T field. We do not find evidence that the diffusion coefficient for spins transverse to the average magnetization (D _|) declines or saturates at temperatures down to 0.20T_{rm F}, contrary to previous experiment (Gully and Mullin 1984) but in accord with current theory. We have compared our measurements with the latest theory of Jeon and Mullin (1991); our data is mostly in good agreement with their theory if a slightly modified version of a ^3 He-^3He interaction due to Ebner (1967) is used. The congruence between data and theory supports the conclusion that the s-wave approximation to the interaction is not useful for transport calculations even for these rather dilute solutions. There may be an one unresolved discrepancy: our diffusion constant for the lowest concentration at the lowest temperatures is 25% higher than theory predicts. This could be due to a polarization dependance for D_| or to a modification of the boundary condition by a bound ^3He state, or possibly due to errors in the theoretical calculation.

  14. Small scale dynamics of a shearless turbulent/non-turbulent interface in dilute polymer solutions

    NASA Astrophysics Data System (ADS)

    Cocconi, G.; De Angelis, E.; Frohnapfel, B.; Baevsky, M.; Liberzon, A.

    2017-07-01

    We study the physics of the turbulent/non-turbulent interface (TNTI) of an isolated turbulent region in dilute polymer solutions and Newtonian fluids. We designed an experimental setup of a turbulent patch growing in water/dilute polymer solutions, without mean shear and far from the walls. The observations from the experiments are complemented and expanded by simulations performed using a localised homogeneous forcing to generate the turbulent front and the Finitely Extensible Elastic model with the Peterlin closure model for the polymer stress. The comparison, which shows that when Newtonian and viscoelastic TNTIs are fed by the same energy they behave in similar manner both in the experiments and in the simulations, permits to extend the applicability, on a qualitative basis, of single relaxation time polymer models also to turbulent/non-turbulent interfaces. From the detailed analysis offered by the numerical results, the alterations in the dynamics between strain and vorticity help understanding the mechanics of the polymer action on the TNTI without mean shear. The reduced vorticity stretching and increased vorticity compression terms are found to be due to the modified degrees of alignment between vorticity, polymer conformation tensor, and rate-of-strain tensor eigenvectors observed especially near the interface. These alignments at the smallest scales of the non-Newtonian turbulent flow lead to a reduced production of enstrophy and consequently to a reduced entrainment, which in this problem are seen as reduced advancement of a turbulent region.

  15. Extensional Relaxation Times and Pinch-off Dynamics of Dilute Polymer Solutions

    NASA Astrophysics Data System (ADS)

    Dinic, Jelena; Zhang, Yiran; Jimenez, Leidy; Sharma, Vivek

    2015-11-01

    We show that visualization and analysis of capillary-driven thinning and pinch-off dynamics of the columnar neck in an asymmetric liquid bridge created by dripping-onto-substrate can be used for characterizing the extensional rheology of complex fluids. Using a particular example of dilute, aqueous PEO solutions, we show the measurement of both the extensional relaxation time and extensional viscosity of weakly elastic, polymeric complex fluids with low shear viscosity η< 20 mPa .s and relatively short relaxation time, λ <1 ms. Characterization of elastic effects and extensional relaxation times in these dilute solutions is beyond the range measurable in the standard geometries used in commercially available shear and extensional rheometers (including CaBER, capillary breakup extensional rheometer). As the radius of the neck that connects a sessile drop to a nozzle is detected optically, and the extensional response for viscoelastic fluids is characterized by analyzing their elastocapillary self-thinning, we refer to this technique as optically-detected elastocapillary self-thinning dripping-onto-substrate (ODES-DOS) extensional rheometry.

  16. Crossover Leung-Griffiths model and the phase behavior of dilute aqueous ionic solutions

    NASA Astrophysics Data System (ADS)

    Belyakov, M. Yu.; Kiselev, S. B.; Rainwater, J. C.

    1997-08-01

    A new parametric crossover model for the phase behavior of a binary mixture is presented that corresponds to the Leung-Griffiths model in the critical region and is transformed into the regular classical expansion far away from the critical point. The model is optimized to, and leads to excellent agreement with, isothermal vapor-liquid equilibrium data for dilute aqueous solutions of sodium chloride by Bischoff and co-workers. It then accurately predicts constant-composition phase equilibrium loci as measured by independent workers. This crossover model is therefore capable of representing the thermodynamic surface of ionic solutions in a large range of temperatures and densities around the critical points of vapor-liquid equilibrium.

  17. Kinetics of phase separation and coarsening in dilute surfactant pentaethylene glycol monododecyl ether solutions.

    PubMed

    Tanaka, S; Kubo, Y; Yokoyama, Y; Toda, A; Taguchi, K; Kajioka, H

    2011-12-21

    We investigated the phase separation phenomena in dilute surfactant pentaethylene glycol monodedecyl ether (C(12)E(5)) solutions focusing on the growth law of separated domains. The solutions confined between two glass plates were found to exhibit the phase inversion, characteristic of the viscoelastic phase separation; the majority phase (water-rich phase) nucleated as droplets and the minority phase (micelle-rich phase) formed a network temporarily, then they collapsed into an usual sea-island pattern where minority phase formed islands. We found from the real-space microscopic imaging that the dynamic scaling hypothesis did not hold throughout the coarsening process. The power law growth of the domains with the exponent close to 1/3 was observed even though the coarsening was induced mainly by hydrodynamic flow, which was explained by Darcy's law of laminar flow.

  18. Phase separation in dilute solutions of 3He in solid 4He

    NASA Astrophysics Data System (ADS)

    Huan, C.; Yin, L.; Xia, J. S.; Candela, D.; Cowan, B. P.; Sullivan, N. S.

    2017-03-01

    We report the results of studies of the phase separation of solid solutions of dilute concentrations of 3He in 4He. The temperatures and the kinetics of the phase separation were determined from NMR experiments for 3He concentrations 1.6 ×10-5solution theory as augmented by Edwards and Balibar [Phys. Rev. B 39, 4083 (1989), 10.1103/PhysRevB.39.4083]. The growth of 3He droplets shows a t1 /3 time dependence at long times consistent with Ostwald ripening.

  19. Separation of glycols from dilute aqueous solutions via complexation with boronic acids

    SciTech Connect

    Randel, L.A.; King, C.J.

    1991-07-01

    This work examines methods of separating low molecular weight glycols from dilute aqueous solution. Extraction into conventional solvents is generally not economical, since, in the literature reviewed, distribution ratios for the two- to four-carbon glycols are all less than one. Distribution ratios can be increased, however, by incorporating into the organic phase an extracting agent that will complex with the solute of interest. The extracting agent investigated in this work is 3-nitrophenylboronic acid (NPBA). NPBA, a boric acid derivative, reversibly complexes with many glycols. The literature on complexation of borate and related compounds with glycols, including mechanistic data, measurement techniques, and applications to separation processes, provides information valuable for designing experiments with NPBA and is reviewed herein. 88 refs., 15 figs., 24 tabs.

  20. Enhancing wastewater reuse by forward osmosis with self-diluted commercial fertilizers as draw solutes.

    PubMed

    Zou, Shiqiang; He, Zhen

    2016-08-01

    Using fertilizers as draw solutes in forward osmosis (FO) can accomplish wastewater reuse with elimination of recycling draw solute. In this study, three commercial fast-release all-purpose solid fertilizers (F1, F2 and F3) were examined as draw solutes in a submerged FO system for water extraction from either deionized (DI) water or the treated wastewater. Systematic optimizations were conducted to enhance water extraction performance, including operation modes, initial draw concentrations and in-situ chemical fouling control. In the mode of the active layer facing the feed (AL-F or FO), a maximum of 324 mL water was harvested using 1-M F1, which provided 41% of the water need for fertilizer dilution for irrigation. Among the three fertilizers, F1 containing a lower urea content was the most favored because of a higher water extraction and a lower reverse solute flux (RSF) of major nutrients. Using the treated wastewater as a feed solution resulted in a comparable water extraction performance (317 mL) to that of DI water in 72 h and a maximum water flux of 4.2 LMH. Phosphorus accumulation on the feed side was mainly due to the FO membrane solute rejection while total nitrogen and potassium accumulation was mainly due to RSF from the draw solute. Reducing recirculation intensity from 100 to 10 mL min(-1) did not obviously decrease water flux but significantly reduced the energy consumption from 1.86 to 0.02 kWh m(-3). These results have demonstrated the feasibility of using commercial solid fertilizers as draw solutes for extracting reusable water from wastewater, and challenges such as reverse solute flux will need to be further addressed.

  1. Segregation of solutes and gases in experimental freezing of dilute solutions: implications for natural glacial systems

    NASA Astrophysics Data System (ADS)

    Killawee, J. A.; Fairchild, I. J.; Tison, J.-L.; Janssens, L.; Lorrain, R.

    1998-12-01

    Low ionic strength waters containing significant calcium and bicarbonate are common in nature, but little literature exists on their behaviour during freezing. Modelling indicates that freezing-induced concentration of solutes (in a closed-system) would lead to progressive increase in calcite saturation index, despite rising partial pressure of CO 2 (PCO 2), but the consequences of CaCO 3 precipitation for the distribution of matter between solid, liquid, and gas phases required experimental investigation. We studied the effects of variations in the rate of advance of an ice-water interface and in the initial degree of saturation for calcite on the behaviour of the system. Downward growth of ice in a 24-cm diameter cylindrical vessel was achieved at a constant linear rate of 3 or 8 mm/h by the progressive cooling of an overlying alcohol reservoir, and the expansion of volume accommodated by regular water sampling through side ports, together with a small expansion chamber. Initial air-saturated solutions (initial PCO 2 in the range 10 -3 to 10 -3.2) were prepared to reflect a range from strongly undersaturated to supersaturated for calcite. Comparative blank experiments were run using deionized water. Ice growth led to enrichment in solutes at the ice-water interface and the creation of a diffusive boundary layer, calculated to be 0.6 mm thick, truncated below by convecting fluid. The first-formed ice (stage 1), was relatively solute-rich because of initial rapid ice nucleation. Where solutions were not strongly supersaturated for calcite this was followed by formation of a solute-poor (stage 2) ice. Ice-interface water segregation coefficients of stage 2 ice were calculated to be 0.0004-0.003 for various solute ions. The relative magnitude of segregation coefficients (Mg 2+ > Ca 2+ > Sr 2+) is attributed to interstitial incorporation (coupled with HCO 3-) in the ice lattice, and controlled by ion size. Air bubbles nucleated once nitrogen supersaturation had

  2. Many segments and few dollars: SALT solutions for ELTs?

    NASA Astrophysics Data System (ADS)

    Buckley, David A. H.; Meiring, Jacobus G.; Swiegers, Jian; Swart, Gerhard P.

    2004-07-01

    The Southern African Large Telescope (SALT) is a little over 18 months away from completion (in early 2005). It is based on the innovative tilted-Arecibo optical analog, first pioneered by the Hobby-Eberly Telescope (HET). By the end of 2003, all major subsystems, including the verification instrument, will be in place and the commissioning of them begun. Tests of a 7-segment subset of the mirror array, including the Shack-Hartmann alignment instrument, the mirror actuators, capacitive edge sensors and active control system has recently started. The first engineering on-sky tests involving the complete light path, from object to detector, have begun. SALT's primary mirror consists of 91 identical segments mounted on a 9 point whiffle tree mount, using three actuators to control tip and tilt, and a foil-type capacitive edge sensor to detect mirror misalignment. These 480 relatively affordable sensors are permanently attached to the segment edges, and are capable of measuring all misalignment modes, including global radius of curvature. This sensing system, used together with a Shack-Hartman wavefront instrument at the center of curvature, controls the primary mirror array, and could be scaled to an array of the size envisaged for an ELT. SALT has developed some innovative designs improvement over the original HET concept. These include a more effective spherical aberration corrector (SAC), interferometric distance sensing and laser auto-collimation of the prime focus payload, the use of newly developed efficient and durable mirror coatings on the SAC optics, and the use of economical low expansion ceramics for the primary mirror segments. These innovative and cost effective solutions used on SALT have potential applications to ELT designs.

  3. Effects of compound-specific dilution on transient transport and solute breakthrough: A pore-scale analysis

    NASA Astrophysics Data System (ADS)

    Rolle, Massimo; Kitanidis, Peter K.

    2014-09-01

    This pore-scale modeling study in saturated porous media shows that compound-specific effects are important not only at steady-state and for the lateral displacement of solutes with different diffusivities but also for transient transport and solute breakthrough. We performed flow and transport simulations in two-dimensional pore-scale domains with different arrangement of the solid grains leading to distinct characteristics of flow variability and connectivity, representing mildly and highly heterogeneous porous media, respectively. The results obtained for a range of average velocities representative of groundwater flow (0.1-10 m/day), show significant effects of aqueous diffusion on solute breakthrough curves. However, the magnitude of such effects can be masked by the flux-averaging approach used to measure solute breakthrough and can hinder the correct interpretation of the true dilution of different solutes. We propose, as a metric of mixing, a transient flux-related dilution index that allows quantifying the evolution of solute dilution at a given position along the main flow direction. For the different solute transport scenarios we obtained dilution breakthrough curves that complement and add important information to traditional solute breakthrough curves. Such dilution breakthrough curves allow capturing the compound-specific mixing of the different solutes and provide useful insights on the interplay between advective and diffusive processes, mass transfer limitations, and incomplete mixing in the heterogeneous pore-scale domains. The quantification of dilution for conservative solutes is in good agreement with the outcomes of mixing-controlled reactive transport simulations, in which the mass and concentration breakthrough curves of the product of an instantaneous transformation of two initially segregated reactants were used as measures of reactive mixing.

  4. Optical Sensor for Characterizing the Phase Transition in Salted Solutions

    PubMed Central

    Claverie, Rémy; Fontana, Marc D.; Duričković, Ivana; Bourson, Patrice; Marchetti, Mario; Chassot, Jean-Marie

    2010-01-01

    We propose a new optical sensor to characterize the solid-liquid phase transition in salted solutions. The probe mainly consists of a Raman spectrometer that extracts the vibrational properties from the light scattered by the salty medium. The spectrum of the O – H stretching band was shown to be strongly affected by the introduction of NaCl and the temperature change as well. A parameter SD defined as the ratio of the integrated intensities of two parts of this band allows to study the temperature and concentration dependences of the phase transition. Then, an easy and efficient signal processing and the exploitation of a modified Boltzmann equation give information on the phase transition. Validations were done on solutions with varying concentration of NaCl. PMID:22319327

  5. Osmotic swelling of polyacrylate hydrogels in physiological salt solutions.

    PubMed

    Horkay, F; Tasaki, I; Basser, P J

    2000-01-01

    The swelling behavior of fully neutralized sodium polyacrylate gels was investigated in aqueous solutions of alkali metal (LiCl, NaCl, KCl, CsCl) and alkaline earth metal salts (CaCl2, SrCl2, BaCl2). The total salt concentration and the ratio of monovalent to divalent cations were varied in the biologically significant range. It is found that the concentrations of both monovalent and divalent cations vary continuously and smoothly in the gel despite the abrupt change in the gel volume. The individual elastic, mixing, and ionic contributions to the free energy of the gel were separately determined as a function of the degree of network swelling to elucidate the thermodynamics of swelling. Shear modulus measurements performed at different Ca2+ concentrations suggest that Ca2+ does not form stable cross-links between the polymer chains. At low and moderate swelling ratios the concentration dependence of the shear modulus follows a power law behavior, G variation of phi n, with n = 0.34 +/- 0.03. At high swelling degrees, however, the shear modulus increases with increasing swelling. The value of the Flory-Huggins interaction parameter, chi, determined from osmotic swelling pressure and shear modulus measurements, strongly depends on the ionic composition of the equilibrium solution and increases with increasing Ca2+ concentration.

  6. Surface Potential of DPPC Monolayers on Concentrated Aqueous Salt Solutions.

    PubMed

    Casper, Clayton B; Verreault, Dominique; Adams, Ellen M; Hua, Wei; Allen, Heather C

    2016-03-03

    The presence and exchange of electrical charges on the surfaces of marine aerosols influence their ability to act as cloud condensation nuclei and play a role in thundercloud electrification. Although interactions exist between surface-active inorganic ions and organic compounds, their role in surface charging of marine aerosols is not well understood. In this study, the surface potential of dipalmitoylphosphatidylcholine (DPPC) monolayers, a zwitterionic phospholipid found in the sea surface microlayer, is measured on concentrated (0.3-2.0 M) chloride salt solutions containing marine-relevant cations (Na(+), K(+), Mg(2+), Ca(2+)) to model and elucidate the electrical properties of organic-covered marine aerosols. Monovalent cations show only a weak effect on the surface potential of DPPC monolayers in the condensed phase compared to water. In contrast, Mg(2+) and Ca(2+) increase the surface potential, indicating different cation binding modes and affinities for the PC headgroup. Moreover, it is found that for divalent chloride salt solutions, the PC headgroup and interfacial water molecules make the largest dipolar contribution to the surface potential. This study shows that for equal charge concentrations, divalent cations impact surface potential of DPPC monolayers more strongly than monovalents likely through changes in the PC headgroup orientation induced by their complexation along with the lesser ordering of interfacial water molecules caused by phosphate group charge screening.

  7. Terahertz echoes reveal the inhomogeneity of aqueous salt solutions

    NASA Astrophysics Data System (ADS)

    Shalit, Andrey; Ahmed, Saima; Savolainen, Janne; Hamm, Peter

    2017-03-01

    The structural and dynamical properties of water are known to be affected by ion solvation. However, a consistent molecular picture that describes how and to what extent ions perturb the water structure is still missing. Here we apply 2D Raman-terahertz spectroscopy to investigate the impact of monatomic cations on the relaxation dynamics of the hydrogen-bond network in aqueous salt solutions. The inherent ability of multidimensional spectroscopy to deconvolute heterogeneous relaxation dynamics is used to reveal the correlation between the inhomogeneity of the collective intermolecular hydrogen-bond modes and the viscosity of a salt solution. Specifically, we demonstrate that the relaxation time along the echo direction t1 = t2 correlates with the capability of a given cation to 'structure' water. Moreover, we provide evidence that the echo originates from the water-water modes, and not the water-cation modes, which implies that cations can structure the hydrogen-bond network to a certain extent.

  8. Theory and Simulation of Cholesteric Film Formation Flows of Dilute Collagen Solutions.

    PubMed

    Aguilar Gutierrez, O F; Rey, Alejandro D

    2016-11-15

    Dilute isotropic collagen solutions are usually flow processed into monodomain chiral nematic thin films for obtaining highly ordered materials by a multistep process that starts with complex inhomogeneous flow kinematics. Here we present rigorous theory and simulation of the initial precursors during flow steps in cholesteric collagen film formation. We first extract the molecular shape parameter and rotational diffusivity from previously reported simple shear data of dilute collagen solutions, where the former leads the reactive parameter (tumbling function) which determines the net effect of vorticity and strain rate on the average orientation and where the latter establishes the intensity of strain required for flow-birefringence, both crucial quantities for controlled film formation flow. We find that the tumbling function is similar to those of rod-like lyotropic liquid crystalline polymers and hence it is predicted that they would tumble in the ordered high concentration state leading to flow-induced texturing. The previously reported experimental data is well fitted with rotational diffusivities whose order of magnitude is consistent to those of other biomacromolecules. We then investigate the response of the tensor order parameter to complex flow kinematics, ranging from pure vorticity, through simple shear, to extensional flow, as may arise in typical flow casting and film flows. The chosen control variable to produce precursor cholesteric films is the director or average orientation, since the nematic order is set close to typical values found in concentrated cholesteric type I collagen solutions. Using the efficient four-roll mill kinematics, we summarize the para-nematic structure-flow process diagram in terms of the director orientation and flow type. Using analysis and computation, we provide a parametric envelope that is necessary to eventually produce well-aligned cholesteric films. We conclude that extensional flow is an essential ingredient of

  9. Transport properties of dilute α -Fe (X ) solid solutions (X = C, N, O)

    NASA Astrophysics Data System (ADS)

    Schuler, Thomas; Nastar, Maylise

    2016-06-01

    We extend the self-consistent mean field (SCMF) method to the calculation of the Onsager matrix of Fe-based interstitial solid solutions. Both interstitial jumps and substitutional atom-vacancy exchanges are accounted for. A general procedure is introduced to split the Onsager matrix of a dilute solid solution into intrinsic cluster Onsager matrices, and extract from them flux-coupling ratios, mobilities, and association-dissociation rates for each cluster. The formalism is applied to vacancy-interstitial solute pairs in α -Fe (V X pairs, X = C, N, O), with ab initio based thermodynamic and kinetic parameters. Convergence of the cluster mobility contribution gives a controlled estimation of the cluster definition distance, taking into account both its thermodynamic and kinetic properties. Then, the flux-coupling behavior of each V X pair is discussed, and qualitative understanding is achieved from the comparison between various contributions to the Onsager matrix. Also, the effect of low-activation energy second-nearest-neighbor interstitial solute jumps around a vacancy on these results is addressed.

  10. Low frequency dielectric dispersion study of PVC-PPy blends in dilute solution of different solvents

    NASA Astrophysics Data System (ADS)

    Sharma, Deepika; Tripathi, Deepti

    2017-05-01

    In present study,the effect of adding Polypyrrole (PPy), a conductive polymer, on the dielectric and electrical behavior of Polyvinyl chloride (PVC) in dilute solution of moderate polar solvent Tetrahydrofuran (THF) and polar solvent M-Cresol at low frequency is investigated. The blend of PVC with PPy forms a colloidal solution in both the solvents. The dielectric dispersion study of PVC-PPy blends in THF and M-Cresol has been carried out in the frequency range of 20Hz to 2MHz at temperature of 303 K. The influence of solvent on dielectric and electrical parameters such as dielectric constant [ɛ*(ω)], loss tangent (tan δ) and ac conductivity (σac) of PVC - PPy solutions is studied. At low frequencies, electrode polarization seems to have dominant effect on the complex dielectric constant. The values of relaxation time corresponding to this phenomena is also reported. Dielectric dispersion studies show that the solvent environment plays significant role in governing segmental motion of polymer chain in solution.

  11. The electroremoval of copper from dilute waste solutions using Swiss-roll electrode cell

    NASA Astrophysics Data System (ADS)

    Saba, A. E.; El Sherif, A. E.; Elsayed, E. M.

    2007-10-01

    Copper is usually present in concentrations less than 5 g/L-1 in dilute waste solutions. The low concentrations make these solutions unsuitable for the electro-flow owinning processes via conventional electrolysis cells. Unconventional, two-and three-dimensional electrode cells with relatively large cathodic area are essential for such treatment. Different types of cells are mentioned in the literature. Among these cells, the two-dimensional Swiss-roll cell (SR) is considered in this study. The effects of cathodic current densities, initial copper concentrations, free sulfuric acid concentration, the presence of iron and zinc cations, and the rate of flow of the solution on both the cathodic current efficiency and power consumption were studied. Copper was removed from synthetic and industrial mixtures of Cu/Fe/Zn sulfate solutions to less than 5 ppm with power consumptions of 10.326 kWh/kg-1 and 8.61 kWh/kg-1, respectively. The correlation between the SR cell and packed-column cell on such treatment was also considered.

  12. A comparison of different dilute solution explosions pretreatment for conversion of distillers' grains into ethanol.

    PubMed

    Zhang, Jian; Zhang, Wen-Xue; Wu, Zheng-Yun; Yang, Jian; Liu, Yue-Hong; Zhong, Xia; Deng, Yu

    2013-01-01

    In order to improve the efficiency of distillers' grains converting to ethanol, 13 dilute solution explosions were evaluated based on the optimization of pure water explosion. To decrease residual inhibitor content, the exploded slurry was dried at 105°C. Using a 1.1 mol/L butanone solution explosion, with the explosion temperature set at 160°C (pressure at 1.9 MPa), the residence time at 10 min, and the dried distillers' grains-to-water ratio at 1:2 (w/w), the yields of total sugar, glucose, and xylose were 86%, 89%, and 84% (w/w), respectively, and the ethanol yield was 25.3 g/100 g distillers' grains dry matter. Moreover, the eight other reagent solution explosions improved the efficiency of enzymatic hydrolysis, and of simultaneous saccharification and co-fermentation, and the residual contents of furfural, 5-hydroxymethylfurfural, and acetic acid decreased to an acceptable concentration range after detoxification by drying. The results suggested that compared with pure water explosions, the use of volatile solutions lowered the explosive temperature and improved the sugar yield. This study offers a reference for the further study of lignocellulosic materials with higher starch and hemicelluloses contents as raw materials for converting biomass to bioethanol.

  13. Formation and stabilization of anionic metal complexes in concentrated aqueous quaternary ammonium salt solutions

    SciTech Connect

    Aronson, F.L.; Hwang, L.L.Y.; Ronca, N.; Solomon, N.A.; Steigman, J.

    1985-02-04

    Anionic complexes of transition metals were stabilized in aqueous solutions containing high concentrations of various short-chain quaternary ammonium salts. Compounds with longer paraffin chains were effective in much less concentrated solution. Complex ions were detected spectrophotometrically. FeCl/sub 4//sup -/, which is usually formed in concentrated HCl, was the predominant Fe(III) complex in 30 m choline chloride containing only 0.12 M HCl. A yellow transitory Tc(VII) chloro-addition intermediate, formed in the reduction of TcO/sub 4//sup -/ by concentrated HCl, was stabilized when the solution also contained 25 m choline chloride. Its spectrum, as well as the isolation of an already known Tc(VII) bipyridyl complex, is reported. Concentrated organic electrolytes also stabilized Tc(V) oxide halides against disproportionation and Tc(IV) hexahalides against hydrolysis. Halochromates of Cr(VI) were formed and stabilized in dilute acid containing quaternary ammonium salts. Their UV spectra showed the well-resolved vibronic fine structure associated with the symmetric chromium-to-oxygen charge-transfer band. It is known that these progressions are resolved in aprotic solvents, but not in aqueous acidic solution alone, and that the loss of fine structure in aqueous media is due to hydrogen bonding. The stabilization of anionic metal complexes and the resolution of vibronic structure in halochromates are probably consequences of water-structure-enforced ion paring. The present work suggests that the water molecules in immediate contact with the complex anions are more strongly hydrogen bonded to each other than to the complex. 21 references, 4 figures.

  14. [Forming the nanosized molecular assemblies (nanoassociates) is a key to understand the properties of highly diluted aqueous solutions].

    PubMed

    Konovalov, A I; Ryzhkina, I S; Murtazina, L I; Kiseleva, Iu V

    2014-01-01

    In the present study it was shown that biological effects of highly diluted aqueous solutions were due to the formation of nano-sized (up to 400 nm) molecular assemblies, called nanoassociates mainly consisting of aqueous molecules (up to 500 million) under the influence of two effectors: solute and external electromagnetic fields.

  15. Oligonucleotides as probes for studying polymerization reactions in dilute aqueous solution

    NASA Technical Reports Server (NTRS)

    Kolb, V.; Orgel, L. E.; Miller, S. L. (Principal Investigator)

    1994-01-01

    We have prepared a [32P]-labled oligonucleotide probe carrying a free primary amine at its 3'-terminus. This probe is used to initiate polymerization of aziridine (ethyleneimine) in aqueous solution. The nature of the oligomeric products and the kinetics of their formation are then monitored by gel electrophoresis. Our results are generally consistent with those obtained using conventional techniques. We have also investigated the effect of polyanionic templates on the rate of oligomerization of aziridine. We find that water-soluble polyanions generally accelerate the polymerization. The sodium salt of polymethacrylic acid is the most effective of the templates that we studied. The methods introduced in this paper should be applicable to a variety of polymerization reactions in aqueous solution. They should greatly simplify the screening of potentially prebiotic polymerization reactions.

  16. Structures and stability of salt-bridge in aqueous solution.

    PubMed

    Sagarik, Kritsana; Chaiyapongs, Supaporn

    2005-09-01

    Structures and stability of salt-bridges in aqueous solutions were investigated using a complex formed from the guanidinium (Gdm+) and formate (FmO-) ions as a model system. The Test-particle model (T-model) potentials to describe the interactions in the Gdm+-H2O, FmO(-)-H2O and Gdm+-FmO- complexes were constructed, tested and applied in molecular dynamics (MD) simulations of the aqueous solutions at 298 K. The three-dimensional structures and energetic of the hydrogen bond (H-bond) networks of water in the first hydration shells of the Gdm+ and FmO- ions, as well as the Gdm+-FmO- complex, were visualized and analyzed using various probability distribution (PD) maps. The structures of the average potential energy landscapes at the H-bond networks were employed to characterize the stability and dynamic behavior of water molecules in the first hydration shells of the solutes. It was observed that water molecules in the first hydration shell of the close-contact Gdm+-FmO- complex form associated H-bond networks, which introduce a net stabilization effect to the ion-pair, whereas those in the interstitial H-bond network destabilize and break the solvent-separated Gdm+-FmO- complex. The present results showed that, in order to provide complete insights into the structures and stability of ion-pairs in aqueous solutions, explicit water molecules have to be included in the model calculations.

  17. Cloud-point temperatures for lysozyme in electrolyte solutions: effect of salt type, salt concentration and pH.

    PubMed

    Grigsby, J J; Blanch, H W; Prausnitz, J M

    2001-07-24

    Liquid-liquid phase-separation data were obtained for aqueous saline solutions of hen egg-white lysozyme at a fixed protein concentration (87 g/l). The cloud-point temperature (CPT) was measured as a function of salt type and salt concentration to 3 M, at pH 4.0 and 7.0. Salts used included those from mono and divalent cations and anions. For the monovalent cations studied, as salt concentration increases, the CPT increases. For divalent cations, as salt concentration rises, a maximum in the CPT is observed and attributed to ion binding to the protein surface and subsequent water structuring. Trends for sulfate salts were dramatically different from those for other salts because sulfate ion is strongly hydrated and excluded from the lysozyme surface. For anions at fixed salt concentration, the CPT decreases with rising anion kosmotropic character. Comparison of CPTs for pH 4.0 and 7.0 revealed two trends. At low ionic strength for a given salt, differences in CPT can be explained in terms of repulsive electrostatic interactions between protein molecules, while at higher ionic strength, differences can be attributed to hydration forces. A model is proposed for the correlation and prediction of the CPT as a function of salt type and salt concentration. NaCl was chosen as a reference salt, and CPT deviations from that of NaCl were attributed to hydration forces. The Random Phase Approximation, in conjunction with a square-well potential, was used to calculate the strength of protein-protein interactions as a function of solution conditions for all salts studied.

  18. Temperature dependence of the activity of Al in dilute Ni(Al) solid solutions

    SciTech Connect

    Jiang Yong; Smith, J. R.; Evans, A. G.

    2006-12-01

    Activities of dilute Al solid solutions in Ni are determined from a first-principles approach. Both thermal lattice vibration and electronic contributions to free energies are considered and compared. Vibrational contributions tend to dominate the temperature dependencies of the free energies, though electron thermal effects are significant. Calculations show opposing temperature trends for the formation enthalpies and entropies, leading to a partial cancellation of their role in the overall energetics. Nevertheless, their remaining temperature effects are strong. Over the temperature range, 400 K

  19. Wavelet treatment of the intrachain correlation functions of homopolymers in dilute solutions

    NASA Astrophysics Data System (ADS)

    Fedorov, M. V.; Chuev, G. N.; Kuznetsov, Yu. A.; Timoshenko, E. G.

    2004-11-01

    Discrete wavelets are applied to the parametrization of the intrachain two-point correlation functions of homopolymers in dilute solutions obtained from Monte Carlo simulations. Several orthogonal and biorthogonal basis sets have been investigated for use in the truncated wavelet approximation. The quality of the approximation has been assessed by calculation of the scaling exponents obtained from the des Cloizeaux ansatz for the correlation functions of homopolymers with different connectivities in a good solvent. The resulting exponents are in better agreement with those from recent renormalization group calculations as compared to the data without the wavelet denoising. We also discuss how the wavelet treatment improves the quality of data for correlation functions from simulations of homopolymers at varied solvent conditions and of heteropolymers.

  20. Geometric pumping induced by shear flow in dilute liquid crystalline polymer solutions.

    PubMed

    Yabunaka, Shunsuke; Yabunaka, Shunsuka; Hayakawa, Hisao

    2015-02-07

    We investigate nonlinear rheology of dilute liquid crystalline polymer solutions under time dependent two-directional shear flow. We analyze the Smoluchowski equation, which describes the dynamics of the orientation of a liquid crystalline polymer, by employing technique of the full counting statistics. In the adiabatic limit, we derive the expression for time integrated currents generated by a Berry-like curvature. Using this expression, it is shown that the expectation values of the time-integrated angular velocity of a liquid crystalline polymer and the time-integrated stress tensor are generally not zero even if the time average of the shear rate is zero. The validity of the theoretical calculations is confirmed by direct numerical simulations of the Smoluchowski equation. Nonadiabatic effects are also investigated by means of simulations and it is found that the time-integrated stress tensor depends on the speed of the modulation of the shear rate if we adopt the isotropic distribution as an initial state.

  1. Soluble aggregates in aqueous solutions of polyion-surfactant ion complex salts and a nonionic surfactant.

    PubMed

    Janiak, John; Tomšič, Matija; Lundberg, Dan; Olofsson, Gerd; Piculell, Lennart; Schillén, Karin

    2014-08-14

    Water-soluble aggregates based on two polyion-surfactant ion "complex salts", consisting of hexadecyltrimethylammonium (C16TA(+)) and polyacrylate (PA(-)) with either 25 or 6000 repeating units, with added nonionic surfactant octaethylene glycol monododecyl ether (C12E8) have been investigated. A previous phase study has shown that added C12E5 or C12E8 can solubilize complex salts in aqueous systems, and that increasing the poly(ethylene oxide) chain length of the nonionic surfactant and/or decreasing the polyion length favors dissolution. In this work we report on dynamic light scattering, NMR diffusometry, small-angle X-ray scattering, and isothermal titration calorimetry measurements performed to characterize the solubilized composite aggregates in dilute aqueous solution in terms of size and stoichiometry. It was found that mixed aggregates of polyacrylate, C16TA(+) ions, and C12E8, with almost constant stoichiometry, coexist with free micelles of C12E8 at all investigated mixing ratios. The length of the polyion only weakly affects the stoichiometry of the mixed aggregates while strongly affecting their size and water solubility.

  2. Acoustic and volumetric studies of intermolecular interactions in dilute solutions of methanol in aromatic amines

    NASA Astrophysics Data System (ADS)

    Marczak, W.; Chowanska, A.; Piwowarska, B.

    2005-10-01

    Limiting partial compressibilities and volumes of methanol in pyridine, 2-methylpyridine, 3-methylpyridine, 4-methylpyridine and 2,6-dimethylpyridine were calculated from the experimental speeds of sounds and densities of dilute solutions at 298.15 K. The limiting functions were found to be linearly correlated with the association energies of isolated 1:1 complexes of the pyridine derivatives with water. Those association energies are close to the energies for similar complexes with methanol. The results evidence that ortho effect enhances the ability of pyridines to hydrogen bonding with methanol in the same way as with water. The effect consist in changes of hydrogen bond energy, unspecific interactions with a steric hindrance, e.g. between hydrocarbon tail of the alcohol molecule and the methyl group in the ring, and changes in resonance interactions. Stronger hydrogen bonds cause smaller partial molar compressibilities and volumes of the solute, as well as greater negative enthalpies of solution. Importantly, single molecule of water or methanol forms one hydrogen bond with the proton-accepting solvent.

  3. Results of Hg speciation testing on MCU strip effluent hold tank (SEHT) and decontaminated salt solution hold tank (DSSHT) materials

    SciTech Connect

    Bannochie, C. J.

    2015-09-17

    The Savannah River National Laboratory (SRNL) was tasked with preparing and shipping samples for Hg speciation by Eurofins Frontier Global Sciences, Inc. in Seattle, WA on behalf of the Savannah River Remediation (SRR) Mercury Task Team.i,ii The tenth shipment of samples was designated to include Modular Caustic Side Solvent Extraction Unit (MCU) Strip Effluent Hold Tank (SEHT) and MCU Decontaminated Salt Solution Hold Tank (DSSHT) materials from processing Salt Batch 7b. The MCU SEHT (MCU-15-722) and DSSHT (MCU-15-709) samples were pulled on June 15, 2015. All MCU samples were received at SRNL on June 16, 2015. The DSSHT sample was moved the same day to refrigeration, while the SEHT sample was placed in the Shielded Cells. On July 9, 2015 it was opened and an aliquot diluted 1:100 with Eurofins deionized water and a portion of the diluted sample transferred to a Teflon® bottle prior to moving it to refrigeration that same day. All samples were kept in the dark and refrigerated until final dilutions were prepared for shipment to Eurofins.

  4. Raman spectroscopic study of the conformation of dicarboxylic acid salts in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Fukushima, Kunio; Watanabe, Toshiaki; Umemura, Matome

    1986-08-01

    It is already known that the molecules of long chain monocarboxylic acid salts have a tendency to form micelles in aqueous solutions, the molecular chain taking the all- trans zigzag structure. However it is considered difficult for dicarboxylic acid salts to adopt the same structure as the monocarboxylic acid salts as they have two carboxyl groups, one on each end of the molecular chain. Therefore, a special structure is expected to exist for dicarboxylic acid salts in aqueous solution. In order to examine this, Raman spectra of suberic acid salt and azelaic acid salt in aqueous solution were measured and the normal vibrational calculation carried out, showing that dicarboxylic acid salts have a helical structure in aqueous solution.

  5. Effect of inorganic salts on crystallization of poly(ethylene glycol) in frozen solutions.

    PubMed

    Izutsu, Ken-ichi; Aoyagi, Nobuo

    2005-01-06

    The effect of inorganic salts on eutectic crystallization of poly(ethylene glycol) (PEG) 1500-20,000 in frozen solution was studied to model the polymer and inorganic salt interaction in freeze-dried formulations. Thermal analysis of an aqueous PEG 3000 solution showed a eutectic PEG crystallization exotherm at approximately -47 degrees C and a subsequent PEG crystal melting endotherm at -14.9 degrees C. Addition of sodium chloride prevented the PEG crystallization in the freeze-concentrated solution surrounding ice crystals. Higher concentration NaCl was required to retain higher molecular weight PEG in the amorphous state. Various inorganic salts prevented the PEG crystallization to varying degrees depending mainly on the position of the anion in the Hofmeister's lyotropic series. Some salting-in and 'intermediate' salts (NaSCN, NaI, NaBr, NaCl, LiCl, KCl, and RbCl) inhibited the crystallization of PEG 7500 in frozen solutions. On the other hand, salting-out salts (NaH2PO4, Na2HPO4, Na2SO4, and NaF) did not show an apparent effect on the PEG crystallization. Some salting-out salts induced PEG crystallization in PEG and sucrose combination frozen solutions. The varying abilities of salts to prevent the PEG crystallization in frozen solutions strongly suggested that the solutes had different degrees of miscibility in the freeze-concentrates.

  6. Modeling mass transfer and reaction of dilute solutes in a ternary phase system by the lattice Boltzmann method

    NASA Astrophysics Data System (ADS)

    Fu, Yu-Hang; Bai, Lin; Luo, Kai-Hong; Jin, Yong; Cheng, Yi

    2017-04-01

    In this work, we propose a general approach for modeling mass transfer and reaction of dilute solute(s) in incompressible three-phase flows by introducing a collision operator in lattice Boltzmann (LB) method. An LB equation was used to simulate the solute dynamics among three different fluids, in which the newly expanded collision operator was used to depict the interface behavior of dilute solute(s). The multiscale analysis showed that the presented model can recover the macroscopic transport equations derived from the Maxwell-Stefan equation for dilute solutes in three-phase systems. Compared with the analytical equation of state of solute and dynamic behavior, these results are proven to constitute a generalized framework to simulate solute distributions in three-phase flows, including compound soluble in one phase, compound adsorbed on single-interface, compound in two phases, and solute soluble in three phases. Moreover, numerical simulations of benchmark cases, such as phase decomposition, multilayered planar interfaces, and liquid lens, were performed to test the stability and efficiency of the model. Finally, the multiphase mass transfer and reaction in Janus droplet transport in a straight microchannel were well reproduced.

  7. Dilute and Semidilute Solutions of a Nonionic, Rigid, Water-soluble Polymer

    NASA Astrophysics Data System (ADS)

    Russo, Paul; Huberty, Wayne; Zhang, Donghui; Water-Soluble Rodlike Polymer Team Collaboration

    2014-03-01

    The solution physics of random polymer chains was established largely on the behavior of commercial polymers such as polystyrene for organic solvents or nonionic poly(ethyleneoxide) for aqueous solvents. Not only are these materials widely available for industrial use, they can be synthesized to be essentially monodisperse. When it comes to stiff polymers, good choices are few and less prone to be used in industrial applications. Much was learned from polypeptides such as poly(benzylglutamate) or poly(stearylglutamate) in polar organic solvents and nonpolar organic solvents, respectively, but aqueous systems generally require charge. Poly(Nɛ-2-[2-(2-Methoxyethoxy) ethoxy]acetyl-L-Lysine) a.k.a. PEGL was pioneered by Deming and coworkers. In principle, PEGL provides a convenient platform from which to study stiff polymer behavior--phase relations, dynamics, liquid crystal formation and gelation--all with good molecular weight control and uniformity and without electrical charge. Still, a large gap in knowledge exists between PEGL and traditional rodlike polymer systems. To narrow this gap, dynamic and static scattering, circular dichroism, and viscosity measurements have been made in dilute and semidilute solutions as necessary preliminaries for lyotropic liquid crystalline and gel phases. Supported by NSF DMR 1306262. Department of Chemistry and Macromolecular Studies Group. Current address: Georgia Institute of Technology, School of Materials Science and Engineering.

  8. Visualizing phase transition behavior of dilute stimuli responsive polymer solutions via Mueller matrix polarimetry.

    PubMed

    Narayanan, Amal; Chandel, Shubham; Ghosh, Nirmalya; De, Priyadarsi

    2015-09-15

    Probing volume phase transition behavior of superdiluted polymer solutions both micro- and macroscopically still persists as an outstanding challenge. In this regard, we have explored 4 × 4 spectral Mueller matrix measurement and its inverse analysis for excavating the microarchitectural facts about stimuli responsiveness of "smart" polymers. Phase separation behavior of thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) and pH responsive poly(N,N-(dimethylamino)ethyl methacrylate) (PDMAEMA) and their copolymers were analyzed in terms of Mueller matrix derived polarization parameters, namely, depolarization (Δ), diattenuation (d), and linear retardance (δ). The Δ, d, and δ parameters provided useful information on both macro- and microstructural alterations during the phase separation. Additionally, the two step action ((i) breakage of polymer-water hydrogen bonding and (ii) polymer-polymer aggregation) at the molecular microenvironment during the cloud point generation was successfully probed via these parameters. It is demonstrated that, in comparison to the present techniques available for assessing the hydrophobic-hydrophilic switch over of simple stimuli-responsive polymers, Mueller matrix polarimetry offers an important advantage requiring a few hundred times dilute polymer solution (0.01 mg/mL, 1.1-1.4 μM) at a low-volume format.

  9. A Statistical-Mechanical Theory of Fibril Formation in Dilute Protein Solutions

    PubMed Central

    van Gestel, Jeroen; de Leeuw, Simon W.

    2006-01-01

    We outline a theoretical treatment that describes fibril formation in dilute protein solutions. For this, we combine a theory describing self-assembly and conformational transition with a description of the lateral association of linear chains. Our statistical-mechanical model is able to predict the mean degree of polymerization and the length of the fibrils and their precursors, as well as the weight fractions of the different aggregated species in solution. We find that there appear to exist two regimes as a function of concentration, and as a function of the free energies of protein association: one in which low-molecular weight compounds dominate and one in which the fibrils do. The transition between these regimes can be quite sharp, and becomes sharper as more filaments are allowed to associate into a single fibril. The fraction of fibrils consisting of less than the maximum allowed number of filaments turns out to be negligible, in agreement with experimental studies, where the fibril thickness is found to be practically monodisperse. In addition, we find that the description of the fibril ends has a large effect on the predicted fibril length. PMID:16603504

  10. A statistical-mechanical theory of fibril formation in dilute protein solutions.

    PubMed

    van Gestel, Jeroen; de Leeuw, Simon W

    2006-05-01

    We outline a theoretical treatment that describes fibril formation in dilute protein solutions. For this, we combine a theory describing self-assembly and conformational transition with a description of the lateral association of linear chains. Our statistical-mechanical model is able to predict the mean degree of polymerization and the length of the fibrils and their precursors, as well as the weight fractions of the different aggregated species in solution. We find that there appear to exist two regimes as a function of concentration, and as a function of the free energies of protein association: one in which low-molecular weight compounds dominate and one in which the fibrils do. The transition between these regimes can be quite sharp, and becomes sharper as more filaments are allowed to associate into a single fibril. The fraction of fibrils consisting of less than the maximum allowed number of filaments turns out to be negligible, in agreement with experimental studies, where the fibril thickness is found to be practically monodisperse. In addition, we find that the description of the fibril ends has a large effect on the predicted fibril length.

  11. A new method to determine the yield stress of diluted polymeric solutions

    NASA Astrophysics Data System (ADS)

    Soto, Enrique; Ruiz, Servando; Cordova Aguilar, Maria Soledad

    2012-11-01

    A new method to measure the yield stress for diluted polymeric solutions is presented. The tested solutions exhibit shear thinning behavior a once the critical yield stress is overcame. In rheology, these fluids are known as Herschel-Buckley. The yield stress phenomenon and its relation with bubble motion is an important issue for different industries, for example, personal care, paints and some others. As a result of the yield stress, small bubbles remain trapped in the fluid bulk, but above a critical volume, which is related with the characteristic yield stress, the bubbles flow in the liquid. In order to change the bubble volume, the liquid is placed in a cylindrical container whose pressure is decreased by a vacuum pump. The bubble growths as the pressure decreases and keeps its position until it reaches the critical volume. The bubble shape changes with volume and velocity, and a competition among surface, gravitational, inertial and viscous forces is discussed. The yield stress determined value is higher than the obtained from simple shear measurements due to the complex flow around the bubble.

  12. A single bubble path transition from spiral to zigzag in dilute surfactant solution

    NASA Astrophysics Data System (ADS)

    Tagawa, Yoshiyuki; Kawaguchi, Wataru; Funakubo, Ami; Takagi, Shu; Matsumoto, Yoichiro

    2007-11-01

    The surfactant effect on a single bubble motion is so important that it changes whole bubbly flow structures. One of the surfactant key effects is to decrease bubble rise velocity. This phenomenon is described as Marangoni effect which is quantitatively investigated by many experiments and numerical calculations of straight rising bubbles. Some other previous researches studied a bubble trajectory transition from a zigzag trajectory to spiral in super purified water (Mougin et al. 2002). However, the surfactant effect on this 3D motion bubbles is not enough investigated. To investigate it in detail, we measured trajectories of single bubbles rising in a tank of 1300mm height filled with dilute surfactant solution. We observed a bubble motion transition from spiral to zigzag, which is just reverse transition of trajectories in super purified water. Considering our other measurement results of bubble trajectories in super purified water, those in different surfactant solution, and a profile of bubble rise velocity, we think this interesting result is explained by surfactant concentration on a bubble surface. We will discuss its mechanism in detail in our presentation.

  13. An ab initio quantum mechanical charge field molecular dynamics simulation of a dilute aqueous HCl solution.

    PubMed

    Kritayakornupong, Chinapong; Vchirawongkwin, Viwat; Rode, Bernd M

    2010-06-01

    An ab initio quantum mechanical charge field (QMCF) molecular dynamics simulation has been performed to study the structural and dynamical properties of a dilute aqueous HCl solution. The solute molecule HCl and its surrounding water molecules were treated at Hartree-Fock level in conjunction with Dunning double-zeta plus polarization function basis sets. The simulation predicts an average H-Cl bond distance of 1.28 A, which is in good agreement with the experimental value. The H(HCl)...O(w) and Cl(HCl)...H(w) distances of 1.84 and 3.51 A were found for the first hydration shell. At the hydrogen site of HCl, a single water molecule is the most preferred coordination, whereas an average coordination number of 12 water molecules of the full first shell was observed for the chloride site. The hydrogen bonding at the hydrogen site of HCl is weakened by proton transfer reactions and an associated lability of ligand binding. Two proton transfer processes were observed in the QMCF MD simulation, demonstrating acid dissociation of HCl. A weak structure-making/breaking effect of HCl in water is recognized from the mean residence times of 2.1 and 0.8 ps for ligands in the neighborhood of Cl and H sites of HCl, respectively. Copyright 2009 Wiley Periodicals, Inc.

  14. Physical and chemical stability of reconstituted and diluted dexrazoxane infusion solutions.

    PubMed

    Zhang, Yan-Ping; Myers, Alan L; Trinh, Van A; Kawedia, Jitesh D; Kramer, Mark A; Benjamin, Robert S; Tran, Hai T

    2014-02-01

    Dexrazoxane is used clinically to prevent anthracycline-associated cardiotoxicity. Hydrolysis of dexrazoxane prior to reaching the cardiac membranes severely hampers its mode of action; therefore, degradation during the preparation and administration of intravenous dexrazoxane admixtures demands special attention. Moreover, the ongoing national shortage of one dexrazoxane formulation in the United States has forced pharmacies to dispense other commercially available dexrazoxane products. However, the manufacturers' limited stability data restrict the flexibility of dexrazoxane usage in clinical practice. The aims of this study are to determine the physical and chemical stability of reconstituted and diluted solutions of two commercially available dexrazoxane formulations. The stability of two dexrazoxane products, brand and generic name, in reconstituted and intravenous solutions stored at room temperature without light protection in polyvinyl chloride bags was determined. The concentrations of dexrazoxane were measured at predetermined time points up to 24 h using a validated reversed phase high-performance liquid chromatography with ultraviolet detection assay. Brand (B-) and generic (G-) dexrazoxane products, reconstituted in either sterile water or 0.167 M sodium lactate (final concentration of 10 mg/mL), were found stable for at least to 8 h. Infusion solutions of B-dexrazoxane, prepared according to each manufacturer's directions, were stable for at least 24 h and 8 h at 1 mg/mL and 3 mg/mL, respectively. Infusion solutions of G-dexrazoxane, prepared in either 5% dextrose or 0.9% sodium chloride following the manufacturer's guidelines, were also stable for at least 24 h and 8 h at 1 mg/mL and 3 mg/mL, respectively. All tested solutions were found physically stable up to 24 h at room temperature. The stability of dexrazoxane infusion solutions reported herein permits advance preparation of dexrazoxane intravenous admixtures, facilitating

  15. The enthalpies of solution of VOCl3 in dilute solutions of sodium hydroxide and the standard enthalpy of formation of liquid VOCl3

    NASA Astrophysics Data System (ADS)

    Dmitrieva, N. G.; Romodanovskii, P. A.; Gridchin, S. N.; Vorob'ev, P. N.

    2010-01-01

    The enthalpies of solution of liquid vanadium oxytrichloride in dilute solutions of sodium hydroxide were determined by direct calorimetric measurements at 298.15 K and ionic strength values I = 0.3, 0.5, and 1.0 (NaClO4). The experimental data were used to calculate the standard enthalpy of formation of liquid VOCl3.

  16. Enthalpy of solution of VOCl3 in dilute sodium hydroxide solutions and the standard enthalpy of formation of the HVO{4/2-} ion

    NASA Astrophysics Data System (ADS)

    Romodanovskii, P. A.; Vorob'ev, P. N.; Dmitrieva, N. G.; Gridchin, S. N.

    2007-12-01

    The calorimetric enthalpies of solution of liquid vanadium oxytrichloride in dilute sodium hydroxide solutions were measured at 298.15 K and ionic strengths I = 0.5, 1.0, or 1.5 (NaClO4). The standard enthalpy of formation of the HVO{4/2-} ion was calculated from the measured data.

  17. Effect of ethanol, temperature, and gas flow rate on volatile release from aqueous solutions under dynamic headspace dilution conditions.

    PubMed

    Tsachaki, Maroussa; Gady, Anne-Laure; Kalopesas, Michalis; Linforth, Robert S T; Athès, Violaine; Marin, Michele; Taylor, Andrew J

    2008-07-09

    On the basis of a mechanistic model, the overall and liquid mass transfer coefficients of aroma compounds were estimated during aroma release when an inert gas diluted the static headspace over simple ethanol/water solutions (ethanol concentration = 120 mL x L(-1)). Studied for a range of 17 compounds, they were both increased in the ethanol/water solution compared to the water solution, showing a better mass transfer due to the presence of ethanol, additively to partition coefficient variation. Thermal imaging results showed differences in convection of the two systems (water and ethanol/water) arguing for ethanol convection enhancement inside the liquid. The effect of ethanol in the solution on mass transfer coefficients at different temperatures was minor. On the contrary, at different headspace dilution rates, the effect of ethanol in the solution helped to maintain the volatile headspace concentration close to equilibrium concentration, when the headspace was replenished 1-3 times per minute.

  18. The effect of divalent salt in chondroitin sulfate solutions

    SciTech Connect

    Aranghel, D.; Badita, C. R.; Radulescu, A.; Moldovan, L.; Craciunescu, O.; Balasoiu, M.

    2016-03-25

    Chondroitin-4 sulfate (CS4) is the main glycosaminoglycan extracted from bovine trachea. CS4 play an important role in osteoarthritis treatment, anticoagulant activity, reduces the degradation of cartilage matrix components, reduces necrosis and apoptosis of chondrocytes and reduces the activity of collagenase. Chondroitin sulfate is also responsible for proteoglycans degradation. Chondroitin sulfate can bind calcium ions with different affinities, depending on their sulfation position. The purpose of this study was to determine the structural properties and the influence of Ca{sup 2+} cations. We carried out measurements on CS4 solutions and mixtures of liquid CS4 with Ca{sup 2+} by Small-Angle Neutron Scattering (SANS). CS4 have a mass fractal behavior and the addition of a salt (CaCl{sub 2}) in CS4 solutions generates the appearance of a correlation peak due to local ordering between adjacent chains with inter-chain distances between 483 Å and 233 Å for a calcium concentration of 0.01% w/w.

  19. The effect of divalent salt in chondroitin sulfate solutions

    NASA Astrophysics Data System (ADS)

    Aranghel, D.; Badita, C. R.; Radulescu, A.; Moldovan, L.; Craciunescu, O.; Balasoiu, M.

    2016-03-01

    Chondroitin-4 sulfate (CS4) is the main glycosaminoglycan extracted from bovine trachea. CS4 play an important role in osteoarthritis treatment, anticoagulant activity, reduces the degradation of cartilage matrix components, reduces necrosis and apoptosis of chondrocytes and reduces the activity of collagenase. Chondroitin sulfate is also responsible for proteoglycans degradation. Chondroitin sulfate can bind calcium ions with different affinities, depending on their sulfation position. The purpose of this study was to determine the structural properties and the influence of Ca2+ cations. We carried out measurements on CS4 solutions and mixtures of liquid CS4 with Ca2+ by Small-Angle Neutron Scattering (SANS). CS4 have a mass fractal behavior and the addition of a salt (CaCl2) in CS4 solutions generates the appearance of a correlation peak due to local ordering between adjacent chains with inter-chain distances between 483 Å and 233 Å for a calcium concentration of 0.01% w/w.

  20. Excess entropy of water in a supercooled solution of salt

    NASA Astrophysics Data System (ADS)

    Gallo, P.; Corradini, D.; Rovere, M.

    2011-12-01

    We consider the relationship between the excess entropy and anomalies of water. We investigate by molecular dynamics simulations the thermodynamic region of supercooled water and a supercooled aqueous solution with NaCl at a salt concentration of 0.67 mol kg-1. The TIP4P potential model displays, as already established, in pure water and in solution a phase diagram with a liquid-liquid critical point. We explore how the two-body excess entropy calculated from the radial distribution functions is an indicator of density and structural anomalies of supercooled liquid water, both in the pure system and in the NaCl(aq). The two-body excess entropy shows a peculiar behaviour associated with the density anomaly and structural changes in water as revealed by the radial distribution functions. The signature of a change in the structural relaxation of water from fragile to strong is also found by examining the behaviour of the excess entropy at decreasing temperature.

  1. Sodium chloride crystallization from drying drops of albumin-salt solutions with different albumin concentrations

    NASA Astrophysics Data System (ADS)

    Yakhno, T. A.

    2015-11-01

    The salt nature of crystalline structures resulting from drying albumin-salt solutions with a low (<1 wt %) and high (7 and 9 wt %) concentration of albumin and a NaCl concentration kept at a physiological level (0.9 wt %) is experimentally substantiated. Such a conclusion is drawn from the dynamics of phase transitions, morphological studies, and differences between the physicochemical properties of albumin and salt. Obtained data give a deeper insight into the albumin and salt distributions in drying liquids.

  2. Adsorption of n-butanol from dilute aqueous solution with grafted calixarenes.

    PubMed

    Thompson, Anthony B; Cope, Sydney J; Swift, T Dallas; Notestein, Justin M

    2011-10-04

    Materials were synthesized for the recovery of n-butanol from dilute aqueous solutions, as may be useful for applications in biofuel-water separations. These materials are composed of hydrophobic, cavity-containing calixarenes covalently bound directly to porous, hydrophilic silica supports through a Si linker atom rather than a flexible organic linker, as is common, at surface coverages of up to ∼0.25 calixarenes/nm(2) (∼250 μmol calix/g matl). The calixarene ring size, upper rim groups, bridging group (calixarene vs thiacalixarene), and surface density were varied. The materials were characterized by NMR, UV-vis, and TGA. The absolute butanol uptake reached ∼0.16 mmol butanol per gram of material at equilibrium concentrations below 0.12 M and increased monotonically with the calixarene surface density. The background adsorption onto the silica surface was small at high calixarene loading. At 298 K, the free energy of adsorption in the calixarene cavities became more favorable by 3 kJ/mol as the surface area of the hydrophobic calixarene upper rim groups increased from H to methyl to tert-butyl, consistent with adsorption driven by van der Waals interactions. A thiacalix[4]arene-SiO(2) material, containing polarizable sulfur bridges and a larger, more conformationally mobile calixarene structure, had slightly stronger adsorption still. All materials except this thiacalixarene exhibited fully reversible adsorption into solution. As a representative material, the adsorption of n-butanol from aqueous solution at a tert-butylcalix[4]arene site was accompanied by a negligible enthalpy change but a small, favorable entropy change of +50 ± 20 J/mol/K, indicating that adsorption is driven by desolvation. Butanol desorbed from tert-butylcalix[4]arene materials at ∼150 °C into the gas phase, well within the range of stability of calixarenes (<300 °C), indicating that these materials have promise as regenerable adsorbents.

  3. Formation of globules and aggregates of DNA chains in DNA/polyethylene glycol/monovalent salt aqueous solutions.

    PubMed

    Kawakita, H; Uneyama, T; Kojima, M; Morishima, K; Masubuchi, Y; Watanabe, H

    2009-09-07

    It has been known that giant DNA shows structural transitions in aqueous solutions under the existence of counterions and other polymers. However, the mechanism of these transitions has not been fully understood. In this study, we directly observed structures of probed (dye-labeled), dilute DNA chains in unprobed DNA/polyethylene glycol (PEG)/monovalent salt (NaCl) aqueous solutions with fluorescent microscopy to examine this mechanism. Specifically, we varied the PEG molecular weight and salt concentration to investigate the effect of competition between the depletion and electrostatic interactions on the coil-globule transition and the aggregate formation. It was found that the globules coexist with the aggregates when the unprobed DNA chains have a concentration higher than their overlap concentration. We discuss the stability of the observed structures on the basis of a free energy model incorporating the attractive depletion energy, the repulsive electrostatic energy, and the chain bending energy. This model suggested that both of the globules and aggregates are more stable than the random coil at high salt concentrations/under existence of PEG and the transition occurs when the depletion interaction overwhelms the electrostatic interaction. However, the coexistence of the globule and aggregate was not deduced from the thermodynamic model, suggesting a nonequilibrium aspect of the DNA solution and metastabilities of these structures. Thus, the population ratio of globules and aggregates was also analyzed on the basis of a kinetic model. The analysis suggested that the depletion interaction dominates this ratio, rationalizing the coexistence of globules and aggregates.

  4. Geotechnical factors and guidelines for storage of compressed air in solution-mined salt cavities

    SciTech Connect

    Allen, R.D.; Doherty, T.J.; Thoms, R.L.

    1982-05-01

    The state of knowledge about utilization of solution-mined salt cavities for CAES including laboratory experiments, numerical modeling, field characterization, solution mining experience, and operating parameters is outlined in this report. Topics evaluated in recent studies include: cavern geometry and size; long-term creep and creep rupture of rock salt; effects of pressure and temperature loading rates; low frequency fatigue; progressive deterioration of salt fabric with possible air penetration; cavern monitoring methods; and salt properties at nonambient conditions. Currently, the only CAES operational facility in the world is located at Huntorf, West Germany. This CAES facility uses two solution-mined salt caverns for air storage and has been operating successfully for more than 2 years. Stability criteria for solution-mined salt caverns from the Huntorf facility and recent field and laboratory studies are included in this report.

  5. Novel Superdielectric Materials: Aqueous Salt Solution Saturated Fabric

    PubMed Central

    Phillips, Jonathan

    2016-01-01

    The dielectric constants of nylon fabrics saturated with aqueous NaCl solutions, Fabric-Superdielectric Materials (F-SDM), were measured to be >105 even at the shortest discharge times (>0.001 s) for which reliable data could be obtained using the constant current method, thus demonstrating the existence of a third class of SDM. Hence, the present results support the general theoretical SDM hypothesis, which is also supported by earlier experimental work with powder and anodized foil matrices: Any material composed of liquid containing dissolved, mobile ions, confined in an electrically insulating matrix, will have a very high dielectric constant. Five capacitors, each composed of a different number of layers of salt solution saturated nylon fabric, were studied, using a galvanostat operated in constant current mode. Capacitance, dielectric constant, energy density and power density as a function of discharge time, for discharge times from ~100 s to nearly 0.001 s were recorded. The roll-off rate of the first three parameters was found to be nearly identical for all five capacitors tested. The power density increased in all cases with decreasing discharge time, but again the observed frequency response was nearly identical for all five capacitors. Operational limitations found for F-SDM are the same as those for other aqueous solution SDM, particularly a low maximum operating voltage (~2.3 V), and dielectric “constants” that are a function of voltage, decreasing for voltages higher than ~0.8 V. Extrapolations of the present data set suggest F-SDM could be the key to inexpensive, high energy density (>75 J/cm3) capacitors. PMID:28774037

  6. Distribution coefficients of vitamin B2 in hydrophilic organic solvent-aqueous salt solution systems

    NASA Astrophysics Data System (ADS)

    Korenman, Ya. I.; Mokshina, N. Ya.; Zykov, A. V.

    2010-03-01

    Distribution coefficients of vitamin B2 in hydrophilic solvent ( n-butanol, isopropanol, acetone, ethyl acetate, and their mixtures)-aqueous salt (potassium chloride, sodium fluoride, and ammonium sulfate salting-out agents) solution systems were calculated. The synergic effect and optimum proportions of components in the solvent mixture for efficient extraction of vitamin B2 from aqueous solutions were established.

  7. Viscometric Studies in Dilute Solution Mixtures of Chitosan and Microcrystalline Chitosan with Poly(vinyl alcohol).

    PubMed

    Lewandowska, Katarzyna

    2013-01-01

    The viscosity behavior of aqueous mixtures formed by a polyelectrolyte (A) and a neutral polymer (B), such as chitosan/poly(vinyl alcohol) (Ch/PVA) and microcrystalline chitosan/poly(vinyl alcohol) (MCCh/PVA), have been investigated at 25 °C. The intrinsic viscosity and the viscosity interaction parameter of each polymer in 0.1 mol·dm(-3) CH3COOH/0.2 mol·dm(-3) NaCl solution as well as the ternary systems (polymer A/polymer B/solvent) have been determined and have served for estimation of the miscibility of different polymer mixtures by means of the method of classical dilution. By comparing the experimental and ideal viscosity data it is clearly seen that the satisfaction of the miscibility criterion depends on the definition of the ideal parameter [Formula: see text]. If the [Formula: see text] parameter is defined according to the Krigbaum-Wall criterion and Garcia criterion, the investigated blends of Ch/PVA satisfy the miscibility criterion. In the case of MCCh/PVA blends, the polymeric components show poor miscibility. Additionally, the viscosity results show that the degree of miscibility depends on the molecular weight of chitosan and on the degree of PVA hydrolysis.

  8. Chain-length heterogeneity allows for the assembly of fatty acid vesicles in dilute solutions.

    PubMed

    Budin, Itay; Prwyes, Noam; Zhang, Na; Szostak, Jack W

    2014-10-07

    A requirement for concentrated and chemically homogeneous pools of molecular building blocks would severely restrict plausible scenarios for the origin of life. In the case of membrane self-assembly, models of prebiotic lipid synthesis yield primarily short, single-chain amphiphiles that can form bilayer vesicles only at very high concentrations. These high critical aggregation concentrations (cacs) pose significant obstacles for the self-assembly of single-chain lipid membranes. Here, we examine membrane self-assembly in mixtures of fatty acids with varying chain lengths, an expected feature of any abiotic lipid synthesis. We derive theoretical predictions for the cac of mixtures by adapting thermodynamic models developed for the analogous phenomenon of mixed micelle self-assembly. We then use several complementary methods to characterize aggregation experimentally, and find cac values in close agreement with our theoretical predictions. These measurements establish that the cac of fatty acid mixtures is dramatically lowered by minor fractions of long-chain species, thereby providing a plausible route for protocell membrane assembly. Using an NMR-based approach to monitor aggregation of isotopically labeled samples, we demonstrate the incorporation of individual components into mixed vesicles. These experiments suggest that vesicles assembled in dilute, mixed solutions are depleted of the shorter-chain-length lipid species, a finding that carries implications for the composition of primitive cell membranes.

  9. Influence of second virial coefficient and persistence length on dilute solution polymer conformation.

    PubMed

    Haidar Ahmad, Imad A; Striegel, André M

    2011-02-01

    The effect of different types of short- and long-range intrachain interactions along the polymeric backbone on the persistence length of a polymer, as well as on other properties such as solvation (characterized by the second virial coefficient), dilute solution conformation, specific refractive index increment, and intrinsic viscosity, were studied using multi-detector size-exclusion chromatography and off-line techniques. The polymers in this study, namely, polystyrene (PS), poly(vinyl chloride) (PVC), and poly(p-vinylbenzyl chloride) (PpVBC), were chosen based on intrachain interactions specific to each, intrachain repulsion in PVC, attraction in PS, and hindered attraction in PpVBC, and also based on a coincidence in molar mass averages and distributions between the polymers. The latter allowed polymeric properties of the three polymers to be compared to each other at the same molar mass and/or degree of polymerization. From the comparisons emerged the effects of intrachain repulsion between consecutive monomers and of the second virial coefficient on chain stiffness and solvation. The increase in the second virial coefficient corresponded to an increase in both polymer solvation and rigidity, while increased intrachain repulsion between consecutive monomers increased polymer solvation while decreasing chain rigidity.

  10. Lagrange thermodynamic potential and intrinsic variables for He-3 He-4 dilute solutions

    NASA Technical Reports Server (NTRS)

    Jackson, H. W.

    1983-01-01

    For a two-fluid model of dilute solutions of He-3 in liquid He-4, a thermodynamic potential is constructed that provides a Lagrangian for deriving equations of motion by a variational procedure. This Lagrangian is defined for uniform velocity fields as a (negative) Legendre transform of total internal energy, and its primary independent variables, together with their thermodynamic conjugates, are identified. Here, similarities between relations in classical physics and quantum statistical mechanics serve as a guide for developing an alternate expression for this function that reveals its character as the difference between apparent kinetic energy and intrinsic internal energy. When the He-3 concentration in the mixtures tends to zero, this expression reduces to Zilsel's formula for the Lagrangian for pure liquid He-4. An investigation of properties of the intrinsic internal energy leads to the introduction of intrinsic chemical potentials along with other intrinsic variables for the mixtures. Explicit formulas for these variables are derived for a noninteracting elementary excitation model of the fluid. Using these formulas and others also derived from quantum statistical mechanics, another equivalent expression for the Lagrangian is generated.

  11. A-type crystals from dilute solutions of short amylose chains.

    PubMed

    Montesanti, Nicole; Véronèse, Gabrielle; Buléon, Alain; Escalier, Pierre-Claude; Kitamura, Shinichi; Putaux, Jean-Luc

    2010-11-08

    Model A-type amylose single crystals were prepared by recrystallizing dextrins from acid-hydrolyzed native starch and narrow fractions of short chains of enzymatically synthesized amylose, in dilute water/acetone solutions. In most cases, spindle-shaped crystals with a sharp, round or flat apical end were formed, organized in rosettes or fan-like assemblies. The morphology and crystal size were shown to strongly depend on the average degree of polymerization (DP), distribution width (DW), and degree of branching of the chains. The largest and most clearly faceted single crystals were prepared using fractions of synthetic amylose. Typically, 5-10 μm long crystals were obtained from fractions with 17 ≤ DP ≤ 20 and DW ≤ 8. Chains with DP > 40 and a high polydispersity formed ill-defined networks of smaller crystallites. Fractions of branched and more polydisperse limit dextrins yielded crystals smaller than those obtained from narrow fractions of synthetic amylose. The morphological analysis of faceted single crystals combined with electron diffraction data confirmed that the double helices were oriented along the long dimension of the crystal and packed into lamellae with a parallelogram cross section defined by the a and b directions of the monoclinic unit cell of A-amylose. The lamellae are stacked along the c-axis that is oriented parallel but opposite to the growth direction of the crystal.

  12. High-Yield Production of Levulinic Acid from Pretreated Cow Dung in Dilute Acid Aqueous Solution.

    PubMed

    Su, Jialei; Shen, Feng; Qiu, Mo; Qi, Xinhua

    2017-02-14

    Agricultural waste cow dung was used as feedstock for the production of a high value-added chemical levulinic acid (LA) in dilute acid aqueous solutions. A high LA yield of 338.9 g/kg was obtained from the pretreated cow dung, which was much higher than that obtained from the crude cow dung (135 g/kg), mainly attributed to the breakage of the lignin fraction in the lignocellulose structure of the cow dung by potassium hydroxide (KOH) pretreatment, and thus enhanced the accessibility of cow dung to the acid sites in the catalytic reaction. Meanwhile, another value-added chemical formic acid could be obtained with a yield of ca. 160 g/kg in the process, implying a total production of ca. 500 g/kg yield for LA and formic acid from the pretreated cow dung with the proposed process. The developed process was shown to be tolerant to high initial substrate loading with a satisfied LA yield. This work provides a promising strategy for the value-increment utilization of liglocellulosic agricultural residues.

  13. Modeling of electro-osmosis of dilute electrolyte solutions in silica microporous media

    NASA Astrophysics Data System (ADS)

    Wang, Moran; Kang, Qinjun; Viswanathan, Hari; Robinson, Bruce A.

    2010-10-01

    Physicochemical transport due to electro-osmosis of dilute electrolyte solutions (<1 × 10-3 mol/L) through microporous media with granular random microstructures has been modeled in this work by our three-step numerical framework. First, the three-dimensional microstructures of porous media are reproduced by a random generation growth method. Second, the effects of chemical adsorption and electrical dissociation at the solid-liquid interfaces are modeled to determine the electrical boundary conditions, which vary with the ionic concentration, pH, and temperature. Finally, the nonlinear governing equations for electrokinetic transport are solved using a highly efficient lattice Poisson-Boltzmann algorithm. The simulation results indicate that the electro-osmotic permeability through the granular microporous media increases monotonically with the porosity, ionic concentration, pH, and temperature. When the surface electric potential is higher than about -50 mV, the electro-osmotic permeability exponentially increases with the electric potential. The electro-osmotic permeability increases with the bulk ionic concentration even though the surface zeta potential decreases correspondingly, which deviates from the conclusions based on the thin layer model. The electro-osmotic permeability increases exponentially with pH and linearly with temperature. The present modeling results improve our understanding of hydrodynamic and electrokinetic transport in geophysical systems and help guide the design of porous electrodes in microenergy systems.

  14. Effect of hydrodynamic correlations on the dynamics of polymers in dilute solution

    NASA Astrophysics Data System (ADS)

    Huang, Chien-Cheng; Gompper, Gerhard; Winkler, Roland G.

    2013-04-01

    We analyze the effect of time-dependent hydrodynamic interactions on the dynamics of flexible polymers in dilute solution. In analytical calculations, the fluctuating hydrodynamics approach is adopted to describe the fluid, and a Gaussian model to represented the polymer. Simulations are performed exploiting the multiparticle collision dynamics approach, a mesoscale hydrodynamic simulation technique, to explicitly describe the fluid. Polymer center-of-mass velocity correlation functions are calculated for various polymer lengths. Similarly, segment mean square displacements are discussed and polymer diffusion coefficients are determined. Particular attention is paid to the influence of sound propagation on the various properties. The simulations reveal a strong effect of hydrodynamic interactions. Specifically, the time dependence of the center-of-mass velocity correlation functions is determined by polymer properties over a length-dependent time window, but are asymptotically solely governed by fluid correlations, with a long-time tail decaying as t-3/2. The correlation functions are heavily influenced by sound modes for short polymers, an effect which gradually disappears with increasing polymer length. We find excellent agreement between analytical and simulation results. This allows us to provide a theory-based asymptotic value for the polymer diffusion coefficient in the limit of large system sizes, which is based on a single finite-system-size simulation.

  15. Effect of cyclic chain architecture on properties of dilute solutions of polyethylene from molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Jang, Seung Soon; ćaǧin, Tahir; Goddard, William A.

    2003-07-01

    We have used molecular dynamics methods to investigate the effects of cyclic chain architecture on the properties of dilute solutions. In order to include solvent effects in estimating these properties, we use a van der Waals scaling factor determined for each solvent by matching to the theta condition. We predict that the theta temperature (θ) of cyclic PE (c-PE) is ˜10% lower than for the linear case (l-PE). This can be compared to the experimental results for polystyrene (PS), where θ for cyclic PS is 2% lower. For conditions corresponding to n-pentane solvent, we predict that cyclic/linear is 0.59 for all temperatures above 350 K. The deviation from the ratio of 0.50-0.53 expected from analytic theory is due to the competition between chain stiffness and excluded volume effects. To calculate the intrinsic viscosity of c-PE and l-PE we extended the Bloomfield-Zimm type theory to include chain stiffness corrections. We find that for the theta temperature, the ratio of viscosities for c-PE and l-PE is 0.71, which is 7% higher than the value of 0.66 from the freely jointed chain model. This difference is caused by the larger value of cyclic/linear from the simulations.

  16. Elastic effects of dilute polymer solution on bubble generation in a microfluidic flow-focusing channel

    NASA Astrophysics Data System (ADS)

    Kim, Dong Young; Shim, Tae Soup; Kim, Ju Min

    2017-05-01

    Recently, two-phase flow in microfluidics has attracted much attention because of its importance in generating droplets or bubbles that can be used as building blocks for material synthesis and biological applications. However, there are many unresolved issues in understanding droplet and bubble generation processes, especially when complex fluids are involved. In this study, we investigated elastic effects on bubble generation processes in a flow-focusing geometry and the shapes of the produced bubbles flowing through a microchannel. We used dilute polymer solutions with nearly constant shear viscosities so that the shear-thinning effects on bubble generation could be precluded. We observed that a very small amount of polymer (poly(ethylene oxide) at O(10) ppm) significantly affects bubble generation. When the polymer was added to a Newtonian fluid, the fluctuation in bubble size increased notably, which was attributed to the chaotic flow dynamics in the flow-focusing region. In addition, it was demonstrated that the bubbles were thinner along the minor axis in the viscoelastic fluid than they were in the Newtonian fluid. We expect that the current results will contribute to understanding the dynamics of two-phase flow in microchannels and the design and operation of the microfluidic devices to generate microbubbles.

  17. Self-assembly behavior of AB/AC diblock copolymer mixtures in dilute solution.

    PubMed

    Zhuang, Ying; Lin, Jiaping; Wang, Liquan; Zhang, Liangshun

    2009-02-19

    The self-assembly behavior of AB/AC amphiphilic diblock copolymer mixtures in dilute solution was studied by a real-space-implemented self-consistent field theory in three dimensions. The AB and AC copolymers have a common hydrophobic block A but different hydrophilic blocks B and C. Two cases were studied: one in which copolymers AB and AC have same hydrophobic and hydrophilic block lengths and one in which copolymers AB and AC have different hydrophobic and hydrophilic block lengths. It was found that the two copolymers can cooperatively self-assemble into hybrid aggregates. The morphologies of the formed aggregates were found to be dependent on the mixture ratio and the interaction between the B and C blocks. For the AB/AC copolymers with different hydrophobic and hydrophilic lengths, chain segregation was found in the formed hybrid aggregates. Based on the obtained calculation results, phase diagrams as functions of the mixture ratio and interaction between the B and C blocks were constructed.

  18. Regeneration of basic sorbents used in the recovery of acetic acid from dilute aqueous solution

    SciTech Connect

    Ng, M.; King, C.J.

    1988-10-01

    The regeneration of basic sorbents used in the recovery of dilute aqueous acetic acid was explored. The regeneration methods studied were solvent leaching and vaporization. The resins used were weak base anion exchange resins, Dow Chemical Company's Dowex MWA-1 (tertiary amine resin) and Celanese Corporation's Aurorez (polybenzimidazole resin). The equilibrium between the aqueous acetic acid solution and the resins was measured in batch experiments. The composite isotherms calculated from these data wee comparable to those of other researchers. Methanol was used as the solvent to leach acetic acid from the resin. The equilibrium data from the batch experiments were used in the local-equilibrium theory of fixed-bed devices to model the desorption behavior of acetic acid in methanol. Both sorption and desorption equilibrium data were used in chemical complexation models to obtain sorption affinities and capacities of the resin for acetic acid. However, the amount of methanol needed to achieve a high degree of regeneration was too large to be economical. 15 refs., 25 figs., 3 tabs.

  19. Recovery of propylene glycol from dilute aqueous solutions via reversible reaction with aldehydes

    SciTech Connect

    Broekhuis, R.R.; Lynn, S.; King, C.J. )

    1994-12-01

    The recovery of propylene glycol from dilute aqueous solutions via reaction with formaldehyde to form 4-methyl-1,3-dioxolane or with acetaldehyde to form 2,4-dimethyl-1,3-dioxolane was studied experimentally. The equilibrium and kinetics of the reaction with formaldehyde were studied in systems catalyzed by Amberlite IR-120 ion exchange resin. The equilibrium constant ranged from 5.9 to 8.7 in the temperature range from 25 to 85 C, with no obvious trend with respect to temperature. The kinetics was found to be first-order in the concentrations of propylene glycol, formaldehyde, and Amberlite IR-120, with an activation energy of 102 kJ/mol. In the reaction with acetaldehyde, the equilibrium constant decreased from 18.1 at 40 C to 8.5 at 83 C. The kinetics was faster than with formaldehyde. The volatilities of 4-methyl-1,3-dioxolane and 2,4-dimethyl-1,3-dioxolane relative to water were 100 and 33, respectively. Of several solvents screened, aromatic hydrocarbons exhibited the highest distribution of 2,4-dimethyl-1,3-dioxolane from the aqueous into the organic phase. Recovery of propylene glycol by reactive distillation with formaldehyde or acetaldehyde is hampered by unfavorable chemical and phase equilibria. A process combining reaction and extraction into an organic solvent appears to be more attractive and substantially reduces the energy requirement, in comparison with a triple-effect evaporation process.

  20. A novel method of non-violent dissolution of sodium metal in a concentrated aqueous solution of Epsom salt

    NASA Astrophysics Data System (ADS)

    Lakshmanan, A. R.; Prasad, M. V. R.; Ponraju, D.; Krishnan, H.

    2004-10-01

    A new technique of non-violent and fast dissolution of sodium metal in a concentrated aqueous solution of Epsom salt (MgSO4.7H2O) at room temperature (RT) has been developed. The dissolution process is mildly exothermic but could be carried out even in a glass beaker in air under swift stirring condition. The reaction products consist of mixed salts of MgSO4 and Na2SO4 as well as Mg(OH)2 which are only mildly alkaline and hence are non-corrosive and non-hazardous unlike NaOH. A 50 mL solution having Epsom salt concentration of 2 M was found to give the optimal composition for disposal of 1 g of sodium. Supersaturated (>2.7 M), as well as dilute (<1.1 M) solutions, however, cause violent reactions and hence should be avoided. Repeated sodium dissolution in Epsom solution produced a solid waste of 4.7 g per g of sodium dissolved which is comparable with the waste (4 g) produced in 8 M NaOH solution. A 1.4 M Epsom solution sprayed with a high-pressure jet cleaner at RT in air easily removed the sodium blocked inside a metal pipe made of mild steel. The above jet also dissolved peacefully residual sodium collected on the metal tray after a sodium fire experiment. No sodium fire or explosion was observed during this campaign. The Epsom solution spray effectively neutralized the minor quantity of sodium aerosol produced during this campaign. This novel technique would hence be quite useful for draining sodium from fast breeder reactor components and bulk processing of sodium as well as for sodium fire fighting.

  1. Controlled formation of ag nanoparticles by means of long-chain sodium polyacrylates in dilute solution.

    PubMed

    Huber, Klaus; Witte, Thomas; Hollmann, Jutta; Keuker-Baumann, Susanne

    2007-02-07

    A new tool is presented to control formation of Ag nanoparticles. Small amounts of silver ions were added to dilute solutions of long-chain sodium polyacrylates (NaPA). Four NaPA samples covering a molar mass regime of 97 kD < or = Mw < or = 650 kD have been used. With amounts of added Ag(+) as low as 1-2% of the COO(-) groups of the polyanionic chains, significant changes could already be induced in the NaPA coils with 650 kD. If the NaPA concentration was kept below 0.1 g/L, the coils with 650 kD exhibited a significant coil shrinking in stable solutions. At larger NaPA concentrations, addition of Ag+ initiates an aggregation of the polyacrylate coils toward compact structures. Coil shrinking and aggregation was revealed by means of time-resolved static light scattering. If exposed to UV-radiation, small Ag particles formed within the shrunken anionic polyacrylate coils. The Ag nanoparticles were identified by means of an enhanced light scattering and a characteristic plasmon absorption band around 410 nm. No such Ag particle formation could be observed even at 5 times larger concentrations of Ag(+) and NaPA if the two smallest polyacrylate samples have been used under otherwise equal conditions. This molar mass sensitive response of NaPA to Ag(+)-addition suggests an interesting phenomenon: if the coil size of the NaPa chains, which act as Ag(+) collectors, is large enough, local Ag(+) concentration in these coil-shaped Ag(+) containers exceeds a critical value, and irradiation with UV generates Ag nanoparticles.

  2. Aggregation behavior of triple helical polysaccharide with low molecular weight in diluted aqueous solution.

    PubMed

    Zhang, Yangyang; Li, Sheng; Zhang, Lina

    2010-04-22

    It has been proven in our previous work that the lentinan triple helical chains with high weight-average molecular weight (M(w) = 1.71 x 10(6)) formed easily a self-entangle one, and no ordered aggregates were detected. In the present work, we used the ultrasonic method to degrade the lentinan triple helical chains to obtain a sample with a mean value of M(w) approximately 5.0 x 10(5) g/mol. Subsequently, its dilute aqueous solution properties were studied by dynamic light scattering (DLS). The relaxation time distributions exhibited two modes (fast and slow) with different relaxation time scales. The fast mode was attributed to the relaxation of an individual triple helical lentinan, whereas the slow mode indicated the formation of large aggregates. On the basis of the scattering wave vector dependencies for the scattering intensity and for the amplitudes and characteristic times associated with the relaxation modes, the molecular parameters were calculated by combing static LS with DLS. The values of the radius of gyration for individuals (R(g)(indi)) and aggregates (R(g)(agg)) were 48.2 and 75.4 nm, and those of the hydrodynamic radius for individuals (R(h)(indi)) and aggregates (R(h)(agg)) were 14.9 and 98.4 nm, respectively. Furthermore, the structure-sensitive dimensionless parameter of individuals (rho(indi) = 3.23) and aggregates (rho(agg) = 0.766) indicated that the individual triple helical chains were stiff, whereas the aggregates existed as compact clusters. The aggregates consisted of short triple helical chains by packing close to form "faggot-like" assembly, and the ordered aggregates (near 10%) coexisted with the predominant triple helical chain in the aqueous solution. Atomic force microscopy provided straightforward evidence on the shape of the triple helical chains and their aggregates in water.

  3. A quasichemical approach for protein-cluster free energies in dilute solution

    NASA Astrophysics Data System (ADS)

    Young, Teresa M.; Roberts, Christopher J.

    2007-10-01

    Reversible formation of protein oligomers or small clusters is a key step in processes such as protein polymerization, fibril formation, and protein phase separation from dilute solution. A straightforward, statistical mechanical approach to accurately calculate cluster free energies in solution is presented using a cell-based, quasichemical (QC) approximation for the partition function of proteins in an implicit solvent. The inputs to the model are the protein potential of mean force (PMF) and the corresponding subcell degeneracies up to relatively low particle densities. The approach is tested using simple two and three dimensional lattice models in which proteins interact with either isotropic or anisotropic nearest-neighbor attractions. Comparison with direct Monte Carlo simulation shows that cluster probabilities and free energies of oligomer formation (ΔGi0) are quantitatively predicted by the QC approach for protein volume fractions ˜10-2 (weight/volume concentration ˜10gl-1) and below. For small clusters, ΔGi0 depends weakly on the strength of short-ranged attractive interactions for most experimentally relevant values of the normalized osmotic second virial coefficient (b2*). For larger clusters (i ≫2), there is a small but non-negligible b2* dependence. The results suggest that nonspecific, hydrophobic attractions may not significantly stabilize prenuclei in processes such as non-native aggregation. Biased Monte Carlo methods are shown to accurately provide subcell degeneracies that are intractable to obtain analytically or by direct enumeration, and so offer a means to generalize the approach to mixtures and proteins with more complex PMFs.

  4. Aggregation in dilute aqueous tert-butyl alcohol solutions: insights from large-scale simulations.

    PubMed

    Gupta, Rini; Patey, G N

    2012-07-21

    of the possible nature of microheterogeneity in dilute TBA-water solutions, and of the associated long correlation lengths. It is clear that system size can be a very important factor in simulations of these solutions, and must be taken into account in the evaluation and development of TBA-water force fields.

  5. THE INACTIVATION OF DILUTE SOLUTIONS OF CRYSTALLINE TRYPSIN BY X-RADIATION

    PubMed Central

    McDonald, Margaret R.

    1955-01-01

    The proteolytic activity of dilute solutions of clystalline trypsin is destroyed by x-rays, the amount of inactivation being an exponential function of the radiation dose. The reaction yield increases steadily with increasing concentration of trypsin, varying, as the concentration of enzyme is increased from 1 to 300 µM, from 0.068 to 0.958 micromole of trypsin per liter inactivated per 1000 r with 0.005 N hydrochloric acid as the solvent, from 0.273 to 0.866 with 0.005 N sulfuric acid as the solvent, and from 0.343 to 0.844 with 0.005 N nitric acid as the solvent. When the reaction yields are plotted as a function of the initial concentration of trypsin, they fall on a curve given by the expression Y α XK, in which Y is the reaction yield, X is the concentration of trypsin, and K is a constant equal to 0.46, 0.20, and 0.16, respectively, with 0.005 N hydrochloric, sulfuric, and nitric acids as solvents. The differences between the reaction yields found with chloride and sulfate ions in I to 10 µM trypsin solutions are significant only in the pH range from 2 to 4. The amount of inactivation obtained with a given dose of x-rays depends on the pH of the solution being irradiated and the nature of the solvent. The reaction yield-pH curve is a symmetrical one, with minimum yields at about pH 7. Buffers such as acetate, citrate, borate and barbiturate, and other organic molecules such as ethanol and glucose, in concentrations as low as 20 µM, inhibit the inactivation of trypsin by x-radiation. Sigmoid inactivation-dose curves instead of exponential ones are obtained in the presence of ethanol. The reaction yields for the inactivation of trypsin solutions by x-rays are approximately 1.5 times greater when the irradiation is done at 26°C. than when it is done at 5°C., when 0.005 N hydrochloric acid is the solvent. The dependence on temperature is less when 0.005 N sulfuric acid is used, and is negligible with 0.005 N nitric acid. The difficulties involved in

  6. Aggregation in dilute aqueous tert-butyl alcohol solutions: Insights from large-scale simulations

    NASA Astrophysics Data System (ADS)

    Gupta, Rini; Patey, G. N.

    2012-07-01

    possible nature of microheterogeneity in dilute TBA-water solutions, and of the associated long correlation lengths. It is clear that system size can be a very important factor in simulations of these solutions, and must be taken into account in the evaluation and development of TBA-water force fields.

  7. Measurement of solute transport in the endothelial glycocalyx using indicator dilution techniques.

    PubMed

    Gao, Lujia; Lipowsky, Herbert H

    2009-09-01

    A new method is presented to quantify changes in permeability of the endothelial glycocalyx to small solutes and fluid flow using techniques of indicator dilution. Following infusion of a bolus of fluorescent solutes (either FITC or FITC conjugated Dextran70) into the rat mesenteric circulation, its transient dispersion through post-capillary venules was recorded and analyzed offline. To represent dispersion of solute as a function of radial position in a microvessel, a virtual transit time (VTT) was calculated from the first moment of fluorescence intensity-time curves. Computer simulations and subsequent in vivo measurements showed that the radial gradient of VTT within the glycocalyx layer (Delta VTT/Delta r) may be related to the hydraulic resistance within the layer along the axial direction in a post-capillary venule and the effective diffusion coefficient within the glycocalyx. Modeling the inflammatory process by superfusion of the mesentery with 10(-7) M fMLP, Delta VTT/Delta r was found to decrease significantly from 0.23 +/- 0.08 SD s/microm to 0.18 +/- 0.09 SD s/microm. Computer simulations demonstrated that Delta VTT/Delta r is principally determined by three independent variables: glycocalyx thickness (delta), hydraulic resistivity (K(r)) and effective diffusion coefficient of the solute (D(eff)) within the glycocalyx. Based upon these simulations, the measured 20% decrease in Delta VTT/Delta r at the endothelial cell surface corresponds to a 20% increase in D(eff) over a broad range in K(r), assuming a constant thickness delta. The absolute magnitude of D(eff) required to match Delta VTT/Delta r between in vivo measurements and simulations was found to be on the order of 2.5 x 10(-3) x D(free), where D(free) is the diffusion coefficient of FITC in aqueous media. Thus the present method may provide a useful tool for elucidating structural and molecular alterations in the glycocalyx as occur with ischemia, metabolic and inflammatory events.

  8. Density functional theories of surface interactions in salt solutions.

    PubMed

    Forsman, Jan

    2009-02-14

    Most current density functional theories rely upon the presence of hard cores, also between ions of like charge. These hard cores should in principle reflect exchange repulsion. However, by the way in which these theories are formulated, the hard cores effectively determine the range of ion-ion correlations. This is because the mutual repulsion between like-charged ions is truncated below the corresponding hard sphere diameter. In most relevant applications, at least those related to ion correlations and surface forces in colloidal dispersions, exchange repulsion between like-charged ions is unimportant. This can easily be demonstrated by simulations. Unfortunately, the hard cores can in practice serve as fitting parameters in calculations with traditional density functional theory. In this work, we present alternative density functional theories to describe aqueous salt solutions. In these approaches, an approximation of the relevant "Coulomb hole" that results from correlations between like-charged ions is calculated for the system under study. Hence, our theories are completely free from fitting parameters, and the results are appropriately insensitive to the exchange repulsion acting between ions of like charge. The theories are evaluated by comparing predictions with simulation data, with an emphasis on ion correlations and surface interactions.

  9. Dynamics of falling droplet and elongational properties of dilute nonionic surfactant solutions with drag-reducing ability

    NASA Astrophysics Data System (ADS)

    Tamano, Shinji; Ohashi, Yota; Morinishi, Yohei

    2017-05-01

    The dynamics of the falling droplet through a nozzle for dilute nonionic surfactant (oleyl-dimethylamine oxide, ODMAO) aqueous solutions with viscoelastic and drag-reducing properties were investigated at different concentrations of ODMAO solutions Cs = 500, 1000, and 1500 ppm by weight. The effects of the flow rate and tube outer diameter on the length of the filament, which was the distance between the tube exit and the lower end of a droplet at the instant when the droplet almost detached from the tube, were clarified by flow visualization measurements by a high-speed video camera. Two types of breaking-off processes near the base of the droplet and within the filament were classified by the Ohnesorge number Oh and the Weber number We. In the regime of the higher Oh and We, the length of the filament became drastically larger at Cs = 1000 and 1500 ppm, whose high spinnability represented the strong viscoelasticity of ODMAO solutions. In the case where the filament was broken up near the lower end of the neck and thinning in time, the thinning of the diameter of the filament was measured by a light-emitting diode micrometer. As for the elasto-capillary thinning of dilute nonionic surfactant solutions, the initial necking process was similar to that of Newtonian fluids and then followed the exponential thinning like polymer solutions. The apparent elongational viscosity of the dilute nonionic surfactant solution was evaluated in the elasto-capillary thinning regime, in which the elongation rate was almost constant. At Cs = 1000 and 1500 ppm, the Trouton ratio, which was the ratio of the apparent elongational viscosity to the shear viscosity, was found to be several orders of magnitude larger than that of Newtonian fluids, while the shear viscosity measured by the capillary viscometer was almost the same order of the Newtonian fluids. The higher elongational property would be closely related to the higher drag-reducing ability of dilute nonionic surfactant

  10. Salting-out effects in aqueous ionic liquid solutions: cloud-point temperature shifts.

    PubMed

    Trindade, Joana R; Visak, Zoran P; Blesic, Marijana; Marrucho, Isabel M; Coutinho, João A P; Lopes, José N Canongia; Rebelo, Luis P N

    2007-05-10

    The effects of the addition of three inorganic salts, namely, NaCl, Na(2)SO(4), and Na(3)PO(4), on the liquid-liquid (L-L) phase diagram of aqueous solutions containing the model ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate, [bmim][BF(4)], were investigated. All three inorganic salts trigger salting-out effects, leading to significant upward shifts of the L-L demixing temperatures of the systems. The magnitude of the shifts depends on both the water-structuring nature of the salt and its concentration; that is, the effects are correlated with the ionic strength of the solution and the Gibbs free energy of hydration of the inorganic salt. The pH effect and the occurrence of salt precipitation in concentrated solutions are also discussed.

  11. ISOPAR L Release Rates from Saltstone Using Simulated Salt Solutions

    SciTech Connect

    Bronikowski, M

    2006-02-06

    The Modular Caustic-Side Solvent Extraction (CSSX) Unit (MCU) and the Salt Waste Processing Facility (SWPF) will produce a Deactivated Salt Solution (DSS) that will go to the Saltstone Production Facility (SPF). Recent information indicates that solvent entrainment in the DSS is larger than expected. The main concern is with Isopar{reg_sign} L, the diluent in the solvent mixture, and its flammability in the saltstone vault. If it is assumed that all the Isopar{reg_sign} L is released instantaneously into the vault from the curing grout before each subsequent pour; the Isopar{reg_sign} L in the vault headspace is well mixed; and each pour displaces an equivalent volume of headspace, the allowable concentration of Isopar{reg_sign} L in the DSS sent to SPF has been calculated at approximately 4 ppm. The amount allowed would be higher, if the release from grout were significantly less. The Savannah River National Laboratory was tasked with determining the release of Isopar{reg_sign} L from saltstone prepared with a simulated DSS with Isopar{reg_sign} L concentrations ranging from 50 mg/L to 200 mg/L in the salt fraction and with test temperatures ranging from ambient to 95 C. The results from the curing of the saltstone showed that the Isopar{reg_sign} L release data can be treated as a percentage of initial concentration in the concentration range studied. The majority of the Isopar{reg_sign} L that was released over the test duration was released in the first few days. The release of Isopar{reg_sign} L begins immediately and the rate of release decreases over time. At higher temperatures the immediate release is larger than at lower temperatures. In one test at 95 C essentially all of the Isopar{reg_sign} L was released in three months. Initial curing temperature was found to be very important as slight variations during the first few days affected the final Isopar{reg_sign} L amount released. Short scoping tests at 95 C with solvent containing all components (Isopar

  12. ISOPAR L RELEASE RATES FROM SALTSTONE USING SIMULATED SALT SOLUTIONS

    SciTech Connect

    Zamecnik, J; Michael Bronikowski, M; Alex Cozzi, A; Russell Eibling, R; Charles Nash, C

    2008-07-31

    The Modular Caustic-Side Solvent Extraction (CSSX) Unit (MCU) and the Salt Waste Processing Facility (SWPF) will produce a Decontaminated Salt Solution (DSS) that will go to the Saltstone Production Facility (SPF). Recent information indicates that solvent entrainment in the DSS is larger than expected. The main concern is with Isopar{reg_sign} L, the diluent in the solvent mixture, and its flammability in the saltstone vault. If it is assumed that all the Isopar{reg_sign} L is released instantaneously into the vault from the curing grout before each subsequent pour, the Isopar{reg_sign} L in the vault headspace is well mixed, and each pour displaces an equivalent volume of headspace, the maximum concentration of Isopar{reg_sign} L in the DSS to assure 25% of the lower flammable limit is not exceeded has been determined to be about 4 ppm. The amount allowed would be higher if the release from grout were significantly less. The Savannah River National Laboratory was tasked with determining the release of Isopar{reg_sign} L from saltstone prepared with a simulated DSS with Isopar{reg_sign} L concentrations ranging from 50 to 200 mg/L in the salt fraction and with test temperatures ranging from ambient to 95 C. The results from the curing of the saltstone showed that the amount of Isopar{reg_sign} L released versus time can be treated as a percentage of initial amount present; there was no statistically significant dependence of the release rate on the initial concentration. The majority of the Isopar{reg_sign} L that was released over the test duration was released in the first few days. The release of Isopar{reg_sign} L begins immediately and the rate of release decreases over time. At higher temperatures the immediate release rate is larger than at lower temperatures. Initial curing temperature was found to be very important as slight variations during the first few hours or days had a significant effect on the amount of Isopar{reg_sign} L released. Short scoping

  13. Interactions between ring polymers in dilute solution studied by Monte Carlo simulation

    NASA Astrophysics Data System (ADS)

    Suzuki, Jiro; Takano, Atsushi; Matsushita, Yushu

    2015-01-01

    The second virial coefficient, A2, for trivial-ring polymers in dilute condition was estimated from a Metropolis Monte Carlo (MC) simulation, and the temperature dependence of A2 has been discussed with their Flory's scaling exponent, ν, in Rg ∝ Nν, where Rg is radius of gyration of a polymer molecule. A limited but not too small number of polymer molecules were employed in the simulation, and the A2 values at various temperatures were calculated from the molecular density fluctuation in the solution. In the simulation, the topology of ring polymers was kept, since chain crossing was prohibited. The excluded volume effects can be screened by the attractive force between segments, which depends on the temperature, Tα, defined in the Metropolis MC method. Linear and trivial-ring polymers have the ν value of 1/2 at Tα = 10.605 and 10.504. At Tα = 10.504, the excluded volume effects are screened by the attractive force generated between segments in a ring polymer, but the A2 value for ring polymers is positive. Thus, the temperature at A2 = 0 for a ring polymer is lower than that at ν = 1/2, and this fact can be explained with the following two reasons. (a) Rg value for a ring polymer is much smaller than that for a linear polymer at the same temperature and molecular weight, where interpenetration of a ring polymer chain into neighboring chains is apparently less than a linear chain. (b) The conformation of trivial rings can be statistically described as a closed random walk at ν = 1/2, but their topologies are kept, being produced topological constraints, which strongly relate not only to the long-distance interaction between segments in a molecule but also the inter-molecular interaction.

  14. Comparison of the kinetics of chain aggregation and chain collapse in dilute polymer solutions.

    PubMed

    Maki, Yasuyuki; Dobashi, Toshiaki; Nakata, Mitsuo

    2008-10-01

    The rates of chain aggregation of poly(methyl methacrylate) (PMMA) in acetonitrile (AcN) and in the mixed solvent of AcN+water (10 vol%) were determined by static light scattering and compared with the rates of chain collapse [Maki, J. Chem. Phys. 126, 134901 (2007)]. Dilute solutions of PMMA with the molecular weight m{w}=6.4 x 10{6} and in the concentration range of (0.8-5)x10;{-4}gcm;{3} were quenched below the cloud point, and the weight-average molecular weight M{w} and z -average square radius of gyration S;{2}_{z} for clusters of PMMA chains were measured as a function of the time t after the quench and the concentration c . The measurement of chain aggregation was carried out up to the cluster size of M{w}m{w} approximately 30 , which required time periods of hours to several days depending on the concentration and solvent. The chain aggregation in AcN+water occurred much faster than that in AcN. The growth of clusters in both the solvents was represented by the exponential function as M{w} approximately e;{gct} and S;{2}_{z} approximately e{hct} , where g and h represent the intrinsic rate of chain aggregation. The ratio sigma of the intrinsic rate in AcN+water to that in AcN was estimated to be 9 by taking a rough average of the ratios 9.4 obtained from g and 8.8 from h . This value is comparable to the ratio 11 of the rate of chain collapse of PMMA in AcN+water (10 vol%) to that in AcN. This close value of the ratios indicates that the nature of solvent would affect the rates of chain collapse and chain aggregation through a similar mechanism.

  15. MTBE Hydrolysis in Dilute Aqueous Solution Using Heterogeneous Strong Acid Catalysts

    NASA Astrophysics Data System (ADS)

    Rixey, W. G.

    2003-12-01

    The objective of this research has been the development of a potential in situ catalytic process for the hydrolysis of methyl tertiary butyl ether (MTBE) to tertiary butyl alcohol (TBA) and methanol in ground water. Bench-scale batch reactor studies were conducted over a temperature range of 23 deg C to 50 deg C with several heterogeneous strong acid catalysts to obtain rates of hydrolysis of MTBE to TBA and methanol at dilute concentrations in water. Continuous flow experiments were then conducted to obtain kinetic data over a temperature range of 15 deg C to 50 deg C for various flow rates for the most active catalysts. It was found that the batch and continuous flow experiments yielded similar intrinsic kinetic rate constants when sorption of MTBE to the catalyst was accounted for. Additional fixed-bed experiments were conducted with deionized water and 0.005 M CaCl2 feed solutions containing 100 mg/L MTBE, respectively, to assess the deactivation of the catalyst, and deactivation was found to be controlled by ion exchange of H+ in the catalyst with Ca+2 in the feed. Our results indicate that, for low to moderate groundwater velocities and cation concentrations at ambient temperatures, an in situ reactive barrier process using the most active catalysts studied in this research could be a viable process in terms of both suitable conversion of MTBE and catalyst life. Although application to in situ remediation is emphasized, the results of this research are also applicable to ex-situ groundwater treatment.

  16. Solvent controlled ion association in structured copolymers: Molecular dynamics simulations in dilute solutions

    NASA Astrophysics Data System (ADS)

    Aryal, Dipak; Perahia, Dvora; Grest, Gary S.

    2015-09-01

    Tailoring the nature of individual segments within ion containing block co-polymers is one critical design tool to achieve desired properties. The local structure including the size and distribution of the ionic blocks, as well as the long range correlations, are crucial for their transport ability. Here, we present molecular dynamics simulations on the effects of varying the concentrations of the ionizable groups on the conformations of pentablock ionomer that consist of a center block of ionic sulfonated styrene tethered to polyethylene and terminated by a bulky substituted styrene in dilute solutions. Sulfonation fractions f (0 ≤ f ≤ 0.55), spanning the range from ionomer to polyelectrolytes, were studied. Results for the equilibrium conformation of the chains in water and a 1:1 mixture of cyclohexane and heptane are compared to that in implicit poor solvents with dielectric constants ɛ = 1.0 and 77.73. In water, the pentablock collapses with the sulfonated groups on the outer surface. As f increases, the ionic, center block increasingly segregates from the hydrophobic regions. In the 1:1 mixture of cyclohexane and heptane, the flexible blocks swell, while the center ionic block collapses for f > 0. For f = 0, all blocks swell. In both implicit poor solvents, the pentablock collapses into a nearly spherical shape for all f. The sodium counterions disperse widely throughout the simulation cell for both water and ɛ = 77.73, whereas for ɛ = 1.0 and mixture of cyclohexane and heptane, the counterions largely condense onto the collapsed pentablock.

  17. Comparison of the kinetics of chain aggregation and chain collapse in dilute polymer solutions

    NASA Astrophysics Data System (ADS)

    Maki, Yasuyuki; Dobashi, Toshiaki; Nakata, Mitsuo

    2008-10-01

    The rates of chain aggregation of poly(methyl methacrylate) (PMMA) in acetonitrile (AcN) and in the mixed solvent of AcN+water (10vol%) were determined by static light scattering and compared with the rates of chain collapse [Maki , J. Chem. Phys. 126, 134901 (2007)]. Dilute solutions of PMMA with the molecular weight mw=6.4×106 and in the concentration range of (0.8-5)×10-4g/cm3 were quenched below the cloud point, and the weight-average molecular weight Mw and z -average square radius of gyration ⟨S2⟩z for clusters of PMMA chains were measured as a function of the time t after the quench and the concentration c . The measurement of chain aggregation was carried out up to the cluster size of Mw/mw˜30 , which required time periods of hours to several days depending on the concentration and solvent. The chain aggregation in AcN+water occurred much faster than that in AcN. The growth of clusters in both the solvents was represented by the exponential function as Mw˜egct and ⟨S2⟩z˜ehct , where g and h represent the intrinsic rate of chain aggregation. The ratio σ of the intrinsic rate in AcN+water to that in AcN was estimated to be 9 by taking a rough average of the ratios 9.4 obtained from g and 8.8 from h . This value is comparable to the ratio 11 of the rate of chain collapse of PMMA in AcN+water (10vol%) to that in AcN. This close value of the ratios indicates that the nature of solvent would affect the rates of chain collapse and chain aggregation through a similar mechanism.

  18. A Study of Novel Hexavalent Phosphazene Salts as Draw Solutes in Forward Osmosis

    SciTech Connect

    Mark L. Stone; Aaron D. Wilson; Mason K. Harrup; Frederick F. Stewart

    2013-03-01

    Two novel multi-valent salts based on phosphazene chemistry have been synthesized and characterized as forward osmosis (FO) draw solutes. Commercially obtained hexachlorocyclotriphosphazene was reacted with the sodium salt of 4-ethylhydroxybenzoate to yield hexa(4-ethylcarboxylatophenoxy)phosphazene. Hydrolysis, followed by and neutralization with NaOH or LiOH, of the resulting acidic moieties yielded water soluble sodium and lithium phosphazene salts, respectively. Degrees of dissociation were determined through osmometry over the range of 0.05-0.5 m, giving degrees of 3.08-4.95 per mole, suggesting a high osmotic potential. The Li salt was found to be more ionized in solution than the sodium salt, and this was reflected in FO experiments where the Li salt gave higher initial fluxes (~ 7 L/m2h) as compared to the sodium salt (~6 L/m2h) at identical 0.07 m draw solution concentrations at 30 °C. Longer term experiments revealed no detectable degradation of the salts; however some hydrolysis of the cellulose acetate membrane was observed, presumably due to the pH of the phosphazene salt draw solution (pH = ~8).

  19. Selective flotation of zinc(II) and silver(I) ions from dilute aqueous solutions

    SciTech Connect

    Charewicz, W.A.; Holowiecka, B.A.; Walkowiak, W.

    1999-09-01

    An experimental investigation is presented of the batch competitive flotation of zinc(II) and silver(I) ions from dilute aqueous solutions with sodium dodecylsulfate and ammonium tetradecysulfonate as anionic surfactants and with cetylpyridinium chloride as a cationic surfactant. The sequence of growing affinity of metal cations to anionic surfactants is the same as the sequence of ionic potential values of the studied cations: AG{sup +} < Zn{sup 2+}. The presence of potassium sulfate in aqueous solution has a negative influence of Zn{sup 2+} foam separation with a anionic surfactant which is due to competition for the surfactant between Zn{sup 2+} and K{sup +} cations. Also, the effect of inorganic ligands (i.e., thiosulfates, thiocyanates, and cyanides) on the selectivity of ion flotation of Zn(II) and Ag(I) is established. Results are discussed in terms of the complex species of zinc(II) and silver(I). At a total S{sub 2}O{sub 3}{sup 2{minus}} concentration of 3 {times} 10{sup {minus}6} M, the silver(I) is floated as a mixture of anions [Ag(S{sub 2}O{sub 3})]{sup {minus}} and [Ag(S{sub 2}O{sub 3}){sub 2}]{sup 3{minus}}, whereas zinc(II) remains in the aqueous phase as Zn{sup 2+}. At total concentrations of SCN{sup {minus}} from 1 {times} 10{sup {minus}4} to 2 {times} 10{sup {minus}3} M, silver(I) is floated as a mixture of [Ag(SCN){sub 2}]{sup {minus}} and AgSCN species. Partial separation of zinc(II) from silver(I) can be achieved in the presence of CN{sup {minus}} ligands at total concentrations varying from 2.5 {times} 10{sup {minus}4} to 1.0 {times} 10{sup {minus}3} M. The affinity of the studied cyanide complexes to cetylpyridinium chloride follows the order [Ag(CN){sub 2}]{sup {minus}} < [Zn(CN){sub 4}]{sup 2{minus}} + [Zn(CN){sub 3}]{sup {minus}}.

  20. Molecular imaging of shear-induced polymer migration near a surface in dilute and semidilute solutions

    NASA Astrophysics Data System (ADS)

    Fang, Lin

    The goal of our research is to optically visualize shear-induced polymer migration near a surface on the single molecular level, and to enhance current understanding of interactions between flowing polymer solutions with surfaces. By using epi-fluorescence microscopy, we measured the mean fractional stretch and concentrations of lambda-phage DNA molecules above a glass surface in shear flows in a microchannel and a torsional shear cell. We find that DNA molecules are driven away to create a depletion layer near the surface. The shear-induced migration is enhanced with a larger depletion layer at high Weissenberg number (Wi), in qualitative agreement with theories. We proposed a simple mechanism for this shear-induced migration based on hydrodynamic interaction (HI) between the surface and polymer chains. We find that the thickness of depletion layer of lambda-phage DNA molecules is about 10mum at Wi = 10.3, which is thinner than in the predictions for the FENE-P dumbbell model [Ma and Graham (2005)] and in Brownian dynamics simulations. The discrepancies suggest that current theoretical models of the polymer migration phenomenon are incomplete. We find that the time scale of DNA migration is on the order of the diffusion time over the distance of depletion layer, and that the mean fractional stretch of DNA molecules decreases near the surface over this same time scale. Experiments with deliberately fragmented DNA indicate that the decrease in mean fractional stretch near the surface might be caused by the selective retention of fragments in the DNA solution owing to weaker HI effects between the surface and shorter polymer chains. The shear-induced migration of DNA molecules exists in diminished form up to 3.0 c* (c* is the overlap concentration), implying that: in the traditionally defined dilute regime (c < c*), screening of wall hydrodynamics occurs over DNA concentration from 0.1 c* to 1.0 c*; and in the semidilute regime (c > c*); while the chains are

  1. Self-assembly of nonionic surfactant Tween 20@2β-CD inclusion complexes in dilute solution.

    PubMed

    Zhou, Chengcheng; Cheng, Xinhao; Zhao, Qiang; Yan, Yun; Wang, Jide; Huang, Jianbin

    2013-10-29

    It has long been considered that the addition of cyclodextrins (CDs) disfavors the self-assembly of surfactants in dilute solutions since the hydrophobic effect is destroyed upon the formation of the hydrophiphilic CD/surfactant inclusion complex. However, in this work, we found that β-CD/nonionic surfactant inclusion complexes are able to self-assemble into vesicles in dilute solutions, namely in solutions with concentration lower than the CMC of surfactants. When using Tween 20 as a model surfactant, HNMR and MS measurements indicate that the building block for the vesicles is the channel type Tween 20@2β-CD inclusion complex. Structure and IR analysis suggests that the self-assembly of hydrophilic Tween 20@2β-CD is driven by H-bonds between both the headgroup of Tween 20 and the hydroxyl groups of β-CD. The self-assembly of the inclusion complex between the β-CD and the nonionic surfactant in dilute solution is found to be a general phenomenon. Undoubtedly, surfactant@2β-CD inclusion complex can be a novel building block for nonamphiphilic self-assembly, which provides a new physical insight for the influence of cyclodextrins on the self-assembly of surfactants.

  2. Concentration and precipitation of NaCl and KCl from salt cake leach solutions by electrodialysis

    SciTech Connect

    Sreenivasarao, K; Patsiogiannis, F.; Hryn, J.N.

    1997-02-09

    Electrodialysis was investigated for cost-effective recovery of salt from salt cake leach solutions. (Salt cake is a waste stream generated by the aluminum industry during treatment of aluminum drosses and scrap.) We used a pilot-scale electrodialysis stack of 5 membrane pairs, each with an effective area of 0.02 m{sup 2}. The diluate stream contained synthetic NaCl, KCl,mixtures of NaCl and KCl, and actual salt cake leach solutions (mainly NaCl and KCl, with small amounts of MgCl{sub 2}). We concentrated and precipitated NaCl and KCl salts from the concentrate steam when the initial diluate stream concentration was 21.5 to 28.8 wt% NaCl and KCl. We found that water transferring through the membranes was a significant factor in overall efficiency of salt recovery by electrodialysis.

  3. Salt weathering in Egyptian limestone after laboratory simulations with continuous flow of salt solutions at different temperatures

    NASA Astrophysics Data System (ADS)

    Aly, Nevin; Gomez-Heras, Miguel; Hamed, Ayman; Alvarez de Buergo, Monica

    2013-04-01

    weathering in Egyptian limestone after laboratory simulations with continuous flow of salt solutions at different temperatures Nevin Aly Mohamed (1), Miguel Gomez - Heras(2), Ayman Hamed Ahmed (1), and Monica Alvarez de Buergo(2). (1) Faculty of Pet. & Min. Engineering- Suez Canal University, Suez, Egypt, (2) Instituto de Geociencias (CSIC-UCM) Madrid. Spain. Limestone is one of the most frequent building stones in Egypt and is used since the time of ancient Egyptians and salt weathering is one of the main threats to its conservation. Most of the limestone used in historical monuments in Cairo is a biomicrite extracted from the Mid-Eocene Mokattam Group. During this work, cylindrical samples (2.4 cm diameter and approx. 4.8 cm length) were subjected, in a purpose-made simulation chamber, to simulated laboratory weathering tests with fixed salt concentration (10% weight NaCl solution), at different temperatures, which were kept constant throughout each test (10, 20, 30, 40 oC). During each test, salt solutions flowed continuously imbibing samples by capilarity. Humidity within the simulation chamber was reduced using silica gel to keep it low and constant to increase evaporation rate. Temperature, humidity inside the simulation chamber and samples weight were digitally monitored during each test. Results show the advantages of the proposed experimental methodology using a continuous flow of salt solutions and shed light on the effect of temperature on the dynamics of salt crystallization on and within samples. Research funded by mission sector of high education ministry, Egypt and Geomateriales S2009/MAT-1629.

  4. Testing of stripping columns for the removal of benzene from aqueous radioactive salt solution

    SciTech Connect

    Georgeton, G.K.; Taylor, G.A.; Gaughan, T.P.

    1995-06-27

    Radioactive high level wastes (HLW) generated from production of special nuclear materials at the Savannah River Site (SRS) are held in interim storage in 51 underground, million gallon tanks. Radioactive cesium ({sup 137}Cs) is segregated by evaporation of aqueous waste solution for interim storage in a salt matrix comprised of Na and K salts or in concentrated salt solution. The saltcake will be dissolved and {sup 137}Cs will be separated from the nonradioactive salts in solution in the In-Tank Precipitation (ITP) Process. The cesium will be combined with other radioactive species and glass formers to be melted and poured into stainless steel canisters in the Defense Waste Processing Facility (DWPF). The salt solution remaining after decontamination in the ITP process will be incorporated into grout for disposal at the site`s Saltstone facility. In the ITP facility, sodium tetraphenylborate (STPB) will be added to precipitate the cesium. Potassium in the waste solution also reacts with STPB and precipitates. Due to radiolytic and chemical degradation of the tetraphenylborate (TPB) precipitate, benzene is generated. The benzene dissolves into the decontaminated salt solution (DSS) and into water (WW) used to {open_quotes}wash{close_quotes} the precipitate to lower the soluble salt content of the slurry. Safety and processing requirements for disposal of the DSS and for temporary storage of the WW dictate that the benzene concentration be reduced.

  5. Conformations of gelatin in trivalent chromium salt solutions: Viscosity and dynamic light scattering study

    NASA Astrophysics Data System (ADS)

    Qiao, Congde; Zhang, Jianlong; Kong, Aiqun

    2017-02-01

    An investigation of the influences of pH, salt type, and salt concentration on the conformations of gelatin molecules in trivalent chromium salt solutions was performed by viscosity and dynamic light scattering (DLS) techniques. It was found that the viscosity behaviors as polyelectrolytes or polyampholytes depended on the charge distribution on the gelatin chains, which can be tuned by the value of pH of the gelatin solution. The intrinsic viscosity of gelatin in basic chromium sulfate aqueous solution at pH = 2.0 first decreased and then increased with increasing Cr(OH)SO4 concentration, while a monotonic decrease of the intrinsic viscosity of gelatin was observed in CrCl3 solution. However, the intrinsic viscosity of gelatin at pH = 5.0 was found to be increased first and then decreased with an increase in salt concentration in Cr(OH)SO4 solution, as well as in CrCl3 solution. We suggested that the observed viscosity behavior of gelatin in trivalent chromium salt solutions was attributed to the comprehensive effects of shielding, overcharging, and crosslinking (complexation) caused by the introduction of the different counterions. In addition, the average hydrodynamic radius ( R h ) of gelatin molecules in various salt solutions was determined by DLS. It was found that the change trend of R h with salt concentration was the same as the change of intrinsic viscosity. Based on the results of the viscosity and DLS, a possible mechanism for the conformational transition of gelatin chains with external conditions including pH, salt concentration, and salt type is proposed.

  6. Effects of dilute aqueous NaCl solution on caffeine aggregation

    NASA Astrophysics Data System (ADS)

    Sharma, Bhanita; Paul, Sandip

    2013-11-01

    The effect of salt concentration on association properties of caffeine molecule was investigated by employing molecular dynamics simulations in isothermal-isobaric ensemble of eight caffeine molecules in pure water and three different salt (NaCl) concentrations, at 300 K temperature and 1 atm pressure. The concentration of caffeine was taken almost at the solubility limit. With increasing salt concentration, we observe enhancement of first peak height and appearance of a second peak in the caffeine-caffeine distribution function. Furthermore, our calculated solvent accessible area values and cluster structure analyses suggest formation of higher order caffeine cluster on addition of salt. The calculated hydrogen bond properties reveal that there is a modest decrease in the average number of water-caffeine hydrogen bonds on addition of NaCl salt. Also observed are: (i) decrease in probability of salt contact ion pair as well as decrease in the solvent separated ion pair formation with increasing salt concentration, (ii) a modest second shell collapse in the water structure, and (iii) dehydration of hydrophobic atomic sites of caffeine on addition of NaCl.

  7. Effects of dilute aqueous NaCl solution on caffeine aggregation

    SciTech Connect

    Sharma, Bhanita; Paul, Sandip

    2013-11-21

    The effect of salt concentration on association properties of caffeine molecule was investigated by employing molecular dynamics simulations in isothermal-isobaric ensemble of eight caffeine molecules in pure water and three different salt (NaCl) concentrations, at 300 K temperature and 1 atm pressure. The concentration of caffeine was taken almost at the solubility limit. With increasing salt concentration, we observe enhancement of first peak height and appearance of a second peak in the caffeine-caffeine distribution function. Furthermore, our calculated solvent accessible area values and cluster structure analyses suggest formation of higher order caffeine cluster on addition of salt. The calculated hydrogen bond properties reveal that there is a modest decrease in the average number of water-caffeine hydrogen bonds on addition of NaCl salt. Also observed are: (i) decrease in probability of salt contact ion pair as well as decrease in the solvent separated ion pair formation with increasing salt concentration, (ii) a modest second shell collapse in the water structure, and (iii) dehydration of hydrophobic atomic sites of caffeine on addition of NaCl.

  8. Recovery of glycols, sugars, and Related Multiple -OH Compounds from Dilute-Aqueous Solution by Regenerable Adsorption onto Activated Carbons

    SciTech Connect

    Chinn, Daniel

    1999-06-01

    The present research explores the use of adsorption onto activated carbons as a means of recover glycerol, glycols, and sugars from dilute-aqueous solution. Our work is focused on understanding the mechanisms of adsorption onto carbons, assessing the degree of adsorption reversibility with precision, and implementing a bench-scale recovery process that results in a higher product concentration and reduction of the energy load for final purification.

  9. Determination of the viscosity number of thermoplastics in dilute solution; polyamides (PA)

    NASA Technical Reports Server (NTRS)

    1985-01-01

    This West German Standard presents a test used to determine the viscosity number of polyamides and copolyamides which are easily diluted in sulfuric acid, and for other polyamides which are less easily diluted in sulfuric acid, and which are diluted in m-cresol. As formic acid is often used in industry instead of sulfuric acid, this solvent is also presented as an alternative, however, sulfuric acid is preferred because of the thermodynamic solubility characteristics of the polyamides and the handling safety. In addition, it is shown which solvent should be used for each polyamide. Finally, determinations concerning the preparation of the samples are presented. Using the viscosity number, a determination of the molar mass of the polyamides is possible.

  10. Enthalpies of the dissolution and dilution of aqueous solutions of rubidium and cesium diclofenac at 293.15-318.15 K

    NASA Astrophysics Data System (ADS)

    Manin, N. G.; Perlovich, G. L.; Fini, A.

    2014-03-01

    Enthalpies of the dissolution and dilution of aqueous solutions of rubidium and cesium diclofenac (RbDC and CsDC) are measured at 293.15, 298.15, 308.15, and 318.15 K at concentrations of water of less than 0.1 mol/kg. The heat capacity of RbDC and CsDC crystal salts is determined. Changes in the thermodynamic properties of both a solution and its components vs. concentration and temperature is considered. An increase in the endothermicity of the dissolution of RbDC and CsDC with a rise in temperature is noted. It is shown that the dissolution of both RbDC and CsDC electrolytes in water is determined by the contribution from entropy. It is shown that in aqueous solutions of RbDC and CsDC, the degree of binding of water molecules is higher than in pure water at temperatures below 303.15 K.

  11. Novel, electrolyte solutions comprising fully inorganic salts with high anodic stability for rechargeable magnesium batteries.

    PubMed

    Doe, Robert E; Han, Ruoban; Hwang, Jaehee; Gmitter, Andrew J; Shterenberg, Ivgeni; Yoo, Hyun Deog; Pour, Nir; Aurbach, Doron

    2014-01-07

    Herein the first inorganic magnesium salt solution capable of highly reversible magnesium electrodeposition is presented. Synthesized by acid-base reaction of MgCl2 and Lewis acidic compounds such as AlCl3, this salt class demonstrates upwards of 99% Coulombic efficiency, deposition overpotential of <200 mV, and anodic stability of 3.1 V.

  12. Novel, electrolyte solutions comprising fully inorganic salts with high anodic stability for rechargeable magnesium batteries

    SciTech Connect

    Doe, RE; Han, R; Hwang, J; Gmitter, AJ; Shterenberg, I; Yoo, HD; Pour, N; Aurbach, D

    2014-01-01

    Herein the first inorganic magnesium salt solution capable of highly reversible magnesium electrodeposition is presented. Synthesized by acid-base reaction of MgCl2 and Lewis acidic compounds such as AlCl3, this salt class demonstrates upwards of 99% Coulombic efficiency, deposition overpotential of <200 mV, and anodic stability of 3.1 V.

  13. Location of microseismic swarms induced by salt solution mining

    NASA Astrophysics Data System (ADS)

    Kinscher, J.; Bernard, P.; Contrucci, I.; Mangeney, A.; Piguet, J. P.; Bigarre, P.

    2015-01-01

    Ground failures, caving processes and collapses of large natural or man-made underground cavities can produce significant socio-economic damages and represent a serious risk envisaged by the mine managements and municipalities. In order to improve our understanding of the mechanisms governing such a geohazard and to test the potential of geophysical methods to prevent them, the development and collapse of a salt solution mining cavity was monitored in the Lorraine basin in northeastern France. During the experiment, a huge microseismic data set (˜50 000 event files) was recorded by a local microseismic network. 80 per cent of the data comprised unusual swarming sequences with complex clusters of superimposed microseismic events which could not be processed through standard automatic detection and location routines. Here, we present two probabilistic methods which provide a powerful tool to assess the spatio-temporal characteristics of these swarming sequences in an automatic manner. Both methods take advantage of strong attenuation effects and significantly polarized P-wave energies at higher frequencies (>100 Hz). The first location approach uses simple signal amplitude estimates for different frequency bands, and an attenuation model to constrain the hypocentre locations. The second approach was designed to identify significantly polarized P-wave energies and the associated polarization angles which provide very valuable information on the hypocentre location. Both methods are applied to a microseismic data set recorded during an important step of the development of the cavity, that is, before its collapse. From our results, systematic spatio-temporal epicentre migration trends are observed in the order of seconds to minutes and several tens of meters which are partially associated with cyclic behaviours. In addition, from spatio-temporal distribution of epicentre clusters we observed similar epicentre migration in the order of hours and days. All together, we

  14. Students' Misconceptions in Electrochemistry: Current Flow in Electrolyte Solutions and the Salt Bridge.

    ERIC Educational Resources Information Center

    Sanger, Michael J.; Greenbowe, Thomas J.

    1997-01-01

    Examines students' misconceptions and proposed mechanisms related to current flow in electrolyte solutions and the salt bridge. Confirms reported misconceptions and identifies several new ones. Discusses probable sources of misconceptions and some methods for preventing them. Contains 27 references. (JRH)

  15. Enthalpy changes upon dilution and ionization of poly(L-glutamic acid) in aqueous solutions.

    PubMed

    Godec, Andrej; Skerjanc, Joze

    2005-07-14

    The enthalpy changes accompanying the dilution and ionization of poly(L-glutamic acid) in water have been measured at 25 degrees C for two degrees of polymerization (DP = 115 and DP = 480) at various degrees of ionization, alpha, for a concentration range from about 0.2 to 0.002 monomol/L. The heat of dilution displays an unusual dependence on the degree of ionization, which is in sharp contrast to the behavior of other weak carboxylic polyelectrolytes, such as poly(acrylic acid). The exothermic heat effects observed at low values of alpha become endothermic for the region where the helix-coil transition is most pronounced, and for high degrees of ionization, they are exothermic again. Evidently, an endothermic heat effect, produced by an additional conformational transition in the dilution process, is superimposed on the exothermic enthalpy of dilution, and it overweighs the latter in the region of alpha where the conformational transition is prevailing. The calorimetric titration curve, which gives the dependence of the heat of ionization, deltaH(i), on alpha, has a maximum and is typical for poly(carboxylic acids) which undergo pH-induced conformational transition, such as poly(methacrylic acid). The values of deltaH(i) obtained at two polymer concentrations indicate that the enthalpy of ionization depends on the polypeptide concentration.

  16. Materials and methods for stabilizing nanoparticles in salt solutions

    DOEpatents

    Robinson, David Bruce; Zuckermann, Ronald; Buffleben, George M.

    2013-06-11

    Sequence-specific polymers are proving to be a powerful approach to assembly and manipulation of matter on the nanometer scale. Ligands that are peptoids, or sequence-specific N-functional glycine oligomers, allow precise and flexible control over the arrangement of binding groups, steric spacers, charge, and other functionality. We have synthesized short peptoids that can prevent the aggregation of gold nanoparticles in high-salt environments including divalent salt, and allow co-adsorption of a single DNA molecule. This degree of precision and versatility is likely to prove essential in bottom-up assembly of nanostructures and in biomedical applications of nanomaterials.

  17. Effect of Salt Concentration on the Structure of Poly(Vinyl Alcohol) Cryogels Obtained from Aqueous Salt Solutions

    NASA Astrophysics Data System (ADS)

    Tretinnikov, O. N.; Sushko, N. I.; Zagorskaya, S. A.

    2015-03-01

    The degree of polymer crystallinity and water content on the surfaces and in the bulk of poly(vinyl alcohol) (PVA) cryogels prepared from aqueous salt solutions were determined as functions of KCl concentration using FTIR-ATR spectroscopy. It was found that the degree of PVA crystallinity increased with increasing KCl concentration and was much greater in the cryogel bulk than on its surfaces. Addition of salt at a concentration of 1.3 M increased the degree of polymer crystallinity on the cryogel surfaces by 1.6-2.3 times whereas the crystallinity in the bulk increased by 3.3-4 times. The cryogel water contents on the surfaces and in the bulk were approximately equal and were practically independent of the salt concentration.

  18. Salt-Finger Convection in a Stratified Fluid Layer Induced by Thermal and Solutal Capillary Motion

    NASA Technical Reports Server (NTRS)

    Chen, Chuan F.; Chan, Cho Lik

    1996-01-01

    Salt-finger convection in a double-diffusive system is a motion driven by the release of gravitational potential due to different diffusion rates. Normally, when the gravitational field is reduced, salt-finger convection together with other convective motions driven by buoyancy forces will be rapidly suppressed. However, because the destabilizing effect of the concentration gradient is amplified by the Lewis number, with values varying from 10(exp 2) for aqueous salt solutions to 10 (exp 4) for liquid metals, salt-finger convection may be generated at much reduced gravity levels. In the microgravity environment, the surface tension gradient assumes a dominant role in causing fluid motion. In this paper, we report on some experimental results showing the generation of salt-finger convection due to capillary motio on the surface of a stratified fluid layer. A numerical simulation is presented to show the cause of salt-finger convection.

  19. Pesticide Removal from Aqueous Solutions by Adding Salting Out Agents

    PubMed Central

    Moscoso, Fátima; Deive, Francisco J.; Esperança, José M. S. S.; Rodríguez, Ana

    2013-01-01

    Phase segregation in aqueous biphasic systems (ABS) composed of four hydrophilic ionic liquids (ILs): 1-butyl-3-methylimidazolium methylsulfate and 1-ethyl-3-methylimidazolium methylsulfate (CnC1im C1SO4, n = 2 and 4), tributylmethyl phosphonium methylsulfate (P4441 C1SO4) and methylpyridinium methylsulfate (C1Py C1SO4) and two high charge density potassium inorganic salts (K2CO3 and K2HPO4) were determined by the cloud point method at 298.15 K. The influence of the addition of the selected inorganic salts to aqueous mixtures of ILs was discussed in the light of the Hofmeister series and in terms of molar Gibbs free energy of hydration. The effect of the alkyl chain length of the cation on the methylsulfate-based ILs has been investigated. All the solubility data were satisfactorily correlated to several empirical equations. A pesticide (pentachlorophenol, PCP) extraction process based on the inorganic salt providing a greater salting out effect was tackled. The viability of the proposed process was analyzed in terms of partition coefficients and extraction efficiencies. PMID:24145747

  20. Small-angle X-ray scattering from salt-free solutions of star-branched polyelectrolytes

    NASA Astrophysics Data System (ADS)

    Heinrich, M.; Rawiso, M.; Zilliox, J. G.; Lesieur, P.; Simon, J. P.

    2001-02-01

    The dispersion state of sodium-sulphonated polystyrene (ensuremathNaPSS) star-branched polyelectrolytes was investigated in salt-free aqueous solutions, by use of the small-angle X-ray scattering technique. With respect to polystyrene (PS) star-branched polymers of identical functionality, the ordering phenomenon occurring in the neighborhood of the overlap concentration c^* is reinforced and observed in a larger range of concentrations. Moreover, the degree of order is no longer maximum at c^* and is improved as the concentration decreases. The dispersion state is then mainly controlled by the electrostatic interaction. A crystalline order should therefore be achieved with stars of lower functionality, provided the electrostatic interaction is added to the osmotic repulsion. On the other hand, unusual scattering patterns are measured for aqueous solutions of ensuremathNaPSS star polyelectrolytes. Indeed, a diffuse scattering is revealed at high angles, in addition to the regular diffraction rings related to preferred interstar distances. It is similar to the broad scattering peak produced by semidilute solutions of ensuremathNaPSS linear polyelectrolytes and associated to the electrostatic correlation hole within the isotropic model. In the dilute regime (c< c^*), it is just an intramolecular characteristic and represents the electrostatic repulsion between arms belonging to the same star. In the semidilute regime (c> c^*), it also reflects the electrostatic repulsion between arms of distinct stars. So, as the concentration increases, it is mainly caused by the interpenetration of ensuremathNaPSS stars. Such an observation is in agreement with the composite structure earlier proposed by Daoud and Cotton for star semidilute solutions. For c> c^*, ensuremathNaPSS star aqueous solutions can therefore be pictured as effective stars immersed in a matrix formed by the overlap of the arm ends. With respect to the dilute regime, the effective stars are smaller; the higher

  1. IR spectroscopy of aqueous alkali halide solutions: Pure salt-solvated water spectra and hydration numbers

    NASA Astrophysics Data System (ADS)

    Max, Jean-Joseph; Chapados, Camille

    2001-08-01

    Extrapolation techniques were used to obtain pure salt-solvated water spectra from the attenuated total reflection infrared spectra (ATR-IR) of aqueous solutions of the nine alkali halide salts LiCl, NaCl, KCl, CsCl, NaBr, KBr, NaI, KI, and CsI and the alkaline-earth chloride salt MgCl2. These salts ionize completely in water. The ions by themselves do not absorb in the IR, but their interactions with water can be observed and analyzed. A pure salt-solvated water spectrum is easier to analyze than that of a combined solution of pure water and salt-solvated water. Although the salt-solvated water spectra examined have distinctive signatures, they can be classified in three categories: those similar to NaCl; those not similar to NaCl; and MgCl2, in a class by itself. Each of the pure salt-solvated water spectra differs from that of liquid water, though the number of bands is the same. From the Gaussian band fitting, we found that the positions of the bands were fairly constant, whereas their intensities differed. The salt hydration numbers were determined: for NaCl, KCl, NaBr, KBr, and CsI solutions it is 5; for KI and MgCL2 it is 4; for NaI it is 3.5; for CsCl it is 3; and for LiCl it is 2. From these results we found that each pair of ions (monoatomic ions) of the ten salt solutions studied are close bound and form a complex in a cluster organization with a fixed number of water molecules.

  2. Effective enzymatic in situ saccharification of bamboo shoot shell pretreated by dilute alkalic salts sodium hypochlorite/sodium sulfide pretreatment under the autoclave system.

    PubMed

    Chong, Gang-Gang; He, Yu-Cai; Liu, Qiu-Xiang; Kou, Xiao-Qin; Huang, Xiao-Jun; Di, Jun-Hua; Ma, Cui-Luan

    2017-10-01

    In this study, dilute alkali salts (0.6% NaClO, 0.067% Na2S) pretreatment at 10% sulfidity under the autoclave system at 120°C for 40min was used for pretreating bamboo shoot shell (BSS). Furthermore, FT-IR, XRD and SEM were employed to characterize the changes in the cellulose structural characteristics (porosity, morphology, and crystallinity) of the pretreated BSS solid residue. After 72h, the reducing sugars and glucose from the enzymatic in situ hydrolysis of 50g/L pretreated BSS in dilute NaClO/Na2S media could be obtained at 31.11 and 20.32g/L, respectively. Finally, the obtained BSS-hydrolysates containing alkalic salt NaClO/Na2S resulted in slightly negative effects on the ethanol production. Glucose in BSS-hydrolysates was fermented from 20.0 to 0.17g/L within 48h, and an ethanol yield of 0.41g/g glucose, which represents 80.1% of the theoretical yield, was obtained. This study provided an effective strategy for potential utilization of BSS. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. Specific Ion Effects: Why the Properties of Lysozyme in Salt Solutions Follow a Hofmeister Series

    PubMed Central

    Boström, M.; Williams, D. R. M.; Ninham, B. W.

    2003-01-01

    Protein solubility in aqueous solutions depends in a complicated and not well understood way on pH, salt type, and salt concentration. Why for instance does the use of two different monovalent salts, potassium thiocyanate and potassium chloride, produce such different results? One important and previously neglected source of ion specificity is the ionic dispersion potential that acts between each ion and the protein. This attractive potential is found to be much stronger for SCN− than it is for Cl−. We present model calculations, performed within a modified ion-specific double-layer theory, that demonstrate the large effect of including these ionic dispersion potentials. The results are consistent with experiments performed on hen egg-white lysozymes and on neutral black lipid membranes. The calculated surface pH and net lysozyme charge depend strongly on the choice of anion. We demonstrate that the lysozyme net charge is larger, and the corresponding Debye length shorter, in a thiocyanate salt solution than in a chloride salt solution. Recent experiments have suggested that pKa values of histidines depend on salt concentration and on ionic species. We finally demonstrate that once ionic dispersion potentials are included in the theory these results can quantitatively be reinterpreted in terms of a highly specific surface pH (and a salt-independent pKa). PMID:12885620

  4. Correlation of second virial coefficient with solubility for proteins in salt solutions.

    PubMed

    Mehta, Chirag M; White, Edward T; Litster, James D

    2012-01-01

    In this work, osmotic second virial coefficients (B(22)) were determined and correlated with the measured solubilities for the proteins, α-amylase, ovalbumin, and lysozyme. The B(22) values and solubilities were determined in similar solution conditions using two salts, sodium chloride and ammonium sulfate in an acidic pH range. An overall decrease in the solubility of the proteins (salting out) was observed at high concentrations of ammonium sulfate and sodium chloride solutions. However, for α-amylase, salting-in behavior was also observed in low concentration sodium chloride solutions. In ammonium sulfate solutions, the B(22) are small and close to zero below 2.4 M. As the ammonium sulfate concentrations were further increased, B(22) values decreased for all systems studied. The effect of sodium chloride on B(22) varies with concentration, solution pH, and the type of protein studied. Theoretical models show a reasonable fit to the experimental derived data of B(22) and solubility. B(22) is also directly proportional to the logarithm of the solubility values for individual proteins in salt solutions, so the log-linear empirical models developed in this work can also be used to rapidly predict solubility and B(22) values for given protein-salt systems. Copyright © 2011 American Institute of Chemical Engineers (AIChE).

  5. Ion aggregation in high salt solutions: ion network versus ion cluster.

    PubMed

    Kim, Seongheun; Kim, Heejae; Choi, Jun-Ho; Cho, Minhaeng

    2014-09-28

    The critical aggregation phenomena are ubiquitous in many self-assembling systems. Ions in high salt solutions could also spontaneously form larger ion aggregates, but their effects on hydrogen-bond structures in water have long been controversial. Here, carrying out molecular dynamics (MD) simulation studies of high salt solutions and comparing the MD simulation results with infrared absorption and pump-probe spectroscopy of O-D stretch mode of HDO in highly concentrated salt solutions and (13)C-NMR chemical shift of S(13)CN(-) in KSCN solutions, we find evidence on the onset of ion aggregate and large-scale ion-ion network formation that concomitantly breaks water hydrogen-bond structure in certain salt solutions. Despite that these experimental results cannot provide direct evidence on the three-dimensional morphological structures of ion aggregates, they serve as reference data for verifying MD simulation methods. The MD results suggest that disrupted water hydrogen-bond network is intricately intertwined with ion-ion network. This further shows morphological variation of ion aggregate structures from ion cluster to ion network in high salt solutions that are interrelated to the onset of macroscopic aggregate formation and the water hydrogen-bond structure making and breaking processes induced by Hofmeister ions.

  6. Ion aggregation in high salt solutions: Ion network versus ion cluster

    SciTech Connect

    Kim, Seongheun; Kim, Heejae; Choi, Jun-Ho; Cho, Minhaeng

    2014-09-28

    The critical aggregation phenomena are ubiquitous in many self-assembling systems. Ions in high salt solutions could also spontaneously form larger ion aggregates, but their effects on hydrogen-bond structures in water have long been controversial. Here, carrying out molecular dynamics (MD) simulation studies of high salt solutions and comparing the MD simulation results with infrared absorption and pump-probe spectroscopy of O–D stretch mode of HDO in highly concentrated salt solutions and {sup 13}C-NMR chemical shift of S{sup 13}CN{sup −} in KSCN solutions, we find evidence on the onset of ion aggregate and large-scale ion-ion network formation that concomitantly breaks water hydrogen-bond structure in certain salt solutions. Despite that these experimental results cannot provide direct evidence on the three-dimensional morphological structures of ion aggregates, they serve as reference data for verifying MD simulation methods. The MD results suggest that disrupted water hydrogen-bond network is intricately intertwined with ion-ion network. This further shows morphological variation of ion aggregate structures from ion cluster to ion network in high salt solutions that are interrelated to the onset of macroscopic aggregate formation and the water hydrogen-bond structure making and breaking processes induced by Hofmeister ions.

  7. Dissipative particle dynamics simulation of depletion layer and polymer migration in micro- and nanochannels for dilute polymer solutions.

    PubMed

    Fedosov, Dmitry A; Em Karniadakis, George; Caswell, Bruce

    2008-04-14

    The flows of dilute polymer solutions in micro- and nanoscale channels are of both fundamental and practical importance in variety of applications in which the channel gap is of the same order as the size of the suspended particles or macromolecules. In such systems depletion layers are observed near solid-fluid interfaces, even in equilibrium, and the imposition of flow results in further cross-stream migration of the particles. In this work we employ dissipative particle dynamics to study depletion and migration in dilute polymer solutions in channels several times larger than the radius of gyration (Rg) of bead-spring chains. We compare depletion layers for different chain models and levels of chain representation, solvent quality, and relative wall-solvent-polymer interactions. By suitable scaling the simulated depletion layers compare well with the asymptotic lattice theory solution of depletion near a repulsive wall. In Poiseuille flow, polymer migration across the streamlines increases with the Peclet and the Reynolds number until the center-of-mass distribution develops two symmetric off-center peaks which identify the preferred chain positions across the channel. These appear to be governed by the balance of wall-chain repulsive interactions and an off-center driving force of the type known as the Segre-Silberberg effect.

  8. Hydraulic conductivity of compacted clay liners permeated with inorganic salt solutions.

    PubMed

    Yilmaz, Gonca; Yetimoglu, Temel; Arasan, Seracettin

    2008-10-01

    Due to their low permeability, geosynthetic clay liners (GCLs) and compacted clay liners (CCLs) are the main materials used in waste disposal landfills. The hydraulic conductivity of GCLs and CCLs is closely related to the chemistry of the permeant fluid. In this study, the effect on the hydraulic conductivity of clays of five different inorganic salt solutions as permeant fluid was experimentally investigated. For this purpose, NaCl, NH(4)Cl, KCl, CaCl(2), and FeCl( 3) inorganic salt solutions were used at concentrations of 0.01, 0.10, 0.25, 0.50, 0.75 and 1 M. Laboratory hydraulic conductivity tests were conducted on low plasticity (CL) and high plasticity (CH) compacted raw clays. The change in electrical conductivity and pH values of the clay samples with inorganic salt solutions were also determined. The experimental test results indicated that the effect of inorganic salt solutions on CL clay was different from that on CH clay. The hydraulic conductivity was found to increase for CH clay when the salt concentrations increased whereas when the salt concentrations were increased, the hydraulic conductivity decreased for the CL clay.

  9. Analysis of Frozen Sulfate and Chloride Salt Solutions Using Laser-induced Breakdown Spectroscopy Under Martian Conditions

    NASA Astrophysics Data System (ADS)

    Schröder, S.; Pavlov, S. G.; Hübers, H.-W.; Rauschenbach, I.; Jessberger, E. K.

    2010-03-01

    We showed the feasibility of laser-induced breakdown spectroscopy to analyze different frozen salt solutions under martian conditions. We focused on chloride and sulphate salts which were found on Mars and could lower the freezing point of water.

  10. Self-diffusion coefficients of the trivalent f-element ion series in dilute and moderately dilute aqueous solutions: A comparative study between europium, gadolinium, terbium and berkelium

    NASA Astrophysics Data System (ADS)

    Rafik, Besbes; Noureddine, Ouerfelli; Abderabbou, Abdelmanef; Habib, Latrous

    2010-03-01

    We have continued the studies on the trivalent ions of the 4f and 5f elements. In this paper, we compare the transport properties (self-diffusion coefficient) of the trivalent aquo ions over two ranges of concentrations (0 — 2×10-3M) and (2×10-3 — 1.5M). Self-diffusion coefficients, D, of the trivalent f-element aquo ion series have been determined in aqueous background electrolytes of Gd(NO3)3 and Nd(ClO4)3, at pH=2.5 (HNO3, HClO4) and at 25°C using the open-end capillary method (O.E.C.M.). This method measures the transportation time of ions across a fixed distance. In this paper, we complete a measurement of self-diffusion coefficient for terbium. We optimized the pH to avoid hydrolysis, ion-pairing and complexation of the trivalent 4f and 5f ions. The variation of D versus √C is not linear for dilute solutions (0 — 2×10-3M) and quasi-linear in moderate concentrations (C<=1.5 M). Similar behavior was observed for Tb, as compared with those for Bk, Eu and Gd. We complete the comparison variation of D/D° versus √C for all studied 4f and 5f elements from concentration 0 to 1.5M and we obtained the same variation with √C for all studied elements. All 4f and 5f elements studied follow the Nernst-Hartley expression.

  11. The Solidification Velocity of Undercooled Nickel and Titanium Alloys with Dilute Solute

    NASA Technical Reports Server (NTRS)

    Algoso, Paul R.; Altgilbers, A. S.; Hofmeister, William H.; Bayuzick, Robert J.

    2003-01-01

    The study of solidification velocity is important for two reasons. First, understanding the manner in which the degree of undercooling of the liquid and solidification velocity affect the microstructure of the solid is fundamental. Second, there is disagreement between theoretical predictions of the relationship between undercooling and solidification velocity and experimental results. Thus, the objective of this research is to accurately and systematically quantify the solidification velocity as a function of undercooling for dilute nickel-and titanium-based alloys. The alloys chosen for study cover a wide range of equilibrium partition coefficients, and the results are compared to current theory.

  12. Effects of osmolytes on human brain-type creatine kinase folding in dilute solutions and crowding systems.

    PubMed

    Fan, Yong-Qiang; Lee, Jinhyuk; Oh, Sangho; Liu, Hong-Jian; Li, Chang; Luan, Yu-Shi; Yang, Jun-Mo; Zhou, Hai-Meng; Lü, Zhi-Rong; Wang, Yu-Long

    2012-12-01

    The effects of osmolytes on the unfolding and refolding process of recombinant human brain-type creatine kinase (rHBCK) were comparatively, quantitatively studied in dilute solutions and macromolecular crowding systems (simulated by 100 g/L polyethylene glycol 2000), respectively. The results showed that the osmolytes, including glycerol, sucrose, dimethylsulfoxide, mannitol, inositol, and xylitol, could both protect the rHBCK from denaturation induced by 0.8 M GdnHCl and aid in the refolding of denatured-rHBCK in macromolecular crowding systems. When we examined the effects of sucrose and xylitol on the parameters of residual activity, reaction kinetics and intrinsic fluorescence of rHBCK during unfolding, it was found that the protecting effects of osmolytes in a macromolecular crowding system were more significant compared with those in a dilute solution, which resulted in more residual activities, protected the conformational changes and greatly decreased the rates of both the fast and slow tracks. Regarding the effects of glycerol, sucrose and mannitol on the denatured-rHBCK refolding parameters of refolding yield, reaction kinetics and aggregation, the results indicated that the osmolytes could alleviate the aggregation of rHBCK during refolding in both dilute solutions and macromolecular crowding systems, and the refolding yields and reaction rates under macromolecular crowding environment could be increased by the addition of osmolytes, though higher yields were obtained in the dilute solution. For further insight, osmolyte docking simulations and rHBCK denaturation were conducted successfully and confirmed our experimental results. The predictions based on the docking simulations suggested that the deactivation of guanidine may be blocked by osmolytes because they share common binding sites on rHBCK, and the higher number of interactions with rHBCK by osmolytes than guanidine may be one of the causes of rHBCK refolding. In brief, the additive effects of

  13. ``Over the horizon`` SANS: Measurements on near-surface Poiseuille shear-induced ordering of dilute solutions of threadlike micelles

    SciTech Connect

    Hamilton, W.A.; Butler, P.D.; Hayter, J.B.; Magid, L.J.; Kreke, P.J.

    1995-06-24

    Although the behavior of a fluid under shear near a surface can be expected to be critically important to its drag and lubrication properties, most shear measurements to date have been of the bulk. This paper outlines the use of a specially developed Poiseuille shear cell at grazing incidence to measure the small-angle neutron scattering (SANS) signal from the first few tens of microns in the interfacial region. The authors illustrate the technique with measurements made on the near-surface ordering in flow past a quartz surface of dilute surfactant solutions comprising highly extended self-assembling ``threadlike`` micelles.

  14. Influence of adding salt on ultrasonic atomization in an ethanol-water solution.

    PubMed

    Hamai, Koumei; Takenaka, Norimichi; Nanzai, Ben; Okitsu, Kenji; Bandow, Hiroshi; Maeda, Yasuaki

    2009-01-01

    Ethanol was enriched by ultrasonic atomization. Enrichment ratios were increased by adding salt to the ethanol solution. Different enrichment ratios were observed for different types of salts in a range of low ethanol concentrations. The enrichment ratio was significantly improved by adding K(2)CO(3) or (NH(4))(2)SO(4). It is concluded that this is due to enhanced interfacial adsorption of the ethanol. Addition of Na(2)CO(3) to the ethanol solution also enhanced the interfacial adsorption of the ethanol, but the effect was relatively small. Addition of NaCl to the ethanol solution did not enhance the interfacial adsorption of the ethanol.

  15. Length Scale Dependence of the Dynamic Properties of Hyaluronic Acid Solutions in the Presence of Salt

    SciTech Connect

    Horkay, Ferenc; Falus, Peter; Hecht, Anne-Marie; Geissler, Erik

    2010-12-07

    In solutions of the charged semirigid biopolymer hyaluronic acid in salt-free conditions, the diffusion coefficient D{sub NSE} measured at high transfer momentum q by neutron spin echo is more than an order of magnitude smaller than that determined by dynamic light scattering, D{sub DLS}. This behavior contrasts with neutral polymer solutions. With increasing salt content, D{sub DLS} approaches D{sub NSE}, which is independent of ionic strength. Contrary to theoretical expectation, the ion-polymer coupling, which dominates the low q dynamics of polyelectrolyte solutions, already breaks down at distance scales greater than the Debye-Hueckel length.

  16. Lanthanide salts solutions: representation of osmotic coefficients within the binding mean spherical approximation.

    PubMed

    Ruas, Alexandre; Moisy, Philippe; Simonin, Jean-Pierre; Bernard, Olivier; Dufrêche, Jean-François; Turq, Pierre

    2005-03-24

    Osmotic coefficients of aqueous solutions of lanthanide salts are described using the binding mean spherical approximation (BIMSA) model based on the Wertheim formalism for association. The lanthanide(III) cation and the co-ion are allowed to form a 1-1 ion pair. Hydration is taken into account by introducing concentration-dependent cation size and solution permittivity. An expression for the osmotic coefficient, derived within the BIMSA, is used to fit data for a wide variety of lanthanide pure salt aqueous solutions at 25 degrees C. A total of 38 lanthanide salts have been treated, including perchlorates, nitrates, and chlorides. For most solutions, good fits could be obtained up to high ionic strengths. The relevance of the fitted parameters has been discussed, and a comparison with literature values has been made (especially the association constants) when available.

  17. Soaking turkey meat in salt-glucose syrup solutions--an experimental study of mass transfers.

    PubMed

    Deumier, F; Collignan, A; Bohuon, P

    2002-08-01

    Turkey meat can be salted and dried in one step by soaking in a concentrated salt-glucose syrup solution at low temperature. Sugar impregnation is minimal; only low molecular weight sugars generally penetrate the product. Glucose uptake is very quick, suggesting the possible involvement of passive glucose transporters. The operational scope of this process, depending on the targeted end-product features, was determined for turkey meat on the basis of clearly characterized mass transport phenomena between the product and the soaking solution. With 2 cm thick meat fillets processed at 10 C it is thus possible to obtain salted-dried end-products containing 2 to 10% salt and 35 to 70% water, ranges that are compatible with a broad range of commercial cured products.

  18. Meat batter production in an extended vane pump-grinder injecting curing salt solutions to reduce energy requirements: variation of curing salt amount injected with the solution.

    PubMed

    Irmscher, Stefan B; Terjung, Eva-Maria; Gibis, Monika; Herrmann, Kurt; Kohlus, Reinhard; Weiss, Jochen

    2017-01-01

    The integration of a nozzle in an extended vane pump-grinder system may enable the continuous injection of curing salt solutions during meat batter production. The purpose of this work was to examine the influence of the curing salt amount injected with the solution (0-100%) on protein solubilisation, water-binding, structure, colour and texture of emulsion-type sausages. The amount of myofibrillar protein solubilised during homogenisation varied slightly from 33 to 36 g kg(-1) . Reddening was not noticeably impacted by the later addition of nitrite. L(*) ranged from 66.9 ± 0.3 to 67.8 ± 0.3, a(*) from 10.9 ± 0.1 to 11.2 ± 0.1 and b(*) from 7.7 ± 0.1 to 8.0 ± 0.1. Although softer sausages were produced when only water was injected, firmness increased with increasing curing salt amount injected and was similar to the control when the full amount of salt was used. The substitution of two-thirds of ice with a liquid brine may enable energy savings due to reduced power consumptions of the extended vane pump-grinder system by up to 23%. The injection of curing salt solutions is feasible without affecting structure and colour negatively. This constitutes a first step towards of an 'ice-free' meat batter production allowing for substantial energy savings due to lower comminution work. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

  19. Not salt taste perception but self-reported salt eating habit predicts actual salt intake.

    PubMed

    Lee, Hajeong; Cho, Hyun-Jeong; Bae, Eunjin; Kim, Yong Chul; Kim, Suhnggwon; Chin, Ho Jun

    2014-09-01

    Excessive dietary salt intake is related to cardiovascular morbidity and mortality. Although dietary salt restriction is essential, it is difficult to achieve because of salt palatability. However, the association between salt perception or salt eating habit and actual salt intake remains uncertain. In this study, we recruited 74 healthy young individuals. We investigated their salt-eating habits by questionnaire and salt taste threshold through a rating scale that used serial dilution of a sodium chloride solution. Predicted 24-hr urinary salt excretions using Kawasaki's and Tanaka's equations estimated dietary salt intake. Participants' mean age was 35 yr, and 59.5% were male. Salt sense threshold did not show any relationship with actual salt intake and a salt-eating habit. However, those eating "salty" foods showed higher blood pressure (P for trend=0.048) and higher body mass index (BMI; P for trend=0.043). Moreover, a salty eating habit was a significant predictor for actual salt intake (regression coefficient [β] for Kawasaki's equation 1.35, 95% confidence interval [CI] 10-2.69, P=0.048; β for Tanaka's equation 0.66, 95% CI 0.01-1.31, P=0.047). In conclusion, a self-reported salt-eating habit, not salt taste threshold predicts actual salt intake.

  20. Conformational stability of alternating d (CG) oligomers in high salt solution.

    PubMed Central

    Quadrifoglio, F; Manzini, G; Vasser, M; Dinkelspiel, K; Crea, R

    1981-01-01

    The conformation of d (CG)n oligomers with n = 2,3 has been studied in aqueous solution in the presence of high salt concentration. A minimum n value of three is necessary to obtain a left-handed Z-helix. When d (CG)3 is flanked by three non Z-helicogenic alternating AT sequences the left-handed helix is unstable and a B-type conformation is obtained also at high salt concentration. PMID:6272229

  1. Fluid-loading solutions and plasma volume: Astro-ade and salt tablets with water

    NASA Technical Reports Server (NTRS)

    Fortney, Suzanne M.; Seinmann, Laura; Young, Joan A.; Hoskin, Cherylynn N.; Barrows, Linda H.

    1994-01-01

    Fluid loading with salt and water is a countermeasure used after space flight to restore body fluids. However, gastrointestinal side effects have been frequently reported in persons taking similar quantities of salt and water in ground-based studies. The effectiveness of the Shuttle fluid-loading countermeasure (8 gms salt, 0.97 liters of water) was compared to Astro-ade (an isotonic electrolyte solution), to maintain plasma volume (PV) during 4.5 hrs of resting fluid restriction. Three groups of healthy men (n=6) were studied: a Control Group (no drinking), an Astro-ade Group, and a Salt Tablet Group. Changes in PV after drinking were calculated from hematocrit and hemoglobin values. Both the Salt Tablet and Astro-ade Groups maintained PV at 2-3 hours after ingestion compared to the Control Group, which had a 6 percent decline. Side effects (thirst, stomach cramping, and diarrhea) were noted in at least one subject in both the Astro-ade and Salt Tablet Groups. Nausea and vomiting were reported in one subject in the Salt Tablet Group. It was concluded that Astro-ade may be offered as an alternate fluid-loading countermeasure but further work is needed to develop a solution that is more palatable and has fewer side effects.

  2. [Solubilization of nitrobenzene in micellar solutions of Tween 80 and inorganic salts].

    PubMed

    Li, Sui; Zhao, Yong-sheng; Xu, Wei; Dai, Ning

    2008-04-01

    The solubilization of nitrobenzene by a nonionic surfactant Tween 80 was investigated at 10 degrees C. Experimental results indicated that the solubility of nitrobenzene in water was greatly enhanced by Tween 80 at surfactant concentration above CMC(critical micelle concentration) and a linear relationship was obtained between surfactant concentration and nitrobenzene concentration from the solubility curve. The molar solubilization ratio (MSR) value was 5.093 and IgKm was 3.499. The solubilization was attributed to the ethoxylation group in Tween 80 micellar. Effect of four inorganic salts such as NaCl, KCl, CaCl2 , MgCl2 on water solubilities of nitrobenzene in Tween 80 micellar solutions was also investigated by a matrix of batch experiments. Mix the Tween 80-inorganic salts at the total mass ratios of 2:1, 5:1 and 10:1. The results show that the inorganic salts at a high concentration( > or = 500 mg x L(-1)) can enhance the solubilization capacities of Tween 80 micellar solution and increase the value of MSR and IgKm . Because of the salting-out effect between the micellar of Tween 80 and inorganic salts, the volume of micelle turns bigger, which may provide larger solubility volume for nitrobenzene. The mixture of nonionic surfactant and inorganic salts can be used in subsurface remediation as a flushing solution.

  3. Morphological study of magnesium hydroxide nanoparticles precipitated in dilute aqueous solution

    NASA Astrophysics Data System (ADS)

    Henrist, C.; Mathieu, J.-P.; Vogels, C.; Rulmont, A.; Cloots, R.

    2003-02-01

    Among other applications, magnesium hydroxide is commonly used as a flame-retardant filler in composite materials, as well as a precursor for magnesium oxide refractory ceramic. The microstructure of the powder is of prime importance in both technical applications. The influence of synthesis parameters on the morphological characteristics of magnesium hydroxide nanoparticles precipitated in dilute aqueous medium was studied. Several parameters were envisaged such as chemical nature of the base precipitant, type of counter-ion, temperature and hydrothermal treatment. Special attention was given to the obtaining of platelet-shaped, nanometric and de-agglomerated powders. The powders were characterized in terms of particle size distribution, crystal habits, morphology and ability to be re-dispersed in water. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption and laser diffusion analyses were used for this purpose.

  4. Highly charged ions in a dilute plasma: an exact asymptotic solution involving strong coupling.

    PubMed

    Brown, Lowell S; Dooling, David C; Preston, Dean L

    2006-05-01

    The ion sphere model introduced long ago by Salpeter is placed in a rigorous theoretical setting. The leading corrections to this model for very highly charged but dilute ions in thermal equilibrium with a weakly coupled, one-component background plasma are explicitly computed, and the subleading corrections shown to be negligibly small. This is done using the effective field theory methods advocated by Brown and Yaffe. Thus, corrections to nuclear reaction rates that such highly charged ions may undergo can be computed precisely. Moreover, their contribution to the equation of state can also be computed with precision. Such analytic results for very strong coupling are rarely available, and they can serve as benchmarks for testing computer models in this limit.

  5. Production of ethyl acetate from dilute ethanol solutions by Candida utilis

    SciTech Connect

    Armstrong, D.W.; Martin, S.M.; Yamazaki, H.

    1984-01-01

    The conversion of ethanol to ethyl acetate has an advantage as a method of ethanol recovery since ethyl acetate is amenable to simple solvent extraction. The potential of Candida utilis in this conversion was studied. The kinetics of accumulation of ethanol and ethyl acetate in glucose-grown C. utilis showed that ester formation resulted from ethanol utilization under appropriate aeration and was inhibited by Fe/sup 3 +/ supplementation. Candida utilis converted ethanol to ethyl acetate optimally at pH 5.0-7.0. The five-hour rate of ester production increased as the ethanol concentration increased to 10 g/L, and rapidly declined to zero at concentrations exceeding 35 g/L. Thus, C. utilis has potential to recover dilute ethanol in the form of ethyl acetate.

  6. Structure impact of two galactomannan fractions on their viscosity properties in dilute solution, unperturbed state and gel state.

    PubMed

    Gillet, Sébastien; Aguedo, Mario; Petrut, Raul; Olive, Gilles; Anastas, Paul; Blecker, Christophe; Richel, Aurore

    2017-03-01

    Two fractions of carob galactomannans (GM25 and GM80) were extracted at respectively 25°C and 80°C from crude locust bean gum. Those fractions having slightly different chemical structures, previously characterized, were studied for their viscosity properties over a wide range of concentrations: diluted solution, unperturbed state and gel state. For each of the physical properties, links to the chemical fine structure could be established, expanding knowledge on the topic: in dilute solution, GM25 is more soluble in water while GM80 seems to tend to self-association due to its structure as highlighted by intrinsic viscosity measurements ([η]GM25=9.96dLg(-1) and [η]GM80=4.04dLg(-1)). In unperturbed state, initial viscosities η0 were more important for GM80 fractions at 1% and 2% due to greater hyperentanglements (η0(GM80,1%)=9.9Pas; η0(GM80,2%)=832.0; Pa.s η0(GM25,1%)=3.1Pas; η0(GM25,2%)=45.1Pas). In gel state, hydrogels obtained from GM80 were also stronger (hardness GM80 (2%)=0.51N and hardness GM25 (2%)=0.11N), suggesting a much more important number of junction areas within the gel network. The findings discussed herein demonstrate the potential for new applications.

  7. Activity coefficients at infinite dilution of organic solutes in the ionic liquid 1-ethyl-3-methyl-imidazolium nitrate.

    PubMed

    Sobota, Marek; Dohnal, Vladimír; Vrbka, Pavel

    2009-04-02

    Infinite dilution activity coefficients gamma(1)(infinity) and gas-liquid partition coefficients K(L) of 30 selected hydrocarbons, alcohols, ketones, ethers, esters, haloalkanes, nitrogen- and sulfur-containing compounds in the ionic liquid (IL) 1-ethyl-3-methylimidazolium nitrate [EMIM][NO(3)] were determined by gas-liquid chromatography at five temperatures in the range from 318.15 to 353.15 K. Relative contribution of adsorption at gas-liquid interphase to the overall solute retention, as examined by varying sample size and IL loading in the column, was found negligible. Partial molar excess enthalpies and entropies at infinite dilution were derived from the temperature dependence of the gamma(1)(infinity) values. The linear free energy relationship (LFER) solvation model was used to correlate successfully the KL values. The LFER correlation parameters and excess thermodynamic functions were analyzed to disclose molecular interactions operating between the IL and the individual solutes. In addition, the promising potential of [EMIM][NO(3)] for applications in solvent-aided separation processes was identified, the selectivities of [EMIM][NO(3)] for separation of aromatic hydrocarbons and thiophene from saturated hydrocarbons ranking among the highest ever observed with ILs or molecular solvents.

  8. Using temperature-programmed reaction for kinetic analysis of reactions in dilute aqueous solutions at high pressure

    SciTech Connect

    Brown, L.F.; Robinson, B.A.

    1986-01-01

    The technique of temperature-programmed reaction (TPR) is shown to be a practical experimental method for determining reaction-rate expressions and kinetics parameters for reactions in dilute aqueous solutions under high ambient pressure. By sampling and measuring the extent of reaction during a rise in temperature, information normally obtained from a series of isothermal batch kinetics experiments can be found in a single TPR test. The use of nonlinear least-squares regression eliminates the need to achieve a constant rate of temperature rise, simplifies the experimental requirements for TPR results, and gives more accurate answers than does a linear analysis of TPR results. Numerical simulations of TPR tests in the presence of random concentration-measurement error is used to assess the accuracy of the technique and to identify the best values of crucial operating parameters. The results of two TPR experiments measuring the alkaline hydrolysis of ethyl acetate demonstrate the applicability of the technique to reactions in dilute aqueous solutions at high pressure. These preliminary experimental results, along with numerical simulations, allow us to chart a course for future TPR kinetics experiments on a large number of similar reactions. 16 refs., 6 figs., 8 tabs.

  9. Solution by dilution?--A review on the pollution status of the Yangtze River.

    PubMed

    Floehr, Tilman; Xiao, Hongxia; Scholz-Starke, Björn; Wu, Lingling; Hou, Junli; Yin, Daqiang; Zhang, Xiaowei; Ji, Rong; Yuan, Xingzhong; Ottermanns, Richard; Roß-Nickoll, Martina; Schäffer, Andreas; Hollert, Henner

    2013-10-01

    The Yangtze River has been a source of life and prosperity for the Chinese people for centuries and is a habitat for a remarkable variety of aquatic species. But the river suffers from huge amounts of urban sewage, agricultural effluents, and industrial wastewater as well as ship navigation wastes along its course. With respect to the vast amounts of water and sediments discharged by the Yangtze River, it is reasonable to ask whether the pollution problem may be solved by simple dilution. This article reviews the past two decades of published research on organic pollutants in the Yangtze River and several adjacent water bodies connected to the main stream, according to a holistic approach. Organic pollutant levels and potential effects of water and sediments on wildlife and humans, measured in vitro, in vivo, and in situ, were critically reviewed. The contamination with organic pollutants, including polycyclic aromatic hydrocarbons, polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans, polybrominated diphenyl ethers (PBDEs), perfluorinated compounds (PFCs), and others, of water and sediment along the river was described. Especially Wuhan section and the Yangtze Estuary exhibited stronger pollution than other sections. Bioassays, displaying predominantly the endpoints mutagenicity and endocrine disruption, applied at sediments, drinking water, and surface water indicated a potential health risk in several areas. Aquatic organisms exhibited detectable concentrations of toxic compounds like PCBs, OCPs, PBDEs, and PFCs. Genotoxic effects could also be assessed in situ in fish. To summarize, it can be stated that dilution reduces the ecotoxicological risk in the Yangtze River, but does not eliminate it. Keeping in mind an approximately 14 times greater water discharge compared to the major European river Rhine, the absolute pollution mass transfer of the Yangtze River is of severe concern for

  10. On the internal field correction in far-infrared absorption of highly polar molecules in neat liquids and dilute solutions

    NASA Astrophysics Data System (ADS)

    Vij, J. K.; Kalmykov, Yu P.

    1993-08-01

    Far-infrared absorption spectra for liquid acetone, methylene chloride, acetonitrile, methyl iodide, and their dilute solutions in cyclohexane at 20 °C are measured by molecular laser spectrometer. Measurements of dielectric loss of polar liquids and solutions in the frequency range 2-300 GHz are made using a number of different techniques. These two sets of measurements are combined with those made using a Fourier transform spectrometer in order to cover the frequency range up to 250 cm-1 and total integrated absorption intensities are calculated. It is shown that the discrepancy between experimental integrated absorption and the theoretical results given by Gordon's sum rule with the Polo-Wilson internal field factor can be explained in the context of Bossis' theory. This theory gives a better agreement with the experimental integrated absorption intensity for these liquids.

  11. Dynamic light scattering studies on charged rod-like fd-virus in dilute aqueous solution

    NASA Astrophysics Data System (ADS)

    Schulz, Susanne F.; Maier, Erich E.; Krause, Rainer; Hagenbüchle, Martin; Deggelmann, Martin; Weber, Reinhart

    1990-06-01

    Time correlation functions of the scattered light intensity are studied in aqueous solutions of charged rod-like fd-virus (L=880 nm, d=6 nm) at various ionic strengths. The short time behavior of the correlation function is dominated by the static structure factor S(q) which is also independently determined from static light scattering experiments. Comparison of correlation functions of solutions with high ionic strength (screened Coulomb interaction) and those of solutions with liquid-like nearest neighbor order (strong Coulomb interaction) shows different single particle diffusion coefficients on medium time scales at high scattering vectors, where mainly single particle properties are observed by light scattering. The single particle diffusion coefficient decreases with increasing structure peak height of the solutions. At low scattering vectors an extra slow mode component of the correlation function is observed for solutions with Coulomb interaction.

  12. Transition metal salt solutions and anaerobic adhesives in dental bonding.

    PubMed

    Ireland, A J; Sherriff, M

    1999-07-01

    The objectives of this experiment were twofold. Firstly to determine whether an anaerobic adhesive could be used to bond steel attachments to etched human enamel, following treatment of this surface with various concentrations of copper (II) sulphate solution. Secondly, to determine the effect of 0.05 M solutions of other transition metal sulphates and chlorides on the same bonding process. Stainless steel attachments were bonded to human enamel using an anaerobic adhesive. In each case the enamel, which had been ground flat, was etched with 37% o-phosphoric acid and then treated with copper (II) sulphate solution prior to bonding. After bench curing for one hour, the specimens were shear tested to failure, and the load at bebond recorded in each case. The effect of varying the concentration of copper (II) sulphate solution was determined. Following determination of the optimal copper (II) sulphate concentration, the experiment was repeated using the same concentration of various other transition metal sulphates and chlorides. The results were analysed using mean force to debond (N) and 95% confidence intervals. Kaplan-Meier survival probabilities and log-rank tests were also performed. Under the conditions of this experiment the optimal concentration of copper (II) sulphate solution was found to be 0.05 M. Of the various transition metal sulphates and chlorides under test, the sulphates appeared to provide a more active surface for the polymerisation of the anaerobic adhesive than the chlorides. Of the sulphate solutions, the most effective was that of copper. Anaerobic adhesives show promise as dental bonding agents capable of bonding metal attachments to enamel following enamel pretreatment with 0.05 M copper (II) sulphate solution.

  13. Rapid recovery of dilute copper from a simulated Cu-SDS solution with low-cost steel wool cathode reactor.

    PubMed

    Chang, Shih-Hsien; Wang, Kai-Sung; Hu, Pei-I; Lui, I-Chun

    2009-04-30

    Copper-surfactant wastewaters are often encountered in electroplating, printed circuit boards manufacturing, and metal finishing industries, as well as in retentates from micellar-enhanced ultrafiltration process. A low-cost three-dimensional steel wool cathode reactor was evaluated for electrolytic recovery of Cu ion from dilute copper solution (0.2mM) in the presence of sodium dodecyl sulfate (SDS), octylphenol poly (ethyleneglycol) 9.5 ether (TX), nonylphenol poly (oxyethylene) 9 ether (NP9) and polyoxyethylene (20) sorbitan monooleate (TW) and also mixed surfactants (anionic/nonionic). The reactor showed excellent copper recovery ability in comparison to a parallel-plate reactor. The reactor rapidly recovered copper with a reasonable current efficiency. 93% of copper was recovered at current density of 1 A m(-2) and pH 4 in the presence of 8.5mM SDS. Initial solution pH, cathodic current density, solution mixing condition, SDS concentration, and initial copper concentrations significantly influenced copper recovery. The copper recovery rate increased with an increase in aqueous SDS concentrations between 5 and 8.5mM. The influences of nonionic surfactants on Cu recovery from SDS-Cu solution depended not only on the type of surfactants used, but also on applied concentrations. From the copper recovery perspective, TX at 0.1mM or NP should be selected rather than TW, because they did not inhibit copper recovery from SDS-Cu solution.

  14. Conformation of ionizable poly Para phenylene ethynylene in dilute solutions

    SciTech Connect

    Wijesinghe, Sidath; Maskey, Sabina; Perahia, Dvora; Grest, Gary S.

    2015-11-03

    The conformation of dinonyl poly para phenylene ethynylenes (PPEs) with carboxylate side chains, equilibrated in solvents of different quality is studied using molecular dynamics simulations. PPEs are of interest because of their tunable electro-optical properties, chemical diversity, and functionality which are essential in wide range of applications. The polymer conformation determines the conjugation length and their assembly mode and affects electro-optical properties which are critical in their current and potential uses. The current study investigates the effect of carboxylate fraction on PPEs side chains on the conformation of chains in the dilute limit, in solvents of different quality. The dinonyl PPE chains are modeled atomistically, where the solvents are modeled both implicitly and explicitly. Dinonyl PPEs maintained a stretched out conformation up to a carboxylate fraction f of 0.7 in all solvents studied. The nonyl side chains are extended and oriented away from the PPE backbone in toluene and in implicit good solvent whereas in water and implicit poor solvent, the nonyl side chains are collapsed towards the PPE backbone. Thus, rotation around the aromatic ring is fast and no long range correlations are seen within the backbone.

  15. Salting-out effect in aqueous NaCl solutions: trends with size and polarity of solute molecules.

    PubMed

    Endo, Satoshi; Pfennigsdorff, Andrea; Goss, Kai-Uwe

    2012-02-07

    Salting-out in aqueous NaCl solutions is relevant for the environmental behavior of organic contaminants. In this study, Setschenow (or salting-out) coefficients (K(s) [M(-1)]) for 43 diverse neutral compounds in NaCl solutions were measured using a shared headspace passive dosing method and a negligible depletion solid phase microextraction technique. The results were used to calibrate and evaluate estimation models for K(s). The molar volume of the solute correlated only moderately with K(s) (R(2) = 0.49, SD = 0.052). The polyparameter linear free energy relationship (pp-LFER) model that uses five compound descriptors resulted in a more accurate fit to our data (R(2) = 0.83, SD = 0.031). The pp-LFER analysis revealed that Na(+) and Cl(-) in aqueous solutions increase the cavity formation energy cost and the polar interaction energies toward neutral organic solutes. Accordingly, the salting-out effect increases with the size and decreases with the polarity of the solute molecule. COSMO-RS, a quantum mechanics-based fully predictive model, generally overpredicted the experimental K(s), but the predicted values were moderately correlated with the experimental values (R(2) = 0.66, SD = 0.042). Literature data (n = 93) were predicted by the calibrated pp-LFER and COSMO-RS models with root mean squared errors of 0.047 and 0.050, respectively. This study offers prediction models to estimate K(s), allowing implementation of the salting-out effect in contaminant fate models, linkage of various partition coefficients (such as air-water, sediment-water, and extraction phase-water partition coefficients) measured for fresh water and seawater, and estimation of enhancement of extraction efficiency in analytical procedures.

  16. Issues affecting storage of compressed air in solution-mined salt cavities

    SciTech Connect

    Allen, R.D.; Doherty, T.J.; Thoms, R.L.

    1982-04-01

    Geologic factors affecting salt deposit acceptability for CAES include diameter, depth, thickness, mineralogy, strength, faulting, seismic susceptibility, caprock quality and rate of dissolution by ground water. Assessment of a site involves analysis of existing information, seismic surveying, exploratory drilling, salt and caprock examination, geophysical logging, in situ stress measurement, and determination of hydrologic impact. Geologic exploration and solution mining at Huntorf, Federal Republic of Germany, are discussed. Cavern design parameters include octahedral shear strength, excess lateral stress, depth to cavern top, lateral salt thickness, vertical salt thickness, span, and height-to-diameter ratio. Noncompensated cavern operation involves cycling with respect to temperature, pressure, humidity and water. Cavern, borehole and surface monitoring methods are discussed.

  17. Acemetacin cocrystals and salts: structure solution from powder X-ray data and form selection of the piperazine salt.

    PubMed

    Sanphui, Palash; Bolla, Geetha; Nangia, Ashwini; Chernyshev, Vladimir

    2014-03-01

    Acemetacin (ACM) is a non-steroidal anti-inflammatory drug (NSAID), which causes reduced gastric damage compared with indomethacin. However, acemetacin has a tendency to form a less soluble hydrate in the aqueous medium. We noted difficulties in the preparation of cocrystals and salts of acemetacin by mechanochemical methods, because this drug tends to form a hydrate during any kind of solution-based processing. With the objective to discover a solid form of acemetacin that is stable in the aqueous medium, binary adducts were prepared by the melt method to avoid hydration. The coformers/salt formers reported are pyridine carboxamides [nicotinamide (NAM), isonicotinamide (INA), and picolinamide (PAM)], caprolactam (CPR), p-aminobenzoic acid (PABA), and piperazine (PPZ). The structures of an ACM-INA cocrystal and a binary adduct ACM-PABA were solved using single-crystal X-ray diffraction. Other ACM cocrystals, ACM-PAM and ACM-CPR, and the piperazine salt ACM-PPZ were solved from high-resolution powder X-ray diffraction data. The ACM-INA cocrystal is sustained by the acid⋯pyridine heterosynthon and N-H⋯O catemer hydrogen bonds involving the amide group. The acid⋯amide heterosynthon is present in the ACM-PAM cocrystal, while ACM-CPR contains carboxamide dimers of caprolactam along with acid-carbonyl (ACM) hydrogen bonds. The cocrystals ACM-INA, ACM-PAM and ACM-CPR are three-dimensional isostructural. The carboxyl⋯carboxyl synthon in ACM-PABA posed difficulty in assigning the position of the H atom, which may indicate proton disorder. In terms of stability, the salts were found to be relatively stable in pH 7 buffer medium over 24 h, but the cocrystals dissociated to give ACM hydrate during the same time period. The ACM-PPZ salt and ACM-nicotinamide cocrystal dissolve five times faster than the stable hydrate form, whereas the ACM-PABA adduct has 2.5 times faster dissolution rate. The pharmaceutically acceptable piperazine salt of acemetacin exhibits superior

  18. Acemetacin cocrystals and salts: structure solution from powder X-ray data and form selection of the piperazine salt

    PubMed Central

    Sanphui, Palash; Bolla, Geetha; Nangia, Ashwini; Chernyshev, Vladimir

    2014-01-01

    Acemetacin (ACM) is a non-steroidal anti-inflammatory drug (NSAID), which causes reduced gastric damage compared with indomethacin. However, acemetacin has a tendency to form a less soluble hydrate in the aqueous medium. We noted difficulties in the preparation of cocrystals and salts of acemetacin by mechanochemical methods, because this drug tends to form a hydrate during any kind of solution-based processing. With the objective to discover a solid form of acemetacin that is stable in the aqueous medium, binary adducts were prepared by the melt method to avoid hydration. The coformers/salt formers reported are pyridine carboxamides [nicotinamide (NAM), isonicotinamide (INA), and picolinamide (PAM)], caprolactam (CPR), p-aminobenzoic acid (PABA), and piperazine (PPZ). The structures of an ACM–INA cocrystal and a binary adduct ACM–PABA were solved using single-crystal X-ray diffraction. Other ACM cocrystals, ACM–PAM and ACM–CPR, and the piperazine salt ACM–PPZ were solved from high-resolution powder X-ray diffraction data. The ACM–INA cocrystal is sustained by the acid⋯pyridine heterosynthon and N—H⋯O catemer hydrogen bonds involving the amide group. The acid⋯amide heterosynthon is present in the ACM–PAM cocrystal, while ACM–CPR contains carboxamide dimers of caprolactam along with acid–carbonyl (ACM) hydrogen bonds. The cocrystals ACM–INA, ACM–PAM and ACM–CPR are three-dimensional isostructural. The carboxyl⋯carboxyl synthon in ACM–PABA posed difficulty in assigning the position of the H atom, which may indicate proton disorder. In terms of stability, the salts were found to be relatively stable in pH 7 buffer medium over 24 h, but the cocrystals dissociated to give ACM hydrate during the same time period. The ACM–PPZ salt and ACM–nicotinamide cocrystal dissolve five times faster than the stable hydrate form, whereas the ACM–PABA adduct has 2.5 times faster dissolution rate. The pharmaceutically acceptable piperazine

  19. Ion aggregation in high salt solutions. VI. Spectral graph analysis of chaotropic ion aggregates

    NASA Astrophysics Data System (ADS)

    Choi, Jun-Ho; Cho, Minhaeng

    2016-11-01

    Carrying out molecular dynamics simulations and graph theoretical analyses of high salt solutions, and comparing numerically calculated vibrational spectroscopic properties of water with femtosecond IR pump-probe experimental data, we have recently found that ions in high salt solutions can form two morphologically different ion aggregate structures. In the cases of NaCl solutions, Na+ and Cl- tend to form compact cluster-like ion aggregate in high NaCl solutions. In contrast, K+ and SCN- form spatially extended network-like ion aggregates that also exhibit a percolating network behavior. Interestingly, a variety of graph theoretical properties of ion network in high KSCN solutions were found to be very similar to those of water H-bonding network. It was shown that spatially extended ion networks in high KSCN solutions are completely intertwined with water H-bonding networks, which might be the key to understand the high solubility of thiocyanate salts in water. Here, we further consider two salts that have been extensively studied experimentally by using femtosecond IR pump-probe technique, which are NaClO4 and NaBF4. Note that ClO4 - and BF4 - are well-known chaotropic ions that have been believed to behave as water structure breaker. To understand how such chaotropic ions affect water H-bonding structure, we carried out spectral graph analyses of molecular dynamics simulation data of these aqueous solutions. Graph spectra and degree distribution of ion aggregates formed in high NaBF4 and NaClO4 solutions show that these chaotropic anions also have a strong propensity to form ion networks. The fact that salts containing chaotropic ions like SCN-, BF4 - , and ClO4 - have very high solubility limits in water could then be related to our observation that these chaotropic anions with counter cations in high salt solutions are capable of forming intricate ion networks intertwined with water H-bonding networks. We anticipate that the present graph theoretical analysis

  20. Balanced versus unbalanced salt solutions: what difference does it make?

    PubMed

    Magder, Sheldon

    2014-09-01

    The infusion of crystalloid solutions is a fundamental part of the management of critically ill patients. These solutions are used to maintain the balance of water and essential electrolytes and replace losses when patients have limited gastrointestinal intake. They also act as carriers for intravenous infusion of medication and red cells. The most commonly used solution, 0.9% saline, has equal concentrations of Na(+) and Cl(-) even though the plasma concentration of Na(+) normally is 40 meq/L higher than that of Cl(-). The use of this fluid thus can produce a hyperchloremic acidosis in a dose-dependent manner, but it is not known whether this has clinical significance. The first part of this article deals with the significance of Na(+) and Cl(-) in normal physiology. This begins with examination of their roles in the regulation of osmolality, acid-base balance, and generation of electrochemical gradients and why the concentration of Cl(-) normally is considerably lower than that of Na(+). The next part deals with how their concentrations are regulated by the gastrointestinal tract and kidney. Based on the physiology, it would seem that solutions in which the concentration of Na(+) is "balanced" by a substance other than Cl(-) would be advantageous. The final part examines the evidence to support that point. There are strong observational data that support the notion that avoiding an elevated Cl(-) concentration or using fluids that reduce the rise in Cl(-) reduces renal dysfunction, infections, and possibly even mortality. However, observational studies only can indicate an association and cannot indicate causality. Unfortunately, randomized trials to date are far too limited to address this crucial issue. What is clear is that appropriate randomized trials will require very large populations. It also is not known whether the important variable is the concentration of Cl(-), the difference in concentrations of Na(+) and Cl(-), or the total body mass of Cl

  1. A method for measuring enthalpy of volatilization of a compound, Delta(vol)H, from dilute aqueous solution.

    PubMed

    Wang, Tianshu

    2006-01-01

    This study has developed a method for measuring the enthalpy of volatilization (Delta(vol)H) of a compound in a dilute solution via ion-molecule reactions and gas-phase analysis using selected ion flow tube mass spectrometry (SIFT-MS). The Delta(vol)H/R value was obtained using an equation with three variant forms either from the headspace concentration of the solution or from individual product ion(s). Under certain experimental conditions, the equation has the simplest form [formula: see text], where R is the gas constant (8.314 J . mol(-1) . K(-1)), i(n) and I are the respective product and precursor ion count rates, and T is the temperature of the solution. As an example, a series of 27.0 micromol/L aqueous solutions of acetone was analyzed over a temperature range of 25-50 degrees C at 5 degrees C intervals using H3O+, NO+ and O2+* precursor ions, producing a mean Delta(vol)H/R value of 4700 +/- 200 K. This corresponds with current literature values and supports the consistency of the new method. Notably, using this method, as long as the concentration of the solution falls into the range of Henry's law, the exact concentration does not have to be known and it can require only one sample at each temperature. Compared with previous methods which involve the measurement of Henry's law constant at each temperature, this method significantly reduces the number of samples required and avoids the labour and difficulties in preparing standard solutions at very low concentrations. Further to this, if the contents of a solution were unknown the measured Delta(vol)H/R from individual product ion(s) can help to identify the origin of the ion(s).

  2. Changes in Proton Dynamics in Articular Cartilage Caused by Phosphate Salts and Fixation Solutions.

    PubMed

    Zheng, Shaokuan; Xia, Yang

    2010-01-01

    The objective was to study the effect of phosphate salts and fixation solutions on the proton dynamics in articular cartilage in vitro. Microscopic magnetic resonance imaging (μMRI) T(2) anisotropy and nuclear magnetic resonance (NMR) double quantum-filtered (DQF) spectroscopy were used to study the full-thickness articular cartilage from several canine humeral heads. The in-plane pixel size across the depth of the cartilage tissue was 13 μm. The acid phosphate salt was an effective exchange catalyst for proton exchange in the cartilage with an organized structure of collagen fibrils, while the alkaline phosphate salt was not. For cartilage tissue containing less organized collagen fibrils, both acid and alkaline phosphate salts have no significant effect on the T(2) value at low concentration but decrease the T(2) value at high concentration. The solutions of NaCl, KCl, CaCl(2), and D-PBS were found to have no significant effect on T(2) and DQF in cartilage. This study demonstrates the ability to modify the proton exchange in articular cartilage using the solutions of phosphate salts. The ability to modify the proton exchange in articular cartilage can be used to modulate the laminar appearance of articular cartilage in MRI.

  3. Separation of compounds with multiple -OH groups from dilute aqueous solutions via complexation with organoboronate

    SciTech Connect

    Chow, Tina Kuo Fung

    1992-05-01

    The complexing extractant agent investigated in this work is 3-nitrophenylboronic acid (NPBA) in its anionic form (NPB). NPBA and Aliquat 336 (quaternary amine) is dissolved in 2-ethyl-l-hexanol, and the extractant is contacted with aq. NaOH. Solutes investigated were 1,2-propanediol, glycerol, fructose, sorbitol and lactic acid. Batch extraction experiments were performed at 25°C. Partition coefficients, distribution ratios and loadings are reported for varying concentrations of solute and NPB. All solutes complexed with NPB-, with all complexes containing only one NPB- per complex. The 1:1 complexation constants for the solutes glycerol, fructose and sorbitol follow trends similar to complexation with B(OH)4- (aq.), i.e. the complexation constants increase with increasing number of -OH groups available for complexation. Assumption of 1:1 complex is not valid for 1, 2-propanediol, which showed overloading (more than one mole of solute complexed to one mole NPB-) at higher concentrations. The -OH group on the NPB- which is left uncomplexed after one solute molecule had bound to the other two -OH groups may be responsible for the overloading. Overloading is also observed in extraction of tactic acid, but through a different mechanism. It was found that TOMA+ can extract lactic acid to an extent comparable to the uptake of lactic acid by NPB-. The complexation is probably through formation of an acid-base ion pair. Losses of NPBA into the aqueous phase could lead to problems, poor economics in industrial separation processes. One way of overcoming this problem would be to incorporate the NPBA onto a solid support.

  4. Effect of Aging Temperature on Corrosion Behavior of Sintered 17-4 PH Stainless Steel in Dilute Sulfuric Acid Solution

    NASA Astrophysics Data System (ADS)

    Szewczyk-Nykiel, Aneta; Kazior, Jan

    2017-07-01

    The general corrosion behavior of sintered 17-4 PH stainless steel processed under different processing conditions in dilute sulfuric acid solution at 25 °C was studied by open-circuit potential measurement and potentiodynamic polarization technique. The corrosion resistance was evaluated based on electrochemical parameters, such as polarization resistance, corrosion potential, corrosion current density as well as corrosion rate. The results showed that the precipitation-hardening treatment could significantly improve the corrosion resistance of the sintered 17-4 PH stainless steel in studied environment. As far as the influence of aging temperature on corrosion behavior of the sintered 17-4 PH stainless steel is concerned, polarization resistance and corrosion rate are reduced with increasing aging temperature from 480 up to 500 °C regardless of the temperature of solution treatment. It can be concluded that the highest corrosion resistance in 0.5 M H2SO4 solution exhibits 17-4 PH after solution treatment at 1040 °C followed by aging at 480 °C.

  5. Electrochemical polarization and stress corrosion cracking behaviors of a pipeline steel in dilute bicarbonate solution with chloride ion

    SciTech Connect

    Liu, X.; Mao, X.

    1995-07-01

    The electrochemical and stress corrosion cracking behavior of Grade 550 (X-80) pipeline steel with coating disbandments was studied in a range of bicarbonate solutions using a potentiodynamic polarization technique and slow strain rate test. The shape of the polarization curves were found to vary with bicarbonate concentration. Increase in bicarbonate concentration results in a wider passive region and a more noble breakdown potential. Low concentrations of chloride ion in bicarbonate greatly affect the polarization characteristics and can cause the elimination of passivity in specific solutions. Tensile specimens were pulled at constant strain rate {dot {epsilon}} = 10{sup {minus}6}/sec. under potential control ranging from {minus}350 mV to {minus}900 mV (SCE) in NS-4 solution (dilute bicarbonate solution with chloride ion). Fracture surface of the specimens were examined under scanning electron microscopy. Overall fracture is ductile dimple, however, transgranular stress corrosion cracking has been found in the edge of specimen for the sample with potential controlled at {minus}800 mV, {minus}750 mV and {minus}650 mV (SCE).

  6. Effect of aging on aluminum hydroxide complexes in dilute aqueous solutions

    USGS Publications Warehouse

    Smith, Ross Wilbert; Hem, John David

    1972-01-01

    Aqueous aluminum solutions containing 4?10 -5 mole/liter aluminum and a constant total ionic strength of 10 -2, but with varying ratios of hydroxide to aluminum (OH:Al), were prepared. Progress of these solutions toward equilibrium conditions over aging periods of as much as 2 years was studied by determining the composition and pH of the solutions at various time intervals. The solutions, after mixing, were supersaturated with respect to both crystalline and amorphous forms of aluminum oxides and aluminum hydroxides. The compositions of the solutions were determined by use of a timed colorimetric analytical procedure which allowed the estimation of three separate forms of aluminum that have been designated Al a, Al b, and Al c. Form Al a appeared to be composed of monomeric species such as Al(H20)6+3, Al(OH)(H20)5+2, Al(OH)2(H20)4 +I and Al(OH)4-. Form Al b was polynuclear material containing perhaps 20-400 aluminum atoms per structure. It appeared to be a metastable material. Form Al c was composed of relatively large, microcrystalline, clearly solid AI(OH)3 particles. For each OH :Al ratio, the concentration of Al a remained constant with aging time, Al b decreased, and Al c increased. It appeared that Al b particles were increasing in size and ultimately were converted to Al c particles. After a few weeks' aging, Al c particles had the structure of gibbsite. In all solutions, equilibrium was only very slowly achieved, and the time required depended on the OH:Al ratio and how rapidly the solution was initially prepared (mixing time). Lower ratios caused a slower approach to equilibrium; sometimes equilibrium was not achieved even after several years' aging. The more slowly base was initially added (to obtain the proper OH:Al ratio), the more slowly was equilibrium approached. Ultimate equilibrium values of dissolved aluminum concentration and pH were consistent with known thermodynamic data on monomeric aluminum species. From data determined during the aging

  7. Nanogel formation from dilute solutions of clickable elastin-like recombinamers and its dependence on temperature: two fractal gelation modes.

    PubMed

    González de Torre, Israel; Quintanilla, Luis; Pinedo-Martín, Guillermo; Alonso, Matilde; Rodríguez-Cabello, José Carlos

    2014-08-27

    Diluted, complementary, click-reactive elastin-like recombinamer (ELR) solutions have been prepared and mixed at two different temperatures, one below and one above the characteristic transition temperature (Tt) of these chemically modified ELRs. FTIR measurements, size, aspect ratio, zeta potential, and microrheological measurements have been carried out on the nanostructures formed under these dilute conditions as a way to better understand the relationship between the final macroscopic properties of ELR-based hydrogels and the molecular conditions governing the initial stages of the chemical cross-linking process that occurs, especially its dependence on the preparation temperature relative to Tt. As a result, two different fractal modes of gel formation have been found at the two temperatures studied (above and below Tt). Thus, when the reaction mixture is prepared below Tt, essentially one-dimensional linear nanogels with a high aspect ratio are obtained. In contrast, 3D nanogels are formed above Tt, with spherical shapes predominating. These different structures seem to reflect the two molecular organizations of the single components of the mixture under these conditions, namely extended chains below Tt and a spherical arrangement above Tt. In addition to the interest in these nanogels as models for understanding the formation of microscopic structures and differential macroscopic properties under more conventional hydrogel-formation conditions, these nanogels are of interest because of their thermoresponsiveness and biocompatibility, which provide them with potential uses for drug delivery and other biomedical applications in living systems.

  8. Characterization of Laboratory Prepared Concrete Pastes Exposed to High Alkaline and High Sodium Salt Solutions

    SciTech Connect

    Langton, C. A.

    2016-06-30

    The objective of this study was to identify potential chemical degradation mechanisms for the Saltstone Disposal Unit (SDU) concretes, which over the performance life of the structures may be exposed to highly alkaline sodium salt solutions containing sulfate, hydroxide, and other potentially corrosive chemicals in salt solution and saltstone flush water, drain water, leachate and / or pore solution. The samples analyzed in this study were cement pastes prepared in the SIMCO Technologies, Inc. concrete laboratory. They were based on the paste fractions of the concretes used to construct the Saltstone Disposal Units (SDUs). SDU 1 and 4 concrete pastes were represented by the PV1 test specimens. The paste in the SDU 2, 3, 5, and 6 concrete was represented by the PV2 test specimens. SIMCO Technologies, Inc. selected the chemicals and proportions in the aggressive solutions to approximate proportions in the saltstone pore solution [2, 3, 5, and 6]. These test specimens were cured for 56 days in curing chamber before being immersed in aggressive solutions. After exposure, the samples were frozen to prevent additional chemical transport and reaction. Selected archived (retrieved from the freezer) samples were sent to the Savannah River National Laboratory (SRNL) for additional characterization using x-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive x-ray (EDX) spectroscopy. Characterization results are summarized in this report. In addition, a correlation between the oxide composition of the pastes and their chemical durability in the alkaline salt solutions is provided.

  9. Bioelectrochemical recovery of Cu, Pb, Cd, and Zn from dilute solutions.

    PubMed

    Modin, Oskar; Wang, Xiaofei; Wu, Xue; Rauch, Sebastien; Fedje, Karin Karlfeldt

    2012-10-15

    In a microbial bioelectrochemical system (BES) living microorganisms catalyze the anodic oxidation of organic matter at a low anode potential. We used a BES with a biological anode to power the cathodic recovery of Cu, Pb, Cd, and Zn from a simulated municipal solid waste incineration ash leachate. By varying the control of the BES, the four metals could sequentially be recovered from a mixed solution by reduction on a titanium cathode. First, the cell voltage was controlled at zero, which allowed recovery of Cu from the solution without an electrical energy input. Second, the cathode potential was controlled at -0.51 V to recover Pb, which required an applied voltage of about 0.34 V. Third, the cathode potential was controlled at -0.66 V to recover Cd, which required an applied voltage of 0.51 V. Finally, Zn was the only metal remaining in solution and was recovered by controlling the anode at +0.2V to maximize the generated current. The study is the first to demonstrate that a BES can be used for cathodic recovery of metals from a mixed solution, which potentially could be used not only for ash leachates but also for e.g. metallurgical wastewaters and landfill leachates.

  10. Thermodynamics of extraction by solutions of amines and salts of substituted ammonium bases

    NASA Astrophysics Data System (ADS)

    Ochkin, A. V.; Sergievskii, V. V.

    1989-09-01

    Extraction systems containing amines and their salts are widely used to concentrate and separate metals. From the theoretical viewpoint, these systems are among the most complex, because of the variety of intermolecular interactions in the organic phase. The explanation and quantitative description of the observed regularities of extraction became possible only as a result of progress in the study of the thermodynamics of binary and multicomponent solutions of salts of substituted ammonium bases in non-polar organic solvents, which make it possible to distinguish the contribution of each type of interaction to the non-ideal character of the solutions. All known "anomalous" features are due to the influence of the hydration of the salts of the substituted ammonium bases on their activity. The bibliography contains 113 references.

  11. A picture of dilute solution behavior of polymers through polyelectrolyte simulation

    NASA Astrophysics Data System (ADS)

    Yamakawa, Hiromi; Yoshizaki, Takenao; Ida, Daichi

    2013-11-01

    A Monte Carlo (MC) study is made of the persistence length q and the binary cluster integral β (or the excluded-volume strength B) for polyelectrolytes by the use of the discrete Kratky-Porod wormlike chain with hard-core-effective Debye-Hückel electrostatic pair potentials. The quantity q is determined from the initial decay rate of the bond correlation function after preliminary confirmation of the validity of this procedure using the chain with Lennard-Jones pair potentials. The quantity B is determined from the mean-square radius of gyration along with q by the use of the quasi-two-parameter (QTP) excluded-volume theory. They are evaluated for two model cases of polyelectrolytes, sodium hyaluronate as an example of semiflexible polymers and poly(sodium 4-styrenesulfonate) as a typical example of flexible polymers, both in aqueous sodium chloride. The behavior of MC data so obtained for q and B as functions of added salt concentration c is examined in detail, comparing them with the Odijk-Skolnick-Fixman theory of q and the Fixman-Skolnick (FS) theory of B and also with literature experimental data. In particular, the MC values of B are in almost complete agreement with the FS theory for large c, although the latter still overestimates B somewhat for small c. The values of B themselves and also the validity of the QTP theory in general are discussed in comparison with the case of nonionic polymers.

  12. A picture of dilute solution behavior of polymers through polyelectrolyte simulation.

    PubMed

    Yamakawa, Hiromi; Yoshizaki, Takenao; Ida, Daichi

    2013-11-28

    A Monte Carlo (MC) study is made of the persistence length q and the binary cluster integral β (or the excluded-volume strength B) for polyelectrolytes by the use of the discrete Kratky-Porod wormlike chain with hard-core-effective Debye-Hückel electrostatic pair potentials. The quantity q is determined from the initial decay rate of the bond correlation function after preliminary confirmation of the validity of this procedure using the chain with Lennard-Jones pair potentials. The quantity B is determined from the mean-square radius of gyration along with q by the use of the quasi-two-parameter (QTP) excluded-volume theory. They are evaluated for two model cases of polyelectrolytes, sodium hyaluronate as an example of semiflexible polymers and poly(sodium 4-styrenesulfonate) as a typical example of flexible polymers, both in aqueous sodium chloride. The behavior of MC data so obtained for q and B as functions of added salt concentration c is examined in detail, comparing them with the Odijk-Skolnick-Fixman theory of q and the Fixman-Skolnick (FS) theory of B and also with literature experimental data. In particular, the MC values of B are in almost complete agreement with the FS theory for large c, although the latter still overestimates B somewhat for small c. The values of B themselves and also the validity of the QTP theory in general are discussed in comparison with the case of nonionic polymers.

  13. Electrochemical Recovery of Sodium Hydroxide from Alkaline Salt Solution

    SciTech Connect

    Hobbs, D.T.; Edwards, T.B.

    1996-10-01

    A statistically designed set of tests determined the effects of current density, temperature, and the concentrations of nitrate/nitrite, hydroxide and aluminate on the recovery of sodium as sodium hydroxide (caustic) from solutions simulating those produced from the Savannah River Site (SRS) In-Tank Precipitation process. These tests included low nitrate and nitrite concentrations which would be produced by electrolytic nitrate/nitrite destruction. The tests used a two compartment electrochemical cell with a Nafion Type 324 ion-exchange membrane. Caustic was successfully recovered from the waste solutions. Evaluation of the testing results indicated that the transport of sodium across the membrane was not significantly affected by any of the varied parameters. The observed variance in the sodium flux is attributed to experimental errors and variations in the performance characteristics of individual pieces of the organic-based Nafion membrane.Additional testing is recommended to determine the maximum current density, to evaluate the chemical durability of the organic membrane as a function of current density and to compare the durability and performance characteristics of the organic-based Nafion membrane with that of other commercially available organic membranes and the inorganic class of membranes under development by Ceramatec and PNNL.

  14. Raman studies of solutions of single-wall carbon nanotube salts.

    PubMed

    Anglaret, E; Dragin, F; Pénicaud, A; Martel, R

    2006-03-09

    Polyelectrolyte solutions of Na-doped single-wall carbon nanotube (SWNT) salts are studied by Raman spectroscopy. Their Raman signature is first compared to undoped SWNT suspensions and dry alkali-doped SWNT powders, and the results indicate that the nanotube solutions consist of heavily doped (charged) SWNT. Raman signature of doping is then used to monitor in situ the oxidation reaction of the nanotube salt solutions upon exposure to air and to an acceptor molecule (benzoquinone). The results indicate a direct charge-transfer reaction from the acceptor molecule to the SWNT, leading to their gradual charge neutralization and eventual precipitation in solution. The results are consistent with a simple redox titration process occurring at the thermodynamical equilibrium.

  15. Theoretical study of the Pb(II)-catechol system in dilute aqueous solution: Complex structure and metal coordination sphere determination

    NASA Astrophysics Data System (ADS)

    Lapouge, Christine; Cornard, Jean-Paul

    2010-04-01

    We investigated the unknown interaction of Pb(II) with catechol ligand in diluted aqueous solution by electronic spectroscopies combined with quantum chemical calculations. The aim of this work is the determination of the complete structure of the complex formed and particularly the metal coordination sphere. Three successive steps have been necessary to reach this goal: (i) the comparison of the experimental electronic absorption spectrum with theoretical spectra calculated from various hypothetical structures, (ii) complexation reaction pathways calculations in vacuum and with taking into account the solvent effects and finally (iii) the fluorescence emission wavelength calculations. All these investigations led to identify a monodentate complex with the monodeprotonated ligand, in which the Pb atom presents a coordination number of five. The formula of the complex is [Pb(Hcat)(HO)4]mono+.

  16. Results of Analysis of Macrobatch 3 Decontaminated Salt Solution Coalescer from May 2010

    SciTech Connect

    Peters, T. B.; Fink, S. D.

    2012-12-18

    SRNL analyzed the Decontamination Salt Solution (DSS) coalescer from MCU by several analytical methods. This unit was removed from service in May 2010. The results of these analyses indicate that there is very little evidence of fouling via excessive solids, either from the leaching studies or X-Ray Diffraction (XRD) analysis.

  17. Oxygen isotope activities and concentrations in aqueous salt solutions at elevated temperatures: Consequences for isotope geochemistry

    USGS Publications Warehouse

    Truesdell, A.H.

    1974-01-01

    Studies of the effect of dissolved salts on the oxygen isotope activity ratio of water have been extended to 275??C. Dehydrated salts were added to water of known isotope composition and the solutions were equilibrated with CO2 which was sampled for analysis. For comparison similar studies were made using pure water. Results on water nearly coincide with earlier calculations. Salt effects diminish with increasing temperature only for solutions of MgCl2 and LiCl. Other salt solutions show complex behavior due to the temperature-dependent formation of ion pairs of changing character. Equilibrium fractionations (103 ln ??) between 1 molal solutions and pure water at 25, 100, and 275??C are: NaCl 0.0, -1.5, +1.0; KCl 0.0, -1.0, +2.0; LiCl -1.0, -0.6, -0.5; CaCl2 -0.4, -1.8, +0.8; MgCl2 -1.1, -0.7, -0.3; MgSO4 -1.1, +0.1, -; NaF (0.8 m) 0.0, -1.5, -0.3; and NH4Cl (0.55 m) 0.0, -1.2, -1.3. These effects are significant in the isotope study of hot saline fluids responsible for ore deposition and of fluids found in certain geothermal systems. Minor modification of published isotope geothermometers may be required. ?? 1974.

  18. [Stability of dilute solutions of ganciclovir sodium (Cymevan) in polypropylene syringes and PVC perfusion bags].

    PubMed

    Phaypradith, S; Vigneron, J; Perrin, A; Durney-Archeray, M J; Hoffman, M A; Hoffman, M

    1992-01-01

    The stability of ganciclovir sodium solutions stored in polypropylene syringes and PVC bags was tested in 0.9% sodium chloride at three concentrations 70, 200 and 350 mg/50 ml for polypropylene syringes, and two concentrations (70 and 350 mg/250 ml) for PVC bags and at three temperatures (-20 degrees C, + 4 degrees C, room temperature). The solutions, which had been initially frozen, were thawed by exposure to microwave radiations. The stability of each sample was determined by high-performance liquid chromatography. The results of this study indicate that admixtures of ganciclovir sodium at the concentration rates tested can be frozen for at least one year and are stable for at least 80 days at + 4 degrees C and 7 days at room temperature.

  19. The Interaction of Polycrystalline Copper Films with Dilute Aqueous Solutions of Cupric Chloride

    DTIC Science & Technology

    1989-10-01

    solution and the sample surface layer have been reported with no mention of the microstructure of the copper sample except for a few cases where chemical...in atmosphere has always been of interest because of the extensive use of copper and brass in buildings and statues, for example. A study by Pinnel et...dependent on the chlorine gas pressure. The copper microstructure was virtually ignored except for the mention of film thickness and crystal orientation

  20. Methods for predicting properties and tailoring salt solutions for industrial processes

    NASA Technical Reports Server (NTRS)

    Ally, Moonis R.

    1993-01-01

    An algorithm developed at Oak Ridge National Laboratory accurately and quickly predicts thermodynamic properties of concentrated aqueous salt solutions. This algorithm is much simpler and much faster than other modeling schemes and is unique because it can predict solution behavior at very high concentrations and under varying conditions. Typical industrial applications of this algorithm would be in manufacture of inorganic chemicals by crystallization, thermal storage, refrigeration and cooling, extraction of metals, emissions controls, etc.

  1. Methods for predicting properties and tailoring salt solutions for industrial processes

    SciTech Connect

    Ally, M.R.

    1992-01-01

    An algorithm developed at Oak Ridge National Laboratory accurately and quickly predicts thermodynamic properties of concentrated aqueous salt solutions. This algorithm is much simpler and much faster than other modeling schemes and is unique because it can predict solution behavior at very high concentrations and under varying conditions. Typical industrial applications of this algorithm would be in manufacture of inorganic chemicals by crystallization, thermal storage, refrigeration and cooling, extraction of metals, emissions control, etc. 3 figs, 2 tabs, 1 ref.

  2. Conversion of borate-based glass scaffold to hydroxyapatite in a dilute phosphate solution.

    PubMed

    Liu, Xin; Pan, Haobo; Fu, Hailuo; Fu, Qiang; Rahaman, Mohamed N; Huang, Wenhai

    2010-02-01

    Porous scaffolds of a borate-based glass (composition in mol%: 6Na2O, 8K2O, 8MgO, 22CaO, 36B2O3, 18SiO2, 2P2O5), with interconnected porosity of approximately 70% and pores of size 200-500 microm, were prepared by a polymer foam replication technique. The degradation of the scaffolds and conversion to a hydroxyapatite-type material in a 0.02 M K2HPO4 solution (starting pH = 7.0) at 37 degrees C were studied by measuring the weight loss of the scaffolds, as well as the pH and the boron concentration of the solution. X-ray diffraction, scanning electronic microscopy and energy dispersive x-ray analysis showed that a hydroxyapatite-type material was formed on the glass surface within 7 days of immersion in the phosphate solution. Cellular response to the scaffolds was assessed using murine MLO-A5 cells, an osteogenic cell line. Scanning electron microscopy showed that the scaffolds supported cell attachment and proliferation during the 6 day incubation. The results indicate that this borate-based glass could provide a promising degradable scaffold material for bone tissue engineering applications.

  3. Recovery of propylene glycol from dilute aqueous solutions via reversible reaction with aldehydes

    SciTech Connect

    Broekhuis, R.R.; Lynn, S.; King, C.J. |

    1993-12-01

    A means is proposed for separating propylene glycol and other compounds bearing multiple hydroxyl groups by reversible chemical reaction. Glycols react with aldehydes in cyclic acetalization reactions to form substituted dioxolanes. Propylene glycol reacts with formaldehyde and acetaldehyde to form 4-methyl-1,3-dioxolane and 2,4-dimethyl-1,3-dioxolane. The reaction is catalyzed homogeneously by strong mineral acids or heterogeneously by cation exchange resins in the acid form. Separation processes utilizing this reaction would include an acetalization step, several distillative separation steps and finally a hydrolysis step in which the reaction is reversed. Both reaction steps must be forced to completion by removing the reaction product simultaneously. The equilibrium and kinetics of the reaction with formaldehyde were studied experimentally in systems catalyzed by Amberlite IR-120 ion exchange resin. A number of solvents were screened for their ability to extract 2,4-dimethyl-1,3-dioxolane from aqueous solution. Aromatic hydrocarbons exhibited the highest distribution into the organic phase. To achieve an effective separation of propylene glycol from aqueous solution by combined reaction with formaldehyde and distillation, formaldehyde would have to be present in excess and would be difficult and costly to separate from the aqueous solution. In reactive distillation using acetaldehyde as a reactant this is not a problem. A large flow of acetaldehyde would be necessary to recover the propylene glycol sufficiently in a distillative process. In a process combining reaction and extraction into an organic solvent this problem is avoided. Process simulation indicates the energy input of such a process is less than half of the energy required in a triple-effect evaporation process. This benefit is offset by higher capital costs and increased complexity in the reaction/extraction process.

  4. Radiation induced modification of tryptophan and tyrosine residues in flavocytochrome b 2 in dilute aqueous solution

    NASA Astrophysics Data System (ADS)

    Bhattacharya, D.; Saha, A.; Mandal, P. C.

    2000-07-01

    Steady state gamma irradiation of an aqueous solution of flavocytochrome b 2 under different conditions led to modification of tryptophan and tyrosine residues. These aromatic amino acid residues were more susceptible to the attack by OH radicals than H atoms. Unchanged quantum yield values for tryptophan and tyrosine residues and unchanged tryptophan excited state lifetime in the irradiated enzyme suggests that irradiation results in breakage of some non-covalent bonds disrupting the peptide framework partially. It is justified by the circular dichroic studies for the irradiated enzyme which shows a reduced helicity but no evolution towards any other structures.

  5. Oligonucleotides as probes for studying polymerization reactions in dilute aqueous solution. 2: Polycondensations

    NASA Technical Reports Server (NTRS)

    Kolb, Vera; Orgel, Leslie E.

    1995-01-01

    We have prepared a (P-32)-labeled oligonucleotide probe carrying a ureido (-NH-CO-NH2) function at its 3'-terminus. This labeled oligomer was used to study polycondensations of urea and formaldehyde and of various phenols and formaldehyde in aqueous solution. The formation of formaldehyde copolymers attached to the amido-function of the probe was monitored by gel electrophoresis. Our results are generally in agreement with those obtained using conventional techniques. Our method is suitable for monitoring potentially prebiotic polycondensation reactions involving formaldehyde.

  6. Oligonucleotides as probes for studying polymerization reactions in dilute aqueous solution: II. Polycondensations

    NASA Technical Reports Server (NTRS)

    Kolb, V.; Orgel, L. E.

    1995-01-01

    We have prepared a [32P]-labeled oligonucleotide probe carrying a ureido (-NH-CO-NH2) function at its 3'-terminus. This labeled oligomer was used to study polycondensations of urea and formaldehyde and of various phenols and formaldehyde in aqueous solution. The formation of formaldehyde copolymers attached to the amido-function of the probe was monitored by gel electrophoresis. Our results are generally in agreement with those obtained using conventional techniques. Our method is suitable for monitoring potentially prebiotic polycondensation reactions involving formaldehyde.

  7. Oligonucleotides as probes for studying polymerization reactions in dilute aqueous solution: II. Polycondensations

    NASA Technical Reports Server (NTRS)

    Kolb, V.; Orgel, L. E.

    1995-01-01

    We have prepared a [32P]-labeled oligonucleotide probe carrying a ureido (-NH-CO-NH2) function at its 3'-terminus. This labeled oligomer was used to study polycondensations of urea and formaldehyde and of various phenols and formaldehyde in aqueous solution. The formation of formaldehyde copolymers attached to the amido-function of the probe was monitored by gel electrophoresis. Our results are generally in agreement with those obtained using conventional techniques. Our method is suitable for monitoring potentially prebiotic polycondensation reactions involving formaldehyde.

  8. Thermodynamic characteristics of the heparin-leucine-CaCl2 system in a diluted physiological solution

    NASA Astrophysics Data System (ADS)

    Nikolaeva, L. S.; Belov, G. V.; Rulev, Yu. A.; Semenov, A. N.

    2013-03-01

    Chemical equilibria in aqueous solutions of high-molecular weight heparin (Na4hep) and leucine (HLeu) are calculated through the mathematical modeling of chemical equilibria based on representative experimental pH titration data. In addition, chemical equilibria in the CaCl2-Na4hep-HLeu-H2O-NaCl system in the presence of 0.154M NaCl background electrolyte at a temperature of 37°C in the range of 2.30 ≤ pH ≤ 10.50 and initial concentrations of basic components n × 10-3 M ( n ≤ 4).

  9. Explicit-water theory for the salt-specific effects and Hofmeister series in protein solutions

    PubMed Central

    Kalyuzhnyi, Yuriy V.; Vlachy, Vojko

    2016-01-01

    Effects of addition of salts on stability of aqueous protein solutions are studied theoretically and the results are compared with experimental data. In our approach, all the interacting species, proteins, ions, and water molecules, are accounted for explicitly. Water molecules are modeled as hard spheres with four off-center attractive square-well sites. These sites serve to bind either another water or to solvate the ions or protein charges. The ions are represented as charged hard spheres, and decorated by attractive sites to allow solvation. Spherical proteins simultaneously possess positive and negative groups, represented by charged hard spheres, attached to the surface of the protein. The attractive square-well sites, mimicking the protein–protein van der Waals interaction, are located on the surface of the protein. To obtain numerical results, we utilized the energy route of Wertheim’s associative mean spherical approximation. From measurable properties, we choose to calculate the second virial coefficient B2, which is closely related to the tendency of proteins to aggregate and eventually crystalize. Calculations are in agreement with experimental trends: (i) For low concentration of added salt, the alkali halide salts follow the inverse Hofmeister series. (ii) At higher concentration of added salt, the trend is reversed. (iii) When cations are varied, the salts follow the direct Hofmeister series. (iv) In contrast to the colloidal theories, our approach correctly predicts the non-monotonic behavior of B2 upon addition of salts. (v) With respect to anions, the theory predicts for the B2 values to follow different sequences below and above the iso-ionic point, as also confirmed experimentally. (vi) A semi-quantitative agreement between measured and calculated values for the second virial coefficient, as functions of pH of solution and added salt type and concentration, is obtained. PMID:27276970

  10. Explicit-water theory for the salt-specific effects and Hofmeister series in protein solutions

    NASA Astrophysics Data System (ADS)

    Kalyuzhnyi, Yuriy V.; Vlachy, Vojko

    2016-06-01

    Effects of addition of salts on stability of aqueous protein solutions are studied theoretically and the results are compared with experimental data. In our approach, all the interacting species, proteins, ions, and water molecules, are accounted for explicitly. Water molecules are modeled as hard spheres with four off-center attractive square-well sites. These sites serve to bind either another water or to solvate the ions or protein charges. The ions are represented as charged hard spheres, and decorated by attractive sites to allow solvation. Spherical proteins simultaneously possess positive and negative groups, represented by charged hard spheres, attached to the surface of the protein. The attractive square-well sites, mimicking the protein-protein van der Waals interaction, are located on the surface of the protein. To obtain numerical results, we utilized the energy route of Wertheim's associative mean spherical approximation. From measurable properties, we choose to calculate the second virial coefficient B2, which is closely related to the tendency of proteins to aggregate and eventually crystalize. Calculations are in agreement with experimental trends: (i) For low concentration of added salt, the alkali halide salts follow the inverse Hofmeister series. (ii) At higher concentration of added salt, the trend is reversed. (iii) When cations are varied, the salts follow the direct Hofmeister series. (iv) In contrast to the colloidal theories, our approach correctly predicts the non-monotonic behavior of B2 upon addition of salts. (v) With respect to anions, the theory predicts for the B2 values to follow different sequences below and above the iso-ionic point, as also confirmed experimentally. (vi) A semi-quantitative agreement between measured and calculated values for the second virial coefficient, as functions of pH of solution and added salt type and concentration, is obtained.

  11. Hydration structure of salt solutions from ab initio molecular dynamics

    SciTech Connect

    Bankura, Arindam; Carnevale, Vincenzo; Klein, Michael L.

    2013-01-07

    The solvation structures of Na{sup +}, K{sup +}, and Cl{sup -} ions in aqueous solution have been investigated using density functional theory (DFT) based Car-Parrinello (CP) molecular dynamics (MD) simulations. CPMD trajectories were collected for systems containing three NaCl or KCl ion pairs solvated by 122 water molecules using three different but commonly employed density functionals (BLYP, HCTH, and PBE) with electron correlation treated at the level of the generalized gradient approximation (GGA). The effect of including dispersion forces was analyzed through the use of an empirical correction to the DFT-GGA scheme. Special attention was paid to the hydration characteristics, especially the structural properties of the first solvation shell of the ions, which was investigated through ion-water radial distribution functions, coordination numbers, and angular distribution functions. There are significant differences between the present results obtained from CPMD simulations and those provided by classical MD based on either the CHARMM force field or a polarizable model. Overall, the computed structural properties are in fair agreement with the available experimental results. In particular, the observed coordination numbers 5.0-5.5, 6.0-6.4, and 6.0-6.5 for Na{sup +}, K{sup +}, and Cl{sup -}, respectively, are consistent with X-ray and neutron scattering studies but differ somewhat from some of the many other recent computational studies of these important systems. Possible reasons for the differences are discussed.

  12. Hydration structure of salt solutions from ab initio molecular dynamics

    NASA Astrophysics Data System (ADS)

    Bankura, Arindam; Carnevale, Vincenzo; Klein, Michael L.

    2013-01-01

    The solvation structures of Na^+, K^+, and Cl^- ions in aqueous solution have been investigated using density functional theory (DFT) based Car-Parrinello (CP) molecular dynamics (MD) simulations. CPMD trajectories were collected for systems containing three NaCl or KCl ion pairs solvated by 122 water molecules using three different but commonly employed density functionals (BLYP, HCTH, and PBE) with electron correlation treated at the level of the generalized gradient approximation (GGA). The effect of including dispersion forces was analyzed through the use of an empirical correction to the DFT-GGA scheme. Special attention was paid to the hydration characteristics, especially the structural properties of the first solvation shell of the ions, which was investigated through ion-water radial distribution functions, coordination numbers, and angular distribution functions. There are significant differences between the present results obtained from CPMD simulations and those provided by classical MD based on either the CHARMM force field or a polarizable model. Overall, the computed structural properties are in fair agreement with the available experimental results. In particular, the observed coordination numbers 5.0-5.5, 6.0-6.4, and 6.0-6.5 for Na^+, K^+, and Cl^-, respectively, are consistent with X-ray and neutron scattering studies but differ somewhat from some of the many other recent computational studies of these important systems. Possible reasons for the differences are discussed.

  13. Hydration structure of salt solutions from ab initio molecular dynamics.

    PubMed

    Bankura, Arindam; Carnevale, Vincenzo; Klein, Michael L

    2013-01-07

    The solvation structures of Na(+), K(+), and Cl(-) ions in aqueous solution have been investigated using density functional theory (DFT) based Car-Parrinello (CP) molecular dynamics (MD) simulations. CPMD trajectories were collected for systems containing three NaCl or KCl ion pairs solvated by 122 water molecules using three different but commonly employed density functionals (BLYP, HCTH, and PBE) with electron correlation treated at the level of the generalized gradient approximation (GGA). The effect of including dispersion forces was analyzed through the use of an empirical correction to the DFT-GGA scheme. Special attention was paid to the hydration characteristics, especially the structural properties of the first solvation shell of the ions, which was investigated through ion-water radial distribution functions, coordination numbers, and angular distribution functions. There are significant differences between the present results obtained from CPMD simulations and those provided by classical MD based on either the CHARMM force field or a polarizable model. Overall, the computed structural properties are in fair agreement with the available experimental results. In particular, the observed coordination numbers 5.0-5.5, 6.0-6.4, and 6.0-6.5 for Na(+), K(+), and Cl(-), respectively, are consistent with X-ray and neutron scattering studies but differ somewhat from some of the many other recent computational studies of these important systems. Possible reasons for the differences are discussed.

  14. Electrodialysis for recovering salts from a urine solution containing micropollutants.

    PubMed

    Pronk, Wouter; Biebow, Martin; Boller, Markus

    2006-04-01

    Electrodialysis was investigated for the separation of micropollutants from nutrients in anthropogenic urine. In a continuously operated process, the nutrients were concentrated up to a factor of 3.2. The concentration factor was limited by water transport across the membrane. Water transport was caused by osmosis and electroosmosis, and a model was developed to describe these phenomena. The removal of several spiked micropollutants was investigated in continuous electrodialysis experiments. Ethinylestradiol was removed completely during the whole operating period. Diclofenac and carbamazepine were initially retained, but limited permeation (5-10%) occurred after longer operating times (90 days). Retentions of propranolol and ibuprofen were also high initially, but substantial breakthroughs occurred during extended operation. Considerable adsorption on the membranes was observed for all compounds. The permeation mechanism of several compounds appears to depend on the adsorbed amount on the membrane, which indicates that partitioning and diffusion mechanisms play an important role in the permeation transport. Partial desorption occurred in leaching experiments with polarity reversal, and almost quantitative desorption was observed after incubation of the membranes with Filter Count Gel Solution. Because environmental concentrations are much lower than the concentrations spiked here, it can be anticipated that operation without significant permeation is possible in practice during extended periods of time.

  15. Monte Carlo Simulations of the Dissolution of Borosilicate and Aluminoborosilicate Glasses in Dilute Aqueous Solutions

    SciTech Connect

    Kerisit, Sebastien N.; Pierce, Eric M.

    2011-09-15

    The aim of this study was to provide atomic-level insights into the dissolution behavior of borosilicate and aluminoborosilicate glasses to complement and help interpret previous experimental work on the NeB glass series studied by Pierce et al. [Pierce E. M., Reed L. R., Shaw W. J., McGrail B. P., Icenhower J. P., Windisch C. F., Cordova E. A. and Broady J. (2010) Experimental determination of the effect of the ratio of B/Al on glass dissolution along the nepheline (NaAlSiO4) - Malinkoite (NaBSiO4) join. Geochim. Cosmochim. Acta 74, 2634-2654]. The composition of these glasses was 50 mol% SiO2 - 25 mol% Na2O - (25-x) mol% Al2O3 - x mol% B2O3, with x varying from 0 to 20 mol%. In the first part of this work, the different structural features of these glasses (e.g., presence of non-bridging oxygens, partition of boron between trigonal and tetrahedral bonding environments, and formation of boroxol rings), identified in the study of Pierce et al., were implemented in the Monte Carlo program. Their effects on the dissolution of borosilicate and aluminosilicate glasses were then evaluated individually and led to the following conclusions. (1) The dependence of the dissolution rate on the amount of non-bridging oxygens was found to be linear at all Si/B ratios and the accelerating effect of non-bridging oxygens was shown to increase with increasing Si/B ratio. (2) The formation of boroxol rings and of clusters of boroxol rings resulted in an increase of the dissolution rate at all Si/B ratios and, again, the extent of the rate increase was strongly dependent on the Si/B ratio. (3) For aluminosilicate glasses, the implementation of the aluminum avoidance rule was found to increase the rate of dissolution relative to that obtained for a random distribution. In the second part of this work, Monte Carlo simulations were performed to model the dissolution of the NeB glasses in dilute conditions. One of the conclusions that emerged from the study of Pierce et al. was that

  16. Experimental and molecular dynamics studies of dysprosium(III) salt solutions for a better representation of the microscopic features used within the binding mean spherical approximation theory.

    PubMed

    Ruas, Alexandre; Guilbaud, Philippe; Den Auwer, Christophe; Moulin, Christophe; Simonin, Jean-Pierre; Turq, Pierre; Moisy, Philippe

    2006-10-19

    This work is aimed at a predictive description of the thermodynamic properties of actinide(III) salt solutions at high concentration and 25 degrees C. A new solution of the binding mean spherical approximation (BIMSA) theory, based on the Wertheim formalism, for taking into account 1:1 and also 1:2 complex formation, is used to reproduce, from a simple procedure, experimental osmotic coefficient variation with concentration for three binary salt solutions of the same lanthanide(III) cation: dysprosium(III) perchlorate, nitrate, and chloride. The relevance of the fitted parameters is discussed, and their values are compared with available literature values. UV-vis/near-IR, time-resolved laser-induced fluorescence spectroscopy experiments, and molecular dynamics (MD) calculations were conducted for dilute to concentrated solutions (ca. 3 mol.kg-1) for a study of the microscopic behavior of DyCl3 binary solutions. Coupling MD calculations and extended X-ray absorption fine structure led to the determination of reliable distances. The MD results were used for a discussion of the parameters used in the BIMSA.

  17. Selective on site separation and detection of molecules in diluted solutions with super-hydrophobic clusters of plasmonic nanoparticles

    NASA Astrophysics Data System (ADS)

    Gentile, Francesco; Coluccio, Maria Laura; Zaccaria, Remo Proietti; Francardi, Marco; Cojoc, Gheorghe; Perozziello, Gerardo; Raimondo, Raffaella; Candeloro, Patrizio; di Fabrizio, Enzo

    2014-06-01

    Super-hydrophobic surfaces are bio-inspired interfaces with a superficial texture that, in its most common evolution, is formed by a periodic lattice of silicon micro-pillars. Similar surfaces reveal superior properties compared to conventional flat surfaces, including very low friction coefficients. In this work, we modified meso-porous silicon micro-pillars to incorporate networks of metal nano-particles into the porous matrix. In doing so, we obtained a multifunctional-hierarchical system in which (i) at a larger micrometric scale, the super-hydrophobic pillars bring the molecules dissolved in an ultralow-concentration droplet to the active sites of the device, (ii) at an intermediate meso-scale, the meso-porous silicon film adsorbs the low molecular weight content of the solution and, (iii) at a smaller nanometric scale, the aggregates of silver nano-particles would measure the target molecules with unprecedented sensitivity. In the results, we demonstrated how this scheme can be utilized to isolate and detect small molecules in a diluted solution in very low abundance ranges. The presented platform, coupled to Raman or other spectroscopy techniques, is a realistic candidate for the protein expression profiling of biological fluids.Super-hydrophobic surfaces are bio-inspired interfaces with a superficial texture that, in its most common evolution, is formed by a periodic lattice of silicon micro-pillars. Similar surfaces reveal superior properties compared to conventional flat surfaces, including very low friction coefficients. In this work, we modified meso-porous silicon micro-pillars to incorporate networks of metal nano-particles into the porous matrix. In doing so, we obtained a multifunctional-hierarchical system in which (i) at a larger micrometric scale, the super-hydrophobic pillars bring the molecules dissolved in an ultralow-concentration droplet to the active sites of the device, (ii) at an intermediate meso-scale, the meso-porous silicon film

  18. Volumetric Properties of Dilute Aqueous Solutions of 1- and 2-propanol to 50 MPa and 373.15 K

    NASA Astrophysics Data System (ADS)

    Seitz, J.; Bahramian, J.; Blackwell, R.; Inaki, T.; York, D.; Schulte, M. D.

    2014-12-01

    The need to accurately model and understand reactions among organic compounds and biomolecules in solution is necessary to develop realistic chemical models for the reactions leading to the emergence of life and metabolic processes of extremophiles under elevated temperature and pressure conditions. Unfortunately, the scarcity of experimentally determined volumetric (and other) properties for important compounds at high temperatures and pressures leads to uncertainty in the calculation of reaction properties. Experimentally determined volumetric properties of aqueous solutions at non-standard conditions provide direct tests of current estimation methods and aid in the refinement of these methods. The goal of our research is to provide a database of experimentally determined volumetric properties. In previous studies, we have examined important organic molecules and biomolecules such as adenosine, coenzyme M and D-ribose. In this study, we investigate the volumetric properties of the structural isomers 1- and 2-propanol. 1-propanol (n-propanol) is a primary alcohol (CH3CH2CH2OH) and 2-propanol (isopropanol) is the simplest example of a secondary alcohol (CH3CHOHCH3). These compounds differ slightly in structure depending on to which carbon atom the hydroxyl group is bonded and will provide a sensitive test of current estimation methods and lead to more accurate predictions of the properties of complex aqueous systems at elevated temperatures and pressures. We obtained the densities of aqueous solutions of the alchohols using an Anton Paar DMA HP vibrating tube densimeter. Pressure was measured (pressure transducer) to an accuracy of ±0.01% and temperature was measured (integrated platinum thermometer) with an accuracy of ±0.05 K. Experimental uncertainty of density measurements is less than ±0.0001 g·cm-3. The partial molar volumes at infinite dilution (V∞) for 1- and 2-propanol were calculated from the measured densities and are shown in the figure at 0

  19. Transport properties in dilute UN (X ) solid solutions (X =Xe ,Kr )

    NASA Astrophysics Data System (ADS)

    Claisse, Antoine; Schuler, Thomas; Lopes, Denise Adorno; Olsson, Pär

    2016-11-01

    Uranium nitride (UN) is a candidate fuel for current GEN III fission reactors, for which it is investigated as an accident-tolerant fuel, as well as for future GEN IV reactors. In this study, we investigate the kinetic properties of gas fission products (Xe and Kr) in UN. Binding and migration energies are obtained using density functional theory, with an added Hubbard correlation to model f electrons, and the occupation matrix control scheme to avoid metastable states. These energies are then used as input for the self-consistent mean field method which enables to determine transport coefficients for vacancy-mediated diffusion of Xe and Kr on the U sublattice. The magnetic ordering of the UN structure is explicitly taken into account, for both energetic and transport properties. Solute diffusivities are compared with experimental measurements and the effect of various parameters on the theoretical model is carefully investigated. We find that kinetic correlations are very strong in this system, and that despite atomic migration anisotropy, macroscopic solute diffusivities show limited anisotropy. Our model indicates that the discrepancy between experimental measurements probably results from different irradiation conditions, and hence different defect concentrations.

  20. Electrochemical Behavior of Nano-grained Pure Copper in Dilute Alkaline Solution with Chloride Ion Trace

    NASA Astrophysics Data System (ADS)

    Fattah-Alhosseini, Arash; Imantalab, Omid; Attarzadeh, Farid Reza

    2016-10-01

    Effect of nano-grained structure on the interface behavior of pure copper in 0.01M KOH solution with chloride ion trace is investigated by various electrochemical techniques. Nano-grained structure was achieved by accumulative roll bonding (ARB) technique. Before any electrochemical measurements, microstructure was evaluated by means of optical microscopy and transmission electron microscopy (TEM). TEM observations showed that nano-grains (with an average size of below 100 nm) appeared after eight passes of ARB. Polarization curves revealed that increasing chloride ion concentration leads to a decrease in the corrosion and pitting potentials of both annealed and nano-grained pure copper samples. Electrochemical impedance spectroscopy revealed that chloride ion trace lowers passive film resistance and charge-transfer resistance in both annealed and nano-grained samples. Mott-Schottky analysis showed that the surface films formed on annealed and nano-grained samples in KOH solution with and without NaCl addition are of p-type semiconducting behavior. Moreover, this analysis showed that the acceptor density increases by increasing chloride ion concentration.

  1. Hausmannite (Mn3O4) conversion to manganite (γ-MnOOH) in dilute oxalate solution

    USGS Publications Warehouse

    Lind, Carol J.

    1988-01-01

    Oxalic acid retards the alteration of Mn3O4 to γ-MnOOH during aging at pH 7.4 ?? 0.2 in well-aerated, abiotic suspensions that contain 4.4 ?? 10-3 M total Mn. In solutions of 1.25 ?? 10-3 M oxalate and greater, about 15% of the initial Mn3O4 altered to ??-MnOOH by day 10, and in solutions of 6.7 ?? 10-4 M oxalate, about 45% altered to ??-MnOOH by day 67. Although precipitation continued through day 365, the degree of conversion remained the same as at day 10 and day 67, respectively. In oxalate-free suspensions, the conversion was about 80% complete by day 67 and 100% by day 109. Oxalate complexed most of the dissolved divalent Mn, lowered the free Mn(II) and MnSO40 concentrations, but increased the total dissolved Mn. Steric hindrance of surface reactions by a suggested manganese oxalate layer on the Mn3O4 surface may explain the blockage of the oxidation cycle.

  2. A traditional Japanese-style salt field is a niche for haloarchaeal strains that can survive in 0.5% salt solution

    PubMed Central

    Fukushima, Tadamasa; Usami, Ron; Kamekura, Masahiro

    2007-01-01

    Background Most of the haloarchaeal strains have been isolated from hypersaline environments such as solar evaporation ponds, salt lakes, or salt deposits, and they, with some exceptions, lyse or lose viability in very low-salt concentrations. There are no salty environments suitable for the growth of haloarchaea in Japan. Although Natrialba asiatica and Haloarcula japonica were isolated many years ago, the question, "Are haloarchaea really thriving in natural environments of Japan?" has remained unanswered. Results Ten strains were isolated from a traditional Japanese-style salt field at Nie, Noto Peninsula, Japan by plating out the soil samples directly on agar plates containing 30% (w/v) salts and 0.5% yeast extract. They were most closely related to strains of three genera, Haladaptatus, Halococcus, and Halogeometricum. Survival rates in 3% and 0.5% SW (Salt Water, solutions containing salts in approximately the same proportions as found in seawater) solutions at 37°C differed considerably depending on the strains. Two strains belonging to Halogeometricum as well as the type strain Hgm. borinquense died and lysed immediately after suspension. Five strains that belonged to Halococcus and a strain that may be a member of Halogeometricum survived for 1–2 days in 0.5% SW solution. Two strains most closely related to Haladaptatus possessed extraordinary strong tolerance to low salt conditions. About 20 to 34% of the cells remained viable in 0.5% SW after 9 days incubation. Conclusion In this study we have demonstrated that haloarchaea are really thriving in the soil of Japanese-style salt field. The haloarchaeal cells, particularly the fragile strains are suggested to survive in the micropores of smaller size silt fraction, one of the components of soil. The inside of the silt particles is filled with concentrated salt solution and kept intact even upon suspension in rainwater. Possible origins of the haloarchaea isolated in this study are discussed. PMID

  3. Modeling Solute Thermokinetics in LiCI-KCI Molten Salt for Nuclear Waste Separation

    SciTech Connect

    Morgan, Dane; Eapen, Jacob

    2013-10-01

    Recovery of actinides is an integral part of a closed nuclear fuel cycle. Pyrometallurgical nuclear fuel recycling processes have been developed in the past for recovering actinides from spent metallic and nitride fuels. The process is essentially to dissolve the spent fuel in a molten salt and then extract just the actinides for reuse in a reactor. Extraction is typically done through electrorefining, which involves electrochemical reduction of the dissolved actinides and plating onto a cathode. Knowledge of a number of basic thermokinetic properties of salts and salt-fuel mixtures is necessary for optimizing present and developing new approaches for pyrometallurgical waste processing. The properties of salt-fuel mixtures are presently being studied, but there are so many solutes and varying concentrations that direct experimental investigation is prohibitively time consuming and expensive (particularly for radioactive elements like Pu). Therefore, there is a need to reduce the number of required experiments through modeling of salt and salt-fuel mixture properties. This project will develop first-principles-based molecular modeling and simulation approaches to predict fundamental thermokinetic properties of dissolved actinides and fission products in molten salts. The focus of the proposed work is on property changes with higher concentrations (up to 5 mol%) of dissolved fuel components, where there is still very limited experimental data. The properties predicted with the modeling will be density, which is used to assess the amount of dissolved material in the salt; diffusion coefficients, which can control rates of material transport during separation; and solute activity, which determines total solubility and reduction potentials used during electrorefining. The work will focus on La, Sr, and U, which are chosen to include the important distinct categories of lanthanides, alkali earths, and actinides, respectively. Studies will be performed using LiCl-KCl salt

  4. Salt-water-freshwater transient upconing - An implicit boundary-element solution

    USGS Publications Warehouse

    Kemblowski, M.

    1985-01-01

    The boundary-element method is used to solve the set of partial differential equations describing the flow of salt water and fresh water separated by a sharp interface in the vertical plane. In order to improve the accuracy and stability of the numerical solution, a new implicit scheme was developed for calculating the motion of the interface. The performance of this scheme was tested by means of numerical simulation. The numerical results are compared to experimental results for a salt-water upconing under a drain problem. ?? 1985.

  5. Precursor Luminescence near the Collapse of Laser-Induced Bubbles in Alkali-Salt Solutions

    PubMed Central

    Chu, Han-Ching; Vo, Sonny; Williams, Gary A.

    2014-01-01

    A precursor luminescence pulse consisting of atomic line emission is observed as much as 150 nanoseconds prior to the collapse point of laser-created bubbles in alkali-metal solutions. The timing of the emission from neutral Na, Li, and K atoms is strongly dependent on the salt concentration, which appears to result from resonant radiation trapping by the alkali atoms in the bubble. The alkali emission ends at the onset of the blackbody luminescence pulse at the bubble collapse point, and the duration of the blackbody pulse is found to be reduced by up to 30% as the alkali-salt concentration is increased. PMID:19519032

  6. Precise scanning calorimeter for studying thermal properties of biological macromolecules in dilute solution.

    PubMed

    Privalov, G; Kavina, V; Freire, E; Privalov, P L

    1995-11-20

    A precise scanning calorimeter for studying the heat capacity of liquids in a broad temperature range has been developed. By its design and capabilities this calorimeter is the first of a new generation for this type of instrument. This new scanning calorimeter operates differentially, is equipped with a pair of gold capillary cells and semiconductor sensors, and is able to scan up and down in temperature at user-selected rates. This instrument is completely operated by an integrated computer which also provides a full thermodynamic analysis of the results. Its construction does not involve the use of organic compounds, thus eliminating a source of baseline noise that has affected previous calorimeters. The operational temperature range of the instrument can be varied between 0 and 120 degrees C. The gold capillary cells (operational volume 0.8 ml) minimize temperature gradients in the heated/cooled liquid sample and permit easy washing and reloading without air bubbles. These features are crucial for the accuracy of difference heat capacity measurements and determination of the absolute value of the partial heat capacity of solute molecules. The measurements can be performed under an excess constant pressure (up to 3 atm) to prevent formation of gas bubbles and boiling of aqueous solutions above 100 degrees C. The noise level of the recorded heating/cooling power difference is below 50 x 10(-9) W (i.e., below 10 ncal/s) with a response half-time of 5 s. The reproducibility of the baseline without refilling the capillary cells is on the order of 0.5 x 10(-6) W. Reproducibility of the baseline upon refilling the cell is of the same order of magnitude. This provides an accuracy in difference heat capacity determination on the order of 10 mu cal/degrees Kml at a heating rate of 1 degree K/min.

  7. Structure-activity relationship for hydrophobic salts as viscosity-lowering excipients for concentrated solutions of monoclonal antibodies.

    PubMed

    Guo, Zheng; Chen, Alvin; Nassar, Roger A; Helk, Bernhard; Mueller, Claudia; Tang, Yu; Gupta, Kapil; Klibanov, Alexander M

    2012-11-01

    To discover, elucidate the structure-activity relationship (SAR), and explore the mechanism of action of excipients able to drastically lower the viscosities of concentrated aqueous solutions of humanized monoclonal antibodies (MAbs). Salts prepared from hydrophobic cations and anions were dissolved into humanized MAbs solutions. Viscosities of the resulting solutions were measured as a function of the nature and concentration of the salts and MAbs. Even at moderate concentrations, some of the salts prepared herein were found to reduce over 10-fold the viscosities of concentrated aqueous solutions of several MAbs at room temperature. To be potent viscosity-lowering excipients, the ionic constituents of the salts must be hydrophobic, bulky, and aliphatic. A mechanistic hypothesis explaining the observed salt effects on MAb solutions' viscosities was proposed and verified.

  8. Fourteen-year survival of Pseudomonas cepacia in a salts solution preserved with benzalkonium chloride.

    PubMed Central

    Geftic, S G; Heymann, H; Adair, F W

    1979-01-01

    A strain of Pseudomonas cepacia that survived for 14 years (1963 to 1977) as a contaminant in an inorganic salt solution which contained commercial 0.05% benzalkonium chloride (CBC) as an antimicrobial preservative, was compared to a recent clinical isolate of P. cepacia. Ammonium acetate was present in the concentrated stock CBC solution, and served as a carbon and nitrogen source for growth when carried over into the salts solution with the CBC. The isolate's resistance to pure benzalkonium chloride was increased step-wise to a concentration of 16%. Plate counts showed 4 x 10(3) colony-forming units per ml in the salts solution. Comparison of growth rates, mouse virulence, antibiotics resistance spectra, and substrate requirements disclosed no differences between the contaminant and a recently isolated clinical strain of P. cepacia. The results indicate that it is critical that pharmaceutical solutions containing benzalkonium chloride as an antimicrobial preservative be formulated without extraneous carbon and nitrogen sources or be preserved with additional antimicrobial agents. PMID:453827

  9. Effect of perfusion of bile salts solutions into the oesophagus of hiatal hernia patients and controls.

    PubMed Central

    Bachir, G S; Collis, J L

    1976-01-01

    Tests of the response to perfusion of the oesophagus were made in 54 patients divided into three groups. Group I consisted of patients with symptomatic hiatal hernia, group II hiatal hernia patients with peptic stricture, and group III normal individuals. Each individual oesophagus was perfused at a rate of 45-65 drops per minute over 25 minutes with six solutions: normal saline, N/10 HCl, taurine conjugates of bile salts in normal saline, taurine conjugates of bile salts in N/10 HCl, glycine conjugates of bile salts in normal saline, and taurine and glycine conjugates in a ratio of 1 to 2 in normal saline. It was found that acidified taurine solutions were more irritating than acid alone. With a 2mM/l solution of taurine in acid, symptoms are produced even in controls. With a 1 mM/l solution of the same conjugates, the majority of normal people feel slight heartburn or nothing, and therefore perfusion into the oesophagus of such a solution could be used as a test for oesophagitis. PMID:941112

  10. Solution-derived sodalite made with Si- and Ge-ethoxide precursors for immobilizing electrorefiner salt

    NASA Astrophysics Data System (ADS)

    Riley, Brian J.; Lepry, William C.; Crum, Jarrod V.

    2016-01-01

    Chlorosodalite has the general form of Na8(AlSiO4)6Cl2 and this paper describes experiments conducted to synthesize sodalite with a solution-based approach to immobilize a simulated spent electrorefiner salt solution containing a mixture of alkali, alkaline earth, and lanthanide chlorides. The reactants used were the salt solution, NaAlO2, and either Si(OC2H5)4 or Ge(OC2H5)4. Additionally, seven different glass sintering aids (at loadings of 5 mass%) were evaluated as sintering aids for consolidating the as-made powders using a cold-press-and-sinter technique. This process of using alkoxide additives for the Group IV component can be used to produce large quantities of sodalite at near-room temperature as compared to a method where colloidal silica was used as the silica source. However, the small particle sizes inhibited densification during heat treatments.

  11. Ethanol production with dilute acid hydrolysis using partially dried lignocellulosics

    DOEpatents

    Nguyen, Quang A.; Keller, Fred A.; Tucker, Melvin P.

    2003-12-09

    A process of converting lignocellulosic biomass to ethanol, comprising hydrolyzing lignocellulosic materials by subjecting dried lignocellulosic material in a reactor to a catalyst comprised of a dilute solution of a strong acid and a metal salt to lower the activation energy (i.e., the temperature) of cellulose hydrolysis and ultimately obtain higher sugar yields.

  12. Analysis of frozen salt solutions with laser-induced breakdown spectroscopy under Martian conditions

    NASA Astrophysics Data System (ADS)

    Schröder, S.; Pavlov, S. G.; Hübers, H.-W.; Rauschenbach, I.; Jessberger, E. K.

    2010-05-01

    Laser-induced breakdown spectroscopy (LIBS) is a powerful analytical technique for determining the elemental composition of materials. It can be applied in-situ to geological surfaces on planetary missions. Since pure liquid water is unstable at the current surface conditions on Mars, i.e. low surface pressure and temperatures ranging from 140 K to 300 K, salt solutions or brines are of particular interest. It has been suggested that salts could stabilize liquid water on Mars lowering the freezing point of the solution and suppressing evaporation rates. The appropriate salts have been found on Mars in different locations. In this study LIBS is employed for the investigation of frozen sulphate and chloride solutions under Martian conditions in a dedicated simulation chamber. For the laboratory experiments, various salt solutions were prepared with different concentrations. To produce ice with only little inclusions of air, the samples were degassed before freezing them in a copper container. The measurements were performed at 240 K by cooling with liquid nitrogen and controlled heating. A constant flow of a Martian atmosphere-like gas mixture at a pressure of approximately 6 hPa was maintained through the chamber during the measurements. A Q-switched Nd:YAG laser operating at 1064nm and at 10 Hz was used to ablate material and to generate a plasma on the frozen sample's surface. The emitted light of the plasma was collected into the entrance slit of an echelle spectrometer (LTB Aryelle Butterfly) by a toroid mirror. A time-gated ICCD camera (Andor) at the exit of the spectrometer recorded the plasma emission signal. The laser beam was focused at a new position for each measurement. The delay time and the integration time of the spectrometer have been optimized to obtain good signal-to-noise ratios up to 150 while at the same time not losing signals from fast recombining ions. First, the spectra of several frozen salt solutions were investigated qualitatively

  13. Laser-induced breakdown spectroscopy for analysis of frozen salt solutions under Martian conditions

    NASA Astrophysics Data System (ADS)

    Schröder, Susanne; Pavlov, Sergey; Hübers, Heinz-Wilhelm; Rauschenbach, Isabelle; Jessberger, Elmar K.

    Laser-induced breakdown spectroscopy (LIBS) is a powerful analytical technique for determin-ing the elemental composition of materials. It can be applied in-situ to geological surfaces on planetary missions. Since pure liquid water is unstable at the current surface conditions on Mars, i.e. low surface pressure and temperatures ranging from 140 K to 300 K, salt solutions or brines are of particular interest. It has been suggested that salts could stabilize liquid water on Mars lowering the freezing point of the solution and suppressing evaporation rates. The ap-propriate salts have been found on Mars in different locations. In this study LIBS is employed for the investigation of frozen sulphate and chloride solutions under Martian conditions in a dedicated simulation chamber. For the laboratory experiments, various salt solutions were prepared with different concen-trations. To produce ice with only little inclusions of air, the samples were degassed before freezing them in a copper container. The measurements were performed at 240 K by cooling with liquid nitrogen and controlled heating. A constant flow of a Martian atmosphere-like gas mixture at a pressure of approximately 6 hPa was maintained through the chamber during the measurements. A Q-switched Nd:YAG laser operating at 1064nm and at 10 Hz was used to ablate material and to generate a plasma on the frozen sample's surface. The emitted light of the plasma was collected into the entrance slit of an echelle spectrometer (LTB Aryelle But-terfly) by a toroid mirror. A time-gated ICCD camera (Andor) at the exit of the spectrometer recorded the plasma emission signal. The laser beam was focused at a new position for each measurement. The delay time and the integration time of the spectrometer have been optimized to obtain good signal-to-noise ratios up to 150 while at the same time not losing signals from fast recombining ions. First, the spectra of several frozen salt solutions were investigated qualitatively

  14. Preliminary evaluation of solution-mining intrusion into a salt-dome repository

    SciTech Connect

    Not Available

    1981-06-01

    This report is the product of the work of an ONWI task force to evaluate inadvertant human intrusion into a salt dome repository by solution mining. It summarizes the work in the following areas: a general review of the levels of defense that could reduce both the likelihood and potential consequences of human intrusion into a salt dome repository; evaluation of a hypothetical intrusion scenario and its consequences; recommendation for further studies. The conclusions of this task force report can be summarized as follows: (1) it is not possible at present to establish with certainty that solution mining is credible as a human-intrusion event. The likelihood of such an intrusion will depend on the effectiveness of the preventive measures; (2) an example analysis based on the realistic approach is presented in this report; it concluded that the radiological consequences are strongly dependent upon the mode of radionuclide release from the waste form, time after emplacement, package design, impurities in the host salt, the amount of a repository intercepted, the solution mining cavity form, the length of time over which solution mining occurs, the proportion of contaminated salt source for human consumption compared to other sources, and the method of salt purification for culinary purposes; (3) worst case scenarios done by other studies suggest considerable potential for exposures to man while preliminary evaluations of more realistic cases suggest significantly reduced potential consequences. Mathematical model applications to process systems, guided by more advanced assumptions about human intrusion into geomedia, will shed more light on the potential for concerns and the degree to which mitigative measures will be required.

  15. Transferable ionic parameters for first-principles Poisson-Boltzmann solvation calculations: Neutral solutes in aqueous monovalent salt solutions

    NASA Astrophysics Data System (ADS)

    Ringe, Stefan; Oberhofer, Harald; Reuter, Karsten

    2017-04-01

    Implicit solvation calculations based on a Stern-layer corrected size-modified Poisson-Boltzmann (SMPB) model are an effective approach to capture electrolytic effects in first-principles electronic structure calculations. For a given salt solution, they require a range of ion-specific parameters, which describe the size of the dissolved ions as well as thickness and shape of the Stern layer. Out of this defined parameter space, we show that the Stern layer thickness expressed in terms of the solute's electron density and the resulting ionic cavity volume completely determine ion effects on the stability of neutral solutes. Using the efficient SMPB functionality of the full-potential density-functional theory package FHI-aims, we derive optimized such Stern layer parameters for neutral solutes in various aqueous monovalent electrolytes. The parametrization protocol relies on fitting to reference Setschenow coefficients that describe solvation free energy changes with ionic strength at low to medium concentrations. The availability of such data for NaCl solutions yields a highly predictive SMPB model that allows to recover the measured Setschenow coefficients with an accuracy that is comparable to prevalent quantitative regression models. Correspondingly derived SMPB parameters for other salts suffer from a much scarcer experimental data base but lead to Stern layer properties that follow a physically reasonable trend with ionic hydration numbers.

  16. Adsorption of N-alkylpyridinium chlorides from water and salt solutions on cellulose acetate ultrafiltration membranes

    SciTech Connect

    Klimenko, N.A.; Yaroshenko, N.A.; Kondratova, T.B.

    1988-09-01

    A study has been made of the adsorption of three homologues in the N-alkylpyridinium chloride series from water and salt solutions, over a wide range of concentrations, on cellulose acetate ultrafiltration membranes, Grades UAM-500 and UAM-150. When adsorption takes place from true solutions, the membrane surface is hydrophobized. In the region of micellar solutions, nonassociated molecules and micelles are adsorbed in the mesopores and supermicropores, forming a mosaic adsorption layer. The thickness of the modifying layer depends on the length of the hydrophobic radical and on the composition of the system.

  17. Effect of added polymer in free jets of a dilute polymer solution

    NASA Astrophysics Data System (ADS)

    Renoult, Marie-Charlotte; Charpentier, Jean-Baptiste; Crumeyrolle, Olivier; Mutabazi, Innocent

    2016-11-01

    The instability of a free viscoelastic jet is experimentally investigated by extruding an aqueous solution containing five parts per million of Poly(ethylene oxide) into air from a sixty micrometers orifice at relative low speeds. A method of image analysis was developed to quantify the effect of the added polymer on the morphology and the stability of the jet breakup. Three main representations were considered: the area versus perimeter relation for all liquid objects detected on the images, i.e. jets and jet fragments, the equivalent diameter distribution of jet fragments and the standard deviation curve of jets profiles. The former two provide information on the morphology of jet fragments: distinction of two classes, products and residues, and existence of coalescence. The latter gives information on the jet breakup stability: measurement of the growth rate and initial amplitude of the jet instability and detection of beads-on-a-string structures in the jet interface deformation. Experimental results will be presented and compared to theory.

  18. [Functional analysis of diluted solutions of human hemoglobin by using Oximeter-3000 WTW equipped with Trioxmatic-300 electrode].

    PubMed

    Ricco, G; David, O; Rabino-Massa, E

    1998-04-01

    The oxygen carrying capacity of dilute solutions of hemoglobin from normal human adults was examined, by using the above indicated Oximeter. The results show that, if the pO2s are compared with those drawn from the Oximeter-539 WTW (a simpler instrument) carrying the same oxygen electrode, there is a good correspondence between the data drawn from both the instruments. The advantage of the former is that pO2s are measure in mBr, whereas the latter measures the oxygen of the aqueous solutions in mg/l; then mg must be converted into Torr pO2. Since both instruments are usually employed in the oxygen measurement of waste waters of earth, another conclusion is that their sensitivity also allows the use in the bio-medical (and zoological) field. In fact, the data obtained agree with those of recent literature on the subject, which are mainly drawn from automated and sophisticated apparatuses specifically built at this purpose.

  19. The molecular properties of biochar carbon released in dilute acidic solution and its effects on maize seed germination.

    PubMed

    Sun, Jingling; Drosos, Marios; Mazzei, Pierluigi; Savy, Davide; Todisco, Daniele; Vinci, Giovanni; Pan, Genxing; Piccolo, Alessandro

    2017-01-15

    It is not yet clear whether the carbon released from biochar in the soil solution stimulates biological activities. Soluble fractions (AQU) from wheat and maize biochars, whose molecular content was thoroughly characterized by FTIR, (13)C and (1)H NMR, and high-resolution ESI-IT-TOF-MS, were separated in dilute acidic solution to simulate soil rhizospheric conditions and their effects evaluated on maize seeds germination activity. Elongation of maize-seeds coleoptile was significantly promoted by maize biochar AQU, whereas it was inhibited by wheat biochar AQU. Both AQU fractions contained relatively small heterocyclic nitrogen compounds, whose structures were accounted by their spectroscopic properties. Point-of-Zero-Charge (PZC) values and van Krevelen plots of identified masses of soluble components suggested that the dissolved carbon from maize biochar behaved as humic-like supramolecular material capable to adhere to seedlings and deliver bioactive molecules. These findings contribute to understand the biostimulation potential of biochars from crop biomasses when applied in agricultural production. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. "Structure-making" ability of Na+ in dilute aqueous solution: an ONIOM-XS MD simulation study.

    PubMed

    Sripa, Pattrawan; Tongraar, Anan; Kerdcharoen, Teerakiat

    2013-02-28

    An ONIOM-XS MD simulation has been performed to characterize the "structure-making" ability of Na(+) in dilute aqueous solution. The region of most interest, i.e., a sphere that includes Na(+) and its surrounding water molecules, was treated at the HF level of accuracy using LANL2DZ and DZP basis sets for the ion and waters, respectively, whereas the rest of the system was described by classical pair potentials. Detailed analyzes of the ONIOM-XS MD trajectories clearly show that Na(+) is able to order the structure of waters in its surroundings, forming two prevalent Na(+)(H(2)O)(5) and Na(+)(H(2)O)(6) species. Interestingly, it is observed that these 5-fold and 6-fold coordinated complexes can convert back and forth with some degrees of flexibility, leading to frequent rearrangements of the Na(+) hydrates as well as numerous attempts of inner-shell water molecules to interchange with waters in the outer region. Such a phenomenon clearly demonstrates the weak "structure-making" ability of Na(+) in aqueous solution.

  1. Nonmonotonic variation with salt concentration of the second virial coefficient in protein solutions.

    PubMed

    Allahyarov, E; Löwen, H; Hansen, J P; Louis, A A

    2003-05-01

    The osmotic virial coefficient B2 of globular protein solutions is calculated as a function of added salt concentration at fixed pH by computer simulations of the "primitive model." The salt and counterions as well as a discrete charge pattern on the protein surface are explicitly incorporated. For parameters roughly corresponding to lysozyme, we find that B2 first decreases with added salt concentration up to a threshold concentration, then increases to a maximum, and then decreases again upon further raising the ionic strength. Our studies demonstrate that the existence of a discrete charge pattern on the protein surface profoundly influences the effective interactions and that linear and nonlinear Poisson Boltzmann theories fail for large ionic strength. The observed nonmonotonicity of B2 is compared with experiments. Implications for protein crystallization are discussed.

  2. Self-association of caffeine in aqueous solution. Study of dilute solutions by normal and second derivative UV absorption spectroscopy.

    NASA Astrophysics Data System (ADS)

    Iza, N.; Gil, M.; Montero, J. L.; Morcillo, J.

    1988-05-01

    The concentration dependence of the spectral parameters of caffeine bands at ˜205 and 273 nm has been studied in aqueous solution by normal and second derivative spectroscopy. The concentration range was 5 x 10 -6 - 5 x 10 -3 M and thirty-five different concentrations were used. Discontinuities in parameter variation of these two bands at ˜7.5 x 10 -5, ˜2 x 10 -4, and ˜1 x 10 -3M were observed as concentration was increased. These "limiting" concentrations define three quite differenciated hyper- or hipochromic effects: the first one can be explained as caffeine-water molecule interaction and the second and third as dimer and (dimer + polymer) stacking, respectively. Apparent self-association constants using the isodesmic model have been obtained K= 160 M -1 (for the second hypochromic effect) and K= 13.6 M -1 (for the third hypochromic effect), for the 273 nm band. It is noteworthy that the three "limiting" concentrations coincide with changes in DNA-caffeine interaction modes (H. Lang , 1976) and biological activity (I.B. Syed , 1976).

  3. Disproportionation and polymerization of plutonium(IV) in dilute aqueous solutions

    SciTech Connect

    Newton, T.W.; Rundberg, V.L.

    1983-12-31

    The rates of polymerization and disproportionation of Pu(IV) have been studied using low concentrations: (1.7 - 10) x 10{sup -}M Pu, (0.8 - 12) x 10{sup -}M HCl and 0.0iM ionic strength. Osmium(II) complexes such as the tris-4,4`-2,2`-bipyridine complex were found to react rapidly with Pu(IV) but very slowly, if at all, with Pu(IV) polymer, Pu(III), or Pu(V). Thus, it is possible to determine unreacted Pu(IV) in the presence of rection products by using Os(II) complexes. Disproportionation reaction products, Pu(III) and Pu(V), were determined using their reactions with Ce(IV) sulfate. We find -d[Pu(IV)]/dt = k`[Pu(IV)]{sup 2} at constant pH. Log k` varies from about 4.25 at pH 3 to about 7.0 at pH 4.1 (units for k` are M{sup -1}min{sup -1}). The [H{sup +}] dependence varies from about -2 to -3 over the pH range studied. The measured rate is the sum of those for polymerization and disproportionation; the latter reaction amounts to about 75% of the total at pH 3 and 20% at pH 4. The second-order rate constants for disproportionation are very much larger than expected on the basis of extrapolation from 0.2 to 1.0M HC10{sub 4} solutions. The products of the reaction do not affect the rate, but U(VI), aged Pu(IV) polymer, and CO{sub 2} increase the rate.

  4. Recovery of propylene glycol from dilute aqueous solutions by reversible chemical complexation with organoboronates

    SciTech Connect

    Broekhuis, R.R.; Lynn, S.; King, C.J.

    1995-05-01

    Extractants consisting of an ion-pair of Aliquat 336 with phenylboronate or 3-nitrophenylboronate were prepared in various diluents (2-ethylhexanol, toluene, o-xylene or diisobutylketone). In batch experiments propyleneglycol (1,2-PD) was effectively extracted even at low concentrations. Heterogeneous complexation constants {beta}{sub 11} calculated at 25 C were 45-120 (mol/1){sup {minus}1} in 2-ethylhexanol, 34.8 (mol/l){sup {minus}1} in toluene, 37.6 (mol/l){sup {minus}1} in o-xylene and 14.4 (mol/l){sup {minus}1} in diisobutylketone. In 2-ethythexanol, there was no significant effect of extractant concentration on the complexation constant. Equilibrium water concentration in the extractants was 8-12 wt %, decreasing with 1,2-PD uptake. Nearly all extractant/diluent systems exhibited overloading (more than stoichiometric uptake of 1,2-PD). Evidence for aggregation of the ion-pair extractant in organic phase was found from water solubilization studies (molar solubilization ratios up to 10) and {sup 1}H NMR spectroscopy studies. Solubilization of 1,2-PD within hydrophilic aggregate interiors may explain the observed overloading. The complexation constant decreased with increasing temperature, but not enough to make back extraction after a temperature change attractive. Back extraction may be achieved after acidification with carbon dioxide to convert the organoboronate anion to the corresponding organoboronic acid. Up to 80% of the extracted 1,2-PD was backextracted in a batch extraction using C0{sub 2}. The extractant could then be regenerated by stripping carbon dioxide from solution at temperatures exceeding 110 C. However, at these temperatures the extractant appears to undergo a transformation in which color changes and extraction capacity is reduced to about 60% of original value.

  5. The influence of temperature, sucrose and lactose on dilute solution properties of basil (Ocimumbasilicum) seed gum.

    PubMed

    Mirabolhassani, Seyed Elias; Rafe, Ali; Razavi, Seyed M A

    2016-12-01

    Hydrocolloid interactions with solvent/cosolutes play a vital role in the resolution of their functional properties. Basil seed gum (BSG) is a plant-derived hydrocolloid which has been found many applications in food formulations as stabilizer, emulsifier, thickener and gelling agents. Sucrose and lactose are the most effective sugars in textural and sensorial properties of bakery and dairy products which adding them to solutions containing hydrocolloids can be helpful to approach a proper formula. In this paper, the effect of temperature (25-65°C), sucrose (10, 20, 30 and 40%) and lactose (5, 10 and 15%) were investigated through some molecular parameters of BSG. Results revealed high flexible chain (665.35), intrinsic viscosity (11.38 dl/g) and hydrogel content (73%) of BSG, which may be attributed to some extent by its high molecular weight (1.73×10(6)Da). The density and intrinsic viscosity of BSG were diminished by growing temperature from 25 to 55°C. Among five models, which were applied to estimate intrinsic viscosity, Higiro-2 was the most suitable model at varying temperatures and cosolutes concentrations. The sugars showed a significant effect on the molecular parameters of BSG such as swollen specific volume, shape function, hydration parameter, and coil dimensions. The sugars showed more impact on the [η] of BSG and its molecular parameters than that of temperature. However, lactose had a more prominent effect on the BSG dimensions than that of sucrose, which can be related to its molecular conformation and spatial orientation. It is feasible to make a proper formula by BSG and explain some phenomena in its applications in food and pharmaceutical systems.

  6. Multilayering of Surfactant Systems at the Air-Dilute Aqueous Solution Interface.

    PubMed

    Thomas, Robert K; Penfold, Jeffrey

    2015-07-14

    In the last 15 years there have been a number of observations of surfactants adsorbed at the air-water interface with structures more complicated than the expected single monolayer. These observations, mostly made by neutron or X-ray reflectivity, show structures varying from the usual monolayer to monolayer plus one or two additional bilayers to multilayer adsorption at the surface. These observations have been assembled in this article with a view to finding some common features between the very different systems and to relating them to aspects of the bulk solution phase behavior. It is argued that multilayering is primarily associated with wetting or prewetting of the air-water interface by phases in the bulk system, whose structures depend on an overall attractive force between the constituent units. Two such phases, whose formation is assumed to be partially driven by strong specific ion binding, are a concentrated lamellar phase that forms at low concentrations and a swollen lamellar phase that is not space-filling. Multilayering phenomena at the air-water interface then offer a delicate and easy means of studying the finer details of the incompletely understood attraction that leads to these two phases, as well as an interesting new means of self-assembling surface structures. In addition, multilayering is often associated with unusual wetting characteristics. Examples of systems discussed, and in some cases their bulk phase behavior, include surfactants with multivalent metal counterions, surfactants with oligomers and polymers, surfactant with hydrophobin, dichain surfactants, lung surfactant, and the unusual system of ethanolamine and stearic acid. Two situations where the air-water surface is deliberately held out of equilibrium are also assessed for features in common with the steady-state/equilibrium observations.

  7. Diluting ferric carboxymaltose in sodium chloride infusion solution (0.9% w/v) in polypropylene bottles and bags: effects on chemical stability

    PubMed Central

    Philipp, Erik; Braitsch, Michaela; Bichsel, Tobias; Mühlebach, Stefan

    2016-01-01

    Objectives This study was designed to assess the physicochemical stability of colloidal ferric carboxymaltose solution (Ferinject) when diluted and stored in polypropylene (PP) bottles and bags for infusion. Methods Two batches of ferric carboxymaltose solution (Ferinject) were diluted (500 mg, 200 mg and 100 mg iron in 100 mL saline) in PP bottles or bags under aseptic conditions. The diluted solutions were stored at 30°C and 75%±5% relative humidity (rH) for 72 h, and samples were withdrawn aseptically at preparation and after 24 h, 48 h and 72 h. Multiple parameters were used to test stability-related measures (pH, total iron and iron (II) content, molecular weight range determination, microbial contamination and particles count ≥10 μm). Results Overall, Ferinject diluted in 0.9% (w/v) NaCl solution and stored in PP bottles and bags was stable within the specifications for the complex and the acceptability limits set for all assays. In both containers, total iron content remained stable, within 10% of the theoretical iron content, and levels of iron (II) remained far below the threshold of acceptability. All preparations were free from sediments, particle numbers were acceptable and there was no microbial contamination. The molecular weight distribution and polydispersity index were also acceptable. Conclusions Under the tested experimental conditions, colloidal ferric carboxymaltose solution (Ferinject) diluted in saline in PP infusion bottles or bags demonstrated physical and chemical stability for up to 72 h at 30°C and 75% rH. Because of the lack of additional clinical data, when using ferric carboxymaltose, physicians/pharmacists should refer to the dilution and storing recommendations given in the product's summary of product characteristics. PMID:26835007

  8. Effects of ion exchange on stream solute fluxes in a basin receiving highway deicing salts

    USGS Publications Warehouse

    Shanley, J.B.

    1994-01-01

    At Fever Brook, a 1260-ha forested basin in central Massachusetts, highway deicing salt application increased the solute flux in streamflow by 120% above background flux (equivalent basis) during a 2-yr period. Attempts to isolate the nonsalt component of stream solute fluxes have commonly subtracted salt contributions based on the net Cl flux (Cl output in streamflow minus Cl input in precipitation). In these studies, any net Na flux in excess of the amount needed to balance the net Cl flux has been attributed to weathering. At Fever Brook, however, the net output of Na was less than the net output of Cl, suggesting a loss of Na within the basin. The Na sink was inferred to be cation exchange of Na for Ca and Mg in the soil. A method was developed to quantify the exchange based on a Na budget, which included an independent estimate of the Na flux from weathering. The amount of exchange was apportioned to Ca and Mg based on their relative concentrations in the stream. The background fluxes of Ca and Mg (i.e., those that would occur in the absence of deicing salts) were calculated by subtracting the amounts from ion exchange plus the much smaller direct contributions in deicing salts from the observed fluxes. Ion exchange and direct salt contributions increased the net output fluxes of Ca and Mg, each by 44% above background. In basins that receive deicing salts, failure to account for cation exchange thus may result in an underestimate of the flux of Na from weathering and overestimates of the fluxes of Ca and Mg from weathering.

  9. Molecular thermodynamics for swelling of a mesoscopic ionomer gel in 1 : 1 salt solutions.

    PubMed

    Victorov, A; Radke, C; Prausnitz, J

    2006-01-14

    For a microphase-separated diblock copolymer ionic gel swollen in salt solution, a molecular-thermodynamic model is based on the self-consistent field theory in the limit of strongly segregated copolymer subchains. The geometry of microdomains is described using the Milner generic wedge construction neglecting the packing frustration. A geometry-dependent generalized analytical solution for the linearized Poisson-Boltzmann equation is obtained. This generalized solution not only reduces to those known previously for planar, cylindrical and spherical geometries, but is also applicable to saddle-like structures. Thermodynamic functions are expressed analytically for gels of lamellar, bicontinuous, cylindrical and spherical morphologies. Molecules are characterized by chain composition, length, rigidity, degree of ionization, and by effective polymer-polymer and polymer-solvent interaction parameters. The model predicts equilibrium solvent uptakes and the equilibrium microdomain spacing for gels swollen in salt solutions. Results are given for details of the gel structure: distribution of mobile ions and polymer segments, and the electric potential across microdomains. Apart from effects obtained by coupling the classical Flory-Rehner theory with Donnan equilibria, viz. increased swelling with polyelectrolyte charge and shrinking of gel upon addition of salt, the model predicts the effects of microphase morphology on swelling.

  10. Influence of electro-activated solutions of weak organic acid salts on microbial quality and overall appearance of blueberries during storage.

    PubMed

    Liato, Viacheslav; Hammami, Riadh; Aïder, Mohammed

    2017-06-01

    The aim of this work was to study the potential of diluted electro-activated solutions of weak organic acid salts (potassium acetate, potassium citrate and calcium lactate) to extend the shelf life of blueberries during post-harvest storage. The sanitizing capacity of these solutions was studied against pathogenic bacteria Listeria monocytogenes and E. coli O157:H7 as well as phytopathogenic fungi A. alternata, F. oxysporum and B. cinerea. The results showed that a 5-min treatment of inoculated blueberries with electro-activated solutions resulted in a 4 log CFU/g reduction in Listeria monocytogenes for all solutions. For E. coli O157:H7, the electro-activated potassium acetate and potassium citrate solutions achieved a decrease of 3.5 log CFU/g after 5 min of berry washing. The most important fungus reduction was found when blueberries were washed with an electro-activated solution of potassium acetate and a NaOCl solution. After 5 min of blueberry washing with an electro-activated potassium acetate solution, a very high reduction effect was observed for A. alternata, F. oxysporum and B. cinerea, which showed survival levels of only 2.2 ± 0.16, 0.34 ± 0.15 and 0.21 ± 0.16 log CFU/g, respectively. Regarding the effect of the washing on the organoleptic quality of blueberries, the obtained results showed no negative effect on the product color or textural profile. Finally, this work suggests that washing with electro-activated solutions of weak organic acid salts can be used to enhance the shelf-life of blueberries during post-harvest storage.

  11. Intrinsic viscosity and conformational parameters of xanthan in aqueous solutions: salt addition effect.

    PubMed

    Brunchi, Cristina-Eliza; Morariu, Simona; Bercea, Maria

    2014-10-01

    The intrinsic viscosity and conformational parameters of xanthan in aqueous solutions were investigated at 25°C as a function of salt nature (NaCl and KCl) and concentration (up to 3×10(-1)mol/L). The viscometric parameters were evaluated by applying semi-empirical equations proposed by Rao and Wolf. The results show that the new model proposed by Wolf provides accurate intrinsic viscosity values comparable with those obtained by using traditional methods. The experimental data were modeled with Boltzmann sigmoidal equation. The stiffness parameter, hydrodynamic volume and viscometric expansion factor were determined and discussed. With increasing salt concentration, the hydrodynamic volume and the viscometric expansion factor decrease and the critical overlap concentration increases, reaching limiting values above a given salt concentration. The high Huggins constant values suggest the existence of aggregates for salt concentrations above 5×10(-2) and 3×10(-3)mol/L for NaCl and KCl, respectively. Stiffness parameter was determined by Smidsrød and Haug method as being 5.45×10(-3), indicating a rigid conformation for xanthan macromolecules in solution.

  12. Condensation of semiflexible polyelectrolytes in mixed solutions of mono- and multivalent salts

    NASA Astrophysics Data System (ADS)

    Plunk, Amelia A.; Luijten, Erik

    2013-03-01

    The salt-dependent condensation of highly charged polyelectrolytes in aqueous solution is a topic of great biological and industrial importance that has been widely studied over the past decades. It is well established that interaction with multivalent counterions leads to the formation of bundle-like aggregates for rigid polyelectrolytes and to collapsed structures or disordered aggregates for flexible polyelectrolytes. Here, we investigate the behavior of semiflexible chain molecules, where the electrostatically induced aggregation is impeded by the intrinsic bending stiffness of the polymer. Moreover, we study the competition between monovalent and multivalent counterions in mixed solutions and establish the threshold salt concentration required for condensation. Our findings are relevant for a range of biomedical problems, including the fabrication of nanoparticles for gene delivery and the packaging of DNA by histones. This work is supported by the National Science Foundation.

  13. Solution-derived sodalite made with Si- and Ge-ethoxide precursors for immobilizing electrorefiner salt

    SciTech Connect

    Riley, Brian J.; Lepry, William C.; Crum, Jarrod V.

    2016-01-01

    Chlorosodalite has the general form of Na8(AlSiO4)6Cl2 and this paper describes experiments conducted to synthesize sodalite to immobilize a mixed chloride salt using solution-based techniques. Sodalites were made using different Group IV contributions from either Si(OC2H5)4 or Ge(OC2H5)4, NaAlO2, and a simulated spent electrorefiner salt solution containing a mixture of alkali, alkaline earth, and lanthanide chlorides. Additionally, 6 glass binders at low loadings of 5 mass% were evaluated as sintering aids for the consolidation process. The approach of using the organic Group IV additives can be used to produce large quantities of sodalite at room temperature and shows promise over a method where colloidal silica is used as the silica source. However, the small particle sizes inhibited densification during pressure-less sintering.

  14. Characterization of Swollen States of Polyelectrolyte Brushes in Salt Solution by Neutron Reflectivity

    NASA Astrophysics Data System (ADS)

    Kobayashi, Motoyasu; Mitamura, Koji; Terada, Masami; Yamada, Norifumi L.; Takahara, Atsushi

    2011-01-01

    Cationic and zwitterionic polyelectrolyte brushes on quartz substrate were synthesized by surface-initiated atom transfer radical polymerization of 2-(methacryloyloxy)-ethyltrimethylammonium chloride (MTAC) and 2-(methacryloyloxy)ethyl phosphorylcholine (MPC). The effects of ionic strength on brush structure are investigated by neutron reflectivity (NR) in NaCl deuterium oxide (D2O) solutions. We observed that poly(MTAC) chains were drastically shrunk at concentrations above 0.1 M NaCl/D2O, which may be the change in charge-screening effect against ions on poly(MTAC). On the other hand, effect of salt concentration on a swollen state of poly(MPC) brush was negligible, even at the high concentration (5.0 M) close to saturation. The behaviour of poly(MPC) in salt aqueous solution is completely different from that of poly(MTAC), which may arise from the unique interaction properties, neutral nature, and hydrated water structure of phosphorylcholine units.

  15. Characterization of swollen structure of high-density polyelectrolyte brushes in salt solution by neutron reflectivity

    NASA Astrophysics Data System (ADS)

    Kobayashi, Motoyasu; Terayama, Yuki; Hino, Masahiro; Ishihara, Kazuhiko; Takahara, Atsushi

    2009-08-01

    Zwitterionic and cationic polyelectrolyte brushes on quartz substrate were prepared by surface-initiated atom transfer radical polymerization of 2-(methacryloyloxy)ethyl phosphorylcholine (MPC) and 2-(methacryloyloxy)ethyltrimethylammonium chloride (METAC), respectively. The effects of ionic strength on brush structure and surface properties of densely grafted polyelectrolyte brushes were analysed by neutron reflectivity (NR) measurements. NR at poly(METAC)/D2O and poly(MPC)/D2O interface revealed that the grafted polymer chains were fairly extended from the substrate surface, while the thickness reduction of poly(METAC) brush was observed in 5.6 M NaCl/D2O solution due to the screening of the repulsive interaction between polycations by hydrated salt ions. Interestingly, no structural change was observed in poly(MPC) brush even in a salt solution probably due to the unique interaction properties of phosphorylcholine units.

  16. Prediction of subsidence resulting from creep closure of solutioned-mined caverns in salt domes

    SciTech Connect

    Neal, J.T.

    1991-01-01

    The prediction of subsidence rates over a range of areal configurations of solution-mined caverns in salt domes is possible, based on some fifty years of history in solution mining. Several approaches contribute to predictions: site-specific observations obtained from subsidence monitoring; numerical modeling, now becoming more practicable and credible; salt-creep data from testing; and rule-of-thumb methods, based on experience. All of these approaches contribute to understanding subsidence but none are totally reliable alone. The example of subsidence occurring at the Strategic Petroleum Reserve sites demonstrates several principles of cavern creep closure, the main cause of the subsidence, and shows that reliable projections of future subsidence are possible. 13 refs., 6 figs.

  17. External application of hypertonic salt solution for treatment of posttraumatic oedema.

    PubMed

    Atalar, Hakan; Yavuz, Osman Y; Uras, Ismail; Selek, Hakan; Erakar, Aziz; Sayli, Ugur

    2005-08-01

    In 20 New Zealand rabbits (two groups of 10 rabbits each), hind limb circumference and anterior compartment pressure were measured following ketamin anaesthesia (time zero). During the same anaesthesia, closed transverse proximal tibial shaft fractures were created in both groups. Twenty-four hours after the fractures, during a second anaesthesia, limb circumference and compartment pressure were measured as before, and fractured limbs were fixed to the rabbits' bodies. At the same time, treatment was started: one group received external application of saturated salt solution and the other group received intermittent ice application. During 48 hours of treatment (from 24 to 72 hours) in the saturated salt solution group, the mean limb circumference decreased from 125.70 +/- 9.93 mm to 115.70 +/- 8.78 mm (p = 0.005) and the mean compartment pressure decreased from 18.30 +/- 1.70 mmHg to 12.40 +/- 1.77 mmHg (p = 0.005). In the control group, the mean limb circumference decreased from 127.85 +/- 7.47 mm to 122.00 +/- 6.83 mm (not significant) and the mean compartment pressure decreased from 19.57 +/- 1.27 mmHg to 17.85 +/- 2.67 mmHg (not significant). In short, differences in compartment pressure and limb circumference before and after treatment were statistically significant in the saturated salt solution group (p = 0.005) but not in the control group.

  18. Investigation of the salting out of methane from aqueous electrolyte solutions using computer simulations.

    PubMed

    Docherty, H; Galindo, A; Sanz, E; Vega, C

    2007-08-02

    We calculate the excess chemical potential of methane in aqueous electrolyte solutions of NaCl using Monte Carlo computer simulations. In a recent work [Docherty et al. J. Chem. Phys. 2006, 125, 074510], we presented a new potential model for methane in water which is capable of describing accurately the excess chemical potential of methane in pure water over a range of temperatures, a quantity that can be related to the solubility and which is commonly used to study the hydrophobic effect. Here, we use the same potential model for the water-methane interactions and investigate the effect of added salt on the chemical potential of methane in the solution. The methane molecules are modeled as single Lennard-Jones (LJ) interaction sites, and the water molecules are modeled with the TIP4P/2005 model. A correcting factor of chi = 1.07 for the energetic Berthelot (geometric) combining rule of the methane-water interaction is also used, which mimics the polarization of methane in water. We consider NaCl as the salt and treat the ions with the Smith and Dang model (i.e., as charged LJ interaction sites). Ion-water, ion-ion, and ion-methane interactions are treated using Lorentz-Berthelot combining rules. In addition, the Coulombic potential is used to model charge-charge interactions which are calculated using the Ewald sum. We have carried out isobaric-isothermal (NpT) simulations to determine the equilibrium densities of the solutions. The simulation data is in excellent agreement with experimental densities of aqueous NaCl solutions of different concentration. Hydration numbers are also obtained and found to be in agreement with reported data. Canonical (NVT) simulations at the averaged densities are then performed using the Widom test-particle insertion method to obtain the excess chemical potential of methane in the saline solutions. An increase in the chemical potential of methane, corresponding to a salting out effect, is observed when salt is added to the solution

  19. Precision and accuracy of TearLab osmometer in measuring osmolarity of salt solutions.

    PubMed

    Yoon, Dan; Gadaria-Rathod, Neha; Oh, Cheongeun; Asbell, Penny A

    2014-12-01

    The purpose of this study was to examine the inherent precision and accuracy of TearLab Osmolarity System using salt solutions, including solutions of very high osmolarity (>360 mOsm/L). Ten salt solutions with osmolarity between 286 mOsm/L and 394 mOsm/L (increments of 12 mOsm/L) plus an additional solution of 400 mOsm/L were tested twice on both the TearLab osmometer and a freezing point depression osmometer. For precision, we compared the two repeated osmolarity measurements of 11 solutions obtained from TearLab. For accuracy, we compared the averaged osmolarity measurements obtained from TearLab to those from the freezing point depression osmometer. For both precision and accuracy, Bland-Altman test of agreement was used. For precision, the upper 95% limit of agreement was 4.7 mOsm/L, and the lower 95% limit of agreement was -7.1 mOsm/L. The repeatability coefficient was 5.9 mOsm/L. For accuracy, the upper 95% limit of agreement was 4.8 mOsm/L and the lower 95% limit of agreement was -5.3 mOsm/L. The present study is the first study to demonstrate that the TearLab in situ osmometer can precisely and accurately measure osmolarity of salt solutions, including those with very high osmolarity. Future studies to evaluate the precision and the accuracy of the machine in measuring complex fluids, such as tears, need to be done, and the clinical significance of measuring tear osmolarity in patients needs to be further determined.

  20. Adsorption of small biological molecules on silica from diluted aqueous solutions: Quantitative characterization and implications to the Bernal's hypothesis

    NASA Astrophysics Data System (ADS)

    Basiuk, Vladimir A.; Gromovoy, Taras Yu.; Khil'Chevskaya, Elena G.

    1995-08-01

    To describe quantitatively the adsorption of prebiotically important compounds of low molecular weight (amino acids, short linear peptides, cyclic dipeptides, the Krebs's cycle and other carboxylic acids, nucleosides and related phosphates) on silica surface from diluted neutral aqueous solutions, equilibrium constants (K) and free energies (-ΔG) of adsorption were determined from the retention values measured by means of high-performance liquid chromatography on a silica gel column and from the isotherms measured under static conditions. For most carboxylic acids (including amino acids and linear peptides) -ΔG values were negative and K<1, thus showing very weak adsorption. Cyclic dipeptides (2,5-piperazinediones) exhibited higher adsorbability; -ΔG>0 and K>1 were found for most of them. Influence of the structure of α-substituent on the adsorbability is analyzed. A linear dependence of -ΔG on the number of aliphatic carbon atoms in a sorbate molecule was found for the series of aliphatic bifunctional amino acids, related dipeptides and 2,5-piperazinediones, as well as for the row from glycine to triglycyl glycine. The adsorption of nucleosides and their phosphates is characterized by much higherK and -ΔG values (of the order of 102 and 104, respectively). The adsorption data available from our work and literature are summarized and discussed with implications to the Bernal's hypothesis on the roles of solid surfaces in the prebiotic formation of biopolymers from monomeric ‘building blocks’.

  1. β-1,3-D-glucan schizophyllan/poly(dA) triple-helical complex in dilute solution.

    PubMed

    Sanada, Yusuke; Matsuzaki, Tsubasa; Mochizuki, Shinichi; Okobira, Tadashi; Uezu, Kazuya; Sakurai, Kazuo

    2012-01-12

    A certain length of poly(deoxyadenylic acid) (dA(X)) can form a novel complex with β-1,3-D-glucan schizophyllan (SPG) with a stoichiometric composition of one dA binding two main chain glucoses. We measured dilute solution properties for the complex with light and small-angle X-ray scattering as well as intrinsic viscosity and found that the complex behaves as a semiflexible rod without branching or cross-linking. We analyzed the data with the wormlike cylinder model, and the chain dimensions and the persistence length for the complexes were consistently determined. The chain flexibility was reduced to almost 25% upon complexation for dA/SPG and to 15% for S-dA/SPG, where S-dA denotes the phosphorothioated DNA analogue. The changes in the molar mass per unit length and the diameter indicated that the helix was elongated or stretched along the axis direction upon the complexation.

  2. Inefficacy of osmotic backwash induced by sodium chloride salt solution in controlling SWRO membrane fouling

    NASA Astrophysics Data System (ADS)

    Farooque, A. Mohammed; Al-Jeshi, Subhi; Saeed, Mohamed O.; Alreweli, Ali

    2014-12-01

    A study was conducted to evaluate the efficacy of osmotic backwash induced by high salt (NaCl) concentration solution on feed side of seawater reverse osmosis (SWRO) membranes, online and offline, in controlling membrane fouling and therefore minimizing/eliminating the need for chemical cleaning. SWRO membranes were deliberately fouled by feeding seawater from an open intake located on the Arabian Gulf Coast without dosing chemicals. The fouled membranes were subjected to offline cleaning with the salt solution of up to 25 % concentration. Despite the partial removal of foulants from the membrane surface, SWRO membrane performance could not be restored, indicating the ineffectiveness of osmotic backwash in aiding offline salt cleaning. Similarly, online osmotic backwash was found to be not only ineffective in removing foulants from membrane surfaces but actually increased the fouling rate, as indicated by faster fouling rates compared to other cases. Although the driving force required for the osmotic backwash existed, the generated back flow proved to be insufficient to detach foulants from membrane surfaces. During the study period, the average SWRO membrane flux was maintained between 19 and 23 LMH, whereas the average generated back flow flux by high salt concentration solution was only 11 LMH, which was not adequate to remove foulants from membrane surfaces. Moreover, it seems that the membrane configuration as well as inherent microstructure of SWRO membrane places certain constraints on the osmotic backwash process and renders osmotic backwash ineffective in tackling SWRO membrane fouling. Hence, chemical cleaning is essential to restore SWRO membrane performance whenever fouling occurs, and the use of highly concentrated salt solution does not have any significant benefit. Membrane autopsy revealed only an insignificant accumulation of biofouling layer despite the absence of disinfection. However, it was shown that culturable biofilm bacteria species

  3. Silica precipitation in acidic solutions: mechanism, pH effect, and salt effect.

    PubMed

    Gorrepati, Elizabeth A; Wongthahan, Pattanapong; Raha, Sasanka; Fogler, H Scott

    2010-07-06

    This study is the first to show that silica precipitation under very acidic conditions ([HCl] = 2-8 M) proceeds through two distinct steps. First, the monomeric form of silica is quickly depleted from solution as it polymerizes to form primary particles approximately 5 nm in diameter. Second, the primary particles formed then flocculate. A modified Smoluchowski equation that incorporates a geometric population balance accurately describes the exponential growth of silica flocs. Variation of the HCl concentration between 2 and 8 M further showed that polymerization to form primary particles and subsequent particle flocculation become exponentially faster with increasing acid concentration. The effect of salt was also studied by adding 1 M chloride salts to the solutions; it was found that salts accelerated both particle formation and growth rates in the order: AlCl(3) > CaCl(2) > MgCl(2) > NaCl > CsCl > no salt. It was also found that ionic strength, over cation identity, determines silica polymerization and particle flocculation rates. This research reveals that precipitation of silica products from acid dissolution of minerals can be studied apart from the mineral dissolution process. Thus, silica product precipitation from mineral acidization follows a two-step process--formation of 5 nm primary particles followed by particle flocculation--which becomes exponentially faster with increasing HCl concentration and with salts accelerating the process in the above order. This result has implications for any study of acid dissolution of aluminosilicate or silicate material. In particular, the findings are applicable to the process of acidizing oil-containing rock formations, a common practice of the petroleum industry where silica dissolution products encounter a low-pH, salty environment within the oil well.

  4. CO sub 2 induced inhibition of the localized corrosion of aluminum, Al-0. 5% Cu, and Al-2% Cu in dilute HF solution

    SciTech Connect

    Scully, J.R. . Dept. of Materials Science); Peebles, D.E. )

    1991-01-01

    This study presents work on corrosion of aluminum, Al-.5% Cu, and Al-2% Cu. Electrochemical tests were performed in dilute HF solutions both with and without CO{sub 2} sparging. It is suggested that CO{sub 2} or its reaction products interact with the passive film so that exposure of Cu in the oxide-solution interface is minimized. CO{sub 2} is investigated as a corrosion inhibitor. 4 refs. (JDL)

  5. An empirical correlation between the enthalpy of solution of aqueous salts and their ability to form hydrates

    SciTech Connect

    Pandelov, S.; Werhahn, Jasper C.; Pilles, Bert M.; Xantheas, Sotiris S.; Iglev, H.

    2010-09-30

    The ability of aqueous salt solutions to form hydrates by cooling them at ambient pressure is probed by infrared (IR) spectroscopy by examining the structure of the spectra in the hydrogen-bonding region (3,000 - 3,800 cm-1). A collection of 75 organic and inorganic salts in saturated solutions are examined. We have found a correlation between the enthalpy of solution of the salt and its ability to form a hydrate, namely that the salt’s enthalpy of solution is lower than the standard enthalpy of fusion of ice (6 kJ/mol). This observation can serve as an empirical rule that determines whether a salt will form a hydrate upon cooling from its aqueous solution.

  6. Ice crystallization in ultrafine water-salt aerosols: nucleation, ice-solution equilibrium, and internal structure.

    PubMed

    Hudait, Arpa; Molinero, Valeria

    2014-06-04

    Atmospheric aerosols have a strong influence on Earth's climate. Elucidating the physical state and internal structure of atmospheric aqueous aerosols is essential to predict their gas and water uptake, and the locus and rate of atmospherically important heterogeneous reactions. Ultrafine aerosols with sizes between 3 and 15 nm have been detected in large numbers in the troposphere and tropopause. Nanoscopic aerosols arising from bubble bursting of natural and artificial seawater have been identified in laboratory and field experiments. The internal structure and phase state of these aerosols, however, cannot yet be determined in experiments. Here we use molecular simulations to investigate the phase behavior and internal structure of liquid, vitrified, and crystallized water-salt ultrafine aerosols with radii from 2.5 to 9.5 nm and with up to 10% moles of ions. We find that both ice crystallization and vitrification of the nanodroplets lead to demixing of pure water from the solutions. Vitrification of aqueous nanodroplets yields nanodomains of pure low-density amorphous ice in coexistence with vitrified solute rich aqueous glass. The melting temperature of ice in the aerosols decreases monotonically with an increase of solute fraction and decrease of radius. The simulations reveal that nucleation of ice occurs homogeneously at the subsurface of the water-salt nanoparticles. Subsequent ice growth yields phase-segregated, internally mixed, aerosols with two phases in equilibrium: a concentrated water-salt amorphous mixture and a spherical cap-like ice nanophase. The surface of the crystallized aerosols is heterogeneous, with ice and solution exposed to the vapor. Free energy calculations indicate that as the concentration of salt in the particles, the advance of the crystallization, or the size of the particles increase, the stability of the spherical cap structure increases with respect to the alternative structure in which a core of ice is fully surrounded by

  7. Spectrophotometric investigation of reaction of uranyl salts with neutral organophosphorus compounds in aqueous solutions

    SciTech Connect

    Takshin, V.V.; Khokhlova, N.L.

    1985-07-01

    The authors study the reaction of uranyl salts with neutral organophosphorous compounds in aqueous solutions of mineral acids. They show that compounds of the R /SUB n/ P(O)-(OR) /SUB 3-n/ type (n = 0, 1, 2, 3; R = CH/sub 3/, C/sub 2/H/sub 5/) do not form complexes with UO/sub 2//sup 2 +/. In perchlorate solutions U/sub 2//sup 2 +/ forms complex with ((CH/sub 3/)/sub 2/ N)/sub 3/ PO. The equilibrium constant of this reaction is 6.4 + or - 0.6 mole/sup -1/. liter at 298 degrees K.

  8. Aqueous Biphasic Systems Based on Salting-Out Polyethylene Glycol or Ionic Solutions: Strategies for Actinide or Fission Product Separations

    SciTech Connect

    Rogers, Robin D.; Gutowski, Keith E.; Griffin, Scott T.; Holbrey, John D.

    2004-03-29

    Aqueous biphasic systems can be formed by salting-out (with kosmotropic, waterstructuring salts) water soluble polymers (e.g., polyethylene glycol) or aqueous solutions of a wide range of hydrophilic ionic liquids based on imidazolium, pyridinium, phosphonium and ammonium cations. The use of these novel liquid/liquid biphases for separation of actinides or other fission products associated with nuclear wastes (e.g., pertechnetate salts) has been demonstrated and will be described in this presentation.

  9. Rheological properties and thickening mechanism of aqueous diutan gum solution: Effects of temperature and salts.

    PubMed

    Xu, Long; Gong, Houjian; Dong, Mingzhe; Li, Yajun

    2015-11-05

    Rheological properties of a new microbial polysaccharide, diutan gum in aqueous solution have been systematically investigated. It is found that molecular aggregates of diutan gum can be formed at a very low concentration (0.12 g/L), and the mechanism of thickening by diutan gum is proposed. The viscosity retention rate of diutan gum changes little when increasing the temperature from 298 K to 348 K or in a high salinity solution (55.5 g L(-1)). Gel structure can be formed in the diutan gum solution, owing to the finding that the dynamic modulus has an exponential relationship with the concentration. The gel properties of diutan gum are not sensitive to temperature, and are virtually independent of cationic environment (Na(+) and Ca(2+)). The temperature/salt tolerance of the diutan gum solution is mainly attributed to its perfect double helix molecular conformation, the location of the side chains of its molecules, and its water retention capacity.

  10. Multicentre evaluation of reduced-osmolarity oral rehydration salts solution. International Study Group on Reduced-osmolarity ORS solutions.

    PubMed

    1995-02-04

    In developed countries, use of oral rehydration salts (ORS) solution with osmolarity lower than that of plasma has been recommended because of the risk of hypernatraemia. We compared the clinical efficacy of reduced-osmolarity ORS and standard ORS solutions in children with acute diarrhoea in four developing countries. 447 boys aged 1-24 months, admitted to hospitals in four countries with acute diarrhoea and signs of dehydration, were randomly assigned either standard ORS (311 mmol/L) or reduced-osmolarity ORS (224 mmol/L) solution. Total stool output was 39% greater (95% CI 11-75), total ORS intake 18% greater (3-33), and duration of diarrhoea 22% longer (2-45) in the standard ORS group than in the reduced-osmolarity ORS group. The risk of requiring intravenous infusion after completion of the initial oral rehydration was greater in children given standard ORS solution than in those given reduced-osmolarity ORS solution in three of the four countries (all-country relative risk 1.4 [0.9-2.4]). This relative risk was significantly increased only in non-breastfed children (2.0 [1.0-3.8], p < 0.05). In breastfed children, the relative risk of requiring intravenous infusion was not affected by the ORS solution (0.9 [0.4-2.0]). The mean sodium concentration 24 h after admission was significantly lower in the reduced-osmolarity ORS group than in the standard ORS group (135 [134-136] vs 138 [136-139] mmol/L, p < 0.01). Reduced-osmolarity ORS solution has beneficial effects on the clinical course of acute diarrhoea. Our findings support the use of reduced-osmolarity ORS solution in children with acute non-cholera diarrhoea in developing countries. Further studies are needed to find the best formulation and whether such a solution would be satisfactory for the treatment of cholera.

  11. Adding salt to a surfactant solution: Linear rheological response of the resulting morphologies

    SciTech Connect

    Gaudino, Danila; Pasquino, Rossana Grizzuti, Nino

    2015-11-15

    The micellar system composed of Cetylpyridinium Chloride-Sodium Salicylate (CPyCl-NaSal) in brine aqueous solutions has been studied by systematically changing the salt concentration, in order to investigate the rheology of the arising morphologies. In particular, the zero-shear viscosity and the linear viscoelastic response have been measured as a function of the NaSal concentration (with [CPyCl] = 100 mM). The Newtonian viscosity shows a nonmonotonic dependence upon concentration, passing through a maximum at NaSal/CPyCl ≈ 0.6, and eventually dropping at higher salt concentrations. The progressive addition of salt determines first a transition from a Newtonian to a purely Maxwell-like behavior as the length of the micelles significantly increases. Beyond the peak viscosity, the viscoelastic data show two distinct features. On the one hand, the main relaxation time of the system strongly decreases, while the plateau modulus remains essentially constant. Calculations based on the rheological data show that, as the binding salt concentration increases, there is a decrease in micelles breaking rate and a decrease in their average length. On the other hand, in the same concentration region, a low-frequency elastic plateau is measured. Such a plateau is considered as the signature of a tenuous, but persistent branched network, whose existence is confirmed by cryo-transmission electron microscopy images.

  12. Absorption and desorption of SO2 in aqueous solutions of diamine-based molten salts.

    PubMed

    Lim, Seung Rok; Hwang, Junhyeok; Kim, Chang Soo; Park, Ho Seok; Cheong, Minserk; Kim, Hoon Sik; Lee, Hyunjoo

    2015-05-30

    SO2 absorption and desorption behaviors were investigated in aqueous solutions of diamine-derived molten salts with a tertiary amine group on the cation and a chloride anion, including butyl-(2-dimethylaminoethyl)-dimethylammonium chloride ([BTMEDA]Cl, pKb=8.2), 1-butyl-1,4-dimethylpiperazinium chloride ([BDMP]Cl, pKb=9.8), and 1-butyl-4-aza-1-azoniabicyclo[2,2,2]octane chloride ([BDABCO]Cl, pKb=11.1). The SO2 absorption and desorption performance of the molten salt were greatly affected by the basicity of the molten salt. Spectroscopic, X-ray crystallographic, and computational results for the interactions of SO2 with molten salts suggest that two types of SO2-containg species could be generated depending on the basicity of the unquaternized amino group: a dicationic species comprising two different anions, HSO3(-) and Cl(-), and a monocationic species bearing Cl(-) interacting with neutral H2SO3. Copyright © 2015 Elsevier B.V. All rights reserved.

  13. ``Ordered'' structure in dilute solutions of sodium polystyrenesulfonates as studied by small-angle x-ray scattering

    NASA Astrophysics Data System (ADS)

    Ise, Norio; Okubo, Tsuneo; Kunugi, Shigeru; Matsuoka, Hideki; Yamamoto, K.; Ishii, Yasuo

    1984-10-01

    The small angle x-ray scattering measurements were performed for aqueous solutions of sodium polystyrenesulfonates having relatively narrow molecular weight distributions. As was observed for other synthetic macroions, polynucleotide and proteins, a single, broad peak was observed. The scattering vector at the peak position (Sm) was shifted toward larger values with increasing polymer concentration and toward lower values with increasing salt concentration, which confirmed earlier observations with polyacrylate and poly-L-lysine. The molecular weight dependence of the scattering behavior, which was earlier observed, was confirmed to be true for samples with Mw of 74 000, 18 000, and 4600. The mixture of two fractions with different Mw's gave a scattering curve which was again different from the composite curve obtained with the parent curves before mixing. A similar situation was observed for the mixture of polystyrenesulfonate and polyacrylate. Thus, it was concluded that the observed single peak indicates the presence of an intermolecular ordering, not an intramolecular ordering. The intermacroion distance (2Dexp) was thus calculated by using the Bragg equation. 2Dexp decreased with increasing polymer concentration and increased (not decreased) with increasing concentration of added salt and Mw. The 2Dexp values thus obtained were smaller beyond the experimental error than 2D0, a theoretical distance calculated from the concentration by assuming the uniform distribution of the macroions throughout the solution and the 2D0/2Dexp value amounted to 3.5 for high molecular weight samples. This fact indicates the presence of an intermacroion attractive interaction. When two fractions with different Mw's were compared at a given number concentration of macroions, the 2Dexp value for the sample of a larger Mw was smaller than that for the fraction of a smaller Mw. This implies that the attraction must be intensified, though unexpectedly, with increasing valency of the

  14. Analytical Results from Salt Solution Feed Tank (SSFT) Samples HTF-16-6 and HTF-16-40

    SciTech Connect

    Peters, T.

    2016-09-23

    Two samples from the Salt Solution Feed Tank (SSFT) were analyzed by SRNL, HTF-16-6 and HTF-16-40. Multiple analyses of these samples indicate a general composition almost identical to that of the Salt Batch 8-B feed and the Tank 21H sample results.

  15. Molecular Thermodynamics for Swelling of a Mesoscopic Ionomer Gelin 1:1 Salt Solutions

    SciTech Connect

    Victorov, Alexey; Radke, Clayton; Prausnitz,John

    2005-06-15

    For a microphase-separated diblock copolymer ionic gel swollen in salt solution, a molecular-thermodynamic model is based on the self-consistent field theory in the limit of strongly segregated copolymer subchains. The geometry of microdomains is described using the Milner generic wedge construction neglecting the packing frustration. Thermodynamic functions are expressed analytically for gels of lamellar, bicontinuous, cylindrical and spherical morphologies. Molecules are characterized by chain composition, length, rigidity, degree of ionization, and by effective polymer-polymer and polymer-solvent interaction parameters. The model predicts equilibrium solvent uptakes and the equilibrium microdomain spacing for gels swollen in salt solutions. Results are given for details of the gel structure: distribution of mobile ions and polymer segments, and the electric potential across microdomains. Apart from effects obtained by coupling classical Flory-Rehner theory with Donnan equilibria, viz., increased swelling with polyelectrolyte charge and shrinking of gel upon addition of salt, the model predicts the effects of microphase morphology on swelling.

  16. Enhanced copper surface protection in aqueous solutions containing short-chain alkanoic acid potassium salts.

    PubMed

    Abelev, Esta; Starosvetsky, David; Ein-Eli, Yair

    2007-10-23

    The ability of dissolved potassium monocarboxylate salts to produce surface passivation and to inhibit aqueous corrosion of copper was studied. The electrochemical measurements indicate that the inhibiting efficiency of these compounds, with a general formula Cn-1H2n-1COOK or CnK (n=3...12), is dependent on the hydrocarbon chain length. The inhibiting efficiency was higher for a longer hydrocarbon chain of n-alkanoic acid. The degree of copper protection was found to increase with an increase in n-alkanoic acid potassium salt concentration; the optimum concentration of potassium dodecanoate (C12K) in sulfate solutions was found to be 0.07 M. The protective layers formed at the copper surface subsequent to exposure in various n-alkanoic acid potassium salt solutions were characterized by contact angle measurements, electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared reflection spectroscopy. Pronounced copper protection was attributed to the growth of a protective film on the copper surface, containing both copper oxides and copper carboxylate compounds. It is suggested that the organic molecules enhance copper protection by covering copper oxides with a thin and dense organic layer, which prevents water molecules or aggressive anions from interacting with the copper surface.

  17. Viscosity-Reducing Bulky-Salt Excipients Prevent Gelation of Protein, but Not Carbohydrate, Solutions.

    PubMed

    Kumar, Awanish; Klibanov, Alexander M

    2017-08-01

    The problem of gelation of concentrated protein solutions, which poses challenges for both downstream protein processing and liquid formulations of pharmaceutical proteins, is addressed herein by employing previously discovered viscosity-lowering bulky salts. Procainamide-HCl and the salt of camphor-10-sulfonic acid with L-arginine (CSA-Arg) greatly retard gelation upon heating and subsequent cooling of the model proteins gelatin and casein in water: Whereas in the absence of additives the proteins form aqueous gels within several hours at room temperature, procainamide-HCl for both proteins and also CSA-Arg for casein prevent gel formation for months under the same conditions. The inhibition of gelation by CSA-Arg stems exclusively from the CSA moiety: CSA-Na was as effective as CSA-Arg, while Arg-HCl was marginally or not effective. The tested bulky salts did not inhibit (and indeed accelerated) temperature-induced gel formation in aqueous solutions of all examined carbohydrates-starch, agarose, alginate, gellan gum, and carrageenan.

  18. Effects of Detergent β-Octylglucoside and Phosphate Salt Solutions on Phase Behavior of Monoolein Mesophases

    PubMed Central

    Khvostichenko, Daria S.; Ng, Johnathan J.D.; Perry, Sarah L.; Menon, Monisha; Kenis, Paul J.A.

    2013-01-01

    Using small-angle x-ray scattering (SAXS), we investigated the phase behavior of mesophases of monoolein (MO) mixed with additives commonly used for the crystallization of membrane proteins from lipidic mesophases. In particular, we examined the effect of sodium and potassium phosphate salts and the detergent β-octylglucoside (βOG) over a wide range of compositions relevant for the crystallization of membrane proteins in lipidic mesophases. We studied two types of systems: 1), ternary mixtures of MO with salt solutions above the hydration boundary; and 2), quaternary mixtures of MO with βOG and salt solutions over a wide range of hydration conditions. All quaternary mixtures showed highly regular lyotropic phase behavior with the same sequence of phases (Lα, Ia3d, and Pn3m) as MO/water mixtures at similar temperatures. The effects of additives in quaternary systems agreed qualitatively with those found in ternary mixtures in which only one additive is present. However, quantitative differences in the effects of additives on the lattice parameters of fully hydrated mesophases were found between ternary and quaternary mixtures. We discuss the implications of these findings for mechanistic investigations of membrane protein crystallization in lipidic mesophases and for studies of the suitability of precipitants for mesophase-based crystallization methods. PMID:24138861

  19. Molecular dynamics study of salt–solution interface: Solubility and surface charge of salt in water

    SciTech Connect

    Kobayashi, Kazuya; Liang, Yunfeng E-mail: matsuoka@earth.kumst.kyoto-u.ac.jp; Matsuoka, Toshifumi E-mail: matsuoka@earth.kumst.kyoto-u.ac.jp; Sakka, Tetsuo

    2014-04-14

    The NaCl salt–solution interface often serves as an example of an uncharged surface. However, recent laser-Doppler electrophoresis has shown some evidence that the NaCl crystal is positively charged in its saturated solution. Using molecular dynamics (MD) simulations, we have investigated the NaCl salt–solution interface system, and calculated the solubility of the salt using the direct method and free energy calculations, which are kinetic and thermodynamic approaches, respectively. The direct method calculation uses a salt–solution combined system. When the system is equilibrated, the concentration in the solution area is the solubility. In the free energy calculation, we separately calculate the chemical potential of NaCl in two systems, the solid and the solution, using thermodynamic integration with MD simulations. When the chemical potential of NaCl in the solution phase is equal to the chemical potential of the solid phase, the concentration of the solution system is the solubility. The advantage of using two different methods is that the computational methods can be mutually verified. We found that a relatively good estimate of the solubility of the system can be obtained through comparison of the two methods. Furthermore, we found using microsecond time-scale MD simulations that the positively charged NaCl surface was induced by a combination of a sodium-rich surface and the orientation of the interfacial water molecules.

  20. Coarse-grained model of glycosaminoglycans in aqueous salt solutions. A field-theoretical approach.

    PubMed

    Kolesnikov, Andrei L; Budkov, Yurij A; Nogovitsyn, Evgenij A

    2014-11-20

    We present results of self-consistent field calculations of thermodynamic and structural properties of glycosaminoglycans (chondroitin sulfate, hyaluronic acid, and heparin) in aqueous solutions with added monovalent and divalent salts. A semiphenomenological coarse-grained model for semiflexible polyelectrolyte chains in solution is proposed. The coarse-grained model permits one to focus on the essential features of these systems and provides significant computational advantages with respect to more detailed models. Our approach relies on the method of Gaussian equivalent representation for the calculation of the partition functions in the form of functional integrals. This method provides reliable thermodynamic information for polyelectrolyte solutions over wide ranges of monomer concentrations. In the present work, we use the comparison and fitting of the experimental osmotic pressure with a theoretical equation of state within the Gaussian equivalent representation. The degrees of ionization, radii of gyration, persistence lengths, and structure factors of chondroitin sulfate, hyaluronic acid, and heparin in aqueous solutions with added monovalent and divalent salts are calculated and discussed.

  1. Introductory lecture: interpreting and predicting Hofmeister salt ion and solute effects on biopolymer and model processes using the solute partitioning model.

    PubMed

    Record, M Thomas; Guinn, Emily; Pegram, Laurel; Capp, Michael

    2013-01-01

    Understanding how Hofmeister salt ions and other solutes interact with proteins, nucleic acids, other biopolymers and water and thereby affect protein and nucleic acid processes as well as model processes (e.g. solubility of model compounds) in aqueous solution is a longstanding goal of biophysical research. Empirical Hofmeister salt and solute "m-values" (derivatives of the observed standard free energy change for a model or biopolymer process with respect to solute or salt concentration m3) are equal to differences in chemical potential derivatives: m-value = delta(dmu2/dm3) = delta mu23, which quantify the preferential interactions of the solute or salt with the surface of the biopolymer or model system (component 2) exposed or buried in the process. Using the solute partitioning model (SPM), we dissect mu23 values for interactions of a solute or Hofmeister salt with a set of model compounds displaying the key functional groups of biopolymers to obtain interaction potentials (called alpha-values) that quantify the interaction of the solute or salt per unit area of each functional group or type of surface. Interpreted using the SPM, these alpha-values provide quantitative information about both the hydration of functional groups and the competitive interaction of water and the solute or salt with functional groups. The analysis corroborates and quantifies previous proposals that the Hofmeister anion and cation series for biopolymer processes are determined by ion-specific, mostly unfavorable interactions with hydrocarbon surfaces; the balance between these unfavorable nonpolar interactions and often-favorable interactions of ions with polar functional groups determine the series null points. The placement of urea and glycine betaine (GB) at opposite ends of the corresponding series of nonelectrolytes results from the favorable interactions of urea, and unfavorable interactions of GB, with many (but not all) biopolymer functional groups. Interaction potentials and

  2. Phase behavior of concentrated hydroxypropyl methylcellulose solution in the presence of mono and divalent salt.

    PubMed

    Almeida, Nalinda; Rakesh, Leela; Zhao, Jin

    2014-01-01

    Thermo reversible sol-gel transitions of hydroxypropylmethylcellulose (HPMC) are critical for many pharmaceutical, cosmetic, and food applications. This study examined the effects of salt (NaCl and CaCl₂) on the viscoelastic properties of concentrated low molecular weight HPMC solutions and found that the gelation temperature decreased linearly as a function of salt concentrations, independent of valency of cations and the mole concentration of anions. Thermal analysis showed that the depression of melting temperature can be fitted for both NaCl and CaCl₂ as a function of the total number of ions by a single linear curve, which was consistent with the melting point depression of pure water by NaCl and CaCl₂, but with a higher linear slope.

  3. A new procedure to measure effective molecular diffusion coefficients of salts solutions in building materials

    NASA Astrophysics Data System (ADS)

    Delgado, J. M. P. Q.

    2013-06-01

    The aim of this work is to present a mathematical and experimental formulation of a new simple procedure for the measurement of effective molecular diffusion coefficients of a salt solution in a water-saturated building material. This innovate experimental procedure and mathematical formulation is presented in detail and experimental values of "effective" molecular diffusion coefficient of sodium chloride in a concrete sample ( w/ c = 0.45), at five different temperatures (between 10 and 30 °C) and four different initial NaCl concentrations (between 0.1 and 0.5 M), are reported. The experimental results obtained are in good agreement with the theoretical and experimental values of molecular diffusion coefficient presented in literature. An empirical correlation is presented for the prediction of "effective" molecular diffusion coefficient over the entire range of temperatures and initial salt concentrations studied.

  4. Ionic conductivity of dual-phase polymer electrolytes comprised of NBR/SBR latex films swollen with lithium salt solutions

    SciTech Connect

    Matsumoto, Morihiko; Ichino, Toshihiro; Rutt, J.S.; Nishi, Shiro . NTT Interdisciplinary Research Lab.)

    1994-08-01

    Dual-phase polymer electrolytes (DPE) with high ionic conductivity and good mechanical strength were prepared by swelling poly(acrylonitrile-co-butadiene) rubber (NBR) and poly(styrene-co-butadiene) rubber (SBR) mixed latex films with lithium salt solutions (e.g., 1M LiClO[sub 4]/[gamma]-butyrolactone). The latex films retain particle morphology in the solid state. The NBR phase (formed from fused NBR latex particles) is polar and is impregnated selectively with polar lithium salt solutions, yielding ion-conductive channels, whereas the SBR phase (formed from fused SBR latex particles) is nonpolar and is not impregnated, providing a mechanically supportive matrix. The ionic conductivity of the DPE increased dramatically with increasing content of lithium salt solution, and higher amounts of solution were imbibed with increasing content of NBR relative to SBR. Several factors which affect the ionic conductivity of this system were examined, and the highest ionic conductivity (>10[sup [minus]3] S/cm) was obtained when either an NBR/SBR 70/30 (w/w) or a 50/50 (w/w) latex film was saturated with 1M LiClO[sub 4]/[gamma]-BL solution or 1M LiClO[sub 4]/[gamma]-BL/DME solution. Ion-conductive behavior changed critically with increasing lithium salt solution uptake. At low levels of lithium salt solution uptake, evidence suggested that ionic conductivity of the absorbed lithium salt solution was strongly influenced by the presence of the NBR in the ion-conductive channel, but at higher levels, the effects of the NBR were reduced and free'' lithium salt solution was present.

  5. Photochromism of a spiropyran and a diarylethene in bile salt aggregates in aqueous solution.

    PubMed

    Santos, Cerize S; Miller, Allyson C; Pace, Tamara C S; Morimitsu, Kentaro; Bohne, Cornelia

    2014-09-30

    Bile salt aggregates incorporate aqueous-insoluble photochromic compounds. The photochromism of a spiropyran (1, 1',3',3'-trimethyl-6-nitrospiro[2H-1]-benzopyran-2,2'-indoline) and a diarylethene derivative (2, 1,2-bis(2,4-dimethyl-5-phenyl-3-thienyl)-3,3,4,4,5,5-hexafluoro-1-cyclopentene) was quantified in different bile salt aggregates. These aggregates act as efficient hosts to solubilize aqueous insoluble photochromic compounds where either both isomers are nonpolar, for example, 2, or compounds where one isomer is hydrophobic and the other is more polar, for example, 1. Methodology was developed to determine molar absorptivity coefficients for solutions containing both isomers and to determine the photoconversion quantum yields under continuous irradiation. The methods were validated by determining parameters in homogeneous solution, which were the same as previously reported. In the case of the colored isomer of 1, the molar extinction coefficient in ethanol at 537 nm ((3.68 ± 0.03) × 10(4) cm(-1) M(-1)) was determined with higher precision. The quantum yields for the photoconversion between the isomers of 2 were shown to be the same in cyclohexane and in the aggregates of sodium cholate (NaCh), deoxycholate (NaDC), and taurocholate (NaTC), showing that bile salt aggregates are not sufficiently rigid to affect the equilibrium between the two possible conformers of the colorless form. In contrast, for 1 the quantum yields for the conversion from the colorless to the colored isomer were higher in bile salts than in ethanol, and the quantum yield was highest in the more hydrophobic aggregates of NaDC, followed by NaCh and then NaTC. The structure of the bile salt had no effect on the quantum yield for the conversion of the colored to the colorless isomer of 1, but these values were higher than in ethanol. For all three bile salts, the absorption maximum for the colored form of 1 suggested that this isomer was located in an environment that is more polar than

  6. RESULTS OF ANALYSES OF MACROBATCH 3 DECONTAMINATED SALT SOLUTION (DSS) COALESCER AND PRE-FILTERS

    SciTech Connect

    Peters, T.; Fondeur, F.; Fink, S.

    2012-06-13

    SRNL analyzed the pre-filter and Decontamination Salt Solution (DSS) coalescer from MCU by several analytical methods. The results of these analyses indicate that overall there is light to moderate solids fouling of both the coalescer and pre-filter elements. The majority of the solids contain aluminum, sodium, silicon, and titanium, in oxide and/or hydroxide forms that we have noted before. The titanium is presumably precipitated from leached, dissolved monosodium titanate (MST) or fines from MST at ARP, and the quantity we find is significantly greater than in the past. A parallel report discusses potential causes for the increased leaching rate of MST, showing that increases in free hydroxide concentration of the feed solutions and of chemical cleaning solutions lead to faster leaching of titanium.

  7. The use of saline W, a physiological salt solution for experimentation on insect immunity.

    PubMed

    Jarosz, J

    1988-01-01

    In a series of induction experiments using various Ringer solutions attempts were made to determine whether saline W, a physiological salt solution for Lepidoptera, when injected into the larval haemocoel of the greater wax moth could be recognized by the insect as a non-self molecule. Laboratory bioassays indicated the loss of insect body integrity following intracoelomic injection of saline W and three other salines, increased levels of haemolymph lysozyme activity (EC 3. 2. 1. 17), and elevated resistance to the bacterial parasite, Pseudomonas aeruginosa. The inducing effect of saline W was stronger than dipterous Ringer's solution or other physiological salines. The stimulating effects indicate that the moth distinguishes between self and non-self, and this provides a new insight into the induction of the immune response.

  8. Faraday Discussion 160 Introductory Lecture: Interpreting and Predicting Hofmeister Salt Ion and Solute Effects on Biopolymer and Model Processes Using the Solute Partitioning Model

    PubMed Central

    Record, M. Thomas; Guinn, Emily; Pegram, Laurel; Capp, Michael

    2013-01-01

    Understanding how Hofmeister salt ions and other solutes interact with proteins, nucleic acids, other biopolymers and water and thereby affect protein and nucleic acid processes as well as model processes (e.g solubility of model compounds) in aqueous solution is a longstanding goal of biophysical research. Empirical Hofmeister salt and solute “m-values” (derivatives of the observed standard free energy change for a model or biopolymer process with respect to solute or salt concentration m3) are equal to differences in chemical potential derivatives: m-value = Δ(dμ2/dm3) = Δμ23 which quantify the preferential interactions of the solute or salt with the surface of the biopolymer or model system (component 2) exposed or buried in the process. Using the SPM, we dissect μ23 values for interactions of a solute or Hofmeister salt with a set of model compounds displaying the key functional groups of biopolymers to obtain interaction potentials (called α-values) that quantify the interaction of the solute or salt per unit area of each functional group or type of surface. Interpreted using the SPM, these α-values provide quantitative information about both the hydration of functional groups and the competitive interaction of water and the solute or salt with functional groups. The analysis corroborates and quantifies previous proposals that the Hofmeister anion and cation series for biopolymer processes are determined by ion-specific, mostly unfavorable interactions with hydrocarbon surfaces; the balance between these unfavorable nonpolar interactions and often-favorable interactions of ions with polar functional groups determine the series null points. The placement of urea and glycine betaine (GB) at opposite ends of the corresponding series of nonelectrolytes results from the favorable interactions of urea, and unfavorable interactions of GB, with many (but not all) biopolymer functional groups. Interaction potentials and local-bulk partition coefficients

  9. Equilibrium, kinetic and thermodynamic study of cesium adsorption onto nanocrystalline mordenite from high-salt solution.

    PubMed

    Lee, Keun-Young; Park, Minsung; Kim, Jimin; Oh, Maengkyo; Lee, Eil-Hee; Kim, Kwang-Wook; Chung, Dong-Yong; Moon, Jei-Kwon

    2016-05-01

    In this study, the equilibrium, kinetics and thermodynamics of cesium adsorption by nanocrystalline mordenite were investigated under cesium contamination with high-salt solution, simulating the case of an operation and decommissioning of nuclear facilities or an accident during the processes. The adsorption rate constants were determined using a pseudo second-order kinetic model. The kinetic results strongly demonstrated that the cesium adsorption rate of nano mordenite is extremely fast, even in a high-salt solution, and much faster than that of micro mordenite. In the equilibrium study, the Langmuir isotherm model fit the cesium adsorption data of nano mordenite better than the Freundlich model, which suggests that cesium adsorption onto nano mordenite is a monolayer homogeneous adsorption process. The obtained thermodynamic parameters indicated that the adsorption involved a very stable chemical reaction. In particular, the combination of rapid particle dispersion and rapid cesium adsorption of the nano mordenite in the solution resulted in a rapid and effective process for cesium removal without stirring, which may offer great advantages for low energy consumption and simple operation.

  10. Aggregate transitions in aqueous solutions of sodium dodecylsulfate with a "gemini-type" organic salt.

    PubMed

    Yu, Defeng; Tian, Maozhang; Fan, Yaxun; Ji, Gang; Wang, Yilin

    2012-06-07

    Effects of a "gemini-type" organic salt 1,2-bis(2-benzylammoniumethoxy) ethane dichloride (BEO) on the aggregation behavior of sodium dodecylsulfate (SDS) have been investigated by turbidity, surface tension, isothermal titration microcalorimetry, dynamic light scattering, cryogenic transmission electron microscopy, (1)H NMR spectroscopy, and differential scanning microcalorimetry. The aggregation behavior of the SDS/BEO mixed aqueous solution shows strong concentration and ratio dependence. For the SDS/BEO solution with a molar ratio of 5:1, large loose irregular aggregates, vesicles, and long thread-like micelles are formed in succession with the increase of the total SDS and BEO concentration. Because BEO has two positive charges, the SDS/BEO solution may consist of the (SDS)(2)-BEO gemini-type complex, the SDS-BEO complex and extra SDS. The aggregation ability and surface activity of the SDS/BEO mixture exhibit the characteristics of gemini-type surfactants. Along with the results of DSC and (1)H NMR, the (SDS)(2)-BEO gemini-type structure is confirmed to exist in the system. This work provides an approach to construct the surfactant systems with the characteristics of gemini surfactants through intermolecular interaction between a two-charged organic salt and oppositely charged single-chain surfactants.

  11. Cytotoxicity, interaction with dentine and efficacy on multispecies biofilms of a modified salt solution intended for endodontic disinfection in a new in vitro biofilm model.

    PubMed

    van der Waal, S V; Scheres, N; de Soet, J J; Wesselink, P R; Crielaard, W

    2015-02-01

    To investigate the cytotoxicity of a modified salt solution (MSS) and evaluate the antimicrobial properties of MSS on in vitro biofilm models. In a metabolic assay, fibroblasts derived from periodontal ligaments (PDL) of human extracted teeth were cultured and challenged with MSS or controls. Then, in active attachment biofilm models, the efficacy of MSS in the presence of dentine powder and in eliminating mature biofilms was investigated. In the dentine assay, a biofilm of Enterococcus faecalis was employed. For the final assay, microorganisms were retrieved from infected root canals and cultured to produce biofilms. After the treatments with MSS or the controls, the biofilms were collected, serially diluted and plated. The colony-forming units were counted. One-way anova was used to analyse the differences between the groups. A P < 0.05 was considered significant. The PDL fibroblasts remained metabolically active after challenges with MSS. Dentine powder did not alter the efficacy of MSS (P > 0.05). In endodontic biofilms, the culturable bacteria were equally reduced by MSS, 2% chlorhexidine (CHX) or 2% sodium hypochlorite (NaOCl) (P > 0.05). Modified salt solution is noncytotoxic in vitro and has good antimicrobial properties equal to CHX and NaOCl. Although the results are promising, ex vivo and in vivo studies are needed before its use as an interappointment root canal dressing can be considered. © 2014 International Endodontic Journal. Published by John Wiley & Sons Ltd.

  12. Diffusivities of lysozyme in aqueous MgCl2 solutions from dynamic light-scattering data:  Effect of protein and salt concentrations

    SciTech Connect

    Grigsby, J. J.; Blanch, H. W.; Prausnitz, J. M.

    2000-03-25

    Dynamic light-scattering (DLS) studies are reported for lysozyme in aqueous magnesium chloride solutions at ionic strengths 0.6, 0.8, and 1.0 M for a temperature range 10–30 °C at pH 4.0. The diffusion coefficient of lysozyme was calculated as a function of protein concentration, salt concentration, temperature, and scattering angle. A Zimm-plot analysis provided the infinitely-dilute diffusion coefficient and the protein-concentration dependence of the diffusion coefficient. The hydrodynamic radius of a lysozyme monomer was obtained from the Stokes–Einstein equation; it is 18.6 ± 1.0 Å. The difference (1.4 Å) between the hydrodynamic and the crystal-structure radius is attributed to binding of Mg2+ ions to the protein surface and subsequent water structuring. The effect of protein concentration on the diffusion coefficient indicates that attractive interactions increase as the temperature falls at fixed salt concentration. However, when plotted against ionic strength, attractive interactions exhibit a maximum at ionic strength 0.84 M, probably because Mg2+–protein binding and water structuring become increasingly important as the concentration of magnesium ion rises. Finally, the present work suggests that inclusion of ion binding and water structuring at the protein surface in a pair-potential model is needed to achieve accurate predictions of protein-solution phase behavior.

  13. Infinite dilution partial molar properties of aqueous solutions of nonelectrolytes. 1. Equations for partial molar volumes at infinite dilution and standard thermodynamic functions of hydration of volatile nonelectrolytes over wide ranges of conditions

    SciTech Connect

    Plyasunov, A.V.; O'Connell, J.P.; Wood, R.H.

    2000-02-01

    A semitheoretical expression for partial molar volumes at infinite dilution of aqueous nonelectrolyte solutes has been developed employing the collection of properties from fluctuation solution theory for use over wide ranges of temperature and pressure. The form of the solution expression was suggested by a comparison of solute/solvent and solvent/solvent direct correlations function integrals (DCFI). The selection of solvent density and compressibility as model variables provides a correct description in the critical region while second virial coefficients have been used to give a rigorous expression in the low density region. The formulation has been integrated to obtain analytic expressions for thermodynamic properties of hydration at supercritical temperatures. The equation is limited to solutes for which B{sub 12} (the second cross virial coefficient between water and a solute molecule) is known or can be estimated. Regression of the three remaining parameters gives good correlations of the available experimental data. A strategy for estimating these parameters allows prediction from readily available data.

  14. Electrically conducting poly(para-phenylene sulfide) prepared by doping with nitrosyl salts from solution

    NASA Astrophysics Data System (ADS)

    Rubner, Michael; Cukor, Peter; Jopson, Harriet; Deits, Walter

    1982-03-01

    Para(polyphenylene sulfide) may be doped spontaneously and rapidly with nitrosyl salts (NOPF6, NOSbF6) from solution to yield an electrically conducting material (10-1ohm-1cm-1). The level of conductivity is primarily dependent on the extent of dopant incorporation, which in turn is determined by the polymer’s crystallinity; the more amorphous the polymer, the more dopant it takes up and the more conductive it becomes. The incorporation of dopants produces irreversible chemical changes in the polymer resulting in the deterioration of its mechanical properties.

  15. Partial and charge structure fonctions of monodisperse DNA fragments in salt free aqueous solution

    NASA Astrophysics Data System (ADS)

    van der Maarel, J. R. C.; Groot, L. C. A.; Mandel, M.; Jesse, W.; Jannink, G.; Rodriguez, V.

    1992-01-01

    Observations of the partial structure functions and the charge structure function are reported for an aqueous solution of monodisperse rodlike DNA fragments, without added simple salt. In the reciprocal space interval qgeqslant 0.075 Å^{-1}, the neutron scattering data can be fitted by the correlation functions derived from the exact solution of the Poisson-Boltzmann equation in the cell model. The fit is equally good for all partial structure functions as well as the charge structure function. The cell model seems to be appropriate for this kind of solution. On reconstitue la structure d'une solution aqueuse de fragments monodisperse d'ADN à l'aide des fonctions de structure partielles et de la fonction de structure de charge mesurées par diffusion des neutrons aux petits angles. Dans l'intervalle qgeqslant 0,075 Å^{-1}, les fonctions de corrélation calculées à partir de la solution exacte de l'équation de Poisson-Boltzmann et du modèle cellulaire, ajustent les données de l'expérience. Cela est vrai aussi bien pour chacune des fonctions de structure partielles que pour la fonction de structure de charge. Le modèle cellulaire semble donc être un modèle convenable pour ces solutions.

  16. Super-absorbency and phase transition of gels in physiological salt solutions

    NASA Astrophysics Data System (ADS)

    Zhang, Yong-Qing; Tanaka, Toyoichi; Shibayama, Mitsuhiro

    1992-11-01

    IONIC gels with the ability to absorb many times their dry weight of water have found widespread use as absorbents in medical, chemical and agricultural applications1. The dramatic swelling power of these super-absorbent gels results from both the electrostatic repulsion between the charges on the polymer chains, and the osmotic pressure of the counter-ions2. In salt solutions such as saline, urine or blood, however, excess Na+ and Cl- ions screen the polymer charges and eliminate the osmotic imbalance, effectively changing the properties of the material to that of a non-ionic gel3: this greatly diminishes the swelling power, and hence the utility of these materials under physiological conditions. Here we report the development of a system combining a non-ionic gel with ionized surfactants, which shows super-absorbent behaviour even in the presence of salt. In water, the hydrophobic gel facilitates the formation of spherical surfactant micelles, which mimic the charged sites of an ionic gel. As the salt concentration is increased, the micelles become rod-like, maintaining the electrostatic repulsion along the polymer chains and thereby preserving the swelling power of the gel.

  17. Molecular Dynamics Simulation of the Aggregation Patterns in Aqueous Solutions of Bile Salts at Physiological Conditions.

    PubMed

    Mustan, Fatmegyul; Ivanova, Anela; Madjarova, Galia; Tcholakova, Slavka; Denkov, Nikolai

    2015-12-24

    Classical molecular dynamics simulations are employed to monitor the aggregation behavior of six bile salts (nonconjugated and glycine- and taurine-conjugated sodium cholate and sodium deoxycholate) with concentration of 10 mM in aqueous solution in the presence of 120 mM NaCl. There are 150 ns trajectories generated to characterize the systems. The largest stable aggregates are analyzed to determine their shape, size, and stabilizing forces. It is found that the aggregation is a hierarchical process and that its kinetics depends both on the number of hydroxyl groups in the steroid part of the molecules and on the type of conjugation. The micelles of all salts are similar in shape-deformed spheres or ellipsoids, which are stabilized by hydrophobic forces, acting between the steroid rings. The differences in the aggregation kinetics of the various conjugates are rationalized by the affinity for hydrogen bond formation for the glycine-modified salts or by the longer time needed to achieve optimum packing for the tauro derivatives. Evidence is provided for the hypothesis from the literature that the entirely hydrophobic core of all aggregates and the enhanced dynamics of the molecules therein should be among the prerequisites for their pronounced solubilization capacity for hydrophobic substances in vivo.

  18. Modeling of dielectric properties of aqueous salt solutions with an equation of state.

    PubMed

    Maribo-Mogensen, Bjørn; Kontogeorgis, Georgios M; Thomsen, Kaj

    2013-09-12

    The static permittivity is the most important physical property for thermodynamic models that account for the electrostatic interactions between ions. The measured static permittivity in mixtures containing electrolytes is reduced due to kinetic depolarization and reorientation of the dipoles in the electrical field surrounding ions. Kinetic depolarization may explain 25-75% of the observed decrease in the permittivity of solutions containing salts, but since this is a dynamic property, this effect should not be included in the thermodynamic modeling of electrolytes. Kinetic depolarization has, however, been ignored in relation to thermodynamic modeling, and authors have either neglected the effect of salts on permittivity or used empirical correlations fitted to the measured static permittivity, leading to an overestimation of the reduction in the thermodynamic static permittivity. We present a new methodology for obtaining the static permittivity over wide ranges of temperatures, pressures, and compositions for use within an equation of state for mixed solvents containing salts. The static permittivity is calculated from a new extension of the framework developed by Onsager, Kirkwood, and Fröhlich to associating mixtures. Wertheim's association model as formulated in the statistical associating fluid theory is used to account for hydrogen-bonding molecules and ion-solvent association. Finally, we compare the Debye-Hückel Helmholtz energy obtained using an empirical model with the new physical model and show that the empirical models may introduce unphysical behavior in the equation of state.

  19. Interconnection of Salt-induced Hydrophobic Compaction and Secondary Structure Formation Depends on Solution Conditions

    PubMed Central

    Haldar, Shubhasis; Chattopadhyay, Krishnananda

    2012-01-01

    What happens in the early stage of protein folding remains an interesting unsolved problem. Rapid kinetics measurements with cytochrome c using submillisecond continuous flow mixing devices suggest simultaneous formation of a compact collapsed state and secondary structure. These data seem to indicate that collapse formation is guided by specific short and long range interactions (heteropolymer collapse). A contrasting interpretation also has been proposed, which suggests that the collapse formation is rapid, nonspecific, and a trivial solvent related compaction, which could as well be observed by a homopolymer (homopolymer collapse). We address this controversy using fluorescence correlation spectroscopy (FCS), which enables us to monitor the salt-induced compaction accompanying collapse formation and the associated time constant directly at single molecule resolution. In addition, we follow the formation of secondary structure using far UV CD. The data presented here suggest that both these models (homopolymer and heteropolymer) could be applicable depending on the solution conditions. For example, the formation of secondary structure and compact state is not simultaneous in aqueous buffer. In aqueous buffer, formation of the compact state occurs through a two-state co-operative transition following heteropolymer formalism, whereas secondary structure formation takes place gradually. In contrast, in the presence of urea, a compaction of the protein radius occurs gradually over an extended range of salt concentration following homopolymer formalism. The salt-induced compaction and the formation of secondary structure take place simultaneously in the presence of urea. PMID:22303014

  20. Glyme-lithium salt equimolar molten mixtures: concentrated solutions or solvate ionic liquids?

    PubMed

    Ueno, Kazuhide; Yoshida, Kazuki; Tsuchiya, Mizuho; Tachikawa, Naoki; Dokko, Kaoru; Watanabe, Masayoshi

    2012-09-13

    To demonstrate a new family of ionic liquids (ILs), i.e., "solvate" ionic liquids, the properties (thermal, transport, and electrochemical properties, Lewis basicity, and ionicity) of equimolar molten mixtures of glymes (triglyme (G3) and tetraglyme (G4)) and nine different lithium salts (LiX) were investigated. By exploring the anion-dependent properties and comparing them with the reported data on common aprotic ILs, two different classes of liquid regimes, i.e., ordinary concentrated solutions and "solvate" ILs, were found in the glyme-Li salt equimolar mixtures ([Li(glyme)]X) depending on the anionic structures. The class a given [Li(glyme)]X belonged to was governed by competitive interactions between the glymes and Li cations and between the counteranions (X) and Li cations. [Li(glyme)]X with weakly Lewis basic anions can form long-lived [Li(glyme)](+) complex cations. Thus, they behaved as typical ionic liquids. The lithium "solvate" ILs based on [Li(glyme)]X have many desirable properties for lithium-conducting electrolytes, including high ionicity, a high lithium transference number, high Li cation concentration, and high oxidative stability, in addition to the common properties of ionic liquids. The concept of "solvate" ionic liquids can be utilized in an unlimited number of combinations of other metal salts and ligands, and will thus open a new field of research on ionic liquids.

  1. Combined influence of ectoine and salt: spectroscopic and numerical evidence for compensating effects on aqueous solutions.

    PubMed

    Hahn, Marc Benjamin; Uhlig, Frank; Solomun, Tihomir; Smiatek, Jens; Sturm, Heinz

    2016-10-19

    Ectoine is an important osmolyte, which allows microorganisms to survive in extreme environmental salinity. The hygroscopic effects of ectoine in pure water can be explained by a strong water binding behavior whereas a study on the effects of ectoine in salty solution is yet missing. We provide Raman spectroscopic evidence that the influence of ectoine and NaCl are opposing and completely independent of each other. The effect can be explained by the formation of strongly hydrogen-bonded water molecules around ectoine which compensate the influence of the salt on the water dynamics. The mechanism is corroborated by first principles calculations and broadens our understanding of zwitterionic osmolytes in aqueous solution. Our findings allow us to provide a possible explanation for the relatively high osmolyte concentrations in halotolerant bacteria.

  2. Polyelectrolyte-like behaviour of poly(ethylene-oxide) solutions with added monovalent salt

    NASA Astrophysics Data System (ADS)

    Lal, Jyotsana; Hakem, Ilhem-Faiza

    2004-03-01

    Solvent effects on the conformation of poly(ethylene-oxide) (PEO) and complexation of PEO by monovalent cations, have been examined by using small-angle neutron scattering. In methanol and acetonitrile, a big change in interchain interaction, osmotic compressibility and local chain conformation have been observed upon addition of small amounts of potassium iodide. The amplitude of the total intensity decreases significantly and a peak at a certain value of the wavevector q* appears as signature of a polyelectrolyte-like behaviour. With further addition of salt, the ionic strength of the solution increases and potassium binding becomes less favorable: the binding constant decreases with the ionic strength and PEO behaves as a neutral polymer with excluded volume. No association between PEO and potassium iodide was observed in aqueous solutions. Reference: I.F. Hakem and J. Lal. Europhysics letters, 64 (2), 204, 2003

  3. Evaluation of poly (aspartic acid sodium salt) as a draw solute for forward osmosis.

    PubMed

    Gwak, Gimun; Jung, Bokyung; Han, Sungsoo; Hong, Seungkwan

    2015-09-01

    Poly (aspartic acid sodium salt) (PAspNa) was evaluated for its potential as a novel draw solute in forward osmosis (FO). The inherent advantages of PAspNa, such as good water solubility, high osmotic pressure, and nontoxicity, were first examined through a series of physicochemical analyses and atomic-scale molecular dynamics simulations. Then, lab-scale FO tests were performed to evaluate its suitability in practical processes. Compared to other conventional inorganic solutes, PAspNa showed comparable water flux but significantly lower reverse solute flux, demonstrating its suitability as a draw solute. Moreover, fouling experiments using synthetic wastewater as a feed solution demonstrated that PAspNa reversely flowed to the feed side reduced inorganic scaling on the membrane active layer. The recyclability of PAspNa was studied using both nanofiltration (NF) and membrane distillation (MD) processes, and the results exhibited its ease of recovery. This research reported the feasibility and applicability of FO-NF or FO-MD processes using PAspNa for wastewater reclamation and brackish water desalination. Copyright © 2015 Elsevier Ltd. All rights reserved.

  4. Changes in mechanical properties and morphology of elastomer coatings after immersion in salt solutions

    NASA Astrophysics Data System (ADS)

    Terán Arce, Fernando; Avci, Recep; Beech, Iwona; Cooksey, Keith; Wigglesworth-Cooksey, Barbara

    2004-03-01

    RTV11 (^TM GE Silicones) and Intersleek (^TM International Paints) are two elastomers of considerable significance to the navy and maritime industry for their application as fouling release coatings. Both materials are composed of polymeric matrices with embedded filler particles, which provide increased strength and durability to the elastomer. Using Atomic force microscopy (AFM), surface and bulk analysis techniques, we have found surface regions with microelastic properties, which correlate with the locations of filler particles inside the coatings. These particles are able to undergo elastic displacements of hundreds of nm inside the polymeric matrix during compression by the AFM tip. While elastic properties of Intersleek remain largely unchanged after immersion in salt solutions, roughening, embrittlement and stiffening occurs in RTV11 coatings depending on the amount of curing agent and humidity used during preparation and curing, respectively. Interestingly, such transformations are absent after immersion in pure water. In particle free regions, elastic moduli of RTV11 take values of 2 - 3 MPa before immersion in salt solutions. After immersion, those values increase 5 - 10 times.

  5. Comparison of peak shape in hydrophilic interaction chromatography using acidic salt buffers and simple acid solutions.

    PubMed

    Heaton, James C; Russell, Joseph J; Underwood, Tim; Boughtflower, Robert; McCalley, David V

    2014-06-20

    The retention and peak shape of neutral, basic and acidic solutes was studied on hydrophilic interaction chromatography (HILIC) stationary phases that showed both strong and weak ionic retention characteristics, using aqueous-acetonitrile mobile phases containing either formic acid (FA), ammonium formate (AF) or phosphoric acid (PA). The effect of organic solvent concentration on the results was also studied. Peak shape was good for neutrals under most mobile phase conditions. However, peak shapes for ionised solutes, particularly for basic compounds, were considerably worse in FA than AF. Even neutral compounds showed deterioration in performance with FA when the mobile phase water concentration was reduced. The poor performance in FA cannot be entirely attributed to the negative impact of ionic retention on ionised silanols on the underlying silica base materials, as results using PA at lower pH (where their ionisation is suppressed) were inferior to those in AF. Besides the moderating influence of the salt cation on ionic retention, it is likely that salt buffers improve peak shape due to the increased ionic strength of the mobile phase and its impact on the formation of the water layer on the column surface. Copyright © 2014 Elsevier B.V. All rights reserved.

  6. Composite Properties of Polyimide Resins Made From "Salt-Like" Solution Precursors

    NASA Technical Reports Server (NTRS)

    Cano, Roberto J.; Weiser, Erik S.; SaintClair, Terry L.; Echigo, Yoshiaki; Kaneshiro, Hisayasu

    1997-01-01

    Recent work in high temperature materials at NASA Langley Research Center (LaRC (trademark)) have led to the development of new polyimide resin systems with very attractive properties. The majority of the work done with these resin systems has concentrated on determining engineering mechanical properties of composites prepared from a poly(amide acid) precursor. Three NASA Langley-developed polyimide matrix resins, LaRC (trademark) -IA, LaRC (trademark) -IAX, and LaRC (trademark) -8515, were produced via a salt-like process developed by Unitika Ltd. The 'salt-like' solutions (sixty-five percent solids in NMP) were prepregged onto Hexcel IM7 carbon fiber using the NASA LaRC Multipurpose Tape Machine. Process parameters were determined and composite panels fabricated. Mechanical properties are presented for these three intermediate modulus carbon fiber/polyimide matrix composites and compared to existing data on the same polyimide resin systems and IM7 carbon fiber manufactured via poly(amide acid) solutions (thirty-five percent solids in NMP). This work studies the effects of varying the synthetic route on the processing and mechanical properties of polyimide composites.

  7. Observation of salt effects on hydration water of lysozyme in aqueous solution using terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Aoki, Katsuyoshi; Shiraki, Kentaro; Hattori, Toshiaki

    2013-10-01

    Terahertz time-domain spectroscopy was used to investigate the salt effect of ammonium sulfate on the dynamics of hydration water of lysozyme in aqueous solution. The absorption coefficient of lysozyme aqueous solutions containing salt was subtracted by that of the water and ammonium sulfate contained in the lysozyme solution. The results revealed that ammonium sulfate increases the absorption coefficient of the hydration water, which indicates that the dynamics of the hydration water becomes faster and/or the number of hydration water molecules decreases with increasing ammonium sulfate concentration.

  8. Determining the Enthalpy of Vaporization of Salt Solutions Using the Cooling Effect of a Bubble Column Evaporator

    ERIC Educational Resources Information Center

    Fan, Chao; Pashley, Richard M.

    2016-01-01

    The enthalpy of vaporization (?H[subscript vap]) of salt solutions is not easily measured, as a certain quantity of pure water has to be evaporated from a solution, at constant composition, and at a fixed temperature and pressure; then the corresponding heat input has to be measured. However, a simple bubble column evaporator (BCE) was used as a…

  9. Determining the Enthalpy of Vaporization of Salt Solutions Using the Cooling Effect of a Bubble Column Evaporator

    ERIC Educational Resources Information Center

    Fan, Chao; Pashley, Richard M.

    2016-01-01

    The enthalpy of vaporization (?H[subscript vap]) of salt solutions is not easily measured, as a certain quantity of pure water has to be evaporated from a solution, at constant composition, and at a fixed temperature and pressure; then the corresponding heat input has to be measured. However, a simple bubble column evaporator (BCE) was used as a…

  10. Effects of dilute substitutional solutes on interstitial carbon in α-Fe: Interactions and associated carbon diffusion from first-principles calculations

    NASA Astrophysics Data System (ADS)

    Liu, Peitao; Xing, Weiwei; Cheng, Xiyue; Li, Dianzhong; Li, Yiyi; Chen, Xing-Qiu

    2014-07-01

    By means of first-principles calculations coupled with the kinetic Monte Carlo simulations, we have systematically investigated the effects of dilute substitutional solutes on the behaviors of carbon in α-Fe. Our results uncover the following. (i) Without the Fe vacancy the interactions between most solutes and carbon are repulsive due to the strain relief, whereas Mn has a weak attractive interaction with its nearest-neighbor carbon due to the local ferromagnetic coupling effect. (ii) The presence of the Fe vacancy results in attractive interactions of all the solutes with carbon. In particular, the Mn-vacancy pair shows an exceptionally large binding energy of -0.81 eV with carbon. (iii) The alloying addition significantly impacts the atomic-scale concentration distributions and chemical potential of carbon in the Fe matrix. Among them, Mn and Cr increase the carbon chemical potential, whereas Al and Si reduce it. (iv) Within the dilute scale of the alloying solution, the solute concentration- and temperature-dependent carbon diffusivities demonstrate that Mn has a little impact on the carbon diffusion, whereas Cr (Al or Si) remarkably retards the carbon diffusion. Our results provide a certain implication for better understanding the experimental observations related with the carbon solubility limit, carbon microsegregation, and carbide precipitations in the ferritic steels.

  11. Measuring and modeling the salting-out effect in ammonium sulfate solutions.

    PubMed

    Wang, Chen; Lei, Ying Duan; Endo, Satoshi; Wania, Frank

    2014-11-18

    The presence of inorganic salts significantly influences the partitioning behavior of organic compounds between environmentally relevant aqueous phases, such as seawater or aqueous aerosol, and other, nonaqueous phases (gas phase, organic phase, etc.). In this study, salting-out coefficients (or Setschenow constants) (KS [M(-1)]) for 38 diverse neutral compounds in ammonium sulfate ((NH4)2SO4) solutions were measured using a shared headspace passive dosing method and a negligible depletion solid phase microextraction technique. The measured KS were all positive, varied from 0.216 to 0.729, and had standard errors in the range of 0.006-0.060. Compared to KS for sodium chloride (NaCl) in the literature, KS values for (NH4)2SO4 are always higher for the same compound, suggesting a higher salting-out effect of (NH4)2SO4. A polyparameter linear free energy relationship (pp-LFER) for predicting KS in (NH4)2SO4 solutions was generated using the experimental data for calibration. pp-LFER predicted KS agreed well with measured KS reported in the literature. KS for (NH4)2SO4 was also predicted using the quantum-chemical COSMOtherm software and the thermodynamic model AIOMFAC. While COSMOtherm generally overpredicted the experimental KS, predicted and experimental values were correlated. Therefore, a fitting factor needs to be applied when using the current version of COSMOtherm to predict KS. AIOMFAC tends to underpredict the measured KS((NH4)2SO4) but always overpredicts KS(NaCl). The prediction error is generally larger for KS(NaCl) than for KS((NH4)2SO4). AIOMFAC also predicted a dependence of KS on the salt concentrations, which is not observed in the experimental data. In order to demonstrate that the models developed and calibrated in this study can be applied to estimate Setschenow coefficients for atmospherically relevant compounds involved in secondary organic aerosol formation based on chemical structure alone, we predicted and compared KS for selected

  12. Numerical simulation of solute transport in southwestern Salt Lake Valley, Utah

    USGS Publications Warehouse

    Lambert, P.M.

    1996-01-01

    Contaminated ground water characterized by high concentrations of dissolved solids and dissolved sulfate, and in areas, by low pH and elevated concentrations of metals, is present near public-supply wells in the southwestern Salt Lake Valley. To provide State officials and water users with information concerning the potential movement of contaminated ground water to points of withdrawal in the area, an analysis of solute transport using computer models was done by the U.S. Geological Survey in cooperation with the Utah Department of Natural Resources, Division of Water  Rights, and local municipalities and water users.A three-dimensional solute-transport model was developed and couples with an existing ground-water flow model of Salt Lake Valley to simulate the movement of dissolved sulfate in ground water in southwestern Salt Lake Valley. Development and calibration of the transport model focused mainly on sulfate movement down-gradient from the Bingham Creek Reservoirs and the South Jordan evaporation ponds east of the mouth of Bingham Canyon. Estimates of transport parameters were adjusted during a calibration simulation representing conditions during 1965-93. After calibration, the transport model was used to simulate future sulfate movement for 1994-2043.Because of uncertainty in estimated transport-parameter values, three projection transport simulations incorporating a range of probable parameter values were done to evaluate future sulfate movement and changes in sulfate concentrations at selected public-supply wells. These projection simulations produced a possible range of computed transport rates and patterns. In general, the projection simulations indicated movement of the sulfate plume east of the Bingham Creek reservoir toward public-supply wells northeast of the reservoirs and then eastward toward the Jordan River. Ground water with high concentrations of sulfate east of the South Jordan evaporation ponds is simulated as moving west to east under the

  13. Effect of Dilute Apple Juice and Preferred Fluids vs Electrolyte Maintenance Solution on Treatment Failure Among Children With Mild Gastroenteritis: A Randomized Clinical Trial.

    PubMed

    Freedman, Stephen B; Willan, Andrew R; Boutis, Kathy; Schuh, Suzanne

    2016-05-10

    Gastroenteritis is a common pediatric illness. Electrolyte maintenance solution is recommended to treat and prevent dehydration. Its advantage in minimally dehydrated children is unproven. To determine if oral hydration with dilute apple juice/preferred fluids is noninferior to electrolyte maintenance solution in children with mild gastroenteritis. Randomized, single-blind noninferiority trial conducted between the months of October and April during the years 2010 to 2015 in a tertiary care pediatric emergency department in Toronto, Ontario, Canada. Study participants were children aged 6 to 60 months with gastroenteritis and minimal dehydration. Participants were randomly assigned to receive color-matched half-strength apple juice/preferred fluids (n=323) or apple-flavored electrolyte maintenance solution (n=324). Oral rehydration therapy followed institutional protocols. After discharge, the half-strength apple juice/preferred fluids group was administered fluids as desired; the electrolyte maintenance solution group replaced losses with electrolyte maintenance solution. The primary outcome was a composite of treatment failure defined by any of the following occurring within 7 days of enrollment: intravenous rehydration, hospitalization, subsequent unscheduled physician encounter, protracted symptoms, crossover, and 3% or more weight loss or significant dehydration at in-person follow-up. Secondary outcomes included intravenous rehydration, hospitalization, and frequency of diarrhea and vomiting. The noninferiority margin was defined as a difference between groups of 7.5% for the primary outcome and was assessed with a 1-sided α=.025. If noninferiority was established, a 1-sided test for superiority was conducted. Among 647 randomized children (mean age, 28.3 months; 331 boys [51.1%]; 441 (68.2%) without evidence of dehydration), 644 (99.5%) completed follow-up. Children who were administered dilute apple juice experienced treatment failure less often than those

  14. Effect of Protein-Lipid-Salt Interactions on Sodium Availability in the Mouth and Consequent Perception of Saltiness: In Solutions.

    PubMed

    Yucel, Umut; Peterson, Devin G

    2015-09-02

    The influence of protein-sodium interactions on the availability of sodium in the aqueous phase of liquid samples and consequently on the perception of saltiness was investigated. The aqueous effluents of casein and casein emulsion-salt solutions were monitored for sodium availability from a tongue column system. In the aqueous protein-salt solutions, increasing the protein/salt ratio from 1:1 to 5:1 or 10:1 significantly decreased the initial salt concentration in the effluent and resulted in a higher salt concentration in the effluent over time. Sensory analysis was in agreement. Samples with increased protein were rated as having significantly lower initial saltiness and a higher salty aftertaste. However, when casein was formulated as an emulsion, the initial release of sodium in the effluent was enhanced (compared to nonemulsified protein). Increasing the emulsion interfacial area (more hydrophilic segments of the protein were structured into the aqueous phase) resulted in a higher salt concentration in the aqueous phase and greater perceived saltiness intensity. In summary, protein interactions, specifically ionic, were reported as food interactions that influence salt perception and provide a basis to develop higher flavor quality low-sodium food products.

  15. Effect of pH Value on the Electrochemical and Stress Corrosion Cracking Behavior of X70 Pipeline Steel in the Dilute Bicarbonate Solutions

    NASA Astrophysics Data System (ADS)

    Cui, Z. Y.; Liu, Z. Y.; Wang, L. W.; Ma, H. C.; Du, C. W.; Li, X. G.; Wang, X.

    2015-11-01

    In this work, effects of pH value on the electrochemical and stress corrosion cracking (SCC) behavior of X70 pipeline steel in the dilute bicarbonate solutions were investigated using electrochemical measurements, slow strain rate tensile tests and surface analysis techniques. Decrease of the solution pH from 6.8 to 6.0 promotes the anodic dissolution and cathodic reduction simultaneously. Further decrease of the pH value mainly accelerates the cathodic reduction of X70 pipeline steel. As a result, when the solution pH decreases form 6.8 to 5.5, SCC susceptibility decreases because of the enhancement of the anodic dissolution. When the solution pH decreases from 5.5 to 4.0, SCC susceptibility increases gradually because of the acceleration of cathodic reactions.

  16. Water Uptake by Mars Salt Analogs: An Investigation of Stable Aqueous Solutions Using Raman Microscopy

    NASA Astrophysics Data System (ADS)

    Nuding, Danielle L.

    Liquid water processes that may occur on the surface and near-subsurface of Mars have important implications for the present-day water cycle, habitability, and planetary protection policies. The presence of salts on Mars plays a role in surface-atmosphere interactions as salts enhance the soil's ability to retain water. This thesis explores the phase transitions of water upon interaction with Mars relevant salt analogs. Water uptake and loss properties of a single and complex Mars analog are examined using a Raman microscope equipped with an environmental cell. The effect of the hygroscopic salts on bacterial spores was evaluated with a focus on potential terrestrial contamination on outbound spacecraft and its influence on planetary protection concerns. Calcium perchlorate (Ca(ClO4)2) is a highly deliquescent salt that may exist on the surface of present-day Mars. Here, we quantify the deliquescent relative humidity (DRH) and efflorescent relative humidity (ERH) of Ca(ClO4)2 as a function of temperature (223 K to 273 K) to elucidate its behavior on the surface of Mars. Mars relevant temperature and relative humidity (RH) conditions were simulated and deliquescence (solid to aqueous) and efflorescence (aqueous to solid) phase transitions of Ca(ClO4)2 were characterized. Experimental DRH values were compared to a thermodynamic model for three hydration states of Ca(ClO 4)2. Calcium perchlorate was found to supersaturate, with lower ERH values than DRH values. Additionally, we conducted a 17-hour experiment to simulate a subsurface relative humidity and temperature diurnal cycle. This demonstrated that aqueous Ca(ClO4)2 solutions can persist without efflorescing for the majority of a martian sol, up to 17 hours under Mars temperature heating rates and RH conditions. Applying these experimental results to martian surface and subsurface heat and mass transfer models, we find that aqueous Ca(ClO4)2 solutions could persist for most of the martian sol under present

  17. Hydrology of the Bonneville Salt Flats, northwestern Utah, and simulation of ground-water flow and solute transport in the shallow-brine aquifer

    USGS Publications Warehouse

    Mason, James L.; Kipp, Kenneth L.

    1998-01-01

    This report describes the hydrologic system of the Bonneville Salt Flats with emphasis on the mechanisms of solute transport. Variable-density, three-dimensional computer simulations of the near-surface part of the ground-water system were done to quantify both the transport of salt dissolved in subsurface brine that leaves the salt-crust area and the salt dissolved and precipitated on the land surface. The study was designed to define the hydrology of the brine ground-water system and the natural and anthropogenic processes causing salt loss, and where feasible, to quantify these processes. Specific areas of study include the transport of salt in solution by ground-water flow and the transport of salt in solution by wind-driven ponds and the subsequent salt precipitation on the surface of the playa upon evaporation or seepage into the subsurface. In addition, hydraulic and chemical changes in the hydrologic system since previous studies were documented.

  18. Removal of Cu{sup 2+}, Cd{sup 2+} and Mn(VII) from dilute, aqueous solutions by oxidized bituminous coal

    SciTech Connect

    Bodine, D.L.; Doyle, F.M.

    1995-07-01

    The ability of oxidized Upper Freeport bituminous coal to adsorb Cu{sup 2+}, Cd{sup 2+} and MN(VII) from very dilute aqueous solutions has been studied. Low-rank coal is known to adsorb heavy metal ions from dilute, aqueous solutions, probably by ion exchange and/or chelation by acidic functional groups on the coal surface. However, it would be advantageous to use higher rank coals for water treatment. Coal samples were oxidized thermally or by 30% H{sub 2}O{sub 2} to increase the surface concentration of phenolic and carboxylic groups, then portions were shaken with Cu{sup 2+} and Cd{sup 2+} solutions. Acidic KMnO{sub 4} was also used to oxidize coal, with concurrent sorption of the resulting MN(IV) and Mn(II). The effect of oxidation treatment, metal ion concentration, and solution pH on metal uptake kinetics was investigated. Potential applications for treating effluents, especially those containing oxidizing ions, are discussed, along with possible flowsheet options.

  19. Dilution of a mepivacaine-adrenaline solution in isotonic sodium bicarbonate for reducing subcutaneous infiltration pain in ambulatory phlebectomy procedures: a randomized, double-blind, controlled trial.

    PubMed

    Moro, Leo; Serino, Francesco-Maria; Ricci, Stefano; Abbruzzese, Gloria; Antonelli-Incalzi, Raffaele

    2014-11-01

    Varicose veins are treated under local infiltration anesthesia. Literature shows that adding sodium bicarbonate reduces the pain associated with local infiltration anesthesia. Nonetheless, sodium bicarbonate is underused. We sought to assess if the use of a solution of mepivacaine 2% plus adrenaline with sodium bicarbonate 1.4% results in less pain associated with local infiltration anesthesia preceding ambulatory phlebectomies, compared with standard preparation diluted with normal saline. In all, 100 adult patients undergoing scheduled ambulatory phlebectomy were randomized to receive either a solution of mepivacaine chlorhydrate 2% plus adrenaline in sodium bicarbonate 1.4% or a similar solution diluted in normal saline 0.9%. Median pain scores associated with local infiltration anesthesia reported in the intervention and control groups were 2 (SD=1.6) and 5 (SD=2.0) (P<.0001), respectively. A general linear model with bootstrapped confidence intervals showed that using the alkalinized solution would lead to a reduction in pain rating of about 3 points. Patients were not asked to distinguish the pain of the needle stick from the pain of the infiltration. Moreover, a complete clinical study of sensitivity on the infiltrated area was not conducted. Data obtained from this study may contribute to improve local infiltration anesthesia in ambulatory phlebectomy and other phlebologic procedures. Copyright © 2014 American Academy of Dermatology, Inc. Published by Elsevier Inc. All rights reserved.

  20. Growth mechanism of a gas clathrate hydrate from a dilute aqueous gas solution: a molecular dynamics simulation of a three-phase system.

    PubMed

    Nada, Hiroki

    2006-08-24

    A molecular dynamics simulation of a three-phase system including a gas clathrate, liquid water, and a gas was carried out at 298 K and high pressure in order to investigate the growth mechanism of the clathrate from a dilute aqueous gas solution. The simulation indicated that the clathrate grew on interfaces between the clathrate and the liquid water, after transfer of the gas molecules from the gas phase to the interfaces. The results suggest a two-step process for growth: first, gas molecules are arranged at cage sites, and second, H(2)O molecules are ordered near the gas molecules. The results also suggest that only the H(2)O molecules, which are surrounded or sandwiched by the gas molecules, form the stable polygons that constitute the cages of the clathrate. In addition, the growth of the clathrate from a concentrated aqueous gas solution was also simulated, and the results suggested a growth mechanism in which many H(2)O and gas molecules correctively form the structure of the clathrate. The clathrate grown from the concentrated solution contained some empty cages, whereas the formation of empty cages was not observed during the growth from the dilute solution. The results obtained by both simulations are compared with the results of an experimental study, and the growth mechanism of the clathrate in a real system is discussed.

  1. Lysozyme-lysozyme and lysozyme-salt interactions in the aqueous saline solution: a new square-well potential.

    PubMed

    Chang, Bong Ho; Bae, Young Chan

    2003-01-01

    We investigate lysozyme-lysozyme and lysozyme-salt interactions in electrolyte solutions using a molecular-thermodynamic model. An equation of state based on the statistical mechanical perturbation theory is applied to describe the interactions. The perturbation term includes a new square-well potential of mean force, which implies the information about the lysozyme surface and salt type. The attractive energy of the potential of mean force is correlated with experimental cloud-point temperatures of lysozyme in various solution conditions. The same attractive energy is used to predict osmotic pressure of a given system with no additional parameters. The new potential shows a satisfactory improvement in understanding the interactions between lysozymes in aqueous salt solutions.

  2. Hydrogen generation in microbial reverse-electrodialysis electrolysis cells using a heat-regenerated salt solution.

    PubMed

    Nam, Joo-Youn; Cusick, Roland D; Kim, Younggy; Logan, Bruce E

    2012-05-01

    Hydrogen gas can be electrochemically produced in microbial reverse-electrodialysis electrolysis cells (MRECs) using current derived from organic matter and salinity-gradient energy such as river water and seawater solutions. Here, it is shown that ammonium bicarbonate salts, which can be regenerated using low-temperature waste heat, can also produce sufficient voltage for hydrogen gas generation in an MREC. The maximum hydrogen production rate was 1.6 m(3) H(2)/m(3)·d, with a hydrogen yield of 3.4 mol H(2)/mol acetate at a salinity ratio of infinite. Energy recovery was 10% based on total energy applied with an energy efficiency of 22% based on the consumed energy in the reactor. The cathode overpotential was dependent on the catholyte (sodium bicarbonate) concentration, but not the salinity ratio, indicating high catholyte conductivity was essential for maximizing hydrogen production rates. The direction of the HC and LC flows (co- or counter-current) did not affect performance in terms of hydrogen gas volume, production rates, or stack voltages. These results show that the MREC can be successfully operated using ammonium bicarbonate salts that can be regenerated using conventional distillation technologies and waste heat making the MREC a useful method for hydrogen gas production from wastes.

  3. Isolation and characterization of coagulant extracted from Moringa oleifera seed by salt solution.

    PubMed

    Okuda, T; Baes, A U; Nishijima, W; Okada, M

    2001-02-01

    It is known that M. oleifera contains a natural coagulant in the seeds. In our previous research, the method using salt water to extract the active coagulation component from M. oleifera seeds was developed and compared with the conventional method using water. In this research, the active coagulation component was purified from a NaCl solution crude extract of Moringa oleifera seeds. The active component was isolated and purified from the crude extract through a sequence of steps that included salting-out by dialysis, removal of lipids and carbohydrates by homogenization with acetone, and anion exchange. Specific coagulation activity of the active material increased up to 34 times more than the crude extract after the ion exchange. The active component was not the same as that of water extract. The molecular weight was about 3000 Da. The Lowry method and the phenol-sulfuric acid method indicated that the active component was neither protein nor polysaccharide. The optimum pH of the purified active component for coagulation of turbidity was pH 8 and above. Different from the conventional water extracts, the active component can be used for waters with low turbidity without increase in the dissolved organic carbon concentration.

  4. Stabilizing Superionic-Conducting Structures via Mixed-Anion Solid Solutions of Monocarba- closo -borate Salts

    DOE PAGES

    Tang, Wan Si; Yoshida, Koji; Soloninin, Alexei V.; ...

    2016-09-01

    Solid lithium and sodium closo-polyborate-based salts are capable of superionic conductivities surpassing even liquid electrolytes, but often only at above-ambient temperatures where their entropically driven disordered phases become stabilized. Here we show by X-ray diffraction, quasielastic neutron scattering, differential scanning calorimetry, NMR, and AC impedance measurements that by introducing 'geometric frustration' via the mixing of two different closo-polyborate anions, namely, 1-CB9H10- and CB11H12-, to form solid-solution anion-alloy salts of lithium or sodium, we can successfully suppress the formation of possible ordered phases in favor of disordered, fast-ion-conducting alloy phases over a broad temperature range from subambient to high temperatures. Finally,more » this result exemplifies an important advancement for further improving on the remarkable conductive properties generally displayed by this class of materials and represents a practical strategy for creating tailored, ambient-temperature, solid, superionic conductors for a variety of upcoming all-solid-state energy devices of the future.« less

  5. Self-organization of poly(ethylene oxide) on the surface of aqueous salt solutions.

    PubMed

    Fuchs, Christian; Hussain, Hazrat; Amado, Elkin; Busse, Karsten; Kressler, Joerg

    2015-01-01

    It is demonstrated that stable Langmuir films of poly(ethylene oxide) (PEO) can be formed up to surface pressures of 30 mN m(-1) when potassium carbonate K2CO3 is added to the aqueous subphase. Generally, PEO homopolymer cannot stay on the water surface at a surface pressure ≥10 mN m(-1) due to its high water solubility. To prepare stable monolayer films, PEO can be modified with hydrophobic moieties. However, by exploiting the salting out effect by adding certain salts (K2CO3 or MgSO4) into the aqueous subphase, not only very stable films but also unusual self-organization can be achieved by the PEO homopolymer on the surface of the aqueous solution. Thus, a series of OH-terminated PEOs is found to form a stable monolayer at K2CO3 concentrations of 2 M and above in the aqueous subphase, and the stability of the film increases with an increase in K2CO3 concentration. Hysteresis experiments are also carried out. During the phase transition induced by progressive compression, self-organization into well-defined domains with sizes in the micrometer range are observed, and with further compression and holding of the film for 30 min and above the microdomains transform into a crystalline morphology as visualized by Brewster angle microscopy. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Results for the Fourth Quarter Calendar Year 2015 Tank 50H Salt Solution Sample

    SciTech Connect

    Crawford, C.

    2016-01-11

    In this memorandum, the chemical and radionuclide contaminant results from the Fourth Quarter Calendar Year 2015 (CY15) sample of Tank 50H salt solution are presented in tabulated form. The Fourth Quarter CY15 Tank 50H samples were obtained on October 29, 2015 and received at Savannah River National Laboratory (SRNL) on October 30, 2015. The information from this characterization will be used by Defense Waste Processing Facility (DWPF) & Saltstone Facility Engineering for the transfer of aqueous waste from Tank 50H to the Salt Feed Tank in the Saltstone Production Facility, where the waste will be treated and disposed of in the Saltstone Disposal Facility. This memorandum compares results, where applicable, to Saltstone Waste Acceptance Criteria (WAC) limits and targets. Data pertaining to the regulatory limits for Resource Conservation and Recovery Act (RCRA) metals will be documented at a later time per the Task Technical and Quality Assurance Plan (TTQAP) for the Tank 50H saltstone task. The chemical and radionuclide contaminant results from the characterization of the Fourth Quarter Calendar Year 2015 (CY15) sampling of Tank 50H were requested by SRR personnel and details of the testing are presented in the SRNL Task Technical and Quality Assurance Plan.

  7. Electron spin resonance of diluted solid solutions of Gd{sub 2}O{sub 3} in CeO{sub 2}

    SciTech Connect

    Biasi, R.S. de . E-mail: rsbiasi@ime.eb.br; Grillo, M.L.N. . E-mail: mluciag@uerj.br

    2005-06-15

    Electron spin resonance spectra of Gd{sup 3+} in diluted solid solutions of Gd{sub 2}O{sub 3} in CeO{sub 2} have been studied at room temperature for Gd concentrations between 0.01 and 1.00mol%. While in the case of Mn{sup 2+}:CeO{sub 2} samples, both the linewidth and the line intensity go through a maximum between 0.2 and 0.4% Mn and then start to decrease, in the case of Gd{sup 3+}:CeO{sub 2} samples the linewidth and the line intensity increase monotonically with the dopant concentration. This as taken as evidence that in Gd{sub 2}O{sub 3}-CeO{sub 2} diluted solid solutions there are no clustering effects similar to the ones observed in Mn:CeO{sub 2} solid solutions. It is not clear why clustering effects are present in Mn:CeO{sub 2} solid solutions and not in Gd:CeO{sub 2} solid solutions; however, it seems reasonable to assume that this is due to the fact that the ionic radius of Mn{sup 2+} (81 pm) is about 25% smaller that that of Gd{sup 3+} (107.8pm). In any case, the fact that Gd:CeO{sub 2} solid solutions do not exhibit clustering effects means that ESR linewidth data can be used to estimate the concentration of Gd in CeO{sub 2} samples, as it is possible to do in several solid solutions of paramagnetic ions in ceramic materials. The results also suggest that the range of the exchange interaction between Gd{sup 3+} ions in CeO{sub 2} is about 0.89nm.

  8. Effectiveness of oral rehydration salt solution (ORS) in reduction of death during cholera epidemic.

    PubMed

    Sircar, B K; Saha, M R; Deb, B C; Singh, P K; Pal, S C

    1990-01-01

    An extensive outbreak of acute gastroenteritis involving all age group of patients occurred during July-September, 1978 in the Central district of Manipur state. A total of 4469 cases occurred during the period. 45.7% of diarrhoea cases sampled and 47.6% of water samples collected from rivers were found to be positive for V.cholerae biotype EITor. Case fatality rate in this epidemic was exceptionally low (0.8%) which was attributed to the early domiciliary use of oral rehydration salt solution (ORS) in the affected villages. Utility of ORS in drastic reduction of case fatality rate during any epidemic situation was first of its kind in the Indian scene.

  9. Synthesis, Solution, and Structural Characterization of Tetrahydrofuranyl-2,2-Bisphosphonic Acid Disodium Salt

    PubMed Central

    Maltezou, Elena; Stylianou, Marios; Roy, Sudeshna; Drouza, Chryssoula; Keramidas, Anastasios D.

    2010-01-01

    Bisphosphonates are biologically relevant therapeutics for bone disorders and cancer. Reaction of γ-chlorobutyric acid, phosphorus acid, and phosphorus trichloride without the use of solvent gave the tetrahydrofuranyl-2,2-bisphosphonate sodium salt (Na2H2L). The Na2H2L was isolated, characterized in solution by 1H, 13C, and 31P NMR spectroscopy and in solid state by single X-Ray crystallography. The crystal structure showed that the Na2H2L forms in the crystal infinite two-dimensional sheets stacked one parallel to the other. A comparison of the chelating properties of H2L2− with similar hydroxyl bisphosphonate ligands shows that the strength of the Na–O(furanyl/hydroxyl) bond is directly related to the total charge of the ligand anion. PMID:20467558

  10. Electrophysical methods of separation of metal cations in the moving salts solution

    NASA Astrophysics Data System (ADS)

    Gofman, V. N.; Tuksov, I. V.; Timchenko, S. N.; Shamanin, I. V.; Poberezhnikov, A. D.; Kazaryan, M. A.

    2016-07-01

    The results of experiments on the excitation of the phenomenon of selective drift of solvated ions under the influence of an external "asymmetric" electric field to the circulating solution of calcium chloride and magnesium salts in a polar liquid dielectric - water are shown. The purpose of the experiments was to determine the influence of the field frequency and amplitude of the field strength on the excitation phenomenon, and the study of the operating characteristics of the testing apparatus - a dividing cell. The dependences of the separation efficiency of solvated cations from the frequency of the external field and the excitation threshold of the phenomenon from the field strength in the separation cell are defined.

  11. Microwave irradiation affects ion pairing in aqueous solutions of alkali halide salts

    NASA Astrophysics Data System (ADS)

    Mohorič, Tomaž; Bren, Urban

    2017-01-01

    Using the molecular dynamics simulations with separate thermostats for translational and rotational degrees of freedom, we investigate the effects of water's rotational motion on the ion pairing of ionic solutes in aqueous solutions. The situation with rotational temperature higher than the translational one, Trot>Ttrs , is mimicking the non-equilibrium effects of microwaves on model solutions of alkali halide salts. The simulations reveal that an increase in the rotational temperature at constant translational temperature exerts significant changes in the structure of the solution. The latter are reflected in increased pairing of the oppositely charged ions, which can be explained by the weaker ability of rotationally excited water to screen and separate the opposite charges. It seems that Collins' law of matching water affinities retains its validity also in the non-equilibrium situation where the rotational temperature exceeds the translational one. On the other hand, the equilibrium effect (i.e., an increase in the solution's overall temperature T ≡Trot = Ttrs) favors the formation of small-small (NaCl), while it has a little effect on large-large (CsI) ion pairs. This is in accordance with water becoming less polar solvent upon a temperature increase. Furthermore, we investigated the effects of excited translational motion of water (and ions) on the ion pairing by increasing the translational temperature, while keeping the rotational one unchanged (i.e., Ttrs>Trot ). Interestingly, in certain cases the faster translational motion causes an increase in correlations. The temperature variations in the like-ion association constants, Kas++ and Kas-, are also examined. Here the situation is more complex but, in most cases, a decrease in the ion pairing is observed.

  12. Additional disinfection with a modified salt solution in a root canal model.

    PubMed

    van der Waal, Suzette V; Oonk, Charlotte A M; Nieman, Selma H; Wesselink, Paul R; de Soet, Johannes J; Crielaard, Wim

    2015-10-01

    The aim of this study is to investigate the disinfecting properties of a modified salt solution (MSS) and calcium hydroxide (Ca(OH)2) in a non-direct-contact ex-vivo model. Seventy-four single-canal roots infected with Enterococcus faecalis were treated with 1% sodium hypochlorite (NaOCl) irrigation or with NaOCl irrigation with subsequent dressing with MSS or Ca(OH)2. After removal of the dressings, the roots were filled with bacterial growth medium and incubated for seven days to enable the surviving bacteria to repopulate the root canal lumen. Growth was determined by sampling the root canals with paper points before treatment (S1), after treatment (S2) and incubation after treatment (S3). The colony forming units were counted at S1 and S2. At S3, growth was determined as no/yes regrowth. The Kruskal-Wallis, McNemar and χ(2) test were used for statistical analyses. At S2, in the NaOCl group, growth was found in 5 of 19 root canals. After the removal of MSS or Ca(OH)2 bacteria were retrieved from one root canal in both groups. At S3, repopulation of the root canals had occurred in 14 of 19 roots after sole NaOCl irrigation, 6 of 20 roots after MSS-dressing and in 14 of 20 roots after Ca(OH)2-dressing. MSS was more effective in preventing regrowth than Ca(OH)2 (P=0.009). The modified salt solution prevented regrowth in roots which indicates that it can eliminate persistent bacteria. Dressing the root canals with Ca(OH)2 did not provide additional disinfection after NaOCl irrigation. Copyright © 2015 Elsevier Ltd. All rights reserved.

  13. Mechanical Behavior of Salt Caverns: Closed-Form Solutions vs Numerical Computations

    NASA Astrophysics Data System (ADS)

    Wang, Linlin; Bérest, Pierre; Brouard, Benoît

    2015-11-01

    Creep closure and structural stability of a cylindrical elongated cavern leached out from a salt formation are discussed. The Norton-Hoff creep law, or "power law", is used to capture the main features of salt rheological behavior. Two failure criteria are considered: (1) shear stresses must not be larger than a certain fraction of the mean stress (dilation criterion); and (2) the effective stress at the cavern wall (actual stress plus cavern fluid pressure) must not be tensile. The case of a brine-filled cavern whose pressure is kept constant is discussed first. It is proved that creep closure reaches a steady state such that stresses in the rock mass remain constant. However, decades are needed to reach such a state. During the transient phase that results from the slow redistribution of stresses in the rock mass, deviatoric stresses decrease at the vicinity of the cavern wall, and onset of dilation is less and less likely. At this point, the case of a rapid brine pressure increase, typical of a tightness test, is considered. It is proved that during such a swift pressure increase, cavern behavior is almost perfectly elastic; there is no risk of dilation onset. However, even when cavern pressure remains significantly smaller than geostatic, the effective stress at cavern wall can become tensile. These results, obtained through numerical computations, are confirmed by closed-form solutions obtained in the case of an idealized perfectly cylindrical cavern; these solutions provide a better insight into the main structural features of the behavior of the cavern.

  14. Complex electronic waste treatment - An effective process to selectively recover copper with solutions containing different ammonium salts.

    PubMed

    Sun, Z H I; Xiao, Y; Sietsma, J; Agterhuis, H; Yang, Y

    2016-11-01

    Recovery of valuable metals from electronic waste has been highlighted by the EU directives. The difficulties for recycling are induced by the high complexity of such waste. In this research, copper could be selectively recovered using an ammonia-based process, from industrially processed information and communication technology (ICT) waste with high complexity. A detailed understanding on the role of ammonium salt was focused during both stages of leaching copper into a solution and the subsequent step for copper recovery from the solution. By comparing the reactivity of the leaching solution with different ammonium salts, their physiochemical behaviour as well as the leaching efficiency could be identified. The copper recovery rate could reach 95% with ammonium carbonate as the leaching salt. In the stage of copper recovery from the solution, electrodeposition was introduced without an additional solvent extraction step and the electrochemical behaviour of the solution was figured out. With a careful control of the electrodeposition conditions, the current efficiency could be improved to be 80-90% depending on the ammonia salts and high purity copper (99.9wt.%). This research provides basis for improving the recyclability and efficiency of copper recovery from such electronic waste and the whole process design for copper recycling. Copyright © 2016 Elsevier Ltd. All rights reserved.

  15. Release of gaseous bromine from the photolysis of nitrate and hydrogen peroxide in simulated sea-salt solutions

    NASA Astrophysics Data System (ADS)

    George, Ingrid J.; Anastasio, Cort

    We have carried out a series of laboratory experiments to investigate the oxidation of bromide (Br -) by hydroxyl radical ( rad OH) in solutions used to mimic sea-salt particles. Aqueous halide solutions with nitrate or hydrogen peroxide (HOOH) as a photochemical source of rad OH were illuminated with 313 nm light and the resulting gaseous bromine (Br*(g)) was collected. While illumination of these solutions nearly always formed gaseous bromine (predominantly Br 2 based on modeling results), there was no evidence for the release of gaseous chlorine. The rate of Br*(g) release increased (up to a plateau value) with increasing concentrations of bromide and was enhanced at lower pH values for both nitrate and HOOH solutions. Increased ionic strength in nitrate solutions inhibited Br*(g) release and the extent of inhibition was dependent upon the salt used. In HOOH solutions, however, no ionic strength effects were observed and the presence of Cl - strongly enhanced Br*(g) release. Overall, for conditions typical of aged, deliquesced, sea-salt particles, the efficiencies of gaseous bromine release, expressed as mole of Br*(g) released per mole of rad OH photochemically formed, were typically 20-30%. Using these reaction efficiencies, we calculated the Br 2(g) release rate from aged, ambient sea-salt particles due to rad OH oxidation to be approximately 0.07 pptv h -1 with the main contributions from nitrate photolysis and partitioning of gas-phase rad OH into the particle. While our solution conditions are simplified compared to ambient particles, this estimated rate of Br 2 release is high enough to suggest that rad OH-mediated reactions in sea-salt particles could be a significant source of reactive bromine to the marine boundary layer.

  16. Excellent dynamic stability under saturated salt solution for aqueous quantum dots capped by multi-branched ligands

    NASA Astrophysics Data System (ADS)

    Xu, Jingkun; Xu, Shuhong; Lv, Changgui; Wang, Chunlei; Cui, Yiping

    2016-09-01

    Preparing quantum dots (QDs) with strong stability against salts is extremely important in some environments with ultrahigh salts concentration, such as the oil exploitation, wastewater treatment and biological markers. In this paper, we reported a simple new method to prepared highly stable QDs by using multi-branched ligands. Our results suggested that multi-branched ligands-capped QDs have extremely good dynamic stability even in salt-saturated solution. Unlike to traditional dynamic stability theory, which considers the electrostatic repulsion of QDs dominant QD stability, the current work found a new determined factor: the steric hindrance of ligand structure. The high steric hindrance effect of multi-branched ligands can maintain the single dispersity of QDs even at extremely low electrostatic repulsion. As a result, QDs with ultrahigh stability against salts can be realized.

  17. Impact of pressure, salt concentration, and temperature on the convective dissolution of carbon dioxide in aqueous solutions.

    PubMed

    Loodts, V; Rongy, L; De Wit, A

    2014-12-01

    The convective dissolution of carbon dioxide (CO2) in salted water is theoretically studied to determine how parameters such as CO2 pressure, salt concentration, and temperature impact the short-time characteristics of the buoyancy-driven instability. On the basis of a parameter-free dimensionless model, we perform a linear stability analysis of the time-dependent concentration profiles of CO2 diffusing into the aqueous solution. We explicit the procedure to transform the predicted dimensionless growth rate and wavelength of the convective pattern into dimensional ones for typical laboratory-scale experiments in conditions close to room temperature and atmospheric pressure. This allows to investigate the implicit influence of the experimental parameters on the characteristic length and time scales of the instability. We predict that increasing CO2 pressure, or decreasing salt concentration or temperature destabilizes the system with regard to convection, leading to a faster dissolution of CO2 into salted water.

  18. Numerical Simulation of the Freeze-Thaw Behavior of Mortar Containing Deicing Salt Solution.

    PubMed

    Esmaeeli, Hadi S; Farnam, Yaghoob; Bentz, Dale P; Zavattieri, Pablo D; Weiss, Jason

    2017-02-01

    This paper presents a one-dimensional finite difference model that is developed to describe the freeze-thaw behavior of an air-entrained mortar containing deicing salt solution. A phenomenological model is used to predict the temperature and the heat flow for mortar specimens during cooling and heating. Phase transformations associated with the freezing/melting of water/ice or transition of the eutectic solution from liquid to solid are included in this phenomenological model. The lever rule is used to calculate the quantity of solution that undergoes the phase transformation, thereby simulating the energy released/absorbed during phase transformation. Undercooling and pore size effects are considered in the numerical model. To investigate the effect of pore size distribution, this distribution is considered using the Gibbs-Thomson equation in a saturated mortar specimen. For an air-entrained mortar, the impact of considering pore size (and curvature) on freezing was relatively insignificant; however the impact of pore size is much more significant during melting. The fluid inside pores smaller than 5 nm (i.e., gel pores) has a relatively small contribution in the macroscopic freeze-thaw behavior of mortar specimens within the temperature range used in this study (i.e., +24 °C to -35 °C), and can therefore be neglected for the macroscopic freeze-thaw simulations. A heat sink term is utilized to simulate the heat dissipation during phase transformations. Data from experiments performed using a low-temperature longitudinal guarded comparative calorimeter (LGCC) on mortar specimens fully saturated with various concentration NaCl solutions or partially saturated with water is compared to the numerical results and a promising agreement is generally obtained.

  19. Reduction of earth alkaline metal salts in THF solution studied by picosecond pulse radiolysis.

    PubMed

    Ma, Jun; Archirel, Pierre; Schmidhammer, Uli; Teuler, Jean-Marie; Pernot, Pascal; Mostafavi, Mehran

    2013-12-27

    Picosecond pulse radiolysis of tetrahydrofuran (THF) solutions containing earth alkaline metal salt, M(II)(ClO4)2, at different concentrations are performed using two different supercontinua as probe pulse, one covering the visible and another the near-infrared (NIR) down to the visible. Two types of line scan detectors are used to record the absorption spectra in the range from 400 to 1500 nm. Because of the strong overlap between the spectra of the absorbing species in the present wavelength range, global matrices were built for each M(II) system, by delay-wise binding the matrix for pure THF with the available matrices for this cation. The number of absorbers was assessed by Singular Value Decomposition of the global matrix, and a MCR-ALS analysis with the corresponding number of species was performed. The analysis of the results show clearly that solvated electron reacts with the earth alkaline metal molecule and the product has an optical absorption band very different than that of solvated electron in pure THF. So, contrarily to the case of solution containing free Na(+), in the presence of Mg(II), Ca(II) and Sr(II) the observed absorption band is not only blueshifted, but its shape is also drastically changed. In fact with Na(+) solvated electron forms a tight-contact pair but with earth alkaline metal cation solvated electron is scavenged by the undissociated molecule M(II)(ClO4)2. In order to determine the structure of the absorbing species observed after the electron pulse, Monte Carlo/DFT simulations were performed in the case of Mg(II), based on a classical Monte Carlo code and DFT/PCM calculation of the solute. The UV-visible spectrum of the solute is calculated with the help of the TDDFT method. The calculated spectrum is close to the experimental one. It is due to two species, a contact pair and an anion.

  20. Preparation of Some Homologous TEMPO Nitroxides and Oxoammonium Salts; Notes on the NMR Spectroscopy of Nitroxide Free Radicals; Observed Radical Nature of Oxoammonium Salt Solutions Containing Trace Amounts of Corresponding Nitroxides in an Equilibrium Relationship.

    PubMed

    Bobbitt, James M; Eddy, Nicholas A; Cady, Clyde X; Jin, Jing; Gascon, Jose A; Gelpí-Dominguez, Svetlana; Zakrzewski, Jerzy; Morton, Martha D

    2017-09-06

    Three new homologous TEMPO oxoammonium salts and three homologous nitroxide radicals have been prepared and characterized. The oxidation properties of the salts have been explored. The direct (13)C NMR and EPR spectra of the nitroxide free radicals and the oxoammonium salts, along with TEMPO and its oxoammonium salt, have been successfully measured with little peak broadening of the NMR signals. In the spectra of all ten compounds (nitroxides and corresponding oxoammonium salts), the carbons in the 2,2,6,6-tetramethylpiperidine core do not appear, implying paramagnetic properties. This unpredicted overall paramagnetism in the oxoammonium salt solutions is explained by a redox equilibrium as shown between oxoammonium salts and trace amounts of corresponding nitroxide. This equilibrium is confirmed by electron interchange reactions between nitroxides with an N-acetyl substituent and oxoammonium salts with longer acyl side chains.