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Sample records for suspension ionic strength

  1. Influence of ionic strength on the viscosities and water loss of bentonite suspensions containing polymers

    Directory of Open Access Journals (Sweden)

    Luciana Viana Amorim

    2007-03-01

    Full Text Available A study was made of the influence of ionic strength (S on the apparent (AV and plastic (PV viscosities and water loss (WL of sodium bentonite suspension with polymers. Na-bentonite was dispersed in water (4.86% w/w of different ionic strengths (S = 0.0, 0.015, 0.030 and 0.045 M followed by the addition of polymer. Three polymer samples were studied, i.e., low viscosity carboxymethyl cellulose (CMC BV, polyanionic cellulose (PAC, and partially hydrolyzed polyacrylamide (HPAM. The results indicated that the presence of salts and increased salinity greatly influence the apparent and plastic viscosities and water loss of bentonite suspensions with polymer.

  2. Dialysis buffer with different ionic strength affects the antigenicity of cultured nervous necrosis virus (NNV) suspensions.

    Science.gov (United States)

    Gye, Hyun Jung; Nishizawa, Toyohiko

    2016-09-02

    Nervous necrosis virus (NNV) belongs to the genus Betanodavirus (Nodaviridae). It is highly pathogenic to various marine fishes. Here, we investigated the antigenicity changes of cultured NNV suspensions during 14days of dialyses using a dialysis tube at 1.4×10(4) molecular weight cut off (MWCO) in three different buffers (Dulbecco's phosphate buffered saline (D-PBS), 15mM Tris-HCl (pH 8.0), and deionized water (DIW)). Total NNV antigen titers of cultured NNV suspension varied depending on different dialysis buffers. For example, total NNV antigen titer during D-PBS dialysis was increased once but then decreased. During Tris-HCl dialysis, it was relatively stable. During dialysis in DIW, total NNV antigen titer was increased gradually. These antigenicity changes in NNV suspension might be due to changes in the aggregation state of NNV particles and/or coat proteins (CPs). ELISA values of NNV suspension changed due to changing aggregates state of NNV antigens. NNV particles in suspension were aggregated at a certain level. These aggregates were progressive after D-PBS dialysis, but regressive after Tris-HCl dialysis. The purified NNV particles self-aggregated after dialysis in D-PBS or in Tris-HCl containing 600mM NaCl, but not after dialysis in Tris-HCl or DIW. Quantitative analysis is merited to determine NNV antigens in the highly purified NNV particles suspended in buffer at low salt condition. Copyright © 2016 Elsevier B.V. All rights reserved.

  3. CADDIS Volume 2. Sources, Stressors and Responses: Ionic Strength - Simple Conceptual Diagram

    Science.gov (United States)

    Introduction to the ionic strength module, when to list ionic strength as a candidate cause, ways to measure ionic strength, simple and detailed conceptual diagrams for ionic strength, ionic strength module references and literature reviews.

  4. CADDIS Volume 2. Sources, Stressors and Responses: Ionic Strength - Detailed Conceptual Diagram

    Science.gov (United States)

    Introduction to the ionic strength module, when to list ionic strength as a candidate cause, ways to measure ionic strength, simple and detailed conceptual diagrams for ionic strength, ionic strength module references and literature reviews.

  5. HIGH IONIC STRENGTH OR PRESENCE OF INOSITOL ...

    African Journals Online (AJOL)

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    has all the characteristics associated with the reaction of CysF9(93)β, a sulphydryl group that is invariant in all mammalian haemoglobins. The slow kinetic phase is assigned to CysH3(125)β. Quantitative analysis of the pH dependence of kapp for this phase at 50 mM ionic strength gave an unusually low pKa of 6.0 for this ...

  6. HIGH IONIC STRENGTH OR PRESENCE OF INOSITOL ...

    African Journals Online (AJOL)

    Preferred Customer

    dependence of kapp for this phase at 50 mM ionic strength gave an unusually low pKa of 6.0 for this sulphydryl group. Published data on guinea pig haemoglobin show that it has a much-enhanced acid Bohr effect compared to human haemoglobin. This indicates that CysH3(125)β functions as an acid Bohr group in guinea ...

  7. Deposition kinetics of colloidal particles at high ionic strengths

    Science.gov (United States)

    Cejas, Cesare; Monti, Fabrice; Truchet, Marine; Burnouf, Jean-Pierre; Tabeling, Patrick

    Using microfluidic experiments, we describe the deposition of a fluid suspension of weakly brownian particles transported in a straight channel at small Reynolds numbers under conditions of high ionic strengths. Our studies fall in a regime where electrostatic interactions are neglected and particle-wall van der Waals interactions govern the deposition mechanism on channel walls. We calculate the deposition kinetics analytically for a wide range of physical parameters. We find that the theory agrees with numerical Langevin simulations, which both confirm the experimental results. From this analysis, we demonstrate a universal dimensionless deposition function described by contributions from advection-diffusion transport and adhesion interactions (Hamaker constant). Results show that we accurately confirm the theoretical expression for the deposition kinetics. From a surface science perspective, working in the van der Waals regime enables to measure the Hamaker constant, a task that would take much longer to perform with the standard AFM. Funding from Sanofi Recherche and ESPCI.

  8. Investigation of the Sedimentation Behavior of Aluminum Phosphate: Influence of pH, Ionic Strength, and Model Antigens.

    Science.gov (United States)

    Muthurania, Kevin; Ignatius, Arun Alphonse; Jin, Zhaowei; Williams, Jennifer; Ohtake, Satoshi

    2015-11-01

    Evaluation of the physical characteristics of vaccines formulated in the presence of adjuvants, such as aluminum salts (Alum), is an important step in the development of vaccines. Depending on the formulation conditions and the associated electrostatic interactions of the adjuvant particles, the vaccine suspension may transition between flocculated and deflocculated states. The impact of practical formulation parameters, including pH, ionic strength, and the presence of model antigens, has been correlated to the sedimentation behavior of aluminum phosphate suspensions. A novel approach for the characterization of suspension properties of Alum has been developed to predict the flocculated state of the system using a sedimentation analysis-based tool (Turbiscan®). Two sedimentation parameters, the settling onset time (Sonset) and the sedimentation volume ratio (SVR) can be determined simultaneously in a single measurement. The results demonstrate the suspension characteristics to be significantly altered by solution conditions (pH and ionic strength) and the charge state of bound antigens. Formulation conditions that promote the flocculated state of the suspension are characterized by faster Sonset and higher SVR, and are generally easy to resuspend. The Turbiscan® method described herein is a useful tool for the characterization of aluminum-containing suspensions and may be adapted for screening and optimization of suspension-based vaccine formulations in general. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.

  9. Ion exchange on mixed ionic forms of montmorillonite at high ionic strengths

    Energy Technology Data Exchange (ETDEWEB)

    Rogers, W. J.; Shiao, S. Y.; Meyer, R. E.; Westmoreland, C. G.; Lietzke, M. H.

    1979-01-01

    This paper summarizes studies of the distribution of sodium and calcium ions between a common clay, montmorillonite, as well as several other clays, and a series of solutions of constant total ionic strength (I) with varying ionic strength fraction of sodium. Distribution coefficients D for Na(I) and Ca(II) were determined by batch equilibrations using isotope dilutions with radioactive tracers. Equilibrium quotients (K/GAMMA) for the exchange of sodium and calcium were then calculated and the effects of solution composition, of solution phase activity coefficients, of ionic strength, of degree of purification, and of source of clay were investigated. Equilibrium quotients with adjustment for solution-phase activity coefficients did not vary greatly with I, except at low loading of sodium on the calcium form of montmorillonite, where D/sub Na/ became anomalously high. Values of K/GAMMA for illite and attapulgite were within an order of magnitude of those for montmorillonite.

  10. Behavior of colloidal gold nanoparticles in different ionic strength media

    Science.gov (United States)

    Barreto, Ângela; Luis, Luis G.; Girão, Ana V.; Trindade, Tito; Soares, Amadeu M. V. M.; Oliveira, Miguel

    2015-12-01

    The increased applications of engineered nanoparticles (NPs) may lead to environmental release and transport to estuarine environments where NPs are expected to aggregate/agglomerate with increasing ionic strength. However, more stable NPs that may be resistant to high ionic strength media and more dispersed in the aquatic environment are being synthesized. Thus, understanding colloidal NPs' behavior in different ionic strength media is crucial for the assessment of the consequences of their environmental release. This work assessed the behavior of gold nanoparticles (AuNPs), with diverse sizes and coatings, in media with different ionic strengths (from biological buffers to artificial seawater). Overall, in biological buffers and artificial seawater, citrate-coated AuNPs were unstable, displaying significantly increased sizes (between 100 and 400 nm), whereas no significant alterations (less than 5 % oscillation) were found for AuNPs with other coatings (bovine serum albumin, polyvinylpyrrolidone, and polyethylene glycol). Data suggest that coated AuNPs, and probably other NPs, may be dispersed in the environment from freshwater to estuarine systems.

  11. Synergies of media surface roughness and ionic strength on particle deposition during filtration.

    Science.gov (United States)

    Jin, Chao; Zhao, Weigao; Normani, Stefano D; Zhao, Peng; Emelko, Monica B

    2017-05-01

    Although it is widely believed that media/collector roughness can enhance particle deposition on surfaces, this effect has not been consistently observed nor systematically described. Here, column tests were conducted to: 1) evaluate media roughness impacts on particle deposition in the presence of an energy barrier (i.e., at low ionic strength conditions), and 2) describe the concurrent impacts of collector surface roughness and suspension fluid ionic strength on particle deposition in packed beds. This work presents a first, systematic demonstration that media/collector surface roughness consistently influences particle deposition in a non-linear, non-monotonic manner, irrespective of the presence of an energy barrier. Notably, ionic strength-associated changes in DLVO interaction energy could not solely explain observed differences in particle deposition associated with collector surface roughness. Particle-to-roughness element and particle-to-smooth/bottom surface interactions contributed to a critical roughness size associated with a minimum DLVO interaction energy; however, that critical size is not necessarily the same as the critical size associated with minimal particle deposition rates. Surface roughness and ionic strength concurrently affected particle deposition in a manner that is not simply additive; rather, particle deposition rates were highly correlated with inverse Debye-Hückel length (i.e., ln [κ-1]) using second-order polynomial functions. Notably, the secondary energy minimum alone appears inadequate for explaining the observed particle deposition behavior. These relationships may provide insight for further development of physico-chemical filtration models for describing particle deposition on surfaces. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Photonic crystal carbohydrate sensors: low ionic strength sugar sensing.

    Science.gov (United States)

    Asher, Sanford A; Alexeev, Vladimir L; Goponenko, Alexander V; Sharma, Anjal C; Lednev, Igor K; Wilcox, Craig S; Finegold, David N

    2003-03-19

    We developed a carbohydrate sensing material, which consists of a crystalline colloidal array (CCA) incorporated into a polyacrylamide hydrogel (PCCA) with pendent boronic acid groups. The embedded CCA diffracts visible light, and the PCCA diffraction wavelength reports on the hydrogel volume. This boronic acid PCCA responds to species containing vicinal cis diols such as carbohydrates. This PCCA photonic crystal sensing material responds to glucose in low ionic strength aqueous solutions by swelling and red shifting its diffraction as the glucose concentration increases. The hydrogel swelling results from a Donnan potential due to formation of boronate anion; the boronic acid pK(a) decreases upon glucose binding. This sensing material responds to glucose and other sugars at <50 microM concentrations in low ionic strength solutions.

  13. Formation of polyelectrolyte multilayers : Ionic strengths and growth regimes

    NARCIS (Netherlands)

    Tang, K.; Besseling, N.A.M.

    2015-01-01

    This article presents a study of layer-by-layer (LbL) formation of poly-electrolyte multilayers (PEMs). Upon increasing ionic strength LbL growth patterns vary from linear for the lowest salt concentrations ([NaCl] = 0, 0.001, and 0.01 M) to exponential (for [NaCl] = 0.5 and 1 M). The slope of the

  14. Charged colloids at low ionic strength: macro- or microphase separation?

    OpenAIRE

    Warren, Patrick B

    2000-01-01

    Phase separation in charged systems may involve the replacement of critical points by microphase separated states, or charge-density-wave states. A density functional theory for highly charged colloids at low ionic strength is developed to examine this possibility. It is found that the lower critical solution point is most susceptible to microphase separation. Moreover the tendency can be quantified, and related to the importance of small ion entropy in suppressing phase separation at low add...

  15. Static facial suspension with Surgisis ES (Enhanced Strength) sling.

    Science.gov (United States)

    Leventhal, Douglas D; Pribitkin, Edmund A

    2008-01-01

    Static suspension procedures stabilize and support paralyzed facial muscles and enhance facial symmetry, appearance, mastication, and speech production in patients with facial palsy. A variety of autografts and allografts have been used for static facial suspension, but each has its limitations, and few studies document the efficacy or benefit of one substance over another. Xenograft tissue scaffoldings potentially offer both the compatibility of autografts and the convenience of allografts. Pilot study to evaluate efficacy of Surgisis ES (Enhanced Strength) static facial suspension in a series of six patients with facial paralysis. Retrospective chart review, illustrative case series, and review of the literature. Six patients with facial paralysis were treated with the Surgisis ES facial sling procedure. Four patients achieved satisfactory results after the initial procedure. One patient was displeased with the esthetic outcome and required a revision procedure to increase the tautness of the implant. In the initial four cases, the sling was tunneled subcutaneously and sutured to the muscle. In two cases, the sling was tunneled subcutaneously and subperiosteally, thereby suspending all the soft tissue in the midface. Static facial suspension with Surgisis ES improved cosmesis and function in this limited pilot study. In particular, a two-plane dissection technique provided excellent results. Further studies need to be conducted to evaluate the ongoing benefit over time.

  16. Effect of ionic surfactants on bauxite residues suspensions viscosity.

    Science.gov (United States)

    Clifton, M; Nguyen, T; Frost, Ray

    2007-03-15

    Measurement of the rheological property of bauxite residue sample received from an Australian alumina refinery, treated with a number of cationic and anionic surfactant in laboratory has been carried out using a Brookfield viscometer for the assessment of the effect of surfactants on the residue viscosity. Sodium laurate, prepared with an excess of sodium hydroxide, was found to be effective while direct addition of anionic surfactants (lauric acid and sodium laureth sulphate) and cationic (cetyl trimethyl ammonium bromide) produce only moderate effect on the red mud suspension apparent viscosity at 65 degrees C. The experimental data appear to confirm the crucial role of the cation sodium in the process of adsorption of anionic surfactants on the flocculated red mud particles.

  17. Ionic strength of electrospray droplets affects charging of DNA oligonucleotides.

    Science.gov (United States)

    Xu, Ning; Chingin, Konstantin; Chen, Huanwen

    2014-01-01

    The fundamental aspects of charging in electrospray ionization (ESI) are hotly debated. In the present study, ESI charging of DNA oligonucleotides was explored in both positive (ESI+) and negative (ESI-) polarity using mass spectrometry detection. Single-stranded 12-mer CCCCAATTCCCC in buffer solution (aqueous NH4Ac, 100 mM) produced similar charge state distribution (CSD) in either ESI+ or ESI-. Similarity of CSD in ESI+ and ESI- was also observed for the double-stranded 12-mer CGCGAATTCGCG. By adding typical low-vapor reagents (e.g. m-nitro benzyl alcohol, m-NBA; sulfolane) into the same buffer solution (sulfolane or m-NBA, the CGCGAATTCGCG duplex dissociated into single strands in ESI-. No SC was observed in both ESI+ and ESI- for thermally denatured CGCGAATTCGCG duplex in NH4 Ac buffer without the reagents. These findings are difficult to reconcile with the earlier model, which attributes SC in aqueous buffer solution to the conformational changes of analytes. Our observations suggest that the ionic strength of ESI droplets strongly affects the CSD of biopolymers such as DNA oligonucleotides and that SC effect is related to the depletion of ionic strength during the ESI process. Copyright © 2014 John Wiley & Sons, Ltd.

  18. Interactions and stability of silver nanoparticles in the aqueous phase: Influence of natural organic matter (NOM) and ionic strength.

    Science.gov (United States)

    Delay, Markus; Dolt, Tamara; Woellhaf, Annette; Sembritzki, Reinhard; Frimmel, Fritz H

    2011-07-08

    The rapid development of nanotechnology and the related production and application of nanosized materials such as engineered nanoparticles (ENP) inevitably lead to the emission of these products into environmental systems. So far, little is known about the occurrence and the behaviour of ENP in environmental aquatic systems. In this contribution, the influence of natural organic matter (NOM) and ionic strength on the stability and the interactions of silver nanoparticles (n-Ag) in aqueous suspensions was investigated using UV-vis spectroscopy and asymmetrical flow field-flow fractionation (AF⁴) coupled with UV-vis detection and mass spectrometry (ICP-MS). n-Ag particles were synthesized by chemical reduction of AgNO₃ with NaBH₄ in the liquid phase at different NOM concentrations. It could be observed that the destabilization effect of increasing ionic strength on n-Ag suspensions was significantly decreased in the presence of NOM, leading to a more stable n-Ag particle suspension. The results indicate that this behaviour is due to the adsorption of NOM molecules onto the surface of n-Ag particles ("coating") and the resulting steric stabilization of the particle suspension. The application of AF⁴ coupled with highly sensitive detectors turned out to be a powerful method to follow the aggregation of n-Ag particle suspensions at different physical-chemical conditions and to get meaningful information on their chemical composition and particle size distributions. The method described will also open the door to obtain reliable data on the occurrence and the behaviour of other ENP in environmental aquatic systems. Copyright © 2011 Elsevier B.V. All rights reserved.

  19. Rheology and structure of ovalbumin gels at low pH and low ionic strength

    NARCIS (Netherlands)

    Weijers, M.; Sagis, L.M.C.; Veerman, C.; Sperber, B.L.H.M.; Linden, van der E.

    2002-01-01

    The objective of this study was to relate the rheological behavior of ovalbumin gels at low pH and low ionic strength to their mesoscopic structure, using rheological measurements and Transmission Electron Microscopy (TEM). Varying pH, ionic strength and protein concentration, we obtained

  20. Discovery of ionic silver in silver nanoparticle suspension fabricated by arc discharge method

    Energy Technology Data Exchange (ETDEWEB)

    Tien, D.-C. [Graduate Institute of Mechanical and Electrical Engineering, National Taipei University of Technology, Taipei 10608, Taiwan (China)], E-mail: s3408508@ntut.edu.tw; Tseng, K.-H.; Liao, C.-Y.; Huang, J.-C. [Department of Electrical Engineering, National Taipei University of Technology, Taipei 10608, Taiwan (China); Tsung, T.-T. [Graduate Institute of Mechanical and Electrical Engineering, National Taipei University of Technology, Taipei 10608, Taiwan (China)

    2008-09-08

    As a result of mankind's over-reliance on antibiotics, germs are becoming more drug-resistant every year. The gradual but inexorable decline in the efficacy of traditional antibiotics is forcing scientists and doctors to search for new weapons in the fight against germs. Metallic silver nanoparticle (Ag{sup 0}) and ionic silver (Ag{sup +}) are the future of the post-antibiotic era, with the latter playing perhaps the central role in this fight. Using the arc discharge method (ADM), our research has allowed us to fabricate silver nanoparticle suspension (SNPS) in deionized water with no added surfactants. Most related research in this field is confined to explore the composition of nanoparticle, ignoring ions. However, we aim to identify and measure the proportion of ionic silver in ADM-SNPS, using conductivity meters, centrifuges, titrator, and atomic absorption spectrophotometer (AA). The results of our experiments show that SNPS fabricated by means of ADM with no added surfactants contains metallic silver nanoparticle and ionic silver. The fabrication consumes silver rods at a rate of 100 mg/min, yielding metallic silver nanoparticle and ionic silver with concentrations of approximately 11 ppm and 19 ppm, respectively.

  1. Ionic strength and composition affect the mobility of surface-modified Fe0 nanoparticles in water-saturated sand columns.

    Science.gov (United States)

    Saleh, Navid; Kim, Hye-Jin; Phenrat, Tanapon; Matyjaszewski, Krzysztof; Tilton, Robert D; Lowry, Gregory V

    2008-05-01

    The surfaces of nanoscale zerovalent iron (NZVI) used for groundwater remediation must be modified to be mobile in the subsurface for emplacement. Adsorbed polymers and surfactants can electrostatically, sterically, or electrosterically stabilize nanoparticle suspensions in water, but their efficacy will depend on groundwater ionic strength and cation type as well as physical and chemical heterogeneities of the aquifer material. Here, the effect of ionic strength and cation type on the mobility of bare, polymer-, and surfactant-modified NZVI is evaluated in water-saturated sand columns at low particle concentrations where filtration theory is applicable. NZVI surface modifiers include a high molecular weight (MW) (125 kg/mol) poly(methacrylic acid)-b-(methyl methacrylate)-b-(styrene sulfonate) triblock copolymer (PMAA-PMMA-PSS), polyaspartate which is a low MW (2-3 kg/mol) biopolymer, and the surfactant sodium dodecyl benzene sulfonate (SDBS, MW = 348.5 g/mol). Bare NZVI with an apparent zeta-potential of -30 +/- 3 mV was immobile. Polyaspartate-modified nanoiron (MRNIP) with an apparent zeta-potential of -39 +/- 1 mV was mobile at low ionic strengths (stabilization afforded by the triblock copolymer but not the other modifiers which provide primarily electrostatic stabilization. Thus, electrosteric stabilization provides the best resistance to changing electrolyte conditions likely to be encountered in real groundwater aquifers, and may provide transport distances of 10s to 100s of meters in unconsolidated sandy aquifers at injection velocities used for emplacement.

  2. Silver nanoparticle aggregation not triggered by an ionic strength mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Botasini, Santiago; Mendez, Eduardo, E-mail: emendez@fcien.edu.uy [Instituto de Quimica Biologica, Universidad de la Republica, Laboratorio de Biomateriales (Uruguay)

    2013-04-15

    The synthesis of stable colloidal solutions of silver nanoparticles is a major goal in the industry to control their fate in aqueous solutions. The present work studies 10-20-nm silver nanoparticle aggregation triggered by the presence of chloride ions. The aggregation process was followed by UV-Vis-NIR spectroscopy and transmission electron microscopy. We found that the mechanism involved differs from the classic explanation of nanoparticle aggregation triggered by an increase in the ionic strength. Moreover, our results give evidence that even when nanoparticles are resistant to an increment of the total amount of ions, the formation of insoluble salts in the vicinity of the nanoparticle is enough to induce the aggregation. The presence of silver chloride around the silver nanoparticles was documented by an X-ray diffraction pattern and electrochemical methods because chloride anions are ubiquitous in real media; this alternative process jeopardized the development of many applications with silver nanoparticles that depend on the use of stable colloids.

  3. Ionic Strength-Mediated Phase Transitions of Surface-Adsorbed DNA on Single-Walled Carbon Nanotubes.

    Science.gov (United States)

    Salem, Daniel P; Gong, Xun; Liu, Albert Tianxiang; Koman, Volodymyr B; Dong, Juyao; Strano, Michael S

    2017-11-22

    Single-stranded DNA oligonucleotides have unique, and in some cases sequence-specific molecular interactions with the surface of carbon nanotubes that remain the subject of fundamental study. In this work, we observe and analyze a generic, ionic strength-mediated phase transition exhibited by over 25 distinct oligonucleotides adsorbed to single-walled carbon nanotubes (SWCNTs) in colloidal suspension. The phase transition occurs as monovalent salts are used to modify the ionic strength from 500 mM to 1 mM, causing a reversible reduction in the fluorescence quantum yield by as much as 90%. The phase transition is only observable by fluorescence quenching within a window of pH and in the presence of dissolved O2, but occurs independently of this optical quenching. The negatively charged phosphate backbone increases (decreases) the DNA surface coverage on an areal basis at high (low) ionic strength, and is well described by a two-state equilibrium model. The resulting quantitative model is able to describe and link, for the first time, the observed changes in optical properties of DNA-wrapped SWCNTs with ionic strength, pH, adsorbed O2, and ascorbic acid. Cytosine nucleobases are shown to alter the adhesion of the DNA to SWCNTs through direct protonation from solution, decreasing the driving force for this phase transition. We show that the phase transition also changes the observed SWCNT corona phase, modulating the recognition of riboflavin. These results provide insight into the unique molecular interactions between DNA and the SWCNT surface, and have implications for molecular sensing, assembly, and nanoparticle separations.

  4. The impact of water content and ionic diffusion on the uniaxial compressive strength of shale

    Directory of Open Access Journals (Sweden)

    Talal AL-Bazali

    2013-12-01

    Finally, the impact of ionic diffusion on the compressive strength of shale was carried out in the absence of both chemical osmosis and capillary forces. Results show that the invasion of sodium and calcium ions into shale reduced its compressive strength considerably while the invasion of potassium ions enhanced its compressive strength.

  5. Surface Physicochemistry and Ionic Strength Affects eDNA's Role in Bacterial Adhesion to Abiotic Surfaces

    DEFF Research Database (Denmark)

    Regina, Viduthalai R.; Lokanathan, Arcot R; Modrzynski, Jakub

    2014-01-01

    DNA-mediated adhesion depends on the physicochemical properties of the surface and surrounding liquid. We investigated eDNA alteration of cell surface hydrophobicity and zeta potential, and subsequently quantified the effect of eDNA on the adhesion of Staphylococcus xylosus to glass surfaces functionalised...... ionic strengths. No effect was seen on glass surfaces and carboxyl-functionalised surfaces at high ionic strength, and a reverse effect occurred on amine-functionalised surfaces at low ionic strength. However, eDNA promoted adhesion of cells to hydrophobic surfaces irrespective of the ionic strength......Extracellular DNA (eDNA) is an important structural component of biofilms formed by many bacteria, but few reports have focused on its role in initial cell adhesion. The aim of this study was to investigate the role of eDNA in bacterial adhesion to abiotic surfaces, and determine to which extent e...

  6. Effects of ionic strength on passive and iontophoretic transport of cationic permeant across human nail.

    Science.gov (United States)

    Smith, Kelly A; Hao, Jinsong; Li, S Kevin

    2009-06-01

    Transport across the human nail under hydration can be modeled as hindered transport across aqueous pore pathways. As such, nail permselectivity to charged species can be manipulated by changing the ionic strength of the system in transungual delivery to treat nail diseases. The present study investigated the effects of ionic strength upon transungual passive and iontophoretic transport. Transungual passive and anodal iontophoretic transport experiments of tetraethylammonium ion (TEA) were conducted under symmetric conditions in which the donor and receiver had the same ionic strength in vitro. Experiments under asymmetric conditions were performed to mimic the in vivo conditions. Prior to the transport studies, TEA uptake studies were performed to assess the partitioning of TEA into the nail. Permselectivity towards TEA was inversely related to ionic strength in both passive and iontophoretic transport. The permeability and transference number of TEA were higher at lower ionic strengths under the symmetric conditions due to increased partitioning of TEA into the nail. Transference numbers were smaller under the asymmetric conditions compared with their symmetric counterparts. The results demonstrate significant ionic strength effects upon the partitioning and transport of a cationic permeant in transungual transport, which may be instrumental in the development of transungual delivery systems.

  7. Ionic Liquid-Tethered Nanoparticle Suspensions: A Novel Class of Ionogels

    KAUST Repository

    Moganty, Surya S.

    2012-04-10

    We report a novel class of silica ionogels created by dispersing silica nanoparticles densely grafted with the ionic liquid (IL) 1-trimethoxysilyl propyl-3-methyl-imidazolium bis- (trifluoromethylsulfonyl) imide (SpmImTSFI) in a 1-butyl-3- methyl-pyrrolidinium bis(trifluoromethylsulfonyl) imide (BmpyrTFSI) IL host. We find that over the entire range of nanoparticle volume fractions studied the systems exist as stable suspensions of SiO 2-SpmImTFSI in the BmpyrTFSI host. Remarkably, we also find that addition of even minute quantities of SiO 2-SpmImTFSI to the BmpyrTFSI IL suppresses crystallization of the host. The resulting disordered hybrid fluids exhibit liquid-like transport properties over a vastly extended temperature range; they open the way for facile synthesis of ILs with extended operating temperature windows. These observations are explained in terms of ionic coupling of the nanoparticle-tethered and free TFSI anions, which is thought to suppress crystallization of BmpyrTFSI. © 2012 American Chemical Society.

  8. Adsorption Isotherms of Boron in Soil: the effects of Sodium Adsorption Ratio (SAR, pH and Ionic strength

    Directory of Open Access Journals (Sweden)

    Mojtaba Moqbeli

    2017-03-01

    Full Text Available Introduction: Boron (B is an essential plant micronutrient whose soil availability is influenced by many soil factors.Understanding the processes controling activity of boron (B in the soil solution is important for soil fertility management. The reaction of adsorption and desorption of boron in soil determines the amount of boron that is available to plants. Adsorption–desorption processes play a major role on boron equilibrium concentration and therefore on its bio-availability. Ionic strength, pH and ionic composition in exchangeable phase are among themajor factors affecting B adsorption reactions.Reducedadsorption of boron at high pH is because of a surface potential decrease onminerals with pH-dependent charge. Ionic strength has also a considerable effect on B adsorption.Several studies have been performed inthe adsorption of boron and the effect of factors such as ionicstrength and cations has been understudied, however, the effect of sodium adsorption ratio and itsinteraction with the ionic strength on boron adsorption behavior has not been reported. In thisstudy, the adsorption isotherms of boron in the soils affected by the combined effects of ionic strengthand sodium adsorption ratio were investigated. Materials and Methods: In order to assess the effects of ionic strength (IS and Sodium Adsorption Ratio (SAR on availability of B, the adsorption of B was investigated in a calcareous soil that hadlow levels of electrical conductivity, sodium adsorption ratio and available P. For this purpose, 5 g soil wasequilibrated with 20 mL of B solution (0, 2, 5, 8, 10, 15, 20 mg L-1 in 0.02, 0.06 and 0.12 M background solutions (prepared by NaC1,CaC12.2H2O, MgCl2.6H2O, at two SAR levels (20 and 100.The reaction temperature was 25◦C. The suspension was centrifuged, filtered, and a sample was removed and B was determined by Azomethine-H spectrophotometric method (at a wavelength of 420 nm. B adsorption in Soil was obtained by subtracting B in

  9. Direct measurement of the strength of single ionic bonds between hydrated charges

    NARCIS (Netherlands)

    Spruijt, E.; Berg, van den S.A.; Cohen Stuart, M.A.; Gucht, van der J.

    2012-01-01

    The strength of ionic bonds is essentially unknown, despite their widespread occurrence in natural and man-made assemblies. Here, we use single-molecule force spectroscopy to measure their strength directly. We disrupt a complex between two oppositely charged polyelectrolyte chains and find two

  10. Dispersion and stability of bare hematite nanoparticles: effect of dispersion tools, nanoparticle concentration, humic acid and ionic strength

    Science.gov (United States)

    Dickson, Dionne; Liu, Guangliang; Li, Chenzhong; Tachiev, Georgio; Cai, Yong

    2012-01-01

    The aggregation and sedimentation of iron oxide nanoparticles (IONPs) can significantly affect the mobility and reactivity of IONPs and subsequently influence the interaction between IONPs and environmental contaminants. Dispersing bare IONPs into a stable suspension within nanoscale range is an important step for studying the interaction of IONPs with contaminants (e.g., toxic metals). In this study, different techniques to disperse bare IONPs (vortex, bath sonication and probe ultrasonication) and the effects of important environmental factors such as dissolved organic matter and ionic strength on the stability of IONPs dispersions were investigated. Vortex minimally dispersed IONPs with hydrodynamic diameter outside the “nanosize range” (698–2400nm). Similar to vortex, bath sonication could not disperse IONPs efficiently. Probe ultrasonication was more effective at dispersing IONPs (50% or more) with hydrodynamic diameters ranging from 120–140 nm with minimal changes in size and sedimentation of IONPs for a prolonged period of time. Over the course of 168 hours, considerable amounts of IONPs remained dispersed in the presence and absence of low ionic strength (0.1 mM of NaCl) and 100 mg/L of humic acid (HA). These results indicate that IONPs can be broken down efficiently into “nanosize range” by probe ultrasonication and a degree of stability can be achieved without the use of synthetic modifiers to enhance colloidal stability. This dispersion tool could be used to develop a laboratory method to study the adsorption mechanism between dispersed bare IONPs and toxic contaminants. PMID:22289174

  11. Effect of pH, ionic strength and fulvic acid on the sorption and desorption of cobalt to bentonite

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Sh.M. [School of Chemical Engineering, Hefei University of Technology, 230009, Hefei, Anhui (China); Ren, A.P. [School of Chemical Engineering, Hefei University of Technology, 230009, Hefei, Anhui (China); Institute of Plasma Physics, Chinese Academy of Sciences, P.O.Box 1126, 230031, Hefei (China); Chen, Ch.L. [Institute of Plasma Physics, Chinese Academy of Sciences, P.O.Box 1126, 230031, Hefei (China); Chen, Y.X. [Institute of Plasma Physics, Chinese Academy of Sciences, P.O.Box 1126, 230031, Hefei (China); Wang, X. [Institute of Plasma Physics, Chinese Academy of Sciences, P.O.Box 1126, 230031, Hefei (China)]. E-mail: xkwang@ipp.ac.cn

    2006-04-15

    Humic substances and bentonite have attracted great interest in radioactive waste management. Here the sorption of cobalt on bentonite in the presence and absence of fulvic acid (FA) under ambient conditions was studied. The effects of pH, ionic strength, FA and solution concentrations on cobalt sorption to bentonite were also investigated using batch techniques. The results indicate that the sorption of cobalt is strongly dependent on pH and is independent of ionic strength under our experimental conditions. Surface complexation is considered the main mechanism of cobalt sorption to bentonite. In the presence of FA, little effect of FA on cobalt sorption was found at pH<6; a positive effect of FA on cobalt sorption was found for pH 6-8; and a negative effect of FA on cobalt sorption was found at pH>8. The addition sequences of FA/Co{sup 2+} to the bentonite suspension on the sorption of cobalt to FA-coated bentonite were also studied. The results indicated that the sorption is not influenced by the addition sequences. Some possible mechanisms are discussed.

  12. Neptunium (V) Adsorption to a Halophilic Bacterium Under High Ionic Strength Conditions: A Surface Complexation Modeling Approach

    Energy Technology Data Exchange (ETDEWEB)

    Ams, David A [Los Alamos National Laboratory

    2012-06-11

    Rationale for experimental design: Np(V) -- important as analog for Pu(V) and for HLW scenarios; High ionic strength -- relevant to salt-based repositories such as the WIPP; Halophilic microorganisms -- representative of high ionic strength environments. For the first time showed: Significant adsorbant to halophilic microorganisms over entire pH range under high ionic strength conditions; Strong influence of ionic strength with increasing adsorption with increasing ionic strength (in contrast to trends of previous low ionic strength studies); Effect of aqueous Np(V) and bacterial surface site speciation on adsorption; and Developed thermodynamic models that can be incorporated into geochemical speciation models to aid in the prediction of the fate and transport of Np(V) in more complex systems.

  13. Bacterial attachment and detachment in aluminum-coated quartz sand in response to ionic strength change.

    Science.gov (United States)

    Lee, Chang-Gu; Park, Seong-Jik; Han, Yong-Un; Park, Jeong-Ann; Kim, Song-Bae

    2010-06-01

    Column experiments were performed to investigate the effect of ionic strength on the attachment and detachment of Staphylococcus aureus ATCC 10537 and Bacillus subtilis ATCC 6633 in aluminum-coated quartz sand. Results showed that the average mass recovery decreased from 80.7 to 45.3% in quartz sand and remained constant in aluminum-coated sand with increasing ionic concentrations of sodium chloride solution from 1 to 100 mmol/L. As the ionic concentrations of leaching solution changed from 100 to 0.1 mmol/L, average mass recovery of 39.1% was obtained from quartz sand (bacterial release), but no detachment was observed from aluminum-coated sand. This lack of detachment can be attributed to inner-sphere complexes between bacteria and aluminum-coated sand, which are minimally affected by ionic strength. This research indicates that aluminum-coated sand has advantages over quartz sand in bacteria removal in water filtration systems.

  14. Ionic strength-dependent changes in tentacular ion exchangers with variable ligand density. II. Functional properties.

    Science.gov (United States)

    Bhambure, Rahul; Angelo, James M; Gillespie, Christopher M; Phillips, Michael; Graalfs, Heiner; Lenhoff, Abraham M

    2017-07-14

    The effect of ligand density was studied on protein adsorption and transport behavior in tentacular cation-exchange sorbents at different ionic strengths. Results were obtained for lysozyme, lactoferrin and a monoclonal antibody (mAb) in order to examine the effects of protein size and charge. The combination of ligand density and ionic strength results in extensive variability of the static and dynamic binding capacities, transport rate and binding affinity of the proteins. Uptake and elution experiments were performed to quantify the transport behavior of selected proteins, specifically to estimate intraparticle protein diffusivities. The observed trend of decreasing uptake diffusivities with an increase in ligand density was correlated to structural properties of the ligand-density variants, particularly the accessible porosity. Increasing the ionic strength of the equilibration buffer led to enhanced mass transfer during uptake, independent of the transport model used, and specifically for larger proteins like lactoferrin and mAb, the most significant effects were evident in the sorbent of the highest ligand density. For lysozyme, higher ligand density leads to higher static and dynamic binding capacities whereas for lactoferrin and the mAb, the binding capacity is a complex function of accessible porosity due to ionic strength-dependent changes. Ligand density has a less pronounced effect on the elution rate, presumably due to ionic strength-dependent changes in the pore architecture of the sorbents. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. Influence of ionic strength on the diffusion of polystyrene latex spheres, bovine serum albumin, and polynucleosomesa)

    Science.gov (United States)

    Schmitz, Kenneth S.; Lu, Mei; Gauntt, Jennifer

    1983-04-01

    Quasielastic light scattering methods were used to determine apparent diffusion coefficients (Dapp) for polystyrene latex spheres, bovine serum albumin, and polynucleosomes under conditions of neutral pH and low ionic strength (0.1-50 mM). Data were collected at several time intervals (Δt) at each of several scattering angles (θ) in the range 35balance between attractive forces arising from fluctuations in the small ion and polyion distributions and the disruptive Brownian forces. Under conditions of extremely low ionic strength, direct interactions between polyions tend to dominate as inferred from data in the literature. These observations suggest at least four regimes in the description of the ionic strength dependence of Dapp.

  16. Ionic strength and transition metals control PrPSc protease resistance and conversion-inducing activity.

    Science.gov (United States)

    Nishina, Koren; Jenks, Samantha; Supattapone, Surachai

    2004-09-24

    The essential component of infectious prions is a misfolded protein termed PrPSc, which is produced by conformational change of a normal host protein, PrPC. It is currently unknown whether PrPSc molecules exist in a unique conformation or whether they are able to undergo additional conformational changes. Under commonly used experimental conditions, PrPSc molecules are characteristically protease-resistant and capable of inducing the conversion of PrPC molecules into new PrPSc molecules. We describe the effects of ionic strength, copper, and zinc on the conformation-dependent protease resistance and conversion-inducing activity of PrPSc molecules in scrapie-infected hamster brains. In the absence of divalent cations, PrPSc molecules were > 20-fold more sensitive to proteinase K digestion in low ionic strength buffers than in high ionic strength buffers. Addition of micromolar concentrations of copper or zinc ions restored the protease resistance of PrPSc molecules under conditions of low ionic strength. These transition metals also controlled the conformation of purified truncated PrP-(27-30) molecules at low ionic strength, confirming that the N-terminal octapeptide repeat region of PrPSc is not required for binding to copper or zinc ions. The protease-sensitive and protease-resistant conformations of PrPSc were reversibly interchangeable, and only the protease-resistant conformation of PrPSc induced by high ionic strength was able to induce the formation of new protease-resistant PrP (PrPres) molecules in vitro. These findings show that PrPSc molecules are structurally interconvertible and that only a subset of PrPSc conformations are able to induce the conversion of other PrP molecules. Copyright 2004 American Society for Biochemistry and Molecular Biology, Inc.

  17. Delineating Effects of Ionic Strength and Suspended Solids on Ammonia Volatilization from Dairy Manure Slurry

    Science.gov (United States)

    Koirala, K.

    2014-12-01

    Ammonia emission is a major concern due to its adverse effects on animal and human health. Ionic strength and suspended solids play key roles in the ammonia volatilization process. These two parameters, however, are usually lumped together in form of total solids. The objective of this study was to separate the contribution of suspended solids (SS) from that of ionic strength (IS) on ammonia volatilization in liquid dairy manure. A two-way factorial experiment was conducted to simultaneously test the effects of IS and SS on ammonium dissociation: a key element of the ammonia volatilization process. The fraction of ammonia (β) in total ammoniacal nitrogen (TAN) was experimentally determined in a convective emission chamber, for each level of SS and IS, at a constant wind speed of 1.5 m s-1, and air and liquid temperature of 25°C. The two way analysis of variance showed a significant effect of SS concentration (p = 0.04) on fraction of ammonia in the liquid dairy manure, while the effect of ionic strength was marginal (p = 0.05). The highest dissociation of ammonium was observed in manure with the lowest SS concentration (0%) and the lowest ionic strength (0.10 mol L-1). Significant increases in suspended solids concentration and ionic strength were necessary to influence the ammonium dissociation in dairy manure. Results revealed that substantially high content of suspended solids (> 3.0%) or relatively high dilution of manure with water (30%) were necessary for these two parameters to play significant roles in the ammonia volatilization mechanism in liquid dairy manure. Results also showed that the β was more sensitive to the changes in suspended solids concentration than in the changes in ionic strength within the ranges of SS and IS examined in this study. Overall, the SS and IS effects on ammonium dissociation (and by extension on ammonia volatilization process) were thus found negligible within the normal ranges of liquid dairy manure characteristics.

  18. Neptunium(V) Adsorption to Bacteria at Low and High Ionic Strength

    Science.gov (United States)

    Ams, D.; Swanson, J. S.; Reed, D. T.

    2010-12-01

    Np(V) is expected to be the predominant oxidation state of neptunium in aerobic natural waters. Np(V), as the NpO2+ aquo and associated complexed species, is readily soluble, interacts weakly with geologic media, and has a high redox stability under a relatively wide range of subsurface conditions. These chemical properties, along with a long half-life make it a primary element of concern regarding long-term nuclear waste storage and subsurface containment. The fate and transport of neptunium in the environment may be influenced by adsorption onto bacterial surfaces. The adsorption of neptunium to bacterial surfaces ties the mobility of the contaminant to the mobility of the bacterium. In this study, the adsorption of the neptunyl (NpO2+) ion was evaluated at low ionic strength on a common soil bacterium and at high ionic strength on a halophilic bacterium isolated from a briny groundwater near the Waste Isolation Pilot Plant (WIPP) in southeast New Mexico. Adsorption experiments were performed in batch reactors as a function of pH, ionic strength, and bacteria/Np mass ratio. Np(V) adsorption was modeled using a surface complexation approach with the mathematical program FITEQL to determine functional group specific binding constants. The data from acid and base titrations of the bacteria used were also modeled to estimate the concentrations and deprotonation constants of discrete bacterial surface functional groups. Bacterial functional group characteristics and Np(V) adsorption behavior between the soil bacterium and the halophilic bacterium were compared. These results highlight key similarities and differences in actinide adsorption behavior in environments of significantly different ionic strength. The observed adsorption behavior may be linked to similarities and differences in the characteristics of the moieties between the cell walls of common gram-negative soil and halophilic bacteria. Moreover, differences in adsorption behavior may also reflect ionic

  19. Response surface optimization of pH and ionic strength for emulsion characteristics of egg yolk.

    Science.gov (United States)

    Kurt, S; Zorba, O

    2009-11-01

    Effects of pH (3.5, 4.5, 6.0, 7.5, and 8.5) and ionic strength (0.05, 0.15, 0.30, 0.45, and 0.55 M NaCl) on emulsion capacity, emulsion stability (ES), apparent yield stress of emulsion (AYS), and emulsion density (ED) of egg yolk were studied by using a model system. Ionic strength and pH had significant (P strenght were 4.61 to 7.43 and 0.10 to 0.47, respectively.

  20. Cardiac strength-interval curves calculated using a bidomain tissue with a parsimonious ionic current.

    Directory of Open Access Journals (Sweden)

    Suran K Galappaththige

    Full Text Available The strength-interval curve plays a major role in understanding how cardiac tissue responds to an electrical stimulus. This complex behavior has been studied previously using the bidomain formulation incorporating the Beeler-Reuter and Luo-Rudy dynamic ionic current models. The complexity of these models renders the interpretation and extrapolation of simulation results problematic. Here we utilize a recently developed parsimonious ionic current model with only two currents-a sodium current that activates rapidly upon depolarization INa and a time-independent inwardly rectifying repolarization current IK-which reproduces many experimentally measured action potential waveforms. Bidomain tissue simulations with this ionic current model reproduce the distinctive dip in the anodal (but not cathodal strength-interval curve. Studying model variants elucidates the necessary and sufficient physiological conditions to predict the polarity dependent dip: a voltage and time dependent INa, a nonlinear rectifying repolarization current, and bidomain tissue with unequal anisotropy ratios.

  1. Gelation of soy glycinin; influence of pH and ionic strength on network structure in relation to protein conformation.

    NARCIS (Netherlands)

    Lakemond, C.M.M.; Jongh, de H.H.J.; Paques, M.; Vliet, van T.; Gruppen, H.; Voragen, A.G.J.

    2003-01-01

    Formation and structure of glycinin gels were studied in relation to protein conformation for two pH values and three ionic strengths. While at I=0.03 the gels were found to be fine stranded, gel coarseness increased when the ionic strength was higher. At I=0.03 finer gel network structures were

  2. Incorporating the effect of ionic strength in free energy calculations using explicit ions

    NARCIS (Netherlands)

    Donnini, S; Mark, AE; Juffer, AH; Villa, Alessandra

    2005-01-01

    The incorporation of explicit ions to mimic the effect of ionic strength or to neutralize the overall charge on a system in free energy calculations using molecular dynamics simulations is investigated. The difference in the free energy of hydration between two triosephosphate isomerase inhibitors

  3. Understanding pH and ionic strength effects on aluminum sulfate-induced microalgae flocculation.

    Science.gov (United States)

    Cui, Y; Yuan, W; Cheng, J

    2014-08-01

    The objective of this study was to understand the effect of pH and ionic strength of aluminum sulfate on the flocculation of microalgae. It was found that changing pH and ionic strength influenced algal flocculation by changing the zeta potential of cells, which was described by the classical theory of Derjaguin, Landau, Verwey, and Overbeek (DLVO). For both algal species of Scenedesmus dimorphus and Nannochloropsis oculata, cells with lower total DLVO interaction energy had higher flocculation efficiency, indicating that the DLVO model was qualitatively accurate in predicting the flocculation of the two algae. However, the two algae responded differently to changing pH and ionic strength. The flocculation of N. oculata increased with increasing aluminum sulfate concentration and favored either low (pH 5) or high (pH 10) pH where cells had relatively low negative surface charges. For S. dimorphus, the highest flocculation was achieved at low ionic strength (1 μM) or moderate pH (pH 7.5) where cell surface charges were fully neutralized (zero zeta potential).

  4. Effect of pH and ionic strength on the bioadhesive properties of ...

    African Journals Online (AJOL)

    Prosopis gum (PG) extracted from Prosopis africana was investigated for bioadhesive properties as affected by pH and ionic strength. The bioadhesive properties were evaluated using the adhesion of gum dispersion-coated glass beads on the antrum region of the porcine gastrointestinal tract and Lecomte Du Nouy ...

  5. The ionic strength effect on the DNA complexation by DOPC - gemini surfactants liposomes.

    Science.gov (United States)

    Pullmannová, Petra; Bastos, Margarida; Bai, Guangyue; Funari, Sergio S; Lacko, Ivan; Devínsky, Ferdinand; Teixeira, José; Uhríková, Daniela

    2012-01-01

    Liposome dispersions obtained from the mixture of gemini surfactants of the type alkane-α,ω-diyl-bis(alkyldimethylammonium bromide) and helper lipid DOPC create complexes with DNA showing a regular inner microstructure, identified by small angle X-ray diffraction as condensed lamellar phase (L(α)(c)). In addition to the L(α)(c) phase, a coexisting lamellar phase L(B) was also identified in the complexes formed, with periodicities in the range ~8.8-5.7nm, at ionic strengths corresponding to 50-200mM NaCl. The periodicities of L(B) phase did not correspond to those identified in liposome dispersion without DNA using small angle neutron scattering. The observed phase separation is shown to depend on the interplay between the surface charge density of cationic liposomes, ionic strength and method of complex preparation. The effect of ionic strength on complex formation was studied by isothermal titration calorimetry and zeta potential measurements. High ionic strength reduces the fraction of bound DNA in the complexes, and the isoelectric point is attained at a ratio of DNA/gemini surfactant which is lower than the one that can be estimated by calculation based on nominal charges of CLs and DNA. Copyright © 2011 Elsevier B.V. All rights reserved.

  6. Ionic Strength Mediated Self-Organization of Gold Nanocrystals: An AFM Study

    NARCIS (Netherlands)

    Kooij, Ernst S.; Brouwer, E.A.M.; Wormeester, Herbert; Poelsema, Bene

    2002-01-01

    The deposition of charge-stabilized colloidal gold nanocrystals on silicon substrates, derivatized with (aminopropyl)triethoxysilane (APTES), is studied using atomic force microscopy. The influence of ionic strength on the spatial distribution of gold nanocrystal assemblies is analyzed in terms of

  7. Quantifying bacterial attachment and detachment using leaching solutions of various ionic strengths after bacterial pulse.

    Science.gov (United States)

    Choi, Nag-Choul; Choi, Jae-Woo; Kwon, Kyu-Sang; Lee, Sang-Gil; Lee, Soonjae

    2017-12-01

    In this study, we quantified the attachment and detachment of bacteria during transport in order to elucidate the contributions of reversible attachment on bacterial breakthrough curves. The first set of breakthrough experiment was performed for a laboratory sand column using leaching solutions of deionized water and mineral salt medium (MSM) of 200 mM with reference to KCl solution by employing Pseudomonas putida as a model bacterium. In the second set of experiment, the ionic strengths of leaching solutions immediately after bacterial pulse were lowered to tenfold and 100-fold diluted system (2 and 20 mM MSM) to focus on the influence of physicochemical factor. Results have shown that bacterial retention occurred in the sand column due to the physical deposition and physicochemical attachment. The physicochemical attachment was attributed to the high ionic strength (200 mM MSM) of leaching solution and the formation of primary energy minimum. Replacing the 200 mM leaching solution with the lower ionic strengths after pulse resulted in the increased tailing of breakthrough curve due to the detachment from the attached bacteria. The detachment could be well explained by DLVO theory, which showed the formation of energy barrier and disappearance of the secondary minimum as the ionic strength gradually decreased. Analysis of mass recovery revealed that 12-20% of the attachment was due to physical and physicochemical attachment, respectively, where the latter consisted of 25-75% of irreversible and reversible attachment respectively.

  8. The structure of pH dependent block copolymer micelles: charge and ionic strength dependence

    Energy Technology Data Exchange (ETDEWEB)

    Pople, John A

    2002-08-06

    We characterize the structures of various polyelectrolyte block copolymer micelles in dilute aqueous solution as a function of pH and ionic strength. The block copolymers carry a common core block 2-(diethylamino) ethyl methacrylate (DEAEMA) and one of three coronal blocks: 2-(dimethylamino) ethyl methacrylate (DMAEMA), polyethylene oxide (PEO), and DMAEMA whose side-chain amine groups are selectively quaternized with benzyl chloride (Q-DMAEMA). The PEO-DEAEMA, DMAEMA-DEAEMA, and Q-DMAEMA-DEAEMA copolymers form micelles with electrostatically neutral, weakly charged, and highly charged coronae, respectively. We adjust the fractional charge a on the DEAEMA and DMAEMA blocks by adjusting the solution pH. For DMAEMA-DEAEMA micelles increasing the fractional charge a swells the micelle corona while decreasing the aggregation number due to electrostatic repulsions. The decrease in aggregation number is also observed with increasing a for the PEO-DEAEMA and Q-DMAEMA-DEAEMA micelles, due to electrostatic repulsions between the hydrophobic DEAEMA blocks. Increasing the ionic strength causes the DMAEMA-DEAEMA micelle corona to shrink as the salt screens electrostatic repulsions within the corona. In all three copolymers increases in the ionic strength causes the micelle aggregation number to increase by screening the electrostatic repulsions between chains. Trends in the corona thickness with varying fractional charge and ionic strength are compared with a number of theoretical models providing additional insight into the micelle structure.

  9. Ionic strength-dependent changes in tentacular ion exchangers with variable ligand density. I. Structural properties.

    Science.gov (United States)

    Bhambure, Rahul; Gillespie, Christopher M; Phillips, Michael; Graalfs, Heiner; Lenhoff, Abraham M

    2016-09-09

    The ligand density critically affects the performance of ion-exchange resins in such measures as the adsorption capacity and transport characteristics. However, for tentacular and other polymer-modified exchangers, the mechanistic basis of the effect of ligand density on performance is not yet fully understood. In this study we map the ionic strength-dependent structural changes in tentacular cation exchangers with variable ligand densities as the basis for subsequent investigation of effects on functional properties. Inverse size-exclusion chromatography (ISEC), scanning electron microscopy (SEM) and small-angle x-ray scattering (SAXS) were used to assess the effect of ionic strength on the pore size and intraparticle architecture of resin variants with different ligand densities. Comparison of ISEC and cryo-SEM results shows a considerable reduction in average pore size with increasing ligand density; these methods also confirm an increase of average pore size at higher ionic strengths. SAXS analysis of ionic strength-dependent conformational changes in the grafted polyelectrolyte layer shows a characteristic ionomer peak at values of the scattering vector q (0.1-0.2Å(-1)) that depend on the ligand density and the ionic strength of the solution. This peak attribution reflects nanoscale changes in the structure of the grafted polyelectrolyte chains that can in turn be responsible for observed pore-size changes in the resins. Finally, salt breakthrough experiments confirm a stronger Donnan exclusion effect on pore accessibility for small ions in the high ligand density variant. Copyright © 2016 Elsevier B.V. All rights reserved.

  10. In-situ AC electroosmotic and thermal perturbation effects for wide range of ionic strength

    Directory of Open Access Journals (Sweden)

    Reza Hadjiaghaie Vafaie

    2017-06-01

    Full Text Available AC electrokinetic flow is promising in designing microfluidic chips for manipulation of biological and chemical samples toward clinical diagnostics. Four pieces of electrodes are optimized to enhance mixing effect inside a straight microchannel. In this research, the mixing dependency on the ionic strength of solutions is investigated. AC electroosmotic secondary flow is responsible for the mixing at low ionic strength (σ < 5 mS m–1, whereas AC electrothermal secondary flow is proposed to mix high conductive mediums (σ > 5 mS m–1. The electrode-electrolyte impedance analysis is employed to facilitate the in-situation mixing process by choosing appropriate electrical excitation parameters for the electrodes.

  11. A New Concept of Ultrafiltration Fouling Control: Backwashing with Low Ionic Strength Water

    OpenAIRE

    Li, S.

    2011-01-01

    Ultrafiltration (UF) is a proven technology in water treatment nowadays. However, fouling remains a major challenge in the operation of UF, especially in regard to colloidal NOM fouling. In general, a number of colloidal NOM fouling mechanisms may occur, such as adsorption, gel formation. Colloidal NOM fouling is influenced by multivalent cations, ionic strength and pH. In order to control membrane fouling, different pretreatments such as powder activated carbon adsorption, lime softening, io...

  12. Deposition and release kinetics of nano-TiO2 in saturated porous media: effects of solution ionic strength and surfactants.

    Science.gov (United States)

    Godinez, Itzel G; Darnault, Christophe J G; Khodadoust, Amid P; Bogdan, Dorin

    2013-03-01

    The aggregation, transport and deposition kinetics (i.e. attachment and release) of TiO(2) nanoparticles (nano-TiO(2)) were investigated as a function of ionic strength and the presence of anionic (sodium dodecylbenzene sulfonate, SDBS) and non-ionic (Triton X-100) surfactants in 100% critical micelle concentration (CMC). The electrolyte concentration of the suspensions dictated the kinetic stability of nano-TiO(2) thus influencing the transport and retention of the nanoaggregates in the saturated porous medium. With increasing ionic strength, the interaction between approaching nano-TiO(2) and nano-TiO(2) already deposited onto collectors surfaces seemed to be more favorable than the interaction between approaching nano-TiO(2) and bare collectors surfaces. The abrupt and gradual reduction in electrolyte concentration during the flushing cycles of the column experiments induced the release of previously deposited nano-TiO(2) suggesting attachment of nano-TiO(2) through secondary energy minimum. Copyright © 2012 Elsevier Ltd. All rights reserved.

  13. Dissolution kinetics and mechanisms at dolomite-water interfaces: effects of electrolyte specific ionic strength.

    Science.gov (United States)

    Xu, Man; Sullivan, Katie; Vanness, Garrett; Knauss, Kevin G; Higgins, Steven R

    2013-01-02

    Elucidating dissolution kinetics and mechanisms at carbonate mineral-water interfaces is essential to many environmental and geochemical processes, including geologic CO(2) sequestration in deep aquifers. In the present work, effects of background electrolytes on dolomite (CaMg(CO(3))(2)) reactivity were investigated by measuring step dissolution rates using in situ hydrothermal atomic force microscopy (HAFM) at 90 °C. Cleaved surfaces of dolomite were exposed to sodium chloride and tetramethylammonium chloride (TMACl) aqueous solutions with ionic strengths (I) ranging from 0 to 0.77 m at pH 4 and pH 9. HAFM results demonstrated that dolomite step retreat rates increased with increasing solution ionic strength and decreasing pH. Comparison of [481] and [441] steps revealed that the anisotropy of [481] and [441] step speeds became significant as solution ionic strength increased, with NaCl exerting more pronounced effects than TMACl for the same I. To interpret the different trends observed for NaCl and TMACl, a dissolution mechanism involving orientation-dependent ion adsorption and consequent edge free energy changes is proposed.

  14. Colloid transport in dolomite rock fractures: effects of fracture characteristics, specific discharge, and ionic strength.

    Science.gov (United States)

    Mondal, Pulin K; Sleep, Brent E

    2012-09-18

    The effects of fracture characteristics, specific discharge, and ionic strength on microsphere transport in variable-aperture dolomite rock fractures were studied in a laboratory-scale system. Fractures with different aperture distributions and mineral compositions were artificially created in two dolomite rock blocks. Transport tests were conducted with bromide and carboxylate-modified latex microspheres (20, 200, and 500 nm diameter). Under overall unfavorable attachment conditions, there was significant retention of the 20 nm microsphere and minimal retention of the 500 nm microsphere for all conditions examined. Aperture variability produced significant spatial variation in colloid transport. Flushing with low ionic strength solution (1 mM) following microsphere transport at 12 mM ionic strength solution produced a spike in effluent microsphere concentrations, consistent with retention of colloids in secondary energy minima. Surface roughness and charge heterogeneity effects may have also contributed to the effect of microsphere size on retention. Matrix diffusion influenced bromide transport but was not a dominant factor in transport for any microsphere size. Calibrated one-dimensional, two-site kinetic model parameters for colloid transport in fractured dolomite were sensitive to the physical and chemical properties of both the fractured dolomite and the colloids, indicating the need for mechanistic modeling for accurate prediction.

  15. Influence of ionic strength on the rheological properties of hydroxypropylmethyl cellulose-sodium dodecylsulfate mixtures

    Directory of Open Access Journals (Sweden)

    Katona Jaroslav M.

    2015-01-01

    Full Text Available Mixtures of polymers and surfactants are commonly found in a range of products of pharmaceutical, cosmetic, and food industry. Interaction between polymers and surfactants influences different properties of these products, e.g. stability, flow properties, phase behavior, etc. It is known from previous work that an interaction in binary mixtures of hydroxypropylmethyl cellulose (HPMC and sodium dodecylsulfate (SDS takes place when SDS concentration (CSDS. is higher than the critical association concentration (CAC and lower than the polymer saturation point (PSP. The interaction results in the formation of an HPMC-SDS complex. The objective of this work was to study the effect of the ionic strength on the HPMC-SDS complex formation by rheological investigation. The HPMC/SDS mixtures composed of 0.70 % wt. HPMC, and 0.00 % to 2.50 % wt. SDS were prepared in deionized water, 0.01M and 0.05M NaCl solution. It was found that an increase in the ionic strength influences the HPMC-SDS complex formation by increasing the zero shear viscosity of the mixtures in the interaction region (CACPSP. The HPMC/SDS mixtures showed a shear thinning or a shear thickening flow properties depending on CSDS. The flow properties were influenced by the ionic strength of the mixtures.[Projekat Ministarstva nauke Republike Srbije, br. III46010

  16. Effect of high ionic strength on the extraction of uranium(VI ions

    Directory of Open Access Journals (Sweden)

    M.K. Nazal

    2014-01-01

    Full Text Available Preparation and characterization of didodecylphosphoric acid (HDDPA as an extractant in toluene was carried. Mass spectroscopy showed that the monomer peak at 457.4 amu [M–Na+] is double that of the dimer at 891.9 amu [M–M–Na+] and the monomer molecules concentration dominate the dimer molecules in toluene. HDDPA was used as an extractant for the extraction of U(VI ion from perchlorate and nitrate media that have ionic strength (1.00, 3.00, 5.00, 7.00 M. The effect of HDDPA concentration, pcH, ionic strength of supporting electrolytes, and temperature in the range 15–45 °C on the extraction process have been studied. The stoichiometry of the extraction of U(VI ion, the free energy change (ΔG, the enthalpy change (ΔH, the entropy change (ΔS, and Kex at different ionic strength have been calculated. The formula of the complexes, which were formed has been established to be UO2(X(R2(HR2 at pcH equal 2.00 and UO2(X(R2(HR2 and UO2(X(R2 at pcH = 1.00, where (X isClO4- orNO3- and (HR2 is didodecylphosphoric acid monomer, (R2 is the deprotonated didodecylphosphoric acid, where R is the dodecyl group.

  17. Removal of natural organic matter by titanium tetrachloride: The effect of total hardness and ionic strength.

    Science.gov (United States)

    Zhao, Y X; Shon, H K; Phuntsho, S; Gao, B Y

    2014-02-15

    This study is the first attempt to investigate the effect of total hardness and ionic strength on coagulation performance and the floc characteristics of titanium tetrachloride (TiCl4). Membrane fouling under different total hardness and ionic strength conditions was also evaluated during a coagulation-ultrafiltration (C-UF) hybrid process. Coagulation experiments were performed with two simulated waters, using humic acid (HA, high molecular weight) and fulvic acid (FA, relatively low molecular weight), respectively, as model natural organic matter (NOM). Results show that both particle and organic matter removal can be enhanced by increasing total hardness and ionic strength. Floc characteristics were significantly influenced by total hardness and ionic strength and were improved in terms of floc size, growth rate, strength, recoverability and compactness. The results of the UF tests show that the pre-coagulation with TiCl4 significantly improves the membrane permeate fluxes. Under different total hardness and ionic strength conditions, the membrane permeate flux varied according to both NOM and floc characteristics. The increase in total hardness and ionic strength improved the membrane permeate flux in the case of HA simulated water treatment. Copyright © 2014 Elsevier Ltd. All rights reserved.

  18. Improving pH gradient cation-exchange chromatography of monoclonal antibodies by controlling ionic strength.

    Science.gov (United States)

    Zhang, Liangyi; Patapoff, Thomas; Farnan, Dell; Zhang, Boyan

    2013-01-11

    Analytical ion exchange chromatography (IEC) is widely used to profile the charge heterogeneity of therapeutic monoclonal antibodies (mAbs). Since conventional salt gradient IEC methods are product-specific and time-consuming to develop, a previously reported alternative pH gradient IEC (pH-IEC) method using a cation-exchange column has been shown to be a multiproduct charge sensitive separation method for mAbs with isoelectric points between 7.3 and 9.0. In the work presented here, we have extended the application of that pH-IEC method to also profile the charge heterogeneity of mAbs with extreme pI values (e.g. acidic with pI9). A key observation of our work is that for the buffer systems used by Farnan and Moreno, the ionic strength of the mobile phase containing multiple polyamine buffers is pH and concentration dependent, and the ionic strength decreases when the pH increases. For the mobile phase with high buffer concentration the ionic strength is high at low pH values, leading to the flow through of acidic mAbs on the cation-exchange column. The basic mAbs may not have an optimal elution profile as the relatively low ionic strength of the mobile phase reduces the resolution of pH-IEC. To modulate the ionic strength, we introduced a salt gradient in addition to the pH gradient. Studies were performed to optimize the buffer and salt concentrations simultaneously to improve the retention of low pI mAbs and the resolution of high pI mAbs. The optimized salt-mediated pH-IEC method was not only applicable to mAbs over a broader pI range from 6.2 to 9.4, but also offered better resolution for mAbs with pI values between 7.3 and 9.0 than the previously reported pH-IEC method. This salt-mediated pH-IEC method was demonstrated to be robust at various chromatography conditions and capable of assessing manufacturing consistency and monitoring degradation of mAbs. Copyright © 2012 Elsevier B.V. All rights reserved.

  19. Rheological properties of epoxy/MWCNT suspensions associated with the surface modification of MWCNT by physisorption of aromatic ionic salts

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Yu-Hsun [Institute of Polymer Science and Engineering, National Taiwan University, Taipei 106, Taiwan (China); Lin, King-Fu, E-mail: kflin@ntu.edu.tw [Institute of Polymer Science and Engineering, National Taiwan University, Taipei 106, Taiwan (China); Department of Materials Science and Engineering, National Taiwan University, Taipei 106, Taiwan (China)

    2016-04-15

    The multi-walled carbon nanotubes (MWCNTs) physisorbed by aromatic ionic salts such as 10-methyl-acridinium iodide (MAcI) were found to well disperse in diglycidyl ether of bisphenol-A epoxy resin. As they were subjected to the rheological study at 30 °C, the gelation of epoxy/MWCNT-MAcI suspension occurred at 0.75 wt% MWCNT-MAcI, which was less than that using pristine MWCNT. As to the viscosity measurements, the dilation effect that the viscosity of epoxy/MWCNT suspension increases with shear rate was found and more pronounced by incorporating MWCNT-MAcI. According to the Thomas-modified Einstein viscosity equation, the dilation effect was attributed to the excess amount of epoxy resin trapping in the aggregated domain of MWCNT. By increasing the shear rate to a certain point, the shear thinning effect that the viscosity decreases with shear rate was also observed. Interestingly, the transition point that the dilation effect changes to shear thinning effect shifted to lower shear rate as the content of MWCNT increased and/or MWCNT-MAcI was incorporated. Notably, better dispersion and less aggregated domains for the suspensions with MWCNT-MAcI compared to pristine MWCNT were further supported by small angle x-ray scattering and transmission electron microscopy. - Highlights: • Dilation effect that viscosity of epoxy/MWCNT suspension increases with shear rate was discovered. • Dilation effect was attributed to the excess epoxy resin trapping in the aggregated domain of MWCNT. • The transition point that the dilation effect changes to shear thinning effect was observed.

  20. Effects of 5 weeks of lower limb suspension on muscle size and strength

    Science.gov (United States)

    Tesch, P. A.; Ploutz, L. L.; Dudley, G. A.

    1994-01-01

    Lack of weight-bearing, as occurs in space, appears to be associated with reductions in strength and mass of skeletal muscle. Very limited data, however, is at hand describing changes in skeletal muscle size and function following manned space missions. Our current knowledge therefore is mainly based on studies of space flown rats. It is obvious though that this information, only in part can be extrapolated to humans. A few bed rest studies have demonstrated that decreases in strength and muscle size are substantial. At this time, however, the magnitude or time course of such changes either in response to space flight or simulations of microgravity have not been defined. In the last few years we have employed a human model to simulate unloading of lower limb skeletal muscles that occurs in microgravity. This model was essentially adopted from the rat hindlimb suspension technique. The purpose of this study was to assess the magnitude of decreases in muscle strength and size as a result of five weeks of unilateral lower limb suspension.

  1. Effects of ionic strength and ion pairing on (plant-wide) modelling of anaerobic digestion

    DEFF Research Database (Denmark)

    Solon, Kimberly; Flores Alsina, Xavier; Mbamba, Christian Kazadi

    2015-01-01

    approach to consider chemical activities instead of molar concentrations. A speciation sub-routine based on a multi-dimensional Newton-Raphson (NR) iteration method is developed to address algebraic interdependencies. The model also includes ion pairs that play an important role in wastewater treatment....... The paper describes: 1) how the anaerobic digester performance is affected by physico-chemical corrections; 2) the effect on pH and the anaerobic digestion products (CO2, CH4 and H2); and, 3) how these variations are propagated from the sludge treatment to the water line. Results at high ionic strength...

  2. The first hydrolysis constant of Eu(III) in 4 M ionic strength at 303 K

    Energy Technology Data Exchange (ETDEWEB)

    Jimenez-Reyes, M. (Instituto Nacional de Investigaciones Nucleares, Mexico City (Mexico). Dept. de Quimica); Solache-Rios, M. (Instituto Nacional de Investigaciones Nucleares, Mexico City (Mexico). Dept. de Quimica)

    1994-01-01

    The first hydrolysis constant of Eu[sup 3+] has been determined at 303 K and 4 M (NaCl) ionic strength. A solvent extraction method was used, the extractant was dibenzoylmethane in benzene and diglycolate anion in the aqueous phase provided competitive complexation. The reaction and the value obtained for the constant were: Eu[sup 3+] + H[sub 2]O = Eu(OH)[sup 2+] + H[sup +], log [beta][sub 1,H] = -6.33 [+-] 0.09. (orig.)

  3. Spectroscopic investigations on sorption of uranium onto suspended bentonite. Effects of pH, ionic strength and complexing anions

    Energy Technology Data Exchange (ETDEWEB)

    Verma, Parveen Kumar; Pathak, Priyanath; Mohapatra, Manoj; Mohapatra, Prasanta Kumar [Bhabha Atomic Research Centre, Mumbai (India). Radiochemistry Div.; Yadav, Ashok Kumar; Jha, Sambhunath; Bhattacharyya, Dibyendu [Bhabha Atomic Research Centre, Mumbai (India). Atomic and Molecular Physics Div.

    2015-06-01

    Batch sorption experiments were carried out under aerobic conditions to understand the sorption behavior of U(VI) onto bentonite clay under varying pH (2-8) and ionic strength (I = 0.01 - 1 M (NaClO{sub 4})) conditions. The influences of different complexing anions (1 x 10{sup -4} M) such as oxalic acid (ox), carbonate (CO{sub 3}{sup 2-}), citric acid (cit), and humic acid (HA, 10 mg/L) on the sorption behavior were also investigated. The sorption of U(VI) increased with increasing pH up to pH 6 beyond which a decrease was attributed to the formation of anionic carbonate species. Marginal influence of the change in the ionic strength of the medium on the sorption profile of uranium suggested inner-sphere complexation onto the bentonite surface. The presence of humic acid showed interesting sorption profile with varying pH. Initially, there was an enhancement in the sorption with increased pH followed by a plateau and finally a decrease thereafter due to the formation of aqueous U(VI)-humate complexes. Spectroscopic studies such as UV spectrophotometry, luminescence and extended X-ray absorption fine structure (EXAFS) measurements were also performed to understand the changes in aqueous speciation of U(VI) ion. The luminescence yields of different aqueous U(VI) species followed the order: U(VI){sub Hydroxy} > U(VI){sub HumicAcid} > U(VI){sub carbonate} > U(VI){sub citrate}. The lower luminescence yield of U(VI)carbonate complex can be attributed to the strong dynamic quenching by carbonate at room temperature. The U(VI) samples shows two distinct life-time suggesting the presence of the different luminescent U(VI) species. Similar trend was observed for U(VI)-bentonite suspension in presence/absence of the complexing ligands. There was luminescence quenching for the sorbed U(VI) due to surface complexation. These observations were further supported by spectrophotometric measurements. EXAFS spectra of U(VI) samples were recorded in luminescence mode at the U L{sub 3

  4. General strategy for biodetection in high ionic strength solutions using transistor-based nanoelectronic sensors.

    Science.gov (United States)

    Gao, Ning; Zhou, Wei; Jiang, Xiaocheng; Hong, Guosong; Fu, Tian-Ming; Lieber, Charles M

    2015-03-11

    Transistor-based nanoelectronic sensors are capable of label-free real-time chemical and biological detection with high sensitivity and spatial resolution, although the short Debye screening length in high ionic strength solutions has made difficult applications relevant to physiological conditions. Here, we describe a new and general strategy to overcome this challenge for field-effect transistor (FET) sensors that involves incorporating a porous and biomolecule permeable polymer layer on the FET sensor. This polymer layer increases the effective screening length in the region immediately adjacent to the device surface and thereby enables detection of biomolecules in high ionic strength solutions in real-time. Studies of silicon nanowire field-effect transistors with additional polyethylene glycol (PEG) modification show that prostate specific antigen (PSA) can be readily detected in solutions with phosphate buffer (PB) concentrations as high as 150 mM, while similar devices without PEG modification only exhibit detectable signals for concentrations ≤10 mM. Concentration-dependent measurements exhibited real-time detection of PSA with a sensitivity of at least 10 nM in 100 mM PB with linear response up to the highest (1000 nM) PSA concentrations tested. The current work represents an important step toward general application of transistor-based nanoelectronic detectors for biochemical sensing in physiological environments and is expected to open up exciting opportunities for in vitro and in vivo biological sensing relevant to basic biology research through medicine.

  5. Effects of ionic strength on the antimicrobial photodynamic efficiency of methylene blue.

    Science.gov (United States)

    Núñez, Silvia Cristina; Garcez, Aguinaldo Silva; Kato, Ilka Tiemy; Yoshimura, Tania Mateus; Gomes, Laércio; Baptista, Maurício Silva; Ribeiro, Martha Simões

    2014-03-01

    Antimicrobial photodynamic therapy (APDT) may become a useful clinical tool to treat microbial infections, and methylene blue (MB) is a well-known photosensitizer constantly employed in APDT studies, and although MB presents good efficiency in antimicrobial studies, some of the MB photochemical characteristics still have to be evaluated in terms of APDT. This work aimed to evaluate the role of MB solvent's ionic strength regarding dimerization, photochemistry, and photodynamic antimicrobial efficiency. Microbiological survival fraction assays on Escherichia coli were employed to verify the solution's influence on MB antimicrobial activity. MB was evaluated in deionized water and 0.9% saline solution through optical absorption spectroscopy; the solutions were also analysed via dissolved oxygen availability and reactive oxygen species (ROS) production. Our results show that bacterial reduction was increased in deionized water. Also we demonstrated that saline solution presents less oxygen availability than water, the dimer/monomer ratio for MB in saline is smaller than in water and MB presented a higher production of ROS in water than in 0.9% saline. Together, our results indicate the importance of the ionic strength in the photodynamic effectiveness and point out that this variable must be taken into account to design antimicrobial studies and to evaluate similar studies that might present conflicting results.

  6. The influence of ionic strength on the interaction of viruses with charged surfaces under environmental conditions.

    Science.gov (United States)

    Schaldach, C M; Bourcier, William L; Shaw, Henry F; Viani, Brian E; Wilson, W D

    2006-02-01

    The influence of ionic strength on the electrostatic interaction of viruses with environmentally relevant surfaces was determined for three viruses, MS2, Q beta, and Norwalk. The virus is modeled as a particle comprised of ionizable amino acid residues in a shell surrounding a spherical RNA core of negative charge, these charges being compensated for by a Coulomb screening due to intercalated ions. A second model of the virus involving surface charges only is included for comparison. Surface potential calculations for each of the viruses show excellent agreement with electrophoretic mobility and zeta potential measurements as a function of pH. The environmental surface is modeled as a homogeneous plane held at constant potential with and without a finite region (patch) of opposite potential. The results indicate that the electrostatic interaction between the virus and the oppositely charged patch is significantly influenced by the conditions of ionic strength, pH and size of the patch. Specifically, at pH 7, the Norwalk virus interacts more strongly with the patch than MS2 (approximately 51 vs approximately 9kT) but at pH 5, the Norwalk-surface interaction is negligible while that of MS2 is approximately 5.9kT. The resulting ramifications for the use of MS2 as a surrogate for Norwalk are discussed.

  7. Ionic strength dependence of the hysteresis in the polyriboadenylate-polyribouridylate system.

    Science.gov (United States)

    Spodheim, M; Neumann, E

    1975-04-01

    The hysteresis observed in cyclic acid-base titrations of the three-standed polyribonucleotide helix poly (A)-2 POLY (U) strongly depends on ionic strength. For NaCl and at 25 degrees C, hysteresis occurs in the limited concentration range between 0.03 M and 1.0 M(NaCl). The transition points associated with the cyclic conversions between the triple helix and the poly (A)-poly (A) double helix and (free) poly (U) constitute a (pH ionic strength) phase diagram covering the ranges of stability and metastability of the hysteresis system. Variations with NaCl concentration of some hysteresis parameters can be quantitatively described in terms of polyelectrolyte theories based on the cylinder-cell model for rodlike polyions. The results of this analysis suggest that the metastability is predominantly due to dlectrostatic energy barriers preventing the equilibrium transition of the partially protonated triple helix above a critical pH value. Ultraviolet absorbance and potentiometric titration data of poly (A)in the acidic pH range can be analyzed in terms of two types of double-helical structures. Spectrophotometric titrations reveal isosbestic wavelengths for structural transitions of poly (A). "Time effects" commonly observed in poly (A) titrations are suggested to reflect helix transitions between the two acidic structures.

  8. Transmembrane Potential of Red Blood Cells Under Low Ionic Strength Conditions

    Directory of Open Access Journals (Sweden)

    Daniel Moersdorf

    2013-06-01

    Full Text Available Background/Aims: In a variety of investigations described in the literature it was not clear to what extent the transmembrane potential red blood cells (RBCs was changed after the cells have been transferred into low ionic strength (LIS solutions. Another open question was to find out how fast the transmembrane potential of RBCs in LIS solution will change and which final new equilibrium value will be reached. Methods: The transmembrane potential of human and bovine RBCs was investigated using the potential-sensitive fluorescent dye DIBAC4(3 (bis(1,3-dibutylbarbituric acid trimethine oxonol as well as the CCCP (carbonylcyanide-m-chlorophenylhydrazone method. Results: Under physiological conditions the transmembrane potential was about -10 mV in agreement with literature data. However, when the RBCs were transferred into an isosmotic low ionic strength medium containing sucrose the transmembrane potential increased to +73 mV and +81 mV for human and bovine RBCs, respectively. In case of human RBCs it continuously decreased reaching finally an equilibrium state of -10 mV again after 30 - 60 min. For bovine RBCs the transmembrane potential declined more slowly reaching a value of +72 mV after 30 min. Conclusions: Investigations of parameters of RBCs depending on transmembrane potential cannot be performed with human RBCs in LIS media.

  9. Relationship of land use and elevated ionic strength in Appalachian watersheds.

    Science.gov (United States)

    Cormier, Susan M; Wilkes, Samuel P; Zheng, Lei

    2013-02-01

    Coal mining activities have been implicated as sources that increase stream specific conductance in Central Appalachia. The present study characterized potential sources of elevated ionic strength for small subwatersheds within the Coal, Upper Kanawha, Gauley, and New Rivers in West Virginia. From a large monitoring data set developed by the West Virginia Department of Environmental Protection, 162 water chemistry sample. Scatter plots of specific conductance were generated for nine land cover classifications: open water, agriculture, forest, residential, barren, total mining, valley fill, abandoned mine lands, and mining excluding valley fill and abandoned mine lands. Conductivity was negatively correlated with the percentage of forest area and positively associated with other land uses. In a multiple regression, the percentage of area in valley fill was the strongest contributor to increased ionic strength, followed by percentage of area in urban (residential/buildings) land use and other mining land use. Based on the 10th quantile regression, 300 µS/cm was exceeded at 3.3% of area in valley fill. In most catchments, HCO 3(-) and SO 4(2-) concentrations were greater than Cl(-) concentration. These findings confirm coal mining activities as the primary source of high conductivity waters. Such activities might be redressed with the goal of protecting sources of dilute freshwater in the region. Copyright © 2012 SETAC.

  10. Controlling the buckling instability of drying droplets of suspensions through colloidal interactions

    OpenAIRE

    Lintingre, É.; Ducouret, G.; Lequeux, F.; Olanier, L.; Périé, T.; Talini, L

    2015-01-01

    International audience; The present study focuses on the drying of droplets of colloidal suspensions using the Leidenfrost effect. At the end of drying, grains show different morphologies: cups or spheres depending on the ionic strength or zeta potential of the initial suspension. High ionic strengths and low absolute zeta potential values lead to spherical morphologies. A model based on the calculations of DLVO potentials has been implemented to extract a critical pressure, which provides a ...

  11. Protein fouling in carbon nanotubes enhanced ultrafiltration membrane: Fouling mechanism as a function of pH and ionic strength

    KAUST Repository

    Lee, Jieun

    2016-11-04

    The protein fouling behavior was investigated in the filtration of the multiwall carbon nanotube (MWCNT) composite membrane and commercial polyethersulfone ultrafiltration (PES-UF) membrane. The effect of solution chemistry such as pH and ionic strength on the protein fouling mechanism was systematically examined using filtration model such as complete pore blocking, intermediate pore blocking and cake layer formation. The results showed that the initial permeate flux pattern and fouling behavior of the MWCNT composite membrane were significantly influenced by pH and ionic strength while the effect of PES-UF membrane on flux was minimal. In a lysozyme (Lys) filtration, the severe pore blocking in the MWCNT membrane was made by the combined effect of intra-foulant interaction (Lys-Lys) and electrostatic repulsion between the membrane surface and the foulant at pH 4.7 and 10.4, and increasing ionic strength where the foulant-foulant interaction and membrane-fouling interaction were weak. In a bovine serum albumin (BSA) filtration, severe pore blocking was reduced by less deposition via the electrostatic interaction between the membrane and foulant at pH 4.7 and 10.4 and increasing ionic strength, at which the interaction between the membrane and BSA became weak. For binary mixture filtration, the protein fouling mechanism was more dominantly affected by foulant-foulant interaction (Lys-BSA, Lys-Lys, and BSA-BSA) at pH 7.0 and increase in ionic strength. This research demonstrates that MWCNT membrane fouling can be alleviated by changing pH condition and ionic strength based on the foulant-foulant interaction and the electrostatic interaction between the membrane and foulant.

  12. Microfludic device for creating ionic strength gradients over DNA microarrays for efficient DNA melting studies and assay development

    DEFF Research Database (Denmark)

    Petersen, Jesper; Poulsen, Lena; Birgens, Henrik

    2009-01-01

    is to use a thermal gradient and information from melting curves, for instance to score genotypes. However, application of temperature gradients normally requires complicated equipment, and the size of the arrays that can be investigated is restricted due to heat dissipation. Here we present a simple...... microfluidic device that creates a gradient comprising zones of defined ionic strength over a glass slide, in which each zone corresponds to a subarray. Using this device, we demonstrated that ionic strength gradients function in a similar fashion as corresponding thermal gradients in assay development. More...

  13. High-Strength Composite Fibers from Cellulose-Lignin Blends Regenerated from Ionic Liquid Solution.

    Science.gov (United States)

    Ma, Yibo; Asaadi, Shirin; Johansson, Leena-Sisko; Ahvenainen, Patrik; Reza, Mehedi; Alekhina, Marina; Rautkari, Lauri; Michud, Anne; Hauru, Lauri; Hummel, Michael; Sixta, Herbert

    2015-12-07

    Composite fibres that contain cellulose and lignin were produced from ionic liquid solutions by dry-jet wet spinning. Eucalyptus dissolving pulp and organosolv/kraft lignin blends in different ratios were dissolved in the ionic liquid 1,5-diazabicyclo[4.3.0]non-5-enium acetate to prepare a spinning dope from which composite fibres were spun successfully. The composite fibres had a high strength with slightly decreasing values for fibres with an increasing share of lignin, which is because of the reduction in crystallinity. The total orientation of composite fibres and SEM images show morphological changes caused by the presence of lignin. The hydrophobic contribution of lignin reduced the vapour adsorption in the fibre. Thermogravimetric analysis curves of the composite fibres reveal the positive effect of the lignin on the carbonisation yield. Finally, the composite fibre was found to be a potential raw material for textile manufacturing and as a precursor for carbon fibre production. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Autotrophic denitrification in microbial fuel cells treating low ionic strength waters.

    Science.gov (United States)

    Puig, Sebastià; Coma, Marta; Desloover, Joachim; Boon, Nico; Colprim, Jesús; Balaguer, M Dolors

    2012-02-21

    The presence of elevated concentrations of nitrates in drinking water has become a serious concern worldwide. The use of autotrophic denitrification in microbial fuel cells (MFCs) for waters with low ionic strengths (i.e., 1000 μS·cm(-1)) has not been considered previously. This study evaluated the feasibility of MFC technology for water denitification and also identified and quantified potential energy losses that result from their usage. The low conductivity (water limited the nitrogen removal efficiency and power production of MFCs and led to the incomplete reduction of nitrate and the nitrous oxide (N(2)O) production (between 4 and 20% of nitrogen removed). Cathodic overpotential was identified as the main energy loss factors (83-90% of total losses). That high overpotential was influenced by denitrification intermediates (NO(2)(-) and N(2)O) and the potential used by microorganisms for growth, activation, and maintenance.

  15. Variation of stability constants of thorium citrate complexes with ionic strength

    Energy Technology Data Exchange (ETDEWEB)

    Choppin, G.R. [Dept. of Chemistry, Florida State Univ., Tallahassee, FL (United States); Erten, H.N. [Dept. of Chemistry, Florida State Univ., Tallahassee, FL (United States); Xia Yuanxian

    1996-12-31

    Citrate is among the organic anions which are expected to be present in the wastes planned for deposition in the WIPP repository. In this study, a solvent extraction method has been used to measure the stability constants of Th(IV) with citrate anions in aqueous solutions with (a) NaClO{sub 4} and (b) NaCl as the background electrolytes. The ionic strengths were varied up to 5 m (NaCl) and 14 m (NaClO{sub 4}). The data from the NaClO{sub 4} solutions at varying pH values were used to calculate thermodynamic stability constants through the use of Specific ion interaction theory (SIT). (orig.)

  16. Mechanical strength and ionic conductivity of polymer electrolyte membranes prepared from cellulose acetate-lithium perchlorate

    Science.gov (United States)

    Sudiarti, T.; Wahyuningrum, D.; Bundjali, B.; Made Arcana, I.

    2017-07-01

    The need for secondary batteries is increasing every year. The secondary battery using a liquid electrolyte has some weaknesses. A solid polymer electrolyte is the alternative electrolytes developed to replace the liquid electrolyte type. This study was conducted to determine the effect of lithium perchlorate content on the polymer electrolyte membranes of cellulose acetate-LiClO4. The cellulose acetate-LiClO4 membranes were prepared by mixing cellulose acetate and LiClO4 in various compositions using tetrahydrofurane (THF) as solvent. The effect of LiClO4 ratios on the polymer electrolyte membranes was studied by analysis of the functional groups using FTIR (Fourier Transform Infrared) spectroscopy measurement, the ionic conductivity by EIS (Electrochemical Impedance Spectroscopy) method, and mechanical properties by tensile tester measurements. The ionic conductivity of the membranes increased with the increasing in the ratios of lithium perchlorate content in the membranes and reached the optimum value at 1.79×10-4 S cm-1 corresponded to the cellulose acetate doped with 25% (w/w) LiClO4 membrane. The presence of 10% (w/w) LiClO4 content within cellulose acetate membranes can increase the mechanical properties of the membranes from 19.89 to 43.29 MPa for tensile strength, and from 2.55 to 4.53% for elongation at break. However, when the cellulose acetate membranes containing ratio of LiClO4 more than 10% (w/w), consequently the tensile strength tended to decrease and the elongation at break was increased.

  17. Effect of ionic strength on complexation of Pu(IV) with humic acid

    Energy Technology Data Exchange (ETDEWEB)

    Szabo, G.; Guezi, J. [National Research Inst. for Radiobiology and Radiohygiene, Budapest (Hungary); Reiller, P. [Commissariat a l' Energie Atomique, CE Saclay, Nuclear Energy Div./DPC/SECR, Lab. de Speciation des Radionucleides et des Molecules, Gif-sur-Yvette (France); Miyajima, T. [Dept. of Chemistry, Saga Univ. (Japan); Bulman, R.A. [Radiation Protection Div., Health Protection Agency, Chilton, Didcot (United Kingdom)

    2010-07-01

    Successful geochemical modelling of the migration of radioactive materials, such as the transuranic elements, from nuclear waste repositories is dependent upon an understanding of their interaction with biogeopolymers such as humic acids, the most likely complexing agents in groundwaters. An established silica/humic acid composite has been evaluated as a model substrate for naturally occurring humate-coated minerals that are likely to be present in the vicinity of the repositories. The binding of Pu(IV), the highly likely oxidation station, by the silica/humic substrate was examined at pH 4 in the range 0.02 to 3.00 M NaClO{sub 4} by the titration method. Pu(IV)-humate conditional stability constants have been evaluated from data obtained from these experiments by using non-linear regression of binding isotherms. The results have been interpreted in terms of complexes of 1: 1 stoichiometry. Analysis of the complex formation dependency with ionic strength shows that the effect of ionic strength on humate complexation of Pu(IV) is not dramatically pronounced. The complexation constants are evaluated for the humate interaction with Pu{sup 4-} and Pu(OH){sub 3}{sup +}, at pH 4. The complexation constants are found, respectively, to be log{sup HA}{beta}{sup 0}(Pu{sup 4+}) = 16.6 {+-} 0.3 and log{beta}{sup 0}{sub 1.3.1} = 46.6 {+-} 2.3. The estimations through analogy from previous results a are in agreement with these new experimental data (orig.)

  18. Inhibition of hyaluronan hydrolysis catalysed by hyaluronidase at high substrate concentration and low ionic strength.

    Science.gov (United States)

    Astériou, Trias; Vincent, Jean-Claude; Tranchepain, Frédéric; Deschrevel, Brigitte

    2006-04-01

    Hyaluronidase and high levels of hyaluronan are found together in tumours. It is highly likely that hyaluronidase activity controls the balance between high molecular mass hyaluronan and oligosaccharides, and thus plays an important role in cancer development. The hyaluronan hydrolysis catalysed by bovine testicular hyaluronidase was studied as a model. The kinetics was investigated at pH 5 and 37 degrees C using the colorimetric N-acetyl-d-glucosamine reducing end assay method. While the substrate dependence obtained in the presence of 0.15 mol L(-1) ionic strength exhibited a Michaelis-Menten behaviour, an atypical behaviour was observed under low ionic strength: for increasing hyaluronan concentrations, the initial reaction rate increased, reached a maximum and then decreased to a very low level, close to zero at high substrate concentrations. One of the various hypotheses examined to explain this atypical behaviour is the formation of non-specific complexes between hyaluronan and hyaluronidase based on electrostatic interactions. This hypothesis is the only one that can explain all the experimental results including the variation of the reaction medium turbidity as a function of time and the influence on the initial reaction rate of the hyaluronan concentration over hyaluronidase concentration. However, phenomena such as the high viscosity of highly concentrated hyaluronan solutions or the steric exclusion of hyaluronidase from hyaluronan solutions may contribute to the atypical behaviour. Finally, the biological implications of the non-linear and non-monotonous shape of the hyaluronan-hyaluronidase substrate dependence in the regulation of the hyaluronan chain molecular mass are discussed, in particular in the case of cancer development.

  19. Ionic strength dependence of the oxidation of SO2 by H2O2 in sodium chloride particles

    Science.gov (United States)

    Ali, H. M.; Iedema, M.; Yu, X.-Y.; Cowin, J. P.

    2014-06-01

    The reaction of sulfur dioxide and hydrogen peroxide in the presence of deliquesced (>75% RH) sodium chloride (brine) particles was studied by utilizing a cross flow mini-reactor. The reaction kinetics were followed by observing chloride depletion in particles by computer-controlled scanning electron microscope with energy dispersive X-ray analysis, namely CCSEM/EDX. The reactions take place in concentrated mixed salt brine aerosols, for which no complete kinetic equilibrium data previously existed. We measured the Henry's law solubility of H2O2 in brine solutions to close that gap. We also calculated the reaction rate as the particle transforms continuously from concentrated NaCl brine to, eventually, a mixed NaHSO4 plus H2SO4 brine solution. The reaction rate of the SO2 oxidation by H2O2 was found to be influenced by the change in ionic strength as the particle undergoes compositional transformation, following closely the dependence of the third order rate constant on ionic strength as predicted using established rate equations. This is the first study that has measured the ionic strength dependence of sulfate formation (in non-aqueous media) from oxidation of mixed salt brine aerosols in the presence of H2O2. It also gives the first report of the dependence of the Henry's law constant of H2O2 on ionic strength.

  20. Force spectroscopy unravels the role of ionic strength on DNA-cisplatin interaction: Modulating the binding parameters

    Science.gov (United States)

    Oliveira, L.; Rocha, M. S.

    2017-09-01

    In the present work we have gone a step forward in the understanding of the DNA-cisplatin interaction, investigating the role of the ionic strength on the complexes formation. To achieve this task, we use optical tweezers to perform force spectroscopy on the DNA-cisplatin complexes, determining their mechanical parameters as a function of the drug concentration in the sample for three different buffers. From such measurements, we determine the binding parameters and study their behavior as a function of the ionic strength. The equilibrium binding constant decreases with the counterion concentration ([Na]) and can be used to estimate the effective net charge of cisplatin in solution. The cooperativity degree of the binding reaction, on the other hand, increases with the ionic strength, as a result of the different conformational changes induced by the drug on the double-helix when binding under different buffer conditions. Such results can be used to modulate the drug binding to DNA, by appropriately setting the ionic strength of the surrounding buffer. The conclusions drawn provide significant new insights on the complex cooperative interactions between the DNA molecule and the class of platinum-based compounds, much used in chemotherapies.

  1. Thermodynamics for proton binding of phytate in KNO{sub 3(aq)} at different temperatures and ionic strengths

    Energy Technology Data Exchange (ETDEWEB)

    Bretti, Clemente; De Stefano, Concetta, E-mail: cdestefano@unime.it; Lando, Gabriele; Sammartano, Silvio

    2013-08-20

    Highlights: • Protonation data were modeled in a wide range of temperatures and ionic strengths. • Protonation values decrease with increasing ionic strength and temperature. • In KNO{sub 3} proton binding process is slightly exothermic, but less than in NaCl. • The major contribution for the proton association is entropic in nature. • Results are in agreement with previous findings for KCl and NaCl. - Abstract: Potentiometric measurements were performed in KNO{sub 3(aq)}, to determine the apparent protonation constants of phytate at different temperatures (278.15 ≤ T (K) ≤ 323.15) and ionic strengths (0.25 ≤ I (mol) dm{sup −3} ≤ 3.0) values. In general, the protonation constants decrease with increasing both temperature and ionic strength. The data reported were critically compared with previous results obtained in KCl and the values are in a good agreement, considering the experimental errors and slight differences between the activity coefficients of the various species in KCl and KNO{sub 3}. Experimental data were then modeled as a function of temperature and ionic strength using, with comparable results, two approaches: the extended Debye–Hückel equation and the specific ion interaction theory (SIT). The single specific ion interaction coefficients, ε, were also determined. The corresponding values are higher than those in Na{sup +} media. The protonation constants were also analyzed considering a simplified weak interaction model using an empirical equation that contains an additional term which takes into account the formation of weak complexes. The results obtained for the modeling of the protonation constants are in agreement with the literature findings. Thermodynamic protonation parameters were also obtained at different temperatures and ionic strengths. The proton association process is slightly exothermic and the enthalpic contribution is less negative than that in NaCl solution. As observed in other cases for phytate anion, the

  2. Low absorption state of phycocyanin from Acaryochloris marina antenna system: On the interplay between ionic strength and excitonic coupling

    Science.gov (United States)

    Nganou, Collins

    2013-07-01

    This paper studies the excitonic factor in the excited state energy transfer of phycobilisome (PBS) by using a polarized time-resolved pump-probe and by changing the ionic strength of the cofactors' medium in the PBS of Acaryochloris marina (A. marina). As a result, the interplay between the surrounding medium and the closely excited adjacent cofactors is shown to be a negligible factor of the excitonic decay kinetics at 618 nm of the phycocyanin (PC), while it appears as a driving factor of an increase in excitonic delocalization at 630 nm. The obtained anisotropy values are consistent with the contribution of ionic strength in the excitonic mechanism in PBS. These values were 0.38 in high ionic strength and 0.4 in low ionic strength at 618 nm, and 0.52 in high ionic strength and 0.4 in low ionic strength at 630-635 nm. The anisotropy value of 0.52 in high phosphate is similar at 630 nm and 635 nm, which is consistent with an excitonic delocalization band at 635 nm. The 635 nm band is suggested to show the true low energy level of PC in A. marina PBS. The anisotropy decay kinetic at 630 nm suggests that the excited state population of PC is not all equilibrated in 3 ps because of the existence of the 10 ps decay kinetic component. The presence of the slow kinetic decay component in high, and low ionic strength, is consistent with a 10 and 14 ps energy transfer pathway, while the 450 fs kinetic decay component is consistent with the presence of an additional excitation energy transfer pathway between adjacent α84 and β84. Furthermore, the 450 fs decay kinetic is suggested to be trapped in the trimer, while the 400 fs decay kinetic rules out an excitonic flow from low energy level PC to allophycoyanin. This excitonic flow may occur between β84 in adjacent trimers, towards the low energy state of the PBS rod.

  3. Particle Deposition Kinetics of Colloidal Suspensions in Microchannels at High Ionic Strength.

    Science.gov (United States)

    Cejas, Cesare M; Monti, Fabrice; Truchet, Marine; Burnouf, Jean-Pierre; Tabeling, Patrick

    2017-07-05

    Despite its considerable practical importance, the deposition of real Brownian particles transported in a channel by a liquid, at small Reynolds numbers, has never been described at a comprehensive level. Here, by coupling microfluidic experiments, theory, and numerics, we succeed in unravelling the problem for the case of straight channels at high salinity. We discover a broad regime of deposition (the van der Waals regime) in which particle-wall van der Waals interactions govern the deposition mechanism. We determine the range of existence of the regime, for which we calculate the concentration profiles, retention profiles, and deposition kinetics analytically. The retention profiles decay as the inverse of the square root of the distance from the entry, and the deposition kinetics are given by the expression [Formula: see text], where S is a dimensionless deposition function, A is the Hamaker constant, and ξL is a dimensionless parameter characterizing fluid flow properties. These findings are well supported by numerics. Experimentally, we find that the retention profiles behave as x-0.5±0.1 (where x is the distance from the channel entry) over three decades in scale, as predicted theoretically. By varying the flow conditions (speed, geometry, surface properties, and concentration) so as to cover four decades in ξL and taking the Hamaker constant as a free parameter, we accurately confirm the theoretical expression for the deposition kinetics. Operating in the van der Waals regime enables control of the deposition rates via surface chemistry. From a surface science perspective, working in the van der Waals regime enables us to measure the Hamaker constants of thousands of particles in a few minutes, a task that would take a much longer time to perform with standard AFM.

  4. Boron Adsorption on Muscovite Mineral as a Function of pH, Ionic strength of Solution and Kinds of Cation

    Directory of Open Access Journals (Sweden)

    F. Zareapour Rafsanjani

    2016-02-01

    boron adsorption isotherm, after 10 ml 0.01 M of Ca(NO32 was transferred into 15 ml centrifuge tubes, 0.1 g sample of muscovite was added to obtain adsorbent concentration of 10 g L-1. Then a predetermined amount of boron from the stock solution was added to give final concentration range between 1 and 15 mg B per liter. Initial pH of the solution was adjusted to 8.2 ± 0.1 by predetermined amount of 0.03 M NaOH solution. Suspensions were then shaken for 24h. At the end of equilibrium time, final pH was measured in the suspensions and the tubes were then centrifuged for 10 min at 5000 g. Half of the supernatant volume (5 mL was pipetted out from each tube and then B in the supernatants were measured using the colorimetric Azomethin-H method. The amount of B adsorbed on the adsorbent was calculated as the difference between the B concentration in the blanks and the concentration in the solution after equilibration. Chemical species in the solutions were also predicted using Visual MINTEQ, a chemical speciation program developed to simulate equilibrium processes in aqueous systems. Results and Discussion: The effect of pH on the amount of B retained depended on the initial B concentration. The amount of boron adsorption increased with increasing equilibrium pH. Boron adsorption on muscovite increased with increasing ionic strength. Greater adsorption was observed in the presence of Mg2+ as compared with Ca2+ at the same ionic strength. Calculations using Vminteq showed that the concentration of Mg-borate ion pairs (MgH2BO3+ were higher than the concentration of Ca and Na-borate ion pairs (CaH2BO3+ and NaH2BO3°. It thus seems that the much greater loss of B from solution observed in the Mg system was caused by Mg-borate ion pair adsorption. Sorption isotherm of B were well described by the Freundlich, Langmuir and Sips models but the Sips sorption model describes the interaction between B and the mineral better than the Langmuir model. On the basis of n value of

  5. Formation of Aqueous Suspensions of Fullerenes

    Science.gov (United States)

    Colloidal suspensions of C60, C70 and a derivative of C60, PCBM ([6,6]-Phenyl C61-butyric acid methyl ester) were produced by extended mixing in water. We examined the contribution of background solution chemistry (pH, ionic strength) on the formation kinetics of colloidal suspe...

  6. Influence of ionic strength and beta2-glycoprotein I concentration on agglutination of like-charged phospholipid membranes.

    Science.gov (United States)

    Perutková, Šárka; Frank-Bertoncelj, Mojca; Rozman, Blaž; Kralj-Iglič, Veronika; Iglič, Aleš

    2013-11-01

    The effect of ionic strength on adhesion between negatively charged giant unilamellar vesicles induced by beta2-glycoprotein I (β2-GPI) was studied experimentally and theoretically. Measuring the effective angle of contact between adhering vesicles indicated that the strength of adhesion between vesicles decreases with increasing ionic strength, and increases with concentration of β2-GPI. In the theoretical part we focused on the study of the average orientation of β2-GPI near the charged membrane and its role in mediating the attractive interactions between the vesicles. β2-GPI proteins were modelled as rods with internal distribution of electric charge. The predictions of Monte Carlo simulations show orthogonal orientation of some of the membrane attached β2-GPI in narrow gap between two vesicles. On the contrary, at larger distances between vesicles the proteins are parallelly attached to the membrane surface. A local minimum of the free energy corresponding to β2-GPI-mediated adhesion of two neighbouring vesicles was predicted. The strength of adhesion was confirmed to decrease at high ionic strength. Copyright © 2013 Elsevier B.V. All rights reserved.

  7. Lipid exchange and transfer on nanoparticle supported lipid bilayers: effect of defects, ionic strength, and size.

    Science.gov (United States)

    Drazenovic, Jelena; Ahmed, Selver; Tuzinkiewicz, Nicole-Marie; Wunder, Stephanie L

    2015-01-20

    Lipid exchange/transfer has been compared for zwitterionic 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 1,2-dimyristoyl-d54-sn-glycero-3-phosphocholine (DMPC) small unilamellar vesicles (SUVs) and for the same lipids on silica (SiO2) nanoparticle supported lipid bilayers (NP-SLBs) as a function of ionic strength, temperature, temperature cycling, and NP size, above the main gel-to-liquid crystal phase transition temperature, Tm, using d- and h-DMPC and DPPC. Increasing ionic strength decreases the exchange kinetics for the SUVs, but more so for the NP-SLBs, due to better packing of the lipids and increased attraction between the lipid and support. When the NP-SLBs (or SUVs) are cycled above and below Tm, the exchange rate increases compared with exchange at the same temperature without cycling, for similar total times, suggesting that defects provide sites for more facile removal and thus exchange of lipids. Defects can occur: (i) at the phase boundaries between coexisting gel and fluid phases at Tm; (ii) in bare regions of exposed SiO2 that form during NP-SLB formation due to mismatched surface areas of lipid and NPs; and (iii) during cycling as the result of changes in area of the lipids at Tm and mismatched thermal expansion coefficient between the lipids and SiO2 support. Exchange rates are faster for NP-SLBs prepared with the nominal amount of lipid required to form a NP-SLB compared with NP-SLBs that have been prepared with excess lipids to minimize SiO2 patches. Nanosystems prepared with equimolar mixtures of NP-SLBs composed of d-DMPC (d(DMPC)-NP-SLB) and SUVs composed of h-DMPC (h(DMPC)-SUV) show that the calorimetric transition of the "donor" h(DMPC)-SUV decreases in intensity without an initial shift in Tm, indicating that the "acceptor" d(DMPC)-NP-SLB can accommodate more lipids, through either further fusion or insertion of lipids into the distal monolayer. Exchange for d/h(DMPC)-NP-SLB is in the order 100 nm SiO2 > 45 nm SiO2 > 5 nm SiO2.

  8. Unusual Volumetric Response of Human Red Blood Cells under Low Ionic Strength Conditions

    Directory of Open Access Journals (Sweden)

    Sergey V. Rudenko, PhD¹

    2013-06-01

    Full Text Available Human red blood cells (RBCs when suspended in a Low Ionic Strength medium (LIS demonstrate characteristic triphasic shape changes (morphological response, MR and become reduced in volume. Tahitian Tabari Noni juice (Tb, after being given during the terminal phase of MR, was shown to initiate an unusual cell response. This response can be described as a volumetric four-phasic response including first a shrinking phase, attributed to the initial sucrose-induced shrinkage during typical MR, a rapid first swelling phase, induced by application of the juice, followed spontaneously by the occurrence of a more prolonged second shrinking phase, which culminated in the swelling and hemolysis of the cells. All the phases of volumetric response can be independently regulated by chloride, DIDS, cations Ca2+, Ag+, Hg2+ or plasma. The second shrinking phase is not inhibited by clotrimazole, a known inhibitor of Gardos channels, and can be replicated by a mixture of two ionophores (valinomycin and CCCP, suggesting the involvement of the putative K+/H+ exchanger as a mechanism of this phase. We suggest that the erythrocyte membrane is equipped with additional molecular systems, poorly characterized at present, that regulate the cell shape and volume. The cell should, therefore, be considered as an “active” responsive system instead of a “passive” osmometer-like structure.

  9. Enhanced granulation by natural ionic polymer additives in UASB reactor treating low-strength wastewater.

    Science.gov (United States)

    Tiwari, Manoj K; Guha, Saumyen; Harendranath, C S; Tripathi, Shweta

    2005-10-01

    Effect of natural ionic polymer additives on granulation in lab-scale UASB reactors treating low-strength synthetic wastewater (COD 750-850 mg/L) was examined. The organic loading rate was 1.477+/-0.118 kgCOD/m3/day. Under identical conditions four similar reactors were operated in parallel with the following additives: control with no additive, anionic part of Reetha (Sapindus trifoliata) extract, cationic part of Reetha extract, and Chitosan. By the end of the study period, Chitosan as an additive produced largest granules with mean size of 0.15 mm closely followed by the cationic fraction of the Reetha extract with mean size of 0.144 mm, and anionic fractions of the Reetha extract with 0.139 mm. Control reactor with no additives had the smallest size granules with mean size of 0.128 mm. The fraction of granules in the sludge bed of size >0.1 mm showed similar trend. The largest granule size observed in the reactors with additives was 4-5mm as compared to 2 mm in the control reactor. Cationic polymers were more effective additives for enhancing sludge granulation. Exo-cellular protein, lipid, sugar and total polymer increased with granulation in the reactors. A COD removal efficiency of 95-98% was achieved in all the reactors.

  10. Kinetic features of metal complexes with polysaccharide colloids: impact of ionic strength.

    Science.gov (United States)

    Rotureau, Elise; van Leeuwen, Herman P

    2009-11-19

    The dynamic features of metal binding by a gel-like polysaccharide, carboxymethyldextran (CMD), are investigated by stripping chronopotentiometry (SCP). This technique measures the diffusive flux properties of the metallic species in the ligand dispersion as defined by their concentration, mobility, and lability. Cadmium(II) forms only 1:1 complexes with CMD, the lability of which is well described by Eigen mechanism principles, that is, the removal of a water molecule from the inner hydration sphere of the metal ion is limiting the complex formation rate. Lead(II) and copper(II), however, also form intramolecular bidentate complexes with CMD, which requires a conformational reorganization of the polymeric chain. The reorganization process appears to be the rate-limiting step of the overall complexation reaction, which takes place on a time scale of hours. The influence of ionic strength on the rate of bidentate complex formation is insignificant. In contrast, its impact on the stability of the monodentate complex follows the corresponding Donnan potential of the soft CMD particle.

  11. Effects of temperature, pH, and ionic strength on the Henry's law constant of triethylamine

    Science.gov (United States)

    Leng, Chun-Bo; Roberts, Jason E.; Zeng, Guang; Zhang, Yun-Hong; Liu, Yong

    2015-05-01

    The Henry's law constants (KH) of triethylamine (TEA) in pure water and in 1-octanol were measured for the temperatures pertinent to the lower troposphere (278-298 K) using a bubble column system coupled to a Fourier transform infrared spectrometer. The KH values of TEA in water and 1-octanol at 298 K are 5.75 ± 0.86 mol L-1 atm-1 and 115.62 ± 5.78 mol L-1 atm-1. The KH values display strong dependence on temperature, pH, and ionic strength. The characteristic times for TEA to establish an equilibrium between gas and droplet with a size of 5.6 µm are ~33 s (298 K, pH = 5.6); ~8.9 × 102 s (278 K, pH = 5.6); ~1.3 × 103 s (298 K, pH = 4.0); and 3.6 × 104 s (278 K, pH = 4.0). The evaluation of TEA partitioning between gas phase and condensed phase implies that TEA predominantly resides in rainwater, and TEA loss to organic aerosol is negligible.

  12. Kinetics of gypsum crystal growth from high ionic strength solutions: A case study of Dead Sea - seawater mixtures

    Science.gov (United States)

    Reznik, Itay J.; Gavrieli, Ittai; Antler, Gilad; Ganor, Jiwchar

    2011-04-01

    Gypsum precipitation kinetics were examined from a wide range of chemical compositions (11Bosbach and Rammensee, 1994). Under further-away-from-equilibrium conditions, the reaction is dominated by an apparent 10th order reaction. A conceptual model for gypsum growth kinetics is presented. The model is based on the 2nd order kinetic coefficients determined in the present study and data from the literature and is valid under a wide range of ionic strengths and Ca/SO42- ratios. According to this model, the integration of SO42- to kinks on the surface of the growing crystals is the rate-limiting step in the precipitation reaction. At ionic strengths above 8.5 m the precipitation rate of gypsum is enhanced, possibly due to the formation of CaSO4° ion pairs and/or a decrease in hydration frequencies.

  13. Sorption and desorption of radiocobalt on montmorillonite-Effects of pH, ionic strength and fulvic acid

    Energy Technology Data Exchange (ETDEWEB)

    Chen Lei [School of Chemical Engineering, Shandong University of Technology, 255049 Zibo, Shandong (China)], E-mail: chenlei761205@sina.com; Lu Songsheng [New Star Institute of Applied Technology, Huangshan Road, Hefei, Anhui (China)

    2008-03-15

    Humic substances and clay minerals have been studied extensively in radioactive waste management. In our research, the sorption and desorption of radiocobalt on montmorillonite in the presence and absence of fulvic acid as a function of pH and ionic strength were investigated under ambient conditions by using batch techniques. The results indicate that the sorption of cobalt is strongly dependent on pH values and independent of ionic strength. Surface complexation rather than cation exchange is considered as the main mechanism of cobalt sorption to montmorillonite. The presence of fulvic acid enhances cobalt sorption obviously at pH values<8. The desorption behavior changes of surface-sorbed cobalt from montmorillonite were studied by decreasing pH values and the solution cobalt concentrations independently. The results indicated that the sorption of cobalt on montmorillonite is irreversible.

  14. Investigations of artificial aggregation of washed human erythrocytes caused by decreased pH and reduced ionic strength.

    Science.gov (United States)

    Lerche, D; Glaser, R

    1980-01-01

    Aggregation measurements of washed human erythrocytes were carried out in a NaCl-PBS solution under laminar shear conditions. An artificial aggregation was caused by decreased pH and reduced ionic strength, and characterized by the collision efficiency, e.m., the probability of a permanent aggregate formation. It was found that the aggregation increases reducing the ionic strength and decreasing the pH of the medium. Pretreatment with Amphothericin B did not change the aggregation. The results cannot be explained neither by the usual D.L.O.V. theory (force balance between electrostatic repulsion and attraction due to dispersion forces) nor by direct influence of the changed transmembrane potential. It is supposed that this type of aggregation involves reversible changes of the membrane and/or the surface structure.

  15. Renewable energy powered membrane technology: Impact of pH and ionic strength on fluoride and natural organic matter removal.

    Science.gov (United States)

    Owusu-Agyeman, Isaac; Shen, Junjie; Schäfer, Andrea Iris

    2018-04-15

    Real water pH and ionic strength vary greatly, which influences the performance of membrane processes such as nanofiltration (NF) and reverse osmosis (RO). Systematic variation of pH (3-12) and ionic strength (2-10g/L as total dissolved solids (TDS)) was undertaken with a real Tanzanian water to investigate how water quality affects retention mechanisms of fluoride (F) and natural organic matter (NOM). An autonomous solar powered NF/RO system driven by a solar array simulator was supplied with constant power from a generator. An open NF (NF270) and a brackish water RO (BW30) membrane were used. A surface water with a very high F (59.7mg/L) and NOM (110mgC/L) was used. Retention of F by NF270 was 80% at pH4, and about 99% at pH >5, due to the smaller pore size and hence a more dominant size exclusion. In consequence, only little impact of ionic strength increase was observed for BW30. The concentration of NOM in permeates of both NF270 and BW30 were typically <2mg/L. This was not affected by pH or ionic strength due to the fact that the bulk of NOM was rejected by both membranes through size exclusion. The research is carried out in the context of providing safe drinking water for rural and remote communities where infrastructure is lacking, and water quality varies significantly. While other studies focus on energy fluctuations, this research emphasises on feed water quality that affects system performance and may alter due to a number of environmental factors. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. The effect of pH and ionic strength of dissolution media on in-vitro release of two model drugs of different solubilities from HPMC matrices.

    Science.gov (United States)

    Asare-Addo, Kofi; Conway, Barbara R; Larhrib, Hassan; Levina, Marina; Rajabi-Siahboomi, Ali R; Tetteh, John; Boateng, Joshua; Nokhodchi, Ali

    2013-11-01

    The evaluation of the effects of different media ionic strengths and pH on the release of hydrochlorothiazide, a poorly soluble drug, and diltiazem hydrochloride, a cationic and soluble drug, from a gel forming hydrophilic polymeric matrix was the objective of this study. The drug to polymer ratio of formulated tablets was 4:1. Hydrochlorothiazide or diltiazem HCl extended release (ER) matrices containing hypromellose (hydroxypropyl methylcellulose (HPMC)) were evaluated in media with a pH range of 1.2-7.5, using an automated USP type III, Bio-Dis dissolution apparatus. The ionic strength of the media was varied over a range of 0-0.4M to simulate the gastrointestinal fed and fasted states and various physiological pH conditions. Sodium chloride was used for ionic regulation due to its ability to salt out polymers in the midrange of the lyotropic series. The results showed that the ionic strength had a profound effect on the drug release from the diltiazem HCl K100LV matrices. The K4M, K15M and K100M tablets however withstood the effects of media ionic strength and showed a decrease in drug release to occur with an increase in ionic strength. For example, drug release after the 1h mark for the K100M matrices in water was 36%. Drug release in pH 1.2 after 1h was 30%. An increase of the pH 1.2 ionic strength to 0.4M saw a reduction of drug release to 26%. This was the general trend for the K4M and K15M matrices as well. The similarity factor f2 was calculated using drug release in water as a reference. Despite similarity occurring for all the diltiazem HCl matrices in the pH 1.2 media (f2=64-72), increases of ionic strength at 0.2M and 0.4M brought about dissimilarity. The hydrochlorothiazide tablet matrices showed similarity at all the ionic strength tested for all polymers (f2=56-81). The values of f2 however reduced with increasing ionic strengths. DSC hydration results explained the hydrochlorothiazide release from their HPMC matrices. There was an increase in

  17. Dioctahedral smectite reactions at elevated temperatures: Effects of K-availability, Na/K ratio and ionic strength

    Science.gov (United States)

    Whitney, G.

    1992-01-01

    Hydrothermal experiments were conducted to measure the effects of K availability, Na/K ratio and ionic strength in chloride solutions on the rate and extent of the reaction of smectite to interstratified illite/smectite. The effect of K-content on reaction progress is dramatic at low (0.33 eq.) K concentrations, but diminishes above a concentration of 0.66 equivalents. The effect of K-content is also more important at lower temperatures than at higher temperatures. Addition of K above that required to satisfy the cation exchange capacity of the smectite reduced the amount of chlorite byproduct and produced authigenic K-feldspar at the highest K-concentration. Similar experiments were run using Na/K equivalent ratios of 0 to 25 and total solution molalities of 0 to 3.75 molal. Because these experiments were small fixed-volume experiments, it was necessary to vary two of the three key variables (K-content, Na/K ratio, ionic strength simultaneously. The data suggest, however, that K-content has a much stronger effect than either Na/K ratio or ionic strength on illitization reaction progress. ?? 1992.

  18. Experimental study of the pH, ionic strength, and reversibility behavior of bacteria-mineral adsorption

    Science.gov (United States)

    Yee, Nathan; Fein, Jeremy B.; Daughney, Christopher J.

    2000-02-01

    In this study, we investigate the adsorption of Bacillus subtilis onto the surfaces of two minerals, corundum and quartz, as a function of time, pH, ionic strength, and bacteria:mineral mass ratio. Experimental results indicate that the adsorption of bacteria onto a mineral surface is a completely reversible process with equilibrium being reached in less than 1 h. Our data also indicate that B. subtilis displays a higher affinity for corundum surfaces than for quartz surfaces, and that the extent of bacteria adsorption onto corundum increases with decreasing pH, with increasing bacteria:mineral mass ratio, and with decreasing ionic strength. The adsorption behavior is governed by the chemical speciation of the bacterial and mineral surfaces. We describe the experimental results with a chemical equilibrium model. The model accounts for hydrophobic and electrostatic interactions that occur between the bacteria and mineral surfaces, and can account for the effects of solution chemistry as well as surface speciation on the extent of adsorption. These results are the first to integrate the effects of pH, ionic strength, and bacteria:mineral ratio in a quantitative model. Such an approach enables bacteria-mineral adsorption reactions to be incorporated into more standard water-rock speciation models, providing a better understanding of mass transport in both natural and bio-engineered bacteria-bearing geochemical systems.

  19. High ionic strength narrows the population of sites participating in protein ion-exchange adsorption: a single-molecule study.

    Science.gov (United States)

    Kisley, Lydia; Chen, Jixin; Mansur, Andrea P; Dominguez-Medina, Sergio; Kulla, Eliona; Kang, Marci K; Shuang, Bo; Kourentzi, Katerina; Poongavanam, Mohan-Vivekanandan; Dhamane, Sagar; Willson, Richard C; Landes, Christy F

    2014-05-23

    The retention and elution of proteins in ion-exchange chromatography is routinely controlled by adjusting the mobile phase salt concentration. It has repeatedly been observed, as judged from adsorption isotherms, that the apparent heterogeneity of adsorption is lower at more-eluting, higher ionic strength. Here, we present an investigation into the mechanism of this phenomenon using a single-molecule, super-resolution imaging technique called motion-blur Points Accumulation for Imaging in Nanoscale Topography (mbPAINT). We observed that the number of functional adsorption sites was smaller at high ionic strength and that these sites had reduced desorption kinetic heterogeneity, and thus narrower predicted elution profiles, for the anion-exchange adsorption of α-lactalbumin on an agarose-supported, clustered-charge ligand stationary phase. Explanations for the narrowing of the functional population such as inter-protein interactions and protein or support structural changes were investigated through kinetic analysis, circular dichroism spectroscopy, and microscopy of agarose microbeads, respectively. The results suggest the reduction of heterogeneity is due to both electrostatic screening between the protein and ligand and tuning the steric availability within the agarose support. Overall, we have shown that single molecule spectroscopy can aid in understanding the influence of ionic strength on the population of functional adsorbent sites participating in the ion-exchange chromatographic separation of proteins. Copyright © 2014 Elsevier B.V. All rights reserved.

  20. Increasing the Strength of Single Filaments and Yarns of a Paraaramid Fiber by Their Processing with an Aqueous Suspension of Carbon Nanoparticles

    Science.gov (United States)

    Shebanov, S. M.; Novikov, I. K.; Gumargalieva, K. Z.; Pavlikov, A. V.

    2017-05-01

    The paper presents the results of increasing the strength and modulus of single filaments and yarns of a paraaramid fiber by their processing with an aqueous suspension of carbon nanotubes in the production process

  1. Colloid release and clogging in porous media: Effects of solution ionic strength and flow velocity.

    Science.gov (United States)

    Torkzaban, Saeed; Bradford, Scott A; Vanderzalm, Joanne L; Patterson, Bradley M; Harris, Brett; Prommer, Henning

    2015-10-01

    The release and retention of in-situ colloids in aquifers play an important role in the sustainable operation of managed aquifer recharge (MAR) schemes. The processes of colloid release, retention, and associated permeability changes in consolidated aquifer sediments were studied by displacing native groundwater with reverse osmosis-treated (RO) water at various flow velocities. Significant amounts of colloid release occurred when: (i) the native groundwater was displaced by RO-water with a low ionic strength (IS), and (ii) the flow velocity was increased in a stepwise manner. The amount of colloid release and associated permeability reduction upon RO-water injection depended on the initial clay content of the core. The concentration of released colloids was relatively low and the permeability reduction was negligible for the core sample with a low clay content of about 1.3%. In contrast, core samples with about 6 and 7.5% clay content exhibited: (i) close to two orders of magnitude increase in effluent colloid concentration and (ii) more than 65% permeability reduction. Incremental improvement in the core permeability was achieved when the flow velocity increased, whereas a short flow interruption provided a considerable increase in the core permeability. This dependence of colloid release and permeability changes on flow velocity and colloid concentration was consistent with colloid retention and release at pore constrictions due to the mechanism of hydrodynamic bridging. A mathematical model was formulated to describe the processes of colloid release, transport, retention at pore constrictions, and subsequent permeability changes. Our experimental and modeling results indicated that only a small fraction of the in-situ colloids was released for any given change in the IS or flow velocity. Comparison of the fitted and experimentally measured effluent colloid concentrations and associated changes in the core permeability showed good agreement, indicating that the

  2. Ionic strength assay via polyacrylate-ferriferrous oxide magnetic photonic crystals.

    Science.gov (United States)

    Li, Yan-Ran; Sun, Ye; Wang, He-Fang

    2015-05-21

    Convenient reading out and/or determination of ionic strength (IS) is of great significance for both scientific research and real life applications. We presented here a novel method for the rapid and sensitive IS assay based on the electrolyte-induced sensitive wavelength blueshifts of the reflection spectra of polyacrylate capped Fe3O4 magnetic photonic crystals (PA-Fe3O4-MPCs). For HCl, MgSO4 and the common electrolytes corresponding to the salinity of seawater (including NaCl, KCl, MgCl2, CaCl2, Na2SO4 and their mixtures), the PA-Fe3O4-MPCs displayed wavelength blueshifts identical to the total IS of the aqueous solutions, regardless of the kind of above-mentioned electrolytes in the solutions. Besides, the PA-Fe3O4-MPCs exhibited relatively high sensitivity (an average of 294 nm L mmol(-1) in the range of 0.05-0.30 mmol L(-1), and an even higher value of 386 nm L mmol(-1) at 0.05-0.15 mmol L(-1)) and fast response (within 8 s) to the IS of aqueous solutions. The relative standard deviation (RSD) for IS (NaCl, 0.1 mmol L(-1)) was 4.4% (n = 5). The developed method was applied to determine the salinity of seawater samples, and the determined results were validated by the traditional standard chlorinity titration and electric conductimetry method. The recoveries were in the range of 92-104%. The proposed PA-Fe3O4-MPCs based reflectometry method would have great potential for IS and salinity assays.

  3. Temperature and ionic strength effects on the chlorosome light-harvesting antenna complex.

    Science.gov (United States)

    Tang, Kuo-Hsiang; Zhu, Liying; Urban, Volker S; Collins, Aaron M; Biswas, Pratim; Blankenship, Robert E

    2011-04-19

    Chlorosomes, the peripheral light-harvesting antenna complex from green photosynthetic bacteria, are the largest and one of the most efficient light-harvesting antenna complexes found in nature. In contrast to other light-harvesting antennas, chlorosomes are constructed from more than 150,000 self-assembled bacteriochlorophylls (BChls) and contain relatively few proteins that play secondary roles. These unique properties have led to chlorosomes as an attractive candidate for developing biohybrid solar cell devices. In this article, we investigate the temperature and ionic strength effects on the viability of chlorosomes from the photosynthetic green bacterium Chloroflexus aurantiacus using small-angle neutron scattering and dynamic light scattering. Our studies indicate that chlorosomes remain intact up to 75 °C and that salt induces the formation of large aggregates of chlorosomes. No internal structural changes are observed for the aggregates. The salt-induced aggregation, which is a reversible process, is more efficient with divalent metal ions than with monovalent metal ions. Moreover, with treatment at 98 °C for 2 min, the bulk of the chlorosome pigments are undamaged, while the baseplate is destroyed. Chlorosomes without the baseplate remain rodlike in shape and are 30-40% smaller than with the baseplate attached. Further, chlorosomes are stable from pH 5.5 to 11.0. Together, this is the first time such a range of characterization tools have been used for chlorosomes, and this has enabled elucidation of properties that are not only important to understanding their functionality but also may be useful in biohybrid devices for effective light harvesting. © 2011 American Chemical Society

  4. Temperature and Ionic Strength Effects on the Chlorosome Light-Harvesting Antenna Complex

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Kuo-Hsiang [Washington Univ., St. Louis, MO (United States); Zhu, Liying [Washington Univ., St. Louis, MO (United States); Urban, Volker S [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Collins, Aaron M. [Washington Univ., St. Louis, MO (United States); Biswas, Pratim [Washington Univ., St. Louis, MO (United States); Blankenship, R. E. [Washington Univ., St. Louis, MO (United States)

    2011-03-15

    Chlorosomes, the peripheral light-harvesting antenna complex from green photosynthetic bacteria, are the largest and one of the most efficient light-harvesting antenna complexes found in nature. In contrast to other light-harvesting antennas, chlorosomes are constructed from more than 150,000 self-assembled bacteriochlorophylls (BChls) and contain relatively few proteins that play secondary roles. These unique properties have led to chlorosomes as an attractive candidate for developing biohybrid solar cell devices. In this article, we investigate the temperature and ionic strength effects on the viability of chlorosomes from the photosynthetic green bacterium Chloroflexus aurantiacus using small-angle neutron scattering and dynamic light scattering. Our studies indicate that chlorosomes remain intact up to 75 °C and that salt induces the formation of large aggregates of chlorosomes. No internal structural changes are observed for the aggregates. The salt-induced aggregation, which is a reversible process, is more efficient with divalent metal ions than with monovalent metal ions. Moreover, with treatment at 98 °C for 2 min, the bulk of the chlorosome pigments are undamaged, while the baseplate is destroyed. Chlorosomes without the baseplate remain rodlike in shape and are 30-40% smaller than with the baseplate attached. Further, chlorosomes are stable from pH 5.5 to 11.0. Together, this is the first time such a range of characterization tools have been used for chlorosomes, and this has enabled elucidation of properties that are not only important to understanding their functionality but also may be useful in biohybrid devices for effective light harvesting.

  5. Temperature and Ionic Strength Effects on the Chlorosome Light-Harvesting Antenna Complex

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Kuo-Hsiang [Washington Univ., St. Louis, MO (United States). Dept. of Biology and Dept. of Chemistry; Zhu, Liying [Washington Univ., St. Louis, MO (United States). Aerosol and Air Quality Research Lab., Dept. of Energy, Environmental and Chemical Engineering; Urban, Volker S. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Structural Molecular Biology (CSMB); Collins, Aaron M. [Washington Univ., St. Louis, MO (United States). Dept. of Biology and Dept. of Chemistry; Biswas, Pratim [Washington Univ., St. Louis, MO (United States). Aerosol and Air Quality Research Lab., Dept. of Energy, Environmental and Chemical Engineering; Blankenship, Robert E. [Washington Univ., St. Louis, MO (United States). Dept. of Biology and Dept. of Chemistry

    2011-03-15

    Chlorosomes, the peripheral light-harvesting antenna complex from green photosynthetic bacteria, are the largest and one of the most efficient light-harvesting antenna complexes found in nature. In contrast to other light-harvesting antennas, chlorosomes are constructed from more than 150,000 self-assembled bacteriochlorophylls (BChls) and contain relatively few proteins that play secondary roles. These unique properties have led to chlorosomes as an attractive candidate for developing biohybrid solar cell devices. In this article, we investigate the temperature and ionic strength effects on the viability of chlorosomes from the photosynthetic green bacterium Chloroflexus aurantiacus using small-angle neutron scattering and dynamic light scattering. Our studies indicate that chlorosomes remain intact up to 75 °C and that salt induces the formation of large aggregates of chlorosomes. No internal structural changes are observed for the aggregates. The salt-induced aggregation, which is a reversible process, is more efficient with divalent metal ions than with monovalent metal ions. Moreover, with treatment at 98 °C for 2 min, the bulk of the chlorosome pigments are undamaged, while the baseplate is destroyed. Chlorosomes without the baseplate remain rodlike in shape and are 30-40% smaller than with the baseplate attached. Further, chlorosomes are stable from pH 5.5 to 11.0. In conclusion, together, this is the first time such a range of characterization tools have been used for chlorosomes, and this has enabled elucidation of properties that are not only important to understanding their functionality but also may be useful in biohybrid devices for effective light harvesting.

  6. Improving the strength of ceramics by controlling the interparticle forces and rheology of the ceramic suspensions

    CERN Document Server

    Chou, Y P

    2001-01-01

    This thesis describes a study of the modification of the interparticle forces of colloidal ceramic particles in aqueous suspensions in order to improve the microstructural homogeneity, and hence the reliability and mechanical performances, of subsequently formed ceramic compacts. A concentrated stable fine ceramic powder suspension has been shown to be able to generate a higher density of a ceramic product with better mechanical, and also electrical, electrochemical and optical, properties of the ceramic body. This is because in a colloidally stable suspension there are no aggregates and so defect formation, which is responsible for the ceramic body performance below its theoretical maximum, is reduced. In order to achieve this, it is necessary to form a well dispersed ceramic suspension by ensuring the interparticle forces between the particles are repulsive, with as a high a loading with particles as possible. By examining the rheological behaviour and the results of Atomic Force Microscope, the dispersion ...

  7. Functionality of myofibrillar proteins as affected by pH, ionic strength and heat treatment - a low-field NMR study.

    Science.gov (United States)

    Bertram, Hanne Christine; Kristensen, Mette; Andersen, Henrik Jørgen

    2004-10-01

    Myofibrills were extracted from porcine muscle, and their water properties were characterized using low-field nuclear magnetic resonance (NMR) T(2) relaxometry. A T(2) relaxation pattern very similar to the pattern observed in intact meat and water contents comparable to the water content in meat were observed, implying that the myofibrillar structures are responsible for retaining the majority of water in meat. The effect of pH and ionic strength in the samples was investigated as pH was adjusted to 5.4, 6.2, and 7.0 and ionic strength to 0.29, 0.46 and 0.71 M, respectively. Even though there were interactions between pH and ionic strength, the water content in the samples increased significantly with increasing pH and ionic strength. Moreover, mean T(2) relaxation times likewise increased with increasing pH and ionic strength, which reveals that the increased water retention could be ascribed to a swelling of the myofibrils and thereby increased spacing between filaments. The present study demonstrates that NMR T(2) relaxometry is a potential tool to explore how processing factors such as pH and ionic strength affect the microstructure of meat.

  8. Hysteresis in the amount of colloids mobilized from intact cores of a fractured soil as a result of changes in the ionic strength of simulated rainfall

    Science.gov (United States)

    Mohanty, S.; Ryan, J. N.; Saiers, J. E.

    2010-12-01

    Understanding the mechanisms of colloid mobilization is essential to predicting the importance of colloid-facilitated transport of contaminants in subsurface environment. The mobilization of colloids increases with a decrease in the ionic strength of the pore water. Colloid mobilization is hysteretic in response to changes in ionic strength - the amount of colloids mobilized at a given ionic strength is not matched when the experiment is repeated following exposure to pore water of higher or lower ionic strengths. An exchange of pore water between the soil matrix and macropores is proposed to be the primary reason for the hysteresis of colloid mobilization during changes in ionic strength. The mobilization of colloids by pore water of a given ionic strength is either enhanced or inhibited by the slow release of matrix pore water of a lower or higher ionic strengths, respectively. This hypothesis was tested by conducting simulated rainfall experiments on undisturbed, intact cores of fractured soil (25.4 cm diameter, 15.2 cm depth) sampled from Oak Ridge National Laboratory, Tennessee. Rainfall of increasing, and then decreasing, ionic strength was applied to soil cores in successive events of 6 h of rainfall and an 18 h pause for each ionic strength. The ionic strength ranged from 0.01 to 10 mM as sodium chloride. Sodium bromide was included to provide a conservative tracer (Br-). Samples were collected from 19 ports in a hexagonal grid at the base of the soil core to identify regions of fast and slow flow attributed to macropore and matrix pathways. The samples were analyzed for concentrations of colloids (turbidity) and bromide (ion-selective electrode), conductivity, and pH. A flow-interruption method during bromide injection was employed to estimate the mass transfer rate of bromide between the soil macropores and matrix. Colloid concentrations, flow rates, and breakthrough times for bromide were found to be different for each port in the experiments at

  9. Stability of YREE complexes with the trihydroxamate siderophore desferrioxamine B at seawater ionic strength

    Science.gov (United States)

    Christenson, Emily A.; Schijf, Johan

    2011-11-01

    Organic complexation of yttrium and the rare earth elements (YREEs), although generally believed to be important, is an understudied aspect of YREE solution speciation in the open ocean. We report the first series of stability constants for complexes of YREEs (except Ce and Pm) with the trihydroxamate siderophore desferrioxamine B (DFOB), representing a class of small organic ligands that have an extraordinary selectivity for Fe(III) and are found in surface seawater at low-picomolar concentrations. Constants were measured by potentiometric titration of DFOB (pH 3-10) in the presence of single YREEs, in simple media at seawater ionic strength (NaClO 4 or NaCl, I = 0.7 M). Under these circumstances, the terminal amine of DFOB does not deprotonate. The four acid dissociation constants of the siderophore were determined separately by potentiometric titration of DFOB alone. Values for the bidentate (log β1), tetradentate (log β2), and hexadentate (log β3) complexes of La-Lu range from 4.88 to 6.53, 7.70 to 11.27, and 10.09 to 15.19, respectively, while Y falls between Gd and Tb in each case. Linear free-energy relations of the three stability constants with the first YREE hydrolysis constant, log β1∗, yield regression coefficients of >0.97. On the other hand, plots of the constants vs. the radius of the inner hydration sphere display an increasing deviation from linearity for the lightest REEs (La > Pr > Nd). This may signify steric constraints in DFOB folding around bulkier cations, a larger mismatch in coordination number, or a substantial degree of covalence in the YREE-hydroxamate bond. Complexes of the YREEs with DFOB are many orders of magnitude more stable than those with carbonate, the dominant inorganic YREE ligand in seawater. Speciation modeling with MINEQL indicates that, for an average seawater composition, the hexadentate complex could constitute as much as 28% of dissolved Lu at free DFOB concentrations as low as 10 -13 M. Such conditions might

  10. Effects of kaolinite colloids on Cd²⁺ transport through saturated sand under varying ionic strength conditions: Column experiments and modeling approaches.

    Science.gov (United States)

    Wikiniyadhanee, Rakkreat; Chotpantarat, Srilert; Ong, Say Kee

    2015-11-01

    Column experiments were performed under various ionic strengths (0.0-0.9 mM) using 10 mg L(-1) of Cd(2+) without kaolinite colloids and 10 mg L(-1) Cd(2+) mixed with 100 mg L(-1) kaolinite colloids. The nonequilibrium two-site model (TSM) described the behavior of both Cd(2+) transport and Cd(2+) co-transported with kaolinite colloids better than the equilibrium model (CD(eq)) (R(2)=0.978-0.996). The results showed that an increase in ionic strength negatively impacted the retardation factors (R) of both Cd(2+) and Cd(2+) mixed with kaolinite colloids. The presence of kaolinite colloids increased the retardation factors of Cd(2+) from 7.23 to 7.89, 6.76 to 6.61 and 3.79 to 6.99 for ionic strengths of 0.225, 0.45 and 0.9 mM, respectively. On the other hand, the presence of kaolinite colloids decreased the retardation factor of Cd(2+) from 8.13 to 7.83 for ionic strength of 0.0 mM. The fraction of instantaneous sorption sites (f) parameters, kinetic constant for sorption sites (α) and Freundlich constant (K(f)) were estimated from HYDRUS-1D of TSM for Cd(2+) transport. The fraction of instantaneous sorption sites was found to increase for an increase in ionic strength. K(f) values of Cd(2+) transport without kaolinite colloids for 0.0, 0.225 and 0.45 mM were found to be higher than those of Cd(2+) transport with kaolinite colloids, except for ionic strength of 0.9 mM. Hence, the presence of kaolinite colloids probably retarded the mobility of Cd(2+) in porous media for higher ionic strengths. Furthermore, retardation factors and K(f) values of both Cd(2+) transport and Cd(2+) co-transport were shown to decrease when ionic strength increased. Interestingly, according to TSM, the fraction of instantaneous sorption sites tends to increase for an increase in ionic strength, which imply that the mechanism of Cd(2+) sorption onto quartz sand can be better described using equilibrium sorption rather than nonequilibrium sorption for an increase in ionic strength. Copyright

  11. Release of colloids from primary minimum contact under unfavorable conditions by perturbations in ionic strength and flow rate.

    Science.gov (United States)

    Pazmino, Eddy; Trauscht, Jacob; Johnson, William P

    2014-08-19

    Colloid release from surfaces in response to ionic strength and flow perturbations has been mechanistically simulated. However, these models do not address the mechanism by which colloid attachment occurs, at least in the presence of bulk colloid-collector repulsion (unfavorable conditions), which is a prevalent environmental condition. We test whether a mechanistic model that predicts colloid attachment under unfavorable conditions also predicts colloid release in response to reduced ionic strength (IS) and increased fluid velocity (conditions thought prevalent for mobilization of environmental colloids). The model trades in mean-field colloid-collector interaction for discrete representation of surface heterogeneity, which accounts for a combination of attractive and repulsive interactions simultaneously, and results in an attached colloid population (in primary minimum contact with the surface) having a distribution of strengths of attraction. The model moderates equilibrium separation distance by inclusion of steric interactions. By using the same model parameters to quantitatively predict attachment under unfavorable conditions, simulated release of colloids (for all three sizes) from primary minimum attachment in response to perturbations qualitatively matched experimental results, demonstrating that both attachment and detachment were mechanistically simulated.

  12. Effects of ionic strength and temperature on the aggregation and deposition of multi-walled carbon nanotubes.

    Science.gov (United States)

    Wang, Lixin; Yang, Xuezhi; Wang, Qi; Zeng, Yuxuan; Ding, Lei; Jiang, Wei

    2017-01-01

    The aggregation and deposition of carbon nanotubes (CNTs) determines their transport and fate in natural waters. Therefore, the aggregation kinetics of humic-acid treated multi-walled carbon nanotubes (HA-MWCNTs) was investigated by time-resolved dynamic light scattering in NaCl and CaCl2 electrolyte solutions. Increased ionic strength induced HA-MWCNT aggregation due to the less negative zeta potential and the reduced electrostatic repulsion. The critical coagulation concentration (CCC) values of HA-MWCNTs were 80mmol/L in NaCl and 1.3mmol/L in CaCl2 electrolyte, showing that Ca(2+) causes more serious aggregation than Na(+). The aggregation behavior of HA-MWCNTs was consistent with Derjaguin-Landau-Verwey-Overbeek theory. The deposition kinetics of HA-MWCNTs was measured by the optical absorbance at 800nm. The critical deposition concentrations for HA-MWCNT in NaCl and CaCl2 solutions were close to the CCC values, therefore the rate of deposition cannot be increased by changing the ionic strength in the diffusion-limited aggregation regime. The deposition process was correlated to the aggregation since larger aggregates increased gravitational deposition and decreased random Brownian diffusion. HA-MWCNTs hydrodynamic diameters were evaluated at 5, 15 and 25°C. Higher temperature caused faster aggregation due to the reduced electrostatic repulsion and increased random Brownian motion and collision frequency. HA-MWCNTs aggregate faster at higher temperature in either NaCl or CaCl2 electrolyte due to the decreased electrostatic repulsion and increased random Brownian motion. Our results suggest that CNT aggregation and deposition are two correlated processes governed by the electrolyte, and CNT transport is favored at low ionic strength and low temperature. Copyright © 2016. Published by Elsevier B.V.

  13. How ionic strength affects the conformational behavior of human and rat beta amyloids--a computational study.

    Directory of Open Access Journals (Sweden)

    Zdeněk Kříž

    Full Text Available Progressive cerebral deposition of amyloid beta occurs in Alzheimers disease and during the aging of certain mammals (human, monkey, dog, bear, cow, cat but not others (rat, mouse. It is possibly due to different amino acid sequences at positions 5, 10 and 13. To address this issue, we performed series of 100 ns long trajectories (each trajectory was run twice with different initial velocity distribution on amyloid beta (1-42 with the human and rat amino acid sequence in three different environments: water with only counter ions, water with NaCl at a concentration of 0.15 M as a model of intracellular Na(+ concentration at steady state, and water with NaCl at a concentration of 0.30 M as a model of intracellular Na(+ concentration under stimulated conditions. We analyzed secondary structure stability, internal hydrogen bonds, and residual fluctuation. It was observed that the change in ionic strength affects the stability of internal hydrogen bonds. Increasing the ionic strength increases atomic fluctuation in the hydrophobic core of the human amyloid, and decreases the atomic fluctuation in the case of rat amyloid. The secondary structure analyses show a stable α-helix part between residues 10 and 20. However, C-terminus of investigated amyloids is much more flexible showing no stable secondary structure elements. Increasing ionic strength of the solvent leads to decreasing stability of the secondary structural elements. The difference in conformational behavior of the three amino acids at position 5, 10 and 13 for human and rat amyloids significantly changes the conformational behavior of the whole peptide.

  14. Nickel adsorption and desorption in an acric oxisol as a function of pH, ionic strength and incubation time

    Directory of Open Access Journals (Sweden)

    Estêvão Vicari Mellis

    Full Text Available ABSTRACT Although nickel (Ni has both important potential benefits and toxic effects in the environment, its behavior in tropical soils has not been well studied. Nickel adsorption-desorption in topsoil and subsoil samples of an acric Oxisol was studied at three pH values (from 3.0 to 8.0. Adsorption-desorption isotherms were elaborated from experiments with increasing Ni concentration (5 to 100 mg L-1, during 0, 4, and 12 weeks, using CaCl2 0.01 and 0.1 M as electrolytic support in order to also verify the effect of Ni-soil time contact and of ionic strength on the reaction. Experimental results of Ni adsorption fitted Langmuir model, which indicated that maximum Ni adsorption (71,440 mg kg-1 occurred at subsoil, after 12 weeks. Nickel affinity (KL was also greater at subsoil (1.0 L kg-1. The Ni adsorption in the topsoil samples was higher, due to its lower point of zero salt effect (PZSE and higher organic matter content. The increase in soil pH resulted in the increase of Ni adsorption. Nickel desorbed less from soil samples incubated for 4 or 12 weeks, suggesting that Ni interactions with colloidal particles increase over time. The amount of Ni desorbed increased with increasing ionic strength in both the topsoil and subsoil soil samples. Finally, adsorption-desorption hysteresis was clearly observed. Soil pH, ionic strength of soil solution and the Ni-soil contact time should be considered as criteria for selecting the areas for disposal of residues containing Ni or to compose remediation strategies for acric soils contaminated with Ni.

  15. Structural instability of shell-like assemblies of a keplerate-type polyoxometalate induced by ionic strength.

    Science.gov (United States)

    Veen, Sandra J; Kegel, Willem K

    2009-11-19

    We demonstrate a new structural instability of shell-like assemblies of polyoxometalates. Besides the colloidal instability, that is, the formation of aggregates that consist of many single layered POM-shells, these systems also display an instability on a structural scale within the shell-like assemblies. This instability occurs at significantly lower ionic strength than the colloidal stability limit and only becomes evident after a relatively long time. For the polyoxometalate, abbreviated as {Mo(72)Fe(30)}, it is shown that the structural stability limit of POM-shells lies between a NaCl concentration of 1.00 and 5.00 mM in aqueous solution.

  16. Influence of porewater velocity and ionic strength on DOC concentrations in and losses from peat-sand mixtures

    Science.gov (United States)

    Pfaffner, Nora; Tiemeyer, Bärbel; Fiedler, Sabine

    2015-04-01

    Organic soils play an important role in the global carbon cycle as they can act as a source or a sink for greenhouse gas emissions. The new IPCC Wetlands Supplement accounts for the first time for CO2 emissions from the decomposition of dissolved organic carbon (DOC). While there is a wealth of studies on "true" peat soils, knowledge on DOC losses from organic soils heavily disturbed by e.g. mixing with sand is fragmentary. Moreover, there are only a few studies on the influence of soil hydrological properties on DOC transport. This study investigates physico-chemical controls on the concentration and losses of DOC from a peat-sand mixture in a saturated column experiment with undisturbed columns. The soil originates from the study site "Grosses Moor" (Northern Germany) which is a former bog where peat layers remaining after peat mining were mixed with the underlying mineral soil. We studied the influence of the flow regime and the ionic strength of the irrigation solution on DOC concentrations and losses. Three different pumping rates and two different ionic strengths determined by different concentrations of a sodium chloride-calcium chloride mixture in the irrigation solution were applied. Transport properties of the soil were obtained by analyzing breakthrough curves (BTCs) of a conservative tracer (potassium bromide). For interpretation of the BTCs, the transport model STANMOD which is based on the two-region (mobile/immobile) non-equilibrium concept was fitted to the data. The shape of the BTCs and the STANMOD results showed that three of the four columns had a dual porosity structure, which affects the porewater velocity and the contact area. After a large initial peak, DOC concentrations equilibrated to nearly constant values. Increased porewater velocities decreased the concentration of DOC, but increased the losses. A new equilibrium concentration was reached after nearly all changes of the porewater velocity. At maximum pumping rates as determined from

  17. Role of eDNA on the Adhesion Forces between Streptococcus mutans and Substratum Surfaces : Influence of Ionic Strength and Substratum Hydrophobicity

    NARCIS (Netherlands)

    Das, Theerthankar; Sharma, Prashant K.; Krom, Bastiaan P.; van der Mei, Henny C.; Busscher, Henk J.

    2011-01-01

    The aim of this study was to investigate the role of extracellular DNA (eDNA) on the adhesion strength of Streptococcus mutans LT11 on substrata with different hydrophobicities at high and low ionic strengths. AFM adhesion forces to a hydrophilic and hydrophobic substratum increased with increasing

  18. Transport of vanadium (V in saturated porous media: effects of pH, ionic-strength and clay mineral

    Directory of Open Access Journals (Sweden)

    Yulu Wang

    2016-10-01

    Full Text Available Vanadium, a hazardous pollutant, has been frequently detected in soil and groundwater, however, its transport behavior in porous media were not clearly understood. In this study, the effects of solution pH, ionic strength (IS and the effect of clay mineral on the transport of vanadium in saturated porous media were investigated. Laboratory experiments using a series of columns packed with quartz sand were carried out to explore the retention and transport of vanadium with a range of ionic-strength (0.001–0.1 M and pH (4–8 and two different types of clay minerals montmorillonite and kaolinite. Results of the breakthrough experiments showed that vanadium was highly mobile in the saturated porous media. The increase in pH rendered a higher transport of vanadium in saturated porous media. The study also indicated an easier transfer of vanadium with an increase in IS. Montmorillonite enhanced the mobility of vanadium in the column when compared to kaolinite. A mathematical model based on advection-dispersion equation coupled with equilibrium and kinetic reactions was used to describe the retention and transport of vanadium in the columns very well.

  19. Charge and softness of the outer part of the cell wall of Thiobacillus ferrooxidans in the low ionic strength medium

    Directory of Open Access Journals (Sweden)

    Škvarla Jiří

    2002-03-01

    Full Text Available The surface charge and surface potential are parameters influencing the microbial adhesion phenomenon through the electrostatic interaction between bacteria and substrates. The Smoluchowski equation, originally developed for estimating the above parameters from the experimentally accessible electrophoretic mobility of rigid colloid particles, is however inapplicable to the elastic bacterial cells. The problem is that the outer cell wall of bacteria is a layer with a complex polyelectrolyte structure. In this article, the OhshimaLs model of the gsofth particle is applied to describe the surface electrostatics of Thiobacillus ferrooxidans cells by measuring their electrophoretic mobility in distilled water as a function of a (low ionic strength and pH. In this model, the rigid core is considered to be covered with a charged ion-penetrable layer of polyelectrolytes. Two model parameters have been determined by the curve fitting at pH from 3.2 to 5.8, namely the number density of the dissociated groups N and the softness parameter 1/ƒÉ of the polyelectrolyte layer of the bacterium. A disagreement of the best fit parameters (evaluated by the correlation coefficient with the analogous parameters determined for other colloids (including bacterial cells in aqueous solutions of a high ionic strength is discussed.

  20. Hydrodynamic modeling of NOM transport in UF: effects of charge density and ionic strength on effective size and sieving.

    Science.gov (United States)

    Yuan, Yanxiao; Kilduff, James E

    2009-07-15

    The transport behavior of natural organic matter (NOM) across polyethersulfone (PES) UF membranes having a range of nominal molecularweight cutoffs (MWCOs) was investigated and described with a hydrodynamic transport model. Transport of whole NOM and NOM fractionated on an anion exchange resin (IRA 958) was measured to investigate the impact of NOM size and charge density. It was found that the dominant transport mechanism, characterized by the membrane Peclet number, depended on the membrane MWCO, and transitioned from diffusion to convection at a MWCO of about 10 kDa. Increasing ionic strength significantly decreased the effective solute radius and decreased the observed rejection of charged NOM fractions, whereas no significant change was seen for neutral fractions. Using an available theoretical model for partitioning of charged solutes, the effect of ionic strength on the electrical double layer thickness can account for the observed changes in effective solute radius. These results provide insight into the role of solute charge and electrostatic interactions in NOM transport behavior.

  1. Effects of ionic strength and fulvic acid on adsorption of Tb(III) and Eu(III) onto clay

    Science.gov (United States)

    Poetsch, Maria; Lippold, Holger

    2016-09-01

    High salinity and natural organic matter are both known to facilitate migration of toxic or radioactive metals in geochemical systems, but little is known on their combined effect. We investigated complexation of Tb(III) and Eu(III) (as analogues for trivalent actinides) with fulvic acid and their adsorption onto a natural clay in the presence of NaCl, MgCl2 and CaCl2 up to very high ionic strengths. 160Tb, 152Eu and 14C-labelled fulvic acid were employed as radiotracers, allowing investigations at very low concentrations according to probable conditions in far-field scenarios of nuclear waste repositories. A combined Kd approach (Linear Additive Model) was tested for suitability in predicting solid-liquid distribution of metals in the presence of organic matter based on the interactions in the constituent subsystems. In this analysis, it could be shown that high ionic strength does not further enhance the mobilizing potential of humic matter. A quantitative reproduction of the influence of fulvic acid failed for most systems under study. Assumptions and limitations of the model are discussed.

  2. Sorption of U(VI) on goethite: Effects of pH, ionic strength, phosphate, carbonate and fulvic acid

    Energy Technology Data Exchange (ETDEWEB)

    Guo Zhijun [Radiochemistry Lab, School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000 (China)], E-mail: guozhj@lzu.edu.cn; Li Yan; Wu Wangsuo [Radiochemistry Lab, School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000 (China)

    2009-06-15

    U(VI) sorption on goethite was investigated as functions of pH, solid-to-liquid ratio (m/V), ionic strength and U(VI) concentration by a batch experimental method. Effects of phosphate, carbonate and fulvic acid (FA) on U(VI) sorption were examined. It was found that the sorption of U(VI) increases from 0% to 100% over the pH range of 2.5-4.5 and keeps constant in the high pH range. The sorption of U(VI) on goethite is insensitive to ionic strength. Different surface complexes in the framework of double-layer model were examined for fitting the sorption of U(VI) on goethite. A model with two mononuclear inner-sphere surface complexes, {identical_to}SOUO{sub 2}{sup +} and {identical_to}SOUO{sub 2}OH, was found capable of reproducing the pH sorption edges, the sorption isotherms and the sorption data with variable m/V in this study. The proposed model can also interpret the pH sorption edge collected at P{sub CO{sub 2}}=10{sup -3.58}atm without considering any ternary surface complexes of carbonate. Moreover, it was found that the presence of phosphate at relatively high concentration (6x10{sup -4} mol/L) promotes U(VI) sorption. The presence of FA of 20 mg/L has little effect on the sorption of U(VI) on goethite.

  3. Low frequency dielectric relaxation processes and ionic conductivity of montmorillonite clay nanoparticles colloidal suspension in poly(vinyl pyrrolidone−ethylene glycol blends

    Directory of Open Access Journals (Sweden)

    2008-11-01

    Full Text Available The dielectric dispersion behaviour of montmorillonite (MMT clay nanoparticles colloidal suspension in poly(vinyl pyrrolidone-ethylene glycol (PVP-EG blends were investigated over the frequency range 20 Hz to 1 MHz at 30°C. The 0, 1, 2, 3, 5 and 10 wt% MMT clay concentration of the weight of total solute (MMT+PVP were prepared in PVP-EG blends using EG as solvent. The complex relative dielectric function, alternating current (ac electrical conductivity, electric modulus and impedance spectra of these materials show the relaxation processes corresponding to the micro-Brownian motion of PVP chain, ion conduction and electrode polarization phenomena. The real part of ac conductivity spectra of these materials obeys Jonscher power law σ′(ω =σdc + Aωn in upper frequency end of the measurement, whereas dispersion in lower frequency end confirms the presence of electrode polarization effect. It was observed that the increase of clay concentration in the PVP-EG blends significantly increases the ac conductivity values, and simultaneously reduces the ionic conductivity relaxation time and electric double layer relaxation time, which suggests that PVP segmental dynamics and ionic motion are strongly coupled. The intercalation of EG structures in clay galleries and exfoliation of clay sheets by adsorption of PVP-EG structures on clay surfaces are discussed by considering the hydrogen bonding interactions between the hydroxyl group (–OH of EG molecules, carbonyl group (C=O of PVP monomer units, and the hydroxylated aluminate surfaces of the MMT clay particles. Results suggest that the colloidal suspension of MMT clay nano particles in the PVP-EG blends provide a convenient way to obtain an electrolyte solution with tailored electrical conduction properties.

  4. The effects of ionic strength on the toxicity of aluminium to Atlantic salmon (Salmo salar under non-steady state chemical conditions

    Directory of Open Access Journals (Sweden)

    Antonio B.S. POLÉO

    2002-02-01

    Full Text Available We have tested the influence of water ionic strength on the toxicity of aluminium in fish by comparing the mortality of Atlantic salmon (Salmo salar parr exposed to Al-rich water with additions of Ca2+ or Na+. The fish were exposed in parallel to Al-rich water (Al 500 μg l-1, pH 5.8 under non-steady state conditions, with and without the addition of one of the two base cations. The amount of Na+ and Ca2+ added to the water was calculated in order to obtain an identical increase in water ionic strength. Fish mortality was dependent on water residence time and whether or not base cations were added to the Al-rich water. In all Al-exposures, the highest mortality was always observed in fish exposed to water with the shortest residence time. Mortality decreased systematically with increasing water residence time through the exposure set-up. The addition of a base cation, Ca2+ or Na+, to the Al-rich water reduced fish mortality significantly compared to the Al-only exposures. Furthermore, increasing ionic strength with Na+ reduced mortality to a larger extent than the corresponding increase in ionic strength by the addition of Ca2+. The variation in mortality between the various aluminium and base cation treatments is discussed in terms of aluminium chemistry, specific mitigating effects of Ca2+ and Na+, and the general importance of water ionic strength. This study clearly demonstrates that Ca2+ does not play an unique role as an ameliorating cation for Al-toxicity in fish under non-steady state chemical conditions. Thus, ionic strength seems to be important, probably for the interaction between aluminium and the gill surface, reducing the possibility for positively charged aluminium species to bind to negatively charged sites.

  5. Calibration of membrane inlet mass spectrometric measurements of dissolved gases: differences in the responses of polymer and nano-composite membranes to variations in ionic strength.

    Science.gov (United States)

    Miranda, L D; Byrne, R H; Short, R T; Bell, R J

    2013-11-15

    This work examines the transmission behavior of aqueous dissolved methane, nitrogen, argon and carbon dioxide through two types of membranes: a polysiloxane nano-composite (PNC) membrane and a conventional polydimethylsiloxane (PDMS) membrane. Transmission properties at 30 °C were examined by membrane introduction mass spectrometry (MIMS) at nearly constant gas partial pressures in NaCl solutions over a range of ionic strength (0-1 molal). Gas flow rates were examined as a function of dissolved gas concentrations using the Setschenow equation. Although MIMS measurements with PDMS and PNC membranes produced signal responses that were directly proportional to aqueous dissolved gas concentrations, the proportionalities varied with ionic strength and were distinctly different for the two types of membranes. With the exception of carbon dioxide, the PNC membrane had membrane salting coefficients quite similar to Setschenow coefficients reported for gases in aqueous solution. In contrast, the PDMS membrane had membrane salting coefficients that were generally smaller than the corresponding Setschenow gas coefficient for each gas. Differences between Setschenow coefficients and membrane salting coefficients lead to MIMS calibrations (gas-flow vs. gas-concentration proportionalities) that vary with ionic strength. Accordingly, gas-flow vs. gas-concentration relationships for MIMS measurements with PDMS membranes are significantly dependent on ionic strength. In contrast, for PNC membranes, flow vs. concentration relationships are independent (argon, methane, nitrogen) or weakly dependent (CO2) on ionic strength. Comparisons of gas Setschenow and membrane salting coefficients can be used to quantitatively describe the dependence of membrane gas-flow on gas-concentrations and ionic strength for both PDMS and PNC membranes. Published by Elsevier B.V.

  6. Facilitated transport of Cu with hydroxyapatite nanoparticles in saturated sand: effects of solution ionic strength and composition.

    Science.gov (United States)

    Wang, Dengjun; Paradelo, Marcos; Bradford, Scott A; Peijnenburg, Willie J G M; Chu, Lingyang; Zhou, Dongmei

    2011-11-15

    Column experiments were conducted to investigate the facilitated transport of Cu in association with hydroxyapatite nanoparticles (nHAP) in water-saturated quartz sand at different solution concentrations of NaCl (0-100 mM) or CaCl(2) (0.1-1.0 mM). The experimental breakthrough curves and retention profiles of nHAP were well described using a mathematical model that accounted for two kinetic retention sites. The retention coefficients for both sites increased with the ionic strength (IS) of a particular salt. However, the amount of nHAP retention was more sensitive to increases in the concentration of divalent Ca(2+) than monovalent Na(+). The effluent concentration of Cu that was associated with nHAP decreased significantly from 2.62 to 0.17 mg L(-1) when NaCl increased from 0 to 100 mM, and from 1.58 to 0.16 mg L(-1) when CaCl(2) increased from 0.1 to 1.0 mM. These trends were due to enhanced retention of nHAP with changes in IS and ionic composition (IC) due to compression of the double layer thickness and reduction of the magnitude of the zeta potentials. Results indicate that the IS and IC had a strong influence on the co-transport behavior of contaminants with nHAP nanoparticles. Copyright © 2011 Elsevier Ltd. All rights reserved.

  7. Computer-aided model analysis for ionic strength-dependent effective charge of protein in ion-exchange chromatography

    DEFF Research Database (Denmark)

    Lim, Young-il; Jørgensen, Sten Bay; Kim, In-Ho

    2005-01-01

    differential algebraic equation (PDAE) system, a fast and accurate numerical method (i.e., conservation element/solution element (CE/SE) method), is proposed. Sensitivity and elasticity of the model parameters (e.g., steric/shape factors, adsorption heat coefficient, effective protein charge, equilibrium...... constant, mass transfer coefficient, axial dispersion coefficient and bed voidage) are analyzed for a BSA-salt system in a low protein concentration range. Within a low concentration range of bovine serum albumin (BSA) where linear adsorption isotherms are shown, the adsorption heat coefficient, shape...... salt concentrations, it is proposed that the effective protein charge could depend upon the salt concentration (or ionic strength). The reason for this dependence may be a steric hindrance of protein binding sites combined with a salt shielding effect neutralizing the surface charges of the protein. (c...

  8. A model of mitochondrial creatine kinase binding to membranes: adsorption constants, essential amino acids and the effect of ionic strength

    DEFF Research Database (Denmark)

    Fedosov, Sergey; Belousova, Lubov; Plesner, Igor

    1993-01-01

    is is suggested as the main candidate to form the adsorption site of mitCK. Deprotonated octameric mitCK easily dissociated from the membrane (View the MathML source at ionic strength View the MathML source and 5°C); after protonation its affinity increased many times (View the MathML source). Determination...... on the enzyme adsorption. An analysis of our own data as well as of the data from the literature is consistent with the adsorption site of the octameric mitCK being composed of 4 amino acid residues with pK = 8.8 in the free enzyme. The pK value changes to 9.8 upon binding of the protein to the membrane. Lysine...

  9. Speciation of phytate ion in aqueous solution. Cadmium(II) interactions in aqueous NaCl at different ionic strengths

    Energy Technology Data Exchange (ETDEWEB)

    Stefano, Concetta de; Milea, Demetrio; Porcino, Nunziatina; Sammartano, Silvio [Universita di Messina, Dipartimento di Chimica Inorganica, Chimica Analitica e Chimica Fisica, Messina (Italy)

    2006-09-15

    Interactions between myo-inositol 1,2,3,4,5,6-hexakis(dihydrogen phosphate) (phytic acid) and cadmium(II) were studied by using potentiometry (at 25 C with the ISE-H{sup +} glass electrode) in different metal to ligand (Phy) ratios (1:1{<=}Cd{sup 2+}:Phy{<=}4:1) in NaCl{sub aq} at different ionic strengths (0.1{<=}I/mol L{sup -1}{<=}1). Nine Cd{sub i}H{sub j}Phy{sup (12-2i-j)-} species are formed with i=1 and 2 and 4{<=}j{<=}7; and trinuclear Cd{sub 3}H{sub 4}Phy{sup 2-}. Dependence of complex formation constants on ionic strength was modeled by using Specific ion Interaction Theory (SIT) equations. Phytate and cadmium speciation are also dependent on the metal to ligand ratio. Stability of Cd{sub i}H{sub j}Phy{sup (12-2i-j)-} species was modeled as a function of both the ligand protonation step (j) and the number of metal cations bound to phytate (i), and relationships found were used for the prediction of species other than those experimentally determined (mainly di- and tri-protonated complexes), allowing the possibility of modeling Phy and Cd(II) behavior in natural waters and biological fluids. A critical evaluation of phytate sequestering ability toward cadmium(II) has been made under several experimental conditions, and the determination of an empirical parameter has been proposed for an objective ''quantification'' of this ability. A thorough analysis of literature data on phytate-cadmium(II) complexes has been performed. (orig.)

  10. Assessing the influence of media composition and ionic strength on drug release from commercial immediate-release and enteric-coated aspirin tablets.

    Science.gov (United States)

    Karkossa, Frank; Klein, Sandra

    2017-10-01

    The objective of this test series was to elucidate the importance of selecting the right media composition for a biopredictive in-vitro dissolution screening of enteric-coated dosage forms. Drug release from immediate-release (IR) and enteric-coated (EC) aspirin formulations was assessed in phosphate-based and bicarbonate-based media with different pH, electrolyte composition and ionic strength. Drug release from aspirin IR tablets was unaffected by media composition. In contrast, drug release from EC aspirin formulations was affected by buffer species and ionic strength. In all media, drug release increased with increasing ionic strength, but in bicarbonate-based buffers was delayed when compared with that in phosphate-based buffers. Interestingly, the cation species in the dissolution medium had also a clear impact on drug release. Drug release profiles obtained in Blank CarbSIF, a new medium simulating pH and average ionic composition of small intestinal fluid, were different from those obtained in all other buffer compositions studied. Results from this study in which the impact of various media parameters on drug release of EC aspirin formulations was systematically screened clearly show that when developing predictive dissolution tests, it is important to simulate the ionic composition of intraluminal fluids as closely as possible. © 2017 Royal Pharmaceutical Society.

  11. Adsorption of a Textile Dye on Commercial Activated Carbon: A Simple Experiment to Explore the Role of Surface Chemistry and Ionic Strength

    Science.gov (United States)

    Martins, Angela; Nunes, Nelson

    2015-01-01

    In this study, an adsorption experiment is proposed using commercial activated carbon as adsorbent and a textile azo dye, Mordant Blue-9, as adsorbate. The surface chemistry of the activated carbon is changed through a simple oxidation treatment and the ionic strength of the dye solution is also modified, simulating distinct conditions of water…

  12. Effects of hydrodynamic mixing intensity coupled with ionic strength on the initial stage dynamics of bridging flocculation of polystyrene latex particles with polyelectrolyte

    NARCIS (Netherlands)

    Adachi, Y.; Matsumoto, T.; Cohen Stuart, M.A.

    2002-01-01

    Effects of hydrodynamic mixing intensity on the initial stage dynamics of bridging flocculation induced by adsorbing polyelectrolyte were analyzed as an extension of previous report on the effect of ionic strength (J. Coll. Int. Sci. 204 (1998) 328). Mixing condition were changed by adopting forked

  13. A Simplified Undergraduate Laboratory Experiment to Evaluate the Effect of the Ionic Strength on the Equilibrium Concentration Quotient of the Bromcresol Green Dye

    Science.gov (United States)

    Rodriguez, Hernan B.; Mirenda, Martin

    2012-01-01

    A modified laboratory experiment for undergraduate students is presented to evaluate the effects of the ionic strength, "I", on the equilibrium concentration quotient, K[subscript c], of the acid-base indicator bromcresol green (BCG). The two-step deprotonation of the acidic form of the dye (sultone form), as it is dissolved in water, yields…

  14. The influence of a fulvic acid on the adsorption of europium and strontium by alumina and quartz: effects of pH and ionic strength

    Energy Technology Data Exchange (ETDEWEB)

    Norden, M. (Dept. of Water and Environmental Studies, Linkoeping Univ. (Sweden)); Ephraim, J.H. (Dept. of Water and Environmental Studies, Linkoeping Univ. (Sweden)); Allard, B. (Dept. of Water and Environmental Studies, Linkoeping Univ. (Sweden))

    1994-01-01

    A batch method has been employed to study the adsorption of trace quantities of Eu and Sr on [alpha]-Al[sub 2]O[sub 3] and SiO[sub 2] as a function of pH (3-9), ionic strength (0.10 and 0.01 M NaClO[sub 4]) and the presence of a well-characterized aquatic fulvic acid (FA). A comparison of Eu and Sr adsorption by alumina showed that FA could both reduce and enhance metal ion adsorption. In the absence of FA the adsorption of the metal ions onto alumina was a function of both pH and ionic strength. In the presence of FA the ionic strength effect on the Eu adsorption vanished, while the Sr adsorption showed a clear dependence on ionic strength. The adsorption of Eu and Sr on quartz was lower than the adsorption of the metals on alumina. Additionally, the adsorption of Eu and Sr on quartz was apparently lower than the adsorption on alumina in the presence of Fa. For both metal ions the adsorption on quartz was higher at 0.10 M than at 0.01 M NaClO[sub 4] - an observation that was reversed in the case of alumina. Increasing concentrations of FA lowered the pH at which Eu adsorption on alumina would be reduced. (orig.)

  15. SORPTION OF CU AND ZN TO KAOLINITE AND IRON OXIDE: EFFECTS OF HUMIC ACID AND IONIC STRENGTH AND IMPLICATIONS FOR STORMWATER RUNOFF

    Science.gov (United States)

    Heavy metals are common pollutants in wet weather flows and urban waterways. Changes in ionic strength, whether from mixing with saline waters, road salt, or from the large osmotic adjustment needed for the Microtox toxicity assay, affect the aqueous chemistry of stormwater runof...

  16. Effect of ionic strength on the interfacial viscoelasticity and stability of silk fibroin at the oil/water interface.

    Science.gov (United States)

    Tang, Xiaoxiao; Qiao, Xiuying; Miller, Reinhard; Sun, Kang

    2016-12-01

    The amphiphilic character and surface activity endows silk fibroin with the ability to reside at fluid interfaces and effectively stabilize emulsions. However, the influence of relevant factors and their actual effect on the interfacial viscoelasticity and stability of silk fibroin at the oil/water interface has received less attention. In the present study, the effect of ionic strength on the interfacial viscoelasticity, emulsification effectiveness and stability of silk fibroin at the oil/water interface was investigated in detail. A higher ion concentration facilitates greater adsorption, stronger molecular interaction and faster structure reorganization of silk fibroin at the oil/water interface, thus causing quicker interfacial saturation adsorption, greater interfacial strength and lower interfacial structural fracture on large deformation. However, the presence of concentrated ions screens the charges in silk fibroin molecules and the zeta potential decreases as a result of electrostatic screening and ion-binding effects, which may result in emulsion droplet coalescence and a decrease in emulsion stability. The positively-charged ions significantly affect the interfacial elasticity and stability of silk fibroin layers at the oil/water interface as a result of the strong electrostatic interactions between counter-ions and the negatively-charged groups of silk fibroin. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

  17. The Hinge Segment of Human NADPH-Cytochrome P450 Reductase in Conformational Switching: The Critical Role of Ionic Strength

    Directory of Open Access Journals (Sweden)

    Diana Campelo

    2017-10-01

    Full Text Available NADPH-cytochrome P450 reductase (CPR is a redox partner of microsomal cytochromes P450 and is a prototype of the diflavin reductase family. CPR contains 3 distinct functional domains: a FMN-binding domain (acceptor reduction, a linker (hinge, and a connecting/FAD domain (NADPH oxidation. It has been demonstrated that the mechanism of CPR exhibits an important step in which it switches from a compact, closed conformation (locked state to an ensemble of open conformations (unlocked state, the latter enabling electron transfer to redox partners. The conformational equilibrium between the locked and unlocked states has been shown to be highly dependent on ionic strength, reinforcing the hypothesis of the presence of critical salt interactions at the interface between the FMN and connecting FAD domains. Here we show that specific residues of the hinge segment are important in the control of the conformational equilibrium of CPR. We constructed six single mutants and two double mutants of the human CPR, targeting residues G240, S243, I245 and R246 of the hinge segment, with the aim of modifying the flexibility or the potential ionic interactions of the hinge segment. We measured the reduction of cytochrome c at various salt concentrations of these 8 mutants, either in the soluble or membrane-bound form of human CPR. All mutants were found capable of reducing cytochrome c yet with different efficiency and their maximal rates of cytochrome c reduction were shifted to lower salt concentration. In particular, residue R246 seems to play a key role in a salt bridge network present at the interface of the hinge and the connecting domain. Interestingly, the effects of mutations, although similar, demonstrated specific differences when present in the soluble or membrane-bound context. Our results demonstrate that the electrostatic and flexibility properties of the hinge segment are critical for electron transfer from CPR to its redox partners.

  18. Adsorption of divalent lead ions by zeolites and activated carbon: effects of pH, temperature, and ionic strength.

    Science.gov (United States)

    Payne, Kelly B; Abdel-Fattah, Tarek M

    2004-01-01

    Lead alloy bullets used at the 2600 military small arm ranges and 9000 nonmilitary outdoor shooting ranges in the United States are a source of mobilized lead ions under conditions of low pH, significant changes in ionic strength, changes in the reduction oxidation potential (redox), and through binding metal ions to soil organic matter. Once mobile, these lead ions can contaminate adjacent soil and water. Batch adsorption kinetic and isotherm studies were conducted to compare and evaluate different types of adsorbents for lead ion removal from aqueous media. The effects on lead ion absorption from pH changes, competing ions, and temperature increases were also investigated. Adsorbent materials such as activated carbon and naturally occurring zeolites (clinoptilolite and chabazite) were selected because of their relative low cost and because the zeolites are potential point-of-use materials for mitigating wastewater runoff. Molecular sieves, Faujasite (13X) and Linde type A (5A) were selected because they provide a basis for comparison with previous studies and represent well-characterized materials. The relative rate for lead ion adsorption was: 13X > chabazite > clinoptilolite > 5A > activated carbon. Modeling lead ion adsorption by these adsorbents using the Langmuir and Freundlich isotherm expressions determined the adsorbents' capacity for lead ion removal from aqueous media. 13X, 5A, and activated carbon best fit the Langmuir isotherm expression; chabazite and clinoptilolite best fit the Freundlich isotherm. Applications of chabazite would require pH values between 4 and 11, clinoptilolite between 3 and 11, while activated carbon would operate at a pH above 7. Ionic competition reduced lead ion removal by the zeolites, but enhanced activated carbon performance. Increasing temperature improved adsorption performance for the zeolites; activated carbon lead ion adsorption was temperature independent.

  19. Analysis of responsive characteristics of ionic-strength-sensitive hydrogel with consideration of effect of equilibrium constant by a chemo-electro-mechanical model.

    Science.gov (United States)

    Li, Hua; Lai, Fukun; Luo, Rongmo

    2009-11-17

    A multiphysics model is presented in this paper for analysis of the influence of various equilibrium constants on the smart hydrogel responsive to the ionic strength of environmental solution, and termed the multieffect-coupling ionic-strength stimulus (MECis) model. The model is characterized by a set of partial differential governing equations by consideration of the mass and momentum conservations of the system and coupled chemical, electrical, and mechanical multienergy domains. The Nernst-Planck equations are derived by the mass conservation of the ionic species in both the interstitial fluid of the hydrogel and the surrounding solution. The binding reaction between the fixed charge groups of the hydrogel and the mobile ions in the solution is described by the fixed charge equation, which is based on the Langmuir monolayer theory. As an important effect for the binding reaction, the equilibrium constant is incorporated into the fixed charge equation. The kinetics of the hydrogel swelling/deswelling is illustrated by the mechanical equation, based on the law of momentum conservation for the solid polymeric networks matrix within the hydrogel. The MECis model is examined by comparison of the numerical simulations and experiments from open literature. The analysis of the influence of different equilibrium constants on the responsive characteristics of the ionic-strength-sensitive hydrogel is carried out with detailed discussion.

  20. Ion Exchange Distribution Coefficient Tests and Computer Modeling at High Ionic Strength Supporting Technetium Removal Resin Maturation

    Energy Technology Data Exchange (ETDEWEB)

    Nash, Charles A. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Hamm, L. Larry [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Smith, Frank G. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); McCabe, Daniel J. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2014-12-19

    The primary treatment of the tank waste at the DOE Hanford site will be done in the Waste Treatment and Immobilization Plant (WTP) that is currently under construction. The baseline plan for this facility is to treat the waste, splitting it into High Level Waste (HLW) and Low Activity Waste (LAW). Both waste streams are then separately vitrified as glass and poured into canisters for disposition. The LAW glass will be disposed onsite in the Integrated Disposal Facility (IDF). There are currently no plans to treat the waste to remove technetium, so its disposition path is the LAW glass. Due to the water solubility properties of pertechnetate and long half-life of 99Tc, effective management of 99Tc is important to the overall success of the Hanford River Protection Project mission. To achieve the full target WTP throughput, additional LAW immobilization capacity is needed, and options are being explored to immobilize the supplemental LAW portion of the tank waste. Removal of 99Tc, followed by off-site disposal, would eliminate a key risk contributor for the IDF Performance Assessment (PA) for supplemental waste forms, and has potential to reduce treatment and disposal costs. Washington River Protection Solutions (WRPS) is developing some conceptual flow sheets for supplemental LAW treatment and disposal that could benefit from technetium removal. One of these flowsheets will specifically examine removing 99Tc from the LAW feed stream to supplemental immobilization. To enable an informed decision regarding the viability of technetium removal, further maturation of available technologies is being performed. This report contains results of experimental ion exchange distribution coefficient testing and computer modeling using the resin SuperLig® 639a to selectively remove perrhenate from high ionic strength simulated LAW. It is advantageous to operate at higher concentration in order to treat the waste

  1. Van der Waals-like instability in suspensions of mutually repelling charged colloids

    NARCIS (Netherlands)

    Roij, R. van; Hansen, J.-P.

    1997-01-01

    We show theoretically that the purely repulsive screened-Coulomb (or Derjaguin-Landau-Verwey- Overbeek) interaction between charged colloidal particles is compatible with gas-liquid, gas-solid, and solid-solid coexistence in colloidal suspensions of low ionic strength of about 1026

  2. Van der Waals-like instability in suspensions of mutually repelling charged colloids

    OpenAIRE

    van Roij, R.; Hansen, J. -P.

    1997-01-01

    We show theoretically that the purely repulsive screened-Coulomb (or Derjaguin-Landau-Verwey- Overbeek) interaction between charged colloidal particles is compatible with gas-liquid, gas-solid, and solid-solid coexistence in colloidal suspensions of low ionic strength of about 1026 molyliter. This finding may partially resolve the ongoing debate on attractions between like-charged particles.

  3. Accumulation of Mg to Diffusive Gradients in Thin Films (DGT) Devices: Kinetic and Thermodynamic Effects of the Ionic Strength.

    Science.gov (United States)

    Altier, Alexandra; Jiménez-Piedrahita, Martín; Rey-Castro, Carlos; Cecilia, Joan; Galceran, Josep; Puy, Jaume

    2016-10-05

    Availability of magnesium is a matter of concern due to its role in many environmental and biological processes. Diffusive Gradients in Thin Films (DGT) devices can measure Mg availability in situ. This work shows that Mg accumulation in water largely increases when ionic strength (I) decreases. This phenomenon can be explained from (i) the increase of both the association equilibrium (K) and rate (k a,R ) constants for the reaction between Mg cations and resin sites, and (ii) the growing contribution of the partitioning of Mg cations at the resin-gel interface, as I decreases. Two theoretical models that take into account electrical interactions among Mg cations, background electrolyte, and resin sites can successfully be used to determine k a,R and K at each I. Both models yield similar k a,R values, which fulfill an expression for the kinetic salt effect. For freshwater (with a typical salinity of 10 mM and circumneutral pH), the binding of Mg is so fast and strong that the simplest perfect-sink DGT expression can be helpful to predict (overestimation lower than 5%) the accumulation in solutions with Mg concentrations up to 1 mM whenever the deployment time is below 9 h. Perfect sink conditions can still be applied for longer times, in systems with either a lower I or a lower Mg concentration.

  4. Reversible and non-reversible thermal denaturation of lysozyme with varying pH at low ionic strength.

    Science.gov (United States)

    Blumlein, Alice; McManus, Jennifer J

    2013-10-01

    DSC analysis has been used to quantify the reversibility of unfolding following thermal denaturation of lysozyme. Since the temperature at which protein unfolding occurs, Tm, varies with different solution conditions, the effect on the melting temperature and the degree of refolding after thermal denaturation in low ionic strength sodium phosphate buffers (5-1000mM) over a range of pH (5-9) in the presence/absence of disaccharides is examined. This study compares the enthalpies of unfolding during successive heating cycles to quantify reversibility following thermal denaturation. The disaccharides, trehalose and maltose were used to assess if the disaccharide induced increase in Tm is reflected in the reversibility of thermally induced denaturation. There was extensive overlap between the Tm values where non-reversible and reversible thermal denaturation occurred. Indeed, for pH6, at the highest and lowest Tm, no refolding was observed whereas refolding was observed for intermediate values, but with similar Tm values having different proportions of refolded protein. We established a method to measure the degree of reversible unfolding following thermal denaturation and hence indirectly, the degree to which protein is lost to irreversible aggregation, and show that solution conditions which increase melt transition temperatures do not automatically confer an increase in reversibility. This type of analysis may prove useful in assessing the stability of proteins in both the biopharmaceutical and food industries. Copyright © 2013 Elsevier B.V. All rights reserved.

  5. Roles of ionic strength and biofilm roughness on adhesion kinetics of Escherichia coli onto groundwater biofilm grown on PVC surfaces

    Science.gov (United States)

    Janjaroen, Dao; Ling, Fangqiong; Monroy, Guillermo; Derlon, Nicolas; Mogenroth, Eberhard; Boppart, Stephen A.; Liu, Wen-Tso; Nguyen, Thanh H.

    2013-01-01

    Mechanisms of Escherichia coli attachment on biofilms grown on PVC coupons were investigated. Biofilms were grown in CDC reactors using groundwater as feed solution over a period up to 27 weeks. Biofilm physical structure was characterized at the micro- and meso-scales using Scanning Electron Microscopy (SEM) and Optical Coherence Tomography (OCT), respectively. Microbial community diversity was analyzed with Terminal Restricted Fragment Length Polymorphism (T-RFLP). Both physical structure and microbial community diversity of the biofilms were shown to be changing from 2 weeks to 14 weeks, and became relatively stable after 16 weeks. A parallel plate flow chamber coupled with an inverted fluorescent microscope was also used to monitor the attachment of fluorescent microspheres and E. coli on clean PVC surfaces and biofilms grown on PVC surfaces for different ages. Two mechanisms of E. coli attachment were identified. The adhesion rate coefficients (kd) of E. coli on nascent PVC surfaces and 2-week biofilms increased with ionic strength. However, after biofilms grew for 8 weeks, the adhesion was found to be independent of solution chemistry. Instead, a positive correlation between kd and biofilm roughness as determined by OCT was obtained, indicating that the physical structure of biofilms could play an important role in facilitating the adhesion of E. coli cells. PMID:23497979

  6. Sorption of chlorimuron-ethyl on montmorillonite clays: effects of exchangeable cations, pH, and ionic strength.

    Science.gov (United States)

    Ren, Wenjie; Teng, Ying; Zhou, Qixing; Paschke, Albrecht; Schüürmann, Gerrit

    2014-10-01

    Sorption interaction of chlorimuron-ethyl with montmorillonite clays was investigated under varied types of exchangeable cation, pH, and ionic strength conditions. Chlorimuron-ethyl sorption on bentonites exhibited pronounced cation dependency, and the sorption ability increased as the sequence Ca(2+)- clay type and much weaker for montmorillonites. The decrease of pH at the range of 4.0-6.0 prominently increased sorption of chlorimuron-ethyl on all cation-exchanged montmorillonite clays, and nearly a neglected sorption (about 2 %) can be observed at pH over 7.0. In the presence of CaCl2, sorption of chlorimuron-ethyl on Fe(3+)-bentonite was promoted because of complexion of Ca(2+) and the surface of Fe(3+)-bentonite. However, as the concentration of CaCl2 increased, chlorimuron-ethyl sorption on Ca(2+)- and Fe(3+)-exchanged bentonite decreased, suggesting that Ca bridging was not the prevailing mechanism for sorption of chlorimuron-ethyl on these clays. Furthermore, chlorimuron-ethyl sorption was relatively sensitive to pH, and the change of pH may obscure effect of other factors on the sorption, so it was quite necessary to control pH at a constant value when the effect of other factor was being studied.

  7. Effect of pH, ionic strength and humic acid on the sorption of uranium(VI) to attapulgite

    Energy Technology Data Exchange (ETDEWEB)

    Niu Zhiwei [Radiochemistry Laboratory, Lanzhou University, Lanzhou 730000, Gansu (China); Fan Qiaohui [Radiochemistry Laboratory, Lanzhou University, Lanzhou 730000, Gansu (China)], E-mail: fanqiaohui@gmail.com; Wang Wenhua; Xu Junzheng [Radiochemistry Laboratory, Lanzhou University, Lanzhou 730000, Gansu (China); Chen Lei [School of Chemical Engineering, Shandong University of Technology, 255049 Zibo, Shandong (China); Wu Wangsuo [Radiochemistry Laboratory, Lanzhou University, Lanzhou 730000, Gansu (China)], E-mail: wuws@lzu.edu.cn

    2009-09-15

    Attapulgite was investigated to remove UO{sub 2}{sup 2+} from aqueous solutions because of its strong sorption capacity. Herein, the attapulgite sample was characterized by Fourier transform infrared spectra (FTIR), X-ray diffraction (XRD) and acid-base titration in detail. Sorption of UO{sub 2}{sup 2+} on attapulgite was strongly dependent on pH values and ionic strength. The presence of humic acid enhanced the sorption of UO{sub 2}{sup 2+} on attapulgite obviously because of the strong complexation of humic acid (HA) with UO{sub 2}{sup 2+} on attapulgite surface. Sorption of UO{sub 2}{sup 2+} on attapulgite was mainly dominated by ion-exchange or outer-sphere complexation at low pH values, and by inner-sphere complexation at high pH values. The results indicated that attapulgite was a suitable material for the preconcentration and solidification of UO{sub 2}{sup 2+} from large volume of solutions because of its negative surface charge and large surface areas.

  8. ORGANIC-HIGH IONIC STRENGTH AQUEOUS SOLVENT SYSTEMS FOR SPIRAL COUNTER-CURRENT CHROMATOGRAPHY: GRAPHIC OPTIMIZATION OF PARTITION COEFFICIENT

    Science.gov (United States)

    Zeng, Yun; Liu, Gang; Ma, Ying; Chen, Xiaoyuan; Ito, Yoichiro

    2012-01-01

    A new series of organic-high ionic strength aqueous two-phase solvents systems was designed for separation of highly polar compounds by spiral high-speed counter-current chromatography. A total of 21 solvent systems composed of 1-butanol-ethanol-saturated ammonium sulfate-water at various volume ratios are arranged according to an increasing order of polarity. Selection of the two-phase solvent system for a single compound or a multiple sample mixture can be achieved by two steps of partition coefficient measurements using a graphic method. The capability of the method is demonstrated by optimization of partition coefficient for seven highly polar samples including tartrazine (K=0.77), tryptophan (K=1.00), methyl green (K= 0.93), tyrosine (0.81), metanephrine (K=0.89), tyramine (K=0.98), and normetanephrine (K=0.96). Three sulfonic acid components in D&C Green No. 8 were successfully separated by HSCCC using the graphic selection of the two-phase solvent system. PMID:23467197

  9. Stability properties of surfactant-free thin films at different ionic strengths: measurements and modeling.

    Science.gov (United States)

    Lech, Frederik J; Wierenga, Peter A; Gruppen, Harry; Meinders, Marcel B J

    2015-03-10

    Foam lamellae are the smallest structural elements in foam. Such lamellae can experimentally be studied by analysis of thin liquid films in glass cells. These thin liquid films usually have to be stabilized against rupture by surface active substances, such as proteins or low molecular weight surfactants. However, horizontal thin liquid films of pure water with a radius of 100 μm also show remarkable stability when created in closed Sheludko cells. To understand thin film stability of surfactant-free films, the drainage behavior and rupture times of films of water and NaCl solutions were determined. The drainage was modeled with an extended Derjaguin-Landau-Verwey-Overbeek (DLVO) model, which combines DLVO and hydrophobic contributions. Good correspondence between experiment and theory is observed, when hydrophobic interactions are included, with fitted values for surface potential (ψ(0,water)) of -60 ± 5 mV, hydrophobic strength (B(hb,water)) of 0.22 ± 0.02 mJ/m(2), and a range of the hydrophobic interaction (λ(hb, water)) of 15 ± 1 nm in thin liquid films. In addition, Vrij's rupture criterion was successfully applied to model the stability regions and rupture times of the films. The films of pure water are stable over long time scales (hours) and drain to a final thickness >40 nm if the concentration of electrolytes is low (resistivity 18.2 MQ). With increasing amounts of ions (NaCl) the thin films drain to <40 nm thickness and the rupture stability of the films is reduced from hours to seconds.

  10. Effect of surface chemistry, solution pH, and ionic strength on the removal of herbicides diuron and amitrole from water by an activated carbon fiber.

    Science.gov (United States)

    Fontecha-Cámara, M A; López-Ramón, M V; Alvarez-Merino, M A; Moreno-Castilla, C

    2007-01-30

    A study was conducted on the effects of carbon surface chemistry, solution pH, and ionic strength on the removal of diuron and amitrole from aqueous solutions by adsorption on an as-received and oxidized activated carbon fiber. Results obtained were explained by the surface characteristics of the adsorbents and the characteristics of the herbicide molecules. Under the experimental conditions used, diuron uptake was much higher than that of amitrole, despite its larger molecular dimensions, due to the lesser water solubility, greater hydrophobicity, and larger dipolar moment of diuron compared with amitrole. Uptake variations associated with differences in carbon surface oxidation, solution pH, and ionic strength were explained by corresponding changes in electrostatic, hydrophobic, and van der Waals interactions.

  11. Adsorption of humic acid and Eu(III) to multi-walled carbon nanotubes. Effect of pH, ionic strength and counterion effect

    Energy Technology Data Exchange (ETDEWEB)

    Fan, Q.H. [Chinese Academy of Sciences, Hefei (China). Key Lab. of Novel Thin Film Solar Cell; Lanzhou Univ. (China). Radiochemistry Lab.; Shao, D.D.; Hu, J.; Chen, C.L.; Wang, X.K. [Chinese Academy of Sciences, Hefei (China). Key Lab. of Novel Thin Film Solar Cell; Wu, W.S. [Lanzhou Univ. (China). Radiochemistry Lab.

    2009-07-01

    Carbon nanotubes (CNTs) have come under intense multidisciplinary study because of their unique physicochemical properties. Understanding adsorptive interactions of simultaneous humic substances (HS) and radionuclides on CNTs is critical to understand the pollution of radionuclides and the assessment of potential impact of CNTs on the behavior of HS and radionuclides. In this paper, the adsorption of humic acid (HA) and Eu(III) on multi-walled carbon nanotubes (MWCNTs) are studied as a function of pH and ionic strength. The results indicate that the adsorption of Eu(III) and HA on MWCNTs is strongly dependent on pH and ionic strength, and the presence of HA enhances Eu(III) adsorption to HA-MWCNT hybrids. The XPS analysis indicates that the functional groups of HA contribute to Eu(III) adsorption to MWCNTs. (orig.)

  12. Friction-corrosion of AISI 316L/bone cement and AISI 316L/PMMA contacts: ionic strength effect on tribological behaviour

    OpenAIRE

    Geringer, Jean; Atmani, Fouad; Forest, Bernard

    2009-01-01

    International audience; Wear phenomena understanding of implants is a challenge: friction-corrosion of biomaterials, which constitute orthopaedic implants, is a significant issue concerning the aseptic loosening. This work aims at studying AISI 316L/bone cement friction which is a tribological problem related to hip joint cemented prostheses. This study focuses on the ionic strength effect on the tribological behaviour of 316L/bone cement and 316L/PMMA contacts. PMMA, poly(methylmethacrylate)...

  13. Dynamic and equilibrium adsorption behaviour of ß-lactoglobulin at the solution/tetradecane interface: Effect of solution concentration, pH and ionic strength

    OpenAIRE

    Won, Jooyoung

    2016-01-01

    Proteins are amphiphilic and adsorb at liquid interfaces. Therefore, they can be efficient stabilizers of foams and emulsions. β-lactoglobulin (BLG) is one of the most widely studied proteins due to its major industrial applications, in particular in food technology. In the present work, the influence of different bulk concentration, solution pH and ionic strength on the dynamic and equilibrium pressures of BLG adsorbed layers at the solution/tetradecane (W/TD) interface has been investig...

  14. The effect of pH, buffer capacity and ionic strength on quetiapine fumarate release from matrix tablets prepared using two different polymeric blends.

    Science.gov (United States)

    Hamed, Rania; AlJanabi, Reem; Sunoqrot, Suhair; Abbas, Aiman

    2017-08-01

    The objective of this study was to investigate the effect of the different physiological parameters of the gastrointestinal (GI) fluid (pH, buffer capacity, and ionic strength) on the in vitro release of the weakly basic BCS class II drug quetiapine fumarate (QF) from two once-a-day matrix tablet formulations (F1 and F2) developed as potential generic equivalents to Seroquel ® XR. F1 tablets were prepared using blends of high and low viscosity grades of hydroxypropyl methylcellulose (HPMC K4M and K100LV, respectively), while F2 tablets were prepared from HPMC K4M and PEGylated glyceryl behenate (Compritol ® HD5 ATO). The two formulations attained release profiles of QF over 24 h similar to that of Seroquel ® XR using the dissolution medium published by the Food and Drug Administration (FDA). A series of solubility and in vitro dissolution studies was then carried out using media that simulate the gastric and intestinal fluids and cover the physiological pH, buffer capacity and ionic strength range of the GIT. Solubility studies revealed that QF exhibits a typical weak base pH-dependent solubility profile and that the solubility of QF increases with increasing the buffer capacity and ionic strength of the media. The release profiles of QF from F1, F2 and Seroquel ® XR tablets were found to be influenced by the pH, buffer capacity and ionic strength of the dissolution media to varying degrees. Results highlight the importance of studying the physiological variables along the GIT in designing controlled release formulations for more predictive in vitro-in vivo correlations.

  15. The Influence of High Drug Loading in Xanthan Tablets and Media with Different Physiological pH and Ionic Strength on Swelling and Release.

    Science.gov (United States)

    Mikac, Urša; Sepe, Ana; Baumgartner, Saša; Kristl, Julijana

    2016-03-07

    The formation of a gel coat around xanthan (Xan) tablets, empty or loaded with pentoxifylline (PF), and its release in media differing in pH and ionic strength by NMR, MR imaging, and two release methods were studied. The T1 and T2 NMR relaxation times in gels depend predominantly on Xan concentration; the presence of PF has negligible influence on them. It is interesting that the matrix swelling is primarily regulated by Xan despite high drug loading (25%, 50%). The gastric pH and high ionic strength of the media do not influence the position of the penetration and swelling fronts but do affect the erosion front and gel thickness. The different release profiles obtained in mixing and nonmixing in vitro methods are the consequence of matrix hydration level and erosion at the surface. In water and in diluted acid medium with low ionic strength, the main release mechanism is erosion, whereas in other media (pH 1.2, μ ≥ 0.20 M), anomalous transport dominates as was found out by fitting of measured data with theoretical model. Besides the in vitro investigation that mimics gastric conditions, mathematical modeling makes the product development more successful.

  16. Effects of background electrolytes and ionic strength on enrichment of Cd(II) ions with magnetic graphene oxide-supported sulfanilic acid.

    Science.gov (United States)

    Hu, Xin-jiang; Liu, Yun-guo; Zeng, Guang-ming; You, Shao-hong; Wang, Hui; Hu, Xi; Guo, Yi-ming; Tan, Xiao-fei; Guo, Fang-ying

    2014-12-01

    To elucidate the influence mechanisms of background electrolytes and ionic strength on Cd(II) removal, the adsorption of Cd(II) onto magnetic graphene oxide-supported sulfanilic acid (MGO-SA) in aqueous solutions containing different types and concentrations of background electrolytes was studied. The results indicate that Cd(II) adsorption was strongly dependent on pH and could be strongly affected by background electrolytes and ionic strength. The Cd(II) removal was decreased with the presence of background electrolyte cations (Na(+), K(+), Ca(2+), Mg(2+), Mn(2+), Zn(2+), and Ni(2+)), and the divalent cations exerted more obvious influences on the Cd(II) uptake than the monovalent cations at pH 6. Both Cl(-) and NO3(-) had negative effects on Cd(II) adsorption because they can form water-soluble metal-anion complexes with Cd(II) ions. The presence of 0.01molL(-1) Na3PO4 reduced the removal percentage of Cd(II) at pH5. The Cd(II) adsorption was sensitive to changes in the concentration of NaCl, NaNO3, NaClO4, and Na3PO4. Besides, the adsorption isotherm of Cd(II) onto MGO-SA could be well described by the Freundlich model and was also influenced by the type of background electrolyte ions and the ionic strength. Copyright © 2014 Elsevier Inc. All rights reserved.

  17. Sorption of Am(III) on attapulgite/iron oxide magnetic composites. Effect of pH, ionic strength and humic acid

    Energy Technology Data Exchange (ETDEWEB)

    Yu, T. [Lanzhou Univ., Gansu (China). Radiochemistry Lab.; East China Institute of Technology, Fuzhou, Jiangxi (China). College of Chemistry, Biology and Materials Science; Fan, Q.H.; Wu, W.S. [Lanzhou Univ., Gansu (China). Radiochemistry Lab.; Lanzhou Univ., Gansu (China). State Key Laboratory of Applied Chemistry; Liu, S.P.; Pan, D.Q.; Zhang, Y.Y.; Li, P. [Lanzhou Univ., Gansu (China). Radiochemistry Lab.

    2012-07-01

    Attapulgite/iron oxide magnetic (ATP/IOM) composites was prepared, and the sorption behavior of Am(III) on that composites was studied as a function of pH, ionic strength, the solid-to-liquid ratio (m/V), contact time, and the concentration of Am(III) under ambient conditions using batch technique. The time to achieve the sorption equilibrium was less than 5 h. The sorption of Am(III) on ATP/IOM composites was strongly affected by pH and ionic strength. Though ion exchange reaction contributed to Am(III) sorption over low pH range and low ionic strength, the sorption was mainly dominated by surface complexion (i.e., outer- and/or inner-sphere complexes) in the whole observed pH range. In the presence of humic acid (HA), the sorption edge of Am(III) on ATP/IOM composites obviously shifted to lower pH; but Am(III) sorption gradually became weak after pH exceeded 4, which may be mainly in terms of the soluble complexes of HA-Am(III). (orig.)

  18. Sorption of vanadium (V) onto natural soil colloids under various solution pH and ionic strength conditions.

    Science.gov (United States)

    Luo, Xiuhua; Yu, Lin; Wang, Changzhao; Yin, Xianqiang; Mosa, Ahmed; Lv, Jialong; Sun, Huimin

    2017-02-01

    Batch sorption kinetics and isothermal characteristics of V(V) were investigated on three natural soil colloids (manual loessial soil colloid (MSC), aeolian sandy soil colloid (ASC), and cultivated loessial soil colloid (CSC)) under various solution pH and ionic strength (IS) conditions. Colloids were characterized by atomic force microscopy (AFM), X-ray diffraction (XRD), and fourier transform infrared spectroscopy (FTIR). AFM micrographs showed CSC with an aggregated shape with larger particle diameter as compared with ASC and MSC. XRD spectra revealed the presence of different minerals in natural soil colloids including biotite, kaolinite, calcite and quartz, which might contribute to sorption process. The sorption ability decreased with increase of colloidal particle size. The sorption was mainly attributed to complexation by active carboxylate and alcohol groups of colloidal components. Sorption kinetics and isotherms of V(V) onto natural soil colloids were best fitted with Pseudo-second-order and Freundlich models. Langmuir model indicated that sorption capacity of MSC and ASC was comparable (285.7 and 238.1 mg g-1); however, CSC exhibited the lowest sorption capacity (41.5 mg g-1) due to its larger particle diameter and aggregated shape. The maximum V(V) sorption capacity reached plateau values at a solution pH ranged between 5.0 and 9.0 for MSC and ASC, and 6.0-8.0 for CSC. Sorption capacity of V(V) onto natural soil colloids decreased with increasing IS. Based on result of this study we can conclude that sorption of V(V) onto natural soil colloids is pH- and IS-dependent. These findings provide insights on the remediation of vanadium-contaminated soils. Copyright © 2016 Elsevier Ltd. All rights reserved.

  19. Structures of self-assembled amphiphilic peptide-heterodimers: effects of concentration, pH, temperature and ionic strength

    KAUST Repository

    Luo, Zhongli

    2010-01-01

    The amphiphilic double-tail peptides AXG were studied regarding secondary structure and self-assembly in aqueous solution. The two tails A = Ala 6 and G = Gly6 are connected by a central pair X of hydrophilic residues, X being two aspartic acids in ADG, two lysines in AKG and two arginines in ARG. The peptide AD (Ala6Asp) served as a single-tail reference. The secondary structure of the four peptides was characterized by circular dichroism spectroscopy under a wide range of peptide concentrations (0.01-0.8 mM), temperatures (20-98 °C), pHs (4-9.5) and ionic strengths. In salt-free water both ADG and AD form a β-sheet type of structure at high concentration, low pH and low temperature, in a peptide-peptide driven assembly of individual peptides. The transition has a two-state character for ADG but not for AD, which indicates that the added tail in ADG makes the assembly more cooperative. By comparison the secondary structures of AKG and ARG are comparatively stable over the large range of conditions covered. According to dynamic light scattering the two-tail peptides form supra-molecular aggregates in water, but high-resolution AFM-imaging indicate that ordered (self-assembled) structures are only formed when salt (0.1 M NaCl) is added. Since the CD-studies indicate that the NaCl has only a minor effect on the peptide secondary structure we propose that the main role of the added salt is to screen the electrostatic repulsion between the peptide building blocks. According to the AFM images ADG and AKG support a correlation between nanofibers and a β-sheet or unordered secondary structure, whereas ARG forms fibers in spite of lacking β-sheet structure. Since the AKG and ARG double-tail peptides self-assemble into distinct nanostructures while their secondary structures are resistant to environment factors, these new peptides show potential as robust building blocks for nano-materials in various medical and nanobiotechnical applications. © 2010 The Royal Society

  20. Transport and abatement of fluorescent silica nanoparticle (SiO2 NP) in granular filtration: effect of porous media and ionic strength

    Science.gov (United States)

    Zeng, Chao; Shadman, Farhang; Sierra-Alvarez, Reyes

    2017-03-01

    The extensive production and application of engineered silica nanoparticles (SiO2 NPs) will inevitably lead to their release into the environment. Granular media filtration, a widely used process in water and wastewater treatment plants, has the potential for NP abatement. In this work, laboratory-scale column experiments were performed to study the transport and retention of SiO2 NPs on three widely used porous materials, i.e., sand, anthracite, and granular activated carbon (GAC). Synthetic fluorescent core-shell SiO2 NPs (83 nm) were used to facilitate NP detection. Sand showed very low capacity for SiO2 filtration as this material had a surface with limited surface area and a high concentration of negative charge. Also, we found that the stability and transport of SiO2 NP were strongly dependent on the ionic strength of the solution. Increasing ionic strength led to NP agglomeration and facilitated SiO2 NP retention, while low ionic strength resulted in release of captured NPs from the sand bed. Compared to sand, anthracite and GAC showed higher affinity for SiO2 NP capture. The superior capacity of GAC was primarily due to its porous structure and high surface area. A process model was developed to simulate NP capture in the packed bed columns and determine fundamental filtration parameters. This model provided an excellent fit to the experimental data. Taken together, the results obtained indicate that GAC is an interesting material for SiO2 NP filtration.

  1. Effects of ionic strength on the surface tension and nonequilibrium interfacial characteristics of poly(sodium styrenesulfonate)/dodecyltrimethylammonium bromide mixtures.

    Science.gov (United States)

    Ábrahám, Ágnes; Kardos, Attila; Mezei, Amália; Campbell, Richard A; Varga, Imre

    2014-05-06

    We rationalize the surface tension behavior and nonequilibrium interfacial characteristics of high molecular weight poly(sodium styrenesulfonate)/dodecyltrimethylammonium bromide (NaPSS/DTAB) mixtures with respect to the ionic strength. Excellent agreement is achieved between experimental data and our recent empirical model [Langmuir 2013, 29, 11554], which is based on the lack of colloidal stability of bulk aggregates in the phase separation region and has no free fitting parameters. We show that the size of a surface tension peak positioned at the edge of the phase separation region can be suppressed by the addition of inert electrolyte, which lowers the critical micelle concentration in relation to the phase separation region. Such manipulation of the peak is possible for the 100 ppm NaPSS/DTAB system because there is a high free surfactant concentration in the phase separation region. The close agreement of our model with the experimental data of samples in the phase separation region with respect to the ionic strength indicates that the surface tension behavior can be rationalized in terms of comprehensive precipitation regardless of whether there is a peak or not. The time scale of precipitation for the investigated system is on the order of one month, which emphasizes the need to understand the dynamic changes in the state of bulk aggregation in order to rationalize the surface properties of strongly interacting mixtures; steady state surface properties measured in the interim period will represent samples far from equilibrium. We show also that the surface properties of samples of low ionic strength outside the equilibrium phase separation region can be extreme opposites depending on the sample history, which is attributed to the generation of trapped nonequilibrium states. This work highlights the need to validate the underlying nature of oppositely charged polyelectrolyte/surfactant systems prior to the interpretation of experimental data within an

  2. Transport and abatement of fluorescent silica nanoparticle (SiO{sub 2} NP) in granular filtration: effect of porous media and ionic strength

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Chao, E-mail: chaozeng@email.arizona.edu; Shadman, Farhang; Sierra-Alvarez, Reyes [University of Arizona, Department of Chemical and Environmental Engineering (United States)

    2017-03-15

    The extensive production and application of engineered silica nanoparticles (SiO{sub 2} NPs) will inevitably lead to their release into the environment. Granular media filtration, a widely used process in water and wastewater treatment plants, has the potential for NP abatement. In this work, laboratory-scale column experiments were performed to study the transport and retention of SiO{sub 2} NPs on three widely used porous materials, i.e., sand, anthracite, and granular activated carbon (GAC). Synthetic fluorescent core-shell SiO{sub 2} NPs (83 nm) were used to facilitate NP detection. Sand showed very low capacity for SiO{sub 2} filtration as this material had a surface with limited surface area and a high concentration of negative charge. Also, we found that the stability and transport of SiO{sub 2} NP were strongly dependent on the ionic strength of the solution. Increasing ionic strength led to NP agglomeration and facilitated SiO{sub 2} NP retention, while low ionic strength resulted in release of captured NPs from the sand bed. Compared to sand, anthracite and GAC showed higher affinity for SiO{sub 2} NP capture. The superior capacity of GAC was primarily due to its porous structure and high surface area. A process model was developed to simulate NP capture in the packed bed columns and determine fundamental filtration parameters. This model provided an excellent fit to the experimental data. Taken together, the results obtained indicate that GAC is an interesting material for SiO{sub 2} NP filtration.

  3. Influence of ionic strength and pH on the limitation of latex microsphere deposition sites on iron-oxide coated sand by humic acid

    Energy Technology Data Exchange (ETDEWEB)

    Yang, X. [School of Planning, Architecture and Civil Engineering, Queen' s University Belfast, David Keir Building, Stranmillis Road, Belfast BT9 5AG, N. Ireland (United Kingdom); Flynn, R., E-mail: r.flynn@qub.ac.uk [School of Planning, Architecture and Civil Engineering, Queen' s University Belfast, David Keir Building, Stranmillis Road, Belfast BT9 5AG, N. Ireland (United Kingdom); Kammer, F. von der, E-mail: frank.von.der.kammer@univie.ac.at [Department of Environmental Geosciences, University of Vienna, Althanstrasse 14, 1090 Vienna (Austria); Hofmann, T. [Department of Environmental Geosciences, University of Vienna, Althanstrasse 14, 1090 Vienna (Austria)

    2011-07-15

    This study, for the first time, investigates and quantifies the influence of slight changes in solution pH and ionic strength (IS) on colloidal microsphere deposition site coverage by Suwannee River Humic Acid (SRHA) in a column matrix packed with saturated iron-oxide coated sand. Triple pulse experimental (TPE) results show adsorbed SRHA enhances microsphere mobility more at higher pH and lower IS and covers more sites than at higher IS and lower pH. Random sequential adsorption (RSA) modelling of experimental data suggests 1 {mu}g of adsorbed SRHA occupied 9.28 {+-} 0.03 x 10{sup 9} sites at pH7.6 and IS of 1.6 mMol but covered 2.75 {+-} 0.2 x 10{sup 9} sites at pH6.3 and IS of 20 mMol. Experimental responses are suspected to arise from molecular conformation changes whereby SRHA extends more at higher pH and lower ionic strength but is more compact at lower pH and higher IS. Results suggest effects of pH and IS on regulating SRHA conformation were additive. - Highlights: > We quantified the coupled role of pH and IS and humic acid on colloid deposition. > Humic acid enhances microsphere mobility more at higher pH and lower IS. > pH and IS may control the behaviour of humic acid by regulating its conformation. > The effect of pH and IS on regulating humic acid conformation is additive. - This paper quantifies the impact of pH and ionic strength on the transient deposition behaviour of colloids in porous medium in the presence of humic acid.

  4. Calculation of the high-temperature strength of complexly alloyed nickel alloys using equations of the system of nonpolarized ionic radii

    Science.gov (United States)

    Ovsepyan, S. V.; Lomberg, B. S.; Baburina, E. V.

    1995-06-01

    Modern complexly alloyed high-temperature nickel-base alloys contain up to 14 alloying elements. The complex composition ensures fulfillment of strict and often contradictory requirements imposed on the materials of critical parts of gas turbine engines (GTE). However, multi-component alloying creates considerable difficulties in the development of new compositions with specified characteristics or in the optimization of existing alloys. The present work is devoted to calculating the high-temperature strength of nickel alloys by means of the system of nonpolarized ionic radii (SNIR).

  5. Coagulation-flocculation of TiO2 in Suspension Used in Heterogeneous Photocatalysis

    Directory of Open Access Journals (Sweden)

    Jomilson M. Santos

    2014-01-01

    Full Text Available The coagulation-flocculation of TiO2 in aqueous suspensions of low and intermediate ionic strength was investigated as a function of pH, of addition of aluminum sulfate and of stirring the suspension. This process was maximized after the addition of aluminum sulfate when the mixture was subjected to rapid and slow shaking and by using tap water at pH 7.0. Under these conditions, the turbidity of a suspension with 0.5 g L-1 of TiO2, which is higher than 4000 NTU, can be lowered to less than 10 NTU in 120 minutes. The filtration of the remaining suspension after coagulation-flocculation was 70 times faster than that of the initial suspension.

  6. Ionic strength and composition govern the elasticity of biological membranes. A study of model DMPC bilayers by force- and transmission IR spectroscopy.

    Science.gov (United States)

    Šegota, Suzana; Vojta, Danijela; Pletikapić, Galja; Baranović, Goran

    2015-02-01

    Infrared (IR) spectroscopy was used to quantify the ion mixture effect of seawater (SW), particularly the contribution of Mg(2+) and Ca(2+) as dominant divalent cations, on the thermotropic phase behaviour of 1,2-dimyristoyl-sn-glycero-3-posphocholine (DMPC) bilayers. The changed character of the main transition at 24 °C from sharp to gradual in films and the 1 °C shift of the main transition temperature in dispersions reflect the interactions of lipid headgroups with the ions in SW. Force spectroscopy was used to quantify the nanomechanical hardness of a DMPC supported lipid bilayer (SLB). Considering the electrostatic and ion binding equilibrium contributions while systematically probing the SLB in various salt solutions, we showed that ionic strength had a decisive influence on its nanomechanics. The mechanical hardness of DMPC SLBs in the liquid crystalline phase linearly increases with the increasing fraction of all ion-bound lipids in a series of monovalent salt solutions. It also linearly increases in the gel phase but almost three times faster (the corresponding slopes are 4.9 nN/100 mM and 13.32 nN/100 mM, respectively). We also showed that in the presence of divalent ions (Ca(2+) and Mg(2+)) the bilayer mechanical hardness was unproportionally increased, and that was accompanied with the decrease of Na(+) ion and increase of Cl(-) ion bound lipids. The underlying process is a cooperative and competitive ion binding in both the gel and the liquid crystalline phase. Bilayer hardness thus turned out to be very sensitive to ionic strength as well as to ionic composition of the surrounding medium. In particular, the indicated correlation helped us to emphasize the colligative properties of SW as a naturally occurring complex ion mixture. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  7. Effect of pH, ionic strength, foreign ions, humic acid and temperature on Zn(II) sorption onto γ-Al{sub 2}O{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Jiang; Zhang, Wei; Liu, Xia; Chen, Yuantao [Qinghai Normal University, Qinghai (China); Zhao, Lanping [Education Training Center of Ningxia Electric Power Company, Ningxia (China)

    2014-02-15

    The sorption of Zn(II) on γ-alumina was investigated as a function of contact time, pH, ionic strength, foreign ions, solid amount, humic acid (HA) and temperature by using batch technique. The results indicated that the sorption of Zn(II) onto γ-alumina was strongly dependent on pH and ionic strength. The sorption of Zn(II) increased slowly with increasing pH at pH 2-5, then increased sharply with pH increasing from 5 to 8.5, and at last maintained a maximum value at pH>8.5. A positive effect of HA on Zn(II) sorption was found at pH<7, whereas a negative effect was observed at pH>7. The thermodynamic data (ΔG{sup 0}, ΔS{sup 0}, ΔH{sup 0}) were calculated from the temperature-dependent sorption isotherms, and the results suggested that the sorption of Zn(II) on γ-alumina was endothermic and spontaneous. The sorption results revealed that the γ-alumina can be as a cost-effective sorbent for pre-concentration of Zn(II) from large volumes of aqueous solutions in environmental pollution cleanup.

  8. Effect of humic acid, fulvic acid, pH, ionic strength and temperature on {sup 63}Ni(II) sorption to MnO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Sheng, G.; Wang, X. [School of Nuclear Science and Engineering, North China Electric Power Univ., BJ (China); Key Lab. of Novel Thin Film Solar Cells, Inst. of Plasma Physics, Chinese Academy of Sciences, Hefei (China); Hu, J.; Yang, S.; Ren, X.; Li, J. [Key Lab. of Novel Thin Film Solar Cells, Inst. of Plasma Physics, Chinese Academy of Sciences, Hefei (China); Jin, H. [National Synchrotron Radiation Lab., Univ. of Science and Technology of China, Hefei, AH (China); Chen, Y. [School of Nuclear Science and Engineering, North China Electric Power Univ., BJ (China)

    2010-07-01

    The effects of pH, ionic strength, temperature, humic acid (HA) and fulvic acid (FA) on the sorption of radionuclide {sup 63}Ni(II) to MnO{sub 2} have been investigated by using batch techniques. The results indicated that the sorption of {sup 63}Ni(II) on MnO{sub 2} is obviously dependent on pH values but independent of ionic strength. The presence of HA/FA strongly enhances the sorption of {sup 63}Ni(II) on MnO{sub 2} at low pH values, whereas reduces {sup 63}Ni(II) sorption at high pH values. The sorption of {sup 63}Ni(II) on MnO{sub 2} is attributed to inner-sphere surface complexation rather than outer-sphere surface complexation or ion exchange. The diffuse layer model (DLM) is used to simulate the experimental data well with the aid of FITEQL 3.2. The thermodynamic parameters ({delta}H{sup 0}, {delta}S{sup 0}, {delta}G{sup 0}) are also calculated from the temperature dependent sorption isotherms, and the results suggest that the sorption of {sup 63}Ni(II) on MnO{sub 2} is a spontaneous and endothermic process. (orig.)

  9. Adsorption of Eu(III) onto TiO{sub 2}: Effect of pH, concentration, ionic strength and soil fulvic acid

    Energy Technology Data Exchange (ETDEWEB)

    Tan Xiaoli, E-mail: tanxl@ipp.ac.cn [Key Lab of New Thin Film Solar Cells, Institute of Plasma Physics, Chinese Academy of Sciences, P.O. Box 1126, Hefei, 230031 Anhui (China); School of Nuclear Science and Engineering, North China Electric Power University, Beijing, 102206 (China); Fang Ming [Institute of Solid States Physics, Chinese Academy of Sciences, P.O. Box 1129, Hefei, 230031 Anhui (China); Li Jiaxing; Lu Yi [Key Lab of New Thin Film Solar Cells, Institute of Plasma Physics, Chinese Academy of Sciences, P.O. Box 1126, Hefei, 230031 Anhui (China); Wang Xiangke, E-mail: xkwang@ipp.ac.cn [Key Lab of New Thin Film Solar Cells, Institute of Plasma Physics, Chinese Academy of Sciences, P.O. Box 1126, Hefei, 230031 Anhui (China); School of Nuclear Science and Engineering, North China Electric Power University, Beijing, 102206 (China)

    2009-08-30

    The effects of pH, initial Eu(III) concentration, ionic strength and fulvic acid (FA) on the adsorption of Eu(III) on TiO{sub 2} are investigated by using batch techniques. The results indicate that the presence of FA strongly enhances the adsorption of Eu(III) on TiO{sub 2} at low pH values. Besides, the adsorption of Eu(III) on TiO{sub 2} is significantly dependent on pH values and independent of ionic strength. The adsorption of Eu(III) on TiO{sub 2} is attributed to inner-sphere surface complexation. The diffuse layer model (DLM) is applied to simulate the adsorption data, and fits the experimental data well with the aid of FITEQL 3.2. X-ray photoelectron spectroscopy (XPS) is performed to study the species of Eu(III) adsorbed on the surfaces of TiO{sub 2}/FA-TiO{sub 2} hybrids at a molecular level, which suggest that FA act as 'bridge' between Eu(III) and TiO{sub 2} particles to enhance the ability to adsorb Eu(III) in solution.

  10. High Conductivity, High Strength Solid Electrolytes Formed by in Situ Encapsulation of Ionic Liquids in Nanofibrillar Methyl Cellulose Networks.

    Science.gov (United States)

    Mantravadi, Ramya; Chinnam, Parameswara Rao; Dikin, Dmitriy A; Wunder, Stephanie L

    2016-06-01

    Strong, solid polymer electrolyte ion gels, with moduli in the MPa range, a capacitance of 2 μF/cm(2), and high ambient ionic conductivities (>1 × 10(-3) S/cm), all at room temperature, have been prepared from butyl-N-methyl pyrrolidinium bis(trifluoromethylsulfonyl) imide (PYR14TFSI) and methyl cellulose (MC). These properties are particularly attractive for supercapacitor applications. The ion gels are prepared by codissolution of PYR14TFSI and MC in N,N-dimethylformamide (DMF), which after heating and subsequent cooling form a gel. Evaporation of DMF leave thin, flexible, self-standing ion gels with up to 97 wt % PYR14TFSI, which have the highest combined moduli and ionic conductivity of ion gels to date, with an excellent electrochemical stability window (5.6 V). These favorable properties are attributed to the immiscibility of PYR14TFSI in MC, which permits the ionic conductivity to be independent of the MC at low MC content, and the in situ formation of a volume spanning network of semicrystalline MC nanofibers, which have a high glass transition temperature (Tg = 190 °C) and remain crystalline until they degrade at 300 °C.

  11. Drug release from E chemistry hypromellose tablets using the Bio-Dis USP type III apparatus: An evaluation of the effect of systematic agitation and ionic strength.

    Science.gov (United States)

    Asare-Addo, Kofi; Supuk, Enes; Mahdi, Mohammed H; Adebisi, Adeola O; Nep, Elijah; Conway, Barbara R; Kaialy, Waseem; Al-Hamidi, Hiba; Nokhodchi, Ali

    2016-07-01

    The aim of the study was to evaluate the effect of systematic agitation, increasing ionic strength and gel strength on drug release from a gel-forming matrix (HPMC E10M, E4M and E50LV) using USP type III Bio-Dis apparatus with theophylline as a model drug. The triboelectric charging; particle sizing, water content, true density and SEM of all the hypromellose grades, theophylline and formulated blends were characterised. The results showed that balanced inter-particulate forces exist between drug particles and the excipient surface and this enabled optimum charge to mass ratio to be measured. Agitation and ionic strength affected drug release from E50LV and E4M tablet matrices in comparison to the E10M tablet matrices. Drug release increased substantially when water was used as the dissolution media relative to media at pH 1.2 (containing 0.4M NaCl). The results showed all f2 values for the E10M tablet matrices were above 50 suggesting the drug release from these tablet matrices to be similar. Rheological data also explained the different drug release behaviour with the stress required to yield/erode being 1Pa, 150Pa, and 320Pa, for the E50LV, E4M and E10M respectively. The stiffness of the gel was also found to be varied from 2.5Pa, 176.2Pa and 408.3Pa for the E50LV, E4M and E10M respectively. The lower G' value can be explained by a softer gel being formed after tablet introduction into the dissolution media thereby indicating faster drug release. Copyright © 2016 Elsevier B.V. All rights reserved.

  12. Reaction product variability and biological activity of the lactoperoxidase system depending on medium ionic strength and pH, and on substrate relative concentration.

    Science.gov (United States)

    Bafort, Françoise; Damblon, Christian; Smargiasso, Nicolas; De Pauw, Edwin; Perraudin, Jean-Paul; Jijakli, M Haïssam

    2017-12-20

    The potential of ions produced in water by the lactoperoxidase system against plant pests has shown promising results. We tested the bioactivity of ions produced by the lactoperoxidase oxidation of I- and SCN- in several buffers or in tap water and characterized the ions produced. In vitro biological activity was tested against Penicillium expansum, the causal agent of mold in fruits, and the major cause of patulin contamination of fruit juices and compotes. In buffers, the ionic concentration was increased 3-fold, and pathogen inhibition was obtained down to the 1/15 dilution. In tap water, the ionic concentration was weaker, and pathogen inhibition was obtained only down to the 1/3 dilution. Acidic buffer increased ion concentrations as compared to less acidic (pH 5.6 or 6.2) or neutral buffers, as do increased ionic strength. 13 C-labelled SCN- and MS showed that different ions were produced in water and in buffers. In specific conditions the ion solution turned yellow and a product was formed, probably diiodothiocyanate (I2 SCN- ), giving an intense signal at 49.7 ppm in 13 C NMR. The formation of the signal was unambiguously favored in acidic media and disadvantaged or inhibited in neutral or basic conditions. It was enhanced at a specific SCN- : I- ratio of 1:4.5, but decreased when the ratio was 1:2, and was inhibited at ratio SCN- >I- . We demonstrated that the formation of the signal required the interaction between I2 and SCN- , and MS showed the presence of I2 SCN- . This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  13. Assessment of the Effects of Flow Rate and Ionic Strength on the Performance of an Air-Cathode Microbial Fuel Cell Using Electrochemical Impedance Spectroscopy

    Directory of Open Access Journals (Sweden)

    Doug Aaron

    2010-03-01

    Full Text Available Impedance changes of the anode, cathode and solution were examined for an air-cathode microbial fuel cell (MFC under varying conditions. An MFC inoculated with a pre-enriched microbial culture resulted in a startup time of less than ten days. Over this period, the anode impedance decreased below the cathode impedance, suggesting a cathode-limited power output. Increasing the anode flow rate did not impact the anode impedance significantly, but it decreased the cathode impedance by 65%. Increasing the anode-medium ionic strength also decreased the cathode impedance. These impedance results provide insight into electron and proton transport mechanisms and can be used to improve MFC performance.

  14. Kinetics of nitrate adsorption and reduction by nano-scale zero valent iron (NZVI): Effect of ionic strength and initial pH

    DEFF Research Database (Denmark)

    Kim, Do-Gun; Hwang, Yuhoon; Shin, Hang-Sik

    2016-01-01

    Kinetic models for pollutants reduction by Nano-scale Zero Valent Iron (NZVI) were tested in this study to gain a better understanding and description of the reaction. Adsorption kinetic models and a heterogeneous catalytic reaction kinetic equation were proposed for nitrate removal and for ammonia...... generation, respectively. A widely used pseudo-first-order reaction model was a poor fit for nitrate removal in an iron-limiting condition and for ammonia generation in an excess iron condition. However, in this study, pseudo-first-order and pseudo-second-order adsorption kinetic equations were a good fit...... for nitrate removal; in addition, a Langmuir-Hinshelwood kinetic equation was able to successfully describe ammonia generation, regardless of the NZVI dose, the ionic strength, and the initial pH. These results strongly indicate that nitrate reduction by NZVI is a heterogeneous catalytic reaction...

  15. Inkjet-printed gold nanoparticle chemiresistors: Influence of film morphology and ionic strength on the detection of organics dissolved in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Chow, Edith [CSIRO Materials Science and Engineering, PO Box 218, Lindfield, NSW 2070 (Australia)], E-mail: Edith.Chow@csiro.au; Herrmann, Jan; Barton, Christopher S.; Raguse, Burkhard; Wieczorek, Lech [CSIRO Materials Science and Engineering, PO Box 218, Lindfield, NSW 2070 (Australia)

    2009-01-19

    The influence of film morphology on the performance of inkjet-printed gold nanoparticle chemiresistors has been investigated. Nanoparticles deposited from a single-solvent system resulted in a 'coffee ring'-like structure with most of the materials deposited at the edge. It was shown that the uniformity of the film could be improved if the nanoparticles were deposited from a mixture of solvents comprising N-methyl-2-pyrrolidone and water. Electrical conductivity measurements showed that both 'coffee ring' and 'flat' films were qualitatively similar suggesting that the films have similar nanoscale structures. To form the functional chemiresistor device, the 4-(dimethylamino)pyridine coating on the nanoparticle was exchanged with 1-hexanethiol to provide a hydrophobic sensing layer. The performance of 1-hexanethiol coated gold nanoparticle chemiresistors to small organic molecules, toluene, dichloromethane and ethanol dissolved in 1 M KCl in regard to changes in impedance and response times was unaffected by the film morphology. For larger hydrocarbons such as octane, the rate of uptake of the analyte into the film was significantly faster when the flatter nanoparticle film was used as opposed to the 'coffee ring' film which has a thicker edge. Furthermore, the presence of potassium and chloride ions in the solution media does not significantly affect the impedance of the nanoparticle film at 1 Hz (<2% variation in film impedance over more than four orders of magnitude change in ionic strength). However, the ionic strength of the media affected the partitioning of the analyte into the hydrophobic nanoparticle film. The response of the sensor was found to increase with an increased salt concentration due to a salting-out of the analyte from the solution.

  16. Sorption of Ni(II) on GMZ bentonite: Effects of pH, ionic strength, foreign ions, humic acid and temperature

    Energy Technology Data Exchange (ETDEWEB)

    Yang Shitong [School of Nuclear Science and Engineering, North China Electric Power University, Beijing 102206 (China); Key Lab of Novel Thin Film Solar Cells, Institute of Plasma Physics, Chinese Academy of Sciences, P.O. Box 1126, 230031 Hefei (China); Li Jiaxing; Lu Yi [Key Lab of Novel Thin Film Solar Cells, Institute of Plasma Physics, Chinese Academy of Sciences, P.O. Box 1126, 230031 Hefei (China); Chen Yixue [School of Nuclear Science and Engineering, North China Electric Power University, Beijing 102206 (China); Wang Xiangke [School of Nuclear Science and Engineering, North China Electric Power University, Beijing 102206 (China); Key Lab of Novel Thin Film Solar Cells, Institute of Plasma Physics, Chinese Academy of Sciences, P.O. Box 1126, 230031 Hefei (China)], E-mail: xkwang@ipp.ac.cn

    2009-09-15

    Bentonite has been widely studied in nuclear waste management because of its special physicochemical properties. In this work, the sorption of Ni(II) from aqueous solution onto GMZ bentonite as a function of contact time, pH, ionic strength, foreign ions, humic acid (HA) and temperature was investigated under ambient conditions. The results indicated that the pseudo-second-order rate equation simulated the kinetic sorption process well. The sorption of Ni(II) on GMZ bentonite was strongly dependent on pH and on ionic strength. At low pH, the sorption of Ni(II) was dominated by outer-sphere surface complexation and ion exchange with Na{sup +}/H{sup +} on GMZ bentonite surfaces, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. A positive effect of HA on Ni(II) sorption was found at pH<8, whereas a negative effect was observed at pH>8. The Langmuir, Freundlich, and D-R models were used to simulate the sorption isotherms of Ni(II) at three different temperatures: 303.15, 318.15 and 333.15 K. The thermodynamic parameters ({delta}H{sup 0}, {delta}S{sup 0} and {delta}G{sup 0}) of Ni(II) sorption on GMZ bentonite at the three different temperatures were calculated from the temperature-dependent sorption isotherms. The results indicated that the sorption process of Ni(II) on GMZ bentonite was endothermic and spontaneous. Experimental results indicate that GMZ bentonite is a suitable sorbent for pre-concentration and solidification of Ni(II) from large volume solutions.

  17. Sorption of Th (IV) to silica as a function of pH, humic/fulvic acid, ionic strength, electrolyte type

    Energy Technology Data Exchange (ETDEWEB)

    Chen Changlun [Institute of Plasma Physics, Chinese Academy of Sciences, P.O. Box 1126, Hefei, 230031, Anhui (China)]. E-mail: clchen@ipp.ac.cn; Wang Xiangke [Institute of Plasma Physics, Chinese Academy of Sciences, P.O. Box 1126, Hefei, 230031, Anhui (China)]. E-mail: xkwang@ipp.ac.cn

    2007-02-15

    The removal behavior of thorium (Th(IV)) has been investigated in multicomponent systems containing silica (SiO{sub 2}) as the model of inorganic particles because of its widespread presence in the earth's crust and soil humic acid (HA)/fulvic acid (FA) by batch experiments. The influence of pH from 2 to 12, ionic strength from 0.02 to 0.2 M KNO{sub 3}, soil HA/FA concentration from 8.3 to 22.5 mg/L, and foreign cations (Li{sup +}, Na{sup +}, K{sup +}) and anions (NO{sub 3} {sup -}, Cl{sup -}) on the sorption of Th(IV) onto SiO{sub 2} was also tested. The sorption isotherms of Th(IV) at approximately constant pH (3.50{+-}0.02) were determined and analyzed regressively with three kinds of sorption isotherm models, i.e., linear, Langmuir, and Freundlich models. The results demonstrated that the sorption of Th(IV) onto SiO{sub 2} increased steeply with increasing pH from 2 to 4. Generally, humic substances (HSs) were shown to enhance Th(IV) sorption at low pH, but to reduce Th(IV) sorption at intermediate and high pH. It was a hypothesis that the significantly positive influence of HA/FA at pH from 2 to 4 on the sorption of Th(IV) onto SiO{sub 2} was attributed to strong surface binding of HA/FA on SiO{sub 2} and subsequently the formation of ternary surface complexes such as {identical_to}MO-O-HA-Th or {identical_to}MO-O-FA-Th. The results also demonstrated that the sorption was strongly dependent on the concentration of HA/FA, and independent of ionic strength and foreign ions under our experimental conditions.

  18. Sorption of Eu(III) and Am(III) on attapulgite. Effect of pH, ionic strength and fulvic acid

    Energy Technology Data Exchange (ETDEWEB)

    Fan, Q.H.; Wu, W.S. [Radiochemistry Lab., School of Nuclear Science and Tech., Lanzhou Univ., GS (China); State Key Lab. of Applied Organic Chemistry, Lanzhou Univ., GS (China); Zhang, M.L.; Zhang, Y.Y.; Ding, K.F.; Yang, Z.Q. [Radiochemistry Lab., School of Nuclear Science and Tech., Lanzhou Univ., GS (China)

    2010-07-01

    Sorption of Eu(III) and Am(III) on attapulgite were studied as a function of pH, ionic strength, the liquid-to-solid ratio (V/m), and Eu(III) and Am(III) concentrations under ambient conditions using batch technique. The sorption of Eu(III) and Am(III) was quickly and {proportional_to} 4 hours were enough to achieve the sorption equilibrium. The K' values were 6.57 x 10{sup 6} g mg{sup -1} h{sup -1} for Eu(III) and 6.67 x 106 g mg{sup -1} h{sup -1} for Am(III), respectively; and q{sub e} values were 4.46 x 10{sup -7} mg/g for Eu(III) and 1.0 x 10{sup -6} mg/g for Am(III), respectively. Sorption of Eu(III) and Am(III) on attapulgite were strongly affected by pH values, and weakly dependent on ionic strength. Sorption of Eu(III) and Am(III) were mainly dominated by surface complexation. although ion exchange also contributed to Eu(III) and Am(III) sorption. In the presence of fulvic acid (FA), the sorption edge of Eu(III) and Am(III) was obviously shifted to lower pH. The results showed that the sorption of Eu(III) and Am(III) to attapulgite was enhanced significantly in the range of pH 0.5 to 6. (orig.)

  19. Long-Term Experimental Determination of Solubilities of Micro-Crystalline Nd(III) Hydroxide in High Ionic Strength Solutions: Applications to Nuclear Waste Management [A Pitzer Model for Am(III)/Nd(III) hydroxide solubility in NaCl-H2O at 298.15 K to high ionic strengths: Experimental validation and model applications

    Energy Technology Data Exchange (ETDEWEB)

    Xiong, Yongliang [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Carlsbad Programs Group; Kirkes, Leslie Dawn [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Carlsbad Programs Group; Marrs, Cassandra [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Carlsbad Programs Group

    2017-12-01

    In this paper, the experimental results from long-term solubility experiments on micro crystalline neodymium hydroxide, Nd(OH)3(micro cr), in high ionic strength solutions at 298.15 K under well-constrained conditions are presented. The starting material was synthesized according to a well-established method in the literature. In contrast with the previous studies in which hydrogen ion concentrations in experiments were adjusted with addition of either an acid or a base, the hydrogen ion concentrations in our experiments are controlled by the dissolution of Nd(OH)3(micro cr), avoiding the possibility of phase change.

  20. Enhancing the basicity of ionic liquids by tuning the cation-anion interaction strength and via the anion-tethered strategy.

    Science.gov (United States)

    Xu, Dan; Yang, Qiwei; Su, Baogen; Bao, Zongbi; Ren, Qilong; Xing, Huabin

    2014-01-30

    Ionic liquids (ILs) with relatively strong basicity often show impressive performance in chemical processes, so it is important to enhance the basicity of ILs by molecular design. Here, we proposed two effective ways to enhance the basicity of ILs: by weakening the cation-anion interaction strength and by employing the anion-tethered strategy. Notably, two quantum-chemical parameters, the most negative surface electrostatic potential and the lowest surface average local ionization energy, were adopted as powerful tools to demonstrate the electrostatic and covalent aspects of basicity, respectively, at the microscopic level. It was shown that, for the ILs with the same anion (acetate or trifluoroacetate), the basicity of the ILs could be enhanced when the cation-anion interaction strength was weakened. For the acetate anion-based ILs, the hydrogen-bonding basicity scale (β) increased by 29% when the cation changed from 1-butyl-3-methylimidazolium ([Bmim]) to tetrabutylphosphonium ([P4444]), achieving one of the highest reported β values for ILs. Moreover, it was also demonstrated that, when an amine group was tethered to the anion of the IL, its basicity was stronger than when it was tethered to the cation. These results are highly instructive for designing ILs with strong basicity and for improving the efficiency of IL-based processes, such as CO2 capture, SO2 and acetylene absorption, dissolution of cellulose, extraction of bioactive compounds, and so on.

  1. Enhancement of polar anchoring strength in a graphene-nematic suspension and its effect on nematic electro-optic switching

    Science.gov (United States)

    Basu, Rajratan

    2017-07-01

    A small quantity of monolayer graphene flakes is doped in a nematic liquid crystal (LC), and the effective polar anchoring strength coefficient between the LC and the alignment substrate is found to increase by an order of magnitude. The hexagonal pattern of graphene can interact with the LC's benzene rings via π -π electron stacking, enabling the LC to anchor to the graphene surface homogeneously (i.e., planar anchoring). When the LC cell is filled with the graphene-doped LC, some graphene flakes are preferentially attached to the alignment layer and modify the substrate's anchoring property. These spontaneously deposited graphene flakes promote planar anchoring at the substrate and the polar anchoring energy at alignment layer is enhanced significantly. The enhanced anchoring energy is found to impact favorably on the electro-optic response of the LC. Additional studies reveal that the nematic electro-optic switching is significantly faster in the LC-graphene hybrid than that of the pure LC.

  2. Adsorption of arsenate and arsenite by iron-treated activated carbon and zeolites: effects of pH, temperature, and ionic strength.

    Science.gov (United States)

    Payne, Kelly B; Abdel-Fattah, Tarek M

    2005-01-01

    Naturally occurring arsenic contaminates groundwater in many countries, including the United States, at levels greater than 10 microg l(-1), the current WHO guideline value, increasing the risk of skin, lung, bladder, and kidney cancer in millions of people. Arsenic toxicity is dependent on its chemical form; arsenite is more toxic due to its higher affinity for protein than arsenate. This study supports worldwide research efforts to obtain drinking water with arsenic levels below 10 microg l(-1). Batch adsorption kinetic and isotherm studies were conducted to compare and evaluate iron-treated adsorbents for arsenate and arsenite removal from aqueous media. Two iron treatments were investigated as well as the effects of varied pH, temperature, and ionic strength increases on adsorption effectiveness. Adsorbent materials such as activated carbon and naturally occurring zeolites (clinoptilolite and chabazite) were selected because of their relative low cost and because the zeolites are potential point-of-use materials for mitigating arsenic contaminated groundwater. Molecular sieves, Faujasite (13X) and Linde type A (5A) were selected because they provide a basis for comparison with previous studies and represent well-characterized materials. Iron-treated activated carbon and chabazite showed the most promise as low-cost arsenic adsorbents; activated carbon removed approximately 60% of arsenate and arsenite while chabazite removed approximately 50% of arsenate and 30% of arsenite. Modeling arsenate and arsenite adsorption by these adsorbents using the Langmuir and Freundlich isotherm expressions determined the adsorbents' capacity for arsenic removal from aqueous media. Arsenate removal by iron-treated activated carbon and clinoptilolite best fit the Langmuir model. Arsenate removal by iron-treated chabazite and arsenite removal by activated carbon, chabazite, and clinoptilolite best fit the Freundlich model. Applications of iron-modified activated carbon for

  3. Properties of silicon suspensions and slip-cast bodies

    Science.gov (United States)

    Sacks, M. D.; Scheiffele, G. W.

    1985-01-01

    The effect of varying pH, sonication times, and solid loading of silicon powder suspensions on the properties of powder/water suspensions and on the resulting pore characteristics of slip-cast bodies was studied. Aqueous suspensions of ground an aged silicon powder (of 0.3 micron median Stokes diameter and containing 1.3 vol pct Fe2O3 powder) were prepared, with solids loading in the range of 30-56 vol pct, and were adjusted to varying pH values by addition of either HCl or NH4OH or NaOH. Suspension aliquots were sonicated for 0, 15, 30, or 60 min. Suspensions were characterized by zeta potentials, ionic strength, and viscosity. Pore characteristics of cast bodies were determined by mercury porosimetry. It was found that intermediate pH values (pH 7-9), long sonication (60 min), and high solid loadings (56 vol pct) produced samples with highest green densities and smallest median pore radius.

  4. Incubating Isolated Mouse EDL Muscles with Creatine Improves Force Production and Twitch Kinetics in Fatigue Due to Reduction in Ionic Strength

    Science.gov (United States)

    Head, Stewart I.; Greenaway, Bronwen; Chan, Stephen

    2011-01-01

    Background Creatine supplementation can improve performance during high intensity exercise in humans and improve muscle strength in certain myopathies. In this present study, we investigated the direct effects of acute creatine incubation on isolated mouse fast-twitch EDL muscles, and examined how these effects change with fatigue. Methods and Results The extensor digitorum longus muscle from mice aged 12–14 weeks was isolated and stimulated with field electrodes to measure force characteristics in 3 different states: (i) before fatigue; (ii) immediately after a fatigue protocol; and (iii) after recovery. These served as the control measurements for the muscle. The muscle was then incubated in a creatine solution and washed. The measurement of force characteristics in the 3 different states was then repeated. In un-fatigued muscle, creatine incubation increased the maximal tetanic force. In fatigued muscle, creatine treatment increased the force produced at all frequencies of stimulation. Incubation also increased the rate of twitch relaxation and twitch contraction in fatigued muscle. During repetitive fatiguing stimulation, creatine-treated muscles took 55.1±9.5% longer than control muscles to lose half of their original force. Measurement of weight changes showed that creatine incubation increased EDL muscle mass by 7%. Conclusion Acute creatine application improves force production in isolated fast-twitch EDL muscle, and these improvements are particularly apparent when the muscle is fatigued. One likely mechanism for this improvement is an increase in Ca2+ sensitivity of contractile proteins as a result of ionic strength decreases following creatine incubation. PMID:21850234

  5. Incubating isolated mouse EDL muscles with creatine improves force production and twitch kinetics in fatigue due to reduction in ionic strength.

    Directory of Open Access Journals (Sweden)

    Stewart I Head

    Full Text Available BACKGROUND: Creatine supplementation can improve performance during high intensity exercise in humans and improve muscle strength in certain myopathies. In this present study, we investigated the direct effects of acute creatine incubation on isolated mouse fast-twitch EDL muscles, and examined how these effects change with fatigue. METHODS AND RESULTS: The extensor digitorum longus muscle from mice aged 12-14 weeks was isolated and stimulated with field electrodes to measure force characteristics in 3 different states: (i before fatigue; (ii immediately after a fatigue protocol; and (iii after recovery. These served as the control measurements for the muscle. The muscle was then incubated in a creatine solution and washed. The measurement of force characteristics in the 3 different states was then repeated. In un-fatigued muscle, creatine incubation increased the maximal tetanic force. In fatigued muscle, creatine treatment increased the force produced at all frequencies of stimulation. Incubation also increased the rate of twitch relaxation and twitch contraction in fatigued muscle. During repetitive fatiguing stimulation, creatine-treated muscles took 55.1±9.5% longer than control muscles to lose half of their original force. Measurement of weight changes showed that creatine incubation increased EDL muscle mass by 7%. CONCLUSION: Acute creatine application improves force production in isolated fast-twitch EDL muscle, and these improvements are particularly apparent when the muscle is fatigued. One likely mechanism for this improvement is an increase in Ca(2+ sensitivity of contractile proteins as a result of ionic strength decreases following creatine incubation.

  6. Chloride salt type/ionic strength and refrigeration effects on antioxidant enzymes and lipid oxidation in cattle, camel and chicken meat.

    Science.gov (United States)

    Gheisari, Hamid Reza; Motamedi, Hossien

    2010-10-01

    The effects of NaCl and KCl at varying ionic strengths on catalase and glutathione peroxidase (GSH-Px) activities and lipid oxidation in ground Longissimus dorsi (LD) of cattle and camel and breast muscle of chicken during refrigerated storage were studied. NaCl and KCl significantly increased 2-thiobarbituric reactive substances (TBARS) and peroxide values. TBARS and peroxide values increased and GSH-Px activity decreased during 4 day storage in the 4 degrees C, but catalase activity was stable. Salt type had no consistent effect on GSH-Px and catalase activities. Chicken samples had lower enzyme activities and TBARS content than cattle and camel. Their peroxide values were lower than camel samples. Camel meat showed higher catalase activity and TBARS content than cattle meat. Results indicated that negative correlation between lipid oxidation and GSH-Px activity and the accelerated lipid oxidation in salted meat may be partly related to a decrease in GSH-Px activity. Crown Copyright (c) 2010. Published by Elsevier Ltd. All rights reserved.

  7. Quartz crystal microbalance study of ionic strength and pH-dependent polymer conformation and protein adsorption/desorption on PAA, PEO, and mixed PEO/PAA brushes.

    Science.gov (United States)

    Delcroix, M F; Demoustier-Champagne, S; Dupont-Gillain, C C

    2014-01-14

    The conformation of polymer chains grafted on a substrate influences protein adsorption. In a previous study, adsorption/desorption of albumin was demonstrated on mixed poly(ethylene oxide) (PEO)/poly(acrylic acid) (PAA) brushes, triggered by solutions of adequate pH and ionic strength (I). In the present work, homolayers of PEO or PAA are submitted to saline solutions with pH from 3 to 9 and I from 10(-5) to 10(-1) M, and their conformation is evaluated in real time using quartz crystal microbalance with dissipation monitoring (QCM-D). Shrinkage/swelling of PAA chains and hydration and salt condensation in the brush are evidenced. The adsorption of human serum albumin (HSA) onto such brushes is also monitored in these different saline solutions, leading to a deep understanding of the influence of polymer chain conformation, modulated by pH and I, on protein adsorption. A detailed model of the conformation of PEO/PAA mixed brushes depending on pH and I is then proposed, providing a rationale for the identification of conditions for the successive adsorption and desorption of proteins on such mixed brushes. The adsorption/desorption of albumin on PEO/PAA is demonstrated using QCM-D.

  8. Co-transport of Pb(2+) and TiO2 nanoparticles in repacked homogeneous soil columns under saturation condition: Effect of ionic strength and fulvic acid.

    Science.gov (United States)

    Fang, Jing; Zhang, Keke; Sun, Peide; Lin, Daohui; Shen, Bing; Luo, Yan

    2016-11-15

    This study investigated the effects of suspended TiO2 nanoparticles (nTiO2) on the transport of Pb(2+) in saturated repacked soil columns under different ionic strengths (IS) and in the presence of fulvic acid (FA). Also, the contribution of soil colloids to the mobility of Pb(2+) was discussed. In the absence of nTiO2, little amount of Pb(2+) was detected in the effluent even in the presence of FA. However, the presence of nTiO2 significantly enhanced the mobility of Pb(2+) in soil columns under all tested conditions and nTiO2-associated Pb(2+) was the major migration species of Pb(2+). Increasing the solution IS decreased the nTiO2-associated Pb(2+) migration due to the significant decrease in the mobility of nTiO2 in soil. FA remarkably increased the nTiO2-associated Pb(2+) mobility in soil column, which was mainly to increase the mobility of nTiO2 in soil and decrease desorption rate of Pb(2+) from nTiO2 during transport. Moreover, nTiO2 significantly enhanced the release of Fe-Al soil colloids, which in turn was also responsible for the enhancement of Pb(2+) mobility in soil. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. Modeling and sensitivity analysis on the transport of aluminum oxide nanoparticles in saturated sand: effects of ionic strength, flow rate, and nanoparticle concentration.

    Science.gov (United States)

    Rahman, Tanzina; Millwater, Harry; Shipley, Heather J

    2014-11-15

    Aluminum oxide nanoparticles have been widely used in various consumer products and there are growing concerns regarding their exposure in the environment. This study deals with the modeling, sensitivity analysis and uncertainty quantification of one-dimensional transport of nano-sized (~82 nm) aluminum oxide particles in saturated sand. The transport of aluminum oxide nanoparticles was modeled using a two-kinetic-site model with a blocking function. The modeling was done at different ionic strengths, flow rates, and nanoparticle concentrations. The two sites representing fast and slow attachments along with a blocking term yielded good agreement with the experimental results from the column studies of aluminum oxide nanoparticles. The same model was used to simulate breakthrough curves under different conditions using experimental data and calculated 95% confidence bounds of the generated breakthroughs. The sensitivity analysis results showed that slow attachment was the most sensitive parameter for high influent concentrations (e.g. 150 mg/L Al2O3) and the maximum solid phase retention capacity (related to blocking function) was the most sensitive parameter for low concentrations (e.g. 50 mg/L Al2O3). Copyright © 2014 Elsevier B.V. All rights reserved.

  10. Solubilization of immune complexes in complement factor deficient sera and the influence of temperature, ionic strength and divalent cations on the solubilization reaction

    DEFF Research Database (Denmark)

    Baatrup, Gunnar; Petersen, Ivan; Svehag, Svend-Erik

    1984-01-01

    The complement-mediated solubilization (CMS) of immune complexes (IC) and the initial kinetics (IKS) of this reaction in human sera depleted of or deficient in C2, C3, C8, factors B, P and I were investigated. Sera depleted of B or P and those lacking native C3 or factor I showed virtually no CMS...... whereas the IKS and CMS capacity of a C8-deficient serum were within the reference range. The IKS of a C2-deficient serum was markedly retarded while the CMS capacity was normal. Addition of C2 normalized the kinetics of the reaction. There was a good correlation between the kinetics of CMS determined...... by a radioassay and kinetic data for the binding of C3b to preformed immune complexes. The CMS capacity reached maximum at 39-41 degrees C and at an ionic strength of approximately 0.20 mu. Selective chelation of Mg2+ completely abolished the CMS of IC. Maximal CMS was observed at Mg2+ concentration of about 2m...

  11. Synthesis and suspension rheology of titania nanoparticles grafted with zwitterionic polymer brushes.

    Science.gov (United States)

    Shao, Zhen; Yang, Youngjun; Lee, Hyunsuk; Kim, Jin Woong; Osuji, Chinedum O

    2012-11-15

    Titania nanoparticles were modified by free-radical graft polymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC) at the particle surface, resulting in the formation of a 1-2 nm thick polymer brush. The zwitterionic nature of the polymer layer suggests that the suspension stability is a delicate function of pH, as well as volume fraction, salt concentration and the presence of charged or un-charged additives which may act as depletants or to screen charge interactions in the system. In this context, we characterized the suspension rheology as a function of volume fraction, pH, ionic strength and the concentration of surfactants in the suspension. Near-neutral pH, the brush layer is effective in stabilizing particles against aggregation with Newtonian behavior observed for volume fractions approaching 14%. Flocculation of particles and an onset of shear-thinning behavior was observed on decreasing pH from near-neutral. Conversely, suspension stability was maintained on increasing pH from near-neutral. Likewise, flocculation could be quickly induced by the addition of salt and cationic surfactant in small amounts, but the suspensions displayed greater stability to anionic and non-ionic surfactant additives. These results have important implications for the successful formulation of complex fluids employing zwitterionic colloids. Copyright © 2012 Elsevier Inc. All rights reserved.

  12. Adsorption of non-ionic ABC triblock copolymers: Surface modification of TiO2 suspensions in aqueous and non-aqueous medium

    Science.gov (United States)

    Lerch, Jean-Philippe; Atanase, Leonard Ionut; Riess, Gérard

    2017-10-01

    A series of non-ionic ABC triblock copolymers, such as poly(butadiene)-b-poly(2-vinylpyrridine)-b-poly(ethylene oxide) (PB-P2VP-PEO) were synthesized by sequential anionic polymerizations. For these copolymers comprising an organo-soluble PB and a water-soluble PEO block, their P2VP middle block has been selected for its anchoring capacity on solid surfaces. The adsorption isotherms on TiO2 were obtained in heptane and in aqueous medium, as selective solvents. In both of these cases, the P2VP middle block provides the surface anchoring, whereas PB and PEO sequences are acting as stabilizing moieties in heptane and water respectively. By extension to ABC triblock copolymers of the scaling theory developed for diblock copolymers, the density of adsorbed chains could be correlated with the molecular characteristics of the PB-P2VP-PEO triblock copolymers. From a practical point a view, it could be demonstrated that these copolymers are efficient dispersing agents for the TiO2 pigments in both aqueous and non-aqueous medium.

  13. Electric permittivity of concentrated suspensions of elongated goethite particles.

    Science.gov (United States)

    Rica, R A; Jiménez, M L; Delgado, A V

    2010-03-15

    This paper describes an investigation on the electric permittivity of concentrated suspensions of non-spherical particles, specifically prolate spheroids. It is first discussed how the determination of the frequency (omega) dependence of the electric permittivity (a phenomenon traditionally known as LFDD or low-frequency dielectric dispersion) can provide ample information on the properties of the dispersed material (shape, size, state of aggregation, conductivity) and of its interface with the (typically aqueous) medium. The basic quantities are the strength and frequency dependence of the dipole moment induced by the applied field, and its dimensionless counterpart, the dipole coefficient, C(*)(omega). It is explicitly shown how the (complex) relative permittivity of the suspension, epsilon(r)(*)(omega), can be calculated from it. Two theoretical models on the polarizability of spheroidal colloidal particles will be used as theoretical starting point; one of them (Model I) explicitly considers two relaxations of the permittivity, each associated to one of the particle axes. The other (Model II) is a semi-analytical theory that yields an LFDD practically independent of the axial ratio of the particles. Both models are aimed to be used if the suspensions are dilute (low volume fraction of solids, phi), and here they are generalized to concentrated systems by means of a previously published approximate evaluation of the permittivity of concentrated suspensions. Experiments are performed in the 1 kHz-1 MHz frequency range on suspensions of elongated goethite particles; the effects of ionic strength, pH, and volume fraction are investigated, and the two models are fitted to the data. In reality, taking into account that the particles are non-uniformly charged (a fact that contributes to their instability), two zeta potentials (roughly representing the lateral surface and the tip of the spheroid) are used as parameters. The results indicate that, when experimental

  14. Oxygen isotope systematics in the aragonite-CO2-H2O-NaCl system up to 0.7 mol/kg ionic strength at 25 °C

    Science.gov (United States)

    Kim, Sang-Tae; Gebbinck, Christa Klein; Mucci, Alfonso; Coplen, Tyler B.

    2014-01-01

    To investigate the oxygen isotope systematics in the aragonite-CO2-H2O-NaCl system, witherite (BaCO3) was precipitated quasi-instantaneously and quantitatively from Na-Cl-Ba-CO2 solutions of seawater-like ionic strength (I = 0.7 mol/kg) at two pH values (~7.9 and ~10.6) at 25 °C. The oxygen isotope composition of the witherite and the dissolved inorganic carbon speciation in the starting solution were used to estimate the oxygen isotope fractionations between HCO3¯ and H2O as well as between CO3 2 and H2O. Given the analytical error on the oxygen isotope composition of the witherite and uncertainties of the parent solution pH and speciation, oxygen isotope fractionation between NaHCO3° and HCO3¯, as well as between NaCO3¯ and CO3 2, is negligible under the experimental conditions investigated. The influence of dissolved NaCl concentration on the oxygen isotope fractionation in the aragonite-CO2-H2O-NaCl system also was investigated at 25 °C. Aragonite was precipitated from Na-Cl-Ca-Mg-(B)-CO2 solutions of seawater-like ionic strength using passive CO2 degassing or constant addition methods. Based upon our new experimental observations and published experimental data from lower ionic strength solutions by Kim et al. (2007b), the equilibrium aragonite-water oxygen isotope fractionation factor is independent of the ionic strength of the parent solution up to 0.7 mol/kg. Hence, our study also suggests that the aragonite precipitation mechanism is not affected by the presence of sodium and chloride ions in the parent solution over the range of concentrations investigated.

  15. Effect of NaCl on ionic content and distribution in suspension-cultured cells of the halophyte Sonneratia alba versus the glycophyte Oryza sativa.

    Science.gov (United States)

    Hayatsu, Manabu; Suzuki, Suechika; Hasegawa, Ai; Tsuchiya, Shinpei; Sasamoto, Hamako

    2014-09-15

    The effect of a high concentration of NaCl on the intra- (cytoplasmic matrix and vacuole) and extracellular (cell wall) distribution of Na, Cl, K, Mg, Ca, S, and P was investigated in suspension-cultured cells of the mangrove halophyte Sonneratia alba and compared to cultured cells of glycophytic rice (Oryza sativa). No significant differences were observed in ultrastructural features of cluster cells of both species cultured with and without 50mM NaCl. Quantitative X-ray microanalysis of cryosections of the cells cultured in the presence of 50mM NaCl showed that the Na concentration ([Na]) and Cl concentration ([Cl]) significantly increased in all three cell components measured. In S. alba, the [Na] was highest in the vacuole and lowest in the cytoplasmic matrix, while the [Cl] was highest in the cell wall and lowest in the cytoplasmic matrix. In O. sativa, however, the [Na] and [Cl] were highest in the cell wall, and the [Na] was lowest in the cytoplasmic matrix. Thus, the possible activities for Na and Cl transport from the cytoplasmic matrix into the vacuole were greater in S. alba than in O. sativa, suggesting that halophilic mangrove cells gain salt tolerance by transporting Na and Cl into their vacuoles. In O. sativa, the addition of NaCl to the culture medium caused no significant changes to the intracellular concentrations of various elements, such as K, P, S, Ca, and Mg, which suggests the absence of a direct relationship with the transport Na and Cl. In contrast, a marked decrease in the Ca concentration ([Ca]) in the cytoplasmic matrix and vacuole and an approximately two-fold increase in the P concentration ([P]) in the cytoplasmic matrix were found in S. alba, suggesting that the decrease in the [Ca] is related to the halophilic nature of S. alba (as indicated by the inward movement of Na(+) and Cl(-)). The possible roles of a Na(+)/Ca(2+) exchange mechanism in halophilism and the effect of the [P] on the metabolic activity under saline conditions are

  16. Silver(I Extraction with Benzo-18-Crown-6 Ether from Water into 1,2-Dichloroethane: Analyses on Ionic Strength of the Phases and their Equilibrium Potentials

    Directory of Open Access Journals (Sweden)

    Yoshihiro Kudo

    2017-06-01

    Full Text Available Extraction constants (Kex & Kex± for the extraction of silver picrate (AgPic by benzo-18-crown-6 ether (B18C6 into 1,2-dichloroethane (DCE were determined at 298 K and various ionic strength (I-values of a water phase with or without excess HNO3. Here the symbols, Kex and Kex±, were defined as [AgLPic]DCE/P and [AgL+]DCE[Pic−]DCE/P with P = [Ag+][L]DCE[Pic−] and L = B18C6, respectively; [ ]DCE refers to the concentration of the corresponding species in the DCE phase at equilibrium. Simultaneously, KD,Pic (= [Pic−]DCE/[Pic−] and K1,DCE (= Kex/Kex± values for given I and IDCE values were determined, where the symbol IDCE shows I of the DCE phase. Also, equilibrium potential differences (Δφeq based on the Pic− transfer at the water/DCE interface were obtained from the analysis of the KD,Pic [= KD,PicS exp{−(F/RT Δφeq}] values; the symbol KD,PicS shows KD,Pic at Δφeq = 0 V. On the basis of these results, I dependences of logKex and logKex± and IDCE ones of logK1,DCE and logKex± were examined. Extraction experiments of AgClO4 and AgNO3 by B18C6 into DCE were done for comparison. The logKex±-versus-Δφeq plot for the above Ag(I extraction systems with Pic−, ClO4−, and NO3− gave a good positive correlation.

  17. Humic Substances-dependent Aggregation and Transport of Cerium Oxide Nanoparticles in Porous Media at Different pHs and Ionic Strengths

    Science.gov (United States)

    Mu, L.; Jacobson, A. R.; Darnault, C. J. G.

    2015-12-01

    Cerium oxide nanoparticles (CeO2 NPs) are commonly used in several fields and industries, such as chemical and pharmaceutical, due to both their physical and chemical properties. For example, they are employed in the manufacturing of catalysts, as fuel additives, and as polishing agents. The release and exposure to CeO2 NPs can occur during their fabrication, application, and waste disposal, as well as through their life-cycle and accidents. Therefore, the assessment of the dynamic nature of CeO2 NPs stability and mobilty in the environment is of paramount importance to establish the environmental and public health risks associated with their inevitable release in the environment. Humic substances are a key element of soils and have been revealed to possibly affect the fate and transport of nanoparticles in soils. Consequently, our present research aims at investigating the influence that different pHs, monovalent and divalent cations, Suwannee River humic acid, and Suwanee River fulvic acid have on the aggregation, transport, and deposition of CeO2 NPs. Batch studies performed with different concentrations of humic and fulvic acids associated with a wide spectrum of pHs and ionic strengths were examined. Key variables from these batch studies were then examined to simulate experimental conditions commonly encountered in the soil-water system to conduct column transport experiments in order to establish the fate and transport of CeO2 NPs in saturated porous media, which is a critical phase in characterizing the behavior of CeO2 NPs in subsurface environmental systems.

  18. [Comparison and optimization of total ionic strength adjustment buffer during detecting fluoride in trace serum sample by fluoride ion selective electrode method].

    Science.gov (United States)

    Zhou, Zhou; Wang, Hongmei; Zhang, Han; Chen, Yanqing

    2016-03-01

    To probe on the influence by four kinds of total ionic strength regulating buffer (TISAB) in establishing the standard curve and determining the level of fluoride in trace serum sample (rats serum and the calf serum) by fluoride ion selective electrode, and further explore the optimal volume ratio among TISAB and serum samples. Standard curve equations of four TISAB were established to clarify the influence of TISAB kinds. And the trace serum samples (rats and calf) were diluted to 1 times by TISAB, and then levels of fluoride in the samples that added by the standard sodium fluoride were detected, subsequently the influence of TISAB kinds on recovery rate were analyzed. Finally, the optimal ratio among serum sample and each TISAB in different serum was determined according to the recovery rate of the serum sample with different volume ratio. The standard curve of TISAB III sample exhibited best fitting effect (R2 = 0.9926 ), and it also showed the overwhelming superiority with the scope of recovery rates ranged from 90% to 105% in the rat serum standard addition recovery experiments. As calf serum, TISAB IV (recommended by health industry standard) performed superior than others with the scope of recovery rate ranged from 90% to 110% in standard addition recovery experiment. When the volume ratio changed, every kinds of TISAB had an optimal proportion with good recovery rate, only TISAB III with the proportion as 1: 1, nevertheless, those change little affected on the recovery rate in calf serum. The method recommended by health industry standard is only suitable for detecting the trace amounts of fluoride in the serum sample as calf, but not the serum sample as rats.

  19. Evaluation of new mixed-mode UHPLC stationary phases and the importance of stationary phase choice when using low ionic-strength mobile phase additives.

    Science.gov (United States)

    Nováková, Lucie; Vlčková, Hana; Petr, Solich

    2012-05-15

    In this study, the selectivity, retention properties, peak shape and loading capacity for bases were practically evaluated using two UHPLC mixed-mode hybrid CSH stationary phases modified by C18 or Phenyl group. The data were compared with the data obtained on other UHPLC hybrid stationary phases (BEH C18, BEH C8, BEH Phenyl and BEH Shield RP18) at both basic and acidic conditions using conventional HPLC buffers (50mM ammonium formate/acetate) as well as low ionic-strength additives such as, e.g. 0.1-0.01% formic/acetic acid and 1mM solution of ammonium formate/acetate, which are widely used in LC-MS applications. Ten pharmaceutically important compounds encompassing acids, bases and neutral were included into the study. Due to properties of CSH sorbent (which possess positively charged surface besides RP group), much improved peak shapes and weaker retention was obtained for bases even at very low concentration of acidic additives. Such conditions are ideally suited for LC-MS analysis of bases, where typical RP chromatographic separation (retention and good selectivity at basic pH) and LS-MS conditions (efficient ionization at acidic pH) are not in agreement. On the other hand, acids were more strongly retained and for some compounds the peak shape was influenced negatively due to ion-exchange mechanism. Further, the behavior of acidic, basic and neutral solutes is discussed using various additives at both basic and acidic pH for all above stated columns. The robustness of retention times after pH change from basic to acidic was also evaluated. The new CSH stationary phases represent an interesting selectivity tool preferably for separation of basic compounds. Copyright © 2012 Elsevier B.V. All rights reserved.

  20. Influence of pH and ionic strength on electrostatic properties of ferredoxin, FNR, and hydrogenase and the rate constants of their interaction

    Science.gov (United States)

    Diakonova, A. N.; Khrushchev, S. S.; Kovalenko, I. B.; Riznichenko, G. Yu; Rubin, A. B.

    2016-10-01

    Ferredoxin (Fd) protein transfers electrons from photosystem I (PSI) to ferredoxin:NADP+-reductase (FNR) in the photosynthetic electron transport chain, as well as other metabolic pathways. In some photosynthetic organisms including cyanobacteria and green unicellular algae under anaerobic conditions Fd transfers electrons not only to FNR but also to hydrogenase—an enzyme which catalyzes reduction of atomic hydrogen to H2. One of the questions posed by this competitive relationship between proteins is which characteristics of thylakoid stroma media allow switching of the electron flow between the linear path PSI-Fd-FNR-NADP+ and the path PSI-Fd-hydrogenase-H2. The study was conducted using direct multiparticle simulation approach. In this method protein molecules are considered as individual objects that experience Brownian motion and electrostatic interaction with the surrounding media and each other. Using the model we studied the effects of pH and ionic strength (I) upon complex formation between ferredoxin and FNR and ferredoxin and hydrogenase. We showed that the rate constant of Fd-FNR complex formation is constant in a wide range of physiologically significant pH values. Therefore it can be argued that regulation of FNR activity doesn’t involve pH changes in stroma. On the other hand, in the model rate constant of Fd-hydrogenase interaction dramatically depends upon pH: in the range 7-9 it increases threefold. It may seem that because hydrogenase reduces protons it should be more active when pH is acidic. Apparently, regulation of hydrogenase’s affinity to both her reaction partners (H+ and Fd) is carried out by changes in its electrostatic properties. In the dark, the protein is inactive and in the light it is activated and starts to interact with both Fd and H+. Therefore, we can conclude that in chloroplasts the rate of hydrogen production is regulated by pH through the changes in the affinity between hydrogenase and ferredoxin.

  1. Charge heterogeneity profiling of monoclonal antibodies using low ionic strength ion-exchange chromatography and well-controlled pH gradients on monolithic columns.

    Science.gov (United States)

    Talebi, Mohammad; Nordborg, Anna; Gaspar, Andras; Lacher, Nathan A; Wang, Qian; He, Xiaoping Z; Haddad, Paul R; Hilder, Emily F

    2013-11-22

    In this work, the suitability of employing shallow pH gradients generated using single component buffer systems as eluents through cation-exchange (CEX) monolithic columns is demonstrated for the high-resolution separation of monoclonal antibody (mAb) charge variants in three different biopharmaceuticals. A useful selection of small molecule buffer species is described that can be used within very narrow pH ranges (typically 1 pH unit) defined by their buffer capacity for producing controlled and smooth pH profiles when used together with porous polymer monoliths. Using very low ionic strength eluents also enabled direct coupling with electrospray ionisation mass spectrometry. The results obtained by the developed pH gradient approach for the separation of closely related antibody species appear to be consistent with those obtained by imaged capillary isoelectric focusing (iCE) in terms of both resolution and separation profile. Both determinants of resolution, i.e., peak compression and peak separation contribute to the gains in resolution, evidently through the Donnan potential effect, which is increased by decreasing the eluent concentration, and also through the way electrostatic charges are distributed on the protein surface. Retention mechanisms based on the trends observed in retention of proteins at pH values higher than the electrophoretic pI are also discussed using applicable theories. Employing monolithic ion-exchangers is shown to enable fast method development, short analysis time, and high sample throughput owing to the accelerated mass transport of the monolithic media. The possibility of short analysis time, typically less than 15 min, and high sample throughput is extremely useful in the assessment of charge-based changes to the mAb products, such as during manufacturing or storage. Copyright © 2013 Elsevier B.V. All rights reserved.

  2. The influence of agitation sequence and ionic strength on in vitro drug release from hypromellose (E4M and K4M) ER matrices--the use of the USP III apparatus.

    Science.gov (United States)

    Asare-Addo, Kofi; Kaialy, Waseem; Levina, Marina; Rajabi-Siahboomi, Ali; Ghori, Mohammed U; Supuk, Enes; Laity, Peter R; Conway, Barbara R; Nokhodchi, Ali

    2013-04-01

    Theophylline extended release (ER) matrices containing hypromellose (hydroxypropyl methylcellulose (HPMC) E4M and K4M were evaluated in media with a pH range of 1.2-7.5, using an automated USP type III, Bio-Dis dissolution apparatus. The objectives of this study were to evaluate the effects of systematic agitation, ionic strength and pH on the release of theophylline from the gel forming hydrophilic polymeric matrices with different methoxyl substitution levels. Tribo-electric charging of hypromellose, theophylline and their formulated blends containing E4M and K4M grades has been characterised, along with quantitative observations of flow, compression behaviour and particle morphology. Agitations were studied at 5, 10, 15, 20, 25, 30 dips per minute (dpm) and also in the ascending and descending order in the dissolution vials. The ionic concentration strength of the media was also varied over a range of 0-0.4M to simulate the gastrointestinal fed and fasted states and various physiological pH conditions. To study the effect of ionic strength on the hydrophilic matrices, agitation was set at 20 dpm. The charge results on individual components imply that the positively charged particles have coupled with the negatively charged particles to form a stable ordered mixture which is believed to result in a more homogeneous and stable system. The particle shape analysis showed the HPMC K4M polymer to have a more irregular morphology and a rougher surface texture in comparison to the HPMC E4M polymer, possibly a contributory factor to the gelation process. The results showed gelation occurred quicker for the K4M tablet matrices. Drug release increased with increased agitation. This was more pronounced for the E4M tablet matrices. The ionic strength also had more of an effect on the drug release from the E4M matrices. The experiments highlighted the resilience of the K4M matrices in comparison with the E4M matrices. The results thus show that despite similar viscosities of

  3. THE EFFECT OF ELECTROLYTE CONCENTRATION AND PH ON THE FLOCCULATION AND RHEOLOGICAL BEHAVIOUR OF KAOLINITE SUSPENSIONS

    Directory of Open Access Journals (Sweden)

    M. S. NASSER

    2009-12-01

    Full Text Available The effects of the electrolyte concentration and pH on the settling behaviour, floc sizes and rheological behaviour of kaolinite suspensions were investigated. The results show that the settling behaviour of kaolinite changes with the ionic strength and pH of the suspension. In the acidic pH range, (pH 2 particles settle in flocculated form regardless of electrolyte concentration, however, in the basic pH range, the particles settle both, in dispersed form (at lower electrolyte concentrations and in flocculated form (at higher electrolyte concentrations. The Bingham yield stress and time-dependent behaviour for these flocculated and deflocculated suspensions was investigated. In this study, the fundamental of structural kinetic model (SKM was used to investigate the time-dependent viscosity behaviour of flocculated and deflocculated kaolinite suspensions. It was found that the kaolinite suspensions in the deflocculated form show viscosity time-independent behaviour with negligible Bingham yield stress. While, the flocculated suspensions show marked non-Newtonian time-dependent behaviour. This work has been very successful in establishing the link among particle-particle interactions, floc size, Bingham yield stress, breakdown rate constant, and extent of thixotropy.

  4. Influence of pH and media composition on suspension stability of silver, zinc oxide, and titanium dioxide nanoparticles and immobilization of Daphnia magna under guideline testing conditions

    DEFF Research Database (Denmark)

    Cupi, Denisa; Hartmann, Nanna B.; Baun, Anders

    2016-01-01

    the influence of key environmental parameters: pH (2-12) and ionic strength using M7, Soft EPA (S EPA) medium, and Very Soft EPA (VS EPA) medium; and observed the influence of these parameters on zeta potential, zeta average, and acute immobilization of Daphnia magna for three different ENPs. Despite being...... sterically stabilized, test suspensions of silver (Ag) ENPs formed large agglomerates in both VS EPA and M7 media; and toxicity was found to be higher in VS EPA medium due to increased dissolution. Low-agglomerate suspensions for zinc oxide (ZnO) could be obtained at pH 7 in VS EPA medium, but the increase...

  5. Dependence of purple membrane bump curvature on pH and ionic strength analyzed using atomic force microscopy combined with solvent exchange.

    Science.gov (United States)

    Yokoyama, Yasunori; Yamada, Kosuke; Higashi, Yosuke; Ozaki, Satoshi; Wang, Haorang; Koito, Naoki; Watanabe, Naoya; Sonoyama, Masashi; Mitaku, Shigeki

    2014-08-07

    Purple membrane (PM), which is a membrane patch formed by the self-assembly of the membrane protein bacteriorhodopsin (bR) with archaeal lipids, is a good subject for studying the mechanism for the supramolecular structural formation of membrane proteins. Several studies have suggested that PM is not simply planar but that it has a curvature. Atomic force microscopy (AFM) studies also indicate the presence of dome-like structures (bumps) on the cytoplasmic surface of PM. PM must have a curvature to form the bump structures; therefore, bump formations will be related to a mechanism for supramolecular structural formation via self-assembly. To elucidate the effect of an asymmetric distribution of charged residues between two aqueous domains on the bump curvature, AFM topography of identical PM sheets were examined with variation of the solvent ionic strength and pH using a newly constructed solvent circulation system. The radius and height distributions of the bumps on the identical PM sheets indicated a linear correlation. The bump curvature, which was simply estimated by the slope of the distribution, became smaller with increasing KCl concentration, which suggests that tension at the cytoplasmic surface caused by electrostatic repulsive force between negatively charged amino acid residues becomes weaker by the electrostatic shielding effect. AFM observations revealed that the bump curvature remained even at high KCl concentration where the Debye length is within a few Angstroms; therefore, the contribution of the intrinsic difference between the domain sizes of bR between two sides was confirmed. Interestingly, the bump curvature was significantly increased by the addition of CaCl2 and then decreased with a similar dependency to KCl at higher CaCl2 concentration. The effect of pH on the bump curvature was also examined, where the curvature increased and reached a maximum at pH 9, while it decreased above pH 10, at which point the two-dimensional crystalline

  6. Analysis of nanoparticle agglomeration in aqueous suspensions via constant-number Monte Carlo simulation.

    Science.gov (United States)

    Liu, Haoyang Haven; Surawanvijit, Sirikarn; Rallo, Robert; Orkoulas, Gerassimos; Cohen, Yoram

    2011-11-01

    A constant-number direct simulation Monte Carlo (DSMC) model was developed for the analysis of nanoparticle (NP) agglomeration in aqueous suspensions. The modeling approach, based on the "particles in a box" simulation method, considered both particle agglomeration and gravitational settling. Particle-particle agglomeration probability was determined based on the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory and considerations of the collision frequency as impacted by Brownian motion. Model predictions were in reasonable agreement with respect to the particle size distribution and average agglomerate size when compared with dynamic light scattering (DLS) measurements for aqueous TiO(2), CeO(2), and C(60) nanoparticle suspensions over a wide range of pH (3-10) and ionic strength (0.01-156 mM). Simulations also demonstrated, in quantitative agreement with DLS measurements, that nanoparticle agglomerate size increased both with ionic strength and as the solution pH approached the isoelectric point (IEP). The present work suggests that the DSMC modeling approach, along with future use of an extended DLVO theory, has the potential for becoming a practical environmental analysis tool for predicting the agglomeration behavior of aqueous nanoparticle suspensions.

  7. Stability of titania nanoparticles in soil suspensions and transport in saturated homogeneous soil columns.

    Science.gov (United States)

    Fang, Jing; Shan, Xiao-quan; Wen, Bei; Lin, Jin-ming; Owens, Gary

    2009-04-01

    The stability of TiO(2) nanoparticles in soil suspensions and their transport behavior through saturated homogeneous soil columns were studied. The results showed that TiO(2) could remain suspended in soil suspensions even after settling for 10 days. The suspended TiO(2) contents in soil suspensions after 24h were positively correlated with the dissolved organic carbon and clay content of the soils, but were negatively correlated with ionic strength, pH and zeta potential. In soils containing soil particles of relatively large diameters and lower solution ionic strengths, a significant portion of the TiO(2) (18.8-83.0%) readily passed through the soils columns, while TiO(2) was significantly retained by soils with higher clay contents and salinity. TiO(2) aggregate sizes in the column outflow significantly increased after passing through the soil columns. The estimated transport distances of TiO(2) in some soils ranged from 41.3 to 370 cm, indicating potential environmental risk of TiO(2) nanoparticles to deep soil layers.

  8. Pharmaceutical suspensions: relation between zeta potential, sedimentation volume and suspension stability.

    Science.gov (United States)

    Kayes, J B

    1977-04-01

    The effect of added surface-active agents of various ionic types on the sedimentation volume of drug suspensions of betamethasone, griseofulvin, nalidixic acid and thiabendazole has been investigated, and the results correlated with previously measured zeta potentials. Study of the zeta potential/sedimentation volumes versus concentration plots showed that apparently only coagulated, deflocculated or sterically stabilized systems were formed. In most cases the sterically stabilized systems were produced from mixtures of ionic/non-ionic surfactants. These are examples of controlled coagulation, although non-ionic surfactant alone conferred stability against caking. Secondary minimum flocculation was not apparent but this may have been due to the method of examination of suspensions. The work confirmed that the DLVO theory of colloid stability and its modification to include a steric term can be applied to coarse suspension systems.

  9. Lipid extraction from microalgae using a single ionic liquid

    Science.gov (United States)

    Salvo, Roberto Di; Reich, Alton; Dykes, Jr., H. Waite H.; Teixeira, Rodrigo

    2013-05-28

    A one-step process for the lysis of microalgae cell walls and separation of the cellular lipids for use in biofuel production by utilizing a hydrophilic ionic liquid, 1-butyl-3-methylimidazolium. The hydrophilic ionic liquid both lyses the microalgae cell walls and forms two immiscible layers, one of which consists of the lipid contents of the lysed cells. After mixture of the hydrophilic ionic liquid with a suspension of microalgae cells, gravity causes a hydrophobic lipid phase to move to a top phase where it is removed from the mixture and purified. The hydrophilic ionic liquid is recycled to lyse new microalgae suspensions.

  10. Different binding modes of Cu and Pb vs. Cd, Ni, and Zn with the trihydroxamate siderophore desferrioxamine B at seawater ionic strength

    Energy Technology Data Exchange (ETDEWEB)

    Schijf, Johan; Christenson, Emily A.; Potter, Kailee J.

    2015-07-01

    The solution speciation in seawater of divalent trace metals (Cd, Cu, Ni, Pb, Zn) is dominated by strong, ostensibly metal-specific organic ligands that may play important roles in microbial metal acquisition and/or detoxification processes. We compare the effective stabilities of these metal-organic complexes to the stabilities of their complexes with a model siderophore, desferrioxamine B (DFOB). While metal-DFOB complexation has been studied in various dilute but often moderately coordinating media, for the purpose of this investigation we measured the stability constants in a non-coordinating background electrolyte at seawater ionic strength (0.7 M NaClO4). Potentiometric titrations of single metals (M) were performed in the presence of ligand (L) at different M:L molar ratios, whereupon the stability constants of multiple complexes were simultaneously determined by non-linear regression of the titration curves with FITEQL, using the optimal binding mode for each metal. Cadmium, Ni, and Zn, like trivalent Fe, sequentially form a bi-, tetra-, and hexadentate complex with DFOB as pH increases, consistent with their coordination number of 6 and regular octahedral geometry. Copper has a Jahn-Teller-distorted square-bipyramidal geometry whereas the geometry of Pb is cryptic, involving a range of bond lengths. Supported by a thermodynamic argument, our data suggest that this impedes binding of the third hydroxamate group and that the hexadentate Cu-DFOB and Pb-DFOB complex identified in earlier reports may instead be a deprotonated tetradentate complex. Absence of the hexadentate complex promotes the formation of a dinuclear (bidentate-tetradentate) complex, M2HL2+, albeit not for Pb in 0.7 M NaCl, evidently due to extensive complexation with chloride. Stabilities of the hexadentate Ni-DFOB, Zn-DFOB, and the tetradentate Pb-DFOB complex are nearly equal, yet about 2 orders of magnitude higher and 4 orders of magnitude lower than those of the hexadentate Cd-DFOB and

  11. Specialist gelator for ionic liquids.

    Science.gov (United States)

    Hanabusa, Kenji; Fukui, Hiroaki; Suzuki, Masahiro; Shirai, Hirofusa

    2005-11-08

    Cyclo(l-beta-3,7-dimethyloctylasparaginyl-L-phenylalanyl) (1) and cyclo(L-beta-2-ethylhexylasparaginyl-L-phenylalanyl) (2), prepared from L-asparaginyl-L-phenylalanine methyl ester, have been found to be specialist gelators for ionic liquids. They can gel a wide variety of ionic liquids, including imizazolium, pyridinium, pyrazolidinium, piperidinium, morpholinium, and ammonium salts. The mean minimum gel concentrations (MGCs) necessary to make gels at 25 degrees C were determined for ionic liquids. The gel strength increased at a rate nearly proportional to the concentration of added gelator. The strength of the transparent gel of 1-butylpyridinium tetrafluoroborate ([C(4)py]BF(4)), prepared at a concentration of 60 g L(-1) (gelator 1/[C(4)py]BF(4)), was ca. 1500 g cm(-2). FT-IR spectroscopy indicated that a driving force for gelation was intermolecular hydrogen bonding between amides and that the phase transition from gel to liquid upon heating was brought about by the collapse of hydrogen bonding. The gels formed from ionic liquids were very thermally stable; no melting occurs up to 140 degrees C when the gels were prepared at a concentration of 70 g L(-1) (gelator/ionic liquid). The ionic conductivities of the gels were nearly the same as those of pure ionic liquids. The gelator had electrochemical stability and a wide electrochemical window. When the gels were prepared from ionic liquids containing propylene carbonate, the ionic conductivities of the resulting gels increased to levels rather higher than those of pure ionic liquids. The gelators also gelled ionic liquids containing supporting electrolytes.

  12. Effects of Temperature, Oxygen Level, Ionic Strength, and pH on the Reaction of Benzene with Hydroxyl Radicals at the Air-Water Interface in Comparison to the Bulk Aqueous Phase.

    Science.gov (United States)

    Heath, Aubrey A; Valsaraj, Kalliat T

    2015-08-06

    Atmospheric aerosols (e.g., fog droplets) are complex, multiphase mediums. Depending on location, time of day, and/or air mass source, there can be considerable variability within these droplets, relating to temperature, pH, and ionic strength. Due to the droplets' inherently small size, the reactions that occur within these droplets are determined by bulk aqueous phase and air-water interfacial conditions. In this study, the reaction of benzene and hydroxyl radicals is examined kinetically in a thin-film flow-tube reactor. By varying the aqueous volume (e.g., film thickness) along the length of the reactor, both bulk and interfacial reaction rates are measured from a single system. Temperature, pH, and ionic strength are varied to model conditions typical of fog events. Oxygen-poor conditions are measured to study oxygen's overall effect on the reaction pathway. Initial rate activation energies and the bulk aqueous phase and interfacial contributions to the overall rate constant are also obtained.

  13. Learning Ionic

    CERN Document Server

    Ravulavaru, Arvind

    2015-01-01

    This book is intended for those who want to learn how to build hybrid mobile applications using Ionic. It is also ideal for people who want to explore theming for Ionic apps. Prior knowledge of AngularJS is essential to complete this book successfully.

  14. Ionic Liquid Epoxy Resin Monomers

    Science.gov (United States)

    Paley, Mark S. (Inventor)

    2013-01-01

    Ionic liquid epoxide monomers capable of reacting with cross-linking agents to form polymers with high tensile and adhesive strengths. Ionic liquid epoxide monomers comprising at least one bis(glycidyl) N-substituted nitrogen heterocyclic cation are made from nitrogen heterocycles corresponding to the bis(glycidyl) N-substituted nitrogen heterocyclic cations by a method involving a non-nucleophilic anion, an alkali metal cation, epichlorohydrin, and a strong base.

  15. Ionic Channels in Thunderclouds

    Science.gov (United States)

    Losseva, T. V.; Fomenko, A. S.; Nemtchinov, I. V.

    2007-12-01

    We proceed to study the formation and propagation of ionic channels in thunderclouds in the framework of the model of the corona discharge wave propagation (Fomenko A.S., Losseva T.V., Nemtchinov I.V. The corona discharge waves in thunderclouds and formation of ionic channels // 2004 Fall Meeting. EOS Trans. AGU. 2004. V. 85. ¹ 47. Suppl. Abstract AE23A-0835.). In this model we proposed a hypothesis that the structure of a thundercloud becomes nonuniform due to corona discharge on the drops and ice particles and formation of ionic channels with higher conductivity than the surrounding air. When the onset strength of corona discharge becomes smaller than the electric field strength the corona discharge increases concentrations of ions in a small part of the cloud (a hot spot). An additional charge at opposite ends of the hot spot forms due to polarization process. The increased electric field initiates corona discharge in other parts of the cloud on ice particles and water drops with smaller sizes. The corona discharge front moves as a wave with the velocity of the order of ion drift and formes a highly conductive channel. We model this non-stationary problem with Poisson equation which is solved simultaneously with a simplified set of kinetic equations for ions, small charged particles and electrons (at high electric fields), including ionization due to electronic impact, attachment and formation of positive ions. By applying 3D numerical simulations we obtain the parameters of formed ionic channels with respect to onset electric fields both from large particles (in hot spot) and from small particles (surrounding hot spot), microscopic currents from particles with different sizes and the external electric field in the cloud. The interaction of ionic channels is also investigated. This work was supported by Russian Foundation of Basic Research (Project No 07-05-00998-à).

  16. Independent suspension

    National Research Council Canada - National Science Library

    Chaikin, Don

    1992-01-01

    ... independent suspension. INDEPENDENCE! An independent system is simply one in which each of the vehicle's wheels is free to react totally separate from any of the other wheels. If the right rear wheel hits a bump, the left rear wheel is undisturbed. Since the whole car does not bounce and shake every time one of the wheels hits a potho...

  17. EDITORIAL: Colloidal suspensions Colloidal suspensions

    Science.gov (United States)

    Petukhov, Andrei; Kegel, Willem; van Duijneveldt, Jeroen

    2011-05-01

    Special issue in honour of Henk Lekkerkerker's 65th birthday Professor Henk N W Lekkerkerker is a world-leading authority in the field of experimental and theoretical soft condensed matter. On the occasion of his 65th birthday in the summer of 2011, this special issue celebrates his many contributions to science. Henk Lekkerkerker obtained his undergraduate degree in chemistry at the University of Utrecht (1968) and moved to Calgary where he received his PhD in 1971. He moved to Brussels as a NATO fellow at the Université Libre de Bruxelles and was appointed to an assistant professorship (1974), an associate professorship (1977) and a full professorship (1980) in physical chemistry at the Vrije Universiteit Brussel. In 1985 he returned to The Netherlands to take up a professorship at the Van 't Hoff Laboratory, where he has been ever since. He has received a series of awards during his career, including the Onsager Medal (1999) of the University of Trondheim, the Bakhuys Roozeboom Gold Medal (2003) of the Royal Dutch Academy of Arts and Sciences (KNAW), the ECIS-Rhodia European Colloid and Interface Prize (2003), and the Liquid Matter Prize of the European Physical Society (2008). He was elected a member of KNAW in 1996, was awarded an Academy Chair position in 2005, and has held several visiting lectureships. Henk's work focuses on phase transitions in soft condensed matter, and he has made seminal contributions to both the theoretical and experimental aspects of this field. Here we highlight three major themes running through his work, and a few selected publications. So-called depletion interactions may lead to phase separation in colloid-polymer mixtures, and Henk realised that the partitioning of polymer needs to be taken into account to describe the phase behaviour correctly [1]. Colloidal suspensions can be used as model fluids, with the time- and length-scales involved leading to novel opportunities, notably the direct observation of capillary waves at a

  18. Influence of pH, soil humic/fulvic acid, ionic strength and foreign ions on sorption of thorium(IV) onto {gamma}-Al{sub 2}O{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Chen, C.L. [Institute of Plasma Physics, Chinese Academy of Sciences, P.O. Box 1126, Hefei, Anhui 230031 (China); Wang, X.K. [Institute of Plasma Physics, Chinese Academy of Sciences, P.O. Box 1126, Hefei, Anhui 230031 (China)]. E-mail: xkwang@ipp.ac.cn

    2007-02-15

    The sorption of Th(IV) onto {gamma}-Al{sub 2}O{sub 3} in the absence and presence of soil humic acid (HA)/fulvic acid (FA) was studied by batch technique. The influence of pH from 2 to 12, ionic strength from 0.01M to 0.1M KNO{sub 3}, soil HA/FA concentrations from 2.5mg/L to 17.5mg/L, and foreign cations (Li{sup +}, Na{sup +}, K{sup +}) and anions (NO{sub 3}{sup -}, Cl{sup -}) on the sorption of Th(IV) onto {gamma}-Al{sub 2}O{sub 3} was also tested. The sorption isotherms of Th(IV) were determined at pH 3.50 (+/-0.02) and analyzed with the linear, Freundlich, and Langmuir sorption models, respectively. The results demonstrated that the sorption of Th(IV) onto {gamma}-Al{sub 2}O{sub 3} increases steeply with increasing pH from 2 to 4. HA/FA was shown to enhance Th(IV) sorption at low pH, but to reduce Th(IV) sorption at high pH. It was assumed that the significantly positive influence of HA/FA on Th(IV) sorption onto {gamma}-Al{sub 2}O{sub 3} at pH 2-4 is attributable to the strong surface binding of HA/FA on {gamma}-Al{sub 2}O{sub 3} and subsequently to the formation of ternary surface complexes such as ?SO-O-HA-Th or ?SO-O-FA-Th. The results also demonstrated that the sorption is strongly dependent on the concentration of HA/FA, and slightly dependent on ionic strength. The sorption of Th(IV) onto {gamma}-Al{sub 2}O{sub 3} was also dependent on foreign ions in solution under the experimental conditions.

  19. Long range electrostatic forces in ionic liquids.

    Science.gov (United States)

    Gebbie, Matthew A; Smith, Alexander M; Dobbs, Howard A; Lee, Alpha A; Warr, Gregory G; Banquy, Xavier; Valtiner, Markus; Rutland, Mark W; Israelachvili, Jacob N; Perkin, Susan; Atkin, Rob

    2017-01-19

    Ionic liquids are pure salts that are liquid under ambient conditions. As liquids composed solely of ions, the scientific consensus has been that ionic liquids have exceedingly high ionic strengths and thus very short Debye screening lengths. However, several recent experiments from laboratories around the world have reported data for the approach of two surfaces separated by ionic liquids which revealed remarkable long range forces that appear to be electrostatic in origin. Evidence has accumulated demonstrating long range surface forces for several different combinations of ionic liquids and electrically charged surfaces, as well as for concentrated mixtures of inorganic salts in solvent. The original interpretation of these forces, that ionic liquids could be envisioned as "dilute electrolytes," was controversial, and the origin of long range forces in ionic liquids remains the subject of discussion. Here we seek to collate and examine the evidence for long range surface forces in ionic liquids, identify key outstanding questions, and explore possible mechanisms underlying the origin of these long range forces. Long range surface forces in ionic liquids and other highly concentrated electrolytes hold diverse implications from designing ionic liquids for energy storage applications to rationalizing electrostatic correlations in biological self-assembly.

  20. Influence of pH and media composition on suspension stability of silver, zinc oxide, and titanium dioxide nanoparticles and immobilization of Daphnia magna under guideline testing conditions.

    Science.gov (United States)

    Cupi, Denisa; Hartmann, Nanna B; Baun, Anders

    2016-05-01

    In aquatic toxicity testing of engineered nanoparticles (ENPs) the process of agglomeration is very important as it may alter bioavailability and toxicity. In the present study, we aimed to identify test conditions that are favorable for maintaining stable ENP suspensions. We evaluated the influence of key environmental parameters: pH (2-12) and ionic strength using M7, Soft EPA (S EPA) medium, and Very Soft EPA (VS EPA) medium; and observed the influence of these parameters on zeta potential, zeta average, and acute immobilization of Daphnia magna for three different ENPs. Despite being sterically stabilized, test suspensions of silver (Ag) ENPs formed large agglomerates in both VS EPA and M7 media; and toxicity was found to be higher in VS EPA medium due to increased dissolution. Low-agglomerate suspensions for zinc oxide (ZnO) could be obtained at pH 7 in VS EPA medium, but the increase in dissolution caused higher toxicity than in M7 medium. Titanium dioxide (TiO2) ENPs had a point of zero charge in the range of pH 7-8. At pH 7 in VS EPA, agglomerates with smaller hydrodynamic diameters (~200nm) were present compared to the high ionic strength M7 medium where hydrodynamic diameters reached micrometer range. The stable suspensions of TiO2 ENPs caused immobilization of D. magna, 48-h EC50 value of 13.7mgL(-1) (95% CI, 2.4mg-79.1mgL(-1)); whereas no toxicity was seen in the unstable, highly agglomerated M7 medium suspensions, 48-h EC50 >100mgL(-1). The current study provides a preliminary approach for methodology in testing and assessing stability and toxicity of ENPs in aquatic toxicity tests of regulatory relevance. Copyright © 2016 Elsevier Inc. All rights reserved.

  1. The effects of ionic strength and organic matter on virus inactivation at low temperatures: general likelihood uncertainty estimation (GLUE) as an alternative to least-squares parameter optimization for the fitting of virus inactivation models

    Science.gov (United States)

    Mayotte, Jean-Marc; Grabs, Thomas; Sutliff-Johansson, Stacy; Bishop, Kevin

    2017-06-01

    This study examined how the inactivation of bacteriophage MS2 in water was affected by ionic strength (IS) and dissolved organic carbon (DOC) using static batch inactivation experiments at 4 °C conducted over a period of 2 months. Experimental conditions were characteristic of an operational managed aquifer recharge (MAR) scheme in Uppsala, Sweden. Experimental data were fit with constant and time-dependent inactivation models using two methods: (1) traditional linear and nonlinear least-squares techniques; and (2) a Monte-Carlo based parameter estimation technique called generalized likelihood uncertainty estimation (GLUE). The least-squares and GLUE methodologies gave very similar estimates of the model parameters and their uncertainty. This demonstrates that GLUE can be used as a viable alternative to traditional least-squares parameter estimation techniques for fitting of virus inactivation models. Results showed a slight increase in constant inactivation rates following an increase in the DOC concentrations, suggesting that the presence of organic carbon enhanced the inactivation of MS2. The experiment with a high IS and a low DOC was the only experiment which showed that MS2 inactivation may have been time-dependent. However, results from the GLUE methodology indicated that models of constant inactivation were able to describe all of the experiments. This suggested that inactivation time-series longer than 2 months were needed in order to provide concrete conclusions regarding the time-dependency of MS2 inactivation at 4 °C under these experimental conditions.

  2. Comparative study on sorption/desorption of radioeuropium on alumina, bentonite and red earth: effects of pH, ionic strength, fulvic acid, and iron oxides in red earth

    Energy Technology Data Exchange (ETDEWEB)

    Dong Wenming E-mail: dongwm@lzu.edu.cn; Wang Xiangke; Bian Xiaoyan; Wang Aixia; Du Jingzhou; Tao, Z.Y

    2001-02-01

    The sorption and desorption of Eu(III) as a representative of trivalent lanthanides and actinides on bentonite, alumina, red earth and red earth treated to remove free iron oxides were comparatively investigated by using batch technique and radiotracer {sup 152+154}Eu. The effects of pH, ionic strength, fulvic acid, iron oxides in red earth and the sorption mechanism were also discussed. As compared to alumina and red earth, Eu(III) presents a considerable distribution coefficient (K{sub d}) onto bentonite. It was found that the pH and the presence of clay minerals are the main factors dominating the sorption/desorption characteristic of Eu{sup 3+} in the soil, and that a sorption-desorption hysteresis on bentonite and red earth actually occurs. Furthermore, the main sorption mechanism of lanthanides onto bentonite, alumina and red earth is the formation of bridged hydroxo complexes with the surface, and there are negative effects of fulvic acid and free iron oxides in red earth on the sorption of Eu(III). The results of this paper indicate that the additivity rule on the sorption characteristic of a soil from the individual component's characteristics is not general.

  3. Solution ionic strength engineering as a generic strategy to coat graphene oxide (GO) on various functional particles and its application in high-performance lithium-sulfur (Li-S) batteries.

    Science.gov (United States)

    Rong, Jiepeng; Ge, Mingyuan; Fang, Xin; Zhou, Chongwu

    2014-02-12

    A generic and facile method of coating graphene oxide (GO) on particles is reported, with sulfur/GO core-shell particles demonstrated as an example for lithium-sulfur (Li-S) battery application with superior performance. Particles of different diameters (ranging from 100 nm to 10 μm), geometries, and compositions (sulfur, silicon, and carbon) are successfully wrapped up by GO, by engineering the ionic strength in solutions. Importantly, our method does not involve any chemical reaction between GO and the wrapped particles, and therefore, it can be extended to vast kinds of functional particles. The applications of sulfur/GO core-shell particles as Li-S battery cathode materials are further investigated, and the results show that sulfur/GO exhibit significant improvements over bare sulfur particles without coating. Galvanic charge-discharge test using GO/sulfur particles shows a specific capacity of 800 mAh/g is retained after 1000 cycles at 1 A/g current rate if only the mass of sulfur is taken into calculation, and 400 mAh/g if the total mass of sulfur/GO is considered. Most importantly, the capacity decay over 1000 cycles is less than 0.02% per cycle. The coating method developed in this study is facile, robust, and versatile and is expected to have wide range of applications in improving the properties of particle materials.

  4. Impact of lysozyme on stability mechanism of nanozirconia aqueous suspension

    Energy Technology Data Exchange (ETDEWEB)

    Szewczuk-Karpisz, Katarzyna, E-mail: k.szewczuk-karpisz@wp.pl; Wiśniewska, Małgorzata

    2016-08-30

    Highlights: • Adsorption and stabilization-destabilization properties of lysozyme (LSZ) in the nanozirconia-biopolymer solution system were determined. • The stability measurements were performed using turbidimetric method. • Lysozyme macromolecules undergo adsorption on the ZrO{sub 2} surface under electrostatic adsorbent-adsorbate attraction, i.e. at pH 6 and 9. • The biopolymer adsorption impact on the zirconia stability varies at different pH values. - Abstract: The effect of lysozyme (LSZ) presence on the zirconium(IV) oxide (ZrO{sub 2}) aqueous suspension stability was examined. The applied zirconia contains mesopores (with a diameter about 30 nm) and its mean particle size is about 100 nm. To determine the stability mechanism of ZrO{sub 2} suspension in the biopolymer presence, the adsorption and electrokinetic (surface charge density and zeta potential) measurements were performed in the pH range 3–10. The lysozyme adsorption on the nanozirconia surface proceeds mainly through electrostatic forces. Under solid-polymer repulsion conditions, there is no adsorption of lysozyme (pH < 6, C{sub NaCl} 0.01 mol/dm{sup 3}). The increase of solution ionic strength to 0.2 mol/dm{sup 3} causes screening of unfavourable forces and biopolymer adsorption becomes possible. The LSZ addition to the ZrO{sub 2} suspension influences its stability. At pH 3, 4.6 and 7.6, slight improvement of the system stability was obtained. In turn, at pH 9 considerable destabilization of nanozirconia particles covered by polymeric layers occurs.

  5. Formation of nitrous oxide (N2O) hydrate in soil mineral suspensions with electrolytes

    Science.gov (United States)

    Kyung, D.; Enkh-Amgalan, T.; Lee, W.

    2013-05-01

    We have identified the effects of solid surface (illite, nontronite, sphalerite, kaolinite) and electrolyte (NaCl, KCl, CaCl2, MgCl2) types on the formation of N2O hydrate in this study. The hydrate formation experiments were conducted at hydrate forming condition (273.3K and 30 bar) by injecting N2O gas into the soil mineral suspensions with and without electrolytes in a 50mL pressurized vessel. The formation of N2O hydrate in aqueous electrolyte solutions was slower than that in deionized water. Ion charge and size were significant factors affecting N2O hydrate formation kinetic in electrolytes solutions. The addition of soil mineral suspensions accelerated the formation of N2O hydrate in the electrolyte solutions. Surface area and ionic strength of soil minerals highly influenced on formation kinetic of N2O hydrate. The hydrate formation times in the solid suspensions without electrolytes were very similar to that in the deionized water. The results obtained from this research could be indirectly applied to the fate of N2O sequestered into geological formations as well as its storage as a form of N2O hydrate.

  6. Robust Tensioned Kevlar Suspension Design

    Science.gov (United States)

    Young, Joseph B.; Naylor, Bret J.; Holmes, Warren A.

    2012-01-01

    One common but challenging problem in cryogenic engineering is to produce a mount that has excellent thermal isolation but is also rigid. Such mounts can be achieved by suspending the load from a network of fibers or strings held in tension. Kevlar fibers are often used for this purpose owing to their high strength and low thermal conductivity. A suite of compact design elements has been developed to improve the reliability of suspension systems made of Kevlar.

  7. A comparison between two pneumatic suspension architectures

    OpenAIRE

    Scopesi, Marco; Franco, Walter; Quaglia, Giuseppe

    2012-01-01

    The aim of this work is to assess and compare the mathematical models of two pneumatic suspension architectures and show how they can converge, after appropriate simplifications, to a general linear form. After making this model dimensionless, it will be used to study, with a transmissibility analysis, the behaviour of a mono-suspension (quarter-car model). Finally, an example of a design process will be shown to highlight the strengths and weaknesses of both architectures and to provide the ...

  8. Restructuring and aging in a capillary suspension.

    Science.gov (United States)

    Koos, Erin; Kannowade, Wolfgang; Willenbacher, Norbert

    2014-12-01

    The rheological properties of capillary suspensions, suspensions with small amounts of an added immiscible fluid, are dramatically altered with the addition of the secondary fluid. We investigate a capillary suspension to determine how the network ages and restructures at rest and under applied external shear deformation. The present work uses calcium carbonate suspended in silicone oil (11 % solids) with added water as a model system. Aging of capillary suspensions and their response to applied oscillatory shear is distinctly different from particulate gels dominated by the van der Waals forces. The suspensions dominated by the capillary force are very sensitive to oscillatory flow, with the linear viscoelastic regime ending at a deformation of only 0.1% and demonstrating power-law aging behavior. This aging persists for long times at low deformations or for shorter times with a sudden decrease in the strength at higher deformations. This aging behavior suggests that the network is able to rearrange and even rupture. This same sensitivity is not demonstrated in shear flow where very high shear rates are required to rupture the agglomerates returning the apparent viscosity of capillary suspensions to the same viscosity as for the pure vdW suspension. A transitional region is also present at intermediate water contents wherein the material response depends very strongly on the type, strength, and duration of the external forcing.

  9. Thermal probes of nanoparticle interfaces: Thermodiffusion and thermal conductivity of nanoparticle suspensions

    Science.gov (United States)

    Putnam, Shawn Arthur

    This dissertation presents an experimental study of heat transport and mass transport in nanoparticle composites. The 3o-method was used for high precision thermal conductivity measurements of PMMA polymers filled with alumina nanoparticles. A microfluidic beam deflection technique, developed in this thesis, was used to measure both the thermal conductivity (Λ) and the thermodiffusion coefficient (DT) of nanoparticle suspensions. Thermal conductivity studies of polymer nanocomposites used effective medium theory and data for the changes in thermal conductivity to estimate the thermal conductance of PMMA/alumina interfaces in the temperature range of 40 30 nm. Thermal conductivity studies of nanoparticle suspensions measured the thermal diffusivity to a precision better than 1%. Solutions of G60--C 70 fullerenes and alkanethiolate-protected Au nanoparticles were measured to maximum volume fractions of 0.6% and 0.35 vol%, respectively. Anomalous enhancements in Λ were not observed. The largest enhancement in Λ was 1.3 +/- 0.8% for 4 nm diameter Au particles suspended in ethanol. Thermodiffusion studies investigated aqueous suspensions of charged polystyrene nanoparticles, proteins of T4 lysozyme, and mutant variants of T4 lysozyme at small particle concentrations (cp ≈ 1-2 vol%). DT was measured as a function of temperature, particle size, particle charge, ionic strength, and ionic species. At room temperature and high salt concentrations (>100 mM), DT for 26 nm polystyrene nanoparticles varied systematically within the range --0.9x10-7 cm2 K -1 50°C, the thermodiffusion coefficients were positive with a value consistent with the predictions of a theoretical model originally proposed by B. Derjaguin that is based on the enthalpy changes due to polarization of water molecules in the double-layer. At high temperatures, DT was also independent of particle size.

  10. Bile salt-fatty acid mixed micelles as nasal absorption promoters of peptides. I. Effects of ionic strength, adjuvant composition, and lipid structure on the nasal absorption of [D-Arg2]kyotorphin.

    Science.gov (United States)

    Tengamnuay, P; Mitra, A K

    1990-02-01

    Bile salts and synthetic surfactants have been used to promote nasal absorption of peptide drugs. Although a marked increase in nasal absorption has been achieved, this may not be adequate and the possibility of adjuvant-induced membrane toxicity exists. The present study employs a rat in situ nasal perfusion technique and mixed micelles between sodium glycocholate (NaGC) and various lipids as potential nasal absorption enhancers of a stable model dipeptide, [D-Arg2]kyotorphin. NaGC alone enhanced the nasal absorption of the dipeptide in a concentration-dependent manner. When linoleic acid was added to form mixed micelles with NaGC, the absorption was further enhanced (P less than 0.01). The effect of mixed micelles was synergistic and much greater than with single adjuvants. Increasing ionic strength was found to increase the adjuvant activity of both NaGC and NaGC-lipid mixed micelles. Structure of the lipid component of the mixed micelles also affected the adjuvant potency. Oleic acid, a cis-unsaturated fatty acid, was more effective than elaidic acid, the trans-isomer, whereas cis-linoleic acid and trans-linolelaidic acid were equally effective (alpha = 0.05). Mixed micelles of mono-glycerides such as monoolein and monolinolein were also more effective than NaGC alone (alpha = 0.05). Micellar solubilization of these polar lipids by NaGC appears to be important for nasal absorption enhancement to occur. Reversal of the membrane permeability was also observed within approximately 20-40 min after removal of the adjuvants from the rat nasal cavity. These observations are similar to the effects of mixed micelles on the rectal mucosa and may involve the same mechanism.

  11. Thermotropic Ionic Liquid Crystals

    OpenAIRE

    Sabine Laschat; Axenov, Kirill V

    2011-01-01

    The last five years’ achievements in the synthesis and investigation of thermotropic ionic liquid crystals are reviewed. The present review describes the mesomorphic properties displayed by organic, as well as metal-containing ionic mesogens. In addition, a short overview on the ionic polymer and self-assembled liquid crystals is given. Potential and actual applications of ionic mesogens are also discussed.

  12. Facile and highly efficient removal of trace Gd(III) by adsorption of colloidal graphene oxide suspensions sealed in dialysis bag

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Weifan, E-mail: dragon0791@sohu.com [School of Materials Science and Engineering, Nanchang University, Nanchang 330031 (China); Research Center of Rare Earths and Micro/Nano Functional Materials, Nanchang University, Nanchang 330031 (China); Wang, Linlin; Zhuo, Mingpeng; Liu, Yue; Wang, Yiping [School of Materials Science and Engineering, Nanchang University, Nanchang 330031 (China); Li, Yongxiu [Research Center of Rare Earths and Micro/Nano Functional Materials, Nanchang University, Nanchang 330031 (China)

    2014-08-30

    Graphical abstract: Schematic diagram of Gd(III) adsorption and desorption on GO nanosheets in colloidal suspensions sealed by dialysis membrane. - Highlights: • Loading GO suspensions into dialysis bag for sorption of Gd(III) avoids re-pollution. • GO shows higher adsorption capacity for Gd(III) than any other currently reported. • Effects of pH, ionic strength and temperature on GO sorption for Gd(III) were studied. • Gd(III)-saturated GO has high desorption rate in nitric acid aqueous solution. • The thermodynamics and kinetics models of Gd(III) sorption on GO were studied. - Abstract: A facile, highly efficient and second-pollution-free strategy to remove trace Gd(III) from aqueous solutions by adsorption of colloidal graphene oxide (GO) suspensions in dialysis bag has been developed. The effects of pH, ionic strength and temperature on Gd(III) adsorption, and the pH-dependent desorption were investigated. The maximum adsorption capacity of Gd(III)on GO at pH = 5.9 ± 0.1 and T = 303 K was 286.86 mg g{sup −1}, higher than any other currently reported. The Gd(III)-saturated GO suspension could resume colloidal state in 0.1 M HNO{sub 3} with desorption rate of 85.00% in the fifth adsorption–desorption cycle. Gd(III) adsorption rate on GO was dependent more on pH and ionic strength than on temperature. The abundant oxygen-containing functional groups such as carboxyl and hydroxyl played a vital role on adsorption. The thermodynamics and kinetics investigations revealed that the adsorption of Gd(III) on GO was an endothermic, spontaneous and monolayer absorption process, which well fitted the pseudo-second-order model. GO could be a promising adsorbent applied in the enrichment and removal of lanthanides from aqueous solutions. More significantly, the combination of colloidal GO suspension with dialysis membrane facilely solves the re-pollution of the treated solutions due to the great difficulties in separation and recovery of GO.

  13. Suspension as an Emergency Power

    National Research Council Canada - National Science Library

    Amanda L. Tyler

    2009-01-01

    ... Legislation B. Suspension During Reconstruction: Putting Down the Klan in South Carolina IV. UNDERSTANDING SUSPENSION AS AN EMERGENCY POWER A. Reading the Suspension Clause in Context B. Giving Meaning to the Suspension Power C. Mapping the Suspension Clause Within the Constitution V. SUSPENSION AND THE SEPARATION OF POWERS CONCLUSION [A] suspensio...

  14. Electrorheology of nanofiber suspensions

    National Research Council Canada - National Science Library

    Yin, Jianbo; Zhao, Xiaopeng

    2011-01-01

    .... In this review, we especially focus on the recent researches on electrorheology of various nanofiber-based suspensions, including inorganic, organic, and inorganic/organic composite nanofibers...

  15. A comparison between two pneumatic suspension architectures

    Science.gov (United States)

    Quaglia, G.; Scopesi, M.; Franco, W.

    2012-04-01

    The aim of this work is to assess and compare the mathematical models of two pneumatic suspension architectures and show how they can converge, after appropriate simplifications, to a general linear form. After making this model dimensionless, it will be used to study, with a transmissibility analysis, the behaviour of a mono-suspension (quarter-car model). Finally, an example of a design process will be shown to highlight the strengths and weaknesses of both architectures and to provide the reader with a practical design tool.

  16. Ionic Nanofluids in Tribology

    Directory of Open Access Journals (Sweden)

    Noelia Saurín

    2015-11-01

    Full Text Available This overview covers the most recent developments in the field of ionic nanofluid lubricants, defined as dispersions of nanoparticles with ionic liquids through the activation of nanophases. The nanophases range from metal nanoparticles and ceramic inorganic nanoparticles, to different carbon nanophases. The combinations with room-temperature ionic liquids can be in the form of mixtures, dispersions, surface-modified nanophases, or chemically-functionalized nanophases. The new ionic nanofluids can be used as base lubricants, as lubricant additives, or as anti-friction and wear-reducing additives in new nanocomposite materials.

  17. The effect of cations on the aggregation of commercial ZnO nanoparticle suspension

    Science.gov (United States)

    Liu, Wei-Szu; Peng, Yu-Huei; Shiung, Chia-En; Shih, Yang-hsin

    2012-12-01

    Nanoscale ZnO materials have been largely used in many products due to their distinct properties. However, ZnO nanoparticles (NPs) are hazardous to human health and the ecosystem. The characteristics and the stability of ZnO NPs are relevant to their fate in the environment and their potential toxicities. In this study, a stable commercial ZnO NP suspension was chosen to investigate its aggregation under various salt additions. Different concentrations of NaCl, KCl and CaCl2 were chosen to represent various environmental conditions. Under pH 8-9, the surface charge of commercial ZnO NPs was negative. The behavior of the stabilized ZnO NPs in water was affected by ionic combinations and ionic strength; that is, divalent cations were more effective than monovalent ones in promoting aggregation formation. The attachment efficiencies of ZnO aggregates were calculated based upon the aggregation kinetics. The critical coagulation concentration values for this commercial ZnO NPs were higher than previous reported for ZnO NPs, indicating this ZnO NP could be stable in the aquatic environment and might have increased hazardous potentials. Based upon the Derjaguin-Landau-Verwey-Overbeek theory, interactions between ZnO NPs in the presence of different ions were evaluated to illustrate the aggregation mechanism. Our results indicated that critical ionic type and concentration promote the aggregation of stable ZnO NPs. These understandings also can facilitate the design of the precipitation treatment to remove NPs from water.

  18. Suspension Trauma / Orthostatic Intolerance

    Science.gov (United States)

    ... Emphasis Programs Directives Severe Violators TOPICS By Sector Construction Health Care Agriculture Maritime Oil and Gas Federal ... such fatalities often are referred to as "harnessinduced pathology" or "suspension trauma." Signs & symptoms that may be ...

  19. Urinary incontinence - retropubic suspension

    Science.gov (United States)

    ... your doctor will have you try bladder retraining, Kegel exercises, medicines, or other options. If you tried ... retropubic colposuspension; Needle suspension; Burch colposuspension Patient Instructions Kegel exercises - self-care Self catheterization - female Suprapubic catheter ...

  20. Rheology of organoclay suspension

    CSIR Research Space (South Africa)

    Hato, MJ

    2011-05-01

    Full Text Available The authors have studied the rheological properties of clay suspensions in silicone oil, where clay surfaces were modified with three different types of surfactants. Dynamic oscillation measurements showed a plateau-like behavior for all...

  1. Nanoconfinement-enhanced conformational response of single DNA molecules to changes in ionic environment

    DEFF Research Database (Denmark)

    Reisner, Walter; Beech, J. P.; Larsen, Niels Bent

    2007-01-01

    We show that the ionic environment plays a critical role in determining the configurational properties of DNA confined in silica nanochannels. The extension of DNA in the nanochannels increases as the ionic strength is reduced, almost tripling over two decades in ionic strength for channels aroun....... To quantify the increase in self-avoidance, we introduce a new parameter into the de Gennes theory: an effective DNA width that gives the increase in the excluded volume due to electrostatic repulsion.......We show that the ionic environment plays a critical role in determining the configurational properties of DNA confined in silica nanochannels. The extension of DNA in the nanochannels increases as the ionic strength is reduced, almost tripling over two decades in ionic strength for channels around...... 100×100 nm in dimension. Surprisingly, we find that the variation of the persistence length alone with ionic strength is not enough to explain our results. The effect is due mainly to increasing self-avoidance created by the reduced screening of electrostatic interactions at low ionic strength...

  2. Articulated suspension system

    Science.gov (United States)

    Bickler, Donald B. (Inventor)

    1989-01-01

    The invention provides a rough terrain vehicle which maintains a substantially constant weight, and therefore traction, on all wheels, despite one wheel moving considerably higher or lower than the others, while avoiding a very soft spring suspension. The vehicle includes a chassis or body to be supported and a pair of side suspensions at either side of the body. In a six wheel vehicle, each side suspension includes a middle wheel, and front and rear linkages respectively coupling the front and rear wheels to the middle wheel. A body link pivotally connects the front and rear linkages together, with the middle of the body link rising or falling by only a fraction of the rise or fall of any of the three wheels. The body link pivotally supports the middle of the length of the body. A transverse suspension for suspending the end of the body on the side suspensions includes a middle part pivotally connected to the body about a longitudinal axis and opposite ends each pivotally connected to one of the side suspensions along at least a longitudinal axis.

  3. Coarsening mechanics of a colloidal suspension in toggled fields

    Science.gov (United States)

    Bauer, Jonathan L.; Liu, Yifei; Kurian, Martin J.; Swan, James W.; Furst, Eric M.

    2015-08-01

    Suspensions of paramagnetic colloids are driven to phase separate and self-assemble in toggled magnetic fields. At field strengths above 575 A/m and toggle frequencies between 0.66 and 2 Hz, an initial gel-like, arrested network collapses into condensed, ellipsoidal aggregates. The evolution to this equilibrium structure occurs via a Rayleigh-Plateau instability. The toggle frequency ν determines the fluidity of the breakup process. At frequencies between 0.66 and 1.5 Hz, the suspension breaks up similar to a viscous, Newtonian fluid. At frequencies ν > 1.5 Hz, the network ruptures like a viscoplastic material. The field strength alters the onset time of the instability. A power law relationship emerges as the scaled frequency and field strength can be used to predict the onset of breakup. These results further aid in understanding the mechanics and dynamics of the phase separation process of suspensions of polarizable colloids in toggled external fields.

  4. Peculiar charging effects on titania in aqueous 1:1, 2:1, 1:2 and mixed electrolyte suspensions.

    Science.gov (United States)

    Rosenholm, Jarl B; Kosmulski, Marek

    2012-11-01

    Charging of particles in aqueous suspensions is primarily related to potential determining ions, such as silver and iodide ions at silver halide particle surfaces. Proton is considered as a (secondary) potential determining ion at hydrated metal oxide surfaces. Indifferent electrolytes neutralize at increased concentration the surface charge but do not reverse it. However, in the presence of a non-Coulombic interaction the surface charge may be enhanced or reversed at increased ionic strength. Such interaction is denoted specific which may be due to enhanced van der Waals dipolar, Lewis acid-base, solvation (Hofmeister) and/or Born solvation effects. Alternatively, these interactions have been characterized in terms of (semi) empirical ion and surface properties, such as hard-soft acid-base (HSAB) interaction. Within the Stern layer closest to the particle surface truly specific effects are related to the inner Helmholtz plane (IHP) in order to distinguish them from the charge and solvation related effects occurring within the outer Helmholtz plane (OHP). We review some recent observations on the particular influence of ions on the charging of titania particles in aqueous 1:1, 2:1, 1:2 and mixed electrolyte suspensions. Copyright © 2012 Elsevier B.V. All rights reserved.

  5. Photophysics of ionic biochromophores

    CERN Document Server

    Brøndsted Nielsen, Steen

    2014-01-01

    This concise guide to studying ionic biochromophores features the first integrated overview of the photophysics of differing classes of biomolecules, from single amino acids to DNA. It includes an appraisal of the latest theories and experimental techniques.

  6. Ionic liquids in tribology.

    Science.gov (United States)

    Minami, Ichiro

    2009-06-24

    Current research on room-temperature ionic liquids as lubricants is described. Ionic liquids possess excellent properties such as non-volatility, non-flammability, and thermo-oxidative stability. The potential use of ionic liquids as lubricants was first proposed in 2001 and approximately 70 articles pertaining to fundamental research on ionic liquids have been published through May 2009. A large majority of the cations examined in this area are derived from 1,3-dialkylimidazolium, with a higher alkyl group on the imidazolium cation being beneficial for good lubrication, while it reduces the thermo-oxidative stability. Hydrophobic anions provide both good lubricity and significant thermo-oxidative stability. The anions decompose through a tribochemical reaction to generate metal fluoride on the rubbed surface. Additive technology to improve lubricity is also explained. An introduction to tribology as an interdisciplinary field of lubrication is also provided.

  7. Fullerol ionic fluids

    KAUST Repository

    Fernandes, Nikhil

    2010-01-01

    We report for the first time an ionic fluid based on hydroxylated fullerenes (fullerols). The ionic fluid was synthesized by neutralizing the fully protonated fullerol with an amine terminated polyethylene/polypropylene oxide oligomer (Jeffamine®). The ionic fluid was compared to a control synthesized by mixing the partially protonated form (sodium form) of the fullerols with the same oligomeric amine in the same ratio as in the ionic fluids (20 wt% fullerol). In the fullerol fluid the ionic bonding significantly perturbs the thermal transitions and melting/crystallization behavior of the amine. In contrast, both the normalized heat of fusion and crystallization of the amine in the control are similar to those of the neat amine consistent with a physical mixture of the fullerols/amine with minimal interactions. In addition to differences in thermal behavior, the fullerol ionic fluid exhibits a complex viscoelastic behavior intermediate between the neat Jeffamine® (liquid-like) and the control (solid-like). © 2010 The Royal Society of Chemistry.

  8. Electroneutrality and phase behavior of colloidal suspensions.

    Science.gov (United States)

    Denton, A R

    2007-11-01

    Several statistical mechanical theories predict that colloidal suspensions of highly charged macroions and monovalent microions can exhibit unusual thermodynamic phase behavior when strongly deionized. Density-functional, extended Debye-Hückel, and response theories, within mean-field and linearization approximations, predict a spinodal phase instability of charged colloids below a critical salt concentration. Poisson-Boltzmann cell model studies of suspensions in Donnan equilibrium with a salt reservoir demonstrate that effective interactions and osmotic pressures predicted by such theories can be sensitive to the choice of reference system, e.g., whether the microion density profiles are expanded about the average potential of the suspension or about the reservoir potential. By unifying Poisson-Boltzmann and response theories within a common perturbative framework, it is shown here that the choice of reference system is dictated by the constraint of global electroneutrality. On this basis, bulk suspensions are best modeled by density-dependent effective interactions derived from a closed reference system in which the counterions are confined to the same volume as the macroions. Lower-dimensional systems (e.g., monolayers, clusters), depending on the strength of macroion-counterion correlations, may be governed instead by density-independent effective interactions tied to an open reference system with counterions dispersed throughout the reservoir, possibly explaining the observed structural crossover in colloidal monolayers and anomalous metastability of colloidal crystallites.

  9. Are Ionic Liquids Chemically Stable?

    Science.gov (United States)

    Wang, Binshen; Qin, Li; Mu, Tiancheng; Xue, Zhimin; Gao, Guohua

    2017-05-24

    Ionic liquids have attracted a great deal of interest in recent years, illustrated by their applications in a variety of areas involved with chemistry, physics, biology, and engineering. Usually, the stabilities of ionic liquids are highlighted as one of their outstanding advantages. However, are ionic liquids really stable in all cases? This review covers the chemical stabilities of ionic liquids. It focuses on the reactivity of the most popular imidazolium ionic liquids at structural positions, including C2 position, N1 and N3 positions, and C4 and C5 positions, and decomposition on the imidazolium ring. Additionally, we discuss decomposition of quaternary ammonium and phosphonium ionic liquids and hydrolysis and nucleophilic reactions of anions of ionic liquids. The review aims to arouse caution on potential decomposition of ionic liquids and provides a guide for better utilization of ionic liquids.

  10. Ionic liquid based multifunctional double network gel

    Science.gov (United States)

    Ahmed, Kumkum; Higashihara, Tomoya; Arafune, Hiroyuki; Kamijo, Toshio; Morinaga, Takashi; Sato, Takaya; Furukawa, Hidemitsu

    2015-04-01

    Gels are a promising class of soft and wet materials with diverse application in tissue engineering and bio-medical purpose. In order to accelerate the development of gels, it is required to synthesize multi-functional gels of high mechanical strength, ultra low surface friction and suitable elastic modulus with a variety of methods and new materials. Among many types of gel ionic gel made from ionic liquids (ILs) could be used for diverse applications in electrochemical devices and in the field of tribology. IL, a promising materials for lubrication, is a salt with a melting point lower than 100 °C. As a lubricant, ILs are characterized by an extremely low vapor pressure, high thermal stability and high ion conductivity. In this work a novel approach of making double network DN ionic gel using IL has been made utilizing photo polymerization process. A hydrophobic monomer Methyl methacrylate (MMA) has been used as a first network and a hydrophobic IL monomer, N,N-diethyl-N-(2-mthacryloylethyl)-N-methylammonium bistrifluoromethylsulfonyl)imide (DEMM-TFSI) has been used as a second network using photo initiator benzophenon and crosslinker triethylene glycol dimethacrylate (TEGDMA). The resulting DN ionic gel shows transparency, flexibility, high thermal stability, good mechanical toughness and low friction coefficient value which can be a potential candidate as a gel slider in different mechanical devices and can open a new area in the field of gel tribology.

  11. Evaluation of new suspension system for limb prosthetics.

    Science.gov (United States)

    Gholizadeh, Hossein; Abu Osman, Noor Azuan; Eshraghi, Arezoo; Ali, Sadeeq; Arifin, Nooranida; Wan Abas, Wan Abu Bakar

    2014-01-10

    Good prosthetic suspension system secures the residual limb inside the prosthetic socket and enables easy donning and doffing. This study aimed to introduce, evaluate and compare a newly designed prosthetic suspension system (HOLO) with the current suspension systems (suction, pin/lock and magnetic systems). All the suspension systems were tested (tensile testing machine) in terms of the degree of the shear strength and the patient's comfort. Nine transtibial amputees participated in this study. The patients were asked to use four different suspension systems. Afterwards, each participant completed a questionnaire for each system to evaluate their comfort. Furthermore, the systems were compared in terms of the cost. The maximum tensile load that the new system could bear was 490 N (SD, 5.5) before the system failed. Pin/lock, magnetic and suction suspension systems could tolerate loads of 580 N (SD, 8.5), 350.9 (SD, 7) and 310 N (SD, 8.4), respectively. Our subjects were satisfied with the new hook and loop system, particularly in terms of easy donning and doffing. Furthermore, the new system is considerably cheaper (35 times) than the current locking systems in the market. The new suspension system could successfully retain the prosthesis on the residual limb as a good alternative for lower limb amputees. In addition, the new system addresses some problems of the existing systems and is more cost effective than its counterparts.

  12. Viscosity of colloidal suspensions

    Energy Technology Data Exchange (ETDEWEB)

    Cohen, E.G.D. [Rockefeller Univ., New York, NY (United States); Schepper, I.M. de [Delft Univ. of Technology (Netherlands)

    1995-12-31

    Simple expressions are given for the effective Newtonian viscosity as a function of concentration as well as for the effective visco-elastic response as a function of concentration and imposed frequency, of monodisperse neutral colloidal suspensions over the entire fluid range. The basic physical mechanisms underlying these formulae are discussed. The agreement with existing experiments is very good.

  13. Flywheel Magnetic Suspension Developments

    Science.gov (United States)

    Palazzolo, Alan; Kenny, Andrew; Sifford, Curtiss; Thomas, Erwin; Bhuiyan, Mohammad; Provenza, Andrew; Kascak, Albert; Montague, Gerald; Lei, Shuliang; Kim, Yeonkyu; hide

    2002-01-01

    The paper provides an overview of many areas of the flywheel magnetic suspension (MS) R&D being performed at the Texas A&M Vibration Control and Electromechanics Lab (TAMU-VCEL). This includes system response prediction, actuator optimization and redundancy, controller realizations and stages, sensor enhancements and backup bearing reliability.

  14. Cryonic Suspension and the Law.

    Science.gov (United States)

    Smith, George P.; Hall, Clare

    1987-01-01

    Analyzes three central problems which adversely affect use, development, and perfection of cryonic suspension of individuals: the extent to which a physician may be guilty of malpractice in assisting with a suspension; the need for a recognition of suspension; and the present effect of the law's anachronistic treatment of estate devolution upon a…

  15. Efeito da força iônica da solução de equilíbrio sobre a adsorção/dessorção de chumbo em Latossolos brasileiros Effect of ionic strength of the equilibrium solution upon lead adsorption/desorption in Brazilian Oxisols

    Directory of Open Access Journals (Sweden)

    Maria Aparecida Pereira Pierangeli

    2001-08-01

    Full Text Available A adsorção/dessorção de metais pelos solos é afetada por vários fatores, dentre os quais, a concentração salina da solução do solo. Este estudo teve o objetivo de avaliar o efeito da variação da força iônica da solução de equilíbrio (I sobre a adsorção/dessorção de Pb por Latossolos brasileiros. Amostras do horizonte A foram colocadas para reagir com Pb(NO32 0,15 mmol L-1 em Ca(NO32 5 e 50 mmol L-1 (pH 5,5; I = 15 e 150 mmol L-1; relação solo:solução 1:100, durante 72 horas. Em seguida, as amostras foram colocadas para dessorver em Ca(NO32 5 mmol L-1. Dos 17 Latossolos, apenas seis apresentaram diferenças significativas entre as quantidades adsorvidas nos dois valores de I. As correlações significativas obtidas entre as quantidades adsorvidas e alguns atributos dos solos (SiO2 e Fe2O3 do ataque sulfúrico, Fe d e Fe o, caulinita, hematita, CTC e superfície específica foram as mesmas para os dois valores de I. A variação de I durante a adsorção teve pouco efeito sobre a dessorção de chumbo. A não-variação da quantidade adsorvida com a mudança de I indica que o Pb é adsorvido, na maioria dos Latossolos, como complexo de esfera interna. Conclui-se que, dentro destas condições experimentais, o Pb não fez parte do complexo de troca da maioria dos solos estudados.The ionic strength of soil solution influences metal availability and mobility in soils. Laboratory experiments were conducted in order to evaluate the effect of solution ionic strength (I upon Pb adsorption/desorption in Ahorizon samples of 17 Brazilian Oxisols. The effect of I upon Pb adsorption was evaluated after a 72hour reaction of the soil samples with 0.15 mmol L-1 Pb(NO32 at pH 5.5, using 5 and 50 mmol L-1 Ca(NO32 as background solutions (I = 15 and 150 mmol L-1. Lead desorption was measured after a 72hour reaction of the soil samples with 5 mmol L-1 Ca(NO32 at pH 5.5. All experiments were performed with a 1:100 soil:solution ratio

  16. Functionalized ionic liquids and their applications

    Energy Technology Data Exchange (ETDEWEB)

    Hariprakasha, Humcha Krishnamurthy; Rangan, Krishnaswamy Kasthuri; Sudarshan, Tirumalai Srinivas

    2018-01-16

    Disclosure of functionalized ionic liquids. Use of disclosed ionic liquids as solvent for carbon dioxide. Use of disclosed ionic liquids as flame retardant. Use of disclosed ionic liquids for coating fabric to obtain flame retardant fabric.

  17. The Effects of Magnetic Exposure on the Nervous System: A study on the effects of low-strength low-frequency magnetic fields on neurotransmitter exocytosis and cell viability through ionic cyclotron resonance frequency

    Science.gov (United States)

    Saveriades, George

    This PhD dissertation focuses on the study of the effects of magnetic exposure on biological systems using amperometry techniques and viability assays. In our prior work based on the cyclotron resonance model, chromaffin cells in physiological saline and Ca2+-free media were exposed for 5 minutes to a 2.7 muT magnetic field, with frequency sweeps going from 30-60 Hz (targeting several ions involved in exocytosis) and 44-48 Hz (targeting specifically Ca2+ ions), with noticeable effects on exocytosis. The present study extended the work on chromaffin cells by covering frequency sweeps for different ions, manipulating the time of exposure and the strength of the magnetic field. Furthermore, amperometry was conducted on acute coronal brain slices, to demonstrate that the recorded effects could be measured on neuronal tissue. The viability of chromaffin cells and primary neuronal cultures exposed to magnetic fields was also addressed. The results demonstrate that cellular exocytosis is sensitive to the frequency of the magnetic field it is exposed to, the strength of the magnetic field and the duration of exposure. No significant effects were established with regards to the viability of the cells exposed to magnetic fields.

  18. Ionic liquids in chemical engineering.

    Science.gov (United States)

    Werner, Sebastian; Haumann, Marco; Wasserscheid, Peter

    2010-01-01

    The development of engineering applications with ionic liquids stretches back to the mid-1990s when the first examples of continuous catalytic processes using ionic liquids and the first studies of ionic liquid-based extractions were published. Ever since, the use of ionic liquids has seen tremendous progress in many fields of chemistry and engineering, and the first commercial applications have been reported. The main driver for ionic liquid engineering applications is to make practical use of their unique property profiles, which are the result of a complex interplay of coulombic, hydrogen bonding and van der Waals interactions. Remarkably, many ionic liquid properties can be tuned in a wide range by structural modifications at their cation and anion. This review highlights specific examples of ionic liquid applications in catalysis and in separation technologies. Additionally, the application of ionic liquids as working fluids in process machines is introduced.

  19. The preparation of steatite suspension for spray drying

    Science.gov (United States)

    Jirousek, L.; Spicak, K.

    1983-01-01

    Liquifying agents were investigated for preparation of highly concentrated steatite suspensions which are to be spray-dried. Organic additives for improving the molding properties and strength of green compacts are described. Demands on properties of the spray-dried granules are defined with regard to shrinkage of the molded compacts.

  20. Effects of biomolecules on the electrokinetics of colloidal nanoparticles in liquid suspension

    Science.gov (United States)

    Midelet, C.; Lin, J.-Y.; Tsang, S.; Sun, C.-l.; Midelet, J.; Kanaras, A. G.; Le Pioufle, B.; Français, O.; Werts, M. H. V.

    2017-02-01

    Electric fields can induce various types of motion in liquid suspensions of colloidal nanoparticles. These electrokinetic phenomena depend on the parameters of the electric field (frequency, amplitude, 3D topology), the particles (size, shape, composition) and the suspending liquid (polarizability, ionic strength, pH). In particular, the dielectrophoretic force on submicron colloidal particles is dependent on the properties of the electric double layer (the "ion cloud") around these particles. This dependence provides a mechanism for detecting and quantifying interactions between biomolecules and these nanoparticles, which can be combined with optical and spectroscopic measurements. Here, we report on functionalized plasmonic nanoparticles that are tracked inside microfluidic systems by dark-field video-microscopy. A high-gradient AC electric field is set up using transparent micro-electrodes. Electrohydrodynamic motion of the entire fluid and dielectrophoretic trapping of individual particles can be analyzed quantitatively by numerical methods. By switching the electric field synchronously with the video acquisition, the effect of biomolecules on the electrokinetic trapping can be quantified. The electromicrofluidic devices allow also for rapid measurement of diffusion coefficients.

  1. Ionic smoke detectors

    CERN Document Server

    2002-01-01

    Ionic smoke detectors are products incorporating radioactive material. This article summarises the process for their commercialization and marketing, and how the activity is controlled, according to regulations establishing strict design and production requisites to guarantee the absence of radiological risk associated both with their use and their final handling as conventional waste. (Author)

  2. INVESTIGATION OF THE PROPERTIES OF THE SUSPENSIONS FOR NON-STICK COATINGS FOR FOUNDRY

    Directory of Open Access Journals (Sweden)

    T. Gil’manshina

    2015-01-01

    Full Text Available The research aimed at figuring out dependence of the technological properties (density, thickness of the coating, reduced strength and sedimentation stability of the suspensions for nonstick coatings on the for activation time powder quartz graphite filler. It is shown that with increasing activation time to 10 minutes all the basic properties of graphite suspension powder quartz were improved. The paper presents the results of comparative studies of technological properties of suspensions of activated graphite oxide compositions prepared on the basis of activated aluminum oxide and periclase. The resulting suspension may be recommended for cast iron and non-ferrous castings.

  3. Dye-sensitized solar cells with ionic gel electrolytes prepared from imidazolium salts and agarose

    Energy Technology Data Exchange (ETDEWEB)

    Kazuharu, Suzuki; Makoto, Yamaguchi; Mikio, Kumagai [Institute of Research and Innovation, Photonics and Materials Research Dept., Takada, Kashiwa (Japan); Nobuo, Tanabe [Fujikura Ltd, Electronics Material Dept., Tokyo (Japan); Shozo, Yanagida [Osaka Univ. Center for Advanced Science and Innovation (Japan)

    2006-05-15

    New ionic gel electrolytes, semi-solid state electrolytes comprised of ionic liquid and gelator were investigated in order to improve the durability of dye-sensitized solar cells (DSCs). The ionic gels were prepared from agarose, natural polysaccharide, and 1-alkyl-3-methyl-imidazolium salts. The gels showed sufficient mechanical strength even though a very small amount of agarose was added (1.0-1.5 wt%). The photon to electron conversion efficiency of the DSCs containing ionic gel electrolyte was 2.93% under simulated sunlight (air mass 1.5) with a light intensity of 100 mW cm{sup -2}. (authors)

  4. Poiseuille flow of a Quincke suspension.

    Science.gov (United States)

    Cēbers, A

    2014-09-01

    The controversy of models of dielectric particle suspensions with antisymmetric stress, which predict a nonphysical cusp of the velocity profile in plane Poiseuille flow under the action of the electrical field, is resolved. In the mean-field approximation, the nonlinear kinetic equation is derived for coupled due to the flow translational and rotational motion of the particles. By its numerical solution, it is shown that the velocity profile is smeared due to the translational diffusion of the particles with opposite directions of rotation. The obtained results for the velocity profiles and flow rates as a function of the electric field strength are in qualitative agreement with the existing experimental results.

  5. Heteropolar Magnetic Suspension

    Science.gov (United States)

    Misovec, Kathleen; Johnson, Bruce; Downer, James; Eisenhaure, David; Hockney, Richard

    1990-01-01

    Compact permanent-magnet/electromagnet actuator has six degrees of freedom. Heteropolar magnetic actuator conceived for use as actively controlled vibration-isolating suspension device. Exerts forces along, and torques about, all three principal coordinate axes to resist all three components of translational vibration and all three components of rotational vibration. Inner cylinder suspended magnetically within outer cylinder. Electro-magnet coils interact with fields of permanent magnets to provide active control of suspending force and torque.

  6. IONIC LIQUIDS: PREPARATIONS AND LIMITATIONS

    Directory of Open Access Journals (Sweden)

    Dzulkefly Kuang Abdullah

    2010-11-01

    Full Text Available Ionic liquids are considered as an ideal alternative to volatile organic solvents and chemical industries in the future,because they are non-volatile. Ionic liquids are also considered as new novel chemical agents and widely regarded as agreener alternative to many commonly used solvents. Ionic liquids have been studied for a wide range of syntheticapplications and have attracted considerable interest for use as electrolytes in the areas of organic synthesis, catalysis,solar cell, fuel cells, electrodeposition and supercapacitors. However, some ionic liquids suffer from more or less somedrawbacks such as toxicity, preparation and high cost in the process for use. Most recently, three types of ionic liquidsare attracted much attentions specifically traditional ionic liquid, protic ionic liquid and deep eutectic solvent, wheretheir preparation, mechanism and limitation were differentiated. However, those liquids are having their ownadvantages and limitations based on applications. Traditional ionic liquid and protic ionic liquid are highly cost andtoxic for applied engineering research, but they consist of micro-biphasic systems composed of ionic compounds whichhave more varieties in the applications. The deep eutectic solvent is very economic for large-scale possessing but thereare only limited ionic mixtures to certain application such as electrochemistry.

  7. Surface Titrations of Perlite Suspensions.

    Science.gov (United States)

    Alkan; Do

    1998-11-01

    The surface charge behaviour of unexpanded and expanded perlite samples in KNO3 and NaCl solutions were investigated as a function of pH and ionic strength. The solutions of KNO3 and NaCl ranging from 10(-3) to 1.0 M were used. The potentiometric titration method was used to determine the surface charge of perlite samples. It was confirmed that the perlite samples had no the point of zero charge and was negatively charged in the pH range of 3-10. The double extrapolation method was used for determining the intrinsic equilibrium constants for simple ionization and complex ionization reactions. The values obtained are pKinta2 = 2.5 and p*KintK+ = 2.3 in KNO3 solutions and pKinta2 = 3.0 and p*KintNa+ = 2.4 in NaCl solutions for unexpanded perlite, and pKinta2 = 2.6 and p*KintK+ = 2.4 in KNO3 solutions and pKinta2 = 2.7 and pKintNa+ = 2.4 in NaCl solutions for expanded perlite. Copyright 1998 Academic Press.

  8. Core Muscle Activation in Suspension Training Exercises.

    Science.gov (United States)

    Cugliari, Giovanni; Boccia, Gennaro

    2017-02-01

    A quantitative observational laboratory study was conducted to characterize and classify core training exercises executed in a suspension modality on the base of muscle activation. In a prospective single-group repeated measures design, seventeen active male participants performed four suspension exercises typically associated with core training (roll-out, bodysaw, pike and knee-tuck). Surface electromyographic signals were recorded from lower and upper parts of rectus abdominis, external oblique, internal oblique, lower and upper parts of erector spinae muscles using concentric bipolar electrodes. The average rectified values of electromyographic signals were normalized with respect to individual maximum voluntary isometric contraction of each muscle. Roll-out exercise showed the highest activation of rectus abdominis and oblique muscles compared to the other exercises. The rectus abdominis and external oblique reached an activation higher than 60% of the maximal voluntary contraction (or very close to that threshold, 55%) in roll-out and bodysaw exercises. Findings from this study allow the selection of suspension core training exercises on the basis of quantitative information about the activation of muscles of interest. Roll-out and bodysaw exercises can be considered as suitable for strength training of rectus abdominis and external oblique muscles.

  9. Nanoscale Ionic Materials

    KAUST Repository

    Rodriguez, Robert

    2008-11-18

    Polymer nanocomposites (nanoparticles dispersed in a polymer matrix) have been the subject of intense research for almost two decades in both academic and industrial settings. This interest has been fueled by the ability of nanocomposites to not only improve the performance of polymers, but also by their ability to introduce new properties. Yet, there are still challenges that polymer nanocomposites must overcome to reach their full potential. In this Research News article we discuss a new class of hybrids termed nanoparticle ionic materials (NIMS). NIMS are organic-inorganic hybrid materials comprising a nanoparticle core functionalized with a covalently tethered ionic corona. They are facilely engineered to display flow properties that span the range from glassy solids to free flowing liquids. These new systems have unique properties that can overcome some of the challenges facing nanocomosite materials. © 2008 WILEY-VCH Verlag GmbH & Co. KGaA.

  10. Super ionic conductive glass

    Science.gov (United States)

    Susman, S.; Volin, K.J.

    Described is an ionically conducting glass for use as a solid electrolyte in a power or secondary cell containing an alkali metal-containing anode and a cathode separated by an alkali metal ion conducting glass having an ionic transference number of unity and the general formula: A/sub 1 + x/D/sub 2-x/3/Si/sub x/P/sub 3 - x/O/sub 12 - 2x/3/, wherein A is a network modifier for the glass and is an alkali metal of the anode, D is an intermediate for the glass and is selected from the class consisting of Zr, Ti, Ge, Al, Sb, Be, and Zn and X is in the range of from 2.25 to 3.0. Of the alkali metals, Na and Li are preferred and of the intermediate, Zr, Ti and Ge are preferred.

  11. Pyrrolidinium Ionic Liquid Crystals

    OpenAIRE

    Goossens, Karel; Lava, Kathleen; Nockemann, Peter; Van Hecke, Kristof; Van Meervelt, Luc; Driesen, Kris; Görller-Walrand, Christiane; Binnemans, Koen; Cardinaels, Thomas

    2009-01-01

    N-Alkyl-N-methylpyrrolidinium cations have been used for the design of ionic liquid crystals, including a new type of uranium-containing metallomesogen. Pyrrolidinium salts with bromide, bis(trifluoromethylsulfonyl)-imide, tetrafluoroborate, hexafluorophosphate, thiocyanate, tetrakis(2-thenoyltrifluoroacetonato)europate(III) and tetrabromouranyl] counteranions were prepared. For the bromide salts and tetrabromouranyl compounds, the chain length of the alkyl group CnH2n+1 was varied from eight...

  12. Ionic contamination detection

    Science.gov (United States)

    Benkovich, M. G.

    1994-04-01

    The effectiveness of Meter A and B for detecting ionic contamination was evaluated and compared on the following types of samples: (1) copper panels; (2) printed wiring boards with through-hold components (IC's); (3) printed wiring boards with surface-mounted components; and (4) mixed-technology printed wiring boards (both through-hole and surface-mount components). The extraction efficiency of the two meters was calculated.

  13. Strength Training

    Science.gov (United States)

    ... big difference between strength training, powerlifting, and competitive bodybuilding! Strength training uses resistance methods like free weights, ... a person can lift at one time. Competitive bodybuilding involves evaluating muscle definition and symmetry, as well ...

  14. The influence of pH and media composition on suspension stability of Ag, ZnO, and TiO2 nanoparticles and immobilization of Daphnia magna under guideline testing conditions

    DEFF Research Database (Denmark)

    Cupi, Denisa; Hartmann, Nanna B.; Baun, Anders

    2015-01-01

    profile of ENPs in aquatic media applicable in OECD guideline. In this study we focus on controlling stability (as point of zero charge) by employing changes in pH to media of different ionic strength (M7, and Very Soft EPA medium) and documenting the influence of these parameters on acute immobilization...... of Daphnia magna. Despite being sterically stabilized, test suspensions of Ag NPs were found to consist of large agglomerate sizes (close to μm range) for both VS EPA and M7 media. The toxicity of the AgNPs was found to be higher in VS EPA medium than in M7 medium caused by an increased dissolution in VS EPA...

  15. Course on Ionic Channels

    CERN Document Server

    1986-01-01

    This book is based on a series of lectures for a course on ionic channels held in Santiago, Chile, on November 17-20, 1984. It is intended as a tutorial guide on the properties, function, modulation, and reconstitution of ionic channels, and it should be accessible to graduate students taking their first steps in this field. In the presentation there has been a deliberate emphasis on the spe­ cific methodologies used toward the understanding of the workings and function of channels. Thus, in the first section, we learn to "read" single­ channel records: how to interpret them in the theoretical frame of kinetic models, which information can be extracted from gating currents in re­ lation to the closing and opening processes, and how ion transport through an open channel can be explained in terms of fluctuating energy barriers. The importance of assessing unequivocally the origin and purity of mem­ brane preparations and the use of membrane vesicles and optical tech­ niques in the stUGY of ionic channels a...

  16. 31 CFR 10.82 - Expedited suspension.

    Science.gov (United States)

    2010-07-01

    ... 31 Money and Finance: Treasury 1 2010-07-01 2010-07-01 false Expedited suspension. 10.82 Section... INTERNAL REVENUE SERVICE Rules Applicable to Disciplinary Proceedings § 10.82 Expedited suspension. (a... suspension. A suspension under this section will commence on the date that written notice of the suspension...

  17. Graphene-ionic liquid composites

    Energy Technology Data Exchange (ETDEWEB)

    Aksay, Ilhan A.; Korkut, Sibel; Pope, Michael; Punckt, Christian

    2016-11-01

    Method of making a graphene-ionic liquid composite. The composite can be used to make elec-trodes for energy storage devices, such as batteries and supercapacitors. Dis-closed and claimed herein is method of making a graphene-ionic liquid com-posite, comprising combining a graphene source with at least one ionic liquid and heating the combination at a temperature of at least about 130 .degree. C.

  18. 48 CFR 209.407 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 48 Federal Acquisition Regulations System 3 2010-10-01 2010-10-01 false Suspension. 209.407... OF DEFENSE ACQUISITION PLANNING CONTRACTOR QUALIFICATIONS Debarment, Suspension, and Ineligibility 209.407 Suspension. ...

  19. Swelling, Compressibility, and Phase Behavior of Soft Ionic Microgels

    Science.gov (United States)

    Denton, Alan

    Soft colloids have inspired great attention recently for their rich and tunable materials properties. Particular interest has focused on microgels - microscopic cross-linked polymer gel particles that, when dispersed in water, become swollen and can acquire charge through dissociation of counterions. Electrostatic interparticle interactions strongly influence the structure and thermodynamics of ionic microgel suspensions*. Permeability to solvent molecules and small ions creates a competition between elastic and electrostatic forces that determines equilibrium particle sizes. Swelling can be controlled by adjusting temperature, pH, and salt concentration, with applications to chemical/biosensing and targeted drug delivery. By combining molecular dynamics and Monte Carlo simulation with Poisson-Boltzmann theory of electrostatics and Flory-Rehner theory of swollen polymer networks, we investigate swelling and compressibility of ionic microgel particles and implications for thermodynamic phase behavior of bulk suspensions at concentrations approaching and exceeding hard-sphere close packing. Predictions for particle size and osmotic pressure are compared with available experimental data. This work was supported by the National Science Foundation under Grant No. DMR-1106331.

  20. Regularities of ultrasonography of suspensions of alumina nanoparticles in biological media

    OpenAIRE

    Shklyar, T. F.; D'yachkova, E. P.; Dinislamova, O. A.; Safronov, A. P.; Leiman, D. V.; Blyakhman, F. A.

    2013-01-01

    This paper studies the echo-contrast properties of an alumina nanopowder suspension using ultrasonography (US) fully corresponding in its characteristics to the techniques of medical ultrasound diagnostics of organs and tissues. The purpose of this study was to search for the possible effect of the ionic and protein composition of the biological medium on the intensity of the reflected echo signal of the contrast material based on nanoparticles. It was found that the pH of the blood promotes ...

  1. High ionic strength or presence of inositol hexakisphosphate ...

    African Journals Online (AJOL)

    The kinetics of the reaction of 5,5'-dithiobis(2-nitrobenzoate) with guinea pig oxy- and carbonmonoxyhaemoglobin are biphasic. The two phases differ in rate by two orders of magnitude. For the fast phase, quantitative analysis of the pH dependence of the apparent second order rate constant, kapp, shows that it has all the ...

  2. Reproduction of Venezulean Equine Encephalomyelitis Virus at Low Ionic Strength

    Science.gov (United States)

    1975-02-28

    using electron microscopy, that Sthe formation of nucleoides of VEE virus occurs near vacuoles formed in the cytoplasm of infected cells ard the...formation of supercapsides as a result of the nucleoide gemmation on the walls of cytoplasmic membranes. The problem posed for this study included an... nucleoides . A comparison of the position of the structures in the gradient with the sedimentation * of the virion ribonucleoproteid secreted from the

  3. Ionic strength effects: Tunable nanocrystal distribution in colloidal gold films

    NARCIS (Netherlands)

    Kooij, Ernst S.; Brouwer, E.A.M.; Wormeester, Herbert; Poelsema, Bene; Schwarz, James A.; Contescu, Cristian I.; Putyera, Karol

    2004-01-01

    The self-assembly of colloidal particles into disordered structures or highly ordered superlattices can be achieved in different ways. Hydrodynamic forces during controlled drying allow control over the deposition process by varying the solvent vapor pressure and temperature, or, more physically, by

  4. The improvement of suspension training for trunk muscle power in Sanda athletes

    Directory of Open Access Journals (Sweden)

    Xiujie Ma

    2017-12-01

    Full Text Available The aim of this study was to investigate whether both suspension training (ST and traditional training (TT can improve Sanda athlete's strength quality of trunk muscles and to explore the effect of suspension training on Sanda athletes' trunk muscle power production. Twelve elite Sanda athletes from the Competitive Sports School of Shanghai University of Sport were randomly assigned to experimental group (EG and control group (CG. EG and CG were regularly trained with suspension training and traditional strength training for 40 minutes three times per week. The total duration of training was 10 weeks. The measurements including peak torque (PT, PT/body weight (BW, and rate of force development (RFD were used to assess trunk muscles strength. The results showed that there were significant differences between the two groups' performance when it was tested at the higher velocity of dynamometer (test of muscle power, but less significant differences when the two groups performance was tested at the lower velocity of dynamometer (test of maximum strength. The conclusion of this study is that compared with traditional training methods, suspension training can improve back and trunk flexion muscles strength more effectively. In particular, suspension training can improve the explosive power of trunk extension and flexion muscles.

  5. Release Mechanism Between Ion Osmotic Pressure and Drug Release in Ionic-Driven Osmotic Pump Tablets (I).

    Science.gov (United States)

    Cheng, Lizhen; Gao, Siqi; Ouyang, Defang; Wang, Haiying; Wang, Yongfei; Pan, Weisan; Yang, Xinggang

    2018-02-01

    The objective of this study was to develop an authentic ionic-driven osmotic pump system and investigate the release mechanism, simultaneously exploring the in vitro and in vivo correlation of the ionic-driven osmotic pump tablet. A comparison of the ionic-driven and conventional theophylline osmotic pump, the influence of pH and the amount of sodium chloride on drug release, the relationship between the ionic osmotic pressure and the drug release, and the pharmacokinetics experiment in beagle dogs were investigated. Consequently, the similarity factor (f 2 ) between the novel and conventional theophylline osmotic pump tablet was 60.18, which indicated a similar drug-release behavior. Also, the release profile fitted a zero-order kinetic model. The relative bioavailability of the ionic-driven osmotic pump to the conventional osmotic pump calculated from the AUC (0-∞) was 93.6% and the coefficient (R = 0.9945) confirmed that the ionic-driven osmotic pump exhibited excellent IVIVC. The driving power of the ionic-driven osmotic pump was produced only by ions, which was strongly dependent on the ion strength, and a novel formula for the ionic-driven osmotic pump was derived which indicated that the drug-release rate was proportional to the ionic osmotic pressure and the sodium chloride concentration. Significantly, the formula can predict the drug-release rate and release characteristics of theophylline ionic-driven osmotic pumps, guiding future modification of the ionic osmotic pump.

  6. 49 CFR 238.427 - Suspension system.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Suspension system. 238.427 Section 238.427... Equipment § 238.427 Suspension system. (a) General requirements. (1) Suspension systems shall be designed to... equipment. (2) Passenger equipment shall meet the safety performance standards for suspension systems...

  7. 78 FR 57525 - Suspension of Community Eligibility

    Science.gov (United States)

    2013-09-19

    ... SECURITY Federal Emergency Management Agency 44 CFR Part 64 Suspension of Community Eligibility AGENCY...) that are scheduled for suspension on the effective dates listed within this rule because of... measures prior to the effective suspension date given in this rule, the suspension will not occur and a...

  8. 48 CFR 2909.407 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 48 Federal Acquisition Regulations System 7 2010-10-01 2010-10-01 false Suspension. 2909.407... CONTRACTOR QUALIFICATIONS Debarment, Suspension, and Ineligibility 2909.407 Suspension. (a) The Senior... authorized to make an exception, regarding suspension by another agency suspending official under the...

  9. 14 CFR 1267.670 - Suspension.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 5 2010-01-01 2010-01-01 false Suspension. 1267.670 Section 1267.670... WORKPLACE (FINANCIAL ASSISTANCE) Definitions § 1267.670 Suspension. Suspension means an action taken by a..., subpart 9.4) and the common rule, Government-wide Debarment and Suspension (Nonprocurement), that...

  10. 22 CFR 1008.670 - Suspension.

    Science.gov (United States)

    2010-04-01

    ... 22 Foreign Relations 2 2010-04-01 2010-04-01 true Suspension. 1008.670 Section 1008.670 Foreign... ASSISTANCE) Definitions § 1008.670 Suspension. Suspension means an action taken by a Federal agency that...-wide Debarment and Suspension (Nonprocurement), that implements Executive Order 12549 and Executive...

  11. 2 CFR 182.670 - Suspension.

    Science.gov (United States)

    2010-01-01

    ... 2 Grants and Agreements 1 2010-01-01 2010-01-01 false Suspension. 182.670 Section 182.670 Grants... Suspension. Suspension means an action taken by a Federal agency that immediately prohibits a recipient from... guidance on nonprocurement debarment and suspension (2 CFR part 180, which implements Executive Orders...

  12. 40 CFR 36.670 - Suspension.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 1 2010-07-01 2010-07-01 false Suspension. 36.670 Section 36.670... REQUIREMENTS FOR DRUG-FREE WORKPLACE (FINANCIAL ASSISTANCE) Definitions § 36.670 Suspension. Suspension means... contracts (48 CFR part 9, subpart 9.4) and the common rule, Government-wide Debarment and Suspension...

  13. 78 FR 5734 - Suspension of Community Eligibility

    Science.gov (United States)

    2013-01-28

    ... SECURITY Federal Emergency Management Agency 44 CFR Part 64 Suspension of Community Eligibility AGENCY...) that are scheduled for suspension on the effective dates listed within this rule because of... measures prior to the effective suspension date given in this rule, the suspension will not occur and a...

  14. 77 FR 53775 - Suspension of Community Eligibility

    Science.gov (United States)

    2012-09-04

    ... SECURITY Federal Emergency Management Agency 44 CFR Part 64 Suspension of Community Eligibility AGENCY...) that are scheduled for suspension on the effective dates listed within this rule because of... measures prior to the effective suspension date given in this rule, the suspension will not occur and a...

  15. 29 CFR 94.670 - Suspension.

    Science.gov (United States)

    2010-07-01

    ... 29 Labor 1 2010-07-01 2010-07-01 true Suspension. 94.670 Section 94.670 Labor Office of the... § 94.670 Suspension. Suspension means an action taken by a Federal agency that immediately prohibits a... Debarment and Suspension (Nonprocurement), that implements Executive Order 12549 and Executive Order 12689...

  16. 45 CFR 1173.670 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 45 Public Welfare 3 2010-10-01 2010-10-01 false Suspension. 1173.670 Section 1173.670 Public... (FINANCIAL ASSISTANCE) Definitions § 1173.670 Suspension. Suspension means an action taken by a Federal..., subpart 9.4) and the common rule, Government-wide Debarment and Suspension (Nonprocurement), that...

  17. 45 CFR 1641.11 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 45 Public Welfare 4 2010-10-01 2010-10-01 false Suspension. 1641.11 Section 1641.11 Public Welfare Regulations Relating to Public Welfare (Continued) LEGAL SERVICES CORPORATION DEBARMENT, SUSPENSION AND REMOVAL OF RECIPIENT AUDITORS Suspension § 1641.11 Suspension. (a) IPAs suspended from providing audit...

  18. 77 FR 2646 - Suspension of Community Eligibility

    Science.gov (United States)

    2012-01-19

    ... SECURITY Federal Emergency Management Agency 44 CFR Part 64 Suspension of Community Eligibility AGENCY...) that are scheduled for suspension on the effective dates listed within this rule because of... measures prior to the effective suspension date given in this rule, the suspension will not occur and a...

  19. 31 CFR 19.1015 - Suspension.

    Science.gov (United States)

    2010-07-01

    ... 31 Money and Finance: Treasury 1 2010-07-01 2010-07-01 false Suspension. 19.1015 Section 19.1015 Money and Finance: Treasury Office of the Secretary of the Treasury GOVERNMENTWIDE DEBARMENT AND SUSPENSION (NONPROCUREMENT) Definitions § 19.1015 Suspension. Suspension is an action taken by a suspending...

  20. 41 CFR 105-68.1015 - Suspension.

    Science.gov (United States)

    2010-07-01

    ... 41 Public Contracts and Property Management 3 2010-07-01 2010-07-01 false Suspension. 105-68.1015 Section 105-68.1015 Public Contracts and Property Management Federal Property Management Regulations...-GOVERNMENTWIDE DEBARMENT AND SUSPENSION (NONPROCUREMENT) Definitions § 105-68.1015 Suspension. Suspension is an...

  1. 15 CFR 29.670 - Suspension.

    Science.gov (United States)

    2010-01-01

    ... 15 Commerce and Foreign Trade 1 2010-01-01 2010-01-01 false Suspension. 29.670 Section 29.670... WORKPLACE (FINANCIAL ASSISTANCE) Definitions § 29.670 Suspension. Suspension means an action taken by a..., subpart 9.4) and the common rule, Government-wide Debarment and Suspension (Nonprocurement), that...

  2. 13 CFR 147.670 - Suspension.

    Science.gov (United States)

    2010-01-01

    ... 13 Business Credit and Assistance 1 2010-01-01 2010-01-01 false Suspension. 147.670 Section 147...-FREE WORKPLACE (NONPROCUREMENT) Definitions § 147.670 Suspension. Suspension means an action taken by a..., subpart 9.4) and the common rule, Government-wide Debarment and Suspension (Nonprocurement), that...

  3. 78 FR 2622 - Suspension of Community Eligibility

    Science.gov (United States)

    2013-01-14

    ... SECURITY Federal Emergency Management Agency 44 CFR Part 64 Suspension of Community Eligibility AGENCY...) that are scheduled for suspension on the effective dates listed within this rule because of... measures prior to the effective suspension date given in this rule, the suspension will not occur and a...

  4. 10 CFR 607.670 - Suspension.

    Science.gov (United States)

    2010-01-01

    ... 10 Energy 4 2010-01-01 2010-01-01 false Suspension. 607.670 Section 607.670 Energy DEPARTMENT OF... ASSISTANCE) Definitions § 607.670 Suspension. Suspension means an action taken by a Federal agency that...-wide Debarment and Suspension (Nonprocurement), that implements Executive Order 12549 and Executive...

  5. 76 FR 9666 - Suspension of Community Eligibility

    Science.gov (United States)

    2011-02-22

    ... SECURITY Federal Emergency Management Agency 44 CFR Part 64 Suspension of Community Eligibility AGENCY...), that are scheduled for suspension on the effective dates listed within this rule because of... measures prior to the effective suspension date given in this rule, the suspension will not occur and a...

  6. 29 CFR 1471.1015 - Suspension.

    Science.gov (United States)

    2010-07-01

    ... 29 Labor 4 2010-07-01 2010-07-01 false Suspension. 1471.1015 Section 1471.1015 Labor Regulations Relating to Labor (Continued) FEDERAL MEDIATION AND CONCILIATION SERVICE GOVERNMENTWIDE DEBARMENT AND SUSPENSION (NONPROCUREMENT) Definitions § 1471.1015 Suspension. Suspension is an action taken by a suspending...

  7. 22 CFR 133.670 - Suspension.

    Science.gov (United States)

    2010-04-01

    ... 22 Foreign Relations 1 2010-04-01 2010-04-01 false Suspension. 133.670 Section 133.670 Foreign... ASSISTANCE) Definitions § 133.670 Suspension. Suspension means an action taken by a Federal agency that...-wide Debarment and Suspension (Nonprocurement), that implements Executive Order 12549 and Executive...

  8. 43 CFR 43.670 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 43 Public Lands: Interior 1 2010-10-01 2010-10-01 false Suspension. 43.670 Section 43.670 Public... WORKPLACE (FINANCIAL ASSISTANCE) Definitions § 43.670 Suspension. Suspension means an action taken by a..., subpart 9.4) and 2 CFR part 180. Suspension of a recipient is a distinct and separate action from...

  9. 22 CFR 312.670 - Suspension.

    Science.gov (United States)

    2010-04-01

    ... 22 Foreign Relations 2 2010-04-01 2010-04-01 true Suspension. 312.670 Section 312.670 Foreign... § 312.670 Suspension. Suspension means an action taken by a Federal agency that immediately prohibits a... Debarment and Suspension (Nonprocurement), that implements Executive Order 12549 and Executive Order 12689...

  10. 34 CFR 84.670 - Suspension.

    Science.gov (United States)

    2010-07-01

    ... 34 Education 1 2010-07-01 2010-07-01 false Suspension. 84.670 Section 84.670 Education Office of... ASSISTANCE) Definitions § 84.670 Suspension. Suspension means an action taken by a Federal agency that...-wide Debarment and Suspension (Nonprocurement), that implements Executive Order 12549 and Executive...

  11. 77 FR 7537 - Suspension of Community Eligibility

    Science.gov (United States)

    2012-02-13

    ... SECURITY Federal Emergency Management Agency 44 CFR Part 64 Suspension of Community Eligibility AGENCY...) that are scheduled for suspension on the effective dates listed within this rule because of... measures prior to the effective suspension date given in this rule, the suspension will not occur and a...

  12. 19 CFR 146.82 - Suspension.

    Science.gov (United States)

    2010-04-01

    ... 19 Customs Duties 2 2010-04-01 2010-04-01 false Suspension. 146.82 Section 146.82 Customs Duties U... (CONTINUED) FOREIGN TRADE ZONES Penalties; Suspension; Revocation § 146.82 Suspension. (a) For cause. The... for a period not to exceed 90 days. Upon order of the Board the suspension may be continued. If...

  13. 77 FR 24858 - Suspension of Community Eligibility

    Science.gov (United States)

    2012-04-26

    ... SECURITY Federal Emergency Management Agency 44 CFR Part 64 Suspension of Community Eligibility AGENCY...) that are scheduled for suspension on the effective dates listed within this rule because of... measures prior to the effective suspension date given in this rule, the suspension will not occur and a...

  14. 75 FR 5890 - Suspension of Community Eligibility

    Science.gov (United States)

    2010-02-05

    ... SECURITY Federal Emergency Management Agency 44 CFR Part 64 Suspension of Community Eligibility AGENCY...), that are scheduled for suspension on the effective dates listed within this rule because of... measures prior to the effective suspension date given in this rule, the suspension will not occur and a...

  15. 76 FR 39782 - Suspension of Community Eligibility

    Science.gov (United States)

    2011-07-07

    ... SECURITY Federal Emergency Management Agency 44 CFR Part 64 Suspension of Community Eligibility AGENCY...), that are scheduled for suspension on the effective dates listed within this rule because of... measures prior to the effective suspension date given in this rule, the suspension will not occur and a...

  16. 22 CFR 1509.670 - Suspension.

    Science.gov (United States)

    2010-04-01

    ... 22 Foreign Relations 2 2010-04-01 2010-04-01 true Suspension. 1509.670 Section 1509.670 Foreign... ASSISTANCE) Definitions § 1509.670 Suspension. Suspension means an action taken by a Federal agency that...-wide Debarment and Suspension (Nonprocurement), that implements Executive Order 12549 and Executive...

  17. 22 CFR 210.670 - Suspension.

    Science.gov (United States)

    2010-04-01

    ... 22 Foreign Relations 1 2010-04-01 2010-04-01 false Suspension. 210.670 Section 210.670 Foreign... (FINANCIAL ASSISTANCE) Definitions § 210.670 Suspension. Suspension means an action taken by a Federal agency..., subpart 9.4) and the common rule, Government-wide Debarment and Suspension (Nonprocurement), that...

  18. 45 CFR 1206.1-4 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 45 Public Welfare 4 2010-10-01 2010-10-01 false Suspension. 1206.1-4 Section 1206.1-4 Public... GRANTS AND CONTRACTS-SUSPENSION AND TERMINATION AND DENIAL OF APPLICATION FOR REFUNDING Suspension and Termination of Assistance § 1206.1-4 Suspension. (a) General. The responsible Corporation official may suspend...

  19. 31 CFR 20.670 - Suspension.

    Science.gov (United States)

    2010-07-01

    ... 31 Money and Finance: Treasury 1 2010-07-01 2010-07-01 false Suspension. 20.670 Section 20.670...-FREE WORKPLACE (FINANCIAL ASSISTANCE) Definitions § 20.670 Suspension. Suspension means an action taken..., subpart 9.4) and the common rule, Government-wide Debarment and Suspension (Nonprocurement), that...

  20. 78 FR 68999 - Suspension of Community Eligibility

    Science.gov (United States)

    2013-11-18

    ... SECURITY Federal Emergency Management Agency 44 CFR Part 64 Suspension of Community Eligibility AGENCY...) that are scheduled for suspension on the effective dates listed within this rule because of... measures prior to the effective suspension date given in this rule, the suspension will not occur and a...

  1. 29 CFR 1472.670 - Suspension.

    Science.gov (United States)

    2010-07-01

    ... 29 Labor 4 2010-07-01 2010-07-01 false Suspension. 1472.670 Section 1472.670 Labor Regulations... DRUG-FREE WORKPLACE (FINANCIAL ASSISTANCE) Definitions § 1472.670 Suspension. Suspension means an... CFR part 9, subpart 9.4) and the common rule, Government-wide Debarment and Suspension (Nonprocurement...

  2. 24 CFR 21.670 - Suspension.

    Science.gov (United States)

    2010-04-01

    ... 24 Housing and Urban Development 1 2010-04-01 2010-04-01 false Suspension. 21.670 Section 21.670... GOVERNMENTWIDE REQUIREMENTS FOR DRUG-FREE WORKPLACE (GRANTS) Definitions § 21.670 Suspension. Suspension means an... CFR part 9, subpart 9.4) and the common rule, Government-wide Debarment and Suspension (Nonprocurement...

  3. 77 FR 9856 - Suspension of Community Eligibility

    Science.gov (United States)

    2012-02-21

    ... SECURITY Federal Emergency Management Agency 44 CFR Part 64 Suspension of Community Eligibility AGENCY...) that are scheduled for suspension on the effective dates listed within this rule because of... measures prior to the effective suspension date given in this rule, the suspension will not occur and a...

  4. 49 CFR 32.670 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 1 2010-10-01 2010-10-01 false Suspension. 32.670 Section 32.670 Transportation... ASSISTANCE) Definitions § 32.670 Suspension. Suspension means an action taken by a Federal agency that...-wide Debarment and Suspension (Nonprocurement), that implements Executive Order 12549 and Executive...

  5. 21 CFR 1405.670 - Suspension.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 9 2010-04-01 2010-04-01 false Suspension. 1405.670 Section 1405.670 Food and... (FINANCIAL ASSISTANCE) Definitions § 1405.670 Suspension. Suspension means an action taken by a Federal..., subpart 9.4) and the common rule, Government-wide Debarment and Suspension (Nonprocurement), that...

  6. 50 CFR 13.27 - Permit suspension.

    Science.gov (United States)

    2010-10-01

    ... 50 Wildlife and Fisheries 1 2010-10-01 2010-10-01 false Permit suspension. 13.27 Section 13.27... GENERAL PERMIT PROCEDURES Permit Administration § 13.27 Permit suspension. (a) Criteria for suspension... Government. Such suspension shall remain in effect until the issuing officer determines that the permittee...

  7. 45 CFR 1155.670 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 45 Public Welfare 3 2010-10-01 2010-10-01 false Suspension. 1155.670 Section 1155.670 Public... ASSISTANCE) Definitions § 1155.670 Suspension. Suspension means an action taken by a Federal agency that...-wide Debarment and Suspension (Nonprocurement), that implements Executive Order 12549 and Executive...

  8. 78 FR 57523 - Suspension of Community Eligibility

    Science.gov (United States)

    2013-09-19

    ... SECURITY Federal Emergency Management Agency 44 CFR Part 64 Suspension of Community Eligibility AGENCY...) that are scheduled for suspension on the effective dates listed within this rule because of... measures prior to the effective suspension date given in this rule, the suspension will not occur and a...

  9. 5 CFR 919.1015 - Suspension.

    Science.gov (United States)

    2010-01-01

    ... 5 Administrative Personnel 2 2010-01-01 2010-01-01 false Suspension. 919.1015 Section 919.1015 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT (CONTINUED) CIVIL SERVICE REGULATIONS (CONTINUED) GOVERNMENTWIDE DEBARMENT AND SUSPENSION (NONPROCUREMENT) Definitions § 919.1015 Suspension. Suspension is an...

  10. 78 FR 2624 - Suspension of Community Eligibility

    Science.gov (United States)

    2013-01-14

    ... SECURITY Federal Emergency Management Agency 44 CFR Part 64 Suspension of Community Eligibility AGENCY...) that are scheduled for suspension on the effective dates listed within this rule because of... measures prior to the effective suspension date given in this rule, the suspension will not occur and a...

  11. 76 FR 2596 - Suspension of Community Eligibility

    Science.gov (United States)

    2011-01-14

    ... SECURITY Federal Emergency Management Agency 44 CFR Part 64 Suspension of Community Eligibility AGENCY...), that are scheduled for suspension on the effective dates listed within this rule because of... measures prior to the effective suspension date given in this rule, the suspension will not occur and a...

  12. 75 FR 52861 - Suspension of Community Eligibility

    Science.gov (United States)

    2010-08-30

    ... SECURITY Federal Emergency Management Agency 44 CFR Part 64 Suspension of Community Eligibility AGENCY...), that are scheduled for suspension on the effective dates listed within this rule because of... measures prior to the effective suspension date given in this rule, the suspension will not occur and a...

  13. 28 CFR 83.670 - Suspension.

    Science.gov (United States)

    2010-07-01

    ... 28 Judicial Administration 2 2010-07-01 2010-07-01 false Suspension. 83.670 Section 83.670... WORKPLACE (GRANTS) Definitions § 83.670 Suspension. Suspension means an action taken by a Federal agency..., subpart 9.4) and the common rule, Government-wide Debarment and Suspension (Nonprocurement), that...

  14. 39 CFR 957.27 - Suspension.

    Science.gov (United States)

    2010-07-01

    ... 39 Postal Service 1 2010-07-01 2010-07-01 false Suspension. 957.27 Section 957.27 Postal Service... SUSPENSION FROM CONTRACTING § 957.27 Suspension. (a) Any firm or individual suspended under chapter 3, section 7 of the Postal Service Purchasing Manual who believes that the suspension has not been in...

  15. 7 CFR 3021.670 - Suspension.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 15 2010-01-01 2010-01-01 false Suspension. 3021.670 Section 3021.670 Agriculture... Suspension. Suspension means an action taken by a Federal agency that immediately prohibits a recipient from... Debarment and Suspension (Nonprocurement), that implements Executive Order 12549 and Executive Order 12689...

  16. 76 FR 5284 - Suspension of Community Eligibility

    Science.gov (United States)

    2011-01-31

    ... SECURITY Federal Emergency Management Agency 44 CFR Part 64 Suspension of Community Eligibility AGENCY...), that are scheduled for suspension on the effective dates listed within this rule because of... measures prior to the effective suspension date given in this rule, the suspension will not occur and a...

  17. 78 FR 69001 - Suspension of Community Eligibility

    Science.gov (United States)

    2013-11-18

    ... SECURITY Federal Emergency Management Agency 44 CFR Part 64 Suspension of Community Eligibility AGENCY...) that are scheduled for suspension on the effective dates listed within this rule because of... measures prior to the effective suspension date given in this rule, the suspension will not occur and a...

  18. 45 CFR 630.670 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 45 Public Welfare 3 2010-10-01 2010-10-01 false Suspension. 630.670 Section 630.670 Public Welfare... DRUG-FREE WORKPLACE (FINANCIAL ASSISTANCE) Definitions § 630.670 Suspension. Suspension means an action... CFR part 9, subpart 9.4) and the common rule, Government-wide Debarment and Suspension (Nonprocurement...

  19. 20 CFR 439.670 - Suspension.

    Science.gov (United States)

    2010-04-01

    ... 20 Employees' Benefits 2 2010-04-01 2010-04-01 false Suspension. 439.670 Section 439.670 Employees... ASSISTANCE) Definitions § 439.670 Suspension. Suspension means an action taken by a Federal agency that...-wide Debarment and Suspension (Nonprocurement), that implements Executive Order 12549 and Executive...

  20. 75 FR 9111 - Suspension of Community Eligibility

    Science.gov (United States)

    2010-03-01

    ... SECURITY Federal Emergency Management Agency 44 CFR Part 64 Suspension of Community Eligibility AGENCY...), that are scheduled for suspension on the effective dates listed within this rule because of... measures prior to the effective suspension date given in this rule, the suspension will not occur and a...

  1. 77 FR 63753 - Suspension of Community Eligibility

    Science.gov (United States)

    2012-10-17

    ... SECURITY Federal Emergency Management Agency 44 CFR Part 64 Suspension of Community Eligibility AGENCY...) that are scheduled for suspension on the effective dates listed within this rule because of... measures prior to the effective suspension date given in this rule, the suspension will not occur and a...

  2. 77 FR 2650 - Suspension of Community Eligibility

    Science.gov (United States)

    2012-01-19

    ... SECURITY Federal Emergency Management Agency 44 CFR Part 64 Suspension of Community Eligibility AGENCY...) that are scheduled for suspension on the effective dates listed within this rule because of... measures prior to the effective suspension date given in this rule, the suspension will not occur and a...

  3. 78 FR 5736 - Suspension of Community Eligibility

    Science.gov (United States)

    2013-01-28

    ... SECURITY Federal Emergency Management Agency 44 CFR Part 64 Suspension of Community Eligibility AGENCY...) that are scheduled for suspension on the effective dates listed within this rule because of... measures prior to the effective suspension date given in this rule, the suspension will not occur and a...

  4. Direct exfoliation of natural graphite into micrometre size few layers graphene sheets using ionic liquids.

    Science.gov (United States)

    Wang, Xiqing; Fulvio, Pasquale F; Baker, Gary A; Veith, Gabriel M; Unocic, Raymond R; Mahurin, Shannon M; Chi, Miaofang; Dai, Sheng

    2010-07-07

    Stable high-concentration suspensions (up to 0.95 mg mL(-1)) of non-oxidized few layer graphene (FLG), five or less sheets, with micrometre-long edges were obtained via direct exfoliation of natural graphite flakes in ionic liquids, such as 1-butyl-3-methyl-imidazolium bis(trifluoro-methane-sulfonyl)imide ([Bmim]-[Tf(2)N]), by tip ultrasonication.

  5. Evaluation of effect of tween 80 on characteristics of tadalafil 0.1% suspension

    Directory of Open Access Journals (Sweden)

    Majid Saeedi

    2015-06-01

    Full Text Available Tadalafil is a phosphodiesterase 5 inhibitor used orally as solid dosage form. The suspension of this drug has been used for pulmonary arterial hypertension treatment in pediatrics. The aim of this work was to investigate the influence of non-ionic surfactant (Tween 80 on the physical characteristics, drug particle size, and stress-shear rate rheogram of tadalafil 0.1% suspension. Several formulations prepared by xanthan gum as suspending agent. Glycerin has been used as wetting agent. The several amounts of Tween 80 were added and the characteristics of suspensions were evaluated during 6 months. The results showed the effect of surfactant on sediment volume and resuspendibility. The particle size of tadalafil was affected by surfactant amount. This result showed an optimum effect of Tween 80 on drug particle size. The viscosity behavior evaluation of tadalafil 0.1% suspension showed Tween 80 effect. This study showed that Tween 80 can dramatically affect viscosity of suspensions. The results of this study have demonstrated the effect of Tween 80 on physical properties of tadalafil 0.1% oral suspension. An ideal drug particle size was observed in particular amount of Tween 80 (0.15% w/v.

  6. "Point de suspension"

    CERN Multimedia

    2004-01-01

    CERN - Globe of Science and Innovation 20 and 21 October Acrobatics, mime, a cappella singing, projections of images, a magical setting... a host of different tools of a grandeur matching that of the Universe they relate. A camera makes a massive zoom out to reveal the multiple dimensions of Nature. Freeze the frame: half way between the infinitesimally small and the infinitesimally large, a man suspends his everyday life (hence the title "Point de Suspension", which refers to the three dots at the end of an uncompleted sentence) to take a glimpse of the place he occupies in the great history of the Universe. An unusual perspective on what it means to be a human being... This spectacle in the Globe of Science and Innovation, specially created by the Miméscope* company for the official ceremony marking CERN's fiftieth anniversary, is a gift from the Government of the Republic and Canton of Geneva, which also wishes to share this moment of wonder with the local population. There will be three performances for...

  7. "Point de suspension"

    CERN Multimedia

    2004-01-01

    CERN - Globe of Science and Innovation 20 and 21 October Acrobatics, mime, a cappella singing, projections of images, a magical setting... a host of different tools of a grandeur matching that of the Universe they relate. A camera makes a massive zoom out to reveal the multiple dimensions of Nature. Freeze the frame: half way between the infinitesimally small and the infinitesimally large, a man suspends his everyday life (hence the title "Point de Suspension", which refers to the three dots at the end of an uncompleted sentence) to take a glimpse of the place he occupies in the great history of the Universe. An unusual perspective on what it means to be a human being... This wondrous show in the Globe of Science and Innovation, specially created by the Miméscope* company for the official ceremony marking CERN's fiftieth anniversary, is a gift from the Government of the Republic and Canton of Geneva, which also wishes to share this moment of wonder with the local population. There will be three perfo...

  8. "Point de suspension"

    CERN Document Server

    2004-01-01

    http://www.cern.ch/cern50/ CERN - Globe of Science and Innovation 20 and 21 October Acrobatics, mime, a cappella singing, projections of images, a magical setting... a host of different tools of a grandeur matching that of the Universe they relate. A camera makes a massive zoom out to reveal the multiple dimensions of Nature. Freeze the frame: half way between the infinitesimally small and the infinitesimally large, a man suspends his everyday life (hence the title "Point de Suspension", which refers to the three dots at the end of an uncompleted sentence) to take a glimpse of the place he occupies in the great history of the Universe. An unusual perspective on what it means to be a human being... This wondrous show in the Globe of Science and Innovation, specially created by the Miméscope* company for the official ceremony marking CERN's fiftieth anniversary, is a gift from the Government of the Republic and Canton of Geneva, which also wishes to share this moment of wonder with the local pop...

  9. Covalent Cross-Linking of Porous Poly(ionic liquid) Membrane via a Triazine Network

    OpenAIRE

    Täuber, K.; Dani, A.; Yuan, J.

    2017-01-01

    Porous poly(ionic liquid) membranes that were prepared via electrostatic cross-linking were subsequently covalently cross-linked via formation of a 1,3,5-triazine network. The additional covalent cross-links do not affect the pore size and pore size distribution of the membranes and stabilize them towards salt solutions of high ionic strength, enabling the membranes to work in a broader environmental window.

  10. Hydrogen bonding in ionic liquids.

    Science.gov (United States)

    Hunt, Patricia A; Ashworth, Claire R; Matthews, Richard P

    2015-03-07

    Ionic liquids (IL) and hydrogen bonding (H-bonding) are two diverse fields for which there is a developing recognition of significant overlap. Doubly ionic H-bonds occur when a H-bond forms between a cation and anion, and are a key feature of ILs. Doubly ionic H-bonds represent a wide area of H-bonding which has yet to be fully recognised, characterised or explored. H-bonds in ILs (both protic and aprotic) are bifurcated and chelating, and unlike many molecular liquids a significant variety of distinct H-bonds are formed between different types and numbers of donor and acceptor sites within a given IL. Traditional more neutral H-bonds can also be formed in functionalised ILs, adding a further level of complexity. Ab initio computed parameters; association energies, partial charges, density descriptors as encompassed by the QTAIM methodology (ρBCP), qualitative molecular orbital theory and NBO analysis provide established and robust mechanisms for understanding and interpreting traditional neutral and ionic H-bonds. In this review the applicability and extension of these parameters to describe and quantify the doubly ionic H-bond has been explored. Estimating the H-bonding energy is difficult because at a fundamental level the H-bond and ionic interaction are coupled. The NBO and QTAIM methodologies, unlike the total energy, are local descriptors and therefore can be used to directly compare neutral, ionic and doubly ionic H-bonds. The charged nature of the ions influences the ionic characteristics of the H-bond and vice versa, in addition the close association of the ions leads to enhanced orbital overlap and covalent contributions. The charge on the ions raises the energy of the Ylp and lowers the energy of the X-H σ* NBOs resulting in greater charge transfer, strengthening the H-bond. Using this range of parameters and comparing doubly ionic H-bonds to more traditional neutral and ionic H-bonds it is clear that doubly ionic H-bonds cover the full range of weak

  11. Smectic phases in ionic liquid crystals.

    Science.gov (United States)

    Bartsch, Hendrik; Bier, Markus; Dietrich, S

    2017-11-22

    Ionic liquid crystals (ILCs) are anisotropic mesogenic molecules which carry charges and therefore combine properties of liquid crystals, e.g. the formation of mesophases, and of ionic liquids, such as low melting temperatures and tiny triple-point pressures. Previous density functional calculations have revealed that the phase behavior of ILCs is strongly affected by their molecular properties, i.e. their aspect ratio, the loci of the charges, and their interaction strengths. Here, we report new findings concerning the phase behavior of ILCs as obtained by density functional theory and Monte Carlo simulations. The most important result is the occurrence of a novel, wide smectic-A phase [Formula: see text], at low temperature, the layer spacing of which is larger than that of the ordinary high-temperature smectic-A phase [Formula: see text]. Unlike the ordinary smectic S A phase, the structure of the [Formula: see text] phase consists of alternating layers of particles oriented parallel to the layer normal and oriented perpendicular to it.

  12. Modeling electrokinetics in ionic liquids.

    Science.gov (United States)

    Wang, Chao; Bao, Jie; Pan, Wenxiao; Sun, Xin

    2017-07-01

    Using direct numerical simulations, we provide a thorough study regarding the electrokinetics of ionic liquids. In particular, modified Poisson-Nernst-Planck equations are solved to capture the crowding and overscreening effects characteristic of an ionic liquid. For modeling electrokinetic flows in an ionic liquid, the modified Poisson-Nernst-Planck equations are coupled with Navier-Stokes equations to study the coupling of ion transport, hydrodynamics, and electrostatic forces. Specifically, we consider the ion transport between two parallel charged surfaces, charging dynamics in a nanopore, capacitance of electric double-layer capacitors, electroosmotic flow in a nanochannel, electroconvective instability on a plane ion-selective surface, and electroconvective flow on a curved ion-selective surface. We also discuss how crowding and overscreening and their interplay affect the electrokinetic behaviors of ionic liquids in these application problems. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Ionic thermoelectric gating organic transistors

    Science.gov (United States)

    Zhao, Dan; Fabiano, Simone; Berggren, Magnus; Crispin, Xavier

    2017-01-01

    Temperature is one of the most important environmental stimuli to record and amplify. While traditional thermoelectric materials are attractive for temperature/heat flow sensing applications, their sensitivity is limited by their low Seebeck coefficient (∼100 μV K−1). Here we take advantage of the large ionic thermoelectric Seebeck coefficient found in polymer electrolytes (∼10,000 μV K−1) to introduce the concept of ionic thermoelectric gating a low-voltage organic transistor. The temperature sensing amplification of such ionic thermoelectric-gated devices is thousands of times superior to that of a single thermoelectric leg in traditional thermopiles. This suggests that ionic thermoelectric sensors offer a way to go beyond the limitations of traditional thermopiles and pyroelectric detectors. These findings pave the way for new infrared-gated electronic circuits with potential applications in photonics, thermography and electronic-skins. PMID:28139738

  14. Ionic emission from Taylor cones

    Science.gov (United States)

    Castro Reina, Sergio

    Electrified Taylor cones have been seen as an efficient way to generate thrust for space propulsion. Especially the pure ionic regime (PIR) combines a very high specific impulse (thrust per unit mass) and efficiency, which is very important to reduce fuel transportation costs. The PIR has been primarily based on electrosprays of liquid metals [Swatik and Hendricks 1968, Swatik 1969]. However, emissions dominated by or containing exclusively ions have also been observed from nonmetallic purely ionic substances, initially sulfuric acid [Perel et al. 1969], and more recently room temperature molten salts referred to as ionic liquids (ILs) [Romero-Sanz et al. 2003]. The recent use of the liquid metal ion source (LMIS) with ILs, becoming this "new" source to be known as ionic liquid ion source (ILIS) [Lozano and Martinez-Sanchez 2005], has shown important differences on the emission from Taylor cones with the traditional hollow capillary. This new source seems to be more flexible than the capillary [Paulo, Sergio, carlos], although its low emission level (low thrust) is an important drawback from the space propulsion point of view. Throughout the thesis I have studied some aspects of the ionic emission from ionic liquid Taylor cones and the influence of the properties of the liquids and the characteristic of source on the emission. I have unraveled the reason why ILIS emits such low currents (˜200 nA) and found a way to solve this problem increasing the current up to capillary levels (˜1000 nA) [Castro and Fernandez de la Mora 2009]. I have also tried to reduce ion evaporation while reducing the emitted droplet size in order to increase the thrust generated while keeping the efficiency relatively high and I have measured the energy of evaporation of several cations composing ionic liquids, mandatory step to understand ionic evaporation.

  15. Ionic Adsorption and Desorption of CNT Nanoropes

    Directory of Open Access Journals (Sweden)

    Jun-Jun Shang

    2016-09-01

    Full Text Available A nanorope is comprised of several carbon nanotubes (CNTs with different chiralities. A molecular dynamic model is built to investigate the ionic adsorption and desorption of the CNT nanoropes. The charge distribution on the nanorope is obtained by using a modified gradient method based on classical electrostatic theory. The electrostatic interactions among charged carbon atoms are calculated by using the Coulomb law. It was found here that the charged nanorope can adsorb heavy metal ions, and the adsorption and desorption can be realized by controlling the strength of applied electric field. The distance between the ions and the nanorope as well as the amount of ions have an effect on the adsorption capacity of the nanorope. The desorption process takes less time than that of adsorption. The study indicates that the CNT nanorope can be used as a core element of devices for sewage treatment.

  16. Suspension biomechanics of swimming microbes.

    Science.gov (United States)

    Ishikawa, Takuji

    2009-10-06

    Micro-organisms play a vital role in many biological, medical and engineering phenomena. Some recent research efforts have demonstrated the importance of biomechanics in understanding certain aspects of micro-organism behaviours such as locomotion and collective motions of cells. In particular, spatio-temporal coherent structures found in a bacterial suspension have been the focus of many research studies over the last few years. Recent studies have shown that macroscopic properties of a suspension, such as rheology and diffusion, are strongly affected by meso-scale flow structures generated by swimming microbes. Since the meso-scale flow structures are strongly affected by the interactions between microbes, a bottom-up strategy, i.e. from a cellular level to a continuum suspension level, represents the natural approach to the study of a suspension of swimming microbes. In this paper, we first provide a summary of existing biomechanical research on interactions between a pair of swimming micro-organisms, as a two-body interaction is the simplest many-body interaction. We show that interactions between two nearby swimming micro-organisms are described well by existing mathematical models. Then, collective motions formed by a group of swimming micro-organisms are discussed. We show that some collective motions of micro-organisms, such as coherent structures of bacterial suspensions, are satisfactorily explained by fluid dynamics. Lastly, we discuss how macroscopic suspension properties are changed by the microscopic characteristics of the cell suspension. The fundamental knowledge we present will be useful in obtaining a better understanding of the behaviour of micro-organisms.

  17. Fluctuating hydrodynamics for ionic liquids

    Energy Technology Data Exchange (ETDEWEB)

    Lazaridis, Konstantinos [Department of Mathematics and Statistics, Washington State University, Pullman, 99163 (United States); Wickham, Logan [Department of Computer Science, Washington State University, Richland, 99354 (United States); Voulgarakis, Nikolaos, E-mail: n.voulgarakis@wsu.edu [Department of Mathematics and Statistics, Washington State University, Pullman, 99163 (United States)

    2017-04-25

    We present a mean-field fluctuating hydrodynamics (FHD) method for studying the structural and transport properties of ionic liquids in bulk and near electrified surfaces. The free energy of the system consists of two competing terms: (1) a Landau–Lifshitz functional that models the spontaneous separation of the ionic groups, and (2) the standard mean-field electrostatic interaction between the ions in the liquid. The numerical approach used to solve the resulting FHD-Poisson equations is very efficient and models thermal fluctuations with remarkable accuracy. Such density fluctuations are sufficiently strong to excite the experimentally observed spontaneous formation of liquid nano-domains. Statistical analysis of our simulations provides quantitative information about the properties of ionic liquids, such as the mixing quality, stability, and the size of the nano-domains. Our model, thus, can be adequately parameterized by directly comparing our prediction with experimental measurements and all-atom simulations. Conclusively, this work can serve as a practical mathematical tool for testing various theories and designing more efficient mixtures of ionic liquids. - Highlights: • A new fluctuating hydrodynamics method for ionic liquids. • Description of ionic liquid morphology in bulk and near electrified surfaces. • Direct comparison with experimental measurements.

  18. Activity of phosphorus of synthetic Fe-K-P compounds in superphosphate fertilizers as affected by pH and ionic strength Efeito do pH e da força iônica na atividade de fósforo oriundo de compostos sinteticos do tipo Fe-K-P de superfosfatos

    Directory of Open Access Journals (Sweden)

    Luís Ignácio Prochnow

    2006-06-01

    Full Text Available The concentration of orthophosphate ions released from Fe-K-P compounds (Fe3KH8(PO46 .6H2O and Fe3KH14(PO48 .4H2O present in superphosphates increases with pH, which initially suggests that the agronomic effectiveness of P fertilizers containing high amounts of these compounds would also increase with soil pH but studies considering activity, instead of concentration, are necessary. With this purpose, both compounds were synthesized under laboratory conditions, characterized by elemental chemical analysis, optical microscopy, X ray diffractometry, scanning electron microscopy (SEM and energy dispersive spectroscopy (EDS, and used in a solubility study. Solutions of 0.01, 0.05 and 0.1 mol L-1 NaCl with pH adjusted to 3.0, 4.0, 5.0, 5.5, 6.0, 6.5, 7.0 and 7.5 were prepared for the solubility study of H8-syn, H14-syn and a phosphate rock (PR from Brazil. The orthophosphate activity as H2PO4- and HPO4(2- was calculated in each situation as related to pH and ionic strength using software MINTEQ. The remaining precipitates after equilibrium were chemically analyzed and subjected to X ray, SEM and EDS. Results of chemical analysis and instrumental techniques confirmed the preparation method. The activity of orthophosphate ions of both compounds tended to decrease under increasing pH and/or ionic strength of the solution, which in turn suggests that an increase in the solution pH does not necessarily promote an increase in the P bioavailability for plant uptake. This can be important when evaluating agronomic data of P fertilizers with high contents of these two Fe-K-P compounds.O aumento do pH da concentração de íons ortofosfatos liberados de compostos do tipo Fe-K-P (Fe3KH8(PO46 .6H2O e Fe3KH14(PO48 .4H2O, presentes em superfosfatos, evidenciam, inicialmente, que a eficiência agronômica de fertilizantes fosfatados, com elevadas quantidades destes, poderiam aumentar com o pH do solo; todavia, estudos que considerem atividades, em vez de concentra

  19. Ionic Conductivity of Polyelectrolyte Hydrogels.

    Science.gov (United States)

    Lee, Chen-Jung; Wu, Haiyan; Hu, Yang; Young, Megan; Wang, Huifeng; Lynch, Dylan; Xu, Fujian; Cong, Hongbo; Cheng, Gang

    2018-01-31

    Polyelectrolytes have many important functions in both living organisms and man-made applications. One key property of polyelectrolytes is the ionic conductivity due to their porous networks that allow the transport of water and small molecular solutes. Among polyelectrolytes, zwitterionic polymers have attracted huge attention for applications that involve ion transport in a polyelectrolyte matrix; however, it is still unclear how the functional groups of zwitterionic polymer side chains affect their ion transport and swelling properties. In this study, zwitterionic poly(carboxybetaine acrylamide), poly(2-methacryloyloxyethyl phosphorylcholine), and poly(sulfobetaine methacrylate) hydrogels were synthesized and their ionic conductivity was studied and compared to cationic, anionic, and nonionic hydrogels. The change of the ionic conductivity of zwitterionic and nonionic hydrogels in different saline solutions was investigated in detail. Zwitterionic hydrogels showed much higher ionic conductivity than that of the widely used nonionic poly(ethylene glycol) methyl ether methacrylate hydrogel in all tested solutions. For both cationic and anionic hydrogels, the presence of mobile counterions led to high ionic conductivity in low salt solutions; however, the ionic conductivity of zwitterionic hydrogels surpassed that of cationic and ionic hydrogels in high salt solutions. Cationic and anionic hydrogels showed much higher water content than that of zwitterionic hydrogels in deionized water; however, the cationic hydrogels shrank significantly with increasing saline concentration. This work provides insight into the effects of polyelectrolyte side chains on ion transport. This can guide us in choosing better polyelectrolytes for a broad spectrum of applications, including bioelectronics, neural implants, battery, and so on.

  20. Active Control of Suspension Bridges

    DEFF Research Database (Denmark)

    Thoft-Christensen, Palle

    In this paper some recent research on active control of very long suspension bridges, is presented. The presentation is based on research work at Aalborg University, Denmark. The active control system is based on movable flaps attached to the bridge girder. Wind load on bridges with or without...... flaps attached to the girder is briefly presented. A simple active control system is discussed. Results from wind tunnel experiments with a bridge section show that flaps can be used effectively to control bridge girder vibrations. Flutter conditions for suspension bridges with and without flaps...

  1. Novel ionic polymeric hydraulic actuators

    Science.gov (United States)

    Shahinpoor, Mohsen; Kim, Kwang J.

    2001-07-01

    It is now well recognized that a strip of ionic polymer- metal composite (IPMC) exhibits a spontaneous bending capability under the influence of an electric potential. A key observation is the appearance and disappearance of water on the expansion and contraction surfaces of the strip, respectively. Such water appearing/disappearing activities occur near the permeable metal electrodes. The imposition of en elctric field causes the mobile cations that are conjugated to the polymeric anions to undergo electrophoretic dynamic migration that can result in local deformation of the material. Such an electrophoretic behavior of the IPMC causes the water to leak out of the permeable electroded boundary so as to lower the actuation performance. This situation is similar to a leaking hydraulic actuator (hydraulic jack), which has the highest force density notwithstanding the compressor unit weight. Herein, a new category of actuators as ionic polymeric hydraulic actuators (IPHA's) is defined. The IPMC is a good example of such ionic polymeric hydraulic actuators. The advantage of ionic polymeric hydraulic actuators is their potential to generate substantially high force densities, theoretically better than current hydraulic actuators. Based upon this ionic polymer hydraulic actuator concept, a certain manufacturing technique was developed to increase the force density of the conventional IPMC's by a factor of two (100% improvement in force). This technology and associated experimental results are presented in this paper.

  2. Characterizing Fullerene Nanoparticles in Aqueous Suspensions

    Science.gov (United States)

    Studies have indicated that fullerenes can form stable colloidal suspensions in water when introduced to the aqueous phase through solvent exchange, sonication, or extended mixing. The colloidal suspensions created using these techniques have effective aqueous phase concentratio...

  3. Heavy vehicle pitch dynamics and suspension tuning

    OpenAIRE

    Cao, Dongpu; Rakheja, Subhash; Su, Chun-Yi

    2008-01-01

    The influence of suspension tuning of passenger cars on bounce and pitch ride performance has been explored in a number of studies, while only minimal efforts have been made for establishing similar rules for heavy vehicles. This study aims to explore pitch dynamics and suspension tunings of a two-axle heavy vehicle with unconnected suspension, which could also provide valuable information for heavy vehicles with coupled suspensions. Based on a generalised pitch-plane model of a two-axle heav...

  4. Sensitivity of nanostructure in charged cubosomes to phase changes triggered by ionic species in solution.

    Science.gov (United States)

    Liu, Qingtao; Dong, Yao-Da; Hanley, Tracey L; Boyd, Ben J

    2013-11-19

    The phase behavior of dispersions comprising mixed ionic surfactant and phytantriol was precisely controlled by varying the ionic surfactant content in the mixed lipid and the ionic strength in the system. Two important trends in the phase transition of the mixed lipid systems were identified: (1) An increase in the ionic surfactant content increased the curvature of the self-assembled system toward the hydrophobic region, resulting in the phase transition from cubic phase to lamellar phase. (2) An increase in ionic strength decreased repulsion between the headgroups of the ionic surfactant, resulting in a phase transition from lamellar phase to cubic phase. The phase transitions were confirmed using small-angle X-ray scattering and cryo-TEM and were strongly correlated with the visual turbidity of the dispersions. The lipid mixture with anionic surfactant showed high sensitivity to multivalent cations for triggering the phase transition, which may be a potential strategy to develop a detection/treatment system for toxic multivalent metallic cations such as chromium.

  5. Muscle sarcomere lesions and thrombosis after spaceflight and suspension unloading

    Energy Technology Data Exchange (ETDEWEB)

    Riley, D.A.; Ellis, S.; Giometti, C.S.; Hoh, J.F.Y.; Ilyina-Kakueva, E.I.; Oganov, V.S.; Slocum, G.R.; Bain, J.L.W.; Sedlak, F.R. (Argonne National Lab., IL (United States))

    1992-08-01

    Extended exposure of humans to spaceflight produces a progressive loss of skeletal muscle strength. This process must be understood to design effective countermeasures. The present investigation examined hindlimb muscles from flight rats killed as close to landing as possible. Spaceflight and tail suspension-hindlimb unloading (unloaded) produced significant decreases in fiber cross-sectional areas of the adductor longus (AL), a slow-twitch antigravity muscle. However, the mean wet weight of the flight AL muscles was near normal, whereas that of the suspension unloaded AL muscles was significantly reduced. Interstitial edema within the flight AL, but not in the unloaded AL, appeared to account for this apparent disagreement.In both conditions, the slow-twitch oxidative fibers atrophied more than the fast-twitch oxidative-glycolytic fibers. Microcirculation was also compromised by spaceflight, such that there was increased formation of thrombi in the postcapillary venules and capillaries.

  6. Highly stable noble-metal nanoparticles in tetraalkylphosphonium ionic liquids for in situ catalysis.

    Science.gov (United States)

    Banerjee, Abhinandan; Theron, Robin; Scott, Robert W J

    2012-01-09

    Gold and palladium nanoparticles were prepared by lithium borohydride reduction of the metal salt precursors in tetraalkylphosphonium halide ionic liquids in the absence of any organic solvents or external nanoparticle stabilizers. These colloidal suspensions remained stable and showed no nanoparticle agglomeration over many months. A combination of electrostatic interactions between the coordinatively unsaturated metal nanoparticle surface and the ionic-liquid anions, bolstered by steric protection offered by the bulky alkylated phosphonium cations, is likely to be the reason behind such stabilization. The halide anion strongly absorbs to the nanoparticle surface, leading to exceptional nanoparticle stability in halide ionic liquids; other tetraalkylphosphonium ionic liquids with non-coordinating anions, such as tosylate and hexafluorophosphate, show considerably lower affinities towards the stabilization of nanoparticles. Palladium nanoparticles stabilized in the tetraalkylphosphonium halide ionic liquid were stable, efficient, and recyclable catalysts for a variety of hydrogenation reactions at ambient pressures with sustained activity. Aerial oxidation of the metal nanoparticles occurred over time and was readily reversed by re-reduction of oxidized metal salts. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Mass-imbalanced ionic Hubbard chain

    Science.gov (United States)

    Sekania, Michael; Baeriswyl, Dionys; Jibuti, Luka; Japaridze, George I.

    2017-07-01

    A repulsive Hubbard model with both spin-asymmetric hopping (t↑≠t↓ ) and a staggered potential (of strength Δ ) is studied in one dimension. The model is a compound of the mass-imbalanced (t↑≠t↓ ,Δ =0 ) and ionic (t↑=t↓ ,Δ >0 ) Hubbard models, and may be realized by cold atoms in engineered optical lattices. We use mostly mean-field theory to determine the phases and phase transitions in the ground state for a half-filled band (one particle per site). We find that a period-two modulation of the particle (or charge) density and an alternating spin density coexist for arbitrary Hubbard interaction strength, U ≥0 . The amplitude of the charge modulation is largest at U =0 , decreases with increasing U and tends to zero for U →∞ . The amplitude for spin alternation increases with U and tends to saturation for U →∞ . Charge order dominates below a value Uc, whereas magnetic order dominates above. The mean-field Hamiltonian has two gap parameters, Δ↑ and Δ↓, which have to be determined self-consistently. For U Uc they have different signs, and for U =Uc one gap parameter jumps from a positive to a negative value. The weakly first-order phase transition at Uc can be interpreted in terms of an avoided criticality (or metallicity). The system is reluctant to restore a symmetry that has been broken explicitly.

  8. Suspension-Firing of Biomass

    DEFF Research Database (Denmark)

    Shafique Bashir, Muhammad; Jensen, Peter Arendt; Frandsen, Flemming

    2012-01-01

    This paper is the second of two papers, describing probe measurements of deposit buildup and removal (shedding), conducted in a 350 MWth suspension-fired boiler, firing straw and wood. Investigations of deposit buildup and shedding have been made by use of an advanced online deposit probe and a s...

  9. Rotational diffusion in dense suspensions

    NARCIS (Netherlands)

    Hagen, M. H. J.; Frenkel, D.; Lowe, C.P.

    1999-01-01

    We have computed the rotational diffusion coefficient for a suspension of hard spheres. We find excellent agreement with experimental results over a density range up to, and including, the colloidal crystal. However, we find that theories derived to second order in the volume fraction overestimate

  10. Transmission function of pneumatic suspension

    OpenAIRE

    Turenko, A.; Bogomolov, V.; Klimenko, V.; Shilov, A.

    2006-01-01

    The transmission function of pneumatic suspension at assumption, that walls of pneumatic elastic element is absolute not stretched; the rubber buffers of compression and of retreat are absent; description of shock absorber is linear and symmetric; the processes of compression and expansion of air are adiabatic; motion of the oscillating system carry out without separation of wheel from a road is received.

  11. 49 CFR 570.61 - Suspension system.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 6 2010-10-01 2010-10-01 false Suspension system. 570.61 Section 570.61 Transportation Other Regulations Relating to Transportation (Continued) NATIONAL HIGHWAY TRAFFIC SAFETY... 10,000 Pounds § 570.61 Suspension system. (a) Suspension condition. Ball joint seals shall not be cut...

  12. 49 CFR 570.8 - Suspension systems.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 6 2010-10-01 2010-10-01 false Suspension systems. 570.8 Section 570.8 Transportation Other Regulations Relating to Transportation (Continued) NATIONAL HIGHWAY TRAFFIC SAFETY... Pounds or Less § 570.8 Suspension systems. (a) Suspension condition. Ball joint seals shall not be cut or...

  13. 49 CFR 393.207 - Suspension systems.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 5 2010-10-01 2010-10-01 false Suspension systems. 393.207 Section 393.207... NECESSARY FOR SAFE OPERATION Frames, Cab and Body Components, Wheels, Steering, and Suspension Systems § 393.207 Suspension systems. (a) Axles. No axle positioning part shall be cracked, broken, loose or missing...

  14. 45 CFR 1210.3-3 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 45 Public Welfare 4 2010-10-01 2010-10-01 false Suspension. 1210.3-3 Section 1210.3-3 Public... § 1210.3-3 Suspension. (a) The ACTION State Director may suspend a Volunteer for up to 30 days in order... Volunteer. Suspension is not warranted if the State Director determines that sufficient grounds already...

  15. 48 CFR 2509.407 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 48 Federal Acquisition Regulations System 6 2010-10-01 2010-10-01 true Suspension. 2509.407 Section 2509.407 Federal Acquisition Regulations System NATIONAL SCIENCE FOUNDATION ACQUISITION PLANNING CONTRACTOR QUALIFICATIONS Debarment, Suspension, and Ineligibility 2509.407 Suspension. ...

  16. 32 CFR 26.670 - Suspension.

    Science.gov (United States)

    2010-07-01

    ... 32 National Defense 1 2010-07-01 2010-07-01 false Suspension. 26.670 Section 26.670 National... GOVERNMENTWIDE REQUIREMENTS FOR DRUG-FREE WORKPLACE (FINANCIAL ASSISTANCE) Definitions § 26.670 Suspension. Suspension means an action taken by a Federal agency that immediately prohibits a recipient from...

  17. 41 CFR 105-74.670 - Suspension.

    Science.gov (United States)

    2010-07-01

    ... 41 Public Contracts and Property Management 3 2010-07-01 2010-07-01 false Suspension. 105-74.670...-GOVERNMENTWIDE REQUIREMENTS FOR DRUG-FREE WORKPLACE (FINANCIAL ASSISTANCE) Definitions § 105-74.670 Suspension. Suspension means an action taken by a Federal agency that immediately prohibits a recipient from...

  18. 48 CFR 609.407 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 48 Federal Acquisition Regulations System 4 2010-10-01 2010-10-01 false Suspension. 609.407 Section 609.407 Federal Acquisition Regulations System DEPARTMENT OF STATE COMPETITION AND ACQUISITION PLANNING CONTRACTOR QUALIFICATIONS Debarment, Suspension, and Ineligibility 609.407 Suspension. ...

  19. 25 CFR 558.5 - License suspension.

    Science.gov (United States)

    2010-04-01

    ... 25 Indians 2 2010-04-01 2010-04-01 false License suspension. 558.5 Section 558.5 Indians NATIONAL... MANAGEMENT OFFICIALS § 558.5 License suspension. (a) If, after the issuance of a gaming license, the... tribe shall suspend such license and shall notify in writing the licensee of the suspension and the...

  20. 48 CFR 1309.407 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 48 Federal Acquisition Regulations System 5 2010-10-01 2010-10-01 false Suspension. 1309.407 Section 1309.407 Federal Acquisition Regulations System DEPARTMENT OF COMMERCE COMPETITION AND ACQUISITION PLANNING CONTRACTOR QUALIFICATIONS Debarment, Suspension, and Ineligibility 1309.407 Suspension. ...

  1. 36 CFR 1212.670 - Suspension.

    Science.gov (United States)

    2010-07-01

    ... 36 Parks, Forests, and Public Property 3 2010-07-01 2010-07-01 false Suspension. 1212.670 Section... GOVERNMENTWIDE REQUIREMENTS FOR DRUG-FREE WORKPLACE (FINANCIAL ASSISTANCE) Definitions § 1212.670 Suspension. Suspension means an action taken by a Federal agency that immediately prohibits a recipient from...

  2. 25 CFR 23.52 - Grant suspension.

    Science.gov (United States)

    2010-04-01

    ... 25 Indians 1 2010-04-01 2010-04-01 false Grant suspension. 23.52 Section 23.52 Indians BUREAU OF... Grant Administration Provisions and Requirements § 23.52 Grant suspension. (a) When a grantee has... assistance, suspend the grant. The notice preceding the suspension shall include the effective date of the...

  3. 22 CFR 34.20 - Suspension.

    Science.gov (United States)

    2010-04-01

    ... 22 Foreign Relations 1 2010-04-01 2010-04-01 false Suspension. 34.20 Section 34.20 Foreign Relations DEPARTMENT OF STATE CLAIMS AND STOLEN PROPERTY DEBT COLLECTION Collection Adjustments § 34.20 Suspension. The suspension of collection action shall be made in accordance with the standards set forth in...

  4. 32 CFR 552.80 - Suspension period.

    Science.gov (United States)

    2010-07-01

    ... 32 National Defense 3 2010-07-01 2010-07-01 true Suspension period. 552.80 Section 552.80 National... Suspension period. All solicitation privileges suspended by installation commanders will be for a specific time. Normally, it will not exceed 2 years. When the suspension period expires, the agent may reapply...

  5. 48 CFR 509.407 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 48 Federal Acquisition Regulations System 4 2010-10-01 2010-10-01 false Suspension. 509.407 Section 509.407 Federal Acquisition Regulations System GENERAL SERVICES ADMINISTRATION COMPETITION AND ACQUISITION PLANNING CONTRACTOR QUALIFICATIONS Debarment, Suspension, and Ineligibility 509.407 Suspension. ...

  6. 7 CFR 3015.123 - Suspension.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 15 2010-01-01 2010-01-01 false Suspension. 3015.123 Section 3015.123 Agriculture... AGRICULTURE UNIFORM FEDERAL ASSISTANCE REGULATIONS Grant and Subgrant Closeout, Suspension and Termination § 3015.123 Suspension. (a) When a recipient has materially failed to comply with the provisions...

  7. 21 CFR 520.1806 - Piperazine suspension.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Piperazine suspension. 520.1806 Section 520.1806... DRUGS, FEEDS, AND RELATED PRODUCTS ORAL DOSAGE FORM NEW ANIMAL DRUGS § 520.1806 Piperazine suspension. (a) Specifications. Each milliliter of suspension contains piperazine monohydrochloride equivalent to...

  8. 48 CFR 9.407 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 48 Federal Acquisition Regulations System 1 2010-10-01 2010-10-01 false Suspension. 9.407 Section 9.407 Federal Acquisition Regulations System FEDERAL ACQUISITION REGULATION ACQUISITION PLANNING CONTRACTOR QUALIFICATIONS Debarment, Suspension, and Ineligibility 9.407 Suspension. ...

  9. 48 CFR 909.407 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 48 Federal Acquisition Regulations System 5 2010-10-01 2010-10-01 false Suspension. 909.407 Section 909.407 Federal Acquisition Regulations System DEPARTMENT OF ENERGY COMPETITION ACQUISITION PLANNING CONTRACTOR QUALIFICATIONS Debarment, Suspension, and Ineligibility 909.407 Suspension. ...

  10. 48 CFR 809.407 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 48 Federal Acquisition Regulations System 5 2010-10-01 2010-10-01 false Suspension. 809.407 Section 809.407 Federal Acquisition Regulations System DEPARTMENT OF VETERANS AFFAIRS COMPETITION AND ACQUISITION PLANNING CONTRACTOR QUALIFICATIONS Debarment, Suspension, and Ineligibility 809.407 Suspension. ...

  11. 48 CFR 1509.407 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 48 Federal Acquisition Regulations System 6 2010-10-01 2010-10-01 true Suspension. 1509.407 Section 1509.407 Federal Acquisition Regulations System ENVIRONMENTAL PROTECTION AGENCY ACQUISITION PLANNING CONTRACTOR QUALIFICATIONS Debarment, Suspension and Ineligibility 1509.407 Suspension. ...

  12. 21 CFR 522.1289 - Lufenuron suspension.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Lufenuron suspension. 522.1289 Section 522.1289 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Lufenuron suspension. (a) Specifications. Each milliliter of sterile aqueous suspension contains 10...

  13. 32 CFR 776.82 - Interim suspension.

    Science.gov (United States)

    2010-07-01

    ... 32 National Defense 5 2010-07-01 2010-07-01 false Interim suspension. 776.82 Section 776.82... Complaint Processing Procedures § 776.82 Interim suspension. (a) Where the Rules Counsel determines there is... interim suspension, pending completion of a professional responsibility investigation. The covered...

  14. 48 CFR 409.407 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 48 Federal Acquisition Regulations System 4 2010-10-01 2010-10-01 false Suspension. 409.407 Section 409.407 Federal Acquisition Regulations System DEPARTMENT OF AGRICULTURE COMPETITION AND ACQUISITION PLANNING CONTRACTOR QUALIFICATIONS Debarment, Suspension and Ineligibility 409.407 Suspension. ...

  15. 48 CFR 2009.407 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 48 Federal Acquisition Regulations System 6 2010-10-01 2010-10-01 true Suspension. 2009.407 Section 2009.407 Federal Acquisition Regulations System NUCLEAR REGULATORY COMMISSION COMPETITION AND ACQUISITION PLANNING CONTRACTOR QUALIFICATIONS Debarment, Suspension, and Ineligibility 2009.407 Suspension. ...

  16. 75 FR 24494 - Nonprocurement Debarment and Suspension

    Science.gov (United States)

    2010-05-05

    ...; ] ELECTION ASSISTANCE COMMISSION 2 CFR Chapter 58 Nonprocurement Debarment and Suspension AGENCY: U.S... proposed debarment and suspension regulations. These proposed regulations will apply to nonprocurement... Management and Budget (OMB) in a document on nonprocurement debarment and suspension published in the Federal...

  17. 21 CFR 520.1630 - Oxfendazole suspension.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Oxfendazole suspension. 520.1630 Section 520.1630... DRUGS, FEEDS, AND RELATED PRODUCTS ORAL DOSAGE FORM NEW ANIMAL DRUGS § 520.1630 Oxfendazole suspension. (a) Specifications. Each milliliter of suspension contains: (1) 90.6 milligrams (mg) oxfendazole (9...

  18. 32 CFR 552.79 - Suspension action.

    Science.gov (United States)

    2010-07-01

    ... 32 National Defense 3 2010-07-01 2010-07-01 true Suspension action. 552.79 Section 552.79 National... Suspension action. (a) When suspended for cause, immediately notify the company and the agent, in writing, of the reason. When the installation commander determines that suspension should be extended throughout...

  19. 36 CFR 223.141 - Suspension.

    Science.gov (United States)

    2010-07-01

    ... 36 Parks, Forests, and Public Property 2 2010-07-01 2010-07-01 false Suspension. 223.141 Section... DISPOSAL OF NATIONAL FOREST SYSTEM TIMBER Suspension and Debarment of Timber Purchasers § 223.141 Suspension. (a) The suspending official may, in the public interest, suspend a purchaser on the basis of...

  20. 22 CFR 127.8 - Interim suspension.

    Science.gov (United States)

    2010-04-01

    ... 22 Foreign Relations 1 2010-04-01 2010-04-01 false Interim suspension. 127.8 Section 127.8 Foreign... Interim suspension. (a) The Managing Director of the Directorate of Defense Trade Controls or the Director of the Office of Defense Trade Controls Compliance is authorized to order the interim suspension of...

  1. 38 CFR 48.670 - Suspension.

    Science.gov (United States)

    2010-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 2 2010-07-01 2010-07-01 false Suspension. 48.670...) GOVERNMENTWIDE REQUIREMENTS FOR DRUG-FREE WORKPLACE (FINANCIAL ASSISTANCE) Definitions § 48.670 Suspension. Suspension means an action taken by a Federal agency that immediately prohibits a recipient from...

  2. 48 CFR 309.407 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 48 Federal Acquisition Regulations System 4 2010-10-01 2010-10-01 false Suspension. 309.407 Section 309.407 Federal Acquisition Regulations System HEALTH AND HUMAN SERVICES COMPETITION AND ACQUISITION PLANNING CONTRACTOR QUALIFICATIONS Debarment, Suspension, and Ineligibility 309.407 Suspension. ...

  3. 48 CFR 1409.407 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 48 Federal Acquisition Regulations System 5 2010-10-01 2010-10-01 false Suspension. 1409.407 Section 1409.407 Federal Acquisition Regulations System DEPARTMENT OF THE INTERIOR COMPETITION AND ACQUISITION PLANNING CONTRACTOR QUALIFICATIONS Debarment, Suspension, and Ineligibility 1409.407 Suspension. ...

  4. Effect of surfactants on mechanical strength of polyacrylamide hydrogels: A rheological study

    Science.gov (United States)

    Khandai, Santripti; Mithra, K.; Jena, Sidhartha S.

    2017-05-01

    We have investigated the effect of ionic and non - ionic surfactants on the structure and rheological properties of polyacrylamide hydrogels. With addition of ionic and non-ionic surfactants, just below and above their critical micellar concentration (CMC), there is a significant decrease in hydrogels mechanical strength as compared to the parent hydrogels alone. In oscillatory measurements, no frequency dependence is observed in the case of polyacrylamide hydrogels. However with the addition of surfactants, just below and above CMC, noticeable frequency dependence is observed.

  5. Lithium ion conducting ionic electrolytes

    Science.gov (United States)

    Angell, C. Austen; Xu, Kang; Liu, Changle

    1996-01-01

    A liquid, predominantly lithium-conducting, ionic electrolyte is described which has exceptionally high conductivity at temperatures of 100.degree. C. or lower, including room temperature. It comprises molten lithium salts or salt mixtures in which a small amount of an anionic polymer lithium salt is dissolved to stabilize the liquid against recrystallization. Further, a liquid ionic electrolyte which has been rubberized by addition of an extra proportion of anionic polymer, and which has good chemical and electrochemical stability, is described. This presents an attractive alternative to conventional salt-in-polymer electrolytes which are not cationic conductors.

  6. Lithium ion conducting ionic electrolytes

    Science.gov (United States)

    Angell, C.A.; Xu, K.; Liu, C.

    1996-01-16

    A liquid, predominantly lithium-conducting, ionic electrolyte is described which has exceptionally high conductivity at temperatures of 100 C or lower, including room temperature. It comprises molten lithium salts or salt mixtures in which a small amount of an anionic polymer lithium salt is dissolved to stabilize the liquid against recrystallization. Further, a liquid ionic electrolyte which has been rubberized by addition of an extra proportion of anionic polymer, and which has good chemical and electrochemical stability, is described. This presents an attractive alternative to conventional salt-in-polymer electrolytes which are not cationic conductors. 4 figs.

  7. The Properties of HPMC:PEO Extended Release Hydrophilic Matrices and their Response to Ionic Environments.

    Science.gov (United States)

    Hu, Anran; Chen, Chen; Mantle, Michael D; Wolf, Bettina; Gladden, Lynn F; Rajabi-Siahboomi, Ali; Missaghi, Shahrzad; Mason, Laura; Melia, Colin D

    2017-05-01

    Investigate the extended release behaviour of compacts containing mixtures of hydrophilic HPMC and PEO in hydrating media of differing ionic strengths. The extended release behaviour of various HPMC:PEO compacts was investigated using dissolution testing, confocal microscopy and magnetic resonance imaging, with respect to polymer ratio and ionic strength of the hydrating media. Increasing HPMC content gave longer extended release times, but a greater sensitivity to high ionic dissolution environments. Increasing PEO content reduced this sensitivity. The addition of PEO to a predominantly HPMC matrix reduced release rate sensitivity to high ionic environments. Confocal microscopy of early gel layer development showed the two polymers appeared to contribute independently to gel layer structure whilst together forming a coherent and effective diffusion barrier. There was some evidence that poorly swollen HPMC particles added a tortuosity barrier to the gel layer in high ionic strength environments, resulting in prolonged extended release. MRI provides unique, non-invasive spatially resolved information from within the HPMC:PEO compacts that furthers our understanding of USP 1 and USP 4 dissolution data. Confocal microscopy and MRI data show that combinations of HPMC and PEO have advantageous extended release properties, in comparison with matrices containing a single polymer.

  8. Surface tension of ionic liquids and ionic liquid solutions.

    Science.gov (United States)

    Tariq, Mohammad; Freire, Mara G; Saramago, Benilde; Coutinho, João A P; Lopes, José N Canongia; Rebelo, Luís Paulo N

    2012-01-21

    Some of the most active scientific research fronts of the past decade are centered on ionic liquids. These fluids present characteristic surface behavior and distinctive trends of their surface tension versus temperature. One way to explore and understand their unique nature is to study their surface properties. This critical review analyses most of the surface tension data reported between 2001 and 2010 (187 references).

  9. Ionic liquid-tolerant cellulase enzymes

    Energy Technology Data Exchange (ETDEWEB)

    Gladden, John; Park, Joshua; Singer, Steven; Simmons, Blake; Sale, Ken

    2017-10-31

    The present invention provides ionic liquid-tolerant cellulases and method of producing and using such cellulases. The cellulases of the invention are useful in saccharification reactions using ionic liquid treated biomass.

  10. Composite Electrolytes for Lithium Batteries: Ionic Liquids in APTES Crosslinked Polymers

    Science.gov (United States)

    Tigelaar, Dean M.; Meador, Mary Ann B.; Bennett, William R.

    2007-01-01

    Solvent free polymer electrolytes were made consisting of Li(+) and pyrrolidinium salts of trifluoromethanesulfonimide added to a series of hyperbranched poly(ethylene oxide)s (PEO). The polymers were connected by triazine linkages and crosslinked by a sol-gel process to provide mechanical strength. The connecting PEO groups were varied to help understand the effects of polymer structure on electrolyte conductivity in the presence of ionic liquids. Polymers were also made that contain poly(dimethylsiloxane) groups, which provide increased flexibility without interacting with lithium ions. When large amounts of ionic liquid are added, there is little dependence of conductivity on the polymer structure. However, when smaller amounts of ionic liquid are added, the inherent conductivity of the polymer becomes a factor. These electrolytes are more conductive than those made with high molecular weight PEO imbibed with ionic liquids at ambient temperatures, due to the amorphous nature of the polymer.

  11. Role of the Ionic Potential in High Harmonic Generation

    CERN Document Server

    Shafir, D; Higuet, J; Soifer, H; Dagan, M; Descamps, D; Mevel, E; Petit, S; Worner, H J; Pons, B; Dudovich, N; Mairesse, Y

    2013-01-01

    Recollision processes provide direct insight into the structure and dynamics of electronic wave functions. However, the strength of the process sets its basic limitations - the interaction couples numerous degrees of freedom. In this Letter we decouple the basic steps of the process and resolve the role of the ionic potential which is at the heart of a broad range of strong field phenomena. Specifically, we measure high harmonic generation from argon atoms. By manipulating the polarization of the laser field we resolve the vectorial properties of the interaction. Our study shows that the ionic core plays a significant role in all steps of the interaction. In particular, Coulomb focusing induces an angular deflection of the electrons before recombination. A complete spatiospectral analysis reveals the influence of the potential on the spatiotemporal properties of the emitted light.

  12. Nanoparticle enhanced ionic liquid heat transfer fluids

    Science.gov (United States)

    Fox, Elise B.; Visser, Ann E.; Bridges, Nicholas J.; Gray, Joshua R.; Garcia-Diaz, Brenda L.

    2014-08-12

    A heat transfer fluid created from nanoparticles that are dispersed into an ionic liquid is provided. Small volumes of nanoparticles are created from e.g., metals or metal oxides and/or alloys of such materials are dispersed into ionic liquids to create a heat transfer fluid. The nanoparticles can be dispersed directly into the ionic liquid during nanoparticle formation or the nanoparticles can be formed and then, in a subsequent step, dispersed into the ionic liquid using e.g., agitation.

  13. Study on epoxy resin modified by polyether ionic liquid

    Science.gov (United States)

    Jin, X. C.; Guo, L. Y.; Deng, L. L.; Wu, H.

    2017-06-01

    Chloride 1-carboxyl polyether-3-methyl imidazole ionic liquid (PIIL) was synthesized. Then blended with epoxy resin(EP) to prepare the composite materials of PIIL/EP, which cured with aniline curing agent. The structure and curing performance of PIIL/EP were determined by FT-IR and DSC. The effects of the content of PIIL on strength of EP were studied. The results show that the PIIL was the target product. The strength was improved significantly with increase of the PIIL content. The obvious rubber elasticity of PIIL/EP after cured was showed when the content of PIIL accounts for 40% and the impact strength was up to 15.95kJ/m2.

  14. Suspensions with reduced violin string modes

    Energy Technology Data Exchange (ETDEWEB)

    Lee, B H; Ju, L; Blair, D G [School of Physics, University of Western Australia, Crawley 6009, WA (Australia)

    2006-03-02

    We discuss the possibility of significantly reducing the number and Q-factor of violin string modes in the mirror suspension. Simulations of a bar-flexure suspension and an orthogonal ribbon have shown a reduction in the number of violin string modes when compared to a normal ribbon suspension. By calculating the expected suspension thermal noise, we find that the orthogonal ribbon provides a promising suspension alternative. A lower number of violin modes oscillating in the direction of the laser and a reduction in violin mode peak values of at least 23dB can be achieved with a slight increase in thermal noise above 40Hz.

  15. Ionic-Liquid-Tethered Nanoparticles: Hybrid Electrolytes

    KAUST Repository

    Moganty, Surya S.

    2010-10-22

    A new class of solventless electrolytes was created by tethering ionic liquids to hard inorganic ZrO2 nanostructures (see picture; NIM=nanoscale ionic material). These hybrid fluids exhibit exceptional redox stability windows, excellent thermal stability, good lithium transference numbers, long-term interfacial stability in the presence of a lithium anode and, when doped with lithium salt, reasonable ionic conductivities.

  16. High-flux ionic diodes, ionic transistors and ionic amplifiers based on external ion concentration polarization by an ion exchange membrane: a new scalable ionic circuit platform.

    Science.gov (United States)

    Sun, Gongchen; Senapati, Satyajyoti; Chang, Hsueh-Chia

    2016-04-07

    A microfluidic ion exchange membrane hybrid chip is fabricated using polymer-based, lithography-free methods to achieve ionic diode, transistor and amplifier functionalities with the same four-terminal design. The high ionic flux (>100 μA) feature of the chip can enable a scalable integrated ionic circuit platform for micro-total-analytical systems.

  17. High-flux ionic diodes, ionic transistors and ionic amplifiers based on external ion concentration polarization by an ion exchange membrane: a new scalable ionic circuit platform†

    Science.gov (United States)

    Sun, Gongchen; Senapati, Satyajyoti

    2016-01-01

    A microfluidic-ion exchange membrane hybrid chip is fabricated by polymer-based, lithography-free methods to achieve ionic diode, transistor and amplifier functionalities with the same four-terminal design. The high ionic flux (> 100 μA) feature of the chip can enable a scalable integrated ionic circuit platform for micro-total-analytical systems. PMID:26960551

  18. Dielectric elastomers, with very high dielectric permittivity, based on silicone and ionic interpenetrating networks

    DEFF Research Database (Denmark)

    Yu, Liyun; Madsen, Frederikke Bahrt; Hvilsted, Søren

    2015-01-01

    permittivity and the Young's modulus of the elastomer. One system that potentially achieves this involves interpenetrating polymer networks (IPNs), based on commercial silicone elastomers and ionic networks from amino- and carboxylic acid-functional silicones. The applicability of these materials as DEs...... is demonstrated herein, and a number of many and important parameters, such as dielectric permittivity/loss, viscoelastic properties and dielectric breakdown strength, are investigated. Ionic and silicone elastomer IPNs are promising prospects for dielectric elastomer actuators, since very high permittivities...... are obtained while dielectric breakdown strength and Young's modulus are not compromised. These good overall properties stem from the softening effect and very high permittivity of ionic networks – as high as ε′ = 7500 at 0.1 Hz – while the silicone elastomer part of the IPN provides mechanical integrity...

  19. Lipid processing in ionic liquids

    DEFF Research Database (Denmark)

    Lue, Bena-Marie; Guo, Zheng; Xu, Xuebing

    2007-01-01

    Ionic liquids (ILs) have been touted as “green” alternatives to traditional molecular solvents and have many unique properties which make them extremely desirable substitutes. Among their most attractive properties are their lack of vapour pressure, broad liquid range, strong solvating power...

  20. Catalysis in Molten Ionic Media

    DEFF Research Database (Denmark)

    Boghosian, Soghomon; Fehrmann, Rasmus

    2013-01-01

    This chapter deals with catalysis in molten salts and ionic liquids, which are introduced and reviewed briefly, while an in-depth review of the oxidation catalyst used for the manufacturing of sulfuric acid and cleaning of flue gas from electrical power plants is the main topic of the chapter...

  1. Retarded ionic motion in flourites

    NARCIS (Netherlands)

    Schoonman, J.

    Metals halides with the fluorite structure attain conductivity values typical of ionic melts far below their melting points, and also go through a second-order transition. Conductivity data for the fluorites are reviewed, and it is shown that the anion vacancies have a large and unique mobility

  2. Effective viscosity of actively swimming algae suspensions

    Science.gov (United States)

    Ewoldt, Randy; Caretta, Lucas; Chengala, Anwar; Sheng, Jian

    2010-11-01

    Suspensions of actively swimming microorganisms exhibit an effective viscosity which may depend on volume fraction, cell shape, and the nature of locomotion (e.g. "pushers" vs. "pullers"). Here we report experimental measurements of shear viscosity for suspensions of unicellular green algae (Dunaliella primolecta, a biflagellated "puller"). We use a cone-and-plate rheometer to measure the dynamic shear viscosity for both motile and non-motile suspensions of D. primolecta. Viscosity increases with concentration for both cases, but the active suspensions of "pullers" have a comparatively lower effective viscosity than passive suspensions. This observation contrasts recently proposed theories which predict that "pullers" should instead have a higher viscosity than non-motile suspensions. Additionally, we observe shear-induced migration of active suspensions and consider its impact on the resulting effective shear viscosity.

  3. Modeling of solubility of CO2 in 1-butylpyridinium bis(trifluoromethylsulfonyl)imide ionic liquid using UNIFAC

    Science.gov (United States)

    Yunus, Normawati M.; Abdul Mutalib, M. I.; Murugesan, T.

    2012-09-01

    The solubility of CO2 in 1-butylpyridinium bis(trifluoromethylsulfonyl)imide [C4py][Tf2N] ionic liquid has been determined using Magnetic Suspension Balance instrument at 298.15 K and in the pressures up to about 27 bar. A group contribution method, namely UNIFAC has been used to fit the experimental data. The interaction parameters of the model were estimated. The predicted CO2 solubility data by the model shows good agreement with the experimental data.

  4. Application of ionic liquids in hydrometallurgy.

    Science.gov (United States)

    Park, Jesik; Jung, Yeojin; Kusumah, Priyandi; Lee, Jinyoung; Kwon, Kyungjung; Lee, Churl Kyoung

    2014-08-29

    Ionic liquids, low temperature molten salts, have various advantages manifesting themselves as durable and environmentally friendly solvents. Their application is expanding into various fields including hydrometallurgy due to their unique properties such as non-volatility, inflammability, low toxicity, good ionic conductivity, and wide electrochemical potential window. This paper reviews previous literatures and our recent results adopting ionic liquids in extraction, synthesis and processing of metals with an emphasis on the electrolysis of active/light, rare earth, and platinum group metals. Because the research and development of ionic liquids in this area are still emerging, various, more fundamental approaches are expected to popularize ionic liquids in the metal manufacturing industry.

  5. Electric Field-Responsive Mesoporous Suspensions: A Review

    Directory of Open Access Journals (Sweden)

    Seung Hyuk Kwon

    2015-12-01

    Full Text Available This paper briefly reviews the fabrication and electrorheological (ER characteristics of mesoporous materials and their nanocomposites with conducting polymers under an applied electric field when dispersed in an insulating liquid. Smart fluids of electrically-polarizable particles exhibit a reversible and tunable phase transition from a liquid-like to solid-like state in response to an external electric field of various strengths, and have potential applications in a variety of active control systems. The ER properties of these mesoporous suspensions are explained further according to their dielectric spectra in terms of the flow curve, dynamic moduli, and yield stress.

  6. Particle Suspension Mechanisms - Supplemental Material

    Energy Technology Data Exchange (ETDEWEB)

    Dillon, M B

    2011-03-03

    This supplemental material provides a brief introduction to particle suspension mechanisms that cause exfoliated skin cells to become and remain airborne. The material presented here provides additional context to the primary manuscript and serves as background for designing possible future studies to assess the impact of skin cells as a source of infectious aerosols. This introduction is not intended to be comprehensive and interested readers are encouraged to consult the references cited.

  7. Dynamics of magnetic nanoparticle suspensions

    OpenAIRE

    Singh, Vanchna; Banerjee, Varsha; Sharma, Manish

    2012-01-01

    We study the dynamics of a suspension of magnetic nanoparticles. Their relaxation times are strongly size-dependent. The dominant mode of relaxation is also governed by the size of the particles. As a result the dynamics is greatly altered due to polydispersity in the sample. We study the effect of polydispersity on the response functions. These exhibit significant changes as the parameters characterizing polydispersity are varied. We also provide a procedure to extract the particle size dist...

  8. Polymorphism in Bacterial Flagella Suspensions

    Science.gov (United States)

    Schwenger, Walter J.

    Bacterial flagella are a type of biological polymer studied for its role in bacterial motility and the polymorphic transitions undertaken to facilitate the run and tumble behavior. The naturally rigid, helical shape of flagella gives rise to novel colloidal dynamics and material properties. This thesis studies methods in which the shape of bacterial flagella can be controlled using in vitro methods and the changes the shape of the flagella have on both single particle dynamics and bulk material properties. We observe individual flagellum in both the dilute and semidilute regimes to observe the effects of solvent condition on the shape of the filament as well as the effect the filament morphology has on reptation through a network of flagella. In addition, we present rheological measurements showing how the shape of filaments effects the bulk material properties of flagellar suspensions. We find that the individual particle dynamics in suspensions of flagella can vary with geometry from needing to reptate linearly via rotation for helical filaments to the prevention of long range diffusion for block copolymer filaments. Similarly, for bulk material properties of flagella suspensions, helical geometries show a dramatic enhancement in elasticity over straight filaments while block copolymers form an elastic gel without the aid of crosslinking agents.

  9. Ionic conductivity studies of gel polyelectrolyte based on ionic liquid

    Energy Technology Data Exchange (ETDEWEB)

    Cha, E.H. [The Faculty of Liberal Arts (Chemistry), Hoseo University, Asan Choongnam 336-795 (Korea); Lim, S.A. [Functional Proteomics Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea); Park, J.H. [Department of Herbal Medicine, Hoseo University, Asan Choongnam 336-795 (Korea); Kim, D.W. [Department of Chemical Technology, Han Bat National University, Daejon 305-719 (Korea); Macfarlane, D.R. [School of Chemistry, Monash University, Clayton, Vic. 3800 (Australia)

    2008-04-01

    Novel lithium polyelectrolyte-ionic liquids have been prepared and characterized of their properties. Poly(lithium 2-acrylamido-2-methyl propanesulfonate) (PAMPSLi) and its copolymer with N-vinyl formamide (VF) also has been prepared as a copolymer. 1-Ethyl-3-methylimidazolium tricyanomethanide (emImTCM) and N,N-dimethyl-N-propyl-N-butyl ammonium tricyanomethanide (N{sub 1134}TCM) which are chosen because of the same with the anion of ionic liquid were prepared. The ionic conductivity of copolymer system (PAMPSLi/PVF/emImTCM: 5.43 x 10{sup -3} S cm{sup -1} at 25 C) exhibits about over four times higher than that of homopolymer system (PAMPSLi/emImTCM: 1.28 x 10{sup -3} S cm{sup -1} at 25 C). Introduction of vinyl formamide into the copolymer type can increase the dissociation of the lithium cations from the polymer backbone. The ionic conductivity of copolymer with emImTCM (PAMPSLi/PVF/emImTCM) exhibits the higher conductivity than that of PAMPSLi/PVF/N{sub 1134}TCM (2.48 x 10{sup -3} S cm{sup -1}). Because of using the polymerizable anion it is seen to maintain high flexibility of imidazolium cation effectively to exhibit the higher conductivity. And also the viscosity of emImTCM (19.56 cP) is lower than that of N{sub 1134}TCM (28.61 cP). Low viscosity leads to a fast rate of diffusion of redox species. (author)

  10. Detection analysis of surface hydroxyl active sites and simulation calculation of the surface dissociation constants of aqueous diatomite suspensions

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Shu-Cui [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Key Laboratory of Applied Chemistry and Nanotechnology at Universities of Jilin Province, Changchun University of Science and Technology, Changchun 130022 (China); Wang, Zhi-Gang [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Zhang, Ji-Lin, E-mail: zjl@ciac.ac.cn [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Sun, De-Hui [Changchun Institute Technology, Changchun 130012 (China); Liu, Gui-Xia, E-mail: liuguixia22@163.com [Key Laboratory of Applied Chemistry and Nanotechnology at Universities of Jilin Province, Changchun University of Science and Technology, Changchun 130022 (China)

    2015-02-01

    Highlights: • To examine surface hydroxyl functional groups of the calcined diatomite by TGA-DSC, FTIR, and XPS. • To calculate the optimized log K{sub 1}, log K{sub 2} and log C values and the surface species distribution of each surface reactive site using ProtoFit and PHREEQC, respectively. - Abstract: The surface properties of the diatomite were investigated using nitrogen adsorption/deadsorption isotherms, TG-DSC, FTIR, and XPS, and surface protonation–deprotonation behavior was determined by continuous acid–base potentiometric titration technique. The diatomite sample with porous honeycomb structure has a BET specific surface area of 10.21 m{sup 2}/g and large numbers of surface hydroxyl functional groups (i.e. ≡Si-OH, ≡Fe-OH, and ≡Al-OH). These surface hydroxyls can be protonated or deprotonated depending on the pH of the suspension. The experimental potentiometric data in two different ionic strength solutions (0.1 and 0.05 mol/L NaCl) were fitted using ProtoFit GUI V2.1 program by applying diffuse double layer model (DLM) with three amphoteric sites and minimizing the sum of squares between a dataset derivative function and a model derivative function. The optimized surface parameters (i.e. surface dissociation constants (log K{sub 1}, log K{sub 2}) and surface site concentrations (log C)) of the sample were obtained. Based on the optimized surface parameters, the surface species distribution was calculated using Program-free PHREEQC 3.1.2. Thus, this work reveals considerable new information about surface protonation–deprotonation processes and surface adsorptive behaviors of the diatomite, which helps us to effectively use the cheap and cheerful diatomite clay adsorbent.

  11. Quality assessment of fluconazole capsules and oral suspensions compounded by pharmacies located in the United States.

    Science.gov (United States)

    Laporte, Carine M; Cruz-Espindola, Crisanta; Thungrat, Kamoltip; Schick, Anthea E; Lewis, Thomas P; Boothe, Dawn M

    2017-04-01

    OBJECTIVE To evaluate pharmaceutical characteristics (strength or concentration, accuracy, and precision), physical properties, and bacterial contamination of fluconazole compounded products. SAMPLE Fluconazole compounded products (30- and 240-mg capsules; 30- and 100-mg/mL oral suspensions) from 4 US veterinary compounding pharmacies. PROCEDURES Fluconazole compounded products were ordered 3 times from each of 4 pharmacies at 7- or 10-day intervals. Generic fluconazole products (50- and 200-mg tablets; 10- and 40-mg/mL oral suspensions) served as references. Compounded products were evaluated at the time of receipt; suspensions also were evaluated 3 months later and at beyond-use dates. Evaluations included assessments of strength (concentration), accuracy, precision, physical properties, and bacterial contamination. Acceptable accuracy was defined as within ± 10% of the labeled strength (concentration) and acceptable precision as within ± 10%. Fluconazole was quantified by use of high-performance liquid chromatography. RESULTS Physical characteristics of compounded products differed among pharmacies. Aerobic bacterial cultures yielded negative results. Capsules (30 and 240 mg) had acceptable accuracy (median, 96.3%; range, 87.3% to 135.2%) and precision (mean ± SD, 7.4 ± 6.0%). Suspensions (30 and 100 mg/mL) had poor accuracy (median, 73.8%; range, 53.9% to 95.2%) and precision (mean ± SD, 15.0 ± 6.9%). Accuracy and precision were significantly better for capsules than for suspensions. CONCLUSIONS AND CLINICAL RELEVANCE Fluconazole compounded products, particularly suspensions, differed in pharmaceutical and physical qualities. Studies to evaluate the impact of inconsistent quality on bioavailability or clinical efficacy of compounded fluconazole products are indicated, and each study should include data on the quality of the compounded product evaluated.

  12. Ionic Liquids to Replace Hydrazine

    Science.gov (United States)

    Koelfgen, Syri; Sims, Joe; Forton, Melissa; Allan, Barry; Rogers, Robin; Shamshina, Julia

    2011-01-01

    A method for developing safe, easy-to-handle propellants has been developed based upon ionic liquids (ILs) or their eutectic mixtures. An IL is a binary combination of a typically organic cation and anion, which generally produces an ionic salt with a melting point below 100 deg C. Many ILs have melting points near, or even below, room temperature (room temperature ionic liquids, RTILs). More importantly, a number of ILs have a positive enthalpy of formation. This means the thermal energy released during decomposition reactions makes energetic ILs ideal for use as propellants. In this specific work, to date, a baseline set of energetic ILs has been identified, synthesized, and characterized. Many of the ILs in this set have excellent performance potential in their own right. In all, ten ILs were characterized for their enthalpy of formation, density, melting point, glass transition point (if applicable), and decomposition temperature. Enthalpy of formation was measured using a microcalorimeter designed specifically to test milligram amounts of energetic materials. Of the ten ILs characterized, five offer higher Isp performance than hydrazine, ranging between 10 and 113 seconds higher than the state-of-the-art propellant. To achieve this level of performance, the energetic cations 4- amino-l,2,4-triazolium and 3-amino-1,2,4-triazolium were paired with various anions in the nitrate, dicyanamide, chloride, and 3-nitro-l,2,4-triazole families. Protonation, alkylation, and butylation synthesis routes were used for creation of the different salts.

  13. Drag Reduction of Bacterial Cellulose Suspensions

    Directory of Open Access Journals (Sweden)

    Satoshi Ogata

    2011-01-01

    Full Text Available Drag reduction due to bacterial cellulose suspensions with small environmental loading was investigated. Experiments were carried out by measuring the pressure drop in pipe flow. It was found that bacterial cellulose suspensions give rise to drag reduction in the turbulent flow range. We observed a maximum drag reduction ratio of 11% and found that it increased with the concentration of the bacterial cellulose suspension. However, the drag reduction effect decreased in the presence of mechanical shear.

  14. Introducing Dual Suspension System in Road Vehicles

    Directory of Open Access Journals (Sweden)

    Imtiaz Hussain

    2013-04-01

    Full Text Available The main objective of suspension system is to reduce the motions of the vehicle body with respect to road disturbances. The conventional suspension systems in road vehicles use passive elements such as springs and dampers to suppress the vibrations induced by the irregularities in the road. But these conventional suspension systems can suppress vibrations to a certain limit. This paper presents a novel idea to improve the ride quality of roads vehicles without compromising vehicle?s stability. The paper proposes the use of primary and secondary suspension to suppress the vibrations more effectively.

  15. Time Varying Behavior of the Loudspeaker Suspension

    DEFF Research Database (Denmark)

    Pedersen, Bo Rohde; Agerkvist, Finn T.

    2007-01-01

    The suspension part of the electrodynamic loudspeaker is often modelled as a simple linear spring with viscous damping, however the dynamic behaviour of the suspension is much more complicated than predicted by such a simple model. At higher levels the compliance becomes non-linear and often...... changes during excitation at high levels. This paper investigates how the compliance of the suspension depends on the excitation, i.e. level and frequency content. The measurements are compared with other known measurement methods of the suspension....

  16. Molecular and ionic hydrogen bond formation in fluorous solvents.

    Science.gov (United States)

    O'Neal, Kristi L; Weber, Stephen G

    2009-01-08

    There are only a few studies of noncovalent association in fluorous solvents and even fewer that are quantitative. A full understanding, particularly of stoichiometry and binding strength of noncovalent interactions in fluorous solvents could be very useful in improved molecular-receptor-based extractions, advancements in sensor technologies, crystal engineering, and supramolecular chemistry. This work investigates hydrogen bonding between heterocyclic bases and a perfluoropolyether with a terminal carboxylic acid group (Krytox 157FSH (1)), chiefly in FC-72 (a mixture of perfluorohexanes). In particular, we were interested in whether or not proton transfer occurs, and if so, under what conditions in H-bonded complexes. Continuous variations experiments show that in FC-72 weaker bases (pyrazine, pyrimidine, and quinazoline) form 1:1 complexes with 1, whereas stronger bases (quinoline, pyridine, and isoquinoline) form 1:3 complexes. Ultraviolet and infrared spectral signatures reveal that the 1:1 complexes are molecular (B.HA) whereas the 1:3 complexes are ionic (BH+.A-HAHA). Infrared spectra of 1:3 ionic complexes are discussed in detail. Literature and experimental data on complexes between N-heterocyclic bases and carboxylic acids in a range of solvents are compiled to compare solvent effects on proton transfer. Polar solvents support ionic hydrogen bonds at a 1:1 mol ratio. In nonpolar organic solvents, ionic hydrogen bonds are only observed in complexes with 1:2 (base/acid) stoichiometries. In fluorous solvents, a larger excess of acid, 1:3, is necessary to facilitate proton transfer in hydrogen bonds between carboxylic acids and the bases studied.

  17. Transformations of Liquid Metals in Ionic Liquid

    OpenAIRE

    Liu, Fujun; Yu, Yongze; Liu, Jing

    2017-01-01

    Experimental studies were carried out on the motions and transformations of liquid metal in ionic liquid under applied electric field. The induced vortex rings and flows of ionic liquid were determined via the photographs taken sequentially over the experiments. The polarization of electric double layer of liquid metals was employed to explain the flow of ionic liquid with the presence of liquid metal. Unlike former observation of liquid metal machine in conventional solution, no gas bubble w...

  18. Membrane separation of ionic liquid solutions

    Energy Technology Data Exchange (ETDEWEB)

    Campos, Daniel; Feiring, Andrew Edward; Majumdar, Sudipto; Nemser, Stuart

    2015-09-01

    A membrane separation process using a highly fluorinated polymer membrane that selectively permeates water of an aqueous ionic liquid solution to provide dry ionic liquid. Preferably the polymer is a polymer that includes polymerized perfluoro-2,2-dimethyl-1,3-dioxole (PDD). The process is also capable of removing small molecular compounds such as organic solvents that can be present in the solution. This membrane separation process is suitable for drying the aqueous ionic liquid byproduct from precipitating solutions of biomass dissolved in ionic liquid, and is thus instrumental to providing usable lignocellulosic products for energy consumption and other industrial uses in an environmentally benign manner.

  19. Improved Ionic Liquids as Space Lubricants Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Ionic liquids are candidate lubricant materials. However for application in low temperature space mechanisms their lubrication performance needs to be enhanced. UES...

  20. "Practical" Electrospinning of Biopolymers in Ionic Liquids.

    Science.gov (United States)

    Shamshina, Julia L; Zavgorodnya, Oleksandra; Bonner, Jonathan R; Gurau, Gabriela; Di Nardo, Thomas; Rogers, Robin D

    2017-01-10

    To address the need to scale up technologies for electrospinning of biopolymers from ionic liquids to practical volumes, a setup for the multi-needle electrospinning of chitin using the ionic liquid 1-ethyl-3-methylimidazolium acetate, [C2 mim]-[OAc], was designed, built, and demonstrated. Materials with controllable and high surface area were prepared at the nanoscale using ionic-liquid solutions of high-molecular-weight chitin extracted with the same ionic liquid directly from shrimp shells. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Diffusion of Magnetized Binary Ionic Mixtures at Ultracold Plasma Conditions

    Science.gov (United States)

    Vidal, Keith R.; Baalrud, Scott D.

    2017-10-01

    Ultracold plasma experiments offer an accessible means to test transport theories for strongly coupled systems. Application of an external magnetic field might further increase their utility by inhibiting heating mechanisms of ions and electrons and increasing the temperature at which strong coupling effects are observed. We present results focused on developing and validating a transport theory to describe binary ionic mixtures across a wide range of coupling and magnetization strengths relevant to ultracold plasma experiments. The transport theory is an extension of the Effective Potential Theory (EPT), which has been shown to accurately model correlation effects at these conditions, to include magnetization. We focus on diffusion as it can be measured in ultracold plasma experiments. Using EPT within the framework of the Chapman-Enskog expansion, the parallel and perpendicular self and interdiffusion coefficients for binary ionic mixtures with varying mass ratios are calculated and are compared to molecular dynamics simulations. The theory is found to accurately extend Braginskii-like transport to stronger coupling, but to break down when the magnetization strength becomes large enough that the typical gyroradius is smaller than the interaction scale length. This material is based upon work supported by the Air Force Office of Scientific Research under Award Number FA9550-16-1-0221.

  2. WtF-Nano: One-pot dewatering and water-free topochemical modification of nanocellulose in ionic liquids or gamma-valerolactone.

    Science.gov (United States)

    Laaksonen, Tiina; Helminen, Jussi Kari Juhani; Lemetti, Laura; Långbacka, Jesper; Rico Del Cerro, Daniel; Hummel, Michael; Filpponen, Erkko Ilari; Rantamäki, Antti; Kakko, Tia; Kemell, Marianna; Wiedmer, Susanne; Heikkinen, Sami; Kilpeläinen, Ilkka; King, Alistair William Thomas

    2017-11-07

    It is shown that ionic liquids can be used to dewater birch kraft pulp cellulose nanofibrillar (CNF) suspension and act as a medium for water-free topochemical modification of the nanocellulose. Acetylation, was applied as a model reaction to investigate the degree of modification and scope of effective ionic liquid structures. Little difference in reactivity was observed when water was removed, after introduction of ionic liquid or molecular co-solvent. However, the viscoelastic properties of CNF suspended in two ionic liquids showed that the more basic, but non-dissolving ionic liquid, allows for better solvation of the CNF. Vibrio fischeri bacterials tests showed that all ionic liquids in this study were harmless. Scanning electron microscopy and wide-angle X-ray scattering on regenerated samples show that the acetylated CNF is still in a fibrillar form. 1D and 2D NMR analysis, after direct dissolution in a novel ionic liquid electrolyte solution, identified that both cellulose and residual xylan on the surface of the nanofibrils reacts to give acetate esters. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Photoelectrochemical studies on aqueous suspensions of some ...

    Indian Academy of Sciences (India)

    pensions meet these requirements. The suspension media are equally as important as the suspension particles in generating an efficient photolysis process. Previous studies used semi- conductor particles as major producers of photonic outcome through heterogeneous charge transfer processes at the par- ticle/electrolyte ...

  4. 49 CFR 238.227 - Suspension system.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Suspension system. 238.227 Section 238.227 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION... Equipment § 238.227 Suspension system. On or after November 8, 1999— (a) All passenger equipment shall...

  5. Phase diagram of vertically vibrated dense suspensions

    NARCIS (Netherlands)

    von Kann, S.; Snoeijer, Jacobus Hendrikus; van der Meer, Roger M.

    2014-01-01

    When a hole is created in a layer of a dense, vertically vibrated suspension, phenomena are known to occur that defy the natural tendency of gravity to close the hole. Here, an overview is presented of the different patterns that we observed in a variety of dense particulate suspensions.

  6. Active suspension for a field sprayer boom

    DEFF Research Database (Denmark)

    Nielsen, Henrik Skovsgaard; Sørensen, Paul Haase

    1998-01-01

    The possibilities of implementing an active boom suspension is investigated. The performance improvement of an active suspension over a traditional passive one is studied in simulation, and shows a significant improvement. A closed-loop control system involving two ultrasonic distance transducers...

  7. Time Variance of the Suspension Nonlinearity

    DEFF Research Database (Denmark)

    Agerkvist, Finn T.; Pedersen, Bo Rohde

    2008-01-01

    . This paper investigates the changes in compliance the driving signal can cause, this includes low level short duration measurements of the resonance frequency as well as high power long duration measurements of the non-linearity of the suspension. It is found that at low levels the suspension softens...

  8. 32 CFR 1609.5 - Suspension.

    Science.gov (United States)

    2010-07-01

    ... 32 National Defense 6 2010-07-01 2010-07-01 false Suspension. 1609.5 Section 1609.5 National Defense Other Regulations Relating to National Defense SELECTIVE SERVICE SYSTEM UNCOMPENSATED PERSONNEL § 1609.5 Suspension. The Director of Selective Service may suspend from duty any uncompensated person...

  9. 25 CFR 242.7 - Suspension.

    Science.gov (United States)

    2010-04-01

    ... 25 Indians 1 2010-04-01 2010-04-01 false Suspension. 242.7 Section 242.7 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR FISH AND WILDLIFE COMMERCIAL FISHING ON RED LAKE INDIAN RESERVATION § 242.7 Suspension. All commercial fishing operations may be suspended by order of the Secretary at any...

  10. 39 CFR 955.28 - Suspension.

    Science.gov (United States)

    2010-07-01

    ... 39 Postal Service 1 2010-07-01 2010-07-01 false Suspension. 955.28 Section 955.28 Postal Service UNITED STATES POSTAL SERVICE PROCEDURES RULES OF PRACTICE BEFORE THE POSTAL SERVICE BOARD OF CONTRACT APPEALS § 955.28 Suspension. (a) Whenever at any time it appears that the parties are in agreement as to...

  11. 32 CFR 552.77 - Suspension approval.

    Science.gov (United States)

    2010-07-01

    ... 32 National Defense 3 2010-07-01 2010-07-01 true Suspension approval. 552.77 Section 552.77 National Defense Department of Defense (Continued) DEPARTMENT OF THE ARMY MILITARY RESERVATIONS AND....77 Suspension approval. The installation commander will personally approve all cases in which...

  12. 21 CFR 520.1289 - Lufenuron suspension.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Lufenuron suspension. 520.1289 Section 520.1289 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS ORAL DOSAGE FORM NEW ANIMAL DRUGS § 520.1289 Lufenuron suspension. (a...

  13. Ionic hydrogenation of organosulfur compounds

    Energy Technology Data Exchange (ETDEWEB)

    Eckert-Maksic, M.; Margetic, D. (Rudjer Boskovic Institute, Zagreb (Yugoslavia). Dept. of Organic Chemistry and Biochemistry)

    Ionic hydrogenation of the three most abundant types of organosulfur constituents of coal, aromatic sulfides, aromatic disulfides, and benzo(b)thiophene derivatives, in BF{sub 3}.H{sub 2}O-Et{sub 3}SiH is studied. Reduction of aromatic sulfides results in partial saturation of the aromatic moiety and cleavage of the corresponding SR group. Aromatic disulfides undergo quantitative sulfur-sulfur bond cleavage, while benzo(b)thiophene derivatives produce 2,3-dihydrobenzo(b)thiophenes in high yields. 32 refs., 2 figs., 3 tabs.

  14. Pseudo-steady rates of crystal nucleation in suspensions of charged colloidal particles

    CERN Document Server

    Dixit, N M

    2003-01-01

    We develop an analytical model to describe crystal nucleation in suspensions of charged colloidal particles. The particles are assumed to interact with a repulsive hard-core Yukawa potential. The thermodynamic properties of the suspensions are determined by mapping onto an effective hard-sphere system using perturbation theory. Hydrodynamic effects are calculated by approximating particle interactions with the excluded shell potential. The rates of particle aggregation and dissociation from cluster surfaces in supersaturated suspensions are determined by solving the diffusion and Smoluchowski equations, respectively, which allow the calculation of pseudo-steady rates of crystal nucleation. By decoupling thermodynamic and hydrodynamic effects, we find intriguing non-monotonic dependencies of the nucleation rate on the strength and the range of particle repulsions. In particular, we find that the rate at any effective hard-sphere volume fraction can be lower than that of the hard-sphere system at that volume fr...

  15. Nitration of plant apoplastic proteins from cell suspension cultures.

    Science.gov (United States)

    Szuba, Agnieszka; Kasprowicz-Maluśki, Anna; Wojtaszek, Przemysław

    2015-04-29

    Nitric oxide causes numerous protein modifications including nitration of tyrosine residues. This modification, though one of the greatest biological importance, is poorly recognized in plants and is usually associated with stress conditions. In this study we analyzed nitrotyrosines from suspension cultures of Arabidopsis thaliana and Nicotiana tabacum, treated with NO modulators and exposed to osmotic stress, as well as of BY2 cells long-term adapted to osmotic stress conditions. Using confocal microscopy, we showed that the cell wall area is one of the compartments most enriched in nitrotyrosines within a plant cell. Subsequently, we analyzed nitration of ionically-bound cell-wall proteins and identified selected proteins with MALDI-TOF spectrometry. Proteomic analysis indicated that there was no significant increase in the amount of nitrated proteins under the influence of NO modulators, among them 3-morpholinosydnonimine (SIN-1), considered a donor of nitrating agent, peroxynitrite. Moreover, osmotic stress conditions did not increase the level of nitration in cell wall proteins isolated from suspension cells, and in cultures long-term adapted to stress conditions; that level was even reduced in comparison with control samples. Among identified nitrotyrosine-containing proteins dominated the ones associated with carbon circulation as well as the numerous proteins responding to stress conditions, mainly peroxidases. High concentrations of nitric oxide found in the cell wall and the ability to produce large amounts of ROS make the apoplast a site highly enriched in nitrotyrosines, as presented in this paper. Analysis of ionically bound fraction of the cell wall proteins indicating generally unchanged amounts of nitrotyrosines under influence of NO modulators and osmotic stress, is noticeably different from literature data concerning, however, the total plant proteins analysis. This observation is supplemented by further nitroproteome analysis, for cells long

  16. 48 CFR 9.407-4 - Period of suspension.

    Science.gov (United States)

    2010-10-01

    ... ACQUISITION PLANNING CONTRACTOR QUALIFICATIONS Debarment, Suspension, and Ineligibility 9.407-4 Period of... notice, the suspension shall be terminated unless an Assistant Attorney General requests its extension...

  17. Quantifying the effect of ionic screening with protein-decorated graphene transistors.

    Science.gov (United States)

    Ping, Jinglei; Xi, Jin; Saven, Jeffery G; Liu, Renyu; Johnson, A T Charlie

    2017-03-15

    Liquid-based applications of biomolecule-decorated field-effect transistors (FETs) range from biosensors to in vivo implants. A critical scientific challenge is to develop a quantitative understanding of the gating effect of charged biomolecules in ionic solution and how this influences the readout of the FETs. To address this issue, we fabricated protein-decorated graphene FETs and measured their electrical properties, specifically the shift in Dirac voltage, in solutions of varying ionic strength. We found excellent quantitative agreement with a model that accounts for both the graphene polarization charge and ionic screening of ions adsorbed on the graphene as well as charged amino acids associated with the immobilized protein. The technique and analysis presented here directly couple the charging status of bound biomolecules to readout of liquid-phase FETs fabricated with graphene or other two-dimensional materials. Copyright © 2015 Elsevier B.V. All rights reserved.

  18. Benzene solubility in ionic liquids: working toward an understanding of liquid clathrate formation.

    Science.gov (United States)

    Pereira, Jorge F B; Flores, Luis A; Wang, Hui; Rogers, Robin D

    2014-11-17

    The solubility of benzene in 15 imidazolium, pyrrolidinium, pyridinium, and piperidinium ionic liquids has been determined; the resulting, benzene-saturated ionic liquid solutions, also known as liquid clathrates, were examined with (1) H and (19) F nuclear magnetic resonance spectroscopy to try and understand the molecular interactions that control liquid clathrate formation. The results suggest that benzene interacts primarily with the cation of the ionic liquid, and that liquid clathrate formation (and benzene solubility) is controlled by the strength of the cation-anion interactions, that is, the stronger the cation-anion interaction, the lower the benzene solubility. Other factors that were determined to be important in the final amount of benzene in any given liquid clathrate phase included attractive interactions between the anion and benzene (when significant), and larger steric or free volume demands of the ions, both of which lead to greater benzene solubility. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Next Generation Suspension Dynamics Algorithms

    Energy Technology Data Exchange (ETDEWEB)

    Schunk, Peter Randall [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Higdon, Jonathon [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Chen, Steven [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2014-12-01

    This research project has the objective to extend the range of application, improve the efficiency and conduct simulations with the Fast Lubrication Dynamics (FLD) algorithm for concentrated particle suspensions in a Newtonian fluid solvent. The research involves a combination of mathematical development, new computational algorithms, and application to processing flows of relevance in materials processing. The mathematical developments clarify the underlying theory, facilitate verification against classic monographs in the field and provide the framework for a novel parallel implementation optimized for an OpenMP shared memory environment. The project considered application to consolidation flows of major interest in high throughput materials processing and identified hitherto unforeseen challenges in the use of FLD in these applications. Extensions to the algorithm have been developed to improve its accuracy in these applications.

  20. Suspension-Firing of Biomass

    DEFF Research Database (Denmark)

    Bashir, Muhammad Shafique; Jensen, Peter Arendt; Frandsen, Flemming

    2012-01-01

    This paper is Part 1 in a series of two describing probe measurements of deposit build-up and removal (shedding) in a 350 MWth suspension boiler, firing straw and wood. The influence of fuel type (straw share in wood), probe exposure time, probe surface temperature (500, 550, and 600 °C), and flue...... gas temperature (600–1050 °C) on ash deposit formation rate has been investigated. Investigations of deposit formation rate were made by use of an advanced online deposit probe that allowed nearly continuous measurement of the deposited mass. Two different measures of deposit formation rate are used...... in the analysis of the data. The first is the integral deposit formation rate (IDF-rate) found by dividing the integral mass change over integral time intervals (of order several hours) by the time interval. The IDF-rate is similar to deposit formation rates based on total deposit mass uptake divided by probe...

  1. Improved ionic model of liquid uranium dioxide

    NARCIS (Netherlands)

    Gryaznov, [No Value; Iosilevski, [No Value; Yakub, E; Fortov, [No Value; Hyland, GJ; Ronchi, C

    The paper presents a model for liquid uranium dioxide, obtained by improving a simplified ionic model, previously adopted to describe the equation of state of this substance [1]. A "chemical picture" is used for liquid UO2 of stoichiometric and non-stoichiometric composition. Several ionic species

  2. Aqueous solutions of ionic liquids: microscopic assembly

    NARCIS (Netherlands)

    Vicent-Luna, J.M.; Dubbeldam, D.; Gómez-Álvarez, P.; Calero, S.

    2016-01-01

    Aqueous solutions of ionic liquids are of special interest, due to the distinctive properties of ionic liquids, in particular, their amphiphilic character. A better understanding of the structure-property relationships of such systems is hence desirable. One of the crucial molecular-level

  3. Dielectric study on mixtures of ionic liquids.

    Science.gov (United States)

    Thoms, E; Sippel, P; Reuter, D; Weiß, M; Loidl, A; Krohns, S

    2017-08-07

    Ionic liquids are promising candidates for electrolytes in energy-storage systems. We demonstrate that mixing two ionic liquids allows to precisely tune their physical properties, like the dc conductivity. Moreover, these mixtures enable the gradual modification of the fragility parameter, which is believed to be a measure of the complexity of the energy landscape in supercooled liquids. The physical origin of this index is still under debate; therefore, mixing ionic liquids can provide further insights. From the chemical point of view, tuning ionic liquids via mixing is an easy and thus an economic way. For this study, we performed detailed investigations by broadband dielectric spectroscopy and differential scanning calorimetry on two mixing series of ionic liquids. One series combines an imidazole based with a pyridine based ionic liquid and the other two different anions in an imidazole based ionic liquid. The analysis of the glass-transition temperatures and the thorough evaluations of the measured dielectric permittivity and conductivity spectra reveal that the dynamics in mixtures of ionic liquids are well defined by the fractions of their parent compounds.

  4. Supported Ionic Liquid Phase (SILP) catalysis

    DEFF Research Database (Denmark)

    Riisager, Anders; Fehrmann, Rasmus; Haumann, Marco

    2006-01-01

    Applications of ionic liquids to replace conventional solvents in homogeneous transition-metal catalysis have increased significantly during the last decade. Biphasic ionic liquid/organic liquid systems offer advantages with regard to product separation, catalyst stability, and recycling but util...

  5. Engineered microorganisms having resistance to ionic liquids

    Energy Technology Data Exchange (ETDEWEB)

    Ruegg, Thomas Lawrence; Thelen, Michael P.

    2016-03-22

    The present invention provides for a method of genetically modifying microorganisms to enhance resistance to ionic liquids, host cells genetically modified in accordance with the methods, and methods of using the host cells in a reaction comprising biomass that has been pretreated with ionic liquids.

  6. Naratriptan hydrochloride in extemporaneosly compounded oral suspensions.

    Science.gov (United States)

    Zhang, Y P; Trissel, L A; Fox, J L

    2000-01-01

    The purpose of this study was to determine the pharmaceutical acceptability and chemical stability of naratriptan hydrochloride in three extemporaneously compounded suspension formulations. The naratriptan-hydrochloride oral suspensions were prepared from 2.5-mg commercial tablets yielding a nominal naratriptan concentration of 0.5 mg/mL. The suspension vehicles selected for testing were Syrpalta, an equal-parts mixture of Ora-Plus and Ora-Sweet, and an equal-parts mixture of Ora-Plus and Ora-Sweet SF. The tablets were crushed and thoroughly triturated to a fine powder using a porcelain mortar and pestle. The powder was incorporated into a portion of the Syrpalta or Ora-Plus suspension vehicle and mixed until homogeneous. The mixtures were then brought to volume with Syrpalta, Ora-Sweet or Ora-Sweet SF, as appropriate. The suspensions were packaged in amber, plastic, screw-cap prescription bottles and stored at 23 deg C for seven days and 4 deg C for 90 days. An adequate suspension was never achieved in Syrpalta. The crushed-tablet powder did not produce a uniformly dispersed mixture and exhibited clumping and a high rate of sedimentation. A distinct layer of the solid tablet material settled immediately after shaking. Over the next four hours, a densely packed, yellow, caked layer formed at the bottom of the containers, making resuspension difficult. During storage, the caking became worse. Chemical analysis was not performed. The Ora-Plus and Ora-Sweet or Ora-Sweet SF suspensions had a slight greenish cast and were resuspended without difficulty by shaking for approximately ten seconds, yielding easily poured and homogeneous mixtures throughout the study. Visible settling and layering did not begin for four hours with the Ora-Sweet suspension and 24 hours for the Ora-Sweet SF suspension. High pressure liquid chromatographic analysis found that the naratriptan concentration in both suspension-vehicle combinations exhibited little or no loss for seven days at 23

  7. Stability of diclofenac sodium oral suspensions packaged in amber polyvinyl chloride bottles.

    Science.gov (United States)

    Donnelly, Ronald F; Pascuet, Elena; Ma, Carmen; Vaillancourt, Régis

    2010-01-01

    Prescribing of diclofenac for children usually involves a dose different from commercially available strengths. This drug is available only as tablets, which can be divided only so many times before the dose obtained becomes inaccurate. In addition, children may have difficulty swallowing tablets. For these reasons, a compounding formula for a liquid dosage form is essential to ensure effective delivery of the drug to pediatric patients. To develop a compounding formula for diclofenac sodium and to determine the extended physical and chemical stability of this compound when stored in amber polyvinyl chloride (PVC) prescription bottles under refrigeration and at room temperature. A suspension of diclofenac sodium (10 mg/mL) was prepared from commercially available diclofenac sodium tablets, with Ora-Blend as the suspending and flavouring agent. The suspension was packaged in 60-mL amber PVC prescription bottles and stored at either room temperature (23°C) or under refrigeration (5°C). Samples were collected on days 0, 7, 14, 21, 27, 56, and 93. Chemical stability was determined using a validated stability-indicating high-performance liquid chromatography method. At each sampling time, the suspensions were checked for changes in appearance (i.e., colour, layering, caking, ease of resuspension), odour, and pH. The diclofenac sodium suspensions were very stable, retaining at least 99.5% of the original concentration for up to 93 days, regardless of storage temperature. There were no apparent changes in the physical appearance of the suspensions, nor were there any substantial changes in odour or pH. Suspensions of diclofenac sodium (10 mg/mL) were quantitatively stable but difficult to prepare because of the enteric coating of the tablets. Therefore, it is recommended that diclofenac powder be used for the preparation of suspensions. For pediatric use, palatability is a consideration, and a masking agent should be added before administration. An expiry date of up to

  8. Application of Ionic Liquids in Hydrometallurgy

    Directory of Open Access Journals (Sweden)

    Jesik Park

    2014-08-01

    Full Text Available Ionic liquids, low temperature molten salts, have various advantages manifesting themselves as durable and environmentally friendly solvents. Their application is expanding into various fields including hydrometallurgy due to their unique properties such as non-volatility, inflammability, low toxicity, good ionic conductivity, and wide electrochemical potential window. This paper reviews previous literatures and our recent results adopting ionic liquids in extraction, synthesis and processing of metals with an emphasis on the electrolysis of active/light, rare earth, and platinum group metals. Because the research and development of ionic liquids in this area are still emerging, various, more fundamental approaches are expected to popularize ionic liquids in the metal manufacturing industry.

  9. Comparison of intravenous drip infusion excretory urography using ionic and non-ionic contrast media

    Energy Technology Data Exchange (ETDEWEB)

    Onitsuka, Hideo; Araki, Akiteru; Torii, Yoshikuni; Tsukuda, Masaaki; Murakami, Junji; Ino, Akihiro; Hashiguchi, Norihisa; Masuda, Kouji (Kyushu Univ., Fukuoka (Japan). Faculty of Medicine)

    1989-07-01

    Ionic and non-ionic contrast media were compared for use in intravenous drip infusion excretory urography. Sixty consecutive cases were classified alternately into two groups, ionic and non-ionic, excluding cases which were known to have factors affecting contrast ability adversely, such as hydronephrosis, renal failure and so on. Each group consisted of 30 cases. A hundred ml of the ionic contrast medium (Diatrizoate-60% Urografin) or non-ionic contrast medium (Iopamidol-Iopamiron 300) was administered I.V. by drip infusion, each infusion taking less than 10 minutes, using a 18 G needle, and 0-minute, 10-minute and 20-minute films were obtained. Visibility of nephrogram, calyceal system, renal pelvis, ureters and bladder were evaluated, ranging from 0 to 3, by six radiologists who were not informed of the contrast medium used. Some detailed factors such as radiographic contrast and fullness of the collecting system and of the bladder were also analyzed. Visualization rate of the ureters was defined as the length of visualized ureters divided by the distance between the renal pelvis and the ureteral orifice of the bladder. There was no significant difference in visualization of nephrogram between the two groups. However, the non-ionic group was superior to the ionic group in visualization of the calyceal system and ureters with statistical significance, probably due to higher radiogrpahic contrast of non-ionic medium. There was no statistical significance between the two groups, in fullness of the calyceal system and visualization rate of the ureters, whereas the ionic group was superior to the non-ionic group in fullness of the bladder. In the ionic and non-ionic groups, side effects were seen in 6 and 2 cases, respectively, although this was not statistically significant. We conclude that non-ionic contrast medium is excellent for drip infusion excretory urography. (author).

  10. Self-powered suspension criterion and energy regeneration implementation scheme of motor-driven active suspension

    Science.gov (United States)

    Yan, Shuai; Sun, Weichao

    2017-09-01

    Active suspension systems have advantages on mitigating the effects of vehicle vibration caused by road roughness, which are one of the most important component parts in influencing the performances of vehicles. However, high amount of energy consumption restricts the application of active suspension systems. From the point of energy saving, this paper presents a self-powered criterion of the active suspension system to judge whether a motor-driven suspension can be self-powered or not, and then a motor parameter condition is developed as a reference to design a self-powered suspension. An energy regeneration implementation scheme is subsequently proposed to make the active suspension which has the potential to be self-powered achieve energy-saving target in the real application. In this implementation scheme, operating electric circuits are designed based on different working status of the actuator and power source and it is realizable to accumulate energy from road vibration and supply energy to the actuator by switching corresponding electric circuits. To apply the self-powered suspension criterion and energy regeneration implementation scheme, an active suspension system is designed with a constrained H∞ controller and calculation results indicate that it has the capability to be self-powered. Simulation results show that the performances of the self-powered active suspension are nearly the same as those of the active suspension with an external energy source and can achieve energy regeneration at the same time.

  11. Stability of extemporaneously prepared rosuvastatin oral suspension.

    Science.gov (United States)

    Zaid, Abdel Naser; Shtayah, Rania; Qadumi, Ayman; Ghanem, Mashour; Qedan, Rawan; Daibes, Marah; Awwad, Somud Abu; Jaradat, Nidal; Kittana, Naim

    2017-10-01

    The stability of an extemporaneously prepared rosuvastatin suspension stored over 30 days under various storage conditions was evaluated. Rosuvastatin suspension was extemporaneously prepared using commercial rosuvastatin tablets as the source of active pharmaceutical ingredient. The organoleptic properties, dissolution profile, and stability of the formulation were investigated. For the stability studies, samples of the suspension were stored under 2 storage conditions, room temperature (25 °C and 60% relative humidity) and accelerated stability chambers (40 °C and 75% relative humidity). Viscosity, pH, organoleptic properties, and microbial contamination were evaluated according to the approved specifications. High-performance liquid chromatography was used for the analysis and quantification of rosuvastatin in selected samples. Microbiological investigations were also conducted. The prepared suspension showed acceptable organoleptic properties. It showed complete release of rosuvastatin within 15 minutes. The pH of the suspension was 9.8, which remained unchanged during the stability studies. The microbiological investigations demonstrated that the preparation was free of any microbial contamination. In addition, the suspension showed stability within at least the period of use of a 100-mL rosuvastatin bottle. Extemporaneously prepared rosuvastatin 20-mg/mL suspension was stable for 30 days when stored at room temperature. Copyright © 2017 by the American Society of Health-System Pharmacists, Inc. All rights reserved.

  12. Mouse Plantar Flexor Muscle Size and Strength After Inactivity and Training

    Science.gov (United States)

    2010-07-01

    suspension. Keywords: eccentric contraction , microgravity , exercise . SPACEFLIGHT CAUSES atrophy and strength loss in antigravity skeletal muscles ...RB. Mouse plantar fl exor muscle size and strength after inactivity and training. Aviat Space Environ Med 2010; 81: 632 – 8 . Introduction: Losses...in muscle mass and strength may affect an astronaut’s safety; therefore, it is of utmost importance to optimize countermeasures to minimize atrophy

  13. Strong Ionic Hydrogen Bonding Causes a Spectral Isotope Effect in Photoactive Yellow Protein

    Science.gov (United States)

    Kaledhonkar, Sandip; Hara, Miwa; Stalcup, T. Page; Xie, Aihua; Hoff, Wouter D.

    2013-01-01

    Standard hydrogen bonds are of great importance for protein structure and function. Ionic hydrogen bonds often are significantly stronger than standard hydrogen bonds and exhibit unique properties, but their role in proteins is not well understood. We report that hydrogen/deuterium exchange causes a redshift in the visible absorbance spectrum of photoactive yellow protein (PYP). We expand the range of interpretable isotope effects by assigning this spectral isotope effect (SIE) to a functionally important hydrogen bond at the active site of PYP. The inverted sign and extent of this SIE is explained by the ionic nature and strength of this hydrogen bond. These results show the relevance of ionic hydrogen bonding for protein active sites, and reveal that the inverted SIE is a novel, to our knowledge, tool to probe ionic hydrogen bonds. Our results support a classification of hydrogen bonds that distinguishes the properties of ionic hydrogen bonds from those of both standard and low barrier hydrogen bonds, and show how this classification helps resolve a recent debate regarding active site hydrogen bonding in PYP. PMID:24314088

  14. Control system design of active seat suspensions

    Science.gov (United States)

    Maciejewski, I.

    2012-03-01

    This paper presents an approach to the control system design of seat suspension systems for the active vibration attenuation. The paper presents the studies of the active vibration control strategy based on the reverse dynamics of force actuator and the primary controller. The multi-criteria optimization procedure is utilized in order to calculate the primary controller settings which subsequently define the vibro-isolation characteristics of active suspensions. As an example of the proposed control system design, the seat with a pneumatic suspension is investigated and its vibro-isolation properties are shaped by an appropriate selection of the controller settings.

  15. Suspension for the low frequency facility

    CERN Document Server

    Cella, G; Di Virgilio, A; Gaddi, A; Viceré, A

    2000-01-01

    We introduce the working principles of the VIRGO Low Frequency Facility (LFF), whose main aim is the measurement of the thermal noise in the VIRGO suspension system. We evaluate the displacement thermal noise of a mirror, which is an intermediate element of a double pendulum suspension system. This double pendulum will be suspended to the last stage of a VIRGO Super-Attenuator (SA), the prototype VIRGO suspension system being tested at the Pisa section of INFN. In the proposed configuration, we evaluate the spectrum of the thermal noise for different choices of the parameters: based on this study, we comment on the future directions to be undertaken in the LFF experiment.

  16. Specific ionic effect for simple and rapid colorimetric sensing assays of amino acids using gold nanoparticles modified with task-specific ionic liquid

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Datong; Cai, Pengfei; Tao, Zhihao; Pan, Yuanjiang, E-mail: panyuanjiang@zju.edu.cn

    2016-01-01

    In this study, a novel task-specific ionic liquid functionalized gold nanoparticle (TSIL-GNP) was successfully prepared and applied in the recognition of amino acids. Particularly, the surface of GNP was modified with the ionic liquid containing carbamido and ester group via thiol, which was characterized by Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). The stability of this material in aqueous solution improves apparently and can remain unchanged for more than three months. The effect of pH was also discussed in this study. Attractive ionic interaction would effectively weaken intensity of the covalent coupling between the metal ion and the functional groups of amino acids. Thus, TSIL-GNP was successfully applied to recognizing serine, aspartic acid, lysine, arginine, and histidine in the presence of Cu{sup 2+} through distinctive color changes. Suspension would be generated once a spot of cysteine was added into the GNPs solution. Results indicated that it had a good linear relationship between extinction coefficients and concentration of amino acids in a wide range of 10{sup −3}–10{sup −6} M. Moreover, the proposed strategy was successfully used to analyze the histidine in urinary samples. In brief, TSIL-GNP is a suitable substrate for discrimination of five amino acids in a rapid and simple way without sophisticated instruments. - Highlights: • A novel task-specific ionic liquid functionalized gold nanoparticle was successfully prepared. • This material was successfully applied to recognizing five amino acids with Cu(II) through distinctive color changes. • The proposed strategy was successfully used to analyze the histidine in real samples.

  17. Sedimentation in Particulate Aqueous Suspensions as studied by means of Dielectric Time Domain Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Pettersen, Bjoernar Hauknes

    1997-12-31

    Many problems in offshore oil production and multiphase transport are related to surface and colloid chemistry. This thesis applies dielectric spectroscopy as an experimental technique to study the behaviour of particle suspensions in polar media. The thesis opens with an introduction to suspensions and time domain dielectric spectroscopy. It then investigates the dielectric properties of silica and alumina dispersed in polar solvents. It is found that theoretical models can be used to calculate the volume fraction disperse phase in the suspension and that the particle sedimentation depends on the wetting of the particles, charge on the particle surface and viscosity of the solvent, and that this dependency can be measured by time domain dielectric spectroscopy. When the surface properties of silica and alumina particles were modified by coating them with a non-ionic polymer and a non-ionic surfactant, then different degrees of packing in the sedimented phase at the bottom of the sedimentation vessel occurred. Chemometrical methods on the synthesis of monodisperse silica particles were used to investigate what factors influence the particle size. It turned out that it is insufficient to consider only main variables when discussing the results of the synthesis. By introducing interaction terms, the author could explain the variation in the size of particles synthesized. The difference in the sedimentation rate of monodisperse silica particles upon variation of volume fraction particles, pH, salinity, amount of silanol groups at the particle surface and temperature was studied. The cross interactions play an important role and a model explaining the variation in sedimentation is introduced. Finally, magnetic particles dispersed in water and in an external magnetic field were used to study the impact on the sedimentation due to the induced flocculation. 209 refs., 90 figs., 9 tabs.

  18. Infrared spectroscopy of ionic clusters

    Energy Technology Data Exchange (ETDEWEB)

    Price, J.M. (California Univ., Berkeley, CA (USA). Dept. of Chemistry Lawrence Berkeley Lab., CA (USA))

    1990-11-01

    This thesis describes new experiments wherein the infrared vibrational predissociation spectra of a number of mass-selected ionic cluster systems have been obtained and analyzed in the 2600 to 4000 cm{sup {minus}1} region. The species studied include: the hydrated hydronium ions, H{sub 3}O{sup +} (H{sub 2}O){sub 3 {minus}10}, ammoniated ammonium ions, NH{sub 4}{sup +}(NH{sub 3}){sub 1 {minus}10} and cluster ions involving both water and ammonia around an ammonium ion core, (mixed clusters) NH{sub 4}{sup +}(NH{sub 3}){sub n}(H{sub 2}O){sub m} (n+m=4). In each case, the spectra reveal well resolved structures that can be assigned to transitions arising from the vibrational motions of both the ion core of the clusters and the surrounding neutral solvent molecules. 154 refs., 19 figs., 8 tabs.

  19. Stabilization of Heavy Metal Particles in AL2O3-W Suspensions

    Directory of Open Access Journals (Sweden)

    Kędzierska – Sar A.

    2016-09-01

    Full Text Available Ceramic – metal composites are widely used materials in a whole world. There were invented many fabrication methods for those kind of materials, but still exists some problems which need to be fixed. Stability of high density metal particles (e.g. W, Mo, Nb in ceramic-metal composite suspensions is one of crucial issues to be solved in order to obtain homogenous composite material with desired properties such as high fracture toughness, mechanical strength, hardness, wear resistance.

  20. 48 CFR 42.1302 - Suspension of work.

    Science.gov (United States)

    2010-10-01

    ... MANAGEMENT CONTRACT ADMINISTRATION AND AUDIT SERVICES Suspension of Work, Stop-Work Orders, and Government Delay of Work 42.1302 Suspension of work. A suspension of work under a construction or architect... 48 Federal Acquisition Regulations System 1 2010-10-01 2010-10-01 false Suspension of work. 42...

  1. Influence of the ionic strength and solid/solution ratio on Ca(II)-for-Na+ exchange on montmorillonite. Part 2: Understanding the effect of the m/V ratio. Implications for pore water composition and element transport in natural media.

    Science.gov (United States)

    Tertre, E; Ferrage, E; Bihannic, I; Michot, L J; Prêt, D

    2011-11-01

    The aim of the present paper is to clarify previous results showing that selectivity coefficients determined for the exchange of Na(+) for Ca(2+) in montmorillonite were dependent on the solid/solution ratio. The organization of montmorillonite suspensions upon Na(+)/Ca(II) exchange was analyzed by combining optical microscopy, small-angle X-ray scattering and X-ray diffraction. All samples displayed flocculated characteristics, eliminating the possibility of contrasting accessibility of sorption sites with the solid/solution ratio. Modeling of experimental X-ray diffraction patterns was used to quantify the relative proportions of interlayer Ca(2+) and Na(+) cations along the exchange isotherm. The results further confirmed the influence of the solid/solution ratio on the degree of interlayer Ca(II)-for-Na(+) exchange, and specific selectivity coefficients for interlayer sites were determined. The effect of the solid/solution ratio was finally interpreted by the resulting local changes in the solution chemistry. We demonstrated that by accounting for the Donnan effect, the different data can be interpreted using a single selectivity coefficient. The obtained Kc constant was successfully applied to interpret existing hydrogeochemical data on a natural aquitard. This most likely represents a more constrained and valid approach for the modeling of reactive element transport in natural media than does the poorly defined Kd parameter. Copyright © 2011 Elsevier Inc. All rights reserved.

  2. A Course in Fluid Mechanics of Suspensions.

    Science.gov (United States)

    Davis, Robert H.

    1989-01-01

    Discusses a course focusing on fluid mechanics and physical chemistry of suspensions. Describes the main themes of the lectures and includes a list of course outlines. Possible textbooks and many journal articles are listed. (YP)

  3. Heat and mass transfer in particulate suspensions

    CERN Document Server

    Michaelides, Efstathios E (Stathis)

    2013-01-01

    Heat and Mass Transfer in Particulate Suspensions is a critical review of the subject of heat and mass transfer related to particulate Suspensions, which include both fluid-particles and fluid-droplet Suspensions. Fundamentals, recent advances and industrial applications are examined. The subject of particulate heat and mass transfer is currently driven by two significant applications: energy transformations –primarily combustion – and heat transfer equipment. The first includes particle and droplet combustion processes in engineering Suspensions as diverse as the Fluidized Bed Reactors (FBR’s) and Internal Combustion Engines (ICE’s). On the heat transfer side, cooling with nanofluids, which include nanoparticles, has attracted a great deal of attention in the last decade both from the fundamental and the applied side and has produced several scientific publications. A monograph that combines the fundamentals of heat transfer with particulates as well as the modern applications of the subject would be...

  4. Numerical Study of Suspension Plasma Spraying

    CERN Document Server

    Farrokhpanah, Amirsaman; Mostaghimi, Javad

    2016-01-01

    A numerical study of suspension plasma spraying (SPS) is presented in the current work. The liquid suspension jet is replaced with a train of droplets containing the suspension particles injected into the plasma flow. Atomization, evaporation, and melting of different components are considered for particles as they travel towards the substrate. Effect of different parameters on particle conditions during flight and upon impact on the substrate are investigated. Initially, influence of the torch operating conditions such as inlet flow rate and power are studied. Additionally, effect of injector parameters like injection location, flow rate, and angle are examined. The model used in current study takes high temperature gradients and non-continuum effects into account. Moreover, the important effect of change in physical properties of suspension droplets as a result of evaporation is included in the model. These mainly include variations in heat transfer properties and viscosity. Utilizing this improved model, s...

  5. Suspension of rigid spheres in shear flows

    Science.gov (United States)

    Rahmani, Mona; Esteghamatian, Amir; Wachs, Anthony

    2017-11-01

    Suspension of rigid spheres in a plane Couette flow is studied using three-dimensional particle resolved numerical simulations. We use a fixed mesh that resolves each particle diameter using 24 points and a Distributed Lagrange Multi- plier/Fictitious Domain (DLM/FD) method. The effects of particle volume fraction and particle Reynolds number on the macrcoscopic and microscopic stresses in the suspension are examined. The kinematics of particle are also studied for a range of dilute to dense suspensions and Stokes to inertial flows. For dense suspensions and also for higher particle Reynolds numbers the particle/particle and particle/wall contacts are enhanced. For such cases, lubrication forces need to be taken into account. We compare simulations with and without the lubrication forces to conclude for what range of parameters lubrication should be incorporated into the simulations.

  6. Experimental Evaluation of Mountain Bike Suspension Systems

    Directory of Open Access Journals (Sweden)

    J. Titlestad

    2003-01-01

    Full Text Available A significant distinction between competitive mountain bikes is whether they have a suspension system. Research studies indicate that a suspension system gives advantages, but it is difficult to quantify the benefits because they depend on so many variables, including the physiology and psychology of the cyclist, the roughness of the track and the design of the suspension system. A laboratory based test rig has been built that allows the number of variables in the system to be reduced and test conditions to be controlled. The test rig simulates regular impacts of the rear wheel with bumps in a rolling road. The physiological variables of oxygen consumption and heart rate were measured, together with speeds and forces at various points in the system. Physiological and mechanical test results both confirm a significant benefit in using a suspension system on the simulated rough track, with oxygen consumption reduced by around 30 % and power transmitted through the pedals reduced by 30 % to 60 %.

  7. 21 CFR 26.16 - Suspension.

    Science.gov (United States)

    2010-04-01

    ... PHARMACEUTICAL GOOD MANUFACTURING PRACTICE REPORTS, MEDICAL DEVICE QUALITY SYSTEM AUDIT REPORTS, AND CERTAIN... Provisions for Pharmaceutical Good Manufacturing Practices § 26.16 Suspension. (a) Each party has the right...

  8. Optical analysis of red blood cell suspension

    Science.gov (United States)

    Szołna, Alicja A.; Grzegorzewski, Bronisław

    2008-12-01

    The optical properties of suspensions of red blood cells (RBCs) were studied. Fresh human venues blood was obtained from adult healthy donors. RBCs were suspended in isotonic salt solution, and in autologous plasma. Suspensions with haematocrit 0.25 - 3% were investigated. Novel technique was proposed to determine the scattering coefficient μs for the suspensions. The intensity of He-Ne laser light transmitted through a wedge-shape container filled with a suspension was recorded. To find the dependence of the intensity on the thickness of the sample the container was moved horizontally. The dependence of μs on the haematocrit was determined for RBCs suspended in the isotonic salt solution. RBCs suspended in plasma tend to form rouleaux. For the RBCs suspended in plasma, the scattering coefficient as a function of time was obtained. It is shown that this technique can be useful in the study of rouleaux formation.

  9. Aspects of fabrication aluminium matrix heterophase composites by suspension method

    Science.gov (United States)

    Dolata, A. J.; Dyzia, M.

    2012-05-01

    Composites with an aluminium alloy matrix (AlMMC) exhibit several advantageous properties such as good strength, stiffness, low density, resistance and dimensional stability to elevated temperatures, good thermal expansion coefficient and particularly high resistance to friction wear. Therefore such composites are more and more used in modern engineering constructions. Composites reinforced with hard ceramic particles (Al2O3, SiC) are gradually being implemented into production in automotive or aircraft industries. Another application of AlMMC is in the electronics industry, where the dimensional stability and capacity to absorb and remove heat is used in radiators. However the main problems are still: a reduction of production costs, developing methods of composite material tests and final product quality assessment, standardisation, development of recycling and mechanical processing methods. AlMMC production technologies, based on liquid-phase methods, and the shaping of products by casting methods, belong to the cheapest production methods. Application of a suspension method for the production of composites with heterophase reinforcement may turn out to be a new material and technological solution. The article presents the material and technological aspects of the transfer procedures for the production of composite suspensions from laboratory scale to a semi-industrial scale.

  10. Non-Gaussian limit fluctuations in active swimmer suspensions

    Science.gov (United States)

    Kurihara, Takashi; Aridome, Msato; Ayade, Heev; Zaid, Irwin; Mizuno, Daisuke

    2017-03-01

    We investigate the hydrodynamic fluctuations in suspensions of swimming microorganisms (Chlamydomonas) by observing the probe particles dispersed in the media. Short-term fluctuations of probe particles were superdiffusive and displayed heavily tailed non-Gaussian distributions. The analytical theory that explains the observed distribution was derived by summing the power-law-decaying hydrodynamic interactions from spatially distributed field sources (here, swimming microorganisms). The summing procedure, which we refer to as the physical limit operation, is applicable to a variety of physical fluctuations to which the classical central limiting theory does not apply. Extending the analytical formula to compare to experiments in active swimmer suspensions, we show that the non-Gaussian shape of the observed distribution obeys the analytic theory concomitantly with independently determined parameters such as the strength of force generations and the concentration of Chlamydomonas. Time evolution of the distributions collapsed to a single master curve, except for their extreme tails, for which our theory presents a qualitative explanation. Investigations thereof and the complete agreement with theoretical predictions revealed broad applicability of the formula to dispersions of active sources of fluctuations.

  11. Ionic Liquids: Synthesis and Applications in Catalysis

    Directory of Open Access Journals (Sweden)

    Rajni Ratti

    2014-01-01

    Full Text Available Ionic liquids have emerged as an environmentally friendly alternative to the volatile organic solvents. Being designer solvents, they can be modulated to suit the reaction conditions, therefore earning the name “task specific ionic liquids.” Though primarily used as solvents, they are now finding applications in various fields like catalysis, electrochemistry, spectroscopy, and material science to mention a few. The present review is aimed at exploring the applications of ionic liquids in catalysis as acid, base, and organocatalysts and as soluble supports for catalysts.

  12. Core Muscle Activation in Suspension Training Exercises

    OpenAIRE

    Cugliari, Giovanni; Boccia, Gennaro

    2017-01-01

    Abstract A quantitative observational laboratory study was conducted to characterize and classify core training exercises executed in a suspension modality on the base of muscle activation. In a prospective single-group repeated measures design, seventeen active male participants performed four suspension exercises typically associated with core training (roll-out, bodysaw, pike and knee-tuck). Surface electromyographic signals were recorded from lower and upper parts of rectus abdominis, ext...

  13. Rheology of Confined Non-Brownian Suspensions.

    Science.gov (United States)

    Fornari, Walter; Brandt, Luca; Chaudhuri, Pinaki; Lopez, Cyan Umbert; Mitra, Dhrubaditya; Picano, Francesco

    2016-01-08

    We study the rheology of confined suspensions of neutrally buoyant rigid monodisperse spheres in plane-Couette flow using direct numerical simulations. We find that if the width of the channel is a (small) integer multiple of the sphere diameter, the spheres self-organize into two-dimensional layers that slide on each other and the effective viscosity of the suspension is significantly reduced. Each two-dimensional layer is found to be structurally liquidlike but its dynamics is frozen in time.

  14. On the Extraction of Aromatic Compounds from Hydrocarbons by Imidazolium Ionic Liquids

    OpenAIRE

    Jairton Dupont; Chiaro,Sandra S. X.; Bauer Ferrera; Günter Ebeling; Umpierre, Alexandre P.; Cláudia C. Cassol

    2007-01-01

    The liquid-liquid equilibrium for the ternary system formed by n-octane and aromatic (alkylbenzenes) and heteroaromatic compounds (nitrogen and sulfur containing heterocyles) and 1-alkyl-3-methylimidazolium ionic liquids (ILs) associated with various anions has been investigated. The selectivity on the extraction of a specific aromatic compound is influenced by anion volume, hydrogen bond strength between the anion and the imidazolium cation and the length of the 1-methyl-3-alkylimidazolium a...

  15. Melting in temperature sensitive suspensions

    Science.gov (United States)

    Alsayed, Ahmed M.

    We describe two experimental studies about melting in colloidal systems. In particular we studied melting of 1-dimensional lamellar phases and 3-dimensional colloidal crystals. In the first set of experiments we prepared suspensions composed of rodlike fd virus and the thermosensitive polymer, poly(N-isopropylacrylamide). The phase diagram of this systems is temperature and concentration dependent. Using video microscopy, we directly observed melting of lamellar phases and single lamellae into nematic phase. We found that lamellar phases swell with increasing temperature before melting into the nematic phase. The highly swollen lamellae can be superheated as a result of topological nucleation barriers that slow the formation of the nematic phase. In another set of experiments we prepared colloidal crystals from thermally responsive microgel spheres. The crystals are equilibrium close-packed three-dimensional structures. Upon increasing the temperature slightly above room temperature, particle volume fraction decreased from 0.74 to less than 0.5. Using video microscopy, we observed premelting at grain boundaries and dislocations within bulk colloidal crystals. Premelting is the localized loss of crystalline order at surfaces and defects at sample volume fractions above the bulk melting transition. Particle tracking revealed increased disorder in crystalline regions bordering defects, the amount of which depends on the type of defect, distance from the defect, and particle volume fraction. In total these observations suggest that interfacial free energy is the crucial parameter for premelting in colloidal and in atomic scale crystals.

  16. Ride responses of macpherson suspension systems

    Directory of Open Access Journals (Sweden)

    Yu Cheng-Chi

    2017-01-01

    Full Text Available The main purpose of this study is to obtain more correct vehicle ride responses by using a nonlinear ride model considering the effect of Macpherson suspension geometry. Traditional ride model applied to analysis and controller design uses a two degree of freedom linear model, which includes sprung mass and unsprung mass and a spring and a damper vertically connect them. In fact, suspension components do not vertically position above the tire. The motions of body and tire are not going straight up and down. Therefore, the analysis results obtained by the simple model are often different from the experimental values of the actual vehicle. Because of the difference between simple model and actual vehicle, the control strategy almost cannot apply to actual vehicle. In order to understand the effect of suspension geometry on the vehicle ride responses and design a more practical control strategy, a nonlinear model including the geometric parameters of the suspension is constructed in this study. To estimate the initial equilibrium position of the suspension assembly under load, the static equilibrium analysis and mechanism motion analysis are synchronous implemented at the same time. The nonlinear model describes not only the relative position and velocity but also the force transmission between body and tire. Furthermore, by linearize this nonlinear model the development of control strategy for subsequent (semi active suspension system could be expected.

  17. X-ray Mapping of Dynamic Suspensions

    Science.gov (United States)

    Gholami, Mohammad; Lenoir, Nicolas; Ovarlez, Guillaume; Hormozi, Sarah

    2016-11-01

    Dense non-colloidal suspensions are materials with broad application both in industrial processes and natural phenomena. In most of these applications, the suspensions are either far from equilibrium or strongly non-Newtonian (i.e., non-colloidal particles are suspended in non-Newtonian fluid) meaning that the flow kinetics are not only strain-dependent but also strain-rate dependent. Therefore, experimental techniques must be developed to analyze the flows of these complex suspensions over a wide range of steady and transient shear rates. Techniques such as Nuclear Magnetic Resonance/Imaging (NMR/I) are inapplicable due to low sampling frequency and low image resolution (typically 10 minutes per averaged NMR image of 1x1cm). We introduce a new technique using an X-ray/CT-scan system to study dynamic suspensions. We show our recent results on the application of this technique for the study of shear induced migration of particles in a yield stress matrix fluid in a wide-gap cylindrical Couette cell. This work opens new avenues to study dynamic non-colloidal suspensions and the suspensions with other types of nonlinear suspending fluids such as viscoelastic and shear thickening fluids. NFS(CBET-1554044-CAREER).

  18. Core muscle activity during suspension exercises.

    Science.gov (United States)

    Mok, Nicola W; Yeung, Ella W; Cho, Jeran C; Hui, Samson C; Liu, Kimee C; Pang, Coleman H

    2015-03-01

    Suspension exercise has been advocated as an effective means to improve core stability among healthy individuals and those with musculoskeletal complaints. However, the activity of core muscles during suspension exercises has not been reported. In this study, we investigated the level of activation of core muscles during suspension exercises within young and healthy adults. The study was conducted in a controlled laboratory setting. Surface electromyographic (sEMG) activity of core muscles (rectus abdominis, external oblique, internal oblique/transversus abdominis, and superficial lumbar multifidus) during four suspension workouts (hip abduction in plank, hamstring curl, chest press, and 45° row) was investigated. Muscle activity during a 5-s hold period of the workouts was measured by sEMG and normalized to the individual's maximal voluntary isometric contraction (MVIC). Different levels of muscle activation were observed during the hip abduction in plank, hamstring curl, and chest press. Hip abduction in plank generated the highest activation of most abdominal muscles. The 45° row exercise generated the lowest muscle activation. Among the four workouts investigated, the hip abduction in plank with suspension was found to have the strongest potential strengthening effect on core muscles. Also, suspension training was found to generate relatively high levels of core muscle activation when compared with that among previous studies of core exercises on stable and unstable support surfaces. Copyright © 2014 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

  19. Alkaline ionic liquids applied in supported ionic liquid catalyst for selective hydrogenation of citral to citronellal

    Directory of Open Access Journals (Sweden)

    Eero eSalminen

    2014-02-01

    Full Text Available The challenge in preparation of ionic liquids containing a strong alkaline anion is to identify a suitable cation which can tolerate the harsh conditions induced by the anion. In this study, a commercial quaternary ammonium compound (quat benzalkonium [ADBA] (alkyldimethylbenzylammonium was used as a cation in the synthesis of different alkaline ionic liquids. In fact, the precursor, benzalkonium chloride, is a mixture of alkyldimethylbenzylammonium chlorides of various alkyl chain lengths and is commonly used in the formulation of various antiseptic products. The prepared ionic liquids were utilized as Supported Ionic Liquid Catalysts (SILCAs. Typically, a SILCA contains metal nanoparticles, enzymes or metal complexes in an ionic liquid layer which is immobilized on a solid carrier material such as an active carbon cloth (ACC. The catalysts were applied in the selective hydrogenation of citral to citronellal which is an important perfumery chemical. Interestingly, 70 % molar yield towards citronellal was achieved over a catalyst containing the alkaline ionic liquid benzalkonium methoxide.

  20. Alkaline ionic liquids applied in supported ionic liquid catalyst for selective hydrogenation of citral to citronellal

    Science.gov (United States)

    Salminen, Eero; Virtanen, Pasi; Mikkola, Jyri-Pekka

    2014-02-01

    The challenge in preparation of ionic liquids containing a strong alkaline anion is to identify a suitable cation which can tolerate the harsh conditions induced by the anion. In this study, a commercial quaternary ammonium compound (quat) benzalkonium [ADBA] (alkyldimethylbenzylammonium) was used as a cation in the synthesis of different alkaline ionic liquids. In fact, the precursor, benzalkonium chloride, is a mixture of alkyldimethylbenzylammonium chlorides of various alkyl chain lengths and is commonly used in the formulation of various antiseptic products. The prepared ionic liquids were utilized as Supported Ionic Liquid Catalysts (SILCAs). Typically, a SILCA contains metal nanoparticles, enzymes or metal complexes in an ionic liquid layer which is immobilized on a solid carrier material such as an active carbon cloth (ACC). The catalysts were applied in the selective hydrogenation of citral to citronellal which is an important perfumery chemical. Interestingly, 70 % molar yield towards citronellal was achieved over a catalyst containing the alkaline ionic liquid benzalkonium methoxide.